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Tone Rearing and Tonotopic Patterning in Mice One of the well-established methods of studying tonotopic patterning in the auditory cortex during development is tone-rearing. In mouse Primary Auditory Cortex (A1), different neurons respond to different ranges of frequencies with one particular frequency eliciting the largest response – this is known as the "best frequency" for a given neuron. Exposing mouse pups to one particular frequency during the auditory critical period (postnatal day 12 to 15) will shift the "best frequencies" of neurons in A1 towards the exposed frequency tone.

These frequency shifts in response to environmental stimuli have been shown to improve performance in perceptual behavior tasks in adult mice that were tone-reared during auditory critical period. Adult learning and critical period sensory manipulations induce comparable shifts in cortical topographies, and by definition adult learning results in increased perceptual abilities. The tonotopic development of A1 in mouse pups is therefore an important factor in understanding the neurological basis of auditory learning.

Other species also show similar tonotopic development during critical periods. Rat tonotopic develop is nearly identical to mouse, but the critical period is shifted slightly earlier, and barn owls show an analogous auditory development in Interaural Time Differences (ITD).

Plasticity of Auditory Critical Period The auditory critical period of rats, which lasts from postnatal day 11 (P11) to P13 can be extended through deprivation experiments such as white noise-rearing. It has been shown that subsets of the tonotopic map in A1 can be held in a plastic state indefinitely by exposing the rats to white noise consisting of frequencies within a particular range determined by the experimenter. For example, exposing a rat during auditory critical period to white noise that includes tone frequencies between 7kHz and 10kHz will keep the corresponding neurons in a plastic state far past the typical critical period–one study has retained this plastic state until the rats were 90 days old.