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Abstract:
Imagine that a person is looking at a photograph saying,
"Brothers and sisters have I none. That man's father is my father's
son." This riddle turns out to be relatively difficult and provides
an interesting forum for analyzing the interaction of verbal
working memory, problem solving and language comprehension. In the
current study we examined similar problems using event-related fMRI
to distinguish differences in the timing of the response of
cortical regions that compose the working memory network. Problems
were developed such that the processing demand as well as the
timing of the manipulation of the contents of working memory (i.e.,
a calculation) was varied. Activation was observed in several
regions including the dorsolateral prefrontal cortex, the inferior
frontal gyrus, and the parietal lobe. The hypotheses that link the
psychological computation to the cortical anatomy place the
top-down planning of the task in the DLPFC, the sequential planning
of calculations in the frontal opercular region, spatial
calculation processes in the intraparietal sulcus, and the
maintenance of information in the frontal triangular/inferior
parietal network. The execution of the processes appears to be
highly collaborative, as indicated by the correlation of the time
courses of certain pairs of areas. The main new result is the
measurement of the differential dynamic time course as it adapts to
the computational load imposed by the different problem
types.
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