Download Chapter 13 Study Questions Key

Chapter 13 Study Questions Key
1. Describe the memory modulation framework. What is the role of the amygdala, the
hippocampus, and the adrenal gland?
It suggests that a behavioral experience can have two independent effects. 1) It can
activate specific sets of neurons that represent and store the content of the
experience; 2) it can activate hormonal and neural systems that can influence the
mechanisms that store the memory. The amygdala modulates other regions in the
brain; the hippocampus is a key structure for storing information; and the adrenal
gland (consisting of the medulla and the cortex) releases hormones that can enhance
the strength of the memory.
2. What are memory modulators?
Hormonal and other neural systems that are not part of the storage system but can
influence the synapses that store the memory.
3. What is the function of epinephrine in the body? Where is it secreted? How is it
different from norepinephrine?
Epinephrine is secreted from the adrenal medulla when an arousing event occurs. It
binds to receptors in the liver, causing the release of glucose into the blood to
support the flight-or-flight response, but in the brain the glucose helps to maintain
transcription and translation processes that strengthen memory. Norepinephrine is
also secreted by the adrenal medulla, but unlike epinephrine, it is also released in
the brain as a neurotransmitter.
4. Given that the hormone epinephrine does not cross the blood–brain barrier, how can it
influence amygdala function?
It does so indirectly by its actions on the vagus nerve. Epinephrine binds to
receptors on the vagus nerve, which projects to the brain where it synapses on and
activates neurons in the solitary tract nucleus (NTS). These neurons project to the
locus coeruleus, which send noradrenergic (norepinephrine) projections to the
amygdala. Thus, norepinephrine release in the amygdala is stimulated by
peripheral epinephrine acting on the vagus nerve.
Epinephrine -> Vagus nerve -> NTS -> LC -> amygdala
5. Describe an experiment that supports the hypothesis that the hormone epinephrine
modulates memory storage processes.
Injecting rats with epinephrine shortly after training increased inhibitory avoidance
when a very low-intensity shock was used. In humans, injections of epinephrine
after viewing visual scenes enhanced the memory for the scenes when testing
occurred a week later.
6. Which memory tasks can be learned and remembered even with the amygdala
removed? Why is that important?
Both the place-learning and visible-platform versions of the Morris water-escape
task can be learned and remembered even when the amygdala is significantly
damaged. This suggests that the amygdala is not an important storage site for the
memory trace.
7. What is propranolol, and how is it used in memory modulation experiments?
It is a beta-adrenergic receptor antagonist, which blocks the receptors that
norepinephrine bind to. If injected into the amygdala after training, it reduces
retention of a memory.
8. Several sources of evidence indicate that the basolateral amygdala modulates memory
storage. What are they?
An injection of lidocaine (a drug that inactivates neurons) into the basolateral
amygdala (BLA) following avoidance training impaired the retention of the
inhibitory avoidance response. Lidocaine had no effect when it was injected into the
central nucleus (CE) of the amygdala.
In contrast, injecting clenbuterol (an adrenergic agonist) into the BLA enhanced
inhibitory avoidance.
9. What evidence suggests that the amygdala modulates memory strength by regulating
the translation of Arc?
Lidocaine injected into the amygdala reduces inhibitory avoidance learning and
reduces levels of Arc protein in the hippocampus. Conversely, clenbuterol is
injected into the amygdala, learning and hippocampal Arc expression are enhanced.
10. What is the evidence for the neuro-hormonal circuit?
1. When epinephrine is administered to anesthetized rats, it activates the vagal
nerve, but this outcome is prevented when a beta-adrenergic receptor antagonist is
applied. 2. Stimulating the vagus nerve increases glutamate in the NTS. 3.
Stimulating the vagus nerve causes burst firing in the locus coeruleus.
11. How is glucose connected to epinephrine and to memory modulation?
Epinephrine can bind to receptors in the liver where it can increase the secretion of
glucose. Glucose may enhance memory by increasing the phosphorylation of CREB,
which acts as a transcription factor.
12. How does glucose release change with age? Does it have effects on memory?
Glucose release is dramatically reduced in aged animals, and this is related to
increased forgetting associated with aging.
13. What are glucocorticoids? Are they effective memory modulators?
Glucocorticoids such as corticosterone are hormones secreted by the adrenal cortex.
They can modulate memory, but they do this primarily by enhancing the action of
norepinephrine.