Differential effects of semantic processing on memory encoding

Developmental refinements to neural attentional state during semantic memory retrieval through adolescence

Despite the fact that attention undergoes protracted development, little is known about how it may support memory refinements in childhood and adolescence. Here, we asked whether people differentially focus their attention on semantic or perceptual information over development during memory retrieval. First, we trained a multivoxel classifier to characterize whole-brain neural patterns reflecting semantic versus perceptual attention in a cued attention task. We then used this classifier to quantify how attention varied in a separate dataset in which children, adolescents, and adults retrieved autobiographical, semantic, and episodic memories. All age groups demonstrated a semantic attentional bias during memory retrieval, with significant age differences in this bias during the semantic task. Trials began with a preparatory picture cue followed by a retrieval question, which allowed us to ask whether attentional biases varied by trial period. Adults showed a semantic bias earlier during the picture cues, whereas adolescents showed this bias during the question. Adults and adolescents also engaged different brain regions-superior parietal cortex and ventral visual regions, respectively-during preparatory picture cues. Our results demonstrate that retrieval-related attention undergoes refinement beyond childhood. These findings suggest that alongside expanding semantic knowledge, attention-related changes may support the maturation of factual knowledge retrieval.

Anterior Hippocampal Engagement during Memory Formation Predicts Subsequent False Recognition of Similar Experiences

People better remember experiences when they orient to meaning over surface-level perceptual features. Such an orientation-related memory boost has been associated with engagement of both hippocampus (HPC) and neocortex during encoding. However, less is known about the neural mechanisms by which a cognitive orientation toward meaning might also promote memory errors, with one open question being whether the HPC-a region traditionally implicated in precise memory formation-also contributes to behavioral imprecision. We used fMRI to characterize encoding-phase signatures as people oriented toward the meaning (story) versus perceptual style (artist) of storybook-style illustrations and then linked them to subsequent true and false memories. We found that story and artist orientation tasks were each associated with both unique univariate profiles and consistent neural states defined using multivoxel patterns. Linking these neural signatures to behavior, we found that greater medial pFC activation and alignment of neural patterns to the story (but not artist) state was related to subsequent memory success on a trial-by-trial basis. Moreover, among successfully remembered experiences, greater anterior HPC engagement at encoding was associated with a higher likelihood of related false recognitions, consistent with the encoding of broad traces in this region. Interestingly, these effects did not reliably vary by cued orientation. These results suggest that, irrespective of the cued encoding orientation, neocortical and hippocampal mechanisms associated with orienting to meaning (story) over perceptual (artist) features may support memory, with the formation of generalizable memories being a specialty of anterior HPC.

Spatiotemporal Dynamics of Affective and Semantic Valence Among Women

As an important dimension of emotional assessment, valence can refer to affective valence reflecting an emotional response, or semantic valence reflecting knowledge about the nature of a stimulus. A previous study has used repeated exposure to separate these two similar cognitive processes. Here, for the first time, we compared the spatiotemporal dynamics of the affective and semantic modes of valence by combining event-related potentials with repeated exposure. Forty-seven female participants were assigned to the feeling-focused and semantic-focused groups and thereafter repeatedly viewed the pictures selected for the study. Self-report behavioral results showed that post-test scores were significantly lower than pre-test scores in the feeling-focused group, while the differences between the two tests were not significant in the semantic-focused group. At the neural level, N2 amplitudes decreased and early late positive potential amplitudes increased in both groups, suggesting that the participants perceived the repeated pictures more fluently and retrieved the traces of the stimulus spontaneously regardless of the valence they judged. However, the late positive potential amplitudes in anterior areas and the activity of the middle frontal gyrus were attenuated in the feeling-focused group; however, this component in posterior areas and the activity of the precentral gyrus were increased in the semantic-focused group. Therefore, the processes of affective and semantic valence are similar in the early stages of image perception and retrieval, while in the later stage of valence judgment, these processes show different brain activation patterns. The results provide electrophysiological evidence for the differences in psychological processes when judging the two modes of valence.

Depth of Processing and Age Differences

The present article is aimed to investigate whether there are any differences between youngsters and adults in their working and long-term memory functioning. The theory of Depth of Processing (Craik and Lockhart in J Verbal Learning Verbal Behav 11:671-684, 1972) discusses the varying degrees of strengths of memory traces as the result of differential levels of processing on the retrieved input. Additionally, they claim that there are three levels of visual, auditory and semantic processes applied on the stimuli in the short-term memory leading to discrepancy in the durability of the memory traces and the later ease of recall and retrieval. In the present article, it is tried to demonstrate if there are evidences of more durable memory traces formed after semantic, visual and auditory processions of the incoming language data in two groups of (a) children in their language learning critical age and (b) youngsters who have passed the critical age period. The comparisons of the results made using two-way ANOVAs revealed the superiority of semantic processing for both age groups in recall, retention and consequently recognition of the new English vocabularies by EFL learners.

A new semantic list learning task to probe functioning of the Papez circuit

INTRODUCTION

List learning tasks are powerful clinical tools for studying memory, yet have been relatively underutilized within the functional imaging literature. This limits understanding of regions such as the Papez circuit that support memory performance in healthy, nondemented adults.

METHOD

The current study characterized list learning performance in 40 adults who completed a semantic list learning task (SLLT) with a Brown-Peterson manipulation during functional magnetic resonance imaging (fMRI). Cued recall with semantic cues and recognition memory were assessed after imaging. Internal reliability, convergent, and discriminant validity were evaluated.

RESULTS

Subjects averaged 38% accuracy in recall (62% for recognition), with primacy but no recency effects observed. Validity and reliability were demonstrated by showing that the SLLT was correlated with the California Verbal Learning Test (CVLT), but not with executive functioning tests, and by high intraclass correlation coefficient across lists for recall (.91). fMRI measurements during encoding (vs. silent rehearsal) revealed significant activation in bilateral hippocampus, parahippocampus, and bilateral anterior and posterior cingulate cortex. Post hoc analyses showed increased activation in anterior and middle hippocampus, subgenual cingulate, and mammillary bodies specific to encoding. In addition, increasing age was positively associated with increased activation in a diffuse network, particularly frontal cortex and specific Papez regions for correctly recalled words. Gender differences were specific to left inferior and superior frontal cortex.

CONCLUSIONS

This is a clinically relevant list learning task that can be used in studies of groups for which the Papez circuit is damaged or disrupted, in mixed or crossover studies at imaging and clinical sites.

Interdisciplinary perspectives on the development, integration, and application of cognitive ontologies

We discuss recent progress in the development of cognitive ontologies and summarize three challenges in the coordinated development and application of these resources. Challenge 1 is to adopt a standardized definition for cognitive processes. We describe three possibilities and recommend one that is consistent with the standard view in cognitive and biomedical sciences. Challenge 2 is harmonization. Gaps and conflicts in representation must be resolved so that these resources can be combined for mark-up and interpretation of multi-modal data. Finally, Challenge 3 is to test the utility of these resources for large-scale annotation of data, search and query, and knowledge discovery and integration. As term definitions are tested and revised, harmonization should enable coordinated updates across ontologies. However, the true test of these definitions will be in their community-wide adoption which will test whether they support valid inferences about psychological and neuroscientific data.

A parametric investigation of pattern separation processes in the medial temporal lobe

The hippocampus is thought to be involved in memory formation and consolidation, with computational models proposing the process of pattern separation as a means for encoding overlapping memories. Previous research has used semantically related targets and lures to investigate hippocampal responses to mnemonic interference. Here, we attempted to define the response function of the human hippocampus and its inputs during pattern separation by parametrically varying target-lure similarity in a continuous recognition task. We also investigated the effect of task demands (intentional vs incidental encoding) on pattern separation processes. We collected functional magnetic resonance imaging data while participants were shown a series of objects. In the intentional paradigm, participants identified objects as "new" (novel stimuli), "old" (exact repetitions), or "rotated" (previously seen objects that were subsequently rotated by varied degrees). In the incidental paradigm, participants were shown the same stimuli but identified objects as "toy" or "not toy." Activation in the hippocampus was best fit with a power function, consistent with predictions made by computational models of pattern separation processes in the hippocampus. The degree of pattern separation was driven by the information most relevant to the task: pattern separation was seen in the left hippocampus when semantic information was more important to the task and seen in the right hippocampus when spatial information was more important. We also present data illustrating that top-down processes modulate activity in the ventral visual processing stream.

Cortical correlates of self-generation in verbal paired associate learning

Behavioral studies have shown that verbal information is better retained when it is self-generated rather than read (learned passively). We used fMRI and a paired associates task to examine brain networks underlying self-generated memory encoding. Subjects were 49 healthy English speakers ages 19-62 (30 female). In the fMRI task, related word pairs were presented in a "read" condition, where subjects viewed both words and read the second word aloud, or a "generate" condition, where the second word was presented with only the first letter and the subject was required to generate the word. Thirty word pairs were presented in each condition. After the fMRI scan, words that were read or generated were presented, each with two foils, in a forced-choice recognition task. On the recognition post-test, words from the "generate" condition were more correctly recognized than from the "read" condition (80.0% for generated words versus 72.0% for read words; t(48)=5.17, p<0.001). FMRI revealed increased activation for generate>read in inferior/middle frontal gyri bilaterally (L>R), anterior cingulate, and caudate nucleus and the temporo-parietal-occipital junction bilaterally. For the "read" condition, better subsequent memory performance across individual subjects was positively correlated with activation in the cuneus bilaterally. In the "generate" condition, better subsequent memory performance was positively correlated with activation in the left superior temporal gyrus. These results suggest that self-generation improves memory performance, that enhanced cortical activation accompanies self-generated encoding, and that recruitment of a specific brain network underlies self-generated encoding. The findings may have implications for the development of procedures to enhance memory performance.