ScienceDaily (here) has an item: Lee, Blumenfeld, D’Esposito; Disruption of Dorsolateral But Not Ventrolateral Prefrontal Cortex Improves Unconscious Perceptual Memories; inJournal of Neuroscience, 2013. It looks at the mechanism of over-thinking.



There are two types of memory (at least): explicit, conscious memory, also called declarative; and, implicit, not conscious memory, also called procedural. It has been noted for some time that preformance in sports, music and the like suffers when the performer thinks consciously too much. Procedural memory works best if the action is just done without trying to consciously control the action.



Two previous brain studies have shown that taxing explicit memory resources improved recognition memory without awareness. The results suggest that implicit perceptual memory can aid performance on recognition tests. So Lee and his colleagues decided to test whether the effects of the attentional control processes associated with explicit memory could directly interfere with implicit memory.”



Lee disrupted activity in two parts of the prefrontal cortex to see which affected recognition. Disrupting the dorsolateral PFC improved memory. This pointed to explicit memory processing taking control of visual information processing and so interfering with implicit memory processes using the same visual information.



Here is the abstract:


Attentive encoding often leads to more accurate responses in recognition memory tests. However, previous studies have described conditions under which taxing explicit memory resources by attentional distraction improved perceptual recognition memory without awareness. These findings lead to the hypothesis that explicit memory processes mediated by the prefrontal cortex (PFC) can interfere with memory processes necessary for implicit recognition memory. The present study directly tested this hypothesis by applying transcranial magnetic stimulation separately over either dorsolateral (DLPFC) or ventrolateral PFC (VLPFC) in humans before performance of a visual memory task. Disruption of DLPFC function led to improvement in recognition accuracy only in responses in which the participant’s awareness of memory retrieval was absent. However, disruption of VLPFC function led to subtle shifts in recollection and familiarity accuracy. We conclude that explicit memory processes mediated by the DLPFC can indirectly interfere with implicit recognition memory.



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