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Virtual reality (VR) locomotion should allow users to move freely in the virtual space while staying within the tracking area in the real space. The redirected walking (RDW) technique enables users to walk naturally in an unlimited virtual space within a limited tracking area by rotating the virtual scene view. However, conflicting visual and vestibular signals during RDW can lead to user discomfort and decreased immersion. To avoid user discomfort, an RDW gain should be within the detection threshold (DT) range. However, a large angle of walking redirection is required when physically avoiding obstacles or escaping from a narrow space, so DT expansion is necessary. In this study, to change the curvature DT range and enhance RDW performance, we proposed an optical flow (OF)-generating vection in a virtual environment. Further, we investigate methods to reduce user discomfort and increase RDW efficiency considering familiar and unfamiliar VR users. The findings showed that the introduction of OF led to a reduction in the DT range for all users, irrespective of the OF’s direction. However, conditions with OF resulted in an extended DT range for users familiar with VR while concurrently diminishing the DT range for those who were VR unfamiliar. To delve further, our analysis indicated that when both the OF and redirecting directions were identical, the RDW performance was robust to VR familiarity, whereas in opposing directions, the DT range increased for VR-familiar users. Our study findings suggested using OF for the RDW technique and extending its applicability in virtual environments. [ABSTRACT FROM AUTHOR]

• Built an apparatus to study non-condensable gas interactions with refrigerant. • Two non-condensable gas fault intensities were imposed at various test conditions. • Ideal Gas assumption causes theory to overestimate non-condensable gas. • A new model quantifies non-condensable gas in typical residential air-conditioners. Non-condensable gas (NC) can be introduced into a vapor compression refrigeration cycle through improper installation or service, and decrease system efficiency, increase burden on the compressor, and reduce the compressor life span. Therefore, detecting this fault early can prevent energy waste and prolong the operating life of the system. However, diagnostic methods are not widely available, and neither are methods to quantify NC amounts based on easily measured variables. Therefore, an experimental test apparatus was built to provide data to improve understanding of NC-refrigerant interactions. Two NC fault intensities (50%, 100%), each at four charge levels (70%, 80%, 100%, 120%), were tested under five different ambient temperatures (0-40°C). Dry nitrogen gas was used for the NC. The results showed that the theoretical estimation method is inaccurate. The trends of the results from experimental tests are consistent with those from theoretical calculations, but the thresholds obtained from experimental tests are larger than those from theoretical calculations. This paper explains these differences, and provides a model to quantify the NC fault intensity using easily-measured variables. The specific model is applicable to typical residential air-conditioner and heat pump systems that use R410A refrigerant, but the general findings are applicable to other refrigerants. [ABSTRACT FROM AUTHOR]

Every-day acoustical environments are often complex, typically comprising one attended target sound in the presence of interfering sounds (e.g., disturbing conversations) and reverberation. Here we assessed binaural detection thresholds and (supra-threshold) binaural audio quality ratings of four distortions types: spectral ripples, non-linear saturation, intensity and spatial modifications applied to speech, guitar, and noise targets in such complex acoustic environments (CAEs). The target and (up to) two masker sounds were either co-located as if contained in a common audio stream, or were spatially separated as if originating from different sound sources. The amount of reverberation was systematically varied. Masker and reverberation had a significant effect on the distortion-detection thresholds of speech signals. Quality ratings were affected by reverberation, whereas the effect of maskers depended on the distortion. The results suggest that detection thresholds and quality ratings for distorted speech in anechoic conditions are also valid for rooms with mild reverberation, but not for moderate reverberation. Furthermore, for spectral ripples, a significant relationship between the listeners' individual detection thresholds and quality ratings was found. The current results provide baseline data for detection thresholds and audio quality ratings of different distortions of a target sound in CAEs, supporting the future development of binaural auditory models. [ABSTRACT FROM AUTHOR]

Every-day acoustical environments are often complex, typically comprising one attended target sound in the presence of interfering sounds (e.g., disturbing conversations) and reverberation. Here we assessed binaural detection thresholds and (supra-threshold) binaural audio quality ratings of four distortions types: spectral ripples, non-linear saturation, intensity and spatial modifications applied to speech, guitar, and noise targets in such complex acoustic environments (CAEs). The target and (up to) two masker sounds were either co-located as if contained in a common audio stream, or were spatially separated as if originating from different sound sources. The amount of reverberation was systematically varied. Masker and reverberation had a significant effect on the distortion-detection thresholds of speech signals. Quality ratings were affected by reverberation, whereas the effect of maskers depended on the distortion. The results suggest that detection thresholds and quality ratings for distorted speech in anechoic conditions are also valid for rooms with mild reverberation, but not for moderate reverberation. Furthermore, for spectral ripples, a significant relationship between the listeners’ individual detection thresholds and quality ratings was found. The current results provide baseline data for detection thresholds and audio quality ratings of different distortions of a target sound in CAEs, supporting the future development of binaural auditory models.

Intracortical microstimulation (ICMS) has shown promise in restoring quality of life to patients suffering from paralysis, specifically when used in the primary somatosensory cortex (S1). However, these benefits can be hampered by long-term degradation of electrode performance due to the brain's foreign body response. Advances in microfabrication techniques have allowed for the development of neuroprostheses with subcellular electrodes, which are characterized by greater versatility and a less detrimental immune response during chronic use. These probes are hypothesized to enable more selective, higher-resolution stimulation of cortical tissue with long-term implants. However, microstimulation using physiologically relevant charges with these smaller-scale devices can damage electrode sites and reduce the efficacy of the overall device. Studies have shown promise in bypassing this limitation by spreading the stimulation charge between multiple channels in an implanted electrode array, but to our knowledge the usefulness of this strategy in laminar arrays with electrode sites spanning each layer of the cortex remains unexplored. To investigate the efficacy of simultaneous multi-channel ICMS in electrode arrays with stimulation sites spanning cortical depth, we implanted laminar electrode arrays in the primary somatosensory cortex of rats trained in a behavioral avoidance paradigm. By measuring detection thresholds, we were able to quantify improvements in ICMS performance using a simultaneous multi-channel stimulation paradigm. The charge required per site to elicit detection thresholds was halved when stimulating from two adjacent electrode sites, although the overall charge used by the implant was increased. This reduction in threshold charge was more pronounced when stimulating with more than two channels and lessened with greater distance between stimulating channels. Our findings suggest that these improvements are based on the synchronicity and polarity of each stimulus, leading us to conclude that these improvements in stimulation efficiency per electrode are due to charge summation as opposed to a summation of neural responses to stimulation. Additionally, the per-site charge reductions are seen regardless of the cortical depth of each utilized channel. This evocation of physiological detection thresholds with lower stimulation currents per electrode site has implications for the feasibility of stimulation regimes in future advanced neuroprosthetic devices, which could benefit from reducing the charge output per site. [ABSTRACT FROM AUTHOR]

Intracortical microstimulation (ICMS) has shown promise in restoring quality of life to patients suffering from paralysis, specifically when used in the primary somatosensory cortex (S1). However, these benefits can be hampered by long-term degradation of electrode performance due to the brain’s foreign body response. Advances in microfabrication techniques have allowed for the development of neuroprostheses with subcellular electrodes, which are characterized by greater versatility and a less detrimental immune response during chronic use. These probes are hypothesized to enable more selective, higher-resolution stimulation of cortical tissue with long-term implants. However, microstimulation using physiologically relevant charges with these smaller-scale devices can damage electrode sites and reduce the efficacy of the overall device. Studies have shown promise in bypassing this limitation by spreading the stimulation charge between multiple channels in an implanted electrode array, but to our knowledge the usefulness of this strategy in laminar arrays with electrode sites spanning each layer of the cortex remains unexplored. To investigate the efficacy of simultaneous multi-channel ICMS in electrode arrays with stimulation sites spanning cortical depth, we implanted laminar electrode arrays in the primary somatosensory cortex of rats trained in a behavioral avoidance paradigm. By measuring detection thresholds, we were able to quantify improvements in ICMS performance using a simultaneous multi-channel stimulation paradigm. The charge required per site to elicit detection thresholds was halved when stimulating from two adjacent electrode sites, although the overall charge used by the implant was increased. This reduction in threshold charge was more pronounced when stimulating with more than two channels and lessened with greater distance between stimulating channels. Our findings suggest that these improvements are based on the synchronicity and polarity of each stimulus, leading us to conclude that these improvements in stimulation efficiency per electrode are due to charge summation as opposed to a summation of neural responses to stimulation. Additionally, the per-site charge reductions are seen regardless of the cortical depth of each utilized channel. This evocation of physiological detection thresholds with lower stimulation currents per electrode site has implications for the feasibility of stimulation regimes in future advanced neuroprosthetic devices, which could benefit from reducing the charge output per site.

[Display omitted] • We measured thresholds for monocular, interocular in-phase and interocular anti-phase tests, with interocular in-phase and anti-phase surrounds. • We observed binocular summation for anti-phase tests suggesting the existence of a differencing channel. • Binocular summation is enhanced by surround masks with opposite interocular phase relationships to those of the tests. • A new model that incorporates both an additive and a differencing channel gives a good account of the data. Recent studies suggest that binocular adding S + and differencing S - channels play an important role in binocular vision. To test for such a role in the context of binocular contrast detection and binocular summation, we employed a surround masking paradigm consisting of a central target disk surrounded by a mask annulus. All stimuli were horizontally oriented 0.5c/d sinusoidal gratings. Correlated stimuli were identical in interocular spatial phase while anticorrelated stimuli were opposite in interocular spatial phase. There were four target conditions: monocular left eye, monocular right eye, binocular correlated and binocular anticorrelated, and three surround mask conditions: no surround, binocularly correlated and binocularly anticorrelated. We observed consistent elevation of detection thresholds for monocular and binocular targets across the two binocular surround mask conditions. In addition, we found an interaction between the type of surround and the type of binocular target: both detection and summation were relatively enhanced by surround masks and targets with opposite interocular phase relationships and reduced by surround masks and targets with the same interocular phase relationships. The data were reasonably well accounted for by a model of binocular combination termed MAX (S+S-), in which the decision variable is the probability summation of modeled S + and S - channel responses, with a free parameter determining the relative gains of the two channels. Our results support the existence of two channels involved in binocular combination, S + and S -, whose relative gains are adjustable by surround context. [ABSTRACT FROM AUTHOR]

Virtual Reality (VR) systems increase immersion by reproducing users' movements in the real world. However, several works have shown that this real-to-virtual mapping does not need to be precise in order to convey a realistic experience. Being able to alter this mapping has many potential applications, since achieving an accurate real-to-virtual mapping is not always possible due to limitations in the capture or display hardware, or in the physical space available. In this work, we measure detection thresholds for lateral translation gains of virtual camera motion in response to the corresponding head motion under natural viewing, and in the absence of locomotion, so that virtual camera movement can be either compressed or expanded while these manipulations remain undetected. Finally, we propose three applications for our method, addressing three key problems in VR: improving 6-DoF viewing for captured 360° footage, overcoming physical constraints, and reducing simulator sickness. We have further validated our thresholds and evaluated our applications by means of additional user studies confirming that our manipulations remain imperceptible, and showing that (i) compressing virtual camera motion reduces visible artifacts in 6-DoF, hence improving perceived quality, (ii) virtual expansion allows for completion of virtual tasks within a reduced physical space, and (iii) simulator sickness may be alleviated in simple scenarios when our compression method is applied. [ABSTRACT FROM AUTHOR]

Modulation of the frictional force of a fingertip sliding over a surface-haptic device can produce compelling sensations of texture and relief. The virtual sensation is particularly apparent and feel as fixed in space if the stimulus is rigorously correlated with the displacement of the finger. While frictional textures tactually resemble their real counterparts, some exploratory conditions under which the sharpness of the texture declines exist. We postulate that this decline in sharpness is caused by the perceptual limitation of the attempt to interpret the variation in friction as an out-of-plane sinusoidal topography. To investigate these questions, we measured the detection thresholds of sinusoidal friction-modulated gratings for a wide range of spatial periods explored at two different speeds. We compared the results with the detection thresholds, reported in the literature, of real gratings and vibrotactile stimuli. We found that the detection of spatial friction-modulated textures does not follow the same trend as that of real textures but is more similar to the vibrotactile rendering, which is strongly influenced by the exploratory speed. This article provides a better understanding of the perception of friction-modulated textures and provides insight into how to design impactful stimuli on surface-haptic devices. [ABSTRACT FROM AUTHOR]

Ground vibration recorded using geophones can provide information on debris flows. This information can be used for debris flow detection and warning. However, real debris flow signals change not only from site to site but also during different times at the same location. Thus, a constant threshold calibrated with historic data at one location may not accurately detect debris flow at the same location, let alone at other locations. Therefore, a debris flow detection method requires a criterion that can transform current environmental conditions into a detection criterion. The characteristic of a debris flow tremor was discussed and transformed into two mathematical indices. We used accumulation energy and the rate of energy change in a specific spectrum domain as the representative indicators. To distinguish debris flows from noise, we assumed debris flow energy to be at least an order of magnitude larger than noise before debris flow arrival. To avoid a short-term spike event confusing the detection of debris flow, accumulation energy at an interval longer than 2 s was used. This method was tested on three debris flow events with complete records at the Ai-Yu-Zi Creek, Taiwan. The detection of arrival time for debris flows using geophone data had a delay of less than 10 s compared with the detection of arrival time through video recording. [ABSTRACT FROM AUTHOR]

Redirected walking techniques enable users to naturally locomote in virtual environments (VEs) that are larger than the tracked space. Redirected walking imperceptibly transforms the VE around the user with predefined estimated threshold gains. Previously estimated gains were evaluated with a 40° field of view (FOV), and have not been evaluated in the presence of a distractor—a moving object in the VE that may capture the user's attention. We conducted a 2 (FOV: 40°, 110°) × 2 (Gender: female, male) × 2 (Distractor: without, with) user study to estimate and compare thresholds for rotation gains. Significant differences in detection thresholds were found between FOVs, and significant differences were found between female and male gains with a 110° FOV. Males had significantly wider gains using a 110° FOV compared to a 40° FOV, and distractors affected females differently than males. Finally, strong correlations were found between simulator sickness scores and threshold gains. [ABSTRACT FROM AUTHOR]

Humans require precise force control to execute fine manual tasks, which is generally facilitated to a great extent by providing adequate feedback. Currently, such dexterous manual tasks can be an input source of computing. To design appropriate vibrotactile stimuli for manual tasks, it is essential to quantify human vibrotactile sensitivity over a large range of contact forces. In this paper, we report the psychophysical detection thresholds for vibrotactile stimuli measured for five pressing forces that cover the range of forces encountered during ordinary manual tasks. The experimental results showed stark contrasts between stimulus frequencies, depending on actively exerted pressing force. The detection thresholds for 40 Hz stimuli first increased and then decreased as the pressing force increased, but the detection threshold for 250 Hz stimuli generally decreased as the force increased. These results have immediate consequences on the design of vibrotactile feedback for manual tasks in many applications of tangible interaction, tele-operation, and VR. [ABSTRACT FROM AUTHOR]

Thresholds of asymmetric pulses presented to cochlear implant (CI) listeners depend on polarity in a way that differs across subjects and electrodes. It has been suggested that lower thresholds for cathodic-dominant compared to anodic-dominant pulses reflect good local neural health. We evaluated the hypothesis that this polarity effect (PE) can be used in a site-selection strategy to improve speech perception and spectro-temporal resolution. Detection thresholds were measured in eight users of Advanced Bionics CIs for 80-pps, triphasic, monopolar pulse trains where the central high-amplitude phase was either anodic or cathodic. Two experimental MAPs were then generated for each subject by deactivating the five electrodes with either the highest or the lowest PE magnitudes (cathodic minus anodic threshold). Performance with the two experimental MAPs was evaluated using two spectro-temporal tests (Spectro-Temporal Ripple for Investigating Processor EffectivenesS (STRIPES; Archer-Boyd et al. in J Acoust Soc Am 144:2983-2997, 2018) and Spectral-Temporally Modulated Ripple Test (SMRT; Aronoff and Landsberger in J Acoust Soc Am 134:EL217-EL222, 2013)) and with speech recognition in quiet and in noise. Performance was also measured with an experimental MAP that used all electrodes, similar to the subjects' clinical MAP. The PE varied strongly across subjects and electrodes, with substantial magnitudes relative to the electrical dynamic range. There were no significant differences in performance between the three MAPs at group level, but there were significant effects at subject level-not all of which were in the hypothesized direction-consistent with previous reports of a large variability in CI users' performance and in the potential benefit of site-selection strategies. The STRIPES but not the SMRT test successfully predicted which strategy produced the best speech-in-noise performance on a subject-by-subject basis. The average PE across electrodes correlated significantly with subject age, duration of deafness, and speech perception scores, consistent with a relationship between PE and neural health. These findings motivate further investigations into site-specific measures of neural health and their application to CI processing strategies. [ABSTRACT FROM AUTHOR]

Previous psychophysical and modeling studies suggest that cathodic stimulation by a cochlear implant (CI) may preferentially activate the peripheral processes of the auditory nerve, whereas anodic stimulation may preferentially activate the central axons. Because neural degeneration typically starts with loss of the peripheral processes, lower thresholds for cathodic than for anodic stimulation may indicate good local neural survival. We measured thresholds for 99-pulse-per-second trains of triphasic (TP) pulses where the central high-amplitude phase was either anodic (TP-A) or cathodic (TP-C). Thresholds were obtained in monopolar mode from four or five electrodes and a total of eight ears from subjects implanted with the Advanced Bionics CI. When between-subject differences were removed, there was a modest but significant correlation between the polarity effect (TP-C threshold minus TP-A threshold) and the average of TP-C and TP-A thresholds, consistent with the hypothesis that a large polarity effect corresponds to good neural survival. When data were averaged across electrodes for each subject, relatively low thresholds for TP-C correlated with a high "upper limit" (the pulse rate up to which pitch continues to increase) from a previous study (Cosentino et al. J Assoc Otolaryngol 17:371-382). Overall, the results provide modest indirect support for the hypothesis that the polarity effect provides an estimate of local neural survival. [ABSTRACT FROM AUTHOR]

Previous psychophysical studies have shown that a steep detection-threshold-versus-stimulation-rate function (multipulse integration; MPI) is associated with laterally positioned electrodes producing a broad neural excitation pattern. These findings are consistent with steep MPI depending on either a certain width of neural excitation allowing a large population of neurons operating at a low point on their dynamic range to respond to an increase in stimulation rate or a certain slope of excitation pattern that allows recruitment of neurons at the excitation periphery. Results of the current study provide additional support for these mechanisms by demonstrating significantly flattened MPI functions in narrow bipolar than monopolar stimulation. The study further examined the relationship between the steepness of the psychometric functions for detection (d' versus log current level) and MPI. In contrast to findings in monopolar stimulation, current data measured in bipolar stimulation suggest that steepness of the psychometric functions explained a moderate amount of the across-site variance in MPI. Steepness of the psychometric functions, however, cannot explain why MPI flattened in bipolar stimulation, since slopes of the psychometric functions were comparable in the two stimulation modes. Lastly, our results show that across-site mean MPI measured in monopolar and bipolar stimulation correlated with speech recognition in opposite signs, with steeper monopolar MPI being associated with poorer performance but steeper bipolar MPI being associated with better performance. If steeper MPI requires broad stimulation of the cochlea, the correlation between monopolar MPI and speech recognition can be interpreted as the detrimental effect of poor spectral resolution on speech recognition. Assuming bipolar stimulation produces narrow excitation, and MPI measured in bipolar stimulation reflects primarily responses of the on-site neurons, the correlation between bipolar MPI and speech recognition can be understood in light of the importance of neural survival for speech recognition. [ABSTRACT FROM AUTHOR]

Knowledge of the mass composition of cosmic rays in the transition region of galactic to extragalactic cosmic rays is needed to discriminate different astrophysical models on their origin, acceleration, and propagation. An important observable to separate different mass groups of cosmic rays is the number of muons in extensive air showers. We performed a CORSIKA simulation study to analyze the impact of the detection threshold of muons on the separation quality of different primary cosmic rays in the energy region of the ankle. Using only the number of muons as the composition-sensitive observable, we find a clear dependence of the separation power on the detection threshold for ideal measurements. Although the number of detected muons increases when lowering the threshold, the discrimination power is reduced. If statistical fluctuations for muon detectors of limited size are taken into account, the threshold dependence remains qualitatively the same for small distances to the shower core but is reduced for large core distances. We interpret the impact of the detection threshold of muons on the composition sensitivity in terms of a change of the correlation of the number of muons n μ with the shower maximum X max  as function of the muon energy as a result of the underlying hadronic interactions and the shower geometry. We further investigate the role of muons produced in a shower by photon-air interactions and conclude that, in addition to the effect of the n μ − X max correlation, the separability of primaries is reduced as a consequence of the presence of more muons from photonuclear reactions in proton than in iron showers. [ABSTRACT FROM AUTHOR]

Background: Recent studies have proposed that humans may perceive complex carbohydrates and that sensitivity to simple carbohydrates is independent of sensitivity to complex carbohydrates. Variation in oral complex carbohydrate sensitivity may influence food consumption.Objective: This study aimed to investigate the associations between oral complex carbohydrate sensitivity, anthropometry, and dietary intake in adults.Methods: We assessed oral sensitivity to complex carbohydrates (maltodextrin and oligofructose) by measuring detection thresholds (DTs) and suprathreshold intensity perceptions (STs) for 34 participants, including 16 men (mean ± SEM age : 26.2 ± 0.4 y; range: 24-30 y) and 18 women (age: 29.4 ± 2.1 y; range: 24-55 y). We also measured height, weight, and waist circumference (WC) and participants completed a 4-d food diary and a food-frequency questionnaire.Results: Measurements of oral sensitivity to complex carbohydrates were significantly correlated with WC and dietary energy and starch intakes (DT: r = -0.38, P < 0.05; ST: r = 0.36-0.48, P < 0.05). When participants were grouped into tertiles, there were significant differences in WC and total energy or starch intakes for those who were more sensitive or experienced high intensity compared with those who were less sensitive or experienced low intensity. Being more sensitive or experiencing high intensity was associated with greater energy (7968-8954 kJ/d) and starch (29.1-29.8% of energy) intakes and a greater WC (88.2-91.4 cm) than was being less sensitive or experiencing low intensity (6693-7747 kJ/d, 20.9-22.2% of energy, and 75.5-80.5 cm, respectively).Conclusion: Complex carbohydrate sensing is associated with WC and consumption of complex carbohydrates and energy in adults. This trial was registered at anzctr.org.au as ACTRN12616001356459. [ABSTRACT FROM AUTHOR]

The reduced gravity experienced in lunar or Martian surfaces can be simulated on the earth using a cable-driven system, where the cable lifts a person to reduce his or her weight. This paper presents a novel cable-driven system designed for the purpose. It is integrated with a head-mounted display and a motion capture system. Focusing on jump motion within the system, this paper proposes to scale the jump and reports the experiments made for quantifying the extent to which a jump can be scaled without the discrepancy between physical and virtual jumps being noticed by the user. With the tolerable range of scaling computed from these experiments, an application named retargeted jump is developed, where a user can jump up onto virtual objects while physically jumping in the real-world flat floor. The core techniques presented in this paper can be extended to develop extreme-sport simulators such as parasailing and skydiving. [ABSTRACT FROM PUBLISHER]

Sweetness is one of the 5 prototypical tastes and is activated by sugars and non-nutritive sweeteners (NNS). The aim of this study was to investigate measures of sweet taste function [detection threshold (DT), recognition threshold (RT), and suprathreshold intensity ratings] across multiple sweeteners. Sixty participants, 18-52 years of age (mean age in years = 26, SD = ±7.8), were recruited to participate in the study. DT and RT were collected for caloric sweeteners (glucose, fructose, sucrose, erythritol) and NNS (sucralose, rebaudioside A). Sweetness intensity for all sweeteners was measured using a general Labeled Magnitude Scale. There were strong correlations between DT and RT of all 4 caloric sweeteners across people (r = 0.62-0.90, P < 0.001), and moderate correlations between DT and RT for both of the NNS (r = 0.39-0.48, P < 0.05); however, weaker correlations were observed between the DT or RT of the caloric sweeteners and NNS (r = 0.26-0.48, P < 0.05). The DT and RT of glucose and fructose were not correlated with DT or RT of sucralose (P > 0.05). In contrast, there were strong correlations between the sweetness intensity ratings of all sweeteners (r = 0.70-0.96, P < 0.001). This suggests those caloric sweeteners and NNS access at least partially independent mechanisms with respect to DT and RT measures. At suprathreshold level, however, the strong correlation between caloric sweeteners and NNS through weak, moderate, and strong intensity indicates a commonality in sweet taste mechanism for the perceived intensity range. [ABSTRACT FROM AUTHOR]

Detection of a tactile stimulus on one finger is impaired when a concurrent stimulus (masker) is presented on an additional finger of the same or the opposite hand. This phenomenon is known to be finger-specific at the within-hand level. However, whether this specificity is also maintained at the between-hand level is not known. In four experiments, we addressed this issue by combining a Bayesian adaptive staircase procedure (QUEST) with a two-interval forced choice (2IFC) design in order to establish threshold for detecting 200ms, 100Hz sinusoidal vibrations applied to the index or little fingertip of either hand (targets). We systematically varied the masker finger (index, middle, ring, or little finger of either hand), while controlling the spatial location of the target and masker stimuli. Detection thresholds varied consistently as a function of the masker finger when the latter was on the same hand (Experiments 1 and 2), but not when on different hands (Experiments 3 and 4). Within the hand, detection thresholds increased for masker fingers closest to the target finger (i.e., middle>ring when the target was index). Between the hands, detection thresholds were higher only when the masker was present on any finger as compared to when the target was presented in isolation. The within hand effect of masker finger is consistent with the segregation of different fingers at the early stages of somatosensory processing, from the periphery to the primary somatosensory cortex (SI). We propose that detection is finger-specific and reflects the organisation of somatosensory receptive fields in SI within, but not between the hands.

Virtual reality strives to provide a user with an experience of a simulated world that feels as natural as the real world. Yet, to induce this feeling, sometimes it becomes necessary for technical reasons to deviate from a one-to-one correspondence between the real and the virtual world, and to reorient or reposition the user's viewpoint. Ideally, users should not notice the change of the viewpoint to avoid breaks in perceptual continuity. Saccades, the fast eye movements that we make in order to switch gaze from one object to another, produce a visual discontinuity on the retina, but this is not perceived because the visual system suppresses perception during saccades. As a consequence, our perception fails to detect rotations of the visual scene during saccades. We investigated whether saccadic suppression of image displacement (SSID) can be used in an immersive virtual environment (VE) to unconsciously rotate and translate the observer's viewpoint. To do this, the scene changes have to be precisely time-locked to the saccade onset. We used electrooculography (EOG) for eye movement tracking and assessed the performance of two modified eye movement classification algorithms for the challenging task of online saccade detection that is fast enough for SSID. We investigated the sensitivity of participants to translations (forward/backward) and rotations (in the transverse plane) during trans-saccadic scene changes. We found that participants were unable to detect approximately ±0.5m translations along the line of gaze and ±5° rotations in the transverse plane during saccades with an amplitude of 15°. If the user stands still, our approach exploiting SSID thus provides the means to unconsciously change the user's virtual position and/or orientation. For future research and applications, exploiting SSID has the potential to improve existing redirected walking and change blindness techniques for unlimited navigation through arbitrarily-sized VEs by real walking. [ABSTRACT FROM AUTHOR]

A valid, objective computation of whether a real-world sound is detectable in a real-world acoustical environment is highly desirable in many noise control applications. However, most current prediction approaches have not been validated for this purpose and have not been tailored towards predicting the influence of certain signal features, such as the temporal structure or the spectral content of the masker or target. In order to evaluate the applicability of prediction approaches with respect to these signal features, detection thresholds of various real-world signals were measured for normal-hearing listeners. The detection thresholds depended on the temporal structure and spectrum of the target and the spectrum of the masker. The data were compared to predictions of five approaches ranging from time-averaged technical measures to psychoacoustic models, which incorporate these signal features to different extents. In general, the correspondence between predictions and the experimental data was better for the psychoacoustic models than for the results of the technical measures. Even though all models could account for most of the key effects in the experimental data, only the psychoacoustic models were able to predict the influence of the temporal structure of the signals. One of the models showed clear advantages in prediction performance, reaching an overall determination coefficient of R 2 = 0.94. This underlines the applicability of psychoacoustic models for correctly predicting audibility in real-world applications. [ABSTRACT FROM AUTHOR]

Due to the longer PRN code employed in next-generation GNSS (Global Navigation Satellite System), receivers in the signal acquisition process should test a larger number of code phase hypotheses. Recently, to reduce acquisition time and computational complexity, TDCC (Two-dimensional Compressed Correlator) is introduced, and this technique is different from the conventional double dwell search technique in terms of parameters used to reduce acquisition time and computational complexity. Studies for optimizing the performance of TDCC have not been introduced yet, therefore, in this paper, detection thresholds of TDCC are investigated to optimize its acquisition performance. The optimal detection thresholds minimizing the MAT (Mean Acquisition Time) and MAC (Mean Acquisition Computation) are numerically evaluated and analyzed for widely used detection strategies in its serial and parallel search schemes. It is demonstrated that the minimized MAT and MAC are much smaller than the MAT and MAC using a detection threshold based on CFAR (Constant False Alarm Rate). [ABSTRACT FROM PUBLISHER]

Taste is the chemical sensation whose function is not very well known. Recently it was shown that the range of taste is more extensive than the five basic taste sweet, salty, bitter, sour and umami. A metallic taste has been suggested as another basic taste, but its mode of perception is not well understood and has not been really accepted in the taste literature. Ferrous sulphate solutions were presented to the assessors so their sensitivity and best estimate thresholds (BET) were measured. The best estimated threshold range was 0.00049-0.00669 g/l for demineralised water, 0.00079-0.00669 g/l for distilled water and 0.00108-0.00669 g/l for tap water.

Abstract: The impact of taste acuity on consumer acceptability and food selection responses has been studied for some time, particularly in the case of bitterness. Less attention has been given to the impact of odor acuity on such responses. To begin to bridge this gap, this investigation is focused on cis-3-hexen-1-ol (green/grassy) and the questions explored were: (1) does varying sensitivity to the odor of cis-3-hexen-1-ol impact hedonic responses to food stimuli that have been spiked with this odorant? and (2) does varying sensitivity to the odor of cis-3-hexen-1-ol impact self-reported food selection? The results from three studies involving 400+ consumers are reported. They are: (1) confirm that in the case of cis-3-hexen-1-ol, odor acuity has a small but systematic impact on acceptability and (2) suggest that this result could extend to food selection. Hedonic responses to hummus, tomato juice and Japanese green tea spiked with two different concentrations of cis-3-hexen-1-ol were negative (relative to the unspiked samples) and these response patterns were similar in consumers of Caucasian and Japanese ancestry. Compared to participants classified as ‘sensitive’ to the odor of cis-3-hexen-1-ol, the negative responses to the spiked foods were less strong among ‘insensitive’ participants. Similar response patterns emerged when Caucasian consumers hedonically assessed the odor of gold kiwifruit essence spiked with cis-3-hexen-1-ol: increasing spike concentration was perceived negatively, but the magnitude of the negative responses was less among participants classified as ‘insensitive’ to the odor of cis-3-hexen-1-ol. Preferences for the odor of gold kiwifruit essence spiked with cis-3-hexen-1-ol varied among ‘sensitive’ and ‘insensitive’ participants, and revealed a preference among ‘insensitive’ participants for intermediate spike concentrations relative to high and low spike concentrations. The impact on food selection was studied using a 142-item 24h self-completion food recall questionnaire, where participants indicated whether or not they had consumed each of the focal foods/beverages. Participants provided data for at least seven 24h recall periods (18 periods on average) and the proportion of days where items were consumed was compared. Amid considerable individual variation in dietary patterns, a tendency towards participants classified as ‘sensitive’ to the odor of cis-3-hexen-1-ol to more frequently consume mild cheese, salad greens and cucumber was uncovered. This result should be considered tentative and more as a suggestion for future targeted research into the impact of sensitivity to the odor of cis-3-hexen-1-ol on food selection. [Copyright &y& Elsevier]

The use of quantitative sensory testing (QST) has become more widespread, with increasing focus on describing somatosensory profiles and pain mechanisms. However, the reliability of thermal QST has yet to be established. We systematically searched the literature using key medical databases. Independent reviewers evaluated reliability data using the Quality Appraisal for Reliability Studies checklist. Of the 21 studies we included in this review, we deemed 5 to have high methodological quality. Narrative analysis revealed that estimates of reliability varied considerably, but overall, the reliability of cold and warm detection thresholds ranged from poor to excellent, while heat and cold pain thresholds ranged from fair to excellent. The methodological quality of research investigating the reliability of thermal QST warrants improvement, particularly in terms of appropriate blinding. The results from this review showed considerable variability in the reliability of each thermal QST parameter. [ABSTRACT FROM AUTHOR]

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Abstract: Different Lactobacillus collinoides and Brettanomyces/Dekkera anomala cider strains were studied for their ability to produce volatile phenols in synthetic medium. All strains were able to produce 4-ethylcatechol (4-EC), 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG) from caffeic, p-coumaric and ferulic acids, respectively. Interestingly, D. anomala and L. collinoides were also able to produce 4-EC, 4-EP and 4-EG in cider conditions. The quantities of ethylphenols produced by these two species were similar in both tested ciders. The impact of precursor quantities was studied and it showed that the addition of caffeic and p-coumaric acids in ciders allowed for higher 4-EC and 4-EP production by D. anomala and L. collinoides. In parallel, D. anomala and L. collinoides strains were isolated from a phenolic off-flavour defective bottled cider after ethylphenol production hence confirming the implication of these two species in this cider spoilage. Finally, detection thresholds of the main ethylphenols were determined in ciders by orthonasal and retronasal sampling. The 4-EC and 4-EP detection thresholds (close to 20–25mg/l and 1.5–2.0mg/l, respectively) were matrix dependant. [Copyright &y& Elsevier]

Abstract: Recent studies have shown that certain aromatic aldehydes are ligands for olfactory receptors expressed in mammalian sperm cells and induce sperm chemotaxis. Using a conditioning paradigm, the olfactory sensitivity of five CD-1 mice for seven aromatic aldehydes was investigated. With all seven stimuli, the mice discriminated concentrations as low as 0.01ppm (parts per million) from the solvent, and with bourgeonal the animals even detected concentrations as low as 0.1ppq (parts per quadrillion) which constitutes the lowest olfactory detection threshold value reported in this species so far. The presence of a tertiary butyl group in para-position (relative to the functional aldehyde group) combined with a lack of an additional alkyl group next to the functional aldehyde group may be responsible for the extraordinary sensitivity of the mice for bourgeonal. [Copyright &y& Elsevier]

Wine experts usually rely on chemical tracers of qualities or defects to judge wines. While part of their expertise is determined by their sensory ability to detect these key compounds, their level of sensitivity is generally unknown. The olfactory detection thresholds for 10 key odorant compounds in wine were, therefore, measured in a large sample of professionals (100 < n < 150). The experts' sensitivity to two tastants, tartaric acid and alum (respectively, sour and astringent compounds) was also tested. The study confirms that distributions of individual detection thresholds were very large (>3 log10 units). Comparing the abilities of the experts to detect the whole sample of chemicals tested, we showed that their sensitivity profiles were very different. Detection threshold distribution asymmetries suggested specific hyposmias or hyperosmias for b-ionone, 2-isobutyl-3-methoxypyrazine, 2,4,6-trichloroanisole, diacetyl, and linalool. Interestingly, we found that academic degrees in tasting and enology do have an impact on odor detection thresholds for two compounds, diacetyl and mixed ethylphenols. [ABSTRACT FROM AUTHOR]

This work addresses the unification of some basic functions and thresholds used in non-parametric estimation of signals by shrinkage in the wavelet domain. The soft and hard thresholding functions are presented as degenerate smooth sigmoid-based shrinkage functions. The shrinkage achieved by this new family of sigmoid-based functions is then shown to be equivalent to a regularization of wavelet coefficients associated with a class of penalty functions. Some sigmoid-based penalty functions are calculated, and their properties are discussed. The unification also concerns the universal and the minimax thresholds used to calibrate standard soft and hard thresholding functions: these thresholds pertain to a wide class of thresholds, called the detection thresholds. These thresholds depend on two parameters describing the sparsity degree for the wavelet representation of a signal. It is also shown that the non-degenerate sigmoid shrinkage adjusted with the new detection thresholds is as performant as the best up-to-date parametric and computationally expensive method. This justifies the relevance of sigmoid shrinkage for noise reduction in large databases or large size images. [ABSTRACT FROM AUTHOR]

Laryngeal control is essential for airway protection, breathing, deglutition, speech, and voice. Unfortunately, integration of laryngeal sensory assessment in research and clinical practice is limited by technical and practical limitations of commercially available technology. A commercial device is available, but reported limitations include procedural complexity requiring two or three individuals to operate, limited stimulus dynamic range, device generated noise, and questionable stimulus reproducibility. The objective of this study was to design a new laryngeal somatosensory stimulus delivery device that provides direct, reliable control over the timing, duration, and dynamic range of stimulus presentation, and test the device in individuals who may manifest a laryngeal sensory deficit. The new device operates silently and has more than four times greater stimulus dynamic range than the commercial device. Testing with the new device revealed laryngeal mechanosensory detection thresholds in an individual with Parkinson's disease that were seven times higher than those of healthy controls. These data would have otherwise gone undetected due to limited stimulus dynamic range in the commercial device. The new design resulted in a new assessment instrument that is simple to use for routine clinical assessment, yet sufficiently versatile for integration within rigorous clinical research protocols. [ABSTRACT FROM AUTHOR]

Using a conditioning paradigm, the olfactory sensitivity of four spider monkeys, three squirrel monkeys and three pigtail macaques to four thiols and two indols, substances characteristic of putrefaction processes and faecal odours, was assessed. With all odorants, the animals significantly discriminated concentrations below 1 p.p.m. (part per million) from the odourless solvent, and in several cases individual animals even demonstrated thresholds below 1 p.p.t. (part per trillion). The detection thresholds of 0.03 p.p.t. for indol in Saimiri sciureus and Macaca nemestrina and 0.96 p.p.t. for ethanethiol in Ateles geoffroyi represent the lowest values among the more than 50 odorants tested so far with these species and are in the same order of magnitude as the lowest detection thresholds reported so far in the rat and the mouse. The results showed (a) all three species of non-human primate to have a highly developed olfactory sensitivity for putrefaction-associated odorants, and (b) a significant correlation between perceptibility in terms of olfactory detection threshold and carbon chain length of the thiols, and a marked effect of the presence vs absence of a methyl group on perceptibility of the indols tested in two of the three species. The results support the hypotheses that (a) between-species differences in neuroanatomical or genetic features may not be indicative of olfactory sensitivity, and (b) within-species differences in olfactory sensitivity may reflect differences in the behavioural relevance of odorants. [ABSTRACT FROM AUTHOR]

This paper describes a systematic procedure for recognizing corrugated asbestos-cement roofing sheets and evaluating their deterioration status related to the asbestos fiber air dispersion that can cause lung cancer. To develop this procedure, we made field and laboratory measurements and gathered airborne MIVIS data covering two industrial test areas in Italy. Laboratory analyses of asbestos-cement samples representing various levels of deterioration allowed for: (a) recognizing dominant minerals using XRD and FTIR instruments, (b) identifying their optical characteristics using portable field spectrometers (ASD and μFTIR), (c) assessing the abundance of surfacing asbestos fibers using a high resolution scanner. Based on the spectral analyses, two linear regression lines were identified by relating optical asbestos-cement material characteristics (i.e. band-depth ratio of the continuum removed calculated for the two asbestos diagnostic bands at 2.32 μm and at 9.44 μm) to the relative percentage of surfacing asbestos fibers related to AC deterioration status. Suitable MIVIS spectral regions were used in a spectral classification procedure to map asbestos-cement roofs. The detected roofs were further analyzed using the obtained linear regression lines to estimate surfacing asbestos fiber abundance, using the MIVIS TIR range at 9.44 μm, selected by means of the asbestos-cement detection limit analysis. The results showed that a hyperspectral scanner with suitable operational characteristics allows for good clustering of AC roofs as a function of their deterioration status. Therefore, this technique can furnish government authorities with an efficient, rapid and repeatable environmental mapping procedure that can provide information about the location of hazardous AC roofing sheets. [Copyright &y& Elsevier]

Accumulating evidence suggests dietary fatty acids (FAs) may be sensed in the oral cavity. However, the effective cues have not been characterized. In particular, influences from other sensory cues have hampered identification of an independent gustatory contribution. Experiment 1 examined techniques to minimize the formation of FA oxidation products and improve the homogeneity of water/lipid emulsions to be used as stimuli in Experiment 2, a psychophysical study to determine FA detection thresholds in humans. Through sonication of chilled samples held in polypropylene labware and the addition of 0.01% ethylenediaminetetraacetic acid, calcium disodium salt, homogenous emulsions of unoxidized linoleic and oleic FAs were obtained. Spectrophotometric analysis revealed no oxidation product formation over a 24-h period. Coupled with these techniques, a masking approach was used to minimize other sensory cues imparted from linoleic, oleic, and stearic FAs. Concentration ranges from 0.00028% to 5% (w/v) were prepared in mixtures with 5% mineral oil (w/v) and 5% gum acacia (w/v) to mask lubricity and viscosity effects, respectively. Testing was conducted under red light with nares blocked to eliminate visual and olfactory cues. Oral rinses with 20 ppm capsaicin were administered to desensitize participants to selected irritation effects prior to remeasuring linoleic acid detection thresholds. To determine if the effective stimulus was an oxidation product, oxidized linoleic acid was included among the test stimuli. Detection thresholds were obtained using a 3-alternative, forced-choice ascending-concentration presentation procedure. The mean detection threshold for linoleic acid pre-desensitization was 0.034 ± 0.008%, for linoleic acid post-desensitization was 0.032 ± 0.007%, for oleic 0.022 ± 0.003%, for stearic 0.032 ± 0.005%, and oxidized linoleic 0.025 ± 0.005%. The results suggest that linoleic, oleic, stearic, and oxidized linoleic acids are detectable in the oral cavity of humans with minimal input from the olfactory, capsaicin, and viscosity-assessing tactile systems. [ABSTRACT FROM AUTHOR]

Selected free fatty acids (FFAs) are documented effective somatosensory and olfactory stimuli whereas gustatory effects are less well established. This study examined orthonasal olfactory, retronasal olfactory, nasal irritancy, oral irritancy, gustatory, and multimodal threshold sensitivity to linoleic, oleic, and stearic acids. Sensitivity to oxidized linoleic acid was also determined. Detection thresholds were obtained using a three-alternative, forced-choice, ascending concentration presentation procedure. Participants included 22 healthy, physically fit adults sensitive to 6-n-propylthiouracil. Measurable thresholds were obtained for all FFAs tested and in 96% of the trials. Ceiling effects were observed in the remaining trials. Greater sensitivity was observed for multimodal stimulation and lower sensitivity for retronasal stimulation. There were no statistically significant correlations for linoleic acid thresholds between different modalities, suggesting that each route of stimulation contributes independently to fat perception. In summary, 18-carbon FFAs of varying saturation are detected by multiple sensory systems in humans. [ABSTRACT FROM AUTHOR]

Abstract: Classification of terrestrial materials using remotely sensed imagery is becoming an increasingly popular method to assess natural systems. This study uses predictions derived from remotely sensed hyperspectral images to determine minimum target detection thresholds and to statistically constrain classification accuracies. Minimum detection thresholds are determined using an iterative regression breakpoint technique, and accuracy is delineated by quantifying the variance above the correlation breakpoint. Assessing confidence and determining detection limits generates a greater understanding of the classification process and adds significant utility to the classified product. [Copyright &y& Elsevier]

Using a conditioning paradigm, the olfactory sensitivity of six CD-1 mice for the enantiomers of carvone and of limonene as well as for their racemic mixtures was investigated. With all six stimuli, the animals significantly discriminated concentrations ≤0.1 ppm (parts per million) from the odorless solvent, and with five of the six stimuli, the best-scoring animals were even able to detect concentrations ≤1 ppb (parts per billion). Five spider monkeys tested in parallel were found to detect the same stimuli at concentrations <1 ppm, and with two of the stimuli, they were also able to discriminate concentrations <1 ppb from the solvent. The results showed 1) both CD-1 mice and spider monkeys to have a well-developed olfactory sensitivity for the stimuli tested, with no systematic difference in performance between species; 2) the effect of chirality on detectability of the enantiomers to be substance specific; 3) no systematic effect of the presence (carvone) or absence (limonene) of a functional carbonyl group on detectability of the enantiomers; and 4) that spider monkeys detected the racemic mixtures of both carvone and limonene at lower concentrations compared to the unmixed compounds, whereas the mice failed to do so. These findings lend support to the growing body of evidence suggesting that between-species comparisons of the relative size of olfactory brain structures do not allow us to reliably predict olfactory sensitivity. As mice and spider monkeys are thought to share a similar number of functional olfactory receptor genes, the findings further suggest that differences in the relative abundance of chiral-specific olfactory receptor types might account for the observed difference in mixture additivity at threshold level between the two species. These threshold data may provide useful information for the choice of adequate stimulus concentrations in electrophysiological or imaging studies of the olfactory system or investigations of the discriminative abilities of mice and spider monkeys. [ABSTRACT FROM AUTHOR]

Kveraga et al. (2002, Exp Brain Res 146(3):307-14) reported that saccade latencies are immune to the effects of stimulus-response uncertainty and constitute one of the few response systems that violate Hick’s law. Similar effects have been reported for keypresses triggered by vibrations of the fingertips, but robust uncertainty effects were subsequently revealed using weak, low-frequency vibrations (Ten Hoopen et al. 1982, Acta Psychol 50:143-157). We wondered whether immunity of saccadic responses would demonstrate a similar intensity-dependency and therefore re-examined the effects of response entropy on saccade latencies using near-threshold visual stimuli. Saccadic latencies remained independent of stimulus-response uncertainty, indicating that saccadic motor programming is unaffected by the duration of the target detection process. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated the ability of cochlear-implanted patients to discriminate tone bursts in free field using the electrophysiological recordings of mismatch negativity (MMN). Seven cochlear-implanted patients (CIP) and eight control subjects (CS) were tested. Event-related potentials were recorded from either 32 or 64 electrodes in response to binaural stimuli using a passive oddball paradigm. Two stimulus-contrast conditions were used to produce MMN: The standard-tone frequency was fixed at 1 kHz, and the deviant-tone frequency was set at 2 or 1.5 kHz. The results show that response waveforms (N1/P2) are similar in latency and amplitude for CS and CIP, suggesting that pure-tone detection is performed over the same time window in both groups. These waveforms are also similar in left- and right-implanted patients, suggesting that electric stimulation of the auditory nerve activates both hemispheres in profound, bilateral hearing loss. Pure-tone audiograms and word-discrimination scores were also measured in each subject in an anechoic room and their relations with MMN data were examined. Correlations were found between the latency of MMN for a 1.5 kHz deviant and the thresholds obtained for pure-tone detection and word discrimination. MMN appears as a possible complementary clinical tool to objectively assess auditory sensitivity in cochlear-implanted populations. However, further improvements are still necessary before it can be used as a standard clinical examination. [Copyright &y& Elsevier]

Using a conditioning paradigm, the olfactory sensitivity of three squirrel monkeys and three pigtail macaques for homologous series of aliphatic 2-ketones (2-butanone to 2-nonanone), symmetrical ketones (3-pentanone to 6-undecanone), and C7-ketones (2-heptanone to 4-heptanone) was assessed. In the majority of cases, the animals of both species significantly discriminated concentrations below 1 ppm from the odorless solvent, and with 2-nonanone and 5-nonanone the monkeys even demonstrated thresholds below 1 ppb. The results showed both primate species have a well-developed olfactory sensitivity for aliphatic ketones, and pigtail macaques generally perform better than squirrel monkeys in detecting members of this class of odorants. Further, in both species tested, we found a significant negative correlation between perceptibility in terms of olfactory detection thresholds and carbon-chain length of both the 2-ketones and the symmetrical ketones, but not between detection thresholds and position of the functional group with the C7-ketones. These findings lend further support to the growing body of evidence suggesting that between-species comparisons of the number of functional olfactory receptor genes or of neuroanatomical features are poor predictors of olfactory performance. [ABSTRACT FROM AUTHOR]

Functional implications of across-site variation in detection thresholds in subjects with cochlear implants were evaluated by comparing thresholds to speech recognition performance. Detection thresholds for bipolar (BP) and monopolar (MP) stimulation of all available stimulation sites were assessed in 21 subjects with Nucleus CI24M and CI24R(CS) implants. We found significant negative correlations between speech recognition and within-subject across-site threshold variance for both BP and MP stimulation, but no significant correlation of speech recognition with mean threshold levels. These results suggest that across-site variance of detection thresholds could provide a useful early indication of the prognosis for speech recognition and might serve as an indicator for specific therapeutic approaches in individual subjects. [ABSTRACT FROM AUTHOR]

Using a conditioning paradigm, the olfactory sensitivity of four spider monkeys and four pigtail macaques for a homologous series of carboxylic acids (n-propionic acid to n-heptanoic acid) was investigated. With only few exceptions, the animals of both species significantly discriminated concentrations <1 p.p.m. from the odorless solvent and in several cases individual monkeys even demonstrated thresholds <1 p.p.b. The results showed (i) both primate species to have a well-developed olfactory sensitivity for carboxylic acids, which for some substances matches or even is markedly better than that of species such as the rat or the dog and (ii) a significant correlation between perceptibility in terms of olfactory detection thresholds and carbon chain length of the carboxylic acids in both species tested. These findings lend further support to the growing body of evidence suggesting that between-species comparisons of the number of functional olfactory receptor genes or of neuroanatomical features are poor predictors of olfactory performance, and that general labels such as ‘microsmat’ or ‘macrosmat’—which usually are based on allometric comparisons of olfactory brain structures—are inadequate to describe a species’ olfactory capabilities. [ABSTRACT FROM AUTHOR]

Using a conditioning paradigm, the olfactory sensitivity of three squirrel monkeys and three pigtail macaques for a homologous series of aliphatic aldehydes (n-butanal to n-nonanal) was assessed. With only few exceptions, the animals of both species significantly discriminated concentrations below 1 ppm from the odorless solvent, and with n-butanal and n-hexanal individual pigtail macaques even demonstrated thresholds below 1 ppb. The results showed (1) both primate species to have a well-developed olfactory sensitivity for aliphatic aldehydes, (2) pigtail macaques to generally perform better than squirrel monkeys in detecting members of this class of odorants, and (3) no significant correlation between perceptibility in terms of olfactory detection thresholds and carbon chain length of the aliphatic aldehydes in both species tested. These findings lend further support to the growing body of evidence suggesting that between-species comparisons of the number of functional olfactory receptor genes or of neuroanatomical features are poor predictors of olfactory performance. Further, our findings suggest that olfaction may play an important and hitherto underestimated role in the regulation of behavior in the species tested. [ABSTRACT FROM AUTHOR]