BRAD BUCHSBAUM, Rotman Research Institute
Title: Neural Reactivation during Mental Replay: Aging, Amnesia, and Individual Differences
Ebbinghaus Empire Series 2015-2016
VIDEO RECORDING OF TALK
Abstract: A detailed conscious memory is a kind of revisitation of a past event. One might even say that a "perfect" memory is be one that perfectly recapitulates the phenomenological qualities of a previous perceptual experience. This relationship may also hold at the neural level -- i.e. during memory the brain's goal is reactivate a former brain state, a distributed pattern of neural activity. We have recently explored the extent to which this principle holds when human subjects must mentally replay complex multimodal episodes. I will present data from fMRI studies showing the relationship between the extent of "pattern reactivation" during memory and its link to age-related memory decline, introspective judgements of vividness, stimulus repetition, and in a case of developmental amnesia. I will show that memories defined by global activation patterns are indeed "similar" to their perceptual precursors, but they are not "pixel-perfect" replications. The systematic differences we see between perception and memory activity patterns relate to Roger Shepard's distinction between first and second-order similarity structure. Finally, I will discuss how the quality of a memory reactivation pattern is associated with the magnitude of univariate activity in a prefrontal, parietal, and medial temporal lobe areas.
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