Abstract
In a backward masking paradigm, a target stimulus is rapidly (<100 ms) followed by a second stimulus. This typically results in a dramatic decrease in the visibility of the target stimulus. It has been shown that masking reduces responses in V1 (1,2). It is not known, however, what process in V1 is affected by the mask. In the past we have shown that in V1, modulations of neural activity can be recorded that are specifically related to figure-ground segregation (3). Here, we recorded from awake macaque monkeys, engaged in a task where they had to detect figures from background in a metacontrast backward masking paradigm. We show that the V1 figure-ground signals are selectively and fully suppressed at target-mask intervals that psychophysically result in the target being invisible. Initial response transients are not affected. As figure-ground modulations depend on feedback from extrastriate areas (4), these results suggest that masking selectively interrupts the recurrent interactions between V1 and higher visual areas.
(1)
BridgemanB. (1980). Temporal response characteristics of cells in monkey striate cortex measured with metacontrast masking and brightness discrimination. Brain Res., 196: 347–364
(2)
MacknikS. L.LivingstoneM. S. (1998): Neuronal correlates of visibility and invisibility in the primate visual system. Nature Neuroscience, 1: 144–149
(3)
LammeV. A. F. (1995). The neurophysiology of figure-ground segregation in primary visual cortex. J. Neurosci., 15: 1605–1615.
(4)
LammeV. A. F.SupørH.SpekreijseH. (1998): Feedforward, horizontal, and feedback processing in the visual cortex. Curr. Opin. Neurobiol., 8, 529–535