A rapid evoked potential index of cortical adaptation
| Autor: | Ronald E. Carr, William Seiple, J I Nelson, Mark J. Kupersmith |
|---|---|
| Rok vydání: | 1984 |
| Předmět: |
Adult
Male medicine.medical_specialty genetic structures Visual N1 Visual Acuity Electroencephalography Stimulus (physiology) Audiology medicine Humans Evoked potential Visual Cortex Cerebral Cortex Communication medicine.diagnostic_test business.industry General Neuroscience Contrast (statistics) Adaptation Physiological Electrophysiology Visual cortex medicine.anatomical_structure Evoked Potentials Visual Female Neurology (clinical) Spatial frequency Psychology business |
| Zdroj: | Electroencephalography and Clinical Neurophysiology/Evoked Potentials Section. 59:454-464 |
| ISSN: | 0168-5597 |
| DOI: | 10.1016/0168-5597(84)90004-2 |
| Popis: | Contrast thresholds and acuity limits were measured in 4 observers with the swept visual evoked potential (VEP) technique. In this technique, grating contrast or grating spatial frequency is electronically varied while the subject's evoked response is retrieved in real time (without averaging). Contrast or spatial frequency variation make the stimulus vary in intensity; zero VEP response amplitude indicates the threshold intensity. Large shifts occur in the indicated threshold when stimulus sweep direction is reversed. Thresholds are always relatively elevated when the run begins with the strongest stimulus value. These shifts do not have a technical origin in the delay of the instrument (Nelson et al. 1984b). Here, it is shown that the shifts are due to orientation and spatial frequency selective adaptation, probably of cortical origin. Measureable adaptation is produced by momentary exposure to contrasts as low as 1.25%; nearly maximum adaptation (0.6 log units) is reached with 20% contrast. These findings support the concept of a contrast gain control mechanism in visual cortex, and pose practical problems for visual assessment with the evoked potential. |
| Databáze: | OpenAIRE |
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