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Extended Data Fig. 2 | Illustration of classical and inverse-tuned neurons.
a, Classical(-only) neuron. Left, the response of a neuron probed with classical
stimuli (black) increases with the size of the stimulus until it peaks at the
preferred size of the neuron (top horizontal dotted line). The response then
decreases owing to surround suppression (maximum suppressed level
indicated by the lower dotted horizontal line). The response of the same
neuron probed with inverse stimuli (red) starts at the maximally surround
suppressed activity level (an inverse stimulus with a size of 0° is a full-field
grating) and then decreases as the diameter of the grey patch increases,
consistent with visual stimulation being progressively removed from the
classical ff RF. Right, schematic of the ff RF of a neuron surrounded by its
classical suppressive zone. b, Inverse-tuned neuron. Left, the response of the
neuron probed with inverse stimuli (red) starts, as for the classical-only neuron,
at the maximally surround suppressed activity level but then increases until it
reaches the preferred inverse stimulus size of the neuron and decreases with
larger diameters of the grey patch, consistent with visual stimulation being
progressively removed from the f bRF. Right, schematic of the ff RF of a neuron
surrounded by its f bRF. c, Four example stimuli: Two classical stimuli (1 and 2 of
sizes x and y, respectively) and two inverse stimuli (3 and 4, also of sizes x and y,
respectively). The inner dotted circle represents the outer border of the
classical ff RF. The outer dotted circle represents the outer border of the
suppressive region and, for inverse-tuned neurons, also the outer border of the
f bRF. The response amplitudes to the four example stimuli (1 to 4) in a
classical-only neuron and in an inverse-tuned neuron are marked in a and b,
respectively, at the intersection between the green vertical lines (stimulus size)
and the size-tuning functions.