Restriction of task processing time affects cortical activity during processing of a cognitive task: an event-related slow cortical potential study

As is known from psychometrics. restriction of task processing time by the instruction to respond as quickly and accurately as possible leads to task- unspecific cognitive processing, Since this task processing mode is used in most functional neuroimaging studies of human cognition, this may evoke co rtical activity that is functionally not essential for the particular task under investigation. Using topographic recordings of event-related slow cor tical potentials, two experiments have been performed to investigate whethe r cortical activity during processing of a visuo-spatial imagery task is su bstantially influenced by the time provided to process the task. Furthermor e, it was investigated whether this effect is additionally modulated by a s ubject's task-specific ability. The instruction to respond as quickly and a ccurately as possible led to increased negative slow cortical potential amp litudes over parietal and frontal regions and significantly interacted with task-specific ability. While cortical activity recorded over parietal and frontal regions was different between subjects with low and high spatial ab ility when processing time was unrestricted, no such differences were found between ability groups when subjects were instructed to answer both quickl y and accurately. These results suggest that restricting processing time ha s considerable effects on the amount and the pattern of brain activity duri ng cognitive processing and should be taken into account more explicitly in the experimental design and interpretation of neuroimaging studies of cogn ition, (C) 2001 Elsevier Science B.V. All rights reserved.