The Journal of Neuroscience, April 15, 2002, 22(8):3277-3284
Midline Thalamic Region: Widespread Excitatory Input to the
Entorhinal Cortex and Amygdala
D. X.
Zhang and
E. H.
Bertram
Department of Neurology, University of Virginia Health Science
Center, Charlottesville, Virginia 22908
The midline thalamus has a role in memory formation and has well
described projections to multiple limbic sites including the
hippocampus, amygdala, and entorhinal cortex. Stimulation of this
region evokes excitatory responses in the CA1 region of the
hippocampus, but nothing is known about the nature of thalamic influence on other limbic sites such as the entorhinal cortex and the
amygdala. In this study we electrically stimulated the midline thalamus
in anesthetized rats to determine whether responses could be evoked in
the amygdala or entorhinal cortex. In addition we examined the
distribution of the responses within the target regions as well as the
effect of short interval paired or high-frequency tetanizing
stimulation. We found reproducible responses in the entorhinal cortex
and the amygdala with a distribution of responses that matched the
described synaptic input from the thalamus. In addition, high-frequency
stimulation induced a consistent long-term potentiation in the two
sites. Paired stimulation resulted in depression of the test response
in the amygdala, but a facilitation in the entorhinal cortex. These
findings indicate that the midline has a significant monosynaptic
excitatory influence in the amygdala and the entorhinal cortex.
Combined with the previous work in the hippocampus, this study suggests
that the midline thalamus plays a significant role in limbic physiology
and may serve to synchronize activity in this system.
Key words:
thalamus; amygdala; entorhinal cortex; physiology; long-term potentiation; thalamolimbic regional interactions; limbic
system
Copyright © 2002 Society for Neuroscience 0270-6474/02/2283277-08$05.00/0
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