The Journal of Neuroscience, December 15, 2002, 22(24):11026-11034
The Contribution of the Amygdala to Conditioned Thalamic
Arousal
Mary Eileen
Cain,
Bruce S.
Kapp, and
Corey B.
Puryear
Department of Psychology, University of Vermont, Burlington,
Vermont 05405
Previous research has demonstrated that thalamocortical neurons
within the dorsal lateral geniculate nucleus (dLGN) are affected by an
acoustic, fear-arousing, conditioned stimulus (Cain et al., 2000). This
effect is reflected in an increase in activity and a tonic firing
pattern, a pattern that assures the most accurate relay of information
from the retina to the visual neocortex. Such an effect is considered
to be indicative of a heightened state of arousal. The present research
was designed to determine the extent to which the central nucleus of
the amygdala (ACe) contributes to this effect. To this end, in
experiment 1 extracellular recordings were made from single dLGN
neurons in the awake rabbit during electrical stimulation of the ACe.
Increased neuronal activity was observed in response to stimulation in
the majority of neurons. Neurons that were in a burst firing pattern
immediately before stimulation assumed a tonic firing pattern in
response to stimulation. Experiment 2 was designed to determine whether
inactivation of the ACe with muscimol would attenuate the response of
dLGN neurons in the awake rabbit to the presentation of acoustic,
fear-arousing, conditioned stimuli. Compared with vehicle injections,
infusions of muscimol attenuated both the spontaneous activity and the
response of dLGN neurons to the presentations of these stimuli. The
results provide support for the hypothesis that the amygdala, and in
particular the ACe, contributes to a heightened state of arousal during
conditioned fear.
Key words:
amygdaloid central nucleus; dorsal lateral geniculate
nucleus; electrical stimulation; extracellular single unit recording; Pavlovian conditioning; muscimol
Copyright © 2002 Society for Neuroscience 0270-6474/02/222411026-09$05.00/0