Hearing threshold determination is an important clinical experiment for monitoring the auditory function of both normal and hear-impaired people. Conventionally, event related potential (ERP) elicited by auditory stimuli (pure tones with different frequencies and amplitudes) are utilized for the estimation of hearing threshold . In response to these stimuli, the human brain produces very small signals called ERP. The electric potentials are measured as electroencephalogram (EEG) signals. ERP is the summation of two neuro-electrical processes: evoked response and induced response. Evoked response is linked to the features of stimuli and found in the initial part of ERP recording (within 100ms of setting stimuli). Induced response is related with cognition, perception, and learning, which are found in later part of ERP recordings . Previous works investigated perturbed tones, phonemes, and sentences in the context [3, 4]. Time domain analysis of evoked response of pure tone indicates only the hearing ability . A person may get satisfactory results in a hearing experiment but cannot perceive the speech, because the hearing-tone experiment does not provide information about cognition. To the best of our knowledge, very limited research has been conducted in speech perception based on induced responses . Determination of coherent spectral properties of induced and evoked related neural responses for perturbed tones and phonemes will be important literature in audiology and electrodiagnosis of auditory neurons. In this research work, we will evaluate the coherent spectral components of these responses for normal hearing people.
- Stimuli preparation and stimuli elicited EEG signals capturing
- Generating perturbed tones with different frequencies and amplitudes
- Collecting phonemes i.e., consonant-vowel, vowel-consonant-vowel
- Collecting stimuli induced EEG signals
- Determination of coherent spectral components of neural responses
- Separating evoked and induced responses from collected EEG signals
- Determining local frequency components of evoked and induced responses
- Computing magnitude squared coherence for evoked and induced responses
- Determining coherent local frequency components as a part of the neural activities for normal hearing people
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