Nondeclarative Learning and the Amygdala

Previously, we used the example of a microwave bell and mouth watering to introduce nondeclarative learning. Physiologist Ivan Pavlov was the first to investigate classical conditioning. His studies showed that by repetitive pairing of a conditioning stimulus (bell) with an unconditional stimulus (food), dogs salivated at the sound of the bell. It was Pavlov's idea that the cerebral cortex was involved in classical conditioning.

Studies with animals show that the amygdala is involved in classical conditioning. In this case, the pairing of a tone with a foot shock elicits a freezing response when the tone is presented alone. That is, the tone predicts the presentation of the shock. Neurons in the amygdala respond to a shock-related tone only. Furthermore, damage to the amygdala eliminates the physiological changes associated with the freezing response. What is the circuit involved in this type of information processing? Studies by LeDoux and cow-orkers suggest that auditory information arriving at the auditory cortex travels to the basolateral nucleus and the central nucleus of the amygdala; first the auditory information arrives at the basolateral nucleus, then to the central nucleus. The central nucleus then sends information to the hypothalamus, which mediates autonomic responses (increased in heart rate); periaqueductal the gray area the brain stem, which mediates the actual emotional response (freezing); and the cerebral cortex, which mediate the emotional experience.

In the next section, we show that information processing can also be studied at the cellular and molecular level. Indeed, as suggested by Semon, Santiago Ramon y Cajal, and William James, the engram is formed by physiological changes in neurons. Neurons in both the hippocampus and the amygdala display physiological changes that are believed to mediate information storage.

Anxiety and Depression 101

Anxiety and Depression 101

Everything you ever wanted to know about. We have been discussing depression and anxiety and how different information that is out on the market only seems to target one particular cure for these two common conditions that seem to walk hand in hand.

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