Biology subjects

Pouratian, N.

Publications and source records attributed to Pouratian, N..

21 records · Page 2Linked to original sources

bioRxiv2020

Movement-related changes in pallidocortical synchrony differentiate action execution and observation in humans

Suppression of local and network alpha (8-12 Hz) and beta (12-35 Hz) oscillations in the human basal ganglia-thalamocortical (BGTC) circuit is a prominent feature of movement. Local alpha/beta power, cross-region beta phase coupling, and phase-amplitude coupling (PAC) have all been shown to be suppressed during movement in multiple nodes of the BGTC. However, the specificity of these various movement-related changes to actual movement execution remains poorly understood. To differentiate signals that are specifically related to movement execution, we compared changes in globus pallidus internus (GPi) and motor cortical local oscillatory activity and coupling (cross-region phase coupling and local PAC) during movement execution and movement observation in 12 patients with Parkinson disease undergoing deep brain stimulator implantation. We hypothesized that network coupling is more directly related to movement execution than local power changes, given the putative role of pathological network coupling in movement disorders such as Parkinson disease. We observed suppression of alpha/beta power during action observation and execution in the globus pallidus and motor cortex during both action execution and action observation. In contrast, pallidocortical coherence and GPi and motor cortical alpha/beta-gamma PAC were significantly suppressed only during action execution. Our results demonstrate a functional dissociation within the BG-cortical network during action execution and observation in which suppression of BG-cortical functional connectivity and local phase amplitude coupling are features specifically of overt movement, suggesting a particularly important role in motor execution. This has implications for identification and use of intracranial signals for closed loop brain stimulation therapies.

neuroscience↗

bioRxiv2020

A shared neural substrate for action verbs and observed actions in human posterior parietal cortex.

High-level sensory and motor cortical areas are activated when processing the meaning of language, but it is unknown whether, and how, words share a neural substrate with corresponding sensorimotor representations. We recorded from single neurons in human posterior parietal cortex (PPC) while participants viewed action verbs and corresponding action videos from multiple views. We find that PPC neurons exhibit a common neural substrate for action verbs and observed actions. Further, videos were encoded with mixtures of invariant and idiosyncratic responses across views. Action verbs elicited selective responses from a fraction of these invariant and idiosyncratic neurons, without preference, thus associating with a statistical sampling of the diverse sensory representations related to the corresponding action concept. Controls indicated the results are not the product of visual imagery nor arbitrary learned associations. Our results suggest that language may activate the consolidated visual experience of the reader.

neuroscience↗

bioRxiv2018

Dynamic Electrical Stimulation of Sites in Visual Cortex Produces Form Vision in Sighted and Blind Humans

Visual cortical prosthetics (VCPs) offer the promise of restoring sight to blind patients. Electrical stimulation of a single site in visual cortex can reliably produce a percept of a spot of light in a fixed visual field location, known as a phosphene. Researchers developing VCPs have assumed that multiple phosphenes produced by concurrent stimulation of multiple sites in visual cortex can combine to form a coherent form, like pixels in a visual display. However, existing data do not support this assumption. Therefore, we developed a novel stimulation paradigm for VCPs termed dynamic current steering in which the visual form to be conveyed is traced on the surface of visual cortex by electrically stimulating electrodes in a dynamic sequence. When tested in sighted and blind subjects, this method of stimulating visual cortex allowed for the immediate recognition of a variety of letter shapes without training and with high accuracy.\n\nOne Sentence SummaryStimulating human visual cortex using dynamic patterns of activity allows both blind and sighted patients to perceive visual percepts of useful forms.

neuroscience↗