Bone conducted responses in the neonatal rat auditory cortex.

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Developmental Neuroscience

Background:

• Rats are born deaf, with auditory canals opening at the end of the second postnatal week.
• Low-intensity sounds begin to elicit auditory cortex responses after ear canal opening.

Purpose of the Study:

• To investigate the early auditory system's response to bone-conducted (BC) sounds in developing rats.
• To determine the pathways and timing of BC sound processing in the auditory cortex before functional hearing onset.

Main Methods:

• Utilized micro-Electrocorticography (μECoG) electrode arrays for cortical recordings.
• Employed intracortical silicon probes for detailed neural activity mapping.
• Recorded responses to bone-conducted sounds from postnatal day (P) 8 onwards.

Main Results:

• Bone-conducted (BC) sounds evoked biphasic responses in the auditory cortex starting from postnatal day (P) 8.
• The initial response phase involved thalamocortical input, followed by intracortical propagation in supragranular layers.
• BC-evoked responses overlapped with those from cochlear electrical stimulation and inferior colliculus stimulation prior to P13, and with air-conducted sounds post-P13.

Conclusions:

• Bone-conducted sound signals reach high-frequency processing regions of the auditory cortex well before the onset of low-threshold hearing (P13).
• These findings demonstrate the early integrity and functional capability of the developing auditory system in rats.
• BC sound provides a pathway for auditory information processing during early development.