Attentional influences on short-interval intracortical inhibition.
OBJECTIVE
The allocation of attention to sensory stimulation and movement might influence cortical activity. Two experiments were conducted to investigate the effect of variation of intensity of attention (Experiment 1) and direction of attention (Experiment 2) on cortical excitability and short-interval intracortical inhibition (SICI) during performance of a simple index finger abduction task.


METHODS
Subjects responded to subtle cutaneous electrical stimulation delivered to the index finger while single and paired TMS pulses were delivered during muscle relaxation between successive responses. In Experiment 1, attentional resources allocated to the task were manipulated using a dual task paradigm involving a backward-counting task. In Experiment 2, spatial attention was varied by delivering cutaneous stimuli to the responding or the non-responding index finger.


RESULTS
In Experiment 1, SICI was reduced during performance, but was unaffected by variation in the intensity of attention. The results of Experiment 2, however, showed that SICI was significantly lower when attention was directed to the responding hand compared with when it was directed to the non-responding hand.


CONCLUSIONS
While SICI was not affected by variation of attentional resources, it was influenced by spatial attention.


CONCLUSIONS
These findings may be relevant in future investigations of the underlying neurophysiology of plasticity.
Thomson
Richard H S
RH
School of Psychology, University of Tasmania, Hobart, Tasmania, Australia.
Garry
Michael I
MI
Summers
Jeffery J
JJ
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D005385:Fingers / Q000294:innervation; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D009433:Neural Inhibition / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods