Effects of baseline task position on apparent activation in functional imaging of memory.
Brain activation dissociates during the repeated performance of memory tasks with decreasing medial temporal and increasing orbitofrontal activation. The impact of such adaptations on a baseline task is unknown. In this study, we used H2(15)O positron emission tomography (PET) in two groups of subjects performing a continuous recognition task and a baseline task. The group performing the baseline task after the main task showed significant medial temporal activation in the subtraction (recognition task-baseline). The group performing the baseline task at the beginning showed right orbitofrontal activation. These differences appeared to result primarily from different activations during the baseline task. It thus appears that the temporal context of a baseline task may fundamentally alter cognitive requirements and substantially influence apparent brain activation during a memory task. We suggest that the automatic filtration of memories according to their relevance for ongoing reality, a capacity mediated by the orbitofrontal cortex, is one such influence on apparent activation.
PET Center, Division of Nuclear Medicine, University Hospital, CH-8091 Zürich, Switzerland.
Valerie
V
Treyer
Alfred
A
Buck
Armin
A
Schnider
D000328:Adult; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D017666:Deuterium Oxide; D004292:Dominance, Cerebral / Q000502:physiology; D005625:Frontal Lobe / Q000000981:diagnostic imaging* / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D020534:Parahippocampal Gyrus / Q000000981:diagnostic imaging / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology*; D049268:Positron-Emission Tomography; D011930:Reaction Time / Q000502:physiology; D012016:Reference Values; D013382:Subtraction Technique; D013702:Temporal Lobe / Q000000981:diagnostic imaging* / Q000502:physiology
D017666:Deuterium Oxide