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Hearing a beat recruits a wide neural network that involves the auditory cortex and motor planning regions. Perceiving a beat can potentially be achieved via vision or even touch, but it is currently not clear whether a common neural network underlies beat processing. Here, we used functional magnetic resonance imaging (fMRI) to test to what extent the neural network involved in beat processing is supramodal, that is, is the same in the different sensory modalities. Brain activity changes in 27 healthy volunteers were monitored while they were attending to the same rhythmic sequences (with and without a beat) in audition, vision and the vibrotactile modality. We found a common neural network for beat detection in the three modalities that involved parts of the auditory dorsal pathway. Within this network, only the putamen and the supplementary motor area (SMA) showed specificity to the beat, while the brain activity in the putamen covariated with the beat detection speed. These results highlighted the implication of the auditory dorsal stream in beat detection, confirmed the important role played by the putamen in beat detection and indicated that the neural network for beat detection is mostly supramodal. This constitutes a new example of convergence of the same functional attributes into one centralized representation in the brain., (© 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)

Tinnitus is the perception of sound in the absence of external stimulus. Currently, the pathophysiology of tinnitus is not fully understood, but recent studies indicate that alterations in the brain involve non-auditory areas, including the prefrontal cortex. In experiment 1, we used a go/no-go paradigm to evaluate the target detection speed and the inhibitory control in tinnitus participants (TP) and control subjects (CS), both in unimodal and bimodal conditions in the auditory and visual modalities. We also tested whether the sound frequency used for target and distractors affected the performance. We observed that TP were slower and made more false alarms than CS in all unimodal auditory conditions. TP were also slower than CS in the bimodal conditions. In addition, when comparing the response times in bimodal and auditory unimodal conditions, the expected gain in bimodal conditions was present in CS, but not in TP when tinnitus-matched frequency sounds were used as targets. In experiment 2, we tested the sensitivity to cross-modal interference in TP during auditory and visual go/no-go tasks where each stimulus was preceded by an irrelevant pre-stimulus in the untested modality (e.g. high frequency auditory pre-stimulus in visual no/no-go condition). We observed that TP had longer response times than CS and made more false alarms in all conditions. In addition, the highest false alarm rate occurred in TP when tinnitus-matched/high frequency sounds were used as pre-stimulus. We conclude that the inhibitory control is altered in TP and that TP are abnormally sensitive to cross-modal interference, reflecting difficulties to ignore irrelevant stimuli. The fact that the strongest interference effect was caused by tinnitus-like auditory stimulation is consistent with the hypothesis according to which such stimulations generate emotional responses that affect cognitive processing in TP. We postulate that executive functions deficits play a key-role in the perception and maintenance of tinnitus.

Purpose: Tinnitus is the perception of a sound in the absence of external stimulus. Currently, the pathophysiology of tinnitus is not fully understood, but recent studies indicate that alterations in the brain involve non-auditory areas, including the prefrontal cortex. Here, we hypothesize that these brain alterations affect top-down cognitive control mechanisms that play a role in the regulation of sensations, emotions and attention resources., Methods: The efficiency of the executive control as well as simple reaction speed and processing speed were evaluated in tinnitus participants (TP) and matched control subjects (CS) in both the auditory and the visual modalities using a spatial Stroop paradigm., Results: TP were slower and less accurate than CS during both the auditory and the visual spatial Stroop tasks, while simple reaction speed and stimulus processing speed were affected in TP in the auditory modality only., Conclusions: Tinnitus is associated both with modality-specific deficits along the auditory processing system and an impairment of cognitive control mechanisms that are involved both in vision and audition (i.e. that are supra-modal). We postulate that this deficit in the top-down cognitive control is a key-factor in the development and maintenance of tinnitus and may also explain some of the cognitive difficulties reported by tinnitus sufferers.

Aim: Sensory substitution (SS) represents a unique opportunity to provide congenitally blind persons with visual-like experience. Although visual experience influences the way we perceive the external world, little is known about the effects of SS experience., Purpose: To investigate the effects of perceptual experience (visual versus sensory substitution) on depth perception through an SS system, object localization abilities of early blind (n = 10), and blindfolded sighted control subjects (n = 20) were assessed before and after a practicing period with a visual-to-auditory SS device., Method: During the pre- and post-test, subjects had to replace, by hand, an object previously localized using the device. The practicing phase consisted of three sessions during which subjects tried to localize and grasp an object using the device. Results. At the pre-test, sighted subjects spontaneously used efficiently different pictorial depth cues to estimate object distance while the blind subjects were affected by their lack of visual experience and were significantly less accurate. Post-test showed that the brief practicing phase sufficed to enable blind subjects to acquire the rules of visual depth and to use them efficiently with the device., Conclusions: These results suggest the possibility to compensate for some effects of early and long-lasting blindness by providing visual-like experience via SS. Theoretical implications are discussed.

We have previously shown that some visual motion areas can be specifically recruited by auditory motion processing in blindfolded sighted subjects [Poirier, C., Collignon, O., De Volder, A.G., Renier, L., Vanlierde, A., Tranduy, D., Scheiber, C., 2005. Specific activation of V5 brain area by auditory motion processing: an fMRI study. Brain Res. Cogn. Brain Res. 25, 650-658]. The present fMRI study investigated whether auditory motion processing may recruit the same brain areas in early blind subjects. The task consisted of simultaneously determining both the nature of a sound stimulus (pure tone or complex sound) and the presence or absence of its movement. When a movement was present, blind subjects had to identify its direction. Auditory motion processing, as compared to static sound processing, activated the brain network of auditory and visual motion processing classically observed in sighted subjects. Accordingly, brain areas previously considered as specific to visual motion processing could be specifically recruited in blind people by motion stimuli presented through the auditory modality. This indicates that the occipital cortex of blind people could be organized in a modular way, as in sighted people. The similarity of these results with those we previously observed in sighted subjects suggests that occipital recruitment in blind people could be mediated by the same anatomical connections as in sighted subjects.

This experiment was undertaken to investigate the effect of sensory modality (vision vs. audition) and of visual status (early blind vs. sighted) on susceptibility to the vertical-horizontal illusion. Early blind volunteers and blindfolded sighted subjects explored variants of the vertical-horizontal illusion using a device that substituted audition for vision, whereas sighted subjects from an independent group inspected the same stimuli visually. Sensitivity to the vertical-horizontal illusion, including an illusion of moderate strength when using the sensory substitution device, was observed only in the two sighted groups. The existence of an illusion effect when using such a device supports the idea of a visual perception provided by sensory substitution, whereas the attenuation of the vertical-horizontal illusion strength is consistent with the visual field shape theory (Künnapas, 1955a). The absence of the illusion effect in early blind subjects suggests that the sensory experience influences the nature of perception and that the visual experience plays a crucial role in the vertical-horizontal illusion, in accordance with the size-constancy scaling theory (Gregory, 1963).

Sensory substitution refers to the use of one sense to pick up information normally gathered by another sensory organ. With recent technological advances and scientific progress, sensory substitution appears as an interesting alternative for restoring some functions of a defective sensory organ (e.g., the sight in case of blindness). At the same time, our knowledge about cognitive and brain mechanisms involved in sensory substitution has grown considerably, bringing new insights into human perception and neural plasticity. From this perspective, sensory substitution can be considered as both a tool to investigate human cognition and brain functions, and a research topic in its own right. This paper addresses some of the major questions raised by sensory substitution, demonstrates how the study of sensory substitution enhances our understanding of human perception and brain plasticity and provides an overview of rehabilitation potentialities.

Using positron emission tomography, regional cerebral blood flow was studied in five early blind and five control volunteers during visuo-spatial imagery. Subjects were instructed to generate a mental representation of verbally provided bidimensional patterns that were placed in a grid and to assess pattern symmetry in relation to a grid axis. This condition was contrasted with a verbal memory task. Cerebral activation in both groups was similar during the visuo-spatial imagery task. It involved the precuneus (BA 7), superior parietal lobule (BA 7), and occipital gyrus (BA 19). These results are in accordance with previous studies conducted in sighted subjects that indicated that the same occipito-parietal areas are involved in visual perception as well as in mental imagery dealing with spatial components. The dorsal pathway seems to be involved in visuo-spatial imagery in early blind subjects, indicating that this pathway undergoes development in the absence of vision.

Brain glucose metabolism was studied, using positron emission tomography and [F-18]-2-deoxy-2-fluoro-D-glucose, in 13 healthy young adult men, at rest and under conditions of high visual and auditory stimulation with minor motor involvement. Despite high individual variations, the mean cerebral metabolic rate for glucose was highly increased during stimulation. Furthermore, the regional pattern of cerebral glucose utilization showed consistent differences between resting and activated states. Several brain areas, including temporal, motor-premotor and parieto-occipital cortices, and striatum, thalamus, and cerebellum showed a level of activation statistically comparable to that of mean gray. Significant preferential activation was found only in the visual cortex. By contrast, prefrontal and mesial cortical areas were relatively hypoactivated by the task. Inasmuch as prefrontal cortex is known to receive visual associative afferents, these observations are tentatively interpreted in terms of the "parallel" mode of information processing, along specific routes according to the environmental state.