Attentional influences in primary visual cortex: an investigation of key task factors

Abstract

Whether or not spatial attention can boost the initial volley of visual processing in V1 remains controversial. In particular, two recent studies failed to replicate an earlier study that found a spatial attention modulation of the earliest, V1-generated component of the human VEP (“C1”). Here, we sought to reconcile these findings through a careful consideration of the computational demands imposed by the target detection tasks. We conducted 3 new experiments. The first sought to elucidate the role of target-non target feature similarity and the second, the level of feedback provided. The third experiment was a close replication of the task conditions of the original experiment. Taking all three experiments together, attention boosted C1 amplitude. However, this effect was present in only the second and third experiments, with the first showing a modulation in the reverse direction. This reversal coincided with differing behavioural results, perhaps reflecting different strategies employed by participants to carry out the task. Thus, although these findings affirm our general hypothesis that the determining factor for attentional modulation of the very earliest sensory representations relates to the precise computational demands of the perceptual task, further work is needed to pinpoint the computational principles that the attention system follows.