Maturation of mismatch negativity: a scalp current density analysis.

OBJECTIVE: Auditory evoked potentials provide the opportunity to better understand the central processing of auditory stimuli, which is the basis of speech and language perception. The purpose of this study was to examine maturational changes in the topography of one of these auditory evoked potentials, the mismatch negativity (MMN), using scalp current density (SCD) analysis. DESIGN: Subjects were children ages 4 to 11 yr (N = 53), and adults (N = 12). Stimuli were 85 dB peSPL 1000 Hz standard tones and 1200 Hz deviant tones (deviant probability = 0.15). Auditory evoked potentials were recorded using surface electrodes placed at 32 locations on the head while subjects ignored the stimuli by watching a silent video. RESULTS: Significant maturational changes in topography of MMN were seen over frontal and left lateral sites. CONCLUSIONS: Differences in MMN for the children compared to adults indicate that the MMN generators or their orientation, and thus the neural processes underlying discrimination of simple tones, are not yet mature by 11 yr of age.

Maturation of mismatch negativity in typically developing infants and preschool children.

OBJECTIVE: 1) To determine whether an adult-like mismatch negativity (MMN) can be reliably elicited in typically developing awake infants and preschool children, and if so 2) to examine whether maturational changes exist in MMN latencyand amplitude. DESIGN: Two experiments were designed to elicit MMN using an "oddball" paradigm. In Experiment 1, a 1000-Hz tone served as the standard stimulus and a 1200-Hz tone as the deviant. In Experiment 2, a 1000-Hz standard stimulus and a 2000-Hz deviant were presented. Infants' ages ranged from 2 to 47 and 3 to 44 mo in Experiments 1 and 2, respectively. RESULTS: In Experiment 1, a negativity was not elicited in the majority of the infants and preschoolers tested. In Experiment 2, a negativity was reliably elicited in the infants and preschoolers across all ages. A significant negative correlation was observed between age and latency, but not for age and amplitude for this negativity. This negativity was found to decrease at a rate of 1 msec/mo. Infants younger than 12 mo of age showed a significantly larger positivity to the deviant than to the standard between 150-300 and 200-300 msec in Experiments 1 and 2, respectively. CONCLUSIONS: The discriminative processes indexed by MMN in response to frequency changes areimmature in infants and preschool children. Although there is convincing evidence that the negativity elicited in Experiment 2 is an immature MMN, the possibility that it may be an "obligatory effect" indexing recovery from refractoriness cannot be ruled out at this time. The results from these experiments suggest that the MMN component haslimited use as a clinical tool at this time for infants and young children.