Fig. 2: Cortico-cortical feedback is relatively suppressive of topographically matched centre locations and relatively facilitating of mismatched surround locations.
From: Cortico-cortical feedback engages active dendrites in visual cortex
a, Left, retinotopic map in azimuth used to assign recorded neurons to a cortical area was obtained by smoothing cellular-resolution maps constructed using sparse noise stimuli and two-photon population imaging. Right, smoothed retinotopic map in elevation. b, Left, example photostimulation group in LM (probing functional connectivity in the feedback direction) and the corresponding retinotopic location in V1. Right, measurement of the absolute retinotopic (rather than physical) distance of an example across-border responder to a photostimulated cluster. c, The probability distribution of responder retinotopic distances divided by the probability distribution of distances for all available neurons. Data are mean ± s.e.m. across stimulation groups. n = 129 (LM) and n = 180 (V1) clusters from 42 sessions in 11 animals. The horizontal grey lines mark y = 1 and represent uniform spatial sampling. Suppressed responders are plotted downwards by convention. Red arrow indicates the location of stimulation, the green arrow indicates the location of responders measured. Top, stimulation and readout in V1. Bottom, stimulation and readout in LM. d, The same as in c, but for interareal stimulation and readout, and also including the average retinotopic location of responders for each stimulation group (red and blue dots), which were used to make the comparison. Top, stimulation in V1 and readout in LM (feedforward). Bottom, stimulation in LM and readout in V1 (feedback). Feedforward-facilitated and feedforward-suppressed responders do not differ in spatial distribution (centroids over stimulation groups, rank-sum test, P = 0.61). Feedback-facilitated and feedback-suppressed responders are displaced relative to each other (rank-sum test, P = 9.2 × 10−5). NS, not significant. e, Schematic illustrating the suppressive feedback from retinotopically aligned and facilitating feedback from retinotopically offset projections.
