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Stimulation of the dorsal speech stream improves speech perception performance in adults of all ages
Poster C5 in Poster Session C, Friday, October 7, 10:15 am - 12:00 pm EDT, Millennium Hall
Valérie Brisson1,2, Pascale Tremblay1,2; 1Rehabilitation department, Université Laval, Québec, Canada, 2Cervo Research Center, Québec, Canada
Normal aging has been associated with increasing difficulties to perceive speech in noise (SPiN). Several studies have shown that this age-related decline can occur in the absence of hearing loss, and that it is associated with changes in the structure and the activity of speech processing areas of the brain [1]. In a previous study, we showed that SPiN could be improved by applying excitatory transcranial magnetic stimulation (TMS) over the left ventral premotor cortex (PMv) [2]. Our results also showed that individuals with lower baseline performance showed the most improvement. These results await replication, however. The objectives of the present study were therefore 1) to confirm whether TMS applied to regions of the dorsal speech stream can improve SPiN performance in young to older adults, and 2) to evaluate the contribution of age, baseline performance, brain structure and brain activity to TMS-induced performance gains in order to understand the mechanisms of action. METHOD. 30 right-handed healthy adults aged 20 to 80 years will be recruited. An auditory syllable discrimination test was used to evaluate SPiN (0 dB SPL). The syllables were pronounced by a fixed talker (low variability condition) or by eight different talkers (high variability condition). MR images were acquired to measure brain structure and activity. Three regions of the left dorsal stream (PMv, superior temporal gyrus – STG, superior temporal sulcus – STS) [3] were used as targets based on each participant BOLD signal pattern while performing the SPiN test in the MRI scanner. A sham stimulation was also included. In the lab, the SPiN test was administered after each stimulation (real or sham). Linear mixed models were computed on a preliminary sample of 16 participants aged 21 to 73 years old (M = 52.01) to examine the effects of age, baseline performance, and talker variability on accuracy and reaction time gains (post TMS – baseline). RESULTS. The results indicate that participants with lower baseline performance showed the most improvement on accuracy (main effect, F(1, 66) = 111.08, p = <.001). Participants with longer baseline reaction times (RT) showed stronger reductions after TMS to the STG or the PMv (Target x Baseline, F(2, 75) = 3.90, p = .025). An age effect was found after TMS to PMv, in the multiple talker condition: younger adults showed more improvement in accuracy than older adults (Age x Target x Talker variability: F(2, 66) = 5.20, p = 0.008). CONCLUSION. The results replicate our recent study suggesting that those with lower performance benefit more from TMS. This supports the relevance of further investigating TMS as a potential rehabilitation tool to reduce SPiN difficulties in aging. The final results, which will include the structure and activity within the targeted regions, will clarify the mechanisms of action. [1] Tremblay, Brisson & Deschamps (2021). Neuroimage. [2] Brisson & Tremblay (2021). B&L. [3] Hickock & Poeppel (2007). Nat Rev Neurosci.
Topic Areas: Speech Perception, Perception: Auditory