Sample of cells in the test of unidirectionality
| Stimulus set | Both | Density– size | Gradient– direction | Total |
|---|---|---|---|---|
| Significant modulation | 92 | 51 | 8 | 151 |
| Position invariance tested | 71/92 | 33/51 | 5/8 | 109/151 |
| Unidirectional | 21/71 | 0/33 | 0/5 | 21/109 |
Sensitivities to the density–size and gradient-direction stimulus sets were tested in 170 V4 cells: 151 exhibited statistically significant modulation in response to at least one of the stimulus sets; the invariance of the directional tuning with respect to the position of the elements was tested in 109 cells; 21 were classified as unidirectional.