期刊
JOURNAL OF NEUROSCIENCE
卷 39, 期 7, 页码 1195-1205出版社
SOC NEUROSCIENCE
DOI: 10.1523/JNEUROSCI.2492-18.2018
关键词
auditory cortex; developmental refinement; synaptic circuit mechanism; thalamocortical projection; tonal receptive field; whole-cell recording
资金
- National Institutes of Health (NIH) [R01DC008983]
- David and Lucile Packard Foundation
- NIH [K99EY029002, R01EY019049, R01EY022478]
In the primary auditory cortex (A1) of rats, refinement of excitatory input to layer (L) 4 neurons contributes to the sharpening of their frequency selectivity during postnatal development. L4 neurons receive both feedforward thalamocortical and recurrent intracortical inputs, but how potential developmental changes of each component can account for the sharpening of excitatory input tuning remains unclear. By combining in vivo whole-cell recording and pharmacological silencing of cortical spiking in young rats of both sexes, we examined developmental changes at three hierarchical stages: output of auditory thalamic neurons, thalamocortical input and recurrent excitatory input to an A1 L4 neuron. In the thalamus, the tonotopic map matured with an expanded range of frequency representations, while the frequency tuning of output responses was unchanged. On the other hand, the tuning shape of both thalamocortical and intracortical excitatory inputs to a L4 neuron became sharpened. In particular, the intracortical input became better tuned than thalamocortical excitation. Moreover, the weight of intracortical excitation around the optimal frequency was selectively strengthened, resulting in a dominant role of intracortical excitation in defining the total excitatory input tuning. Our modeling work further demonstrates that the frequency-selective strengthening of local recurrent excitatory connections plays a major role in the refinement of excitatory input tuning of L4 neurons.
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