Plasticity Of Characteristic Frequency In Rat Auditory Cortical Neurons During Postnatal Development

Using conventional electrophysiological technique, we investigated auditory response properties and the plasticity of characteristic frequency (CF) of neurons in rat auditory cortex (AC) at postnatal age of two , three , four , five , six and eight week by determining CF and frequency tuning curve (FTC) shifts of neurons.1. Auditory response properties and neurons in rat auditory cortex (AC) at postnatal age of two , three , four , five , six and eight week.(1). The older is the age, the larger is the characteristic frequency (CF) ; characteristic frequency (CF) is much lower, when at postnatal age of two, three week.(2). The older is the age, the less is the mean minimum threshold and mean latency of the auditory cortex, the younger is the age, the minimum threshold of the auditory cortex is higher and latency of the auditory cortex.(3). The older is the age, the larger is mean Q₁₀-dB values of the auditory cortex.(4). The younger is the age, the more broad of frequency tuning curve (FTC) in the auditory cortex; there was multipeak, when at postnatal age of two, three week. 2. The plasticity of characteristic frequency (CF) of neurons in rat auditory cortex (AC) at postnatal age of two , three , four , five , six and eight week.(1). When the frequency difference between conditioned stimulus frequency (CSF) and the CF of neuron was in 1.0 kHz or 2.0 kHz with conditioned stimulation, conditioned stimulus can induce CF shift toward higher frequency side (HFS), lower frequency side (LFS) and both sides (BLH) of neuron's FTC.(2). The proportion of CF shift becomes lower and the proportion of non CF shift becomes higher with the increasing of the age.(3). Neurons with bigger Q10-dB value of the FTC, increasing of the proportion of CF shift toward higher frequency side (HFS) of neuron's FTC is much higher.(4). Neurons with symmetry index >0 of the FTC, increasing of the proportion of CF shift toward higher frequency side (HFS) of neuron's FTC is much higher.(5). There is significant correlation between the time course and the age of rat, the older is the age, the longer is the shift time (p<0.05) and the recovery time (p<0.05) of neurons.These findings also provide evidence for further study of plasticity mechanisms in sensory function of the brain.