Figure 2. Spike-timing computations based on retinal spike trains.

(A) Schematic of the modeled readout neuron. The neuron receives input from multiple afferents (top left). Each afferent spike produces a PSP of stereotyped shape with an amplitude that depends on the synaptic strength (insets top right, x-scale = 20 ms, y-scale = spike threshold). For some RGC spike patterns (e.g. the one in blue), excitatory and inhibitory input spikes arrive segregated in time such that the resulting PSPs sum to a peak voltage, , above the spike threshold (), and the model neuron fires an action potential (bottom left, blue trace). For other patterns (e.g. red), excitation and inhibition interfere such that the peak voltage (red trace) remains below threshold and the model neuron remains silent. (B) Two visual categorization tasks based on the grating stimuli. Top: The luminance task asks whether a particular location in the field (dotted line) is bright (left) or dark (right). The readout neuron should fire in the former case but not in the latter; the opposite rule is another version of this task. Bottom: The boundary task asks whether a particular location (dotted line) has a boundary of either polarity (left) or no boundary (right).