Early stage of life is characterized by increased excitability of the auditory cortex in both humans and rats

ABSTRACT Auditory evoked response (ER) undergoes notable changes during childhood and likely reflects changes in synaptic signaling in the auditory cortex. Establishing the interspecies generalizability of electrophysiological indicators of cortical maturation would offer a means to better understand the neurodevelopment of the human brain. We measured cortical ERs to simple auditory probes in three age groups of human subjects and juvenile rats. These two species exhibited a remarkably similar long-latency (150–350 ms poststimulus) response in the auditory cortex, specifically pronounced in the younger individuals in both species. An age-dependent pattern of activity was evident at the level of single trials, and the late response showed stronger trial-by-trial stability in children than the early, adult-like 100-ms response, especially in humans. This robust development-related pattern of sensory cortex excitability is likely to represent a distinct synaptic event and may be a marker of the maturational stage, especially in GABAergic cortical circuits.