gating of movement-related neural activity ?

MGLinWS mglinws at
Tue Aug 22 06:17:57 EST 1995

ewass at (Eric Wassermann) wrote:
:There is very good evidence from human studies using transcranial
:stimulation that the excitability of the primary motor cortex and its
:output systems increases during a reaction time (c.f. Starr et al.
:Electroenceph Clin Neurophysiol 1988;70:26).  Moreover, in a 2 choice
:reaction time, both response channels (muscles representations in M1 and
:downstream connections) are potentiated until about 30 ms prior to
:movement when there is inhibition of the non-chosen channel
:et al. Soc Neurosci Abstr 1992;18:25)
:Is this what you mean by gating of motor activity?

Yes.  This sort of neural activity may be involved in what I termed
although I wnat to read these papers before giving a definite yes or no.
Alterations in the excitability of motor cortex could give rise to
in the striatum over the course of a behavioral reaction.  Perhaps the
of the preparatory interval preceeding the response is associated with 
alterations in the excitability of motor cortex?

Furthermore, the reciprocity you mention between "response" and
channels could potentially account for the heterogeneity I see in the
activity of 
single neurons.  And, these "reciprocal states" could engender
in the time series of spike activity in subcortical structures such as
the striatum.  I have found evidence for reciprocal firing using the joint

peri-stimulus time histogram and will report some of this at this year's 
Neuroscience meeting and in a manuscript that is (and has been) in
preparation (for more than a year now!).

Thanks for the info.

Question: Are there any imaging studies (fast MRI) of this effect
motor cortical excitability) in human subjects ?

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