The functional anatomy of visual-tactile integration in man: a study using positron emission tomography

Alterations of tactile and anatomical spatial representations of the hand after stroke

Stroke often causes long-term motor and somatosensory impairments. Motor planning and tactile perception rely on spatial body representations. However, the link between altered spatial body representations, motor deficit and tactile spatial coding remains unclear. This study investigates the relationship between motor deficits and alterations of anatomical (body) and tactile spatial representations of the hand in 20 post-stroke patients with upper limb hemiparesis. Anatomical and tactile spatial representations were assessed from 10 targets (nails and knuckles) respectively cued verbally by their anatomical name or using tactile stimulations. Two distance metrics (hand width and finger length) and two structural measures (relative organization of targets positions and angular deviation of fingers from their physical posture) were computed and compared to clinical assessments, normative data and lesions sites. Over half of the patients had altered anatomical and/or tactile spatial representations. Metrics of tactile and anatomical representations showed common variations, where a wider hand representation was linked to more severe motor deficits. In contrast, alterations in structural measures were not concomitantly observed in tactile and anatomical representations and did not correlate with clinical assessments. Finally, a preliminary analysis showed that specific alterations in tactile structural measures were associated with dorsolateral prefrontal stroke lesions. This study reveals shared and distinct characteristics of anatomical and tactile hand spatial representations, reflecting different mechanisms that can be affected differently after stroke: metrics and location of tactile and anatomical representations were partially shared while the structural measures of tactile and anatomical representations had distinct characteristics.

The functional connectivity of the human claustrum, according to the Human Connectome Project database

The claustrum is an irregular and fine sheet of grey matter in the basolateral telencephalon present in almost all mammals. The claustrum has been the object of several studies using animal models and, more recently, in human beings using neuroimaging. One of the most extended cognitive processes attributed to the claustrum is the salience process, which is also related to the insular cortex. In the same way, studies with human subjects and functional magnetic resonance imaging have reported the coactivation of the claustrum/insular cortex in the integration of sensory signals. This coactivation has been reported in the left claustrum/insular cortex or in the right claustrum/insular cortex. The asymmetry has been reported in task studies and literature related to neurological disorders such as Alzheimer's disease and schizophrenia, relating the severity of delusions with the reduction in left claustral volume. We present a functional connectivity study of the claustrum. Resting-state functional and anatomical MRI data from 100 healthy subjects were analyzed; taken from the Human Connectome Project (HCP, NIH Blueprint: The Human Connectome Project), with 2x2x2 mm3 voxel resolution. We hypothesize that 1) the claustrum is a node involved in different brain networks, 2) the functional connectivity pattern of the claustrum is different from the insular cortex's pattern, and 3) the asymmetry is present in the claustrum's functional connectivity. Our findings include at least three brain networks related to the claustrum. We found functional connectivity between the claustrum, frontoparietal network, and the default mode network as a distinctive attribute. The functional connectivity between the right claustrum with the frontoparietal network and the dorsal attention network supports the hypothesis of claustral asymmetry. These findings provide functional evidence, suggesting that the claustrum is coupled with the frontoparietal network serving together to instantiate new task states by flexibly modulating and interacting with other control and processing networks.

fNIRS a novel neuroimaging tool to investigate olfaction, olfactory imagery, and crossmodal interactions: a systematic review

Olfaction is understudied in neuroimaging research compared to other senses, but there is growing evidence of its therapeutic benefits on mood and well-being. Olfactory imagery can provide similar health benefits as olfactory interventions. Harnessing crossmodal visual-olfactory interactions can facilitate olfactory imagery. Understanding and employing these cross-modal interactions between visual and olfactory stimuli could aid in the research and applications of olfaction and olfactory imagery interventions for health and wellbeing. This review examines current knowledge, debates, and research on olfaction, olfactive imagery, and crossmodal visual-olfactory integration. A total of 56 papers, identified using the PRISMA method, were evaluated to identify key brain regions, research themes and methods used to determine the suitability of fNIRS as a tool for studying these topics. The review identified fNIRS-compatible protocols and brain regions within the fNIRS recording depth of approximately 1.5 cm associated with olfactory imagery and crossmodal visual-olfactory integration. Commonly cited regions include the orbitofrontal cortex, inferior frontal gyrus and dorsolateral prefrontal cortex. The findings of this review indicate that fNIRS would be a suitable tool for research into these processes. Additionally, fNIRS suitability for use in naturalistic settings may lead to the development of new research approaches with greater ecological validity compared to existing neuroimaging techniques.

Congruent aero-tactile stimuli bias perception of voicing continua

Multimodal integration is the formation of a coherent percept from different sensory inputs such as vision, audition, and somatosensation. Most research on multimodal integration in speech perception has focused on audio-visual integration. In recent years, audio-tactile integration has also been investigated, and it has been established that puffs of air applied to the skin and timed with listening tasks shift the perception of voicing by naive listeners. The current study has replicated and extended these findings by testing the effect of air puffs on gradations of voice onset time along a continuum rather than the voiced and voiceless endpoints of the original work. Three continua were tested: bilabial (“pa/ba”), velar (“ka/ga”), and a vowel continuum (“head/hid”) used as a control. The presence of air puffs was found to significantly increase the likelihood of choosing voiceless responses for the two VOT continua but had no effect on choices for the vowel continuum. Analysis of response times revealed that the presence of air puffs lengthened responses for intermediate (ambiguous) stimuli and shortened them for endpoint (non-ambiguous) stimuli. The slowest response times were observed for the intermediate steps for all three continua, but for the bilabial continuum this effect interacted with the presence of air puffs: responses were slower in the presence of air puffs, and faster in their absence. This suggests that during integration auditory and aero-tactile inputs are weighted differently by the perceptual system, with the latter exerting greater influence in those cases where the auditory cues for voicing are ambiguous.

Long term food stability for extended space missions: a review

At present, human spaceflight is confined to low Earth orbit but, in future, will again go to the Moon and, beyond, to Mars. The provision of food during these extended missions will need to meet the special nutritional and psychosocial needs of the crew. Terrestrially grown and processed food products, currently provided for consumption by astronauts/cosmonauts, have not yet been systematically optimised to maintain their nutritional integrity and reach the shelf-life necessary for extended space voyages. Notably, space food provisions for Mars exploration will be subject to extended exposure to galactic cosmic radiation and solar particle events, the impact of which is not fully understood. In this review, we provide a summary of the existing knowledge about current space food products, the impact of radiation and storage on food composition, the identification of radiolytic biomarkers and identify gaps in our knowledge that are specific in relation to the effect of the cosmic radiation on food in space.

Trait Empathy Shapes Neural Responses Toward Sad Music

Individuals with a predisposition to empathize engage with sad music in a compelling way, experiencing overall more pleasurable emotions. However, the neural mechanisms underlying these music-related experiences in empathic individuals are unknown. The present study tested whether dispositional empathy modulates neural responses to sad compared with happy music. Twenty-four participants underwent fMRI while listening to 4-min blocks of music evoking sadness or happiness. Using voxel-wise regression, we found a positive correlation between trait empathy (with scores assessed by the Interpersonal Reactivity Index) and eigenvector centrality values in the ventromedial prefrontal cortex (vmPFC), including the medial orbitofrontal cortex (mOFC). We then performed a functional connectivity (FC) analysis to detect network nodes showing stronger FC with the vmPFC/mOFC during the presentation of sad versus happy music. By doing so, we identified a "music-empathy" network (vmPFC/mOFC, dorsomedial prefrontal cortex, primary visual cortex, bilateral claustrum and putamen, and cerebellum) that is spontaneously recruited while listening to sad music and includes brain regions that support the coding of compassion, mentalizing, and visual mental imagery. Importantly, our findings extend the current understanding of empathic behaviors to the musical domain and pinpoint sad music as an effective stimulus to be employed in social neuroscience research.

Increased visual bias in children with developmental coordination disorder: Evidence from a visual-tactile temporal order judgment task

BACKGROUND

Previous studies have suggested that children with developmental coordination disorder (DCD) rely heavily on vision to perform movements, which may contribute to their clumsy movements. However, few studies have objectively and quantitatively investigated the perceptual biases of children with DCD.

METHODS

A visual-tactile temporal order judgment (TOJ) task was used to measure and compare the perceptual biases of 19 children with DCD and 19 age- and sex-matched typically developing children. The point of subjective equality, which demonstrates when "visual first" and "tactile first" judgment probabilities are equal (50%), obtained by analyzing the results of the visual-tactile TOJ task, was used as an indicator of perceptual biases. Further, variables (age and manual dexterity in all participants; motor function, autism spectrum disorder and attention-deficit hyperactivity disorder traits, and depressive symptoms in children with DCD) associated with perceptual biases were examined with correlation analysis.

RESULTS

Children with DCD had significantly stronger visual bias than typically developing children. Overall correlation analysis showed that increased visual bias was significantly correlated with poor manual dexterity.

CONCLUSION

Children with DCD had a strong visual bias, which was associated with poor manual dexterity.

Children's neural activity during number line estimations assessed by functional near-infrared spectroscopy (fNIRS)

Number line estimation (NLE) is an educational task in which children estimate the location of a value (e.g., 25) on a blank line that represents a numerical range (e.g., 0-100). NLE performance is a strong predictor of success in mathematics, and error patterns on this task help provide a glimpse into how children may represent number internally. However, a missing and fundamental element of this puzzle is the identification of neural correlates of NLE in children. That is, understanding possible neural signatures related to NLE performance will provide valuable insight into the cognitive processes that underlie children's development of NLE ability. Using functional near-infrared spectroscopy (fNIRS), we provide the first investigation of concurrent behavioral and cortical signatures of NLE performance in children. Specifically, our results highlight significant fronto-parietal changes in cortical activation in response to increases in NLE scale (e.g., 0-100 vs. 0-100,000). Furthermore, our results demonstrate that NLE performance feedback (auditory, visual, or audiovisual), as well as children's grade (2nd vs. 3rd) influence cortical responding during an NLE task.

Shared neural representations of tactile roughness intensities by somatosensation and touch observation using an associative learning method

Previous human fMRI studies have reported activation of somatosensory areas not only during actual touch, but also during touch observation. However, it has remained unclear how the brain encodes visually evoked tactile intensities. Using an associative learning method, we investigated neural representations of roughness intensities evoked by (a) tactile explorations and (b) visual observation of tactile explorations. Moreover, we explored (c) modality-independent neural representations of roughness intensities using a cross-modal classification method. Case (a) showed significant decoding performance in the anterior cingulate cortex (ACC) and the supramarginal gyrus (SMG), while in the case (b), the bilateral posterior parietal cortices, the inferior occipital gyrus, and the primary motor cortex were identified. Case (c) observed shared neural activity patterns in the bilateral insula, the SMG, and the ACC. Interestingly, the insular cortices were identified only from the cross-modal classification, suggesting their potential role in modality-independent tactile processing. We further examined correlations of confusion patterns between behavioral and neural similarity matrices for each region. Significant correlations were found solely in the SMG, reflecting a close relationship between neural activities of SMG and roughness intensity perception. The present findings may deepen our understanding of the brain mechanisms underlying intensity perception of tactile roughness.

Multisensory integration processing during olfactory-visual stimulation-An fMRI graph theoretical network analysis

In this study, we aimed to understand how whole-brain neural networks compute sensory information integration based on the olfactory and visual system. Task-related functional magnetic resonance imaging (fMRI) data was obtained during unimodal and bimodal sensory stimulation. Based on the identification of multisensory integration processing (MIP) specific hub-like network nodes analyzed with network-based statistics using region-of-interest based connectivity matrices, we conclude the following brain areas to be important for processing the presented bimodal sensory information: right precuneus connected contralaterally to the supramarginal gyrus for memory-related imagery and phonology retrieval, and the left middle occipital gyrus connected ipsilaterally to the inferior frontal gyrus via the inferior fronto-occipital fasciculus including functional aspects of working memory. Applied graph theory for quantification of the resulting complex network topologies indicates a significantly increased global efficiency and clustering coefficient in networks including aspects of MIP reflecting a simultaneous better integration and segregation. Graph theoretical analysis of positive and negative network correlations allowing for inferences about excitatory and inhibitory network architectures revealed-not significant, but very consistent-that MIP-specific neural networks are dominated by inhibitory relationships between brain regions involved in stimulus processing.

Clinical response to Vim's thalamic stereotactic radiosurgery for essential tremor is associated with distinctive functional connectivity patterns

INTRODUCTION

Essential tremor (ET) is the most common movement disorder. Drug-resistant ET can benefit from standard surgical stereotactic procedures (deep brain stimulation, thalamotomy) or minimally invasive high-intensity focused ultrasound (HIFU) or stereotactic radiosurgical thalamotomy (SRS-T). Resting-state fMRI (rs-fMRI) is a non-invasive imaging method acquired in absence of a task. We examined whether rs-fMRI correlates with tremor score on the treated hand (TSTH) improvement 1 year after SRS-T.

METHODS

We included 17 consecutive patients treated with left unilateral SRS-T in Marseille, France. Tremor score evaluation and rs-fMRI were acquired at baseline and 1 year after SRS-T. Resting-state data (34 scans) were analyzed without a priori hypothesis, in Lausanne, Switzerland. Based on degree of improvement in TSTH, to consider SRS-T at least as effective as medication, we separated two groups: 1, ≤ 50% (n = 6, 35.3%); 2, > 50% (n = 11, 64.7%). They did not differ statistically by age (p = 0.86), duration of symptoms (p = 0.41), or lesion volume at 1 year (p = 0.06).

RESULTS

We report TSTH improvement correlated with interconnectivity strength between salience network with the left claustrum and putamen, as well as between bilateral motor cortices, frontal eye fields and left cerebellum lobule VI with right visual association area (the former also with lesion volume). Longitudinal changes showed additional associations in interconnectivity strength between right dorsal attention network with ventro-lateral prefrontal cortex and a reminiscent salience network with fusiform gyrus.

CONCLUSIONS

Brain connectivity measured by resting-state fMRI relates to clinical response after SRS-T. Relevant networks are visual, motor, and attention. Interconnectivity between visual and motor areas is a novel finding, revealing implication in movement sensory guidance.

Fabrication of cerebral aneurysm simulator with a desktop 3D printer

Now, more and more patients are suffering cerebral aneurysm. However, long training time limits the rapid growth of cerebrovascular neurosurgeons. Here we developed a novel cerebral aneurysm simulator which can be better represented the dynamic bulging process of cerebral aneurysm The proposed simulator features the integration of a hollow elastic vascular model, a skull model and a brain model, which can be affordably fabricated at the clinic (Fab@Clinic), under $25.00 each with the help of a low-cost desktop 3D printer. Moreover, the clinical blood flow and pulsation pressure similar to the human can be well simulated, which can be used to train the neurosurgical residents how to clip aneurysms more effectively.

A role for the anterior insular cortex in the global neuronal workspace model of consciousness

According to the global neuronal workspace model of consciousness, consciousness results from the global broadcast of information throughout the brain. The global neuronal workspace is mainly constituted by a fronto-parietal network. The anterior insular cortex is part of this global neuronal workspace, but the function of this region has not yet been defined within the global neuronal workspace model of consciousness. In this review, I hypothesize that the anterior insular cortex implements a cross-modal priority map, the function of which is to determine priorities for the processing of information and subsequent entrance in the global neuronal workspace.

Human Brain Activity Related to the Tactile Perception of Stickiness

While the perception of stickiness serves as one of the fundamental dimensions for tactile sensation, little has been elucidated about the stickiness sensation and its neural correlates. The present study investigated how the human brain responds to perceived tactile sticky stimuli using functional magnetic resonance imaging (fMRI). To evoke tactile perception of stickiness with multiple intensities, we generated silicone stimuli with varying catalyst ratios. Also, an acrylic sham stimulus was prepared to present a condition with no sticky sensation. From the two psychophysics experiments-the methods of constant stimuli and the magnitude estimation-we could classify the silicone stimuli into two groups according to whether a sticky perception was evoked: the Supra-threshold group that evoked sticky perception and the Infra-threshold group that did not. In the Supra-threshold vs. Sham contrast analysis of the fMRI data using the general linear model (GLM), the contralateral primary somatosensory area (S1) and ipsilateral dorsolateral prefrontal cortex (DLPFC) showed significant activations in subjects, whereas no significant result was found in the Infra-threshold vs. Sham contrast. This result indicates that the perception of stickiness not only activates the somatosensory cortex, but also possibly induces higher cognitive processes. Also, the Supra- vs. Infra-threshold contrast analysis revealed significant activations in several subcortical regions, including the pallidum, putamen, caudate and thalamus, as well as in another region spanning the insula and temporal cortices. These brain regions, previously known to be related to tactile discrimination, may subserve the discrimination of different intensities of tactile stickiness. The present study unveils the human neural correlates of the tactile perception of stickiness and may contribute to broadening the understanding of neural mechanisms associated with tactile perception.

Functional gains in energy and cell metabolism after TSPO gene insertion

Recent loss-of-function studies in tissue-specific as well as global Tspo (Translocator Protein 18 kDa) knockout mice have not confirmed its long assumed indispensability for the translocation of cholesterol across the mitochondrial inter-membrane space, a rate-limiting step in steroid biosynthesis. Instead, recent studies in global Tspo knockout mice indicate that TSPO may play a more fundamental role in cellular bioenergetics, which may include the indirect down-stream regulation of transport or metabolic functions. To examine whether overexpression of the TSPO protein alters the cellular bioenergetic profile, Jurkat cells with low to absent endogenous expression were transfected with a TSPO construct to create a stable cell line with de novo expression of exogenous TSPO protein. Expression of TSPO was confirmed by RT-qPCR, radioligand binding with [3H]PK11195 and immunocytochemistry with a TSPO antibody. We demonstrate that TSPO gene insertion causes increased transcription of genes involved in the mitochondrial electron transport chain. Furthermore, TSPO insertion increased mitochondrial ATP production as well as cell excitability, reflected in a decrease in patch clamp recorded rectified K channel currents. These functional changes were accompanied by an increase in cell proliferation and motility, which were inhibited by PK11195, a selective ligand for TSPO. We suggest that TSPO may serve a range of functions that can be viewed as downstream regulatory effects of its primary, evolutionary conserved role in cell metabolism and energy production.

Effects of visual information regarding tactile stimulation on the somatosensory cortical activation: a functional MRI study

Many studies have investigated the evidence for tactile and visual interactive responses to activation of various brain regions. However, few studies have reported on the effects of visuo-tactile multisensory integration on the amount of brain activation on the somatosensory cortical regions. The aim of this study was to examine whether coincidental information obtained by tactile stimulation can affect the somatosensory cortical activation using functional MRI. Ten right-handed healthy subjects were recruited for this study. Two tasks (tactile stimulation and visuotactile stimulation) were performed using a block paradigm during fMRI scanning. In the tactile stimulation task, in subjects with eyes closed, tactile stimulation was applied on the dorsum of the right hand, corresponding to the proximal to distal directions, using a rubber brush. In the visuotactile stimulation task, tactile stimulation was applied to observe the attached mirror in the MRI chamber reflecting their hands being touched with the brush. In the result of SPM group analysis, we found brain activation on the somatosensory cortical area. Tactile stimulation task induced brain activations in the left primary sensory-motor cortex (SM1) and secondary somatosensory cortex (S2). In the visuo-tactile stimulation task, brain activations were observed in the both SM1, both S2, and right posterior parietal cortex. In all tasks, the peak activation was detected in the contralateral SM1. We examined the effects of visuo-tactile multisensory integration on the SM1 and found that visual information during tactile stimulation could enhance activations on SM1 compared to the tactile unisensory stimulation.

Multisensory Processing in Sensory-Specific Cortical Areas

The anatomical organization of the brain is such that incoming signals from different sensory modalities are initially processed in anatomically separate regions of the cortex. When these signals originate from a single event or object in the external world, it is essential that the inputs are integrated to form a coherent representation of the multisensory event. This review discusses recent data indicating that the integration of multisensory signals relies not only on anatomical convergence from sensory-specific cortices to multi-sensory brain areas but also on reciprocal influences between cortical regions that are traditionally considered as sensory-specific. These findings highlight integration mechanisms that go beyond traditional models based on a hierarchical convergence of sensory processing.

Synaptic Organization of the Neuronal Circuits of the Claustrum

The claustrum, a poorly understood subcortical structure located between the cortex and the striatum, forms widespread connections with almost all cortical areas, but the cellular organization of claustral circuits remains largely unknown. Based primarily on anatomical data, it has been proposed that the claustrum integrates activity across sensory modalities. However, the extent to which the synaptic organization of claustral circuits supports this integration is unclear. Here, we used paired whole-cell recordings and optogenetic approaches in mouse brain slices to determine the cellular organization of the claustrum. We found that unitary synaptic connections among claustrocortical (ClaC) neurons were rare. In contrast, parvalbumin-positive (PV) inhibitory interneurons were highly interconnected with both chemical and electrical synapses. In addition, ClaC neurons and PV interneurons formed frequent synaptic connections. As suggested by anatomical data, we found that corticoclaustral afferents formed monosynaptic connections onto both ClaC neurons and PV interneurons. However, the responses to cortical input were comparatively stronger in PV interneurons. Consistent with this overall circuit organization, activation of corticoclaustral afferents generated monosynaptic excitatory responses as well as disynaptic inhibitory responses in ClaC neurons. These data indicate that recurrent excitatory circuits within the claustrum alone are unlikely to integrate across multiple sensory modalities. Rather, this cellular organization is typical of circuits sensitive to correlated inputs. Although single ClaC neurons may integrate corticoclaustral input from different cortical regions, these results are consistent with more recent proposals implicating the claustrum in detecting sensory novelty or in amplifying correlated cortical inputs to coordinate the activity of functionally related cortical regions. Significance statement: The function of the claustrum, a brain nucleus found in mammals, remains poorly understood. It has been proposed, based primarily on anatomical data, that claustral circuits play an integrative role and contribute to multimodal sensory integration. Here we show that the principal neurons of the claustrum, claustrocortical (ClaC) projection neurons, rarely form synaptic connections with one another and are unlikely to contribute to broad integration within the claustrum. We show that, although single ClaC neurons may integrate corticoclaustral inputs carrying information for different sensory modalities, the synaptic organization of ClaC neurons, local parvalbumin-positive interneurons within the claustrum, and cortical afferents is also consistent with recent proposals that the claustrum plays a role in detecting salient stimuli or amplifying correlated cortical inputs.

The Tactile Dimensions of Abstract Paintings: A Cross-Modal Study

In our research, we tested for the existence of cross-modal visual and tactile associations in the experience of abstract art. Specifically, we measured the association of 60 abstract paintings with four couples of antonyms related to texture, such as warm or cold, smooth or rough, lightweight or heavy, soft or hard, investigating if the different modality of presentation on a computer screen (color versions: natural colors, inverted colors, black and white) gave rise to different associations relative to the four couples of opponent qualities. Second, we tested whether there might be differences between the ratings of the paintings when they were presented as images on a computer screen versus in real life at the museum. The results confirmed that associations between visual and tactile experience with such complex stimuli exist. In the case of the couple warm or cold, a significant inversion of associated qualities occurs when the images are presented in inverted colors as opposed to natural colors; furthermore, when presented in black and white, warm evaluations are "cooled down," but cold evaluations remain the same. The degree of smoothness could be considered not associated with the color versions. When seen in black and white, both the mean softness and the mean lightweight-ness of the paintings were reduced; however, in the last case, this effect was more evident for the most lightweight pictures. There is only a slight difference between the two presentations of the paintings as images presented on a computer screen and seen in real life, relative to the warm or cold and soft or hard dimensions. Of the four opponent qualities, the three pairs warm or cold, lightweight or heavy, and soft or hard showed the most interesting results in relation to the cross-modal associations.

White matter correlates of sensory processing in autism spectrum disorders

Autism spectrum disorder (ASD) has been characterized by atypical socio-communicative behavior, sensorimotor impairment and abnormal neurodevelopmental trajectories. DTI has been used to determine the presence and nature of abnormality in white matter integrity that may contribute to the behavioral phenomena that characterize ASD. Although atypical patterns of sensory responding in ASD are well documented in the behavioral literature, much less is known about the neural networks associated with aberrant sensory processing. To address the roles of basic sensory, sensory association and early attentional processes in sensory responsiveness in ASD, our investigation focused on five white matter fiber tracts known to be involved in these various stages of sensory processing: superior corona radiata, centrum semiovale, inferior longitudinal fasciculus, posterior limb of the internal capsule, and splenium. We acquired high angular resolution diffusion images from 32 children with ASD and 26 typically developing children between the ages of 5 and 8. We also administered sensory assessments to examine brain-behavior relationships between white matter integrity and sensory variables. Our findings suggest a modulatory role of the inferior longitudinal fasciculus and splenium in atypical sensorimotor and early attention processes in ASD. Increased tactile defensiveness was found to be related to reduced fractional anisotropy in the inferior longitudinal fasciculus, which may reflect an aberrant connection between limbic structures in the temporal lobe and the inferior parietal cortex. Our findings also corroborate the modulatory role of the splenium in attentional orienting, but suggest the possibility of a more diffuse or separable network for social orienting in ASD. Future investigation should consider the use of whole brain analyses for a more robust assessment of white matter microstructure.

NIH workshop on clinical translation of molecular imaging probes and technology--meeting report

A workshop on "Clinical Translation of Molecular Imaging Probes and Technology" was held August 2, 2013 in Bethesda, Maryland, organized and supported by the National Institute of Biomedical Imaging and Bioengineering (NIBIB). This workshop brought together researchers, clinicians, representatives from pharmaceutical companies, molecular probe developers, and regulatory science experts. Attendees met to talk over current challenges in the discovery, validation, and translation of molecular imaging (MI) probes for key clinical applications. Participants also discussed potential strategies to address these challenges. The workshop consisted of 4 sessions, with 14 presentations and 2 panel discussions. Topics of discussion included (1) challenges and opportunities for clinical research and patient care, (2) advances in molecular probe design, (3) current approaches used by industry and pharmaceutical companies, and (4) clinical translation of MI probes. In the presentations and discussions, there were general agreement that while the barriers for validation and translation of MI probes remain high, there are pressing clinical needs and development opportunities for targets in cardiovascular, cancer, endocrine, neurological, and inflammatory diseases. The strengths of different imaging modalities, and the synergy of multimodality imaging, were highlighted. Participants also underscored the continuing need for close interactions and collaborations between academic and industrial partners, and federal agencies in the imaging probe development process.

A role of the claustrum in auditory scene analysis by reflecting sensory change

The biological function of the claustrum remains speculative, despite many years of research. On the basis of its widespread connections it is often hypothesized that the claustrum may have an integrative function mainly reflecting objects rather than the details of sensory stimuli. Given the absence of a clear demonstration of any sensory integration in claustral neurons, however, we propose an alternative, data-driven, hypothesis: namely that the claustrum detects the occurrence of novel or salient sensory events. The detection of new events is critical for behavior and survival, as suddenly appearing objects may require rapid and coordinated reactions. Sounds are of particular relevance in this regard, and our conclusions are based on the analysis of neurons in the auditory zone of the primate claustrum. Specifically, we studied the responses to natural sounds, their preference to various sound categories, and to changes in the auditory scene. In a test for sound-category preference claustral neurons responded to but displayed a clear lack of selectivity between monkey vocalizations, other animal vocalizations or environmental sounds (Esnd). Claustral neurons were however able to detect target sounds embedded in a noisy background and their responses scaled with target signal to noise ratio (SNR). The single trial responses of individual neurons suggest that these neurons detected and reflected the occurrence of a change in the auditory scene. Given its widespread connectivity with sensory, motor and limbic structures the claustrum could play the essential role of identifying the occurrence of important sensory changes and notifying other brain areas-hence contributing to sensory awareness.

Intracranial cortical responses during visual-tactile integration in humans

Sensory integration of touch and sight is crucial to perceiving and navigating the environment. While recent evidence from other sensory modality combinations suggests that low-level sensory areas integrate multisensory information at early processing stages, little is known about how the brain combines visual and tactile information. We investigated the dynamics of multisensory integration between vision and touch using the high spatial and temporal resolution of intracranial electrocorticography in humans. We present a novel, two-step metric for defining multisensory integration. The first step compares the sum of the unisensory responses to the bimodal response as multisensory responses. The second step eliminates the possibility that double addition of sensory responses could be misinterpreted as interactions. Using these criteria, averaged local field potentials and high-gamma-band power demonstrate a functional processing cascade whereby sensory integration occurs late, both anatomically and temporally, in the temporo-parieto-occipital junction (TPOJ) and dorsolateral prefrontal cortex. Results further suggest two neurophysiologically distinct and temporally separated integration mechanisms in TPOJ, while providing direct evidence for local suppression as a dominant mechanism for synthesizing visual and tactile input. These results tend to support earlier concepts of multisensory integration as relatively late and centered in tertiary multimodal association cortices.

Dysgranular retrosplenial cortex lesions in rats disrupt cross-modal object recognition

The retrosplenial cortex supports navigation, with one role thought to be the integration of different spatial cue types. This hypothesis was extended by examining the integration of nonspatial cues. Rats with lesions in either the dysgranular subregion of retrosplenial cortex (area 30) or lesions in both the granular and dysgranular subregions (areas 29 and 30) were tested on cross-modal object recognition (Experiment 1). In these tests, rats used different sensory modalities when exploring and subsequently recognizing the same test objects. The objects were first presented either in the dark, i.e., giving tactile and olfactory cues, or in the light behind a clear Perspex barrier, i.e., giving visual cues. Animals were then tested with either constant combinations of sample and test conditions (light to light, dark to dark), or changed “cross-modal” combinations (light to dark, dark to light). In Experiment 2, visual object recognition was tested without Perspex barriers, but using objects that could not be distinguished in the dark. The dysgranular retrosplenial cortex lesions selectively impaired cross-modal recognition when cue conditions switched from dark to light between initial sampling and subsequent object recognition, but no impairment was seen when the cue conditions remained constant, whether dark or light. The combined (areas 29 and 30) lesioned rats also failed the dark to light cross-modal problem but this impairment was less selective. The present findings suggest a role for the dysgranular retrosplenial cortex in mediating the integration of information across multiple cue types, a role that potentially applies to both spatial and nonspatial domains.

Haptic shape processing in visual cortex

Humans typically rely upon vision to identify object shape, but we can also recognize shape via touch (haptics). Our haptic shape recognition ability raises an intriguing question: To what extent do visual cortical shape recognition mechanisms support haptic object recognition? We addressed this question using a haptic fMRI repetition design, which allowed us to identify neuronal populations sensitive to the shape of objects that were touched but not seen. In addition to the expected shape-selective fMRI responses in dorsal frontoparietal areas, we observed widespread shape-selective responses in the ventral visual cortical pathway, including primary visual cortex. Our results indicate that shape processing via touch engages many of the same neural mechanisms as visual object recognition. The shape-specific repetition effects we observed in primary visual cortex show that visual sensory areas are engaged during the haptic exploration of object shape, even in the absence of concurrent shape-related visual input. Our results complement related findings in visually deprived individuals and highlight the fundamental role of the visual system in the processing of object shape.

Natural stimuli from three coherent modalities enhance behavioral responses and electrophysiological cortical activity in humans

Cues that involve a number of sensory modalities are processed in the brain in an interactive multimodal manner rather than independently for each modality. We studied multimodal integration in a natural, yet fully controlled scene, implemented as an interactive game in an auditory-haptic-visual virtual environment. In this imitation of a natural scene, the targets of perception were ecologically valid uni-, bi- and tri-modal manifestations of a simple event-a ball hitting a wall. Subjects were engaged in the game while their behavioral and early cortical electrophysiological responses were measured. Behavioral results confirmed that tri-modal cues were detected faster and more accurately than bi-modal cues, which, likewise, showed advantages over unimodal responses. Event-Related Potentials (ERPs) were recorded, and the first 200 ms following stimulus onset was analyzed to reveal the latencies of cortical multimodal interactions as estimated by sLORETA. These electrophysiological findings indicated bi-modal as well as tri-modal interactions beginning very early (~30 ms), uniquely for each multimodal combination. The results suggest that early cortical multimodal integration accelerates cortical activity and, in turn, enhances performance measures. This acceleration registers on the scalp as sub-additive cortical activation.

Development of three-dimensional hollow elastic model for cerebral aneurysm clipping simulation enabling rapid and low cost prototyping

OBJECTIVE

We developed a method for fabricating a three-dimensional hollow and elastic aneurysm model useful for surgical simulation and surgical training. In this article, we explain the hollow elastic model prototyping method and report on the effects of applying it to presurgical simulation and surgical training.

METHODS

A three-dimensional printer using acrylonitrile-butadiene-styrene as a modeling material was used to produce a vessel model. The prototype was then coated with liquid silicone. After the silicone had hardened, the acrylonitrile-butadiene-styrene was melted with xylene and removed, leaving an outer layer as a hollow elastic model.

RESULTS

Simulations using the hollow elastic model were performed in 12 patients. In all patients, the clipping proceeded as scheduled. The surgeon's postoperative assessment was favorable in all cases. This method enables easy fabrication at low cost.

CONCLUSION

Simulation using the hollow elastic model is thought to be useful for understanding of three-dimensional aneurysm structure.

The functional neuroanatomy of multitasking: combining dual tasking with a short term memory task

Insight into the neural architecture of multitasking is crucial when investigating the pathophysiology of multitasking deficits in clinical populations. Presently, little is known about how the brain combines dual-tasking with a concurrent short-term memory task, despite the relevance of this mental operation in daily life and the frequency of complaints related to this process, in disease. In this study we aimed to examine how the brain responds when a memory task is added to dual-tasking. Thirty-three right-handed healthy volunteers (20 females, mean age 39.9 ± 5.8) were examined with functional brain imaging (fMRI). The paradigm consisted of two cross-modal single tasks (a visual and auditory temporal same-different task with short delay), a dual-task combining both single tasks simultaneously and a multi-task condition, combining the dual-task with an additional short-term memory task (temporal same-different visual task with long delay). Dual-tasking compared to both individual visual and auditory single tasks activated a predominantly right-sided fronto-parietal network and the cerebellum. When adding the additional short-term memory task, a larger and more bilateral frontoparietal network was recruited. We found enhanced activity during multitasking in components of the network that were already involved in dual-tasking, suggesting increased working memory demands, as well as recruitment of multitask-specific components including areas that are likely to be involved in online holding of visual stimuli in short-term memory such as occipito-temporal cortex. These results confirm concurrent neural processing of a visual short-term memory task during dual-tasking and provide evidence for an effective fMRI multitasking paradigm.

Motor skill learning in children with Developmental Coordination Disorder

Children with Developmental Coordination Disorder (DCD) are characterized as having motor difficulties and learning impairment that may last well into adolescence and adulthood. Although behavioral deficits have been identified in many domains such as visuo-spatial processing, kinesthetic perception, and cross-modal sensory integration, recent studies suggested that the functional impairment of certain brain areas, such as cerebellum and basal ganglia, are the underlying causes of DCD. This review focuses on the "motor learning deficits" in DCD and their possible neural correlates. It presents recent evidence from both behavioral and neuroimaging studies and discusses dominant neural hypotheses in DCD. Given the heterogeneity of this disorder, a successful intervention program should target the specific deficits on an individual basis. Future neuroimaging studies are critical steps in enhancing our understanding of learning deficits in DCD.

Multimodal interactions in typically and atypically developing children: natural versus artificial environments

This review addresses the central role played by multimodal interactions in neurocognitive development. We first analyzed our studies of multimodal verbal and nonverbal cognition and emotional interactions within neuronal, that is, natural environments in typically developing children. We then tried to relate them to the topic of creating artificial environments using mobile toy robots to neurorehabilitate severely autistic children. By doing so, both neural/natural and artificial environments are considered as the basis of neuronal organization and reorganization. The common thread underlying the thinking behind this approach revolves around the brain's intrinsic properties: neuroplasticity and the fact that the brain is neurodynamic. In our approach, neural organization and reorganization using natural or artificial environments aspires to bring computational perspectives into cognitive developmental neuroscience.

Anatomical and functional enhancements of the insula after loss of large primary somatosensory fibers

Brain changes associated with the loss of a sensory modality such as vision and audition have previously been reported. Here, we examined the effect of loss of discriminative touch and proprioception on cortical thickness and functional connectivity. We performed structural magnetic resonance imaging and resting-state functional magnetic resonance imaging scans on a 60-year-old female who at age 31 suffered a selective loss of large-diameter myelinated primary afferents and, therefore, relies mainly on her intact thin-fiber senses (temperature, pain, itch, and C-fiber touch) and vision to negotiate her environment. The patient showed widespread cortical thinning compared with 12 age-matched female controls. In contrast, her right anterior insula was significantly thick. Seed-based resting-state analysis revealed that her right anterior insula had increased connectivity to bilateral posterior insula. A separate independent component analysis revealed the increased connectivity between the insula and visual cortex in the patient. As the insula is an important processing area for temperature and C-fiber tactile information, the increased intrainsular and insular-visual functional connectivity could be related to the patient's use of C-fiber (gentle) touch and temperature information in conjunction with visual information to navigate her environment. We, thus, demonstrated plasticity in networks involving the insular cortex following denervation of large-diameter somatosensory afferents.

Cross-modal recruitment of primary visual cortex by auditory stimuli in the nonhuman primate brain: a molecular mapping study

Recent studies suggest that exposure to only one component of audiovisual events can lead to cross-modal cortical activation. However, it is not certain whether such crossmodal recruitment can occur in the absence of explicit conditioning, semantic factors, or long-term associations. A recent study demonstrated that crossmodal cortical recruitment can occur even after a brief exposure to bimodal stimuli without semantic association. In addition, the authors showed that the primary visual cortex is under such crossmodal influence. In the present study, we used molecular activity mapping of the immediate early gene zif268. We found that animals, which had previously been exposed to a combination of auditory and visual stimuli, showed increased number of active neurons in the primary visual cortex when presented with sounds alone. As previously implied, this crossmodal activation appears to be the result of implicit associations of the two stimuli, likely driven by their spatiotemporal characteristics; it was observed after a relatively short period of exposure (~45 min) and lasted for a relatively long period after the initial exposure (~1 day). These results suggest that the previously reported findings may be directly rooted in the increased activity of the neurons occupying the primary visual cortex.

Correlating anterior insula gray matter volume changes in young people with clinical and neurocognitive outcomes: an MRI study

BACKGROUND

The anterior insula cortex is considered to be both the structural and functional link between experience, affect, and behaviour. Magnetic resonance imaging (MRI) studies have shown changes in anterior insula gray matter volume (GMV) in psychosis, bipolar, depression and anxiety disorders in older patients, but few studies have investigated insula GMV changes in young people. This study examined the relationship between anterior insula GMV, clinical symptom severity and neuropsychological performance in a heterogeneous cohort of young people presenting for mental health care.

METHODS

Participants with a primary diagnosis of depression (n = 43), bipolar disorder (n = 38), psychosis (n = 32), anxiety disorder (n = 12) or healthy controls (n = 39) underwent structural MRI scanning, and volumetric segmentation of the bilateral anterior insula cortex was performed using the FreeSurfer application. Statistical analysis examined the linear and quadratic correlations between anterior insula GMV and participants' performance in a battery of clinical and neuropsychological assessments.

RESULTS

Compared to healthy participants, patients had significantly reduced GMV in the left anterior insula (t = 2.05, p = .042) which correlated with reduced performance on a neuropsychological task of attentional set-shifting (ρ = .32, p = .016). Changes in right anterior insula GMV was correlated with increased symptom severity (r = .29, p = .006) and more positive symptoms (r = .32, p = .002).

CONCLUSIONS

By using the novel approach of examining a heterogeneous cohort of young depression, anxiety, bipolar and psychosis patients together, this study has demonstrated that insula GMV changes are associated with neurocognitive deficits and clinical symptoms in such young patients.

Synaesthetic perception of colour and visual space in a blind subject: an fMRI case study

In spatial sequence synaesthesia (SSS) ordinal stimuli are perceived as arranged in peripersonal space. Using fMRI, we examined the neural bases of SSS and colour synaesthesia for spoken words in a late-blind synaesthete, JF. He reported days of the week and months of the year as both coloured and spatially ordered in peripersonal space; parts of the days and festivities of the year were spatially ordered but uncoloured. Words that denote time-units and triggered no concurrents were used in a control condition. Both conditions inducing SSS activated the occipito-parietal, infero-frontal and insular cortex. The colour area hOC4v was engaged when the synaesthetic experience included colour. These results confirm the continued recruitment of visual colour cortex in this late-blind synaesthetes. Synaesthesia also involved activation in inferior frontal cortex, which may be related to spatial memory and detection, and in the insula, which might contribute to audiovisual integration related to the processing of inducers and concurrents.

Visuo-haptic neuronal convergence demonstrated with an inversely effective pattern of BOLD activation

We investigated the neural substrates involved in visuo-haptic neuronal convergence using an additive-factors design in combination with fMRI. Stimuli were explored under three sensory modality conditions: viewing the object through a mirror without touching (V), touching the object with eyes closed (H), or simultaneously viewing and touching the object (VH). This modality factor was crossed with a task difficulty factor, which had two levels. On the basis of an idea similar to the principle of inverse effectiveness, we predicted that increasing difficulty would increase the relative level of multisensory gain in brain regions where visual and haptic sensory inputs converged. An ROI analysis focused on the lateral occipital tactile-visual area found evidence of inverse effectiveness in the left lateral occipital tactile-visual area, but not in the right. A whole-brain analysis also found evidence for the same pattern in the anterior aspect of the intraparietal sulcus, the premotor cortex, and the posterior insula, all in the left hemisphere. In conclusion, this study is the first to demonstrate visuo-haptic neuronal convergence based on an inversely effective pattern of brain activation.

Integration of visual and tactile signals from the hand in the human brain: an FMRI study

In the non-human primate brain, a number of multisensory areas have been described where individual neurons respond to visual, tactile and bimodal visuotactile stimulation of the upper limb. It has been shown that such bimodal neurons can integrate sensory inputs in a linear or nonlinear fashion. In humans, activity in a similar set of brain regions has been associated with visuotactile stimulation of the hand. However, little is known about how these areas integrate visual and tactile information. In this functional magnetic resonance imaging experiment, we employed tactile, visual, and visuotactile stimulation of the right hand in an ecologically valid setup where participants were looking directly at their upper limb. We identified brain regions that were activated by both visual and tactile stimuli as well as areas exhibiting greater activity in the visuotactile condition than in both unisensory ones. The posterior and inferior parietal, dorsal, and ventral premotor cortices, as well as the cerebellum, all showed evidence of multisensory linear (additive) responses. Nonlinear, superadditive responses were observed in the cortex lining the left anterior intraparietal sulcus, the insula, dorsal premotor cortex, and, subcortically, the putamen. These results identify a set of candidate frontal, parietal and subcortical regions that integrate visual and tactile information for the multisensory perception of one's own hand.

Unimodal responses prevail within the multisensory claustrum

The claustrum receives afferent inputs from multiple sensory-related brain areas, prompting speculation about a role in integrating information across sensory modalities. Here we directly test this hypothesis by probing neurons in the primate claustrum for functional characteristics of multisensory processing. To this end we recorded neuronal responses to naturalistic audio-visual stimuli from the claustra of alert monkeys. Our results reveal the existence of distinct claustral zones comprised of unimodal neurons associated with the auditory and visual modalities. In a visual zone within the ventral claustrum neurons responded to visual stimuli but not to sounds, whereas in an auditory zone located within the central claustrum neurons responded to sounds but not to visual stimuli. Importantly, we find that neurons within either zone are not influenced by stimuli in the other modality and do not exhibit the typical response characteristics usually associated with multisensory processing. While these results confirm the notion of the claustrum as a multisensory structure per se, they argue against the hypothesis of the claustrum serving as an integrator of sensory information.

Equivalent activation of the hippocampus by face-face and face-laugh paired associate learning and recognition

The human hippocampus is known to play an important role in relational memory. Both patient lesion studies and functional-imaging studies have shown that it is involved in the encoding and retrieval from memory of arbitrary associations. Two recent patient lesion studies, however, have found dissociations between spared and impaired memory within the domain of relational memory. Recognition of associations between information of the same kind (e.g., two faces) was spared, whereas recognition of associations between information of different kinds (e.g., face-name or face-voice associations) was impaired by hippocampal lesions. Thus, recognition of associations between information of the same kind may not be mediated by the hippocampus. Few imaging studies have directly compared activation at encoding and recognition of associations between same and different types of information. Those that have have shown mixed findings and been open to alternative interpretation. We used fMRI to compare hippocampal activation while participants studied and later recognized face-face and face-laugh paired associates. We found no differences in hippocampal activation between our two types of stimulus materials during either study or recognition. Study of both types of paired associate activated the hippocampus bilaterally, but the hippocampus was not activated by either condition during recognition. Our findings suggest that the human hippocampus is normally engaged to a similar extent by study and recognition of associations between information of the same kind and associations between information of different kinds.

Anterior insula activations in perceptual paradigms: often observed but barely understood

Anterior insular cortex is among the non-sensory brain regions most commonly found activated in functional brain imaging studies on visual and auditory perception. However, most of these studies do not explicitly address the functional role of this specific brain region in perception, but rather report its activation as a by-product. Here, we attempt to characterize the involvement of anterior insular cortex in various perceptual paradigms, including studies of visual awareness, perceptual decision making, cross-modal sensory processes and the role of spontaneous neural activity fluctuations in perception. We conclude that anterior insular cortex may be associated with perception in that it underpins heightened alertness of either stimulus- or task-driven origin, or both. Such a mechanism could integrate endogenous and exogenous functional demands under the joint criterion of whether they challenge an individual's homeostasis.

A distributed cortical representation underlies crossmodal object recognition in rats

The mechanisms by which the brain integrates the unimodal sensory features of an object into a comprehensive multimodal object representation are poorly understood. We have recently developed a procedure for assessing crossmodal object recognition (CMOR) and object feature binding in rats using a modification of the spontaneous object recognition (SOR) paradigm. Here we show for the first time that rats are capable of spontaneous crossmodal object recognition when they are asked to recognize a visually presented object having previously only explored the tactile features of that object. Moreover, rats with bilateral perirhinal cortex (PRh) lesions were impaired on the CMOR task and a visual-only, but not a tactile-only, version of SOR. Conversely, rats with bilateral posterior parietal cortex (PPC) lesions were impaired on the CMOR and tactile-only tasks but not the visual-only task. Finally, crossmodal object recognition ability was severely and selectively impaired in rats with unilateral lesions made to PRh and PPC in opposite hemispheres. Thus, spontaneous tactile-to-visual crossmodal object recognition in rats relies on an object representation that requires functional interaction between PRh and PPC, which appear to mediate the visual and tactile information-processing demands of the task, respectively. These results imply that, at least under certain conditions, the separate sensory features of an object are represented in a distributed manner in the cortex. The novel paradigm introduced here should be a valuable tool for further study of the neurobiological bases of crossmodal cognition and object feature binding.

Crossmodal recruitment of primary visual cortex following brief exposure to bimodal audiovisual stimuli

Several lines of evidence suggest that exposure to only one component of typically audiovisual events can lead to crossmodal cortical activation. These effects are likely explained by long-term associations formed between the auditory and visual components of such events. It is not certain whether such crossmodal recruitment can occur in the absence of explicit conditioning, semantic factors, or long-term association; nor is it clear whether primary sensory cortices can be recruited in such paradigms. In the present study we tested the hypothesis that crossmodal cortical recruitment would occur even after a brief exposure to bimodal stimuli without semantic association. We used positron emission tomography, and an apparatus allowing presentation of spatially and temporally congruous audiovisual stimuli (noise bursts and light flashes). When presented with only the auditory or visual components of the bimodal stimuli, naïve subjects showed only modality-specific cortical activation, as expected. However, subjects who had previously been exposed to the audiovisual stimuli showed increased cerebral blood flow in the primary visual cortex when presented with sounds alone. Functional connectivity analysis suggested that the auditory cortex was the source of visual cortex activity. This crossmodal activation appears to be the result of implicit associations of the two stimuli, likely driven by their spatiotemporal characteristics; it was observed after a relatively short period of exposure (approximately 45 min), and lasted for a relatively long period after the initial exposure (approximately 1 day). The findings indicate that auditory and visual cortices interact with one another to a larger degree than typically assumed.

Neural correlates of developmental coordination disorder: a review of hypotheses

Affecting 5% to 6% of school-age children, developmental coordination disorder is characterized by a marked impairment of motor coordination that significantly interferes with activities of daily living and academic achievement. Little is known about the etiology of developmental coordination disorder, but the disorder often coexists with attention-deficit hyperactivity disorder (ADHD), speech/language impairment, and/or reading disability. This comprehensive review examines the literature supporting or refuting hypothesized neural correlates of developmental coordination disorder and suggests directions for future research. Potential sources of neuropathology include the cerebellum, parietal lobe, corpus callosum, and basal ganglia. Comorbidities and deficits associated with developmental coordination disorder are highly suggestive of cerebellar dysfunction; yet, given the heterogeneity of this disorder, it is likely that the cerebellum is not the only neural correlate. Neuroimaging studies and behavioral investigations of learning-related change in motor behavior are the next critical step in enhancing our understanding of developmental coordination disorder.

Multisensory integration of sounds and vibrotactile stimuli in processing streams for "what" and "where"

The segregation between cortical pathways for the identification and localization of objects is thought of as a general organizational principle in the brain. Yet, little is known about the unimodal versus multimodal nature of these processing streams. The main purpose of the present study was to test whether the auditory and tactile dual pathways converged into specialized multisensory brain areas. We used functional magnetic resonance imaging (fMRI) to compare directly in the same subjects the brain activation related to localization and identification of comparable auditory and vibrotactile stimuli. Results indicate that the right inferior frontal gyrus (IFG) and both left and right insula were more activated during identification conditions than during localization in both touch and audition. The reverse dissociation was found for the left and right inferior parietal lobules (IPL), the left superior parietal lobule (SPL) and the right precuneus-SPL, which were all more activated during localization conditions in the two modalities. We propose that specialized areas in the right IFG and the left and right insula are multisensory operators for the processing of stimulus identity whereas parts of the left and right IPL and SPL are specialized for the processing of spatial attributes independently of sensory modality.