Psychophysical Tests of the Hypothesis of a Bottom-Up Saliency Map in Primary Visual Cortex (original) (raw)
Figure 1
Prediction of Interference by Task-Irrelevant Features, and Its Psychophysical Test
(A–C) Schematics of texture stimuli (extending continuously in all directions beyond the portions shown), each followed by schematic illustrations of its V1 responses, in which the orientation and thickness of a bar denote the preferred orientation and response level, respectively, of the activated neuron. Each V1 response pattern is followed below by a saliency map, in which the size of a disk, denoting saliency, corresponds to the response of the most activated neuron at the texture element location. The orientation contrasts at the texture border in (A) and everywhere in (B) lead to less suppressed responses to the stimulus bars since these bars have fewer iso-orientation neighbours to evoke iso-orientation suppression. The composite stimulus (C), made by superposing (A) and (B), is predicted to be difficult to segment, since the task-irrelevant features from (B) interfere with the task-relevant features from (A), giving no saliency highlights to the texture border.
(D,E) RTs (differently colored data points denote different subjects) for texture segmentation and visual search tasks testing the prediction. For each subject, RT for the composite condition is significantly higher (p < 0.001). In all experiments in this paper, stimuli consist of 22 rows × 30 columns of items (of single or double bars) on a regular grid with unit distance 1.6° of visual angle.