| The amygdaloid complex is one of crucial structures of the limbic system. The amygdaloid complex was convinced to be broad related with emotion, memory, and sense function of animals. LeDoux JF and McDonald RJ et al found that amygdala received auditory information from MGB and the auditory cortex, and was involved with emotion activities such as the auditory fearing. On the other hand, Zhou ShaoCi et al proved that amygdala could effect the acoustic response evoked by click on MGB and cortex level. However according to the view of acoustics, click includes mixed frequencies, so further studies are necessary to investigate the physiological significance of amygdaloid modulating effect on the ascending auditory information at the cortical level. In this paper we firstly observe the characteristics of the acoustic response of neurons in A- I evoked by pure tone; then investigate the influence of LA stimulation on the acoustic response of these neurons and the physiological significance of such influence; reveal the neural pathway mediating this effect with the neurohistological method; and study the neurotransmitter and its receptor participating in this effect. The main results are as follows:(1) Firstly we investigated the basic characteristics of the acoustic response of A-I neurons to burst tone. 226 auditory neurons were recorded in our experiment. The patterns of the acoustic response of A-I neurons includes ON-response, ON-OFF response, sustained response, and OFF response. The proportion of these responses was 35%, 39.8%, 10.2%,and 9.7% respectively. Furthermore the ON response can be also classified into several subtypes such as single ON response, single-inhibition response, burst response, and burst-inhibition response. The ON-OFF response can also been classified into a few subtypes according to the different characteristics of the ON- and OFF-response element. The response latency varied from 8 ms to 60 ms, but 92% neurons have their response latency within the range from 8 to 14 ms. The form of acoustic response of A- I neurons was closely related with the stimulation parameters of the burst tone. The changing of the intensity, frequency, or duration of the pure tone can effect the discharge and patterns of the acoustic response of these cortical neurons observed. For example, it was found at some ON-OFF neurons that the change of the intensity, frequency or duration ofthe pure tone could result in inhibiting or even disappearing of the ON-response or OFF-response. The diversity of the acoustic response of A- I neurons and the correlation of their response patterns with the parameters of the pure tone, indicate the complexity of their encoding auditory information.(2) Our experimental results have shown the topographycal distribution of the CFs of neurons in A- 1 .Generally the neurons with high CFs laid in the rostral part of A- 1 , and the neurons with low CFs laid in its caudal part. The similar isofrequency strip was observed in A-I cortex. The topology of CFs in A- 1 indicated the rule of the neural projection from GMB to primary auditory cortex. The tuning curves of 34 neurons have been recorded and analyzed. The results showed that the tuning curves of neurons can be classified into " V " , " W" , and " U " types, and its proportions was 88%, 8%, and 4% respectively. Q10 values of A- I neurons varied from 0.8 to 10.2. The fact that Q10 values increase with increasing of the CFs of neurons indicated that neurons with high CFs had more powerful frequency selectivity ability than that with low CFs. Q30 values of A- I neurons were within from 0.24 to 3.36. The values of Q30 can also increase with increasing of CFs of neurons, which indicated that the frequency range of acoustic response of A- 1 neurons widened with increasing of CFs of these neurons.(3) In recent paper the influence of LA stimulation on the acoustic response of A- I neurons has been emphatically studied. The experimental results of 139 neurons showed that the acoustic response of 31.7% neurons was inhibited wh...
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