478 Single-Neuron and Columnar Computations in the Human Prefrontal Cortex Underlying Transformations From Conscious Visual Perception to Speech Production

Abstract

INTRODUCTION: The basic functional unit of the mammalian neocortex is the cortical column. It consists of a vast diversity of circuit elements and interconnected layers supporting a range of computations for cognitive functions. While much progress has been made in our understanding of its functional architecture in animal models, its role in complex, uniquely human cognitive processes remain unknown. METHODS: We utilized a new columnar recording approach in humans participating of cognitive tasks, while undergoing awake neurosurgical procedures. The novelty of this approach hinged on utilizing state-of-the-art Neuropixels probes for our recordings, a silicon-based electrophysiology recording electrodes with high channel count and recording site density. This technology allows us to measure neural activity with single cell resolution throughout the neocortical column and its layers, and at a scale that is far beyond the capabilities of current clinically-approved devices. The participants performed a naturalistic visual priming-based sentence production task that provided them with pictorial representations of events that had to be articulated in specific form and order. RESULTS: We observed distinct spatiotemporal activity dynamics throughout the cortical column in the language-dominant prefrontal cortex that encoded a preparatory mode for speech generation, as well as visual perception and sentence construction processing stages during natural speech. Furthermore, we observed the emergence of this columnar activity pattern with optimal visual inspection of presented images (by high resolution eye and pupil tracking) and associated improved performance during the task. CONCLUSIONS: These results highlight a functional organization of the cortical column in the human prefrontal cortex subserving sensory-motor transformations for visual conscious perception and speech production, with profound implications for future brain machine interfaces that aim to restore complex human cogntive functions.