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Isik M, Eskikurt G, Erdogan ET. Neuromodulation of the left auditory cortex with transcranial direct current stimulation (tDCS) has no effect on the categorical perception of speech sounds. Neuropsychologia 2023; 178:108442. [PMID: 36481255 DOI: 10.1016/j.neuropsychologia.2022.108442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 11/23/2022] [Accepted: 12/03/2022] [Indexed: 12/11/2022]
Abstract
Temporal cue analysis in auditory stimulus is essential in the perception of speech sounds. The effect of transcranial direct current stimulation (tDCS) on auditory temporal processing remains unclear. In this study, we examined whether tDCS applied over the left auditory cortex (AC) has a polarity-specific behavioral effect on the categorical perception of speech sounds whose temporal features are modulated. Sixteen healthy volunteers in each group were received anodal, cathodal, or sham tDCS. A phonetic categorization task including auditory stimuli with varying voice onset time was performed before and during tDCS, and responses were analyzed. No statistically significant difference was observed between groups (anode, cathode, sham) and within the groups (pre-tDCS, during tDCS) in comparisons of the slope parameter of the identification function obtained from the phonetic categorization task data. Our results show that a single-session application of tDCS over the left AC does not significantly affect the categorical perception of speech sounds.
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Affiliation(s)
- Mevlude Isik
- Neurological Sciences Research and Application Center (İSÜCAN), Istinye University, Istanbul, Turkey.
| | - Gokcer Eskikurt
- Department of Physiology, Istinye University, Faculty of Medicine, Istanbul, Turkey.
| | - Ezgi Tuna Erdogan
- Department of Physiology, Koç University, Faculty of Medicine, Istanbul, Turkey.
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Bidelman GM, Chow R, Noly-Gandon A, Ryan JD, Bell KL, Rizzi R, Alain C. Transcranial Direct Current Stimulation Combined With Listening to Preferred Music Alters Cortical Speech Processing in Older Adults. Front Neurosci 2022; 16:884130. [PMID: 35873829 PMCID: PMC9298650 DOI: 10.3389/fnins.2022.884130] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 06/17/2022] [Indexed: 11/13/2022] Open
Abstract
Emerging evidence suggests transcranial direct current stimulation (tDCS) can improve cognitive performance in older adults. Similarly, music listening may improve arousal and stimulate subsequent performance on memory-related tasks. We examined the synergistic effects of tDCS paired with music listening on auditory neurobehavioral measures to investigate causal evidence of short-term plasticity in speech processing among older adults. In a randomized sham-controlled crossover study, we measured how combined anodal tDCS over dorsolateral prefrontal cortex (DLPFC) paired with listening to autobiographically salient music alters neural speech processing in older adults compared to either music listening (sham stimulation) or tDCS alone. EEG assays included both frequency-following responses (FFRs) and auditory event-related potentials (ERPs) to trace neuromodulation-related changes at brainstem and cortical levels. Relative to music without tDCS (sham), we found tDCS alone (without music) modulates the early cortical neural encoding of speech in the time frame of ∼100-150 ms. Whereas tDCS by itself appeared to largely produce suppressive effects (i.e., reducing ERP amplitude), concurrent music with tDCS restored responses to those of the music+sham levels. However, the interpretation of this effect is somewhat ambiguous as this neural modulation could be attributable to a true effect of tDCS or presence/absence music. Still, the combined benefit of tDCS+music (above tDCS alone) was correlated with listeners' education level suggesting the benefit of neurostimulation paired with music might depend on listener demographics. tDCS changes in speech-FFRs were not observed with DLPFC stimulation. Improvements in working memory pre to post session were also associated with better speech-in-noise listening skills. Our findings provide new causal evidence that combined tDCS+music relative to tDCS-alone (i) modulates the early (100-150 ms) cortical encoding of speech and (ii) improves working memory, a cognitive skill which may indirectly bolster noise-degraded speech perception in older listeners.
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Affiliation(s)
- Gavin M. Bidelman
- Department of Speech, Language and Hearing Sciences, Indiana University Bloomington, Bloomington, IN, United States,School of Communication Sciences and Disorders, The University of Memphis, Memphis, TN, United States,*Correspondence: Gavin M. Bidelman,
| | - Ricky Chow
- Rotman Research Institute, Baycrest Centre, Toronto, ON, Canada
| | | | - Jennifer D. Ryan
- Rotman Research Institute, Baycrest Centre, Toronto, ON, Canada,Department of Psychology, University of Toronto, Toronto, ON, Canada,Department of Psychiatry, University of Toronto, Toronto, ON, Canada,Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Karen L. Bell
- Department of Audiology, San José State University, San Jose, CA, United States
| | - Rose Rizzi
- Department of Speech, Language and Hearing Sciences, Indiana University Bloomington, Bloomington, IN, United States,School of Communication Sciences and Disorders, The University of Memphis, Memphis, TN, United States
| | - Claude Alain
- Rotman Research Institute, Baycrest Centre, Toronto, ON, Canada,Department of Psychology, University of Toronto, Toronto, ON, Canada,Institute of Medical Science, University of Toronto, Toronto, ON, Canada,Music and Health Science Research Collaboratory, University of Toronto, Toronto, ON, Canada
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