Development of contralateral and ipsilateral frequency representations in ferret primary auditory cortex

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Developmental Neuroscience

Background:

• The maturation of functional maps in the primary auditory cortex (A1) following sensory experience onset is not well understood.
• Understanding A1 map development is crucial for comprehending auditory processing in juvenile animals.

Purpose of the Study:

• To investigate the developmental trajectory of tonotopic organization in the ferret primary auditory cortex (A1).
• To compare the maturation of auditory maps in response to contralateral and ipsilateral auditory stimuli.

Main Methods:

• Intrinsic signal imaging was employed to observe sound-evoked activity in the ferret A1.
• Pure tone stimuli were used to map tonotopic organization across different postnatal ages.
• Cortical activation area and response magnitude were quantified for both contralateral and ipsilateral ear stimulation.

Main Results:

• Tonotopic maps emerged by postnatal day 36, shortly after hearing onset.
• The cortical representation of each octave increased with age, with a notable expansion for frequencies above 4 kHz after postnatal day 60.
• Initially, both ears evoked similar responses, but in older animals, contralateral stimuli elicited stronger responses and larger cortical areas.

Conclusions:

• The tonotopic organization and the representation of inputs from each ear in A1 are not fully mature until approximately one month after hearing onset.
• These developmental changes in A1 map organization have significant implications for auditory signal processing in young animals.