title: Dual-task interference: attentional and neurophysiological influences.
abstract: Performing two tasks simultaneously often degrades performance of one or both tasks. While this dual-task interference is classically interpreted in terms of shared attentional resources, where two motor tasks are performed simultaneously interactions within primary motor cortex (i.e., activity-dependent coupling) may also be a contributing factor. In the present study TMS (transcranial magnetic stimulation) was used to examine the contribution of activity-dependent coupling to dual-task interference during concurrent performance of a bimanual coordination task and a discrete probe reaction time (RT) task involving the foot. Experiments 1 and 2 revealed that activity-dependent coupling within the leg corticomotor pathway was greater during dual-task performance than single-task performance, and this was associated with interference on the probe RT task (i.e., increased RT). Experiment 3 revealed that dual-task interference occurred regardless of whether the dual-task involved two motor tasks or a motor and cognitive task, however activity-dependent coupling was present only when a dual motor task was performed. This suggests that activity-dependent coupling is less detrimental to performance than attentional processes operating upstream of the corticomotor system. Finally, while prioritising the RT task reduced, but did not eliminate, dual-task interference the contribution of activity-dependent coupling to dual-task interference was not affected by task prioritisation. This suggests that although activity-dependent coupling may contribute to dual motor-task interference, attentional processes appear to be more important. It also suggests that activity-dependent coupling may not be subject to modulation by attentional processes.
authors.affiliation: Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, Av Arlindo Bétio, 1000, Ermelino Matarazzo, São Paulo-SP, CEP 03828-000, Brazil.
authors.forename: Cynthia Y
authors.initials: CY
authors.lastname: Hiraga
authors.forename: Michael I
authors.initials: MI
authors.lastname: Garry
authors.forename: Richard G
authors.initials: RG
authors.lastname: Carson
authors.forename: Jeffery J
authors.initials: JJ
authors.lastname: Summers
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D003071:Cognition / Q000502:physiology*; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D005528:Foot; D006225:Hand; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009483:Neuropsychological Tests; D011597:Psychomotor Performance / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology; D011930:Reaction Time; D013647:Task Performance and Analysis; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult