By Walter Glannon, PhD
Walter Glannon, PhD, is Professor of Philosophy at the University of Calgary. He is the author of Bioethics and the Brain (Oxford, 2007) and Brain, Body and Mind: Neuroethics with a Human Face (Oxford, 2011) and editor of Free Will and the Brain: Neuroscientific, Philosophical and Legal Perspectives (Cambridge, 2015).
Neuroscientists can measure changes in the brain associated with different types of memory. Recent experiments on rodents have shown that memories can be manipulated. In one experiment, researchers implanted a false fear memory in a mouse brain, causing it to elicit a fear response to a stimulus to which it was not actually exposed . In a different experiment, researchers electrically stimulated place cells in a mouse hippocampus as well as cells in the reward system during sleep. This induced learned behavior where mice linked a specific location to a reward . This type of manipulation may eventually serve a therapeutic purpose in humans. Psychiatric disorders including subtypes of major depression, generalized anxiety, phobia, panic and especially post-traumatic stress disorder (PTSD) can be conceptualized as disorders of memory content. In such a model, the neural representation of the emotional component of the memory, or emotional trace, of a traumatic experience persists beyond any adaptive purpose. This causes dysregulation in the fear memory system, resulting in pathology associated with impaired cognitive, affective and volitional functions [3, 4]. I’d also like to propose that unlike disorders of memory capacity, such as anterograde or retrograde amnesia, where one cannot form or retain memories, the problem in disorders of memory content, like PTSD, is the inability to get rid of or “extinguish” them.
The source of this dysfunction in the fear memory system is neural changes employed during the consolidation and reconsolidation of an emotionally charged memory of fear-inducing stimuli.