Fig. 3.
Rate-specific synchrony underlies MAE computation. (a) Model network used to test MAE computation in the presence of noisy oscillations. Each neuron in the population receives independent time-varying excitatory drive (I1–I10) and a common oscillatory input (Icommon). All 10 neurons provide synaptic input to a postsynaptic read-out neuron (R) that reports population synchrony by generating action potentials. (b) To reproduce this model experimentally, a single L2/3 cell was injected with 10 waveforms of 10-s duration. During the first 3.5 s, waveforms linearly converge from 10 distinct levels, remain fixed at a common value for 3 s, followed by another 3.5-s interval, during which they linearly diverge to 10 distinct levels. The time-averaged stimulus amplitude is identical for each epoch, as illustrated by waveform color coding: A high initial level is matched with a low final level, and vice versa, to guarantee identical time-averaged stimulus amplitudes across waveforms. During the experiment, a common noisy oscillatory stimulus with Fc = 30 Hz, Fw = 30 Hz, and Arms = 50% was added to each waveform in b to create stimuli for 10 stimulus epochs. (c) Spike rasters for all 10 stimulus epochs sorted by increasing initial constant current level and color-coded to match b. Stimulus epochs were presented in a random order during the experiment. (d) Spike rasters from each stimulus epoch were convolved with the EPSP kernel (τ = 2 ms) and summed to mimic synaptic input to a coincidence detector postsynaptic to 10 neurons. A threshold of six events was applied to detect population synchrony. (e) Ticks indicate threshold-crossing events in d. Population synchrony is greatly enhanced during the time period when all firing rates are approximately equal. (f) Average firing rate across all 10 epochs calculated by counting spikes in sequential bins of 220 ms. Average firing rate remains unchanged across time.