Synaptic Circuit Mechanism Of Auditory Information Processing In Awake Mouse Primary Auditory Cortex

The arithmetic nature and underlying synaptic mechanisms of auditory informationin processing in the primary auditory cortex(Al)remain unclear.The first part is a review of the cellular and functional characteristics of Al,which is important to integrate binaural information and response to band-pass noise.In the second part,we employed cell-attached and whole-cell recordings to examine the responses of Al neurons to tone pips at different frequencies and intensities given to the contralateral,ipsilateral ear separately or simultaneously to both ears in a random sequence.The results showed that the inputs from ipsilateral sound stimulation could regulate the responses to the contralateral,but did not affect the tuning curve of L4 response to the bilateral stimulaition.In addition,there is a layer specificity in the two ear integrated neuron distribution,and the ipsilateral acoustic input can enhance the excitability of the L4 contralateral reaction and the inhibition of the L6 contralateral reaction.When muscimol was used to silence the contralateral auditory cortex,the integration of L4 and L6 in two ears disappeared.When ipsilateral L6 was destroyed,the excitatory phenomenon of L4 neurons was enhanced by ipsilateral enhancement.In other words,the contralateral cortex projected an inhibitory pathway to L6 of the ipsilateral cortex,causing the ipsilateral acoustic input to inhibit the contralateral response of the L6 neurons;After the ipsilateral L6 was silent,the phenomenon of L4 associated with the increase of the excitatory gain factor disappeared.It shows that excitatory inputs in cortical layer 4 reinforced by ipsilateral acoustic stimulation through the modification from contralateral auditory cortex to ipsilateral layer 6.In the third part,we separately extracted the CF from those responses in L6,and found that the ipsilateral response neurons in L6 were able to modify the contralateral CF.