An article in MIT’s Technology Review magazine about our work on how multitasking “mixed selectivity” neurons may be key for cognition.
Do-It-All Neurons – A key to cognitive flexibility by Anne Trafton
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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 » -
Koralek et al show learning-related increases in oscillatory coherence between the motor cortex and striatum during learning. The increase in coherence was seen for neurons related to behavior. This supports the notion that oscillatory coherence plays a role in forming functional networks.
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Pesenson, Cohen, and Voytek review methods for linking nonlinear oscillatory neural dynamics, in particular oscillatory phase, to behavior.
Linking Nonlinear Neural Dynamics to Single-Trial Human Behavior -
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.
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Dipoppa and Gutkin propose a model of working memory in which gamma-beta oscillations gates access, theta oscillations protects working memory from distractions, and alpha oscillations clears out old memories.
This is consistent with our observations that beta helps from ensembles for rules held in working memory while alpha clears out a dominant ensemble so that a weaker one can be used:
Buschman, T.J., Denovellis, E.L., Diogo, C., Bullock, D. and Miller, E.K. (2012) Synchronous oscillatory neural ensembles for rules in the prefrontal cortex. Neuron, 76: 838-846. View PDF -
Peter Lakatos and Charlie Schroeder have conducted elegant work showing that the brain entrains its rhythms to attended sensory inputs. Here, Lakatos et al show that normal human subjects show increased rhythmic entrainment with increasing task demands, By contrast, schizophrenic patients are less able to match their brain rhythms to attended stimuli, even when the task is highly demanding.
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 »
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Ekstrom and Watrous review the role of low frequency oscillatory coupling in cognition. The propose that different resonant frequencies within the same networks support movement vs memory related functions. They provide further evidence and argument for a role for oscillatory coupling in multiplexing of function. In other words, different frequency coupling can allow the same networks to have different roles by allowing them to communicate different messages to different targets.
Miller Lab work on oscillatory coupling and multiplexing:
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 View PDF »Miller, E.K. and Buschman, T.J. (2013) Cortical circuits for the control of attention. Current Opinion in Neurobiology. 23:216–222 View PDF »
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Kometer et al show that psilocybin decreased spontaneous alpha oscillations which precluded the usual decrease in alpha when a visual stimulus is presented. Psilocybin may result in a brain state in which normal stimulus-driven cortical excitation is overwhelmed by spontaneous neuronal excitation resulting in altered perception and hallucinations.
We recently found evidence that alpha oscillations are useful for clearing out unwanted thoughts (neural ensembles) that could interfere with the current cognitive demands:
- Buschman, T.J., Denovellis, E.L., Diogo, C., Bullock, D. and Miller, E.K. (2012) Synchronous oscillatory neural ensembles for rules in the prefrontal cortex. Neuron, 76: 838-846. View PDF