Dynamics of coherent activity between cortical areas defines a two-stage process of top-down attention

Analysing a visual scene requires the brain to briefly keep in memory potentially relevant items of that scene and then direct attention to their locations for detailed processing. To reveal the neuronal basis of the underlying working memory and top-down attention processes, we trained macaques to match two patterns presented with a delay between them. As the above processes are likely to require communication between brain regions, and the parietal cortex is known to be involved in spatial attention, we simultaneously recorded neuronal activities from the interconnected parietal and middle temporal areas. We found that mnemonic information about features of the first pattern was retained in coherent oscillating activity between the two areas in high-frequency bands, followed by coherent activity in lower frequency bands mediating top-down attention on the relevant spatial location. Oscillations maintaining featural information also modulated activity of the cells of the parietal cortex that mediate attention. This could potentially enable transfer of information to organize top-down signals necessary for selective attention. Our results provide evidence in support of a two-stage model of visual attention where the first stage involves creating a saliency map representing a visual scene and at the second stage attentional feedback is provided to cortical areas involved in detailed analysis of the attended parts of a scene.