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Regional brain activity during shape recognition impaired by a scopolamine challenge to encoding
A M Rosier1, L Cornette, P Dupont
1Laboratorium voor Neuro- en Psychofysiologie, KU Leuven, Medical School, Campus Gasthuisberg, Leuven, Belgium. Anne-Marie.Rosier@med.KULeuven.ac.be
The European Journal of Neuroscience
|November 17, 1999
Summary
Scopolamine impairs memory encoding, decreasing fusiform cortex activity during shape recognition but increasing thalamic activity, similar to previous findings with diazepam. This suggests distinct roles for these brain regions in memory storage and retrieval.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Neuroimaging
Background:
- Previous studies indicated fusiform and thalamic activity during object recognition is modulated by memory challenges.
- Impaired recognition due to diazepam (impaired storage) or perceptual challenge (impaired retrieval) affected these regions differently.
- Fusiform activity decreased with impaired recognition, while thalamic activity increased only with impaired storage.
Purpose of the Study:
- To investigate the effect of scopolamine, a memory storage impairer, on regional cerebral blood flow during shape recognition.
- To test hypotheses that fusiform activation reflects stimulus matching and thalamic activation reflects retrieval attempts.
- To compare scopolamine's effects with previous findings using diazepam.
Main Methods:
- Positron emission tomography (PET) was used to measure regional cerebral blood flow.
- Participants underwent a scopolamine challenge during the encoding phase of a shape recognition task.
- Recognition of abstract visual shapes was assessed 3 days after encoding.
Main Results:
- Scopolamine challenge modulated activity in the fusiform cortex and thalamus, mirroring effects seen with diazepam.
- Fusiform cortex activity decreased during recognition following scopolamine, correlating linearly with performance.
- Thalamic activation increased after impaired encoding, suggesting heightened retrieval effort.
Conclusions:
- Scopolamine's impact on shape recognition network activity parallels diazepam's, despite different neurochemical pathways.
- Findings support the hypothesis that fusiform activity relates to stimulus-representation matching and thalamic activity to retrieval processes.
- Increased activity in the intraparietal sulcus may reflect compensatory visuospatial attention.