Mentor: Professor Thomas
The amygdala is a section of the temporal lobe which acts to create anxiety. It is believed that several other areas, such as the medial prefrontal cortex and the lateral septum, send inhibitory inputs to the amygdala to mediate these anxiety producing effects. In order for the amygdala to cause anxiety, then this inhibitory system must be inhibited in some way so that the first sign of increased amygdala firing is not countered by these inhibitory regions. The mechanism of inhibition is still unknown, but to understand it we must first understand the relationship between the amygdala and its inhibitory regions.
This study will examine the actions of the amygdala and the lateral septum in conditioned fear environments. Rats were implanted with a bundle of eight small electrodes in each of these regions so that single cell activity could be recorded. Rats were then placed alternately in a chamber where they were safe from shock and one in which they received regular shocks. The two chambers were designed to look very different from one another so that rats could tell them apart easily. We hypothesize that in the safe chamber the lateral septum will fire more than the amygdala, since it is acting to inhibit the fear causing firing there and that in the shock chamber the amygdala will show more activity and the lateral septum less.
We will then administer an anti-anxiety drug, chlordiazopoxide, to the rats and put them back into the chambers. We predict that with the addition of the drug, the differences in firing rate in each chamber will be evened out, since the drug blocks the inhibition of the lateral septum that is the cause of increased amygdal firing.