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Multisensory integration processes are fundamental to our sense of self as embodied beings. Bodily illusions, such as the rubber hand illusion (RHI) and the size-weight illusion (SWI), allow us to investigate how the brain resolves conflicting multisensory evidence during perceptual inference in relation to different facets of body representation. In the RHI, synchronous tactile stimulation of a participant's hidden hand and a visible rubber hand creates illusory body ownership; in the SWI, the perceived size of the body can modulate the estimated weight of external objects. According to Bayesian models, such illusions arise as an attempt to explain the causes of multisensory perception and may reflect the attenuation of somatosensory precision, which is required to resolve perceptual hypotheses about conflicting multisensory input. Recent hypotheses propose that the precision of sensorimotor representations is determined by modulators of synaptic gain, like dopamine, acetylcholine, and oxytocin. However, these neuromodulatory hypotheses have not been tested in the context of embodied multisensory integration. The present, double-blind, placebo-controlled, crossover study ( n = 41 healthy volunteers) aimed to investigate the effect of intranasal oxytocin (IN-OT) on multisensory integration processes, tested by means of the RHI and the SWI. Results showed that IN-OT enhanced the subjective feeling of ownership in the RHI, only when synchronous tactile stimulation was involved. Furthermore, IN-OT increased an embodied version of the SWI (quantified as estimation error during a weight estimation task). These findings suggest that oxytocin might modulate processes of visuotactile multisensory integration by increasing the precision of top-down signals against bottom-up sensory input.

We injected serotonin (5-HT) into adult male crayfish before pairing them with size-matched non-injected competitors, and observed dyadic agonistic interactions. Paradoxically, 5-HT elicited opposite behavioral responses if the injected animal was opposed by a smaller or larger rival: the level of aggressiveness of the injected crayfish was higher when facing a larger rival but lower when facing a smaller rival. Our results indicate that the effects of 5-HT on aggressiveness are dependent on the perception of the relative size difference of the opponent. In both cases, however, 5-HT significantly delayed the decision to retreat. We conclude that 5-HT does not primarily act on aggressiveness but rather on the brain centers that integrate risk assessment and/or decision making, which then modulate the aggressive response. Our findings support a reinterpretation of the role of 5-HT in crustacean agonistic behavior that may be of interest for studies of other animals., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2018. Published by The Company of Biologists Ltd.)

Background: This study investigates whether cognitive impairment is evident in inpatients diagnosed with Major Depression (MD) following electro-convulsive therapy (ECT), and if so, whether it is independent from depressive symptomatology., Methods: Speed of information processing was measured using the inspection time (IT) task. IT was compared between twelve inpatients diagnosed with MD receiving ECT and twelve age-, gender-, verbal IQ-, and depression and anxiety severity matched control inpatients diagnosed with MD not receiving ECT, over four testing sessions (prior to ECT, following one ECT session, following the completion of an ECT block, and 4 to 6 weeks after the ECT block (follow-up))., Results: The mean IT score for the inpatients diagnosed with MD who received ECT slowed significantly from the first ECT to immediately after the ECT block, and was significantly faster at follow-up. The mean IT score of the inpatients diagnosed with MD not receiving ECT gradually but significantly became faster over the entire equivalent time period., Limitations: Small sample sizes., Conclusions: ECT temporarily slows information processing speed in MD patients, independent of depression symptomatology.

In normal subjects, alcohol increases handwriting size, but the mechanism is not understood. Here we show that the alcohol effect on handwriting can be explained by a selective impairment of kinaesthetic perception. Thirty volunteers (15 male, aged 18-29 years) took part in an open study. They were tested before and after a drink containing vodka intended to produce a blood alcohol concentration of about 80mg/100ml. Tests included kinaesthetic distance estimation, in which volunteers worked with preferred hand and arm behind a screen which hid their movements; visual distance estimation; and measures of handwriting and drawing. Blood alcohol concentration at 55min, based on breathalyser measurements, was 76.7mg/100ml (SD 9.8). When asked to move the hand and mark a distance of 10cm from a starting point, distances estimates increased by 7-10% (p 0.01). Similar increases were seen for writing words and drawing characters. Signatures were increased in height but not in length. Distances estimated visually were increased much less, by 3-4% (p 0.05). Tests of psychomotor performance indicated the expected effects of ethanol. These results suggest that ethanol affects writing size by reducing kinaesthetically perceived distances.

Ethanol may increase the willingness to take risks, but this issue remains controversial. We used a risk-taking paradigm in which volunteers answered a series of general knowledge questions with numerical answers and were asked to judge the length of a line that would just fit into a given gap. A maximum score was given for an exactly correct answer. For answers that were less than the correct value, the score was reduced gradually to zero, while answers even slightly over the correct value were penalized considerably. Total points were rewarded by cash payments, so volunteers were taking real risks when making their responses. Performance was assessed in a two-period, double-blind crossover study, comparing ethanol (0.7 g/kg) with placebo in 20 female volunteers aged 19-20 years. Tests were carried out before and at 45 min after dosing. Mean (SD) ethanol blood alcohol concentrations were 65 (10.5) mg/100 ml. Ethanol impaired the skill/ability measure of the length estimation test (SD of difference between length of line and gap), which increased from 5.9 to 6.6 (p < 0.05), indicating a reduced accuracy of estimation. The risk measures in both tasks were not significantly affected. The skill/ability measure in the general knowledge task was not significantly affected. Other performance tests showed that ethanol produced the expected impairment of both speed and accuracy. These results suggest that risk-taking is not increased by ethanol at doses approaching the UK legal limit for driving.

Previous studies have shown that crude ginseng extracts enhance performance on shock-motivated tasks. Whether such performance enhancements are due to memory-enhancing (nootropic) properties of ginseng, or to other non-specific effects such as an influence on anxiety has not been determined. In the present study, we evaluated both the nootropic and anxiolytic effects of the ginseng saponin Rb1. In the first experiment, 80 five-day-old male chicks received intraperitoneal injections of 0, 0.25, 2.5 or 5.0 mg/kg Rb1. Performance on a visual discrimination task was evaluated 15 minutes, 24 and 72 hours later. Acquisition of a visual discrimination task was unaffected by drug treatment, but the number of errors was significantly reduced in the 0.25 mg/kg group during retention trials completed 24 and 72 hours after injection. Animals receiving higher dosages showed trends towards enhancement initially, but demonstrated impaired performance when tested 72 hours later. Rb1 had no effect on response rates or body weight. In the second experiment, 64 five-day-old male chicks received similar injections of Rb1 (0, 0.25, 2.5 or 5.0 mg/kg) and separation distress was evaluated 15 minutes, 24 and 72 hours later. Rb1 produced a change in separation distress that depended on the dose and environmental condition under which distress was recorded. These data suggest that Rb1 can improve memory for a visual discrimination task and that the nootropic effect may be related to changes in anxiety.

Background: Slowing of the speed of information processing has been reported in geriatric depression, but it is not clear if the impairment is present in younger patients, if motor retardation is responsible, or if antidepressant medications play a role., Method: Twenty unmedicated unipolar depressed inpatients were compared with 19 medicated depressed in-patients and 20 age-, sex- and verbal IQ-matched controls on inspection time (IT), a measure of speed of information processing that does not require a speeded motor response. We also examined the relationship between IT and current mood and length of depressive illness., Results: Unmedicated depressed patients showed slowing of information processing speed when compared to both medicated depressed patients and controls. The latter two groups were not significantly different from each other. Slowing of IT was not associated with current mood, but was negatively correlated with length of illness since first episode. No differences in IT were found between patients receiving medication with anticholinergic effects and patients receiving medication with no anticholinergic effects., Conclusions: The findings indicate that unipolar depression is associated with a slowing of speed of information processing in younger patients who have not received antidepressant medication. This does not appear to be a result of motor slowing.

This study assessed the kinematic changes to the reach to grasp movement in response to a perturbation of object size in 15 Parkinson's disease (PD) and 15 control subjects. For non-perturbed trials subjects reached 35 cm to grasp and lift either an illuminated small (0.7 cm) or large (8 cm) diameter cylinder. For perturbed trials (20%), illumination shifted unexpectedly from the small to the large or from the large to the small cylinder at the onset of the reach. For Condition One trials subjects were given no instructions as to which grasp to use. With perturbation, they thus naturally changed grasp from precision grip to whole hand prehension or vice versa. The results for the PD subjects indicated a slowness at the transition from one to another grasp. This contrasted to the smooth transitions when perturbation required only a change of grasp aperture (precision grip--Condition Two; whole hand prehension--Condition Three). PD subjects thus showed dysfunction in the suppression/activation of different grasp programs rather than deficits in the on-line modification of an operating program.

After systemic administration of the dopamine agonist apomorphine (APO) in common toads Bufo bufo spinosus, the excitatory receptive fields of retinal R2 and R3 ganglion cells doubled their size and the response activities of these neurons to moving visual stimuli were generally increased. Comparable investigations of the stimulus-response relationships in the snapping behavior of toads pre- and post-APO showed a general increase in the snapping responses, but no shift in the preferred prey size. This is consistent with the current concept, suggesting that size evaluation in amphibians does not rely on retinal ganglion cell output but on interacting networks beyond the retina.

A group of 11 hashish users were compared with 11 controls on a visual sustained attention (vigilance) task. Analysis indicated that hashish use affected subjects' sensitivity. Subjects who used hashish responded in an indiscriminate manner, making more false alarms (8.7) than controls (2.6). The importance of vigilance in the assessment of adverse effects of hashish is discussed.

The effects of placebo, triazolam (2.0, 4.0 and 8.0 micrograms/kg) and ethanol (0.25, 0.5, 1.0 g/kg) on perceptual-motor performance were examined using a visual pattern matching-to-sample procedure in which pattern size and comparison stimulus discriminability were systematically varied. Baseline response rates and accuracy increased as the discriminability of the comparison stimuli increased. At the highest dose, both drugs decreased response accuracy. This disruption of accuracy was attenuated by increasing the discriminability of non-matching stimuli. Triazolam produced dose-related decreases in response rate while ethanol produced only slight decreases at the highest baseline rates of responding. Thus, triazolam produced response rate slowing at relatively lower doses than ethanol.

Chicks 5 days old received intraperitoneal injections of nimodipine 30 min before training on either a visual discrimination task (0, 0.5, 1.0, or 5.0 mg/kg) or a test of separation-induced distress vocalizations (0, 0.5, or 2.5 mg/kg). Chicks receiving 1.0 mg/kg nimodipine made significantly fewer visual discrimination errors than vehicle controls by trials 41-60, but did not differ from controls 24 h later. Chicks in the 5 mg/kg group made significantly more errors when compared to controls both during acquisition of the task and during retention. Nimodipine did not alter separation-induced distress vocalizations at any of the doses tested, suggesting that nimodipine's effects on learning cannot be attributed to a reduction in separation distress. These data indicate that nimodipine's facilitation of learning in young subjects is dose dependent, but nimodipine failed to enhance retention.

The effects of the constancy phenomena in vision seem to be to provide information about the environment which is not solely dependent upon the characteristics of shape or size of the retinal image but which is modified by the brain to appear closer to the idealized characteristics of the real object. There is a regression away from the retinal image towards the actual object's characteristics. A plate viewed from an angle tends to look more like a disc than would be predicted from the geometry of perspective. This ability of the brain to impose conditions on perception is a high-level process which may be adversely affected by the depressive action of alcohol on the nervous system. In this case, objects such as road signs, etc. would tend to look smaller and so more distant than when sober if regression is inhibited. Drivers' reactions may be delayed if hazards are seen smaller and further away, thereby increasing the possibility of accident. This research indicates a reduction in phenomenal regression after ingestion of alcohol. There are implications for accident-rates in driving or in industry.

Motor alimentary conditioned reflex was elaborated in Wistar line rats to presentation of various pairs of figures, those of larger area serving as positive signals. In tests on animals with intact brain and with unilateral hemispheric cortical inactivation, new pairs of figures were used besides basic stimuli. The level of analysis in testing experiment was lower than normal: by 5.6% at intact brain, by 16.4%--at right hemisphere inactivation, by 36.4%--at left hemisphere inactivation. Elimination of the left hemisphere produced prolongation of the conditioned reaction time, signs of frustration and aftereffect. In conditions of right hemisphere inactivation the level of discrimination of figures depended on their specific properties and the side of presentation. Conclusion is made on dominating role of the left hemisphere in analysis of abstract and concrete characteristics of visual stimuli, in control of temporal, spatial and emotional characteristics of reactions in situations when considerable abstraction and distinguishing of generalizing invariant sign "more-less" is necessary for elaboration of the conditioned reflex.

The dimension discrimination ability of twenty-five young persons was tested at two different degrees of mouth opening. One reference stick of 10-0 mm and another of 45-0 mm was placed between the teeth, alternating with test sticks of different heights. The subjects were asked to assess whether a test stick felt higher or lower than the reference stick. The experiment was performed with and without anaesthesia applied to the periodontal ligaments. Anaesthesia did not impair the discrimination ability. At dimensions in the region of the 10-0 mm stick the incorrect assessments occurred predominantly among sticks higher than the reference stick. Around the 45-0 mm stick incorrect assessments were distributed evenly between dimensions higher or lower than the reference stick.

A central feature of the impairment in performance produced by inert gas narcosis, which poses a threat to divers breathing compressed air, is a slowing of reaction time (RT). To investigate the locus of this slowing, the effects of 35% nitrous oxide on Crossman's confusion function were determined using line-length and weight discrimination tasks, with accuracy held constant. For both tasks narcosis slowed RT by increasing the intercept rather than the slope of Crossman's function. These results are interpreted in terms of additive factors method logic as being consistent with the predictions of the slowed processing model that has been proposed to account for the effects of narcosis on human performance.

From the McClelland et al. theory it was hypothesized that the distribution of power defined in terms of both outcome and process would be affected by alcohol in a man-woman dyad interaction situation by increasing power of the intoxicated partner. Man-woman couples (N = 30) were randomly assigned to an alcohol, a placebo or a control group. The men in the alcohol group were served a beverage containing 0.8 ml of absolute alcohol per kg of body weight. In the placebo group, the men were served a drink of orange juice and vodka essence, and the men in the control group received only orange juice. The women in all groups were served only orange juice. The same information about the kind of drinks to be served was given to both the men and the women in their respective groups. Each couple was tested individually and the experimental task consisted of 20 equal trials. The man and the woman were asked to give an individual estimation of the length of a line projected on a screen. They were then instructed to discuss their individual answers and to come to a mutual agreement on the length of the line. Outcome power was defined as the influence each one had on the actual decision and process power as each one's influence on the interaction process. Results clearly show that sober women increase their outcome power and responsibility aspects of process power over the intoxicated men, while the intoxicated men retain some of their process power as estimated in quantitative terms. The hypothesis was not supported and alternative explanations were discussed.