A collection of fragments of understanding in the pursuit of deeper questions.
Hubel & Wiesel found out that certain cells, called hypercomplex cells, showed a decrease in response when the stimulus exceeds the border of the cell receptive field. This phenomenon takes the name of surround suppression.
Surround Suppression Example
Decreasing firing rate with increasing stimulus size outside the classical receptive field.
Surround and Saliency
In the figure, we have the same sinewave grating presented 3 times with different surrounds. It can be noticed that changing the surround gives us the sense of an increased contrast. When the surround stimulus orientation is different, the stimulus becomes more salient and "pops out" from the background.