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Neuronal generators of visual evoked potentials in humans: visual processing in the human cortex
S Arroyo1, R P Lesser, W T Poon
1Servicio de Neurología, Hospital Clinic i Provincial de Barcelona, Spain.
Epilepsia
|May 1, 1997
Summary
Visual evoked potentials (VEP) originate from distinct areas in the occipital cortex, with sequential activation patterns observed in the lingual gyrus and surrounding regions. These findings map the temporal sequence of VEP generation.
Area of Science:
- Neuroscience
- Visual Neuroscience
- Electrophysiology
Background:
- Visual evoked potentials (VEP) are crucial for assessing visual pathway function.
- Understanding the precise cortical generators of VEPs is essential for clinical diagnosis and research.
- Previous studies have suggested VEP generation in the occipital cortex, but detailed spatiotemporal mapping remains an area of investigation.
Purpose of the Study:
- To precisely localize the cortical generators of visual (pattern) evoked potentials (VEP) in the occipital region.
- To elucidate the temporal sequence of neuronal activation underlying VEPs.
- To differentiate the contributions of mesial and lateral occipital cortex to VEP generation.
Main Methods:
- Subdural electrode arrays were implanted over the occipital cortex in four epilepsy surgery candidates.
- Checkerboard pattern reversal stimuli were used to elicit VEPs.
- Epileptogenic foci were localized, and functional mapping was performed; MRI confirmed no occipital lesions.
Main Results:
- The earliest activation (approx. 70 ms) was observed in the lingual gyrus of the mesial occipital lobe.
- Subsequent activation (approx. 80 ms) occurred superior to the calcarine fissure.
- Later activation (approx. 90 ms onwards) showed positive potentials at the occipital pole and lingual gyrus, followed by the lateral occipital lobe.
Conclusions:
- VEPs are generated by distinct, localized neuronal generators within the mesial and lateral occipital cortex.
- These generators exhibit different latencies of activation, contributing to the complex VEP waveform.
- The N1 and P1 components of scalp-recorded VEPs likely reflect the progressive activation of neuronal populations across different occipital regions.