Effects of stimulus presentation rate on the activity of primary somatosensory cortex: a functional magnetic resonance imaging study in humans.
To investigate the effect of stimulus presentation rate on the activity of primary somatosensory cortex, we performed echo-planar functional magnetic resonance imaging using a 1.5-tesla magnetic resonance system. Eight right-handed normal volunteers underwent functional magnetic resonance imaging during somatosensory stimulation with a 0.2 ms electrical square wave to the left index finger at 1, 4, 8, 16, and 32 Hz at constant intensity. Activated areas were located mainly around 'the hand area' of the right postcentral gyrus. Between 4 and 16 Hz, almost all subjects showed significant activation, but at 1 Hz and 32 Hz, five of eight subjects showed no activation. The average number of activated pixels in this area between 4 and 16 Hz were significantly greater than those at 1 Hz and 32 Hz, and the average percent signal increase had its activation peak at 8 Hz. Our results suggest that the existence of the optimal stimulation rate range may be a common phenomenon to a variety of sensory modalities. The electrical somatosensory stimulation rates from 4 Hz to 16 Hz are advisable to investigate the activation of the primary somatosensory cortex in human subjects.
Departments of 1Department of Neurology, Osaka University Graduate School of Medicine, Suita City, Osaka, Japan.
M
M
Takanashi
K
K
Abe
T
T
Yanagihara
Y
Y
Oshiro
Y
Y
Watanabe
H
H
Tanaka
N
N
Hirabuki
H
H
Nakamura
N
N
Fujita
D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D017352:Echo-Planar Imaging / Q000379:methods; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006225:Hand / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D013003:Somatosensory Cortex / Q000502:physiology*