Superior Temporal Sulcus Area Research Articles

Motor Circuit and Superior Temporal Sulcus Activities Linked to Individual Differences in Multisensory Speech Perception.

Integrating multimodal information into a unified perception is a fundamental human capacity. McGurk effect is a remarkable multisensory illusion that demonstrates a percept different from incongruent auditory and visual syllables. However, not all listeners perceive the McGurk illusion to the same degree. The neural basis for individual differences in modulation of multisensory integration and syllabic perception remains largely unclear. To probe the possible involvement of specific neural circuits in individual differences in multisensory speech perception, we first implemented a behavioral experiment to examine the McGurk susceptibility. Then, functional magnetic resonance imaging was performed in 63 participants to measure the brain activity in response to non-McGurk audiovisual syllables. We revealed significant individual variability in McGurk illusion perception. Moreover, we found significant differential activations of the auditory and visual regions and the left Superior temporal sulcus (STS), as well as multiple motor areas between strong and weak McGurk perceivers. Importantly, the individual engagement of the STS and motor areas could specifically predict the behavioral McGurk susceptibility, contrary to the sensory regions. These findings suggest that the distinct multimodal integration in STS as well as coordinated phonemic modulatory processes in motor circuits may serve as a neural substrate for interindividual differences in multisensory speech perception.

Cerebral Sulcal Asymmetry in Macaque Monkeys

The asymmetry of the cerebral sulcal morphology is particularly obvious in higher primates. The sulcal asymmetry in macaque monkeys, a genus of the Old World monkeys, in our previous studies and others is summarized, and its evolutionary significance is speculated. Cynomolgus macaques displayed fetal sulcation and gyration symmetrically, and the sulcal asymmetry appeared after adolescence. Population-level rightward asymmetry was revealed in the length of arcuate sulcus (ars) and the surface area of superior temporal sulcus (sts) in adult macaques. When compared to other nonhuman primates, the superior postcentral sulcus (spcs) was left-lateralized in chimpanzees, opposite of the direction of asymmetry in the ars, anatomically-identical to the spcs, in macaques. This may be associated with handedness: either right-handedness in chimpanzees or left-handedness/ambidexterity in macaques. The rightward asymmetry in the sts surface area was seen in macaques, and it was similar to humans. However, no left/right side differences were identified in the sts morphology among great apes, which suggests the evolutionary discontinuity of the sts asymmetry. The diversity of the cortical lateralization among primate species suggests that the sulcal asymmetry reflects the species-related specialization of the cortical morphology and function, which is facilitated by evolutionary expansion in higher primates.

Yüz Tanıma Alanı (Gyrus Fusiformis): Betimleyici Bir İnceleme

People recognise each other with faces. For this reason, the ability to recognize and remember faces is very important for the social functioning of a person. For these processes involve a network of interrelated brain regions including, such as occipital face area in inferior occipital gyrus, fusiform face area in fusiform gyrus and facial expression recognition area in superior temporal sulcus.

FV 2. Modulation of the cortical vestibular network by means of rTMS and its neural correlate

Repetitive transcranial magnetic stimulation (rTMS) has been applied to sensory research and for the treatment of disorders in psychiatry and neurology since 1993 ( Wassermann and Zimmermann, 2012 ). The widespread cortical vestibular system, however, has to date not been targeted. Aim of our study was to manipulate vestibular regions in the human cortex by temporary virtual lesioning through rTMS and analyse the changes in the perception of a galvanic vestibular stimulation (GVS) as well as the differing activation patterns in functional neuroimaging. The effects of rectangular and sinusoidal bimastoidal GVS were studied in 16 healthy volunteers (8 F; mean age 23 years) in a 3T scanner. Data was analysed with SPM12. Results of the baseline fMRI session were used as functional localizers for three rTMS target regions: (1) cingulate sulcus visual (CSv) bilaterally, (2) the right inferior parietal lobule (BA40), and (3) the right polysensory superior temporal sulcus area (STP) ( Smith, 2012 ). The vestibular fMRI sessions with GVS were repeated within minutes after virtual lesioning of the target regions with low-frequency rTMS (1 Hz, 1800 pulses, 90% active motor threshold) followed by a psychophysical debriefing and a clinical neurootological examination. Generally speaking virtual lesioning of vestibular cortex areas by means of rTMS resulted in a reduced, never in a more pronounced, activation pattern of the cortical vestibular regions. (1) RTMS of area CSv bilaterally led to a reduction in vestibular activation of area 6, area MST, and the inferior parietal lobule in both hemispheres. For unilateral galvanic stimuli this effect was constricted to the cerebral hemisphere ipsilateral to the side of excitation. More subjects perceived their head to be rotating in space during sinusoidal GVS instead of the sensation of the whole body twirling compared to all other sessions (72% vs 30%). (2) Virtual lesioning of the right inferior parietal lobule lead to reduced activation of the target region itself and area 6 in the same hemisphere during GVS. Here, subjects showed the largest reduction in grading the perceived amount of rotation induced by rectangular GVS (mean reduction of 45 ± 7° compared to the baseline session). The effect of a significantly reduced sensation of head rotation during GVS was seen in all target areas. (3) RTMS of area STP lead to a significant isolated deactivation of the left midbrain during GVS. There were no pathological findings in our healthy subjects after the virtual lesioning in the ensuing clinical neurootological examinations. The realignment parameters of the vestibular stimulations as a correlate for a potential vestibular motor response also gave no significant differences between the four sessions. This is the first demonstration by means of psychophysics, fMRI and rTMS that points at the potential for a manipulation of vestibular cortex regions. Global cerebral network effects within the vestibular system were only seen after rTMS lesioning of the vestibular midline structure CSv bilaterally. The resulting shift from body to isolated head rotation in space in the perception after GVS for the lesioned area CSv could reflect its role in egomotion processing. The quantitative perceptual findings for the right inferior parietal lobule as an rTMS lesion site on the other hand might suggest a leading role for this region in egocentric referencing within the confines of a three-dimensional environment.

Functional columns in superior temporal sulcus areas of the common marmoset.

Cortical areas in the superior temporal sulcus (STS) of primates have been recognized as a part of the 'social brain'. In particular, biological motion stimuli elicit neuronal responses in the STS, indicating their roles in the ability to understand others' actions. However, the spatial organization of functionally identified STS cells is not well understood because it is difficult to identify the precise locations of cells in sulcal regions. Here, using a small New World monkey, the common marmoset (Callithrix jacchus) that has a lissencephalic brain, we investigated the spatial organization of the cells responsive to other's actions in STS. The neural responses to movies showing several types of other's actions were recorded with multicontact linear-array electrodes that had four shanks (0.4 mm spacing), with eight electrode contacts (0.2 mm spacing) for each shank. The four shanks were penetrated perpendicular to the cortical surface. We found that STS cells significantly responded to other's goal-directed actions, such as when an actor marmoset was reaching for and grasping a piece of food. The response profiles to the movies were more similar between the vertically positioned electrodes than horizontally positioned electrodes when the distances between electrodes were matched. This indicates that there are functional columns in the higher-order visual areas in STS of the common marmoset.

Pure word deafness with auditory object agnosia after bilateral lesion of the superior temporal sulcus

Based on results from functional imaging, cortex along the superior temporal sulcus (STS) has been suggested to subserve phoneme and pre-lexical speech perception. For vowel classification, both superior temporal plane (STP) and STS areas have been suggested relevant. Lesion of bilateral STS may conversely be expected to cause pure word deafness and possibly also impaired vowel classification. Here we studied a patient with bilateral STS lesions caused by ischemic strokes and relatively intact medial STPs to characterize the behavioral consequences of STS loss. The patient showed severe deficits in auditory speech perception, whereas his speech production was fluent and communication by written speech was grossly intact. Auditory-evoked fields in the STP were within normal limits on both sides, suggesting that major parts of the auditory cortex were functionally intact. Further studies showed that the patient had normal hearing thresholds and only mild disability in tests for telencephalic hearing disorder. Prominent deficits were discovered in an auditory-object classification task, where the patient performed four standard deviations below the control group. In marked contrast, performance in a vowel-classification task was intact. Auditory evoked fields showed enhanced responses for vowels compared to matched non-vowels within normal limits. Our results are consistent with the notion that cortex along STS is important for auditory speech perception, although it does not appear to be entirely speech specific. Formant analysis and single vowel classification, however, appear to be already implemented in auditory cortex on the STP.

Mapping the macaque superior temporal sulcus: functional delineation of vergence and version eye-movement-related activity.

It is currently thought that the primate oculomotor system has evolved distinct but interrelated subsystems to generate different types of visually guided eye movements (e.g., saccades/smooth pursuit/vergence). Although progress has been made in elucidating the neural basis of these movement types, no study to date has investigated all three movement types on a large scale and within the same animals. Here, we used fMRI in rhesus macaque monkeys to map the superior temporal sulcus (STS) for BOLD modulation associated with visually guided eye movements. Further, we ascertained whether modulation in a given area was movement type specific and, if not, the modulation each movement type elicited relative to the others (i.e., dominance). Our results show that multiple areas within STS modulate during all movement types studied, including the middle temporal, medial superior temporal, fundus of the superior temporal, lower superior temporal, and dorsal posterior inferotemporal areas. Our results also reveal an area in dorsomedial STS that is modulated almost exclusively by vergence movements. In contrast, we found that ventrolateral STS is driven preferentially during versional movements. These results illuminate an STS network involved in processes associated with multiple eye movement types, illustrate unique patterns of modulation within said network as a function of movement type, and provide evidence for a vergence-specific area within dorsomedial STS. We conclude that producing categorically different eye movement types requires access to a common STS network and that individual network nodes are recruited differentially based upon the type of movement generated.

P 148. Anticipatory motor simulation of deceptive actions in soccer players

The ability to form anticipatory representations of ongoing actions is crucial for meaningful and effective interactions in dynamic environments. Previous research has shown that simulating and predicting the outcome of ongoing actions is modulated by motor expertise. In sports, elite athletes exhibit great ability in predicting other players’ actions, mainly based on action body kinematics as well as visual body representations. Surprisingly, there has been little evidence so far on how motor experts such as athletes perceive and/or anticipate bluffing actions. A few studies applying temporal occlusion paradigms have shown that expert players are better in detecting deceptive actions compared to expert observers. A recent study by Tomeo et al. (2012) in soccer players has found that the ability to detect deceptive actions relies on a complex mechanism of inhibitory and excitatory processes within the motor system. Furthermore, it was indicated that the balance between these processes depends on both visual and motor expertise. The present study has tried to identify the involvement and interactions between visual and motor areas concerning the detection of bluffing actions in soccer penalty kicks. We used the experimental paradigm described by Tomeo et al. (2012) , during which subjects (expert kickers, goalkeepers and novices) were judging the direction of the ball after a penalty kick, and we applied a repetitive TMS methodology in order to cause online disruption of two different regions; the dorsal premotor cortex (PMd) and the superior temporal sulcus (STS). Results have shown a strong modulation in the task performance between the sample groups caused by disruption of the STS area compared to control areas. Hence, new evidence is provided on how visual and motor expertise contributes to representing actions and detecting bluffing actions.

Dissimilar processing of emotional facial expressions in human and monkey temporal cortex.

Emotional facial expressions play an important role in social communication across primates. Despite major progress made in our understanding of categorical information processing such as for objects and faces, little is known, however, about how the primate brain evolved to process emotional cues. In this study, we used functional magnetic resonance imaging (fMRI) to compare the processing of emotional facial expressions between monkeys and humans. We used a 2×2×2 factorial design with species (human and monkey), expression (fear and chewing) and configuration (intact versus scrambled) as factors. At the whole brain level, neural responses to conspecific emotional expressions were anatomically confined to the superior temporal sulcus (STS) in humans. Within the human STS, we found functional subdivisions with a face-selective right posterior STS area that also responded to emotional expressions of other species and a more anterior area in the right middle STS that responded specifically to human emotions. Hence, we argue that the latter region does not show a mere emotion-dependent modulation of activity but is primarily driven by human emotional facial expressions. Conversely, in monkeys, emotional responses appeared in earlier visual cortex and outside face-selective regions in inferior temporal cortex that responded also to multiple visual categories. Within monkey IT, we also found areas that were more responsive to conspecific than to non-conspecific emotional expressions but these responses were not as specific as in human middle STS. Overall, our results indicate that human STS may have developed unique properties to deal with social cues such as emotional expressions.

8. Sulcus temporalis superior

Superior temporal sulcus (STS) is a brain structure, which has been related to many cognitive functions recently. It can be presumed that it is a part of many cognitive functions and that in particular situation, its relationship with other brain areas is relevant. Our work aimed to its effective connectivity during processing of potentially relevant unusual events. Twenty healthy volunteers were investigated by functional magnetic resonance during visual oddball task – they were instructed to react to different visual stimuli, randomly dislocated among frequent ones. Further processing was done by SPM5 programme. Next step was psychophysiological interaction analysis, method of effective connectivity. We have detected two areas related to target stimuli detection in STS. The anterior area had increased connectivity with mesiotemporal cortices, the posterior one with anterior cingulate cortex. We have found decreased connectivity of the anterior area with dorsolateral prefrontal cortex and the posterior area with parietal cortex – attention related structures. We can hypothesize that STS in detection of rare events is not related to attention, but to later stages of stimuli processing. This hypothesis is supported by association of STS and mesiotemporal areas.

Direct Structural Connections between Voice- and Face-Recognition Areas

Currently, there are two opposing models for how voice and face information is integrated in the human brain to recognize person identity. The conventional model assumes that voice and face information is only combined at a supramodal stage (Bruce and Young, 1986; Burton et al., 1990; Ellis et al., 1997). An alternative model posits that areas encoding voice and face information also interact directly and that this direct interaction is behaviorally relevant for optimizing person recognition (von Kriegstein et al., 2005; von Kriegstein and Giraud, 2006). To disambiguate between the two different models, we tested for evidence of direct structural connections between voice- and face-processing cortical areas by combining functional and diffusion magnetic resonance imaging. We localized, at the individual subject level, three voice-sensitive areas in anterior, middle, and posterior superior temporal sulcus (STS) and face-sensitive areas in the fusiform gyrus [fusiform face area (FFA)]. Using probabilistic tractography, we show evidence that the FFA is structurally connected with voice-sensitive areas in STS. In particular, our results suggest that the FFA is more strongly connected to middle and anterior than to posterior areas of the voice-sensitive STS. This specific structural connectivity pattern indicates that direct links between face- and voice-recognition areas could be used to optimize human person recognition.

White-Matter Connectivity between Face-Responsive Regions in the Human Brain

Face recognition is of major social importance and involves highly selective brain regions thought to be organized in a distributed functional network. However, the exact architecture of interconnections between these regions remains unknown. We used functional magnetic resonance imaging to identify face-responsive regions in 22 participants and then employed diffusion tensor imaging with probabilistic tractography to establish the white-matter pathways between these functionally defined regions. We identified strong white-matter connections between the occipital face area (OFA) and fusiform face area (FFA), with a significant right-hemisphere predominance. We found no evidence for direct anatomical connections between FFA and superior temporal sulcus (STS) or between OFA and STS, contrary to predictions based on current cognitive models. Instead, our findings point to segregated processing along a ventral extrastriate visual pathway to OFA-FFA and another more dorsal system connected to STS and frontoparietal areas. In addition, early occipital areas were found to have direct connections to the amygdala, which might underlie a rapid recruitment of limbic brain areas by visual inputs bypassing more elaborate extrastriate cortical processing. These results unveil the structural neural architecture of the human face recognition system and provide new insights on how distributed face-responsive areas may work together.

Explicit Encoding of Multimodal Percepts by Single Neurons in the Human Brain

Different pictures of Marilyn Monroe can evoke the same percept, even if greatly modified as in Andy Warhol's famous portraits. But how does the brain recognize highly variable pictures as the same percept? Various studies have provided insights into how visual information is processed along the "ventral pathway," via both single-cell recordings in monkeys and functional imaging in humans. Interestingly, in humans, the same "concept" of Marilyn Monroe can be evoked with other stimulus modalities, for instance by hearing or reading her name. Brain imaging studies have identified cortical areas selective to voices and visual word forms. However, how visual, text, and sound information can elicit a unique percept is still largely unknown. By using presentations of pictures and of spoken and written names, we show that (1) single neurons in the human medial temporal lobe (MTL) respond selectively to representations of the same individual across different sensory modalities; (2) the degree of multimodal invariance increases along the hierarchical structure within the MTL; and (3) such neuronal representations can be generated within less than a day or two. These results demonstrate that single neurons can encode percepts in an explicit, selective, and invariant manner, even if evoked by different sensory modalities.

Modulation of perception and brain activity by predictable trajectories of facial expressions.

People track facial expression dynamics with ease to accurately perceive distinct emotions. Although the superior temporal sulcus (STS) appears to possess mechanisms for perceiving changeable facial attributes such as expressions, the nature of the underlying neural computations is not known. Motivated by novel theoretical accounts, we hypothesized that visual and motor areas represent expressions as anticipated motion trajectories. Using magnetoencephalography, we show predictable transitions between fearful and neutral expressions (compared with scrambled and static presentations) heighten activity in visual cortex as quickly as 165 ms poststimulus onset and later (237 ms) engage fusiform gyrus, STS and premotor areas. Consistent with proposed models of biological motion representation, we suggest that visual areas predictively represent coherent facial trajectories. We show that such representations bias emotion perception of subsequent static faces, suggesting that facial movements elicit predictions that bias perception. Our findings reveal critical processes evoked in the perception of dynamic stimuli such as facial expressions, which can endow perception with temporal continuity.

Voice perception in blind persons: A functional magnetic resonance imaging study

Early blind persons have often been shown to be superior to sighted ones across a wide range of non-visual perceptual abilities, which in turn are often explained by the functionally relevant recruitment of occipital areas. While voice stimuli are known to involve voice-selective areas of the superior temporal sulcus (STS) in sighted persons, it remains unknown if the processing of vocal stimuli involves similar brain regions in blind persons, or whether it benefits from cross-modal processing. To address these questions, we used fMRI to measure cerebral responses to voice and non-voice stimuli in blind (congenital and acquired) and sighted subjects. The global comparison of all sounds vs. silence showed a different pattern of activation between blind (pooled congenital and acquired) and sighted groups, with blind subjects showing stronger activation of occipital areas but weaker activation of temporal areas centered around Heschl's gyrus. In contrast, the specific comparison of vocal vs. non-vocal sounds did not isolate activations in the occipital areas in either of the blind groups. In the congenitally blind group, however, it led to a stronger activation in the left STS, and to a lesser extent in the fusiform cortex, compared to both sighted participants and those with acquired blindness. Moreover, STS activity in congenital blind participants significantly correlated with performance in a voice discrimination task. This increased recruitment of STS areas in the blind for voice processing is in marked contrast with the usual cross-modal recruitment of occipital cortex.

Neural Representations of Faces and Body Parts in Macaque and Human Cortex: A Comparative fMRI Study

Single-cell studies in the macaque have reported selective neural responses evoked by visual presentations of faces and bodies. Consistent with these findings, functional magnetic resonance imaging studies in humans and monkeys indicate that regions in temporal cortex respond preferentially to faces and bodies. However, it is not clear how these areas correspond across the two species. Here, we directly compared category-selective areas in macaques and humans using virtually identical techniques. In the macaque, several face- and body part-selective areas were found located along the superior temporal sulcus (STS) and middle temporal gyrus (MTG). In the human, similar to previous studies, face-selective areas were found in ventral occipital and temporal cortex and an additional face-selective area was found in the anterior temporal cortex. Face-selective areas were also found in lateral temporal cortex, including the previously reported posterior STS area. Body part-selective areas were identified in the human fusiform gyrus and lateral occipitotemporal cortex. In a first experiment, both monkey and human subjects were presented with pictures of faces, body parts, foods, scenes, and man-made objects, to examine the response profiles of each category-selective area to the five stimulus types. In a second experiment, face processing was examined by presenting upright and inverted faces. By comparing the responses and spatial relationships of the areas, we propose potential correspondences across species. Adjacent and overlapping areas in the macaque anterior STS/MTG responded strongly to both faces and body parts, similar to areas in the human fusiform gyrus and posterior STS. Furthermore, face-selective areas on the ventral bank of the STS/MTG discriminated both upright and inverted faces from objects, similar to areas in the human ventral temporal cortex. Overall, our findings demonstrate commonalities and differences in the wide-scale brain organization between the two species and provide an initial step toward establishing functionally homologous category-selective areas.

Differential cross-modal effect of speech sounds on the vMMN elicited by letter versus non-letter deviants

Event Abstract Back to Event Differential cross-modal effect of speech sounds on the vMMN elicited by letter versus non-letter deviants Dries Froyen1, 2*, N. Van-Atteveldt1, 3 and L. Blomert1, 2 1 Faculty of psychology and congnitive neuroscience, Maastricht University, Netherlands 2 Maastricht Brain Imaging Center, M-BIC, Netherlands 3 College of Physicians and Surgeons, Columbia University, United States Appropriate development of letter - speech sound associations is considered crucial for reading acquisition. Brain imaging evidence indicated that heteromodal areas in superior temporal sulcus and modality-specific auditory cortex are involved in letter - speech sound processing. The role of early visual areas, however, remains unclear. In a previous auditory MMN (aMMN) study a cross-modal effect of letters on speech sound processing was observed. aMMN-amplitude to speech sounds presented simultaneously with letters was higher in comparison with aMMN amplitude to speech sounds presented in isolation, indicating early and automatic letter - speech sound integration. In the present study the visual counterpart of the aMMN, the vMMN, is used to investigate the influences of speech sounds on letter processing. Letter and non-letter deviants were infrequently presented in a train of standard letters either in isolation or simultaneously with a speech sound. As early as 150-220 ms after stimulus onset, influences of the speech sound on visual processing were observed. However, these influences were similar for letter and non-letter processing and thus not letter-specific. In a later time-window, between 240 and 350 msec, a differential effect of the speech sound on letter and non-letter processing was observed. Interestingly, the speech sound did not influence letter processing but suppressed non-letter processing. The present results support previous fMRI findings on letter - speech sound processing, in which the early visual areas were not involved when passively processing letters and speech sounds. This implies that, although letter - speech sound processing might rely on the evolutionarily older audiovisual speech processing system, both systems recruit early visual areas by means of a different mechanism. The present study furthermore provides an appropriate tool to investigate, with a high temporal resolution and non-invasively, cross-modal effects on visual processing. Conference: MMN 09 Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications, Budapest, Hungary, 4 Apr - 7 Apr, 2009. Presentation Type: Poster Presentation Topic: Poster Presentations Citation: Froyen D, Van-Atteveldt N and Blomert L (2009). Differential cross-modal effect of speech sounds on the vMMN elicited by letter versus non-letter deviants. Conference Abstract: MMN 09 Fifth Conference on Mismatch Negativity (MMN) and its Clinical and Scientific Applications. doi: 10.3389/conf.neuro.09.2009.05.091 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 25 Mar 2009; Published Online: 25 Mar 2009. * Correspondence: Dries Froyen, Faculty of psychology and congnitive neuroscience, Maastricht University, 6200 MD Maastricht, Netherlands, d.froyen@psychology.unimaas.nl Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Dries Froyen N. Van-Atteveldt L. Blomert Google Dries Froyen N. Van-Atteveldt L. Blomert Google Scholar Dries Froyen N. Van-Atteveldt L. Blomert PubMed Dries Froyen N. Van-Atteveldt L. Blomert Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Multisensory Integration: A Functional Role for Inter-Area Synchronization?

It has been suggested that synchronization of neural activity in distinct areas of the brain is important in the 'perceptual binding' of the various features relating to a specific object. A recent study has provided new evidence that inter-area synchronization is important in multisensory integration.

Integration of Bimodal Looming Signals through Neuronal Coherence in the Temporal Lobe

The ability to integrate information across multiple sensory systems offers several behavioral advantages, from quicker reaction times and more accurate responses to better detection and more robust learning. At the neural level, multisensory integration requires large-scale interactions between different brain regions--the convergence of information from separate sensory modalities, represented by distinct neuronal populations. The interactions between these neuronal populations must be fast and flexible, so that behaviorally relevant signals belonging to the same object or event can be immediately integrated and integration of unrelated signals can be prevented. Looming signals are a particular class of signals that are behaviorally relevant for animals and that occur in both the auditory and visual domain. These signals indicate the rapid approach of objects and provide highly salient warning cues about impending impact. We show here that multisensory integration of auditory and visual looming signals may be mediated by functional interactions between auditory cortex and the superior temporal sulcus, two areas involved in integrating behaviorally relevant auditory-visual signals. Audiovisual looming signals elicited increased gamma-band coherence between these areas, relative to unimodal or receding-motion signals. This suggests that the neocortex uses fast, flexible intercortical interactions to mediate multisensory integration.

Differential neural responses to humans vs. robots: An event-related potential study

Do we perceive humanoid robots as human beings? Recent neuroimaging studies have reported similarity in the neural processing of human and robot actions in the superior temporal sulcus area but a differential neural response in the premotor area. These studies suggest that the neural activity of the occipitotemporal region would not be affected by appearance information. Unlike those studies, in this study, by using the inversion effect as an index, we demonstrated for the first time that the appearance information of a presented action affects neural responses in the occipitotemporal region. In event-related potential (ERP) studies, the inversion effect is the phenomenon whereby an upright face- and body-sensitive ERP component in the occipitotemporal region is enhanced and delayed up to 200 ms in response to an inverted face and body, but not to an inverted object. We used three kinds of walking animation with different appearance information (human, robot, and point-light) as well as inverted stimuli of each appearance. The anatomical structure and walking speed of the presented stimuli were all identical. The results showed that the inversion effect occurred in the right occipitotemporal region only in response to human appearance, and not robotic and point-light appearances. That is, the amplitude of the inverted condition of human appearance was significantly larger than that of the upright condition only. Our results, which are contrary to other recent neuroimaging studies, suggested that appearance information affects the neural response in the occipitotemporal region.