In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 96, No. 4 ( 1999-02-16), p. 1794-1799
Abstract:
In all cognitive tasks, general task-related processes operate
throughout a given task on all items, whereas specific item-related processes operate differentially on individual items. In typical
functional neuroimaging experiments, these two sets of processes have usually been confounded. Herein we report a combined positron emission
tomography and event-related potential (ERP) experiment that was designed to distinguish between neural correlates of task-related and
item-related processes of memory retrieval. Two retrieval tasks, episodic and semantic, were crossed with episodic (old/new) and
semantic (living/nonliving) properties of individual items to yield evidence of regional brain activity associated with task-related
processes, item-related processes, and their interaction. The results showed that episodic retrieval task was associated with increased blood
flow in right prefrontal and posterior cingulate cortex, as well as with a sustained right-frontopolar-positive ERP, but that the semantic
retrieval task was associated with left frontal and temporal lobe activity. Retrieval of old items was associated with increased blood
flow in the left medial temporal lobe and with a brief late positive ERP component. The results provide converging hemodynamic and
electrophysiological evidence for the distinction of task- and item-related processes, show that they map onto spatially and
temporally distinct patterns of brain activity, and clarify the hemispheric encoding/retrieval asymmetry (HERA) model of prefrontal
encoding and retrieval asymmetry.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.96.4.1794
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
1999
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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