DiQuattro et al use dynamic causal modeling (DCM) of FMRI signals to show that the frontal eye fields (FEF) are more involved initiating shifts of attention than the temporoparietal junction (TPJ, another leading candidate). The FEF received sensory signals earlier than the TPJ and FEF to TPJ connectivity was modulated by appearance of a target.
Miller Lab work cited:
Buschman, T.J. and Miller, E.K. (2007) Top-down versus bottom-up control of attention in the prefrontal and posterior parietal cortices. Science. 315: 1860-1862 The Scientist’s “Hot Paper” for October 2009. View PDF »
Buschman, T.J. and Miller, E.K. (2009) Serial, covert, shifts of attention during visual search are reflected by the frontal eye fields and correlated with population oscillations. Neuron, 63: 386-396. View PDF »
A nice article in the Wall Street Journal describing Jack Gallant’s recent FMRI work. They didn’t just subtract conditions and come up with a typical imaging map with one or a few isolated bits of activation. Jack L. Gallant, Tolga Çukur and colleagues used sophisticated analyses to find the relationship between the patterns of whole brain activity and the content of videos watched by the subjects. This revealed wide networks, not isolated patches, of neurons engaged by attention to different things in the video (humans vs vehicles, etc).
It also showed how dynamic and flexible the brain is. When subjects looked for humans, large portions of the cortex were sensitive to humans and less sensitive to vehicles. When subjects looked for vehicles, large portions of the cortex became vehicle detectors. Many of the same brain areas were involved in multiple networks, changing when people changed the focus of their attention. Thus, rather than the cortex being composed of modules with strict specializations, high-level information is spread across wide-ranging cortical networks of neurons that participate in many different functions, adapting their properties to current cognitive demands.
We have long argued that mixed selectivity, adaptive coding neurons are crucial for hallmarks of cognition like flexibility. And in forthcoming paper (Rigotti et al), we show computationally that you can’t build a complex brain w/o them.
For a brief discussion of this issue, read this Preview of a paper by Stokes et al:
Miller, E.K. and Fusi, S. (2013) Limber neurons for a nimble mind. Neuron. 78:211-213. View PDF
And stay tuned for this paper:
Rigotti, M., Barak, O., Warden, M.R., Wang, X., Daw, N.D., Miller, E.K., & Fusi, S. (in press) The importance of mixed selectivity in complex cognitive tasks. Nature.