Figure 7.

A thalamocortical network model. A, Schematic drawing of the network configuration. The pyramidal neurons in layer 4 receive input from three sources: direct input from thalamic neurons and feedforward intracortical excitation and inhibition from cortical excitatory and inhibitory interneurons driven by thalamic afferents. B, Top, Temporal profiles of synaptic conductances in the pyramidal neuron. The amplitudes are for the responses to the BF tone. Bottom, Tuning curves of peak synaptic currents evoked under simulated voltage-clamp conditions (at −70mV for excitatory currents and 0 mV for inhibitory currents). C, Top, Spike latency tuning for the pyramidal neuron under three conditions: with the thalamic input only (green), with combined thalamic and intracortical excitatory inputs (red), and with all inputs including inhibition (blue). Middle, Tuning of integration time under the three conditions. Bottom, Tuning of relative spike latency. D, Relay of latency tuning from the thalamus to the cortex. Top, Spike latency tuning for individual thalamic neurons defined in the model. Middle, Latency tuning of the aggregate thalamic input received by individual pyramidal neurons in layer 4. Bottom, Spike latency tuning of individual pyramidal neurons. E, Spike latency tuning of a pyramidal neuron with 20 Hz background activity added to all cortical neurons. Data are averaged from 100 running trials. Whiskers indicate SE. F, Spike latencies of all pyramidal neurons (800 neurons) in response to a middle-frequency tone in the network model. Neurons are indexed according to their characteristic frequency. Right, Histogram for the distribution of first spike latencies. Bin size, 0.5ms.