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When conditioned responses "fire back": bidirectional cross-activation creates learning opportunities in synesthesia
1University of Bern, Institute of Psychology, Bern 9, Switzerland. beat.meier@psy.unibe.ch
Neuroscience
|June 16, 2007
Summary
Grapheme-color synesthesia typically involves unidirectional color experiences. This study reveals implicit bidirectional cross-activation in synesthesia using a novel conditioning method, suggesting parietal lobe involvement.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Sensory Perception
Background:
- Grapheme-color synesthesia usually presents unidirectional subjective experiences (e.g., letters evoking colors).
- Prior research hinted at implicit bidirectional cross-activation in digit-color synesthesia.
- Investigating bidirectionality in other synesthesia types requires new methodologies.
Purpose of the Study:
- To investigate implicit bidirectional cross-activation in grapheme-color synesthesia.
- To introduce a novel method for assessing synesthetic bidirectionality.
- To explore the neural mechanisms underlying this phenomenon.
Main Methods:
- A conditioning paradigm was employed, associating a startle response with a specific color.
- Grapheme-color synesthetes and a control group were tested.
- The generalization of conditioned startle responses to color-inducing graphemes was measured.
Main Results:
- Synesthetes, unlike controls, exhibited a conditioned startle response to a grapheme after conditioning to its corresponding color.
- This indicates an implicit association between the grapheme and the shock, generalizing from the real color.
- The findings support bidirectional cross-activation at an implicit level.
Conclusions:
- Bidirectional cross-activation is not limited to digit-color synesthesia but occurs in grapheme-color synesthesia.
- Implicit cross-activation may occur via associations established through conditioning.
- Parietal brain regions are implicated in this neural 'backfiring' mechanism.
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