The interaction of emotion and memory is necessary for establishing a cognitive
map including current context and past experiences, which is used by prefrontal cortex to
regulate the internal state and guide goal directed actions and decision making. The
amygdala, hippocampus and anterior cingulate cortex (ACC) play critical roles in these
processes, but the organization of pathways between them is largely unknown in
primates. This issue was addressed using neural tracers in rhesus monkeys to label the
bidirectional pathways between amygdala and hippocampus and the unidirectional
pathway from hippocampus to ACC. The amygdala sent a robust projection to
hippocampus that formed large and closely spaced dual synapses on spines from the same
dendritic segment, suggesting a strong influence. Further, amygdalar axon boutons
innervated some disinhibitory calretinin neurons in CA1, suggesting enhanced excitatory
influence. In contrast, in CA3 the amygdala pathway innervated calretinin and some of
the powerful parvalbumin inhibitory neurons, which may help enhance memory of
affective events. The reverse pathway from hippocampus densely and mainly targeted the
ventro-medial part of the amygdala, including the basolateral (BL) and paralaminar
basolateral (PLBL) nuclei. Hippocampal terminations formed synapses mostly on spines
vii
of presumed excitatory neurons. Some hippocampal terminations innervated inhibitory
neurons in BL and PLBL and showed a rank of preference, by targeting mostly calretinin,
and then calbindin and least parvalbumin inhibitory neurons. This pattern of innervation
may allow contextual information represented by hippocampus to influence affective
processes in the amygdala. The hippocampus sent strong projections to ACC (A32, A24a
and A25) and targeted particularly A25, suggesting a role in affective and autonomic
regulation. About 90% of hippocampal terminations in A25 innervated excitatory
neurons, suggesting strong excitatory effects. The hippocampal pathway had a close
relationship with postsynaptic D1 receptors in A25, especially in the deep layers.
Dopamine has a strong influence in goal-directed actions, rewards, and attention in
prefrontal cortex in primates, and may facilitate contextual information from the
hippocampus to A25 to influence emotional regulation. The pathways studied were
distinct, and suggest specific roles in emotional memory by the amygdala in
hippocampus, in flexible learning and forgetting fear based on context transmitted from
hippocampus to the amygdala, and in the synthesis of current context and past experience
carried out by the hippocampal pathway to ACC to influence adaptive goal directed
behavior. / 2021-09-27T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/41460 |
| Date | 27 September 2020 |
| Creators | Wang, Jingyi |
| Contributors | Barbas, Helen |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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