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Encoding of movement direction in different frequency ranges of motor cortical local field potentials.
Rickert J, Oliveira SC, Vaadia E, Aertsen A, Rotter S, Mehring C.
of Neurobiology and Biophysics, Institute of Biology III,
Albert-Ludwigs-University, 79104 Freiburg, Germany.
Recent studies showed that the
low-frequency component of local field potentials (LFPs) in monkey
motor cortex carries information about parameters of voluntary arm
movements. Here, we studied how different signal components of the LFP
in the time and frequency domains are modulated during center-out arm
movements. Analysis of LFPs in the time domain showed that the
amplitude of a slow complex waveform beginning shortly before the onset
of arm movement is modulated with the direction of the movement.
Examining LFPs in the frequency domain, we found that
direction-dependent modulations occur in three frequency ranges, which
typically increased their amplitudes before and during movement
execution: < or =4, 6-13, and 63-200 Hz. Cosine-like tuning was
prominent in all signal components analyzed. In contrast, activity in a
frequency band approximately 30 Hz was not modulated with the direction
of movement and typically decreased its amplitude during the task. This
suggests that high-frequency oscillations have to be divided into at
least two functionally different regimes: one approximately 30 Hz and
one >60 Hz. Furthermore, using multiple LFPs, we could show that LFP
amplitude spectra can be used to decode movement direction, with the
best performance achieved by the combination of different frequency
ranges. These results suggest that using the different frequency
components in the LFP is useful in improving inference of movement
parameters from local field potentials.
PMID: 16192371 [PubMed - in process]
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