Van der Linden et al used computer generated images to study categorization in the human brain. They found that the frontal cortex showed sensitivity to the features diagnostic for the categories, which is consistent with results from animal studies at the neuron level.
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Psychedelic drugs desynchronize oscillatory rhythms in the cortex. Like, wow.
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Jack Gallant and crew used FMRI to examine scene processing in the human brain. They found that scenes activated many regions of anterior visual cortex and that the scene categories capture the co-occurrence of the objects that compose the scenes.
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Adam Gazzaley and company show, for the first time, that training on a video game results in benefits that transfer to other tests of cognition. Training on the NeuroRacer game produced long-lasting improvements in cognitive abilities of older adults (age 65-80). How did they do it? Their trick was to focus on multitasking and attention.
Anguera et al (2013) Nature -
Matt Chafee and colleagues used multiple-electrode recording in the prefrontal and parietal cortices to examine the temporal dynamics of their neural activity during a categorization task. They decoded category signals from patterns of simultaneously recorded in small bins and asked whether the resulting information time series in one area could predict the other. This showed that “executive” top-down signals flow from the prefrontal to parietal cortex.
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Max Riesenhuber and colleagues used EEG to examine the time course of shape and category signals in the human brain. Neural adaptation for category changes was seen in frontal cortex and then subsequently in temporal cortex. This supports the hypothesis that shape categories are formed by shape signals from temporal cortex that converge and form explicit category representations in frontal cortex. A late category signal in temporal cortex is consistent with category signals feeding back from frontal to temporal cortex.
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Markov et al provide an excellent review and analysis of the anatomy of visual cortex and beyond. The show that supragranular layers contain highly segregated feedforward and feedback pathways. Their analysis of the detailed anatomy revealed that feedback connections are more numerous and have more levels than feedforward connections. By contrast, infragranular layers are less hierarchical and may be more involved in point-to-point cross-talk than feedforward or feedback processing. Markov et al map the feedforward and feedback pathways to recent observations that feedforward vs feedback communication is supported by gamma vs beta cortical oscillations.
For more on the role of oscillations in feedforward and feedback cortical communication, see our review:
Miller, E.K. and Buschman, T.J. (2013) Cortical circuits for the control of attention. Current Opinion in Neurobiology. 23:216–222 View PDF » -
Miller Lab alumnus Andreas Nieder shows that dopamine (DA) has different effects on two different classes of neurons in the prefrontal cortex. For neurons with a short latency visual response, DA suppressed activity but preserved their signal to noise ratio. For neurons with a longer visual latency (exclusively broad-spiking, putative pyramidal neurons), DA increased excitability and enhanced signal/noise ratio. Thus, DA can shape how the prefrontal cortex processes bottom-up sensory inputs.
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A review of the groundbreaking work of Patricia Goldman-Rakic by Amy Arnsten
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Vinck, Womelsdorf, Fries review the role of gamma band synchronization in information transfer in the cortex. They argue that due to feedforward coincidence detection and phase-coupling, gamma synchronization is important for flexible routing of information and may be an important determinant of spike rate coding.