Saccades Compress Space, Time, and Number

This chapter focuses on space, time, and number as visual primitives and effects of saccades on them. The intraparietal sulcus (IPS) and the prefrontal cortex (PFC) of the primate are both involved in encoding of space, time, and number. Neurons tuned to number have been identified in nonhuman primates in parietal areas including the Ventral Intra-Parietal (VIP) area and the Lateral Intra-Parietal (LIP) area, as well as in a lateral pre-frontal region. If spatial, temporal, and numeral representations share a neural substrate in the posterior parietal cortex, and if visual responses on these areas are strongly affected by saccadic eye movement, then saccades should interfere in similar ways with the perception of all three perceptual attributes: space, time, and number. A pair of bars flashed 100 ms apart is seen veridically when displayed well before or after saccadic onset, but near saccadic onset the apparent interval between them is strongly compressed, to about half its true value.