Effects of modality on the neural correlates of encoding processes supporting recollection and familiarity

Abstract

Prior research has demonstrated that the neural correlates of successful encoding ("subsequent memory effects") partially overlap with neural regions selectively engaged by the on-line demands of the study task. The primary goal of the present experiment was to determine whether this overlap is associated solely with encoding processes supporting later recollection, or whether overlapping subsequent memory and study condition effects are also evident when later memory is familiarity-based. Subjects (N = 17) underwent fMRI scanning while studying a series of visually and auditorily presented words. Memory for the words was subsequently tested with a modified Remember/Know procedure. Auditorily selective subsequent familiarity effects were evident in bilateral temporal regions that also responded preferentially to auditory items. Although other interpretations are possible, these findings suggest that overlap between study condition-selective subsequent memory effects and regions selectively sensitive to study demands is not uniquely associated with later recollection. In addition, modality-independent subsequent memory effects were identified in several cortical regions. In every case, the effects were greatest for later recollected items, and smaller for items later recognized on the basis of familiarity. The implications of this quantitative dissociation for dual-process models of recognition memory are discussed.

Figure 1.

Performance on the subsequent memory test. (A) Visual, (B) auditory.

Figure 2.

(Upper) Modality-independent subsequent memory effects (main effect of memory [P < 0.001] exclusively masked with subsequent memory by modality interaction [P < 0.1]). Effects are rendered onto a single subject template brain (left) and projected onto a section of the normalized average anatomical image (right). (Lower) Bar plots show parameter estimates (in arbitrary units) for recollected (R), familiar (4), and forgotten (3/2/1) trials of peak voxels for effects localized in (A) left IPS (−30, −69, 42), (E,F) left (−51, −48, −21) and right fusiform cortex (51, −48, −18), (B) left middle frontal gyrus (−27, 9, 51), (C) left posterior inferior frontal gyrus (−45, 18, 15), (D) left lateral orbital gyrus (−39, 39, −18), and (G) left hippocampus/parahippocampal cortex (−39, −27, −18).

Figure 3.

(Upper) Auditorily selective subsequent familiarity effects (P < 0.01) that overlap regions demonstrating auditorily selective activity (P < 0.001). (Lower) Bar plots of mean parameter estimates (in arbitrary units) for recollected, familiar, and forgotten study items in left superior temporal sulcus and right superior temporal gyrus.

Figure 4.

(Upper) Visually selective subsequent recollection effects projected onto sections of the normalized across-subjects averaged anatomical image. (Lower) Bar plots of mean parameter estimates (in arbitrary units) for recollected (R), familiar (4), and forgotten (3/2/1) trials in right superior frontal gyrus, left superior frontal sulcus, and left insula.

Figure 5.

(Upper) Auditorily selective subsequent familiarity effects projected onto sections of the normalized across-subjects averaged anatomical image. (Lower) Bar plots of mean parameter estimates (in arbitrary units) for recollected (R), familiar (4), and forgotten (3/2/1) trials in (A) left perirhinal cortex, (B) left middle occipital gyrus, (C) right middle occipital gyrus, and (D) right inferior occipital gyrus.