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Lookup NU author(s): Dr Claire Witham,
Professor Stuart Baker
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Witham CL, Baker SN. Coding of digit displacement by cell spiking and network oscillations in the monkey sensorimotor cortex. J Neurophysiol 108: 3342-3352, 2012. First published September 26, 2012; doi:10.1152/jn.00462.2012.-beta-Band oscillations occur in motor and somatosensory cortices and muscle activity. Oscillations appear most strongly after movements, suggesting that they may represent or probe the limb's final sensory state. We tested this idea by training two macaque monkeys to perform a finger flexion to one of four displacements, which was then held for 2 s without visual feedback of absolute displacement. Local field potential (LFP) and single unit spiking were recorded from the rostral and caudal primary motor cortex and parietal areas 3a, 3b, 2, and 5. Information theoretic analysis determined how well unit firing rate or the power of LFP oscillations coded finger displacement. All areas encoded significant information about finger displacement after the movement into target, both in beta-band (similar to 20 Hz) oscillatory activity and unit firing rate. On average, the information carried by unit firing was greater (0.07 bits) and peaked earlier (0.73 s after peak velocity) than that by LFP beta-oscillations (0.05 bits and 0.95 s). However, there was considerable heterogeneity among units: some cells did not encode maximal information until midway through the holding phase. In 30% of cells, information in rate lagged information in LFP oscillations recorded at the same site. Finger displacement may be represented in the cortex in multiple ways. Coding the digit configuration immediately after a movement probably relies on nonoscillatory feedback, or efference copy. With increasing delay after movement cessation, oscillatory processing may also play a part.
Author(s): Witham CL, Baker SN
Publication type: Article
Publication status: Published
Journal: Journal of Neurophysiology
Print publication date: 26/09/2012
ISSN (print): 0022-3077
ISSN (electronic): 1522-1598
Publisher: American Physiological Society
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