gating of movement-related neural activity ?

MGLinWS mglinws at
Thu Aug 24 07:04:55 EST 1995

arm at helix (Andrew_R._Mitz) wrote:

:In similar tasks with monkeys we have used 3 discrete delays rather
:than a continuous random time range for the preparatory period.
:Histograms of many premotor units show peaks in the
:preparatory period around the time of the first and second descrete
:delays.  Of course, you can only see both peaks on the trials that
:use the longest delay.  Presumably the monkey is trying to predict
:the occurance of the trigger signal.  More continuous time ranges
:do not produce such pronounced peaks, but some units show increased
:activity near the end of the preparatory period when the longest
:delays are used.

Thanks for this info.  

My experiments next week will examine exactly this issue. I will run
sessions (>300 trials) with preparatory intervals of either 500 or 1500
msec.  Based on pilot studies, the animal should come to "expect" the
trigger stimulus at these times and I hope to find neural correlates of
this process.  

In addition, I will run sessions with unusually short (200) and long
(2500) delays to examine the neural correlates of reactions to these
"unexpected" delays.  Pilot studies showed that the rats respond slowly to
the unanticipated short delays and respond prematurely to the longer
intervals.  (Perhaps the task enacts not only motor readiness but also a
timing process. such that the animal responds after a period in which the
trigger "should have" occurred.)  

Finally, I will test the effects of a series of short (500) or long (1500)
delays.  Pilot studies show that the rat will respond prematurely after a
long delay that follows a run of several short delays and slowly after
short delay that follows a run of several long delays.

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