Prevalence of mismatch negativity with tonal stimuli in normal-hearing individuals

Abstract Electrophysiological measures are one of the objective modes of assessment to check the integrity of the auditory function. The endogenous potentials like mismatch negativity (MMN) are responses which are due to internal events such as cognition or perception. In clinical practice and researches it was observed that MMN not present in all normal hearing individual. So, there is a need to study prevalence of MMN in normal population, which helps the researchers and clinicians in interpreting clinical findings. 50 participants recruited in the age range of 18–25 years. MMN was recorded with pair of stimuli. The pair was having /1000Hz/ and /1100Hz/ with /1000Hz/ as frequent stimulus and /1100Hz/ as the infrequent stimulus. Out of 50 normal hearing subjects, MMN was present only in 33 normal hearing subjects (66%). So clinician should be cautious during interpretation of clinical findings using MMN in abnormal population

Neuro-Physiological Correlates of Voice Onset Time in Kannada and Tamil Speaking

Voice Onset Time (VOT) refers to the time difference between two events—one articulatory and the other laryngeal. VOT is measured as the time difference between the onset of the burst (articulatory event) and the onset of vocal fold vibration (laryngeal event) Lisker [14]. The cross-linguistic variation with respect to voicing perception is more in multilingual countries like India. For example, in Tamil language, there is no good distinction between voiced and unvoiced stops; however, in Kannada, Telugu, and Hindi, there exists a difference. To verify the cross-linguistic difference, the behavioral response for VOT continuum in native Kannada and Tamil speakers, and the neuro-physiological changes for VOT continuum in native Kannada and Tamil speakers were taken as objective of the study. Two groups of subjects were participated in the study. Group I consisted of ten male Kannada speakers in the age range of 20–35 years. All the subjects were native speakers of Kannada language, and they belong to Mysore dialect and they are fluent speakers in Kannada only. All though they were exposed to English, they were not fluent speakers of English or Hindi. Group II consisted of ten male Tamil speakers in the age range of 20–35. All the subjects were native speakers of Tamil language, and they belong to Coimbatore/Chennai dialect and they are fluent speakers in Tamil only. Although they were exposed to English, they were not fluent speakers of English or Kannada or Hindi. From the naturally recorded speech sounds, /da-ta/ continuum was created using copy past synthesis method. This continuum had 10 tokens. Using this stimulus, behavioral identification curve was generated. Also electrophysiological, N100 potential was recorded using Neuro-Scan instrument (Compumedies, AUS) with five tokens, which covers the entire dynamic range of the /da-ta/ continuum. The recording was done with 16 channels. The behavioral result showed there was difference between Tamil and Kannada languages; however, electrophysiological results showed that there was a change with N100 latency with changing VOT but there was no language difference found. The author concluded that N100 may not be an effective measure to indicate to represent the voice /voiceless categorical perception. May be higher potential might give better information.</p

Using energetic models to investigate the survival and reproduction of beaked whales (family Ziphiidae)

Mass stranding of several species of beaked whales (family Ziphiidae) associated with exposure to anthropogenic sounds has raised concern for the conservation of these species. However, little is known about the species' life histories, prey or habitat requirements. Without this knowledge, it becomes difficult to assess the effects of anthropogenic sound, since there is no way to determine whether the disturbance is impacting the species' physical or environmental requirements. Here we take a bioenergetics approach to address this gap in our knowledge, as the elusive, deep-diving nature of beaked whales has made it hard to study these effects directly. We develop a model for Ziphiidae linking feeding energetics to the species' requirements for survival and reproduction, since these life history traits would be the most likely to be impacted by non-lethal disturbances. Our models suggest that beaked whale reproduction requires energy dense prey, and that poor resource availability would lead to an extension of the inter-calving interval. Further, given current information, it seems that some beaked whale species require relatively high quality habitat in order to meet their requirements for survival and reproduction. As a result, even a small non-lethal disturbance that results in displacement of whales from preferred habitats could potentially impact a population if a significant proportion of that population was affected. We explored the impact of varying ecological parameters and model assumptions on survival and reproduction, and find that calf and fetus survival appear more readily affected than the survival of adult females