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Abstract:
Reasoning involves cognitive processes necessary for dealing
with novel situations. Two different types of processes can be
distinguished: (i) generating an internal representation of
elements in the environment and the relationships between them, and
(ii) integrating and manipulating the newly generated relations for
producing an appropriate response. Using event-related fMRI, we
tried to differentiate between the processes of relational
generation and integration, by varying the number of relations to
be processed during a visuo-spatial reasoning task, the Raven's
Progressive Matrices. Three types of problems were used:
0-relational, not requiring relational processing; 1-relational,
requiring processing of one relation only (generation); and
2-relational, requiring processing of two relations (generation and
integration). Statistical analysis was performed using SPM97.
Hemodynamic response functions (HRFs) spanning the peri-stimulus
time were fitted to the fMRI signal from the individual trials.
When 1-relational problems were compared to 0-relational,
significant increases in activation were observed bilaterally in
the dorsolateral-prefrontal cortex (Brodmann's areas 9 and 46).
Further, when 2-relational problems were compared to 1-relational,
significant increases in activation were found in the left
frontopolar-prefrontal cortex (area 10). These findings indicate
neural-level differences between the processes of generation and
integration of relations and suggest a possible functional
distinction between executive processes within the human prefrontal
cortex.
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