Subregions of human MT complex revealed by comparative MEG and direct electrocorticographic recordings.
OBJECTIVE
To locate the visual motion complex (MT+) and study its response properties in an epilepsy surgery patient.


METHODS
A 17-year-old epilepsy patient underwent invasive monitoring with subdural electrodes in the right temporo-parieto-occipital area. MT+ was investigated by cortical electric stimulation and by epicortical visual evoked potentials time-locked to motion onset of sinusoidal gratings (motion VEP). Motion-related visual evoked magnetic field (motion VEF) was also recorded before the electrode implantation to complement the invasive recording.


RESULTS
Motion VEPs revealed two subregions within MT+, generating early and late potentials respectively. The early activity with a peak around 130 ms was localized at a single electrode situated immediately caudal to the initial portion of the ascending limb of the superior temporal sulcus (AL-STS). The late activity, peaking at 242-274 ms, was located ventro-rostrally over three electrodes. Among the four electrodes with motion VEPs, cortical stimulation at the most caudal pair elicited motion-in-depth perception involving the whole visual field. In addition to two subregions revealed on the gyral crown, magnetoencephalography (MEG) demonstrated another subregion with a late motion VEF in AL-STS immediately rostral to the electrode with the early motion VEP.


CONCLUSIONS
In combination with MEG recording, the present invasive exploration demonstrated human MT+ in a focal area of the temporo-parieto-occipital junction and delineated possible three subregions as indicated by the different latencies and distributions of the motion VEP/VEFs.


CONCLUSIONS
Comparative MEG and direct electrocorticographic recordings delineated possible subregions within the human MT complex.
Human Brain Research Center, Kyoto University Graduate School of Medicine, Shogoin, Sakyo, Kyoto 606-8507, Japan.
R
R
Matsumoto
A
A
Ikeda
T
T
Nagamine
M
M
Matsuhashi
S
S
Ohara
J
J
Yamamoto
K
K
Toma
N
N
Mikuni
J
J
Takahashi
S
S
Miyamoto
H
H
Fukuyama
H
H
Shibasaki
D000293:Adolescent; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004569:Electroencephalography; D017029:Epilepsy, Complex Partial / Q000503:physiopathology; D005074:Evoked Potentials, Visual / Q000502:physiology*; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D010296:Parietal Lobe / Q000502:physiology; D013355:Subdural Space; D013702:Temporal Lobe / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology*