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Hippocampal activation during processing of previously seen visual stimulus pairs
Dost Ongür1, Martin Zalesak, Anthony P Weiss
1Schizophrenia and Bipolar Disorder Program, McLean Hospital, 115 Mill St., AB 347, Belmont, MA, USA. dongur@partners.org
Psychiatry Research
|August 2, 2005
Summary
The hippocampus, crucial for memory, activates more when distinguishing familiar visual pairs than novel ones. This right hippocampal activity is linked to recognizing previously rewarded stimulus relationships.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Neuroimaging
Background:
- The hippocampus plays a role in novelty detection and processing stimulus conjunctions.
- Understanding hippocampal function in stimulus-relationship discrimination is essential.
Purpose of the Study:
- To investigate hippocampal activation during the discrimination of stimulus-stimulus relationships in novel versus familiar visual pairs.
- To determine if the hippocampus is activated by recognizing previously rewarded stimuli within these pairs.
Main Methods:
- Functional magnetic resonance imaging (fMRI) was used in 15 healthy subjects.
- Subjects discriminated relationships in novel versus familiar visual stimulus pairs, identifying previously rewarded stimuli.
Main Results:
- Significantly greater activation was observed in the right hippocampus when discriminating previously seen pairs compared to novel pairs.
- This right hippocampal activation was consistent across individual subjects.
- Activation was independent of stimulus novelty, reward contingency, or task instructions.
Conclusions:
- The right hippocampus is activated during the discrimination of previously seen stimulus-stimulus relationships.
- This hippocampal activation correlates with activity in the anteromedial thalamus, cingulate cortex, and contralateral hippocampus.