ERP evaluation of auditory sensory memory systems in adults with intellectual disability

Auditory sensory memory stage can be functionally divided into two subsystems; transient-detector system and permanent feature-detector system (Naatanen, 1992). We assessed these systems in persons with intellectual disability by measuring event-related potentials (ERPs) N1 and mismatch negativity (MMN), which reflect the two auditory subsystems, respectively. Added to these, P3a (an ERP reflecting stage after sensory memory) was evaluated. Either synthesized vowels or simple tones were delivered during a passive oddball paradigm to adults with and without intellectual disability. ERPs were recorded from midline scalp sites (Fz, Cz, and Pz). Relative to control group, participants with the disability exhibited greater N1 latency and less MMN amplitude. The results for N1 amplitude and MMN latency were basically comparable between both groups. IQ scores in participants with the disability revealed no significant relation with N1 and MMN measures, whereas the IQ scores tended to increase significantly as P3a latency reduced. These outcomes suggest that persons with intellectual disability might own discrete malfunctions for the two detector systems in auditory sensory-memory stage. Moreover, the processes following sensory memory might be partly related to a determinant of mental development.