Abstract

Abstract – Attention to low-level visual features can alter the activity of neurons in visual cortex. In principle we expect attention to select the neurons most sensitive to changes in the feature being attended. This means that the precise nature of the neuronal responses may depend on both task and stimulus. Here, we used magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) to examine modulations of neural activity in visual cortex driven purely by both stimulus and task. We presented sequences of achromatic radial frequency pattern targets (200ms, ISI randomized from 1800-2000ms) with occasional small ‘probe’ changes in their contrast, shape and orientation. Probe types were randomized and independent and subjects were cued to attend to specific probe types in blocks of 24s. Responses from 15 subjects (9 F) were recorded in separate fMRI and MEG experiments. Support vector machines were used to decode MEG sensor space data at 5ms intervals and fMRI voxel-wise responses from retinotopically-defined regions of interest. We show that both attentional state and target events cause changes in ongoing neuronal activity and that we are able to distinguish between different types of low-level featural attention with good temporal and spatial resolution. Some of his most cited vision research and neuroimaging papers