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Detecting Pre-Stimulus Source-Level Effects on Object Perception with Magnetoencephalography
Published on: July 26, 2019
The role of prestimulus activity in visual extinction
Maren Urner1, Margarita Sarri, Jessica Grahn
1UCL Institute of Cognitive Neuroscience, London WC1N 3AR, UK. maren.urner.09@ucl.ac.uk
Neuropsychologia
|May 18, 2013
Summary
Prestimulus activity in visual brain regions influences awareness in visual extinction, a condition following right-hemisphere damage. Enhanced connectivity may explain these neural activity differences, impacting perception of visual stimuli.
Area of Science:
- Neuroscience
- Cognitive Neurology
Background:
- Visual extinction occurs after right-hemisphere damage, causing inconsistent perception of left visual field stimuli, especially during bilateral presentation.
- While awareness is linked to parietal and frontal activity, the reasons for stimulus omission remain unclear.
- Prestimulus neural activity is known to bias perceptual decisions in healthy individuals.
Purpose of the Study:
- To investigate the role of prestimulus neural activity in visual extinction.
- To determine if fluctuations in brain activity before stimulus onset affect awareness in patients with visual extinction.
Main Methods:
- Functional magnetic resonance imaging (fMRI) was used to measure prestimulus activity in a patient with right parietal damage and visual extinction.
- An extinction paradigm compared prestimulus activity during identical bilateral trials that resulted in either perception or omission of the left visual field stimulus.
- Dynamic causal modeling (DCM) analyzed effective connectivity within and between visual areas.
Main Results:
- Significantly increased prestimulus activity was observed in the left calcarine sulcus and right occipital inferior cortex.
- These areas showed increased activity both before and during visual stimulation.
- DCM revealed that enhanced effective connectivity, both intrinsic and extrinsic, explained these prestimulus activity differences.
Conclusions:
- Prestimulus neural activity in visually responsive areas significantly impacts awareness in visual extinction.
- Fluctuations in connectivity within and between visual areas mediate these effects.
- This provides evidence for the role of ongoing neural dynamics in perceptual awareness following brain injury.
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