The Emotional Brain: The Mysterious Underpinnings of Emotional Life by Joseph Ledoux

Author:Joseph Ledoux
Language: eng
Format: mobi
Publisher: Simon & Schuster
Published: 2015-09-21T14:00:00+00:00

FIGURE 7–5

Brain Systems of Emotional Memory and Memory of Emotion.

It is now common to think of the brain as containing a variety of different memory systems. Conscious, declarative or explicit memory is mediated by the hippocampus and related cortical areas, whereas various unconscious or implicit forms of memory are mediated by different systems. One implicit memory system is an emotional (fear) memory system involving the amygdala and related areas. In traumatic situations, implicit and explicit systems function in parallel. Later, if you are exposed to stimuli that were present during the trauma, both systems will most likely be reactivated. Through the hippocampal system you will remember who you were with and what you were doing during the trauma, and will also remember, as a cold fact, that the situation was awful. Through the amygdala system the stimuli will cause your muscles to tense up, your blood pressure and heart rate to change, and hormones to be released, among other bodily and brain responses. Because these systems are activated by the same stimuli and are functioning at the same time, the two kinds of memories seem to be part of one unified memory function. Only by taking these systems apart, especially through studies of experimental animals but also through important studies of rare human cases, are we able to understand how memory systems are operating in parallel to give rise to independent memory functions.

Nevertheless, we know from personal experience that conscious memories can make us tense and anxious, and we need to account for this as well. All that is needed for this to occur is a set of connections from the explicit memory system to the amygdala. There are in fact abundant connections from the hippocampus and the transition regions, as well as many other areas of the cortex, to the amygdala.

It is also possible that implicitly processed stimuli activate the amygdala without activating explicit memories or otherwise being represented in consciousness. As we saw in Chapters 2 and 3, unconscious processing of stimuli can occur either because the stimulus itself is unnoticed or because its implications are unnoticed. For example, suppose the accident described above happened long ago and your explicit memory system has since forgotten about many of the details, such as the fact that the horn had been stuck on. The sound of a horn now, many years later, is ignored by the explicit memory system. But if the emotional memory system has not forgotten, the sound of the horn, when it hits the amygdala, will trigger an emotional reaction. In a situation like this, you may find yourself in the throes of an emotional state that exists for reasons you do not quite understand. This condition of being emotionally aroused and not knowing why is all too common for most of us, and was, in fact, the key condition for which the Schachter-Singer theory of emotion tried to account. But in order for emotion to be aroused in this way, the implicit emotional memory system would have to be less forgetful than the explicit memory system.

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