Coordinated neural, behavioral, and phenomenological changes in perceptual plasticity through overtraining of synesthetic associations

Rothen, Nicolas, Schwartzman, David J, Bor, Daniel and Seth, Anil K (2018) Coordinated neural, behavioral, and phenomenological changes in perceptual plasticity through overtraining of synesthetic associations. Neuropsychologia, 111. pp. 151-162. ISSN 0028-3932

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Synesthesia is associated with additional perceptual experiences, which are automatically and consistently triggered by specific inducing stimuli. Synesthesia is also accompanied by more general sensory and cortical changes, including 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. Here we investigate whether extensive training of letter-color associations leads not only to synesthetic experiences, but also to changes in cortical excitability. We confirm that overtraining synesthetic associations results in synesthetic phenomenology. Stroop tasks further reveal synesthesia-like performance following training. Electroencephalography and transcranial magnetic stimulation show, respectively, enhanced visual evoked potentials (in response to untrained patterns) and lower phosphene thresholds, demonstrating specific cortical changes. An active (using letter-symbol training) and a passive control confirmed these results were due to letter-color training and not simply to repeated testing. Summarizing, we demonstrate specific cortical changes, following training-induced acquisition of synesthetic phenomenology 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: Article
Keywords: cortical excitability; cortical plasticity; perceptual processing; electroencephalogram (EEG); transcranial magnetic stimulation (TMS)
Schools and Departments: School of Engineering and Informatics > Informatics
Research Centres and Groups: Sackler Centre for Consciousness Science
Subjects: B Philosophy. Psychology. Religion > BF Psychology > BF0309 Consciousness. Cognition Including learning, attention, comprehension, memory, imagination, genius, intelligence, thought and thinking, psycholinguistics, mental fatigue
Depositing User: Marianne Cole
Date Deposited: 23 Jan 2018 10:49
Last Modified: 29 May 2018 14:42

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