The Neuropsychology of Dual Task Performance: a Motor Behavior Analysis.

Neuropsychologists attempt to discern brain-behavior relationships by using a number of non-invasive methodologies. In recent years, the dual task paradigm has been used to estimate capacity limitations of the cerebral hemispheres. Researchers using the dual task method contend that behaviors controlled by overlapping brain areas will interfere with each other when executed simultaneously. Behaviors controlled by nonoverlapping brain areas will not compete with each other to the same extent. Therefore, it is reasonable to hypothesize that the magnitude of performance decrement reflects the sharing of functional systems in the brain. In this investigation, the dual task method was used to study functional neural overlap at three levels of inquiry: (1) the hemisphere level; (2) the modality level; and , (3) the motor program level. The primary task, single finger tapping, was studied at the hemispheric (i.e., left vs. right h and ) and motor program (i.e., timing, force, organization, and execution) levels. The secondary tasks differed in modality (i.e., visual-cognitive vs. manual) as well as hemispheric organization (i.e., left vs. right hemisphere). The results of the experiments indicated that most components of tapping were disturbed by simultaneous manual rather than visual-cognitive activity. This concurred with the expectation that movement systems were more functionally related than movement and visual-cognitive systems. Left hemispheric manual secondary tasks created greater decrements in right h and tapping, whereas right hemispheric manual secondary tasks produced greater decrements in left h and tapping. There were no h and and hence no hemisphere asymmetries using visual cognitive secondary tasks. The most noteworthy finding was that these asymmetrical decrement patterns were most evident in the motor program's timing of direction (flexion to extension) reversals. The results of this study lead to the conclusion that finger tapping is not a unitary activity, but the integrated action of smaller components. The components may be differentially organized in the brain and decoupled by secondary task competition. The implications of these results for future research on dual task performance and brain localization are discussed.PhDPsychobiologyUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/160097/1/8422199.pd