Neuronal correlates of contour integration and curve tracing in primary visual cortex (area V1).

<p>A) Contour integration task. If monkeys have been trained to make a saccade to a pattern with a string of collinear contour elements (1, 3, 5, 7 or 9 collinear bars, left panel), the neuronal responses in V1 elicited by these elements are stronger than the responses elicited by a single line element that is not part of such a perceptual group (right panel). This influence of colinearity on V1 activity is not present before training. The purple circle in the upper panel illustrates the V1 receptive field. Re-drawn from [<a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1004489#pcbi.1004489.ref015" target="_blank">15</a>]. <b>B)</b> Curve-tracing task. Monkeys were trained to mentally trace a target curve (T) that is connected to a fixation point (FP) because they had to make an eye movement to a larger red circle at the end of this curve. They had to ignore a distractor curve (D). After training in this task, V1 activity elicited by the target curve (red response in lower panel) became stronger than that elicited by the distractor (blue response). The green circle in the upper panel shows the V1 receptive field. Adapted from [<a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1004489#pcbi.1004489.ref017" target="_blank">17</a>].