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INTRODUCTION Frequency following response (FFR) using speech stimuli is used extensively to assess brainstem processing in individuals with auditory processing disorder, dyslexia, language impairment, musicians etc and determining the effects of training on brainstem encoding (Banai & Kraus, 2008; Skoe & Kraus, 2010). It is reported in literature that FFR for speech is enhanced in musicians compared to non-musicians (Banai & Kraus, 2008). They attributed the difference to neural plasticity at the level of brainstem in musicians. Dance is a form of art which requires constant auditory attention to pitch, rhythm and tempo of the music (Poikonen, Toivainen & Tervaniemi, 2016; d a Silva, Dias & Periera, 2015). Bharatanatyam is a traditional Indian classical dance form practiced in South India. The word Bharatanatyam connotes a dance form which harmoniously would express the bhava, raga and tala. The dance form requires auditory attention, co-ordination of rhythm and tempo of the music to perform an act appropriately. Silva, Dias & Periera (2015) reported that temporal resolution and auditory figure ground perception is enhanced in dancers compared to non-dancers. FFR for speech is reported to assess objectively if there are any neuro plasticity for speech stimuli at the level of brainstem. It may be assumed that the temporal coding in individuals may be enhanced in dancers because of constant practice. However, there is paucity of literature regarding the assessment of temporal encoding of speech (FFR) in dancers and non-dancers. Thus, it is essential to study differences in FFR for speech stimuli in Bharatanatyam dancers compared to non-dancers. METHOD 40 individuals with normal hearing between the age of 18-25 years participated in the study. The participants were divided into two groups based on who practice Bharatanatyam dance (20 participants) and those who don’t practice dance (20 participants). Individuals in dancers group were practicing dance for at least 5 years to 10 years. All the participants in the study didn’t have any history otologic symptoms, metabolic and systemic disease causing hearing loss and use of ototoxic drugs. FFR for speech stimuli was recorded using insert earphones in Biologic EP system separately for left and right ear. Speech stimulus /da/ with duration of 40 ms duration was used in the study. The stimuli were presented at 80 dB nHL using standard response and stimulus parameters (Skoe & Kraus, 2010). The non-inverting electrode was placed on vertex, inverting electrode was placed on mastoid of test ear and ground electrode was placed on mastoid of non-test ear using vertical electrode montage. FFR for speech stimuli was analyzed in terms of amplitude and latency differences between Bharatanatyam dancers and non-dancers. RESULTS AND DISCUSSION The results of the study showed that there was an enhanced frequency following response recorded using speech stimuli in dancers compared to non-dancers. Shapiro Wilks test of normality suggested that the data was normally distributed (p>0.05). The results of MANOVA showed that the latencies were significant lower (p<0.01) for all FFR peaks for dancers compared to non-dancers. MANOVA results also showed that the amplitude of all the FFR waves was significantly higher (p<0.01) for Bharatanatyam dancers compared to non-dancers. The effect size of the significant difference (partial eta squared value) was >0.7. This suggested that the difference was strongly significant. The results of the study showed that there was an enhancement in FFR for speech in Bharatanatyam dancers compared to non-dancers. Silva, Dias & Periera (2015) also reported that auditory temporal resolution is enhanced in dancers compared to non-dancers. The dancer is involved in co-ordination of physical, spatial and temporal abilities in the brain. Temporal coding for at the level of brainstem would also play a major role in the perception of tempo and rhythm which is a core component of Bharanatyam dance. The study provides an evidence of enhanced temporal coding at the level of brainstem in Bharatanatyam dancers. Thus, the study indicates an increased plasticity of the brainstem with regular dance practice. Hence, the study suggests the use of dance as a tool to improve brainstem encoding. However, further studies using a larger group of individuals with other dance forms included are necessary for better generalization of the results. CONCLUSIONS The results of the study showed that there was an enhancement in FFR for speech in Bharatanatyam dancers compared to non-dancers. The result of the study suggests that dance practice enhances the sensory perception and improves temporal encoding at the level of brainstem. However, further studies on a larger group of population are essential for better applicability of the results.
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