Encoding and modulation of vibration representations in human neocortex

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PROJECT SUMMARY/ABSTRACT Touch comprises an exquisite sensitivity to vibrations. This sensitivity underlies our ability to perceive textures and sense through handheld tools. Much of the information conveyed by vibrations is carried in their spectral content. Thus, vibration perception likely involves cortical processing that is analogous to the processes that support hearing. Although the neural encoding of vibrations in the peripheral somatosensory system is established, far less is known about vibration representations in the central nervous system. In this project, we will extend on our investigations of the cortical basis of vibration processing and determine on how vibration frequency representations are impacted by selective attention and multisensory context in the human brain. Our understanding of how cortical responses relate to perception is predicated on knowledge of how sensory information is selectively encoded in neural populations. Indeed, without knowing the logic of how sensory signals are represented and transformed across the brain, it is difficult to understand how sensory responses are shaped by attention state or multisensory context. Although much is known about neural tuning for visual and auditory stimulus features, relatively little is known about somatosensory tuning mechanisms, particularly with respect to the frequency content of vibrations. We recently uncovered evidence for somatosensory tuning for vibration frequency in the human brain. This proposal builds on the observation of somatosensory tuning to test the overarching hypothesis that a cortical processing hierarchy supports the encoding and elaboration of vibration frequency information. We will address a number of fundamental questions using human behavior, functional neuroimaging, and modeling. In Aim 1, we will establish how selective attention impacts frequency representations in voxel-level activity. In Aim 2, we will establish how auditory frequency information – which is known to bias tactile frequency perception in humans – is integrated with vibration frequency information in voxel-level activity. In Aim 3, we will test more complex stimuli to identify brain regions that respond to vibration comprising frequency changes (sweeps) and establish whether cortical responses reflect tuning for time varying frequency signals. Collectively, these experiments will advance our understanding of how the human brain supports vibration perception and how touch is combined with audition for multisensory cognition. Our findings may inform the diagnosis and treatment of sensory, cognitive, and psychiatric disorders involving somatosensory deficits, such as in individuals with brain damage, autism, schizophrenia, and age-related cognitive impairments including Alzheimer’s disease.