Background. The aim of this study was to investigate mnemonic
strategic deficits in schizophrenic patients.
Methods. Analogous tasks were used that required the self-generation
of an efficient strategy and
its implementation in two domains: visuospatial and verbal. The tasks were
given to 20 IQ
preserved schizophrenics and 20 matched normal controls. A number of
different scores was derived
from each task including strategy, short-term memory capacity and perseveration.
Results. Overall, the schizophrenic patients were significantly
impaired in their ability to generate
effective mnemonic strategies on both tasks. In addition, on the visuospatial
task there was no
difference between the groups on the memory scores, but the schizophrenic
patients made
significantly more perseverative errors than controls. They were disproportionately
worse on the
verbal strategy task, showing impairment on memory as well as on strategy
scores and were also
impaired at semantically classifying the words. Performance was similar
to the deficit seen in
patients with frontal lobe excisions and Parkinson's disease,
in terms of the inability to generate an
effective strategy. The deficit on the verbal task was similar
to patients with temporal lobe excisions
who show impaired verbal memory. However, the pattern differed in the sense
that the temporal
lobe patients were able to generate effective strategies, unlike the patients
with schizophrenia.
Conclusions. High functioning schizophrenic patients are impaired
in utilizing visuospatial and
verbal mnemonic strategies. By comparing the results with those of
neurosurgical excision patients,
further evidence is provided for both frontal and temporal lobe involvement
in schizophrenia.