Neural, behavioural, and phenomenological changes in training-induced synaesthesia

Rothen, Nicolas; Schwartzman, David; Bor, Daniel; Seth, Anil (4 September 2017). Neural, behavioural, and phenomenological changes in training-induced synaesthesia (Unpublished). In: 20th Conference of the European Society for Cognitive Psychology (ESCoP2017). Potsdam, Germany. 03.09.-06.09.2017.

Synesthesia is associated with unusual additional perceptual experiences, which are automatically and consistently triggered by specific inducing stimuli. Synesthesia is also accompanied by more general sensory and cortical changes, such as enhanced modality-specific cortical excitability. Extensive cognitive training has been shown to generate synesthesia-like phenomenology but whether these experiences are accompanied by neurophysiological changes characteristic of synesthesia remains unknown. Addressing this question provides a unique opportunity to elucidate the neural basis of perceptual plasticity relevant to conscious experiences. In a series of experiments we investigate whether extensive training of grapheme-color associations leads not only to synesthetic experiences, but also to changes in cortical excitability. Using a structured interview, we confirm that overtraining synesthetic associations results in synesthetic phenomenology. Using electroencephalography and transcranial magnetic stimulation before and after training, we find enhanced visual evoked potentials (in response to untrained patterns) and lower phosphene thresholds, demonstrating specific cortical changes. Behavioral tasks before and after training further reveal synesthesia-like performance. Control studies confirmed these results were due specifically to grapheme-color training. A passive control without training, confirmed that these results were not due to repeated testing. An active control with an analogous training regime associating abstract symbols with graphemes led to similar behavioral changes but, crucially, not neural changes or widespread phenomenological changes characteristic of synesthesia. In summary, we demonstrate cortical changes following training that are characteristic of genuine synesthesia. Collectively, our data reveal dramatic plasticity in human visual perception, expressed through a coordinated set of behavioral, neurophysiological, and phenomenological changes.

Item Type:

Conference or Workshop Item (Speech)

Division/Institute:

07 Faculty of Human Sciences > Institute of Psychology > Psychological and Behavioral Health

UniBE Contributor:

Rothen, Nicolas

Subjects:

100 Philosophy > 150 Psychology
600 Technology > 610 Medicine & health

Language:

English

Submitter:

Nicolas Rothen

Date Deposited:

23 Apr 2018 14:28

Last Modified:

23 Apr 2018 14:28

URI:

https://boris.unibe.ch/id/eprint/113344

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