Sequential Organization of Critical Periods in the Mouse Auditory System

Critical periods-time windows of heightened plasticity in postnatal development-are specific to sensory features and are asynchronous. Whether they are timed by a temporally precise developmental program or are sequentially organized is not known. We use electrophysiology and molecular or sensory manipulations to elucidate the biological constraints on critical period timing. Passive sound exposure shows that the cortical representations of two sound features, pure tone and frequency-modulated sweep (FMS), are not influencing each other. Enhancing inhibition before the critical period for pure tone accelerates it without changing the critical period for FMS. Similarly, delaying the critical period for pure tone with white noise exposure has no effect on the critical period for FMS. However, the critical period for FMS starts only if the one for pure tone has occurred. Together, these results indicate that distinct critical periods, although sequentially organized, can be temporally shifted independently of each other.