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Abstract:
There are at least two strategies for remembering route
directions (Aginsky et al, 1997; Schölkopf & Mallot,
1995): recall which way to turn at specific landmarks; or recall a
sequence of turns. Twelve normal subjects were studied with
whole-brain fMRI at 1.5 Tesla (22 interleaved slices, 6 mm/slice)
while performing both strategies. Subjects later reported which
strategy was easier. Functional images were motion-corrected,
realigned, normalized to Talairach space, and smoothed in SPM99
(Wellcome Dept. of Cognitive Neurology, UK), then converted to t
maps. Preliminary results from the first six subjects indicated
that the pattern of brain activation depends on instruction
preference. Subjects who preferred landmark information showed
greater activation for landmark relative to sequence recall in
areas including bilateral fusiform gyri and right parahippocampal
gyrus, which have been implicated in real-world navigation (Barrash
et al, 2000). The same contrast for subjects who preferred sequence
information yielded uneven bilateral fusiform activation (left more
than right), several frontal and parietal areas, and no significant
right parahippocampal activation. A recently performed behavioral
study (Manly, Arnold, & Grafman, in prep) indicates that for
long-term recall, the landmark strategy is more effective.
Conjunction analyses for both groups' nonpreferred strategy yielded
common frontal and parietal activations, which may be associated
with performance monitoring during a perceived difficult
task.
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