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‘Where Do I Know You From?’ Recognition Shows Distinct Memory Processes

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New research from The University of Western Ontario suggests the sometimes eerie feeling experience when recognizing someone, yet failing to remember how or why, reveals important insight into how memory is wired in the human brain.

Western psychology graduate student Ben Bowles and psychology professor Stefan Köhler have found that this feeling of familiarity during recognition relies on a distinct brain mechanism and does not simply reflect a weak form of memory.

“Recognition based on familiarity can be contrasted with recognition when we spontaneously conjure up details about the episode in which we encountered the person before, such as where we met the person or when it happened,” explains Köhler.

The authors report that a rare form of brain surgery that can be highly effective for treatment of epilepsy can selectively impair the ability to assess familiarity.

“It is counterintuitive but makes a lot of sense from a theoretical perspective that familiarity can be affected, while the ability to recollect episodic detail is completely spared,” adds Köhler.

The research is based on Bowles’ Master’s thesis and was supported by a grant from the Canadian Institutes of Health Research (CIHR) to Dr. Köhler. It has important implications for understanding memory deficits in neurology, including in Alzheimer’s disease.

Proc Natl Acad Sci U S A. 2007 Oct 9;104(41):16382-7. Epub 2007 Sep 28.

Impaired familiarity with preserved recollection after anterior temporal-lobe resection that spares the hippocampus.

Bowles B, Crupi C, Mirsattari SM, Pigott SE, Parrent AG, Pruessner JC, Yonelinas AP, Köhler S.

Department of Psychology, University of Western Ontario, London, ON, Canada N6A 5C2.

It is well established that the medial-temporal lobe (MTL) is critical for recognition memory. The MTL is known to be composed of distinct structures that are organized in a hierarchical manner. At present, it remains controversial whether lower structures in this hierarchy, such as perirhinal cortex, support memory functions that are distinct from those of higher structures, in particular the hippocampus. Perirhinal cortex has been proposed to play a specific role in the assessment of familiarity during recognition, which can be distinguished from the selective contributions of the hippocampus to the recollection of episodic detail. Some researchers have argued, however, that the distinction between familiarity and recollection cannot capture functional specialization within the MTL and have proposed single-process accounts. Evidence supporting the dual-process view comes from demonstrations that selective hippocampal damage can produce isolated recollection impairments. It is unclear, however, whether temporal-lobe lesions that spare the hippocampus can produce selective familiarity impairments. Without this demonstration, single-process accounts cannot be ruled out. We examined recognition memory in NB, an individual who underwent surgical resection of left anterior temporal-lobe structures for treatment of intractable epilepsy. Her resection included a large portion of perirhinal cortex but spared the hippocampus. The results of four experiments based on three different experimental procedures (remember-know paradigm, receiver operating characteristics, and response-deadline procedure) indicate that NB exhibits impaired familiarity with preserved recollection. The present findings thus provide a crucial missing piece of support for functional specialization in the MTL.

Written by huehueteotl

October 26, 2007 at 9:19 pm

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