Sequential organization of critical periods in the mouse auditory system
Mari Nakamura1, Patricia Valerio1, Stitipragyan Bhumika1, Tania R Barkat1, 2
1Department of Biomedicine, Basel University, Basel, Switzerland
Critical periods are time windows of heightened plasticity during postnatal brain development. They are specific to sensory features and do not all happen at the same time. For example, the critical period for pure tone precedes the critical period for frequency modulated sweep (FMS) by about two weeks. Whether such critical periods are timed by a temporally precise developmental program or sequentially organized, where the closing of one window triggers the opening of the next, is not known. We used in vivo electrophysiological recordings in combination with molecular and sensory manipulations to elucidate the biological constraints on critical period timing in the mouse auditory system. Passive sound exposure during development shows that the cortical representation of the two sound features pure tone and FMS are not influencing each other. Enhancing g-aminobutyric acid (GABA) function before the critical period for pure tone accelerated it without changing the critical period for FMS. Similarly, delaying by ten days the critical period for pure tone by rearing mice in white noise (WN) had no effect on the critical period for FMS. However, the critical period for FMS started only if the critical period for pure tone had occurred. Together, these results indicate that distinct critical periods, although sequentially organized, can be temporally shifted independently of each other and are therefore timed by a temporally precise development program. Our findings shed new light on the dependence of sensory features on each other and on the mechanisms at play in developmental plasticity.
Cell Reports, August 2020