3-06 Attack And Escape Behavior (Part 2)

Front 1

Objective

Describe the role of the amygdala in fear and anxiety.

Back 1

The startle reflex, which is a response to an unexpected loud noise, occurs extremely fast. Psychologists measure the enhancement of a startle reflex as a gauge of fear or anxiety. Investigators have determined which brain areas are most important for enhancing the startle reflex—one key area is the amygdala. Output from the amygdala to the hypothalamus controls autonomic fear responses, such as increased blood pressure. The amygdala has axons to areas of the prefrontal cortex that control approach and avoidance responses. Additional axons extend to various areas in the midbrain that relay info to the nucleus in the pons that controls the startle reflex. Although a rat with damage to the amygdala still shows a normal startle reflex, a fear signal before the loud noise does not enhance the reflex. Damage to the amygdala interferes with both the learning of fear responses and retention of fear responses learned previously.

Front 2

Objective

Discuss the effects of Kluver-Bucy syndrome in monkeys.

Back 2

Kluver-Bucy syndrome is produced by damaging the amygdala in monkeys, which causes them to become tame and placid. These monkeys attempt to pick up lighted matches and other objects that they ordinarily avoid. They display less-than-normal fear of snakes or of larger, more dominant monkeys.

Front 3

Objective

Identify the types of emotional expressions to which the amygdala responds most strongly.

Back 3

We recognize angry expressions faster if directed towards us and fearful expressions faster if they are directed to our side. It is interesting that the amygdala shows greater activation in response to a fearful expression directed towards us, even though the expression is more ambiguous and puzzling (We may wonder why somebody would respond to us with fear). The assumption is that the amygdala is trying to interpret a difficult stimulus.

Front 4

Objective

Describe the effects of amygdala damage in humans.

Back 4

People with amygdala damage do not lose their emotions; they report that they continue to feel anger, fear, happiness, and other emotions more or less normally as a result of life events. However, they are impaired at processing emotional information when the signals are subtle or complicated. For example, amygdala damage interferes with the social judgments that we constantly make about other people. When we look at other people’s faces, some of them strike us, rightly or wrongly, as “untrustworthy,” and looking at a face we regard as untrustworthy strongly activates the amygdala. People with damage to the amygdala regard all faces as about equally trustworthy, and they approach people for help indiscriminately, instead of trying to find people who look and act friendly.

People with amygdala damage also fail to focus their attention on emotional stimuli the way other people do. For example, when most people with an intact brain look at a picture of something highly emotional, such as one person attacking another, they remember the emotional part and forget most of the details in the background. When they hear a highly emotional story, such as one about children who died in a plane crash, they remember the emotional gist and forget the details. When they see a series of words flashed briefly on the screen under distracting conditions, they notice more of the emotionally charged words like kill than unemotional words like pear. In all these regards, people with amygdala damage are different. They remember many of the irrelevant details of a story as much as the emotional gist, and they notice a flashed word like pear about as much as one like kill. Such people also fail to recognize the emotions that people in photographs express, especially when they express fear or disgust. They often have trouble recognizing expressions of anger, surprise, arrogance, guilt, admiration, and flirtation.

Front 5

Objective

Explain how benzodiazepines work on the nervous system.

Back 5

The most commonly used anti-anxiety drugs are the benzodiazepines, such as diazepam (Valium). Benzodiazepines bind to the GABAa receptor complex, which includes a site that binds GABA as well as sites that modify the sensitivity of the binding site to GABA. At the center of the GABAa receptor complex is a chloride channel. When open, it permits chloride ions to cross the membrane into the neuron, hyperpolarizing the cell (inhibitory effect). Surrounding the chloride channel are four units, each containing one or more sites sensitive to GABA. Benzodiazepines bind to additional sites on three of those four units. When a benzodiazepine molecule attaches, it neither opens nor closes the chloride channel but changes the shape of the receptor so that GABA binds more tightly to the binding site. Benzodiazepines thus facilitate the effects of GABA on the receptor.

Benzodiazepines decrease anxiety and suppress influences that would otherwise increase the startle reflex. For example, ordinarily the startle reflex is enhanced in the presence of a signal previously paired with a shock. Benzodiazepines decrease that effect. They also induce sleepiness, block epileptic convulsions, and impair memory.

Front 6

startle reflex

Back 6

Response to an unexpected loud noise

Front 7

barbiturates

Back 7

Antianxiety drugs; bind to GABA receptors

Front 8

benzodiazepines

Back 8

Most commonly used anti-anxiety drug; bind to GABA receptors

Front 9

GABAA receptor complex

Back 9

Includes a site that binds GABA as well as sites that modify the sensitivity of the GABA site

Front 10

diazepam-binding inhibitor (DBI)

Back 10

Chemical that blocks the behavioral effects of diazepam and other benzodiazepines

Front 11

endozepines

Back 11

An endogenous antibenzodiazepine