TY - JOUR
T1 - Topography of cortical activation differs for fundamental and harmonic frequencies of the steady-state visual-evoked responses. An EEG and PET H 215O study
AU - Pastor, M. A.
AU - Valencia, M.
AU - Artieda, J.
AU - Alegre, M.
AU - Masdeu, J. C.
N1 - Funding Information:
This study was financially supported by grants from the Department of Health, Executive Yuan, Taiwan (DOH92-TD-1024) , National Science Council of Taiwan (NSC 93-2314-B-039-031) , and China Medical University Hospital (DMR-93-021, DMR-93-078, and DMR-96-061) . The authors would like to thank Drs. Lai, Ming-Mei, Lai, Shih-Wei, and Lin, Chih-Hsueh for their kind assistance in subject recruitment.
PY - 2007/8
Y1 - 2007/8
N2 - In humans, visual flicker stimuli of graded frequency (2-90 Hz) elicit an electroencephalographic (EEG) steady-state visual-evoked response (SSVER) with the same fundamental frequency as the stimulus and, in addition, a series of harmonic responses. The fundamental component of the SSVER is generated by increased synaptic activity in primary visual cortex (V1). We set out to determine the cortical origin of the harmonic responses in humans. For this purpose, we recorded the SSVERs at 5 different frequencies (5, 10, 15, 25, and 40 Hz) and measured regional cerebral blood flow (rCBF) with positron emission tomography-H2
15O at rest and during visual stimulation at the same frequencies. The rCBF contrast weighted by the amplitude of the SSVERs first harmonics showed activation of a swath of cortex perpendicular to V1, including mostly the inferior half of the parieto-occipital sulcus. This area overlapped minimally with the primary visual cortex activated by the fundamental frequency. A different method, estimating EEG cortical source current density with low-resolution brain electromagnetic tomography, gave the same results. Our finding suggests that the inferior portion of the banks of the parieto-occipital sulci contains association visual cortex involved in the processing of stimuli that can be as simple as a flickering light source.
AB - In humans, visual flicker stimuli of graded frequency (2-90 Hz) elicit an electroencephalographic (EEG) steady-state visual-evoked response (SSVER) with the same fundamental frequency as the stimulus and, in addition, a series of harmonic responses. The fundamental component of the SSVER is generated by increased synaptic activity in primary visual cortex (V1). We set out to determine the cortical origin of the harmonic responses in humans. For this purpose, we recorded the SSVERs at 5 different frequencies (5, 10, 15, 25, and 40 Hz) and measured regional cerebral blood flow (rCBF) with positron emission tomography-H2
15O at rest and during visual stimulation at the same frequencies. The rCBF contrast weighted by the amplitude of the SSVERs first harmonics showed activation of a swath of cortex perpendicular to V1, including mostly the inferior half of the parieto-occipital sulcus. This area overlapped minimally with the primary visual cortex activated by the fundamental frequency. A different method, estimating EEG cortical source current density with low-resolution brain electromagnetic tomography, gave the same results. Our finding suggests that the inferior portion of the banks of the parieto-occipital sulci contains association visual cortex involved in the processing of stimuli that can be as simple as a flickering light source.
KW - LORETA
KW - Parieto-occipital sulcus
KW - Positron emission tomography
KW - Regional cerebral blood flow
KW - Steady-state visual-evoked potentials
KW - Visual cortex
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U2 - 10.1093/cercor/bhl098
DO - 10.1093/cercor/bhl098
M3 - Article
C2 - 17060366
AN - SCOPUS:34547652501
SN - 1047-3211
VL - 17
SP - 1899
EP - 1905
JO - Cerebral Cortex
JF - Cerebral Cortex
IS - 8
ER -