The Molecular Mechanism Of Auditory Discrimination Training-enhanced Directional Selectivity In Adult Rats

Sound localization is one of the most important tasks performed by the auditory system. In this study, we used behavioral and molecular biological methods to examine mechanisms underlying the auditory discrimination training-enhanced directional sensitivity of neurons in the primary auditory cortex.Auditory discrimination training enhances directional selectivityThe rats were divided into three groups:(1) EXP rats which were trained to identify a target sound at a specific azimuth angle using a reward-contingent auditory discrimination task;(2) PE rats which were passively exposed to the training procedure but no reward for correct identification of the azimuth angle;(3) CON rats which were housed in a normal environment without auditory training. We investigated the changes of correct, latency and the azimuth deviation. We found that, compared with the aged matched control, EXP rats could be successfully trained to identify a target sound at a specific azimuth angle using a reward-contingent auditory discrimination task while PE rats expressed no significant improvement.GABAA receptor subunits in the adult auditory cortexWe examined the changes in the expression of cortical inhibitory and excitatory receptors by using the western blotting technology. We detected significant increases in GABAA receptor α1, β2,β3subunits; NMDA receptor NR2A, NR2B subunits; and in the ratios of GABAA al/GABAA α3, NR2A/NR2B and NMDA/GABAA. The development of auditory directional selectivity depends on the regulated expression of these excitatory and inhibitory neurotransmitter receptor subunits. Thus, reward-contingent sound-azimuth discrimination training may alter the directional selectivity by interfering with changes in expression of these receptor subunits.