Structural plasticity and memory.
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Animals↗
Biomedical subjects
Joseph LeDoux
Publications and source records attributed to Joseph LeDoux.
The emotional brain, fear, and the amygdala.
1. Considerable progress has been made over the past 20 years in relating specific circuits of the brain to emotional functions. Much of this work has involved studies of Pavlovian or classical fear conditioning, a behavioral procedure that is used to couple meaningless environmental stimuli to emotional (defense) response networks. 2. The major conclusion from studies of fear conditioning is that the amygdala plays critical role in linking external stimuli to defense responses. 3. Before describing research on the role of the amygdala in fear conditioning, though, it will be helpful to briefly examine the historical events that preceded modern research on conditioned fear.
Amygdala↗
The self: clues from the brain.
Can we find a way of thinking about the self that is compatible with modern neuroscience? I think we can. First of all, we have to recognize that "the self" is not the same as "the conscious self," since much of who we are as individuals takes place out of conscious awareness. Second, we have to accept that some aspects of the self, especially the unconscious aspects, occur in and can be studied in other species, allowing us to relate these aspects of the self to detailed brain mechanisms. Finally, it also helps to think of the self in terms of memory. Obviously, much of who we are is based on memories learned through personal experience, including both conscious or explicit memories and unconscious or implicit memories. This is particularly important since much progress has been made in relating memory to the cells and synapses of the brain. By viewing the self as a network of memories the effort to relate the self to the brain can build on this progress. Emphasizing memory and experience does not take away from the fact that our genetic history also contributes to who we are. In fact, genes and experience, or nature and nurture, are, in the end, not different things, but different ways of doing the same thing-wiring the synapses of our brain. In many ways, the self is synaptic. This synaptic view of the self is not meant as a challenge to other views, such as spiritual, cultural, or psychological views. It is instead, just a way of understanding how these other aspects of who we are relate, deep down, to the brain.
Animals↗
Single-unit activity in the lateral nucleus of the amygdala and overlying areas of the striatum in freely behaving rats: rates, discharge patterns, and responses to acoustic stimuli.
Acoustic responses of single units were examined in awake, freely behaving rats in the lateral nucleus of the amygdala (AL). Recordings were made from a movable bundle of 9 microwires. Most cells had very low rates of spontaneous activity (about 3 spikes/s average). Firing rates increased during sleep states. Short-latency auditory responses (12-25 ms) were found in the dorsal subnucleus (ALd) of the AL. Cells in the ALd most typically responded in a sustained fashion. Some of the cells in the ALd showed preferences for high frequencies, tone bursts, or frequency-modulated stimuli with center frequencies above 12 kHz. Response latencies were considerably longer in other areas of the amygdala. Our results corroborate the main findings of a previous study (F. Bordi & J. LeDoux, 1992) that examined the acoustic response properties of single cells in the AL in anesthetized rats. Together the findings from awake and anesthetized rats provide the most precise information about sensory processing in amygdala neurons available to date.
Amygdala↗