Why is the meaning of a sentence better remembered than its form? An fMRI study on the role of novelty‐encoding processes

Abstract

Episodic memory is based primarily on meaning. This is behaviorally well documented in studies on memory for prose, in which the meaning of novel sentences is typically well remembered but information pertaining to exact wording and syntax is not. The neural basis of this 'verbatim effect' is poorly understood. In the current fMRI study, we manipulated the novelty of sentences at different levels to test whether medial temporal lobe (MTL) regions that are known to play a critical role in verbal episodic encoding would respond preferentially to the novelty of sentence meaning. Fifteen participants were pre-familiarized with auditory sentences describing unique episodes. During scanning, they encountered sentences that were old, that contained a change in (i.e., were novel in terms of) syntactic relationships, that contained a change in semantic relationships, or that described an entirely novel episode. Subsequently, participants performed a recognition memory test for the different types of novel information encountered. Behavioral data confirmed the typical verbatim effect. Analyses of fMRI data revealed differential MTL activation in the left hippocampus and entorhinal cortex with a response profile across conditions that paralleled the behavioral results; the identified region responded selectively to those conditions that contained semantic novelty. Other regions, by contrast, showed a novelty response that did not share this selectivity. Our findings suggest that the verbatim effect can be linked to hippocampally-based novelty-assessment processes that operate based on semantic relationships.

Past Experience Modulates the Neural Mechanisms of Episodic Memory Formation

“…While our behavioral evidence favors the position that past experience in the form of repetitions, rather than novelty, benefits memory once confounding factors are removed, neuroimaging has consistently revealed greater medial temporal lobe (MTL) responses to novel relative to repeated materials (Tulving et al, 1996;Kirchhoff et al, 2000;Kumaran and Maguire, 2006;Poppenk et al, 2008). Because the MTL is known to be important for memory in general (Scoville and Milner, 1957), and because novelty and subsequent memory effects have been observed in the same hippocampal region (Kirchhoff et al, 2000), many researchers have linked MTL novelty responses to memory encoding.…”

The Franciscan Prayer Elicits Empathic and Cooperative Intentions in Atheists: A Neurocognitive and Phenomenological Enquiry

“…Some investigations using fMRI have revealed the activation of the hippocampus, the parahippocampal gyrus, and the perirhinal cortex involving the medial temporal lobe (MTL) when reading novelty texts or sentences. The cognitive functions related to these brain structures involve new memory formation, encodingretrieving processes of contextual and verbal information, and declarative memory about the meaning of the sentences or texts (O'Kane et al, 2005;Poppenk et al, 2008). Nevertheless, the activation of the MTL regions identified by neuroimaging strictly depends of cognitive tasks designed to explicitly evaluate what the participants remember about the text, or to request for a judge or thinking about the text during or immediately after the reading (Diana et al, 2007).…”

Preserved hippocampal novelty responses following anterior temporal‐lobe resection that impairs familiarity but spares recollection

“…Thirty-three sentences were selected from a larger stimulus set that had been used previously to examine novelty signals in the MTL (Poppenk et al, 2008). Each sentence described a unique episode (e.g., At the conclusion of the provocative comedian's outstanding performance, the enthusiastic crowd applauded with a standing ovation).…”

“…Subjects were presented with an intermixed list of 30 old sentences, each presented once during a novel block during scanning, and 30 new sentences not previously heard. The 30 new sentences were selected from the same larger set from which the experimental stimuli were chosen (Poppenk et al, 2008). The 60 sentences were presented auditorily in random order, and subjects were required to make self-paced old/new judgments.…”

“…Guided by the findings of Poppenk et al (2008) that were obtained with a variant of the current paradigm, we anticipated that the control group would show robust left-sided MTL activity, particularly, in the hippocampus, for novel as compared to repeated sentences. A random-effect analysis confirmed the expected novelty effect in the hippocampus [t(8) 5 9.039, P < 0.005, 506 mm 3 ].…”