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Crossmodal visual-tactile extinction: Modulation by posture implicates biased competition in proprioceptively
Steffan Kennett1, Chris Rorden, Masud Husain
1Department of Psychology, University of Essex, Colchester, UK. skennett@essex.ac.uk
Journal of Neuropsychology
|October 14, 2009
Summary
Brain injury can cause extinction, where stimuli are missed. Posture alone can modulate this crossmodal extinction, demonstrating the brain
Area of Science:
- Neuroscience
- Cognitive Psychology
- Perception Research
Background:
- Unilateral brain injury frequently results in extinction, where contralesional stimuli are missed when presented with ipsilesional stimuli.
- Crossmodal extinction occurs when a tactile stimulus is extinguished by a visual stimulus in the ipsilateral visual field.
- Previous research suggests spatial manipulations, like altering hand position or visual event distance, can modulate crossmodal extinction.
Observation:
- A single-case study investigated crossmodal extinction using a novel spatial manipulation while keeping somatosensory input and posture constant.
- The study aimed to alter the external spatial relationship between tactile and visual events without changing retinotopic visual input.
- In a patient with right hemisphere injury, left-hand touches were extinguished by right visual field stimulation in the default posture.
Findings:
- When the patient's eyes and head turned left, shifting visual events to align with the left-hand touch in external space, extinction was eliminated.
- This occurred despite identical somatosensory and retinal stimulation, indicating the critical role of the changed spatial relationship.
- Proprioceptive postural cues were the sole signal for this altered spatial relationship, demonstrating their sufficiency in modulating extinction.
Implications:
- Postural cues alone are sufficient to modulate crossmodal extinction, challenging previous assumptions.
- This finding highlights the dynamic interplay between body posture, spatial representation, and sensory processing in the brain.
- Understanding these mechanisms could inform rehabilitation strategies for patients with sensory processing deficits following brain injury.
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