Rhesus monkeys were exposed to lesioning of a specific brain area, and when they woke up they showed a pronounced decrease in their fear responses. the part of the brain that was most likely under investigation in this study was the . amygdala
b. hippocampus
c. basal ganglia
d. medulla oblongata

a. amygdala

Explanation:

According to my research on studies conducted by various neurologists, I can say that based on the information provided within the question the part of the brain that was most likely under investigation in this study was the amygdala. This can be said because the amygdala is the part of the brain that is responsible for emotions, survival instincts (which dictates fear levels), and memory.

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