Biomedical subjects

Joshua O S Goh

Publications and source records attributed to Joshua O S Goh.

3 recordsLinked to original sources

PubMed2006

Age-related changes in object processing and contextual binding revealed using fMR adaptation.

Using fMR adaptation, we studied the effects of aging on the neural processing of passively viewed naturalistic pictures composed of a prominent object against a background scene. Spatially distinct neural regions showing specific patterns of adaptation to objects, background scenes, and contextual integration (binding) were identified in young adults. Older adults did not show adaptation responses corresponding to binding in the medial-temporal areas. They also showed an adaptation deficit for objects whereby their lateral occipital complex (LOC) did not adapt to repeated objects in the context of a changing background. The LOC could be activated, however, when objects were presented without a background. Moreover, the adaptation deficit for objects viewed against backgrounds was reversed when elderly subjects were asked to attend to objects while viewing these complex pictures. These findings suggest that the elderly have difficulty with simultaneous processing of objects and backgrounds that, in turn, could contribute to deficient contextual binding.

Adult↗

PubMed2004

Cortical areas involved in object, background, and object-background processing revealed with functional magnetic resonance adaptation.

Previous work has suggested that object and place processing are neuroanatomically dissociated in ventral visual areas under conditions of passive viewing. It has also been shown that the hippocampus and parahippocampal gyrus mediate the integration of objects with background scenes in functional imaging studies, but only when encoding or retrieval processes have been directed toward the relevant stimuli. Using functional magnetic resonance adaptation, we demonstrated that object, background scene, and contextual integration of selectively repeated objects and background scenes could be dissociated during the passive viewing of naturalistic pictures involving object-scene pairings. Specifically, bilateral fusiform areas showed adaptation to object repetition, regardless of whether the associated scene was novel or repeated, suggesting sensitivity to object processing. Bilateral parahippocampal regions showed adaptation to background scene repetition, regardless of whether the focal object was novel or repeated, suggesting selectivity for background scene processing. Finally, bilateral parahippocampal regions distinct from those involved in scene processing and the right hippocampus showed adaptation only when the unique pairing of object with background scene was repeated, suggesting that these regions perform binding operations.

Adult↗

PubMed2004

Recognition memory for studied words is determined by cortical activation differences at encoding but not during retrieval.

Prior work has shown that when responses to incidentally encoded words are sorted, subsequently remembered words elicit greater left prefrontal BOLD signal change relative to forgotten words. Similarly, low-frequency words elicit greater activation than high-frequency words in the same left prefrontal regions, contributing to their better subsequent memorability. This study examined the relative contribution of encoding and retrieval processes to the correct recognition of target words. A mixture of high- and low-frequency words was incidentally encoded. Scanning was performed at encoding as well as during retrieval. During encoding, greater activation in the left prefrontal and anterior cingulate regions predicted a higher proportion of hits for low-frequency words. However, data acquired during recognition showed that word frequency did not modulate activation in any of the areas tracking successful recognition. This result demonstrates that under some circumstances, the recognition of studied words is determined purely by processes that are active during encoding. In contrast to the finding for hits, activation associated with correctly rejected foils was modulated by word frequency, being higher for high-frequency words in the left lateral parietal and anterior prefrontal regions. These findings were replicated in two further experiments, one in which the number of test items at recognition was doubled and another where encoding strength for high-frequency words was varied (once vs. 10 times). These results indicate that word frequency modulates activity in the left lateral parietal and anterior prefrontal regions contingent on whether the item involved is correctly recognized as a target or a foil. This observation is consistent with a dual process account of episodic memory.

Adult↗