The Responses Of Neurons In The Rat Primary Auditory Cortex To Sound Stimulus Duration

Duration is an important feature of sound. Previous studies have described neurons that were selective for sound duration in the inferior collicular neurons, but few studies were focused on the primary auditory cortex.The present study used extracellular recordings to investigate the tuning characteristics of neurons in the rat primary auditory cortex (AI) to sound duration, and analyzed whether the selectivity for sound duration were tolerant at different sound levels.Previous studies have shown that responses of A1 neurons were changed with sound stimulus history. The responses of neurons in AI can be affected by a forward stimulus. The present study further investigated whether the selectivity of A1 neurons to sound duration was tolerant to forward noise. The findings are as follows:1. The tuning characteristics of neurons in the rat primary auditory cortex to sound durationThe present study investigated responses of 76 neurons in the rat AI to sound duration. The tuning of AI neurons to sound duation can be classified to six types: short-pass, band-pass, long-pass, band-off, all-pass and complex. When the sound level is 10 dB above the minimumthreshold (MT) of AI neurons, there are 6 short-pass neurons,8 band-pass neurons, and 2 long-pass neurons.These neurons are duration selectivity neurons at this sound level.We found that 21%(16/76) of the neurons were duration selective at 10 dB above MT. However, the duration selectivity of these neurons were changed when the sound level varied.Thus, the duration selectivity of these neurons were not level-tolerant. The results of the present study are different with the findings in bat auditory cortex, which suggest that the distribution of duration selective neurons is different in different species. The results suggest that the duration selective neurons found in AI may not specifically deal with sound duation information. 2 The effect of forward noise on duration selectivity of neurons in the rat primary auditory cortexThe present study investigated responses of 76 neurons to sound duration in the rat primary auditory cortex under forward noise conditions. The results showed that the neurons exhibitednon-selective to sound duration were still non-selective under forward noise, and the duration selective neurons could be varied under forward noise conditions. However, we did not find specific patten of change. The total proportion of duration selective neurons were not significantly changed under forward noise conditions. These results suggested these duration selective neurons in the rat auditory cortex were not tolerant to noise and may not specifically deal with the sound duration information.