Details of stimuli have been described before11. We copy these description here for ease of access. Stimuli consisted of either central Gabor elements presented in isolation or flanked by two iso-oriented flankers. The orientation and spatial frequency of the Gabors matched the neuron’s preference (see below). Each Gabor moved within a Gaussian aperture at 4 Hz temporal frequency. The motion was perpendicular to the Gabor’s orientation, and reversed direction at a frequency of 4 Hz. Within the sequence of 4 presentations per trial the order of stimulus presentation within a trial and between trials was randomised.

Central and flanker Gabors were identical in all respects except for their contrasts. The contrast of the central Gabor was varied between 0, 4, 8, 12, 16, 24, 32, and 64% (Michelson contrast), while the contrast of the flanking Gabors was fixed at 48%. The distance between the central and flanking Gabors could be 1, 2 or 3–4 times the Gabor wavelength (λ). The exact wavelength varied slightly with the spatial frequency preference. High spatial frequencies of for example 6 cyc/° would result in centre flanker distances of 0.166° at a distance of 1λ, whereby the receptive field centre would be filled by flankers. To account for this we used distances of 1.5, 2.8, and 4λ for spatial frequencies of ≥ 6 cyc/°, and distances of 1, 2, and 3λ for spatial frequencies of < 6 cyc/°. The large majority of our neurons preferred spatial frequencies of ≤ 4 cyc/° and only 8 neurons were measured with ≥ 6 cyc/°. We included them in our overall sample and treated them as if the wavelengths had been 1, 2, and 3λ, respectively. We also scaled the size of our stimuli, whereby the half width at half height of the Gaussian envelope was 0.3 times the spatial frequency for spatial frequencies of < 2 cyc/°, it was 0.4 times the spatial frequency for spatial frequencies between 2 cyc/° and 4 cyc/°, 0.5 times the spatial frequency for spatial frequencies between 4 cyc/°, and 6 cyc/°, and 0.6 times the spatial frequency for spatial frequencies of ≥ 6 cyc/°.

Twenty trials per stimulus, contrast, and drug application conditions were recorded in most recordings. Cells were excluded if fewer than 10 trials per stimulus, contrast, and drug application conditions were available.

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