Mismatch negativity and frequency representational width in children with specific language impairment.

The aim of this study was to compare the degree of frequency separation that is required between tones to generate mismatch negativity (MMN) in a group of children with specific language impairment (SLI) and a comparison group, who had their temporal processing abilities assessed in a previous experiment. Using a 1000Hz standard (85%) and 1020, 1050, and 1100Hz deviant tones presented at inter-stimulus intervals (ISIs) of 200 and 400ms, MMN was compared in 19 children with SLI (13 males, six females, age range 7y 4mo-11y 10mo, mean age 9y 7mo [SD 1y 2mo]), and 19 comparison children (13 males, six females, age range 7y 3mo-11y 4mo, mean age 9y 5mo [SD 1y 3mo]). Temporal processing ability was assessed by the Auditory Fusion Test-Revised. Children with SLI who had poor temporal processing abilities generated a positive mismatch response (P-MMR) for 2% tone contrasts at 400ms ISI but MMN with larger contrasts. These children also generated stronger MMN than the comparison group at 200ms ISI for 2% contrasts. Children with SLI who had good temporal processing abilities generated only P-MMR in response to contrasts up to 10% for both ISIs. Some children with SLI show an inverse relationship between frequency discrimination and temporal processing. Furthermore, certain stimulus-related and biological criteria may need to be met for P-MMR to switch to MMN.