Hippocampal activation during face-name associative memory encoding: blocked versus permuted design.
BACKGROUND
The contribution of the hippocampal subregions to episodic memory through the formation of new associations between previously unrelated items such as faces and names is established but remains under discussion. Block design studies in this area of research generally tend to show posterior hippocampal activation during encoding of novel associational material while event-related studies emphasize anterior hippocampal involvement. We used functional magnetic resonance imaging to assess the involvement of anterior and posterior hippocampus in the encoding of novel associational material compared to the viewing of previously seen associational material.


METHODS
We used two different experimental designs, a block design and a permuted block design, and applied it to the same associative memory task to perform valid statistical comparisons.


RESULTS
Our results indicate that the permuted design was able to capture more anterior hippocampal activation compared to the block design, which emphasized more posterior hippocampal involvement. These differences were further investigated and attributed to a combination of the polymodal stimuli we used and the experimental design.


CONCLUSIONS
Activation patterns during encoding in both designs occurred along the entire longitudinal axis of the hippocampus, but with different centers of gravity. The maximal activated voxel in the block design was situated in the posterior half of the hippocampus while in the permuted design this was located in the anterior half.
Laboratory for Neuropsychology, Department of Neurology, Ghent University, De Pintelaan 185, 4K3, Ghent, Belgium. frederick.devogelaere@ugent.be
Frederick
F
De Vogelaere
Patrick
P
Santens
Erik
E
Achten
Paul
P
Boon
Guy
G
Vingerhoets
D000328:Adult; D001245:Association Learning / Q000502:physiology*; D001921:Brain / Q000502:physiology; D001931:Brain Mapping / Q000379:methods; D005145:Face; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008568:Memory / Q000502:physiology*; D009275:Names; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D014796:Visual Perception / Q000502:physiology; D055815:Young Adult