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. 2019 Feb 13;39(7):1195–1205. doi: 10.1523/JNEUROSCI.2492-18.2018

Figure 2.

Figure 2.

Thalamic output responses during cortical development and a refinement of thalamocortical input. A, B, Left, The 3-D tonotopic map in MGBv of an example P17 and a P22 animal. Each dot represents one recording site, with color indicating its CF. Dashed arrow indicates the axis for the low-to-high CF gradient. Right, Color maps show the TRFs of three example sites with low, mid, and high CFs, respectively, with x-axis representing the tone frequency and y-axis representing the tone intensity. Brightness of yellow color indicates the level of evoked firing rates. C, Average BW20 of MGBv responses within each CF range in animals of two different stages. N = 3, 3 animals; n = 17, 25, 10 sites for three CF ranges before refinement and n = 5, 15, 15, 23, 8 sites for five CF ranges after refinement. No significant difference, ANOVA test. All bars represent SD. D, E, TRFs of excitatory input for an example P16 and a P21 neuron. Each small trace represents the average excitatory synaptic current (from 3 trials) evoked by a pure tone of a specific frequency and intensity. Black envelope curve within the red box outlines the frequency tuning curve at 20 dB above the intensity threshold. Color map in the top right corner depicts the peak amplitude of each evoked response in the frequency-intensity space, and below the color map are responses evoked by the CF tone (50 ms, duration marked by the red line) in three individual trials. F, Average BW20 (white) and FWHM (gray) of thalamocortical excitation before and after the refinement (n = 12 and 14 cells respectively). *p < 0.05, t test. Inset, Illustration of how BW20 and FWHM are measured from the frequency tuning curve. G, Average onset latency of thalamocortical excitation (gray, n = 12 and 14) and thalamic spiking responses (black, n = 52 and 66) evoked by CF tones before and after the refinement. ***p < 0.001, t test. Th, thalamic; TC, thalamocortical. H, Average peak amplitude of thalamocortical excitation (gray, n = 12 and 14) and average firing rate of thalamic spiking responses (black, n = 52 and 66) evoked by CF tones. *p < 0.05, t test. I, Average intensity threshold of TRF of thalamocortical excitation (gray, n = 12 and 14) and of thalamic spiking responses (black, n = 52 and 66). All bars represent SD.