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Abstract:
Post-mortem and in vivo imaging studies suggest that the
hippocampal system is implicated in schizophrenia. Here, we examine
the performance of schizophrenia patients on a task that
selectively taps hippocampal dysfunction in animals with selective
hippocampal lesions -- the ordered transitivity task (Dusek &
Eichenbaum, 1997). In this task, participants are initially trained
on a series of two-item discriminations (i.e., AB=A, BC=B, CD=C,
DE=D). Participants may discriminate these adjacent pairs simply by
memorizing each individual pair or by understanding that the entire
set of stimuli is an ordered sequence (i.e.,
A>B>C>D>E). After training, participants are tested on
each adjacent pair, an "easy inference", non-transitivity pair
(AE), and a "hard inference", transitivity pair (BD), the latter of
which can only be evaluated via an understanding of the
hierarchical nature of the stimuli. The results suggest that
schizophrenia patients had more difficulty than nonpsychiatric
controls in responding to the hard inference, transitivity probes
(BD) but not to the easy inference, nontransitivity probes (AE).
These results are consistent with the notion that hippocampal
memory function is disrupted in schizophrenia.
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