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Topographic mapping and source localization of the pattern onset visual evoked magnetic response
C Degg1, A Slaven, R A Armstrong
1Vision Sciences, Aston University, Birmingham, UK.
Brain Topography
|January 1, 1992
Summary
Investigating the visual evoked magnetic response (VEMR) to pattern onset, this study found that contrast affects amplitude but not latency. The CIIm component may originate in similar visual cortex areas as P100m.
Area of Science:
- Neuroscience
- Visual Neuroscience
- Magnetoencephalography
Background:
- The visual evoked magnetic response (VEMR) provides insights into visual cortex activity.
- Understanding the topographical distribution of VEMR components is crucial for mapping visual processing.
Purpose of the Study:
- To investigate the topography of VEMR components to pattern onset stimuli.
- To examine the effects of check size and contrast on VEMR topography and characteristics.
- To explore the potential origins of the CIIm component using source localization.
Main Methods:
- Utilized magnetoencephalography (MEG) to record VEMR.
- Employed pattern onset stimuli with varying check sizes and contrast levels.
- Applied source localization techniques to estimate the origin of VEMR components.
Main Results:
- The pattern onset response includes early components (CIm, CIIm, CIIIm) within 200ms.
- CIIm demonstrated high amplitude and consistent latency.
- Increasing contrast enhanced VEMR amplitude, while latency remained stable.
- Check size influenced the spatial distribution of magnetic fields.
- Source localization suggested CIIm originates approximately 4cm below the scalp, near the midline.
Conclusions:
- VEMR topography is sensitive to stimulus parameters like check size and contrast.
- The CIIm component's characteristics suggest a potential shared origin with the P100m response in the visual cortex.
- CIIm and P100m may reflect different facets of visual information processing.