The Miller Lab

  • Today @ #CRC2013: Charlie Schroeder’s neurodynamics

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    Charlie Schroeder shows us the laminar profile of oscillations in cortex.  Different strengths for different frequency bands in different cortical layers.  Attention phase-synchronizes oscillations across layers facilitating communication between them. See Lakatos et al (2005) J. Neurophys.

    Circuits from different thalamic nuclei  to cortex, one broad and modulatory, the other narrow and specific, may regulate oscillatory entrainment.

    New Neuron paper shows cortical entrainment that matches periodic sensory inputs; phase depended on the attended frequency content., enhancing attended representations.  Lakatos et al 2013

    Entrainment may explain cocktail party effect. Low frequency phase and high gamma power track attended speech.  Zion Golumbic et al

  • People can ‘beat’ guilt detection tests by suppressing incriminating memories

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    Zara Bergstrom, Jon Simons and crew show that people can beat EEG tests of guilt detection by suppressing the guilty memories.  Research calls into question reliability of such tests.
    http://www.cam.ac.uk/research/news/people-can-beat-guilt-detection-tests-by-suppressing-incriminating-memories

  • ‘@ MIT tomorrow: Rhythmic Dynamics and Cognition

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    If you are interested in cognition, brain rhythms, and, especially, brain rhythms and cognition, this is the place to be.
    http://cogrhythms.bu.edu/conference.htm

    The Rhythmic Dynamics and Cognition Conference is a two-day event sponsored by the Cognitive Rhythms Collaborative (CRC). The program will be held at the Brain Building (Building 46) on the MIT campus (Room 3002) and will include lectures, a reception, and a poster session.

    Speakers include:

    • Pascal Fries, (Ernst Strungmann Institute (ESI), Frankfurt)
    • Elizabeth Buffalo (Emery University)
    • Charlie Schroeder (Nathan Kline Institute)
    • Peter Brown (University College London)
    • Fiona Le Beau (Newcastle University)
    • Earl Miller (MIT)
    • Charlie Wilson (University of Texas, San Antonio)
    • Peter Uhlhaas (University of Glasgow)
    • Christa van Dort (Mass. General Hospital)
    • Markus Siegal (University of Tubingen)
    • Robert Knight (UC Berkely)

  • Sober discussion: Does brain stim really improve math?

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    It was recently reported that low-voltage, non-invasive brain stimulation improves mathematical abilities.  Does it?  Here’s a cautionary discussion:
    Does Brain Stimulation Make You Better at Maths?

  • Attention-induced changes in temporal dynamics of neural activity depends on NMDA receptors

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    Visual attention modulates several aspects of neural coding.  There is an increase in firing rate and changes in temporal dynamics: a reduction of neural variance and noise correlation as well as changes in oscillatory synchronization.   The authors used glutamatergic receptor activation, combined with neurophysiological recording to show that the NMDA receptor is responsible for attention -related changes in neural temporal dynamics but not for  increases in firing rate.  Thus,  different  neurophysiological mechanisms that underlie attention can be dissociated at the receptor level. This supports the hypothesis that attention is mediated in part by the temporal dynamics of neural activity, not merely changes in the firing rate of neurons, and that the changes temporal dynamics are not simply a byproduct of changes in firing rate.
    Herrero et al (2013) Neuron

    For a further discussion of the role of temporal dynamics in attention see:
    Miller, E.K. and Buschman, T.J. (2013) Cortical circuits for the control of attention.  Current Opinion in Neurobiology.  23:216–222  View PDF »

    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 »

    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 »

  • The time course of brain synchronization patterns during cognitive tasks

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    This paper uses EEG to examine the timecourse of synchronization patterns across the brain during a simple cognitive task.  First, there was low frequency (delta) synchrony, which may reflect global, long-range synchronization and may help organize the higher frequency synchrony that followed.  Then, there was higher frequency (gamma) synchrony, which may reflect reorganization of local circuits for bottom-up processing of sensory inputs.  Finally, there was beta synchrony, which may reflect the final stage of top-down processing in the task.  Gamma and beta synchronization has been shown to be correlated with bottom-up vs top-down cortical processing (Buschman and Miller, 2007; Chanes et al, 2013; Ibos et al, 2013).  This study identifies and confirms some of the proposed mechanisms of global information integration in the brain.
    Brazdil et al (2013)

    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 »

    Chanes et al (2013)  Journal of Neuroscience

    Ibos et al (2013) Journal of Neuroscience

  • NY TIMES: GRAY MATTER Vision Is All About Change

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    In this week’s NY Times, Susana Martinez-Conde reminds us that our visual system works by detecting change.
    http://www.nytimes.com/2013/05/19/opinion/sunday/vision-is-all-about-change.html

  • Robust Gamma Coherence between Macaque V1 and V2 by Dynamic Frequency Matching

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    Rhythmic synchrony between neurons has been suggested as a mechanism for establishing communication channels between neurons.  However, this hypothesis has been criticized because of observations that the exact frequency of gamma oscillations bounces around too much to provide a stable communication channel.  (BTW, it doesn’t seem to bother anyone that single neuron activity also bounces around).

    In this study, Roberts et al record from V1 and V2 simultaneously while presenting gratings of varying contrast.  Even though the gamma frequencies changed with stimulus contrast and fluctuated over time, coherence remained stable between V1 and V2.   Thus, rhythmic synchrony can provide a stable channel for neural communication.
    http://www.cell.com/neuron/abstract/S0896-6273(13)00227-4?utm_source=feedly

    For further reading on the role of rhythmic synchrony in neural communication see:
    Miller, E.K. and Buschman, T.J. (2013) Cortical circuits for the control of attention.  Current Opinion in Neurobiology.  23:216–222  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

  • A Functional Hierarchy within the Parietofrontal Network in Stimulus Selection and Attention Control

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    Ibos et al examined the relative roles of the frontal eye fields (FEF) and lateral intraparietal area (LIP) in bottom-up vs top-down selection.  They found that intrinsic salience (bottom-up) was signaled in LIP before the FEF whereas extrinsic salience (top-down) was signaled in FEF before LIP.  The authors conclude that bottom-up vs top-down control of attention predominates in the parietal vs frontal cortex, respectively.
    http://www.jneurosci.org/content/33/19/8359.abstract

    As noted by the authors, this is highly consistent with our lab’s observations that attention signals for bottom-up capture by stimulus salience (pop-out) vs top-down search originate from parietal vs frontal cortex, respectively.
    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 »

    We also showed that rhythmicity of frontal cortical top-down signals may control the periodic shifts of attention during visual search that leads to eventual selection of a target:
    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 »

  • Neural Limits to Representing Objects Still within View

    Miller Lab

    Our very limited ability to hold multiple thoughts in mind is apparent to anyone who has tried to talk on the phone and email at the same time.  Traditionally, this is thought of as a limitation in the capacity of working memory, the “mental scratchpad” used to keep important information “online” after it is no longer available.  However, Ed Vogel and crew show that the bottleneck is not in working memory per se but instead present during processing of visual stimuli while they are still visible.  Thus, the bottleneck is not (just) in memory but also in the processing of sensory inputs.  In other words, capacity limitations seem to be a fundamental limit in neural processing related to consciousness in general, not a unique byproduct of working memory.
    http://www.jneurosci.org/content/33/19/8257.abstract

    As noted by the authors, this is consistent with our finding that when capacity is exceeded, information is lost in a bottom-up fashion during initial processing of visual stimuli:
    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 »