INTERFERENCE BETWEEN 2 CONCURRENT TASKS IS ASSOCIATED WITH ACTIVATIONOF OVERLAPPING FIELDS IN THE CORTEX

Interference between two concurrent tasks can be measured as an increa sed reaction time during simultaneous performance compared to when eac h task is performed alone. We tested the hypothesis that two tasks int erfere because they require activation of overlapping areas of the cer ebral cortex. With positron emission tomography we measured cortical a ctivation as fields with significant increase in regional cerebral blo od flow during single task performance of an auditory and a visual go/ no-go task and an auditory and a visual short-term memory (STM) task. In a separate experiment we measured the degree of interference betwee n the two go/no-go tasks and between the two STM tasks during dual tas k performance. Both the two go/no-go tasks and the two STM tasks activ ated overlapping parts of the cortex and interfered significantly duri ng dual task performance. The two STM tasks had a lar er volume of ove rlap and also significantly larger increase in reaction time during du al task performance, compared to the go/no-go tasks. The results thus indicate that two concurrent tasks interfere, with a resulting increas e in reaction One, if they require activation of overlapping parts of the cortex. (C) 1997 Elsevier Science B.V.