PubMed Health⌕ Search

Biomedical subjects

Jason P Mitchell

Publications and source records attributed to Jason P Mitchell.

7 recordsLinked to original sources
PubMed2003

Multiple routes to memory: distinct medial temporal lobe processes build item and source memories.

A central function of memory is to permit an organism to distinguish between stimuli that have been previously encountered and those that are novel. Although the medial temporal lobe (which includes the hippocampus and surrounding perirhinal, parahippocampal, and entorhinal cortices) is known to be crucial for recognition memory, controversy remains regarding how the specific subregions within the medial temporal lobe contribute to recognition. We used event-related functional MRI to examine the relation between activation in distinct medial temporal lobe subregions during memory formation and the ability (i) to later recognize an item as previously encountered (item recognition) and (ii) to later recollect specific contextual details about the prior encounter (source recollection). Encoding activation in hippocampus and in posterior parahippocampal cortex predicted later source recollection, but was uncorrelated with item recognition. In contrast, encoding activation in perirhinal cortex predicted later item recognition, but not subsequent source recollection. These outcomes suggest that the subregions within the medial temporal lobe subserve distinct, but complementary, learning mechanisms.

Adolescent↗
PubMed2003

Gender differences in implicit weight identity.

OBJECTIVE: This study examined gender differences in explicit and implicit attitudes toward overweight and explicit and implicit weight identity. METHOD: Normal weight women (n=22) and men (n=20) and overweight women (n=20) and men (n=21) completed the Implicit Association Test and portions of the Eating Disorders Questionnaire. RESULTS: Although explicit and implicit anti-fat attitudes were ubiquitous, gender differences emerged for weight identity. Both men and women provided accurate explicit appraisals of their weight status. However, men implicitly identified themselves as light regardless of actual weight status. Women's implicit weight identity was associated with their actual weight status, explicit weight appraisal, and implicit self-esteem. DISCUSSION: These findings may provide additional insight into why men are underrepresented among those seeking weight loss and why women are at increased risk for developing eating disorders.

Adult↗
PubMed2003

Feeling-of-knowing in episodic memory: an event-related fMRI study.

An individual may fail to recall an item from memory but still feel that it would be recognized on a later test, a retrieval state termed the "feeling-of-knowing" (FOK). In this study we used event-related fMRI and the FOK to examine both encoding- and retrieval-related factors that are associated with different levels of recall performance: successful retrieval of a previously studied item, retrieval failure accompanied by the FOK, and retrieval failure without any FOK. The results revealed one predominant pattern of retrieval-related activation: an intermediate level of activation for FOK-less than that associated with successful recall and greater than that associated with unsuccessful recall (frontal and left parietal cortices). Two further patterns were also observed: greater activation for both successful recall and FOK than for unsuccessful recall (left midlateral prefrontal cortex) and greater activation for successful recall than for both FOK and unsuccessful recall (left MTL). Analysis of encoding trials conditional upon subsequent retrieval success revealed a pattern of activation that appeared to predict subsequent recall, but which further analysis indicated to be a better predictor of subsequent recognition. These results provide evidence that the phenomenology of graded recall is represented neurally in frontal and parietal cortices, but that activation at encoding may not precipitate the different levels of recall experience.

Adolescent↗
PubMed2002

Distinct neural systems subserve person and object knowledge.

Studies using functional neuroimaging and patient populations have demonstrated that distinct brain regions subserve semantic knowledge for different classes of inanimate objects (e.g., tools, musical instruments, and houses). What this work has yet to consider, however, is how conceptual knowledge about people may be organized in the brain. In particular, is there a distinct functional neuroanatomy associated with person knowledge? By using event-related functional magnetic resonance imaging (fMRI), we measured neural activity while participants made semantic judgments about people or objects. A unique pattern of brain activity was associated with person judgments and included brain regions previously implicated in other aspects of social-cognitive functioning: medial prefrontal cortex, superior temporal cortex, intraparietal sulcus, and fusiform gyrus. These regions were generally marked by relatively little change from baseline brain activity for person judgments along with significant deactivations for object judgments. Together, these findings support the notion that person knowledge may be functionally dissociable from other classes of semantic knowledge within the brain.

Adolescent↗
PubMed2002

Working memory and the suppression of reflexive saccades.

Conscious behavioral intentions can frequently fail under conditions of attentional depletion. In attempting to trace the cognitive origin of this effect, we hypothesized that failures of action control--specifically, oculomotor movement--can result from the imposition of fronto-executive load. To evaluate this prediction, participants performed an antisaccade task while simultaneously completing a working-memory task that is known to make variable demands on prefrontal processes (n-back task, see Jonides et al., 1997). The results of two experiments are reported. As expected, antisaccade error rates were increased in accordance with the fronto-executive demands of the n-back task (Experiment 1). In addition, the debilitating effects of working-memory load were restricted to the inhibitory component of the antisaccade task (Experiment 2). These findings corroborate the view that working memory operations play a critical role in the suppression of prepotent behavioral responses.

Attention↗
PubMedDate not supplied

Directed remembering: subliminal cues alter nonconscious memory strategies.

Much research on memory function has focused on changes in recognition performance brought about by differences in the processes engaged during encoding. In most of this work, participants either receive explicit instructions to remember particular items or they perform orienting (i.e., encoding) tasks that support different levels of memory performance. In daily life, however, the retention or dismissal of information often occurs without conscious intent, thereby suggesting an alternative, nonconscious route through which purposive remembering and forgetting can occur. Based on this line of reasoning, we speculated that recognition performance in a standard item-based forgetting paradigm may be moderated by subliminal cues that trigger the automatic activation of different mnemonic strategies. We report the results of two experiments that supported this prediction. In each experiment, the basic item-based forgetting effect was replicated, but via the subliminal presentation of "remember" and "forget" cues. In addition, cue-dependent differences in memory performance were traced to the operation of a covert rehearsal mechanism during encoding. We consider the implications of these findings for the non-conscious#10; operation of memory processes in everyday life.

Adult↗