gating of movement-related neural activity ?

Andrew_R._Mitz arm at helix
Wed Aug 23 22:13:06 EST 1995

MGLinWS (mglinws at wrote:
: arm at helix (Andrew_R._Mitz) wrote:

: The task I use is analogous to a task used by Amalric and Koob (J.
: Neurosci., 1987) to study reaction-time performance in the rat.  I use a
: nose-poke operandum instead of a bar.

: After each correct response, a light inside the operandum is turned on and
: the rat begins each trial by placing his snout inside the operandum, thus
: breaking a photobeam.  This behavior results in the nose-poke operandum
: light turning off and initiates the preparatory interval (500-2000 msec). 
: If the animal sustains the response over this interval, an auditory
: trigger stimulus (tone) is presented for 200 msec.  The animal must
: withdraw from the operandum within 600 msec to obtain a drop of water.

: The goal of this design was to examine how the spike activity of neurons
: that become active during the preparatory interval vary in relation to the
: animal's reaction-time and as a function of the length of the preparatory
: interval.  However, only a portion of the neurons fire in a preparatory
: manner and others fire in relation to movement.  I noticed that both
: "types" of cells varied in relation to the reaction-time and the length of
: the preparatory interval.  The animal's movements did not vary in relation
: to these factors (as determined from time measurements of video-tape of
: the behavior during the neural activity).  

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.

Andrew Mitz, Biomed. Eng., National Institutes | Opinions are mine alone 
of Health Animal Center, Poolesville, MD       | arm at       

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