Memory, Fear, and the Brain, Part I

Synaptic network

Synaptic network

Scientists are learning more about inaccurate recovered memories.

I recently watched a documentary about a murder committed in a store. The person who seemed to be the most reliable witness described the murderer falsely, even though she had definitely seen him. In the last few decades, scientists have discovered we can think we remember things that are proven to never have happened. The murder investigators were able to take into account that the witness might have remembered wrong largely because of psychologist Elizabeth Loftus’ research on how misinformation invades our memories. According to Professor Elizabeth Phelps at N.Y.U., “Loftus has been vilified for demonstrating that even the most vivid and detailed eyewitness accounts—a ‘recovered memory’ of sexual abuse, for example—can be inaccurate or completely false. The notion of the unreliability of memory has changed courtrooms in America, and it is completely owing to Elizabeth’s persistence in the face of a very harsh backlash.”

This blog is based on a New Yorker article, “Partial Recall—Can neuroscience help us rewrite our most traumatic memories?” by Michael Specter May 19, 2014.

Professor of neuroscience and psychiatry at Mount Sinai, Daniela Schiller, studies the biology of how emotional memories are formed. She hopes this will help people suffering from phobias, addiction, anxiety, and post-traumatic stress disorder (PTSD). Schiller, Phelps, and colleague Joseph LeDoux are leading investigators of the neural systems involved in learning, emotion, and memory. They and their colleagues want to find a way to “rewrite our darkest memories.”

According to “Partial Recall,” scientists are finding out that:

• implicit, procedural memories—how we ride a bike, tie our shoes, make an omelet—are distributed throughout the brain.

• emotional memories, like fear and love, are stored in the amygdala.

• conscious, visual memories—the date of a doctor’s appointment, the names of the Presidents—reside in the hippocampus, which also processes information about context.

“At N.Y.U. and other institutions, scientists have begun to identify genes that appear to make proteins that enhance memory, and genes that clearly interfere with it. These discoveries may lead to a new generation of drugs, some of which could help people remember and some that might help them forget.”

Scientists have also learned that “it takes a few hours for new experiences to complete the biochemical and electrical process that transforms them from short-term to long-term memories. Over time, they become stronger and less vulnerable to interference, and they eventually become imprinted onto the circuitry of our brains.” That process is called consolidation.

LeDoux, Phelps, and others mapped the neural circuitry responsible for many types of memory and found that for an old memory to be recalled, it had to retrace the pathways in which it originated. Under certain circumstances the memory seems to change. Scientists called this reconsolidation.

Eric Kandel, Columbia University neuroscientist, demonstrated how neurochemicals form short-term memories, and how more permanent memories are then consolidated into various parts of the brain.

• Neurons are programmed by our DNA and rarely change.

• Synapses, the small gaps between neurons, are highly mutable.

• Synaptic networks grow as we learn, often sprouting entirely new branches, based on the way neurotransmitters pass between neurons. According to Kandel, “The growth and maintenance of new synaptic terminals makes memory persist.”

Please see my Psychology Today blog on healing PTSD.

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