Neurophysiologic Bases of Speech Discrimination

Abstract

The mismatch negativity (MMN) is an automatic cortical evoked potential that signifies the brain's detection of acoustic change. In other words, the MMN reflects the neurophysiologic processes that underlie auditory discrimination. As such, the MMN provides an objective tool for evaluating central auditory mechanisms involved in speech perception.We are using the MMN to study the central auditory processes that encode acoustic changes important for speech perception in 1) normal-hearing adults and children, 2) individuals with impaired auditory systems (including persons with learning disabilities, attention deficit disorders, cochlear implants), and 3) an animal model. Specifically, we have demonstrated that the MMN provides information about the central processing of fine acoustic differences, the neuroanatomic pathways that encode acoustic change, central auditory processing in the presence of peripheral hearing deficits, and central auditory system plasticity, In addition, we have considered methodological challenges associated with measuring the MMN in individual subjects.Several methodological issues-including appropriate stimuli, stimulus presentation variables, the recording protocol and environment, and validation of the MMN in individuals-are discussed.

Do video sounds interfere with auditory event-related potentials?

“…Kraus, McGee, Carrell, and Sharma (1995) claim that leaving the video soundtrack on at 40 dB SPL has no effect on the auditory mismatch negativity component (MMN; the difference between a listener's ERP to a common standard stimulus and their ERP to a rarer deviant stimulus at around 200 msec; see waveforms in Figure 1 that were measured in this experiment). However, they provide no data to support this claim.…”

O Mismatch Negativity em pacientes com distúrbios do processamento auditivo (central)

“…14,[41][42][43][44][45][46][47][48] Such statistical proof is generally done with a t test based on the mean MMN amplitude in subjects. Table 1 thus shows that MMNs elicited for duration and frequency deviations were statistically demonstrated in the experiment group -(C)APD -and the control group.…”

Spectro-temporal analysis of complex tones: two cortical processes dependent on retention of sounds in the long auditory store

“…Schro Èger et al, 1994Alho et al, 1996;Tervaniemi et al, 1997) and speech sounds (e.g. Kraus et al, 1995). It is generally agreed that the MMN depends on accumulation of the sound pattern in the`echoic memory' or`long auditory store', a pre-perceptual memory which retains the spectro-temporal structure of sounds over a period of several seconds (Cowan, 1984) and permits unattended sounds to be retrospectively perceived and analyzed.…”