Differential modulation of corticospinal excitability during haptic sensing of 2-D patterns vs. textures.
BACKGROUND
Recently, we showed a selective enhancement in corticospinal excitability when participants actively discriminated raised 2-D symbols with the index finger. This extra-facilitation likely reflected activation in the premotor and dorsal prefrontal cortices modulating motor cortical activity during attention to haptic sensing. However, this parieto-frontal network appears to be finely modulated depending upon whether haptic sensing is directed towards material or geometric properties. To examine this issue, we contrasted changes in corticospinal excitability when young adults (n = 18) were engaged in either a roughness discrimination on two gratings with different spatial periods, or a 2-D pattern discrimination of the relative offset in the alignment of a row of small circles in the upward or downward direction.


RESULTS
A significant effect of task conditions was detected on motor evoked potential amplitudes, reflecting the observation that corticospinal facilitation was, on average, ~18% greater in the pattern discrimination than in the roughness discrimination.


CONCLUSIONS
This differential modulation of corticospinal excitability during haptic sensing of 2-D patterns vs. roughness is consistent with the existence of preferred activation of a visuo-haptic cortical dorsal stream network including frontal motor areas during spatial vs. intensive processing of surface properties in the haptic system.
University of Ottawa, Ontario, Canada.
Sabah
S
Master
François
F
Tremblay
D000328:Adult; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000502:physiology*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D046709:Pattern Recognition, Physiological / Q000502:physiology*; D010812:Physical Stimulation / Q000379:methods; D011712:Pyramidal Tracts / Q000502:physiology*; D055698:Touch Perception / Q000502:physiology*; D055815:Young Adult