Tactile Coding in Cuneate Nucleus

University Of Chicago, Chicago IL

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Abstract

? DESCRIPTION (provided by applicant): The purpose of this project is to achieve the first recordings of single neurons in the cuneate nucleus (CN) of awake non-human primates. CN is a tiny, previously inaccessible, structure at the base of the brainstem that is the gateway for sensory signals from our upper limbs to our brain. We hope to generate foundational scientific data that will illuminate the poorly understood role of CN in processing information about somatosensation. A central question in sensory neuroscience is how sensory representations are transformed as they ascend the neuraxis. In primates, the coding of tactile information and of limb state has been extensively studied in the nerve and in primary somatosensory cortex (S1). Previous studies have shown that responses of individual S1 neurons reflect convergent input from multiple tactile submodalities. Furthermore, while the responses of individual afferents convey ambiguous information about stimuli, those of cortical neurons explicitly carry information about behaviorally relevant stimulus features, such as edge orientation or motion direction. In contrast, much less attention has been directed towards the two intervening synapses in the medial lemniscal pathway, namely the dorsal column nuclei (of which the CN is one) and the ventroposterior nucleus of the thalamus. We have developed an approach to chronically implant electrode arrays in the CN of primates so that we will be able, for the first time, to record single unit activity from this structure in awake, behaving animals. We propose to probe the responses of CN neurons to a wide variety of stimuli that have been used to investigate tactile coding at the periphery and in cortex. We will (a) characterize the receptive field structure of individual CN neurons; (b) assess the extent to which CN neurons receive convergent input from multiple tactile submodalities; and (c) determine the extent to which the feature selectivity observed in S1 begins to emerge in CN. The proposed study will not only shed light on somatosensory coding in CN, but it will also pave the way for developing neural interfaces with the brain stem for use in upper-limb neuroprostheses to restore touch for amputees and patients with spinal cord injury.