Hippocampal damage impairs recognition memory broadly, affecting both parameters in two prominent models of memory

Abstract

Declarative memory is thought to rely on two processes: recollection and familiarity. Recollection involves remembering specific details about the episode in which an item was encountered, and familiarity involves simply knowing that an item was presented even when no information can be recalled about the episode itself. There has been debate whether the hippocampus supports only recollection or whether it supports both processes. We approached this issue in a relatively theory-neutral way by fitting two prominent models that have been used to describe recognition memory: dual process signal detection and unequal variance signal detection. Both models yield two parameters of interest when fit to recognition memory data. The dual process signal detection model yields estimates of recollection ( r ) and familiarity ( d′ ). The unequal variance signal detection model yields estimates of the ratio of the variance of target and foil memory strength distributions (σ target /σ foil ) and the difference in the means of the two distributions ( d ). We asked how the two parameters of each model were affected by hippocampal damage. We tested five patients with well-characterized bilateral lesions thought to be limited to the hippocampus and age-matched controls. The patients exhibited a broad memory deficit that markedly reduced the value of both parameters in both models. In addition, the pattern of results exhibited by the patients was recapitulated in healthy controls as the delay between learning and testing was extended. Thus, hippocampal damage impairs both component processes of recognition memory.

The human hippocampus contributes to both the recollection and familiarity components of recognition memory

“…An across-subject regression model of We next implemented a behavioral model of memory to obtain more specific and psychologically meaningful metrics of recognition memory performance. We chose the dual-process signal detection model (DPSM) of recognition memory because of its simplicity and widespread application (1,4,12,17,18,35), and to answer a key question of recognition memory: is hippocampal activity specific to recollection (2, 36), or does it correspond to both the recollection and familiarity processes (4, 25)?…”

“…By this account, humans and animals are able to compensate for the loss of the hippocampus, and thus recollection, by relying on familiarity (15-18). A contrasting view holds that the hippocampus instead contributes to both recollection and familiarity, thus explaining why hippocampal damage is associated with severe impairment of both processes and consequently the overall recognition performance (4,8,19,20). Whether neural circuitry underlying familiarity and recollection lie within the hippocampus has also been extensively studied using functional MRI (fMRI) (21).…”

“…Whereas it is well known that the hippocampus plays a crucial role in human recall memory, the role of the hippocampus in recognition memory remains surprisingly controversial (1)(2)(3)(4). A number of studies have reported that bilateral hippocampal injury in humans causes impaired recall, whereas recognition remains intact (5).…”

A novel approach to an old problem: Analysis of systematic errors in two models of recognition memory

“…These data sets were selected because they are based on sufficient data to allow for individual model fitting and because the methods were comparable. The data represent results from a laboratory that has generally supported the CDP model (Dede, Wixted, Hopkins & Squire, 2013), a laboratory that has generally supported the HTDP model (Koen & Yonelinas, 2010), and a neutral laboratory (Van Zandt, 2000). …”

“…To test for such systematic error, a series of one-sample t -tests determined whether there was significant non-zero error at each confidence level within each of the four data sets. Errors were deemed systematic if they were identified as significant in all four data sets (Dede et al, 2013; Koen & Yonelinas, 2010, 4-sec condition; Koen & Yonelinas, 2010, 1-sec condition; Van Zandt, 2000). …”