Progress on the CBMM challenge questions: What/Who is there?

Abstract:

We continue the series of weekly discussions and reports on each CBMM challenge question describing progress and problems of ongoing work at CBMM.

Thrust 2 is focused on the Neural Circuits and on how models for the CBMM challenge should be consistent with the brain neural data. One of the projects in the thrust focuses on the neural correlates of visual attention, which plays a key role in the answer to most of the CBMM open set of questions, probably in the form of task-dependent visual routines. I will describe very recent results about the neural correlates of so-called object attention. The voluntary control of visual attention to behaviorally relevant stimuli is thought to involve “top-down” feedback to visual processing areas. For spatially-directed attention, one key source of top-down attention is the frontal eye fields (FEF). My lab found that feedback to visual cortex from FEF causes enhanced responses to stimuli at attended locations, and leads to synchronized neural activity in the gamma frequency range between FEF and visual processing areas. Recent evidence suggests that the pulvinar may also serve as an important relay of attentional feedback to visual cortex, and it may also serve to desynchronize cortical activity in the alpha frequency range. Many aspects of the neural response changes with attention are explained by top-down inputs to a simple cortical circuit containing excitatory and inhibitory neurons. The neural basis of feature, or object attention has been much more difficult to understand.

One possibility is that attention to objects with particular features causes spatially directed attention to be directed to those objects, utilizing known pathways for spatial attention. Another possibility is that attention to objects or features such as faces, colors, or shapes, depends on feedback to visual cells that are selective for those features, biasing activity in favor of those stimuli. Such a mechanism would be similar to what is thought to mediate visual recall memory. We have recently found evidence for both types of mechanisms in prefrontal cortex of humans and monkeys.