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Abstract:
Abstract: One of the most basic abilities of organisms is to
learn new information. The present experiment was designed to study
the neural correlates, expressed through changes in cerebral blood
flow, of multitrial learning of verbal information. Sixteen young
subjects participated in a verbal discrimination task, similar to
the object discrimination task used with nonhuman animals. On each
of five successive study/test trials, subjects noted which of two
words in successively presented pairs was underlined, and then
attempted to identify the target word thus noted in each test pair.
Regional cerebral blood flow (rCBF) was measured on the first,
second, and fifth learning trials with positron emission tomography
(PET). Over trials, discrimination performance increased linearly.
For each subject a linear 'rate of change' score of behavioral
performance was calculated, and related to both a linear and
non-linear rCBF 'rate of change' score at each voxel in the brain.
During both encoding and retrieval, linear changes in behavioral
discrimination correlated positively with linear rCBF changes in
the left medial temporal lobe (MTL) regions, and with nonlinear
rCBF changes in the right MTL regions. These findings suggest that
linear changes in behavior may arise from both linear and
non-linear changes in the underlying neural systems.
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