[Abstract Title]. - Society for Neuroscience

Abstract: Slow finger movements in man are not smooth but characterised by 8-12 Hz
discontinuities in finger acceleration. The primary motor cortex (M1) has been proposed to be a
source of these oscillations. We trained two macaque monkeys to track a moving target by
performing index finger flexion/extension movements and recorded local field potentials (LFPs)
and extracellular spiking activity from M1. There was significant coherence between both LFPs
and spikes with finger acceleration in the ~10 Hz range. Subsets of the M1 cells were
antidromically identified as pyramidal tract neurons (PTNs). Some PTNs were further identified
as corticomotoneuronal (CM) cells by spike triggered averaging of rectified EMG. There was
significant coherence between PTNs and CM cells and finger acceleration between 6-13 Hz.
LFP-acceleration coherence was similar for flexion and extension movements (0.094 at 9.8 Hz
and 0.11 at 6.8 Hz respectively), but substantially smaller during periods of steady position
holding (0.0067 at 9.35 Hz). The coherence phase showed a significant linear relationship with
frequency over the 6-13 Hz range, as expected for a constant conduction delay; the slope
indicated that LFP lagged acceleration by 17.1±7.4 ms. Directed coherence (Granger causality)
analysis supported the conclusion that the dominant interaction was in the acceleration to LFP
(i.e. sensory) direction. The phase relationships between both LFPs and cell spikes and finger
acceleration shifted by approximately π radians in flexion compared to extension trials. We
conclude that although M1 activity is synchronised with peripheral oscillations during slow
finger movements, M1 is unlikely to be the sole origin of these movement discontinuities.
Disclosures: S.N. Baker , None; E.R. Williams, None; D.S. Soteropoulos, None.
Poster
277. Voluntary Movement: Cortical Planning and Execution II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 277.5/KK31
Topic: D.17.b. Cortical planning and execution
Support: Academic Frontier Project from the Ministry of Education, Culture, Sports, Science
and Technology of Japan to Japan Women's College of Physical Education
a Grant-in-Aid for Young Scientists (B, #19700532) to Kenichi Shibuya
Title: Reduced contribution of the ipsilateral primary motor cortex to force modulation with
short-term motor learning in humans
Authors: *K. SHIBUYA 1 , M. IWADATE 2 , T. SADAMOTO 1 ;
1 Res. Inst. of Physical Fitness, JWCPE, Tokyo, Japan; 2 Nihon Univ., Narashino, Japan