Joseph E LeDoux

Memory and Emotion

My lab's research is aimed at understanding how the brain learns and stores information about danger. Using Pavlovian threat (fear) conditioning in rats, we have mapped pathways through which sensory stimuli enter and flow through the brain in during of learning. This work has implicated specific circuits in within the amygdala as essential for the formation of threat memories. The same brain system underlies threat learning in humans. The detailed mechanisms, which can only be uncovered through animal studies are thus applicable to understanding threat processing in the human brain.

Some of the techniques we use to explore threat memory in the brain include pharmacological and viral-based (DREADD and optogenetic) manipulations of brain chemistry, brain lesions, neuroanatomical tract tracing at the light and electron microscopic level, single unit and field recordings of neural activity in awake and anesthetized animals, whole cell recordings in in vitro brain slices, and fMRI in healthy human volunteers and in patients with fear/anxiety disorders.

Ongoing work is exploring the following questions. Is the same basic system that underlies the conditioning and expression reactive responses, such as freezing behavior, also involved in controlling instrumental responses, such as escape and avoidance, in dangerous situations? To what extent can threat memories be changed through experience, and can these approaches be used to help treat people with fear and anxiety disorders? What are the mechanisms through which conscious emotional feelings, as opposed to behavioral or autonomic responses, come about?

A key issue is the role of "fear" in so-called fear conditioning. Fear, as commonly used, refers to the subjective feeling we experience when in danger. The extent to which animals, aside from humans, have such experiences is not easily determined. We should, therefore, not search for fear or other human emotions in the brains of other animals, but instead should ask whether processes that are present in the brains of other animals are also present in humans. This will help avoid conflation of fearful feelings with more basic survival mechanisms that are widely shared across species.