gating of movement-related neural activity ?

Eric Wassermann ewass at
Tue Aug 22 09:11:49 EST 1995

In article <41ced5$l2n at>, mglinws at (MGLinWS) wrote:

> 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
> (Pascual-Leone
> :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
> "gating",
> 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
> alterations 
> in the striatum over the course of a behavioral reaction.  Perhaps the
> length 
> of the preparatory interval preceeding the response is associated with 
> alterations in the excitability of motor cortex?

I think it is far more likely that the rise in excitability in M1
preceding movement is conditioned by activity in the basal ganglia via the
ventral thalamus, since it is abnormal in Parkinson's disease where the
motor cortex is not directly affected (Hallett et al. Electroenceph Clin
Neurophysiol 1991;?76:?76; Pascual-Leone et al. 1994 Neurology;44:884)

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

Not of this phenomenon per se, at least that I know of.  

Eric Wassermann

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