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The Journal of Neuroscience, December 17, 2003, 23(37):11621-11627

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Behavioral/Systems/Cognitive
Human Cerebral Activation during Steady-State Visual-Evoked Responses

Maria A. Pastor,¹ Julio Artieda,¹ Javier Arbizu,² Miguel Valencia,¹ and Jose C. Masdeu¹

Departments of ¹Neurology and ²Nuclear Medicine, University of Navarra School of Medicine, and the Clínica Universitaria de Navarra, Pamplona 31080, Spain

Flicker stimuli of variable frequency (2-90 Hz) elicit a steady-state visual-evoked response (SSVER) in the electroencephalogram (EEG) with the same frequency as the stimulus. In humans, the amplitude of this response peaks at 15 Hz, decreasing at higher stimulation frequencies. It was not known whether this peak response corresponds to increased synaptic activity in the visual cortex or to other mechanisms [for instance, the temporal coherence (phase summation) of evoked responses]. We studied the SSVER in 16 normal volunteers by means of visual stimulation at 14 different frequencies (from 5 to 60 Hz) while recording the EEG. In nine subjects of the group, we measured regional cerebral blood flow (rCBF) with positron emission tomography (PET)-H₂¹⁵O at rest and during visual stimulation at five different frequencies: 5, 10, 15, 25, and 40 Hz. We confirmed that the amplitude of the SSVER in occipital regions peaks at 15 Hz stimulation. Applying to the PET rCBF data a contrast weighted by the amplitude of the SSVER, we determined that the primary visual cortex rCBF follows an activation pattern similar to the SSVER. This finding suggests that the amplitude of the SSVER corresponds to increased synaptic activity, specifically in Brodmann's area 17. Additionally, this study showed that visual stimulation at 40 Hz causes selective activation of the macular region of the visual cortex, and that a region in the dorsal aspect of the Crus I lobule of the left cerebellar hemisphere is activated during repetitive visual stimulation.

Key words: steady-state visual-evoked potentials; gamma oscillatory activity; regional cerebral blood flow; positron emission tomography; cerebellum; visual cortex

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Received May 31, 2003; revised October 15, 2003; accepted October 15, 2003.

This article has been cited by other articles:

				M. A. Pastor, C. Vidaurre, M. A. Fernandez-Seara, A. Villanueva, and K. J. Friston Frequency-Specific Coupling in the Cortico-Cerebellar Auditory System J Neurophysiol, October 1, 2008; 100(4): 1699 - 1705. [Abstract] [Full Text] [PDF]

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