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Stimulus-specific Cortical Visual Evoked Potential Morphological Patterns
Published on: May 12, 2019
Unconscious response priming by shape depends on geniculostriate visual projection
Mika Koivisto1, Linda Henriksson, Antti Revonsuo
1Department of Psychology, University of Turku, Turku, Finland. mika.koivisto@utu.fi
The European Journal of Neuroscience
|February 7, 2012
Summary
Unconscious shape processing relies on early visual cortex (V1/V2) and lateral occipital cortex (LO). Disrupting these areas with transcranial magnetic stimulation (TMS) impacts unconscious visual priming.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Visual Perception
Background:
- Unconscious visual processing may occur independently of early visual cortex (V1/V2).
- The precise roles of different visual areas in unconscious processing remain unclear.
Purpose of the Study:
- To investigate the causal role of V1/V2 and lateral occipital cortex (LO) in unconscious visual processing.
- To determine the temporal dynamics of visual processing for unconscious shape priming.
Main Methods:
- Transcranial magnetic stimulation (TMS) was applied to V1/V2 and LO.
- A metacontrast-masked response priming task with arrow stimuli was used.
- A control task assessed conscious visibility of masked primes.
Main Results:
- TMS of V1/V2 impaired unconscious priming 30-90 ms after prime onset.
- TMS of LO reduced priming magnitude 90-120 ms post-stimulus, particularly early in the experiment.
- TMS did not affect conscious visibility or mask effectiveness.
Conclusions:
- A feedforward sweep from V1/V2 to LO is essential for unconscious shape priming.
- Conscious shape perception additionally requires recurrent processing.
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