Journal of Neuroscience, Vol 11, 48-58, Copyright © 1991 by Society for Neuroscience
Patterns of unit activity in the rostral thalamus of cats related to short-latency discrimination between different auditory stimuli
CD Woody, E Gruen, O Melamed and V Chizhevsky
Brain Research Institute, UCLA Medical Center 90024.
Short-latency auditory-responsive units were found in the rostral thalamus
of cats during performance of conditioned eyeblink responses (CRs) elicited
discriminatively by a forward-paired, 70-dB-click conditioned stimulus (CS)
as opposed to a backward-paired, 70-dB-hiss discriminative stimulus (DS).
Discharges in response to the CS or DS were found in 57% of 138 units
tested. Forty-one percent of units responding to the CS did so at latencies
of less than 40 msec. After conditioning a discriminative CR to click CS,
an increase in the ratio of CS-evoked activity to baseline activity was
found relative to that before conditioning. This increase was attributable,
in part, to a decrease in baseline activity and, in part, to an increase in
the magnitude of response to the CS. These responses preceded early
components of the electromyographically measured motor responses with
latencies sufficient to contribute to initiation of the movement. After
acquisition of the CR, the proportion of CS responsive units also
increased. We conclude that this area of the thalamus, a region thought to
support thalamocortical reverberatory activity, also functions to transmit
short-latency auditory signals. Our evidence further suggests that this
region may participate in the elicitation of conditioned responses by
specific auditory stimuli and in discrimination between auditory stimuli of
different significance.