They got my experiment wrong, but spelled my name right:
Biology of Consciousness: Bridging the Mind-Body Gap?
The Huffington Post 10/30/14
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Ruff and Cohen report evidence that attention can increase or decrease neural correlations depending on whether the neurons have the same or different functions.
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Goal-direction and top-down control
Timothy J. Buschman and Earl K. MillerWe review the neural mechanisms that support top-down control of behavior. We suggest that goal-directed behavior utilizes two systems that work in concert. A basal ganglia-centered system quickly learns simple, fixed goal-directed behaviors while a prefrontal cortex-centered system gradually learns more complex (abstract or long-term) goal-directed behaviors. Interactions between these two systems allows top-down control mechanisms to learn how to direct behavior towards a goal but also how to guide behavior when faced with a novel situation.
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Hwang et al report increased alpha/beta power in the frontal cortex during a fundamental test of cognitive control, the anti-saccade task. There was increased cross-frequency coupling between alpha and beta bands and alpha, specifically, was predictive of trial-by-trial success. This adds to the growing body of evidence that beta oscillations are associated with cognition and that alpha is important for inhibitory control.
For further reading:
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 »
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 »
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Dotson et al report both 0 and 180 deg phase synchrony between the prefrontal and parietal cortices during a working memory task, suggestion both formation and segregation of different functional networks by neural synchrony.
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Womeldorf et al observed bursts of firing in the anterior cingulate and prefrontal cortex during shifts of attention. These bursts (but not non-burst firing) synchronized over long distances (between the AC and PFC) to local field field potentials at beta and gamma frequencies. These bursts were proceeded by bursts of inhibitory neurons. The authors propose burst firing mechanisms help form functional networks to coordinate shifts of attention.
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Kopell et al provide an excellent review of the role of neural rhythms in brain function and argue that we need to know more than anatomy, no matter how detailed. We also need to connect it to an understanding of brain dynamics. They review our current knowledge of brain rhythms and identify (many) open questions.
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Our lab and others (e.g., Buschman and Miller, 2007; Bastos et al 2012) has suggested that top-down (feedback) vs bottom-up (feedforward) cortical processing is mediated by synchrony between cortical areas at different frequencies: lower (e.g., beta band) for top-down vs higher (e.g., gamma band) for bottom-up. These two different frequency bands allow top-down vs bottom-signals to multiplex through the same circuits, much as different FM radio stations multiplex through the airwaves. They may also allow cortical microcircuits to engage in helpful things like predictive coding (Bastos et al., 2012).
Schmiedt et al (2014) provide new evidence for this. They recorded neural activity in visual area V4 after damage to primary visual area V1. V4 is higher in the cortical hierarchy, so V1 has a bottom-up influence on V4. They found that damage to V1 decreased the gamma in V4 that follows appearance of a visual stimulus. That is consistent with gamma carrying bottom-up or feedforward signals, lost after V1 damage. By contrast, V4 beta activity was minimally affected, reflecting the unaffected top-down influence on V4 Normally there is beta suppression during visual stimulation, presumably because the bottom-up inputs overwhelm or suppress beta-mediated top-down processing. After V1 damage, this suppression of top-down beta rhythms was diminished, presumably because it was no longer suppressed by bottom-up influences from V1.
For further reading:
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 »Bastos AM, Usrey WM, Adams RA, Mangun GR, Fries P, Friston KJ. Canonical microcircuits for predictive coding. Neuron. 2012 Nov 21;76(4):695-711. doi:
10.1016/j.neuron.2012.10.038. Review. -
At this risk of kvelling, in 2011 we published a paper (Buschman et al., 2011) showing independent visual working memory capacities in the right vs left visual hemifields. We were told “no way” and “that’s impossible”. Since then, a bunch of papers have supported this. Here’s another one.
Wang et al used FMRI and found that brain networks primarily interact with ipsilateral, not contralateral networks. Thus, the brain emphasizes processing within each hemisphere (visual hemifield) and minimizes across-hemisphere processing.
Also see:
Buschman,T.J., Siegel, M., Roy, J.E. and Miller, E.K. (2011) Neural substrates of cognitive capacity limitations. Proceedings of the National Academy of Sciences. 108(27):11252-5. View PDF » -
Ibos and Freedman show that area LIP is more than just space and spatial attention. They trained monkeys to make decisions based on conjunctions of motion and color. LIP neurons integrated color and motion when it was task-relevant.