Timing of right parietal and frontal cortex activity in visuo-spatial perception: a TMS study in normal individuals.
In a recent study we showed that repetitive transcranial magnetic stimulation (rTMS) with train duration of 400 ms over right frontal and right posterior parietal cortices gives rise to transitory contralateral visuo-spatial neglect in normal subjects. In the present experiment we investigated whether using single-pulse TMS it is possible to obtain information about the timing of cortical activity related to spatial cognition. Nine healthy subjects performed in baseline condition and during TMS a tachistoscopic task, requiring a forced-choice estimation of the length of the two segments of prebisected horizontal lines. Single-pulse TMS was triggered at various time intervals (150 ms, 225 ms, 300 ms) after visual stimulus onset with a focal coil over P6 and F4 (according to 10/20 EEG system). Relative transitory rightward bias was observed only when parietal TMS was delivered 150 ms after visual stimulus presentation. Frontal stimulation induced no effect on visuo-spatial perception with the time intervals explored.
Fierro
B
B
Neurophysiological Unit, Institute of Neuropsychiatry, Via G. La Loggia 1, University of Palermo, Italy.
Brighina
F
F
Piazza
A
A
Oliveri
M
M
Bisiach
E
E
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D004558:Electric Stimulation; D005625:Frontal Lobe / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D008875:Middle Aged; D010296:Parietal Lobe / Q000502:physiology*; D010468:Perceptual Disorders / Q000503:physiopathology; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D013028:Space Perception / Q000502:physiology*