Repetition Suppression and Multi-Voxel Pattern Similarity Differentially Track Implicit and Explicit Visual Memory

Abstract

Repeated exposure to a visual stimulus is associated with corresponding reductions in neural activity, particularly within visual cortical areas. It has been argued that this phenomenon of repetition suppression is related to increases in processing fluency or implicit memory. However, repetition of a visual stimulus can also be considered in terms of the similarity of the pattern of neural activity elicited at each exposure-a measure that has recently been linked to explicit memory. Despite the popularity of each of these measures, direct comparisons between the two have been limited, and the extent to which they differentially (or similarly) relate to behavioral measures of memory has not been clearly established. In the present study, we compared repetition suppression and pattern similarity as predictors of both implicit and explicit memory. Using functional magnetic resonance imaging, we scanned 20 participants while they viewed and categorized repeated presentations of scenes. Repetition priming (facilitated categorization across repetitions) was used as a measure of implicit memory, and subsequent scene recognition was used as a measure of explicit memory. We found that repetition priming was predicted by repetition suppression in prefrontal, parietal, and occipitotemporal regions; however, repetition priming was not predicted by pattern similarity. In contrast, subsequent explicit memory was predicted by pattern similarity (across repetitions) in some of the same occipitotemporal regions that exhibited a relationship between priming and repetition suppression; however, explicit memory was not related to repetition suppression. This striking double dissociation indicates that repetition suppression and pattern similarity differentially track implicit and explicit learning.

The relationship between repetition suppression and face perception

“…Indeed, recent neuroimaging studies found that trials leading to behavioral priming also lead to fMRIa in the fusiform and occipital face areas (FFA and OFA) of the human brain . Similarly, repetition priming has also been related to fMRIa in several cortical areas for objects and scenes, including prefrontal, parietal, and occipito-temporal ones (Soldan et al 2010;Ward et al 2013). However, a clear causal relationship could not been determined between behavioral priming and RS as of today.…”

Noninvasive Functional and Anatomical Imaging of the Human Medial Temporal Lobe

“…These data suggest that the success of hippocampally mediated encoding of event details is influenced by, or at least covaries with, the strength or fidelityof the corresponding cortical representations. We expect that these, and other recent MVPA and RSA observations (Johnson et al 2009;McDuff et al 2009;Rissman et al 2010;Ward et al 2013), will be the first of many instances, in which the application of multivariate analytic techniques, combined with the spatial resolution of fMRI, allows researchers to make critical progress on open questions about the neurobiological mechanisms governing memory.…”

“…In particular, RSA analyses of fMRI encoding data suggest that, in some contexts, representational stability may be beneficial to later remembering (Xue et al 2010;Ward et al 2013; but see Wagner et al 2000), demonstrating that greater pattern similarity of an item's neural representations across multiple encoding trials predicts better subsequent memory for the item. Although some questions remain (Xue et al 2013;Davis et al 2014), researchers are now positioned to measure, at the individual trial level and within an individual human brain, the large-scale distributed neural representations that underlie important aspects of memory behavior.…”

Steady-state and dynamic network modes for perceptual expectation

“…5). It has been reported that IPL_L is involved in a goal-directing function, which causes repetition suppression in human studies181920 or the prediction repetition priming phenomenon21.…”