The Miller Lab @ MIT

  • Load Dependence of β and γ Oscillations Predicts Individual Capacity of Visual Attention

    Miller Lab

    Rouhinen et al provide evidence for the role of neural oscillations in the limitations of cognitive capacity.  Subjects tracked multiple objects.  Strength of oscillations were different preceding detected vs undetected objects.  Suppression of low-frequency oscillations (<20 Hz) and strengthening of high-frequency oscillations (>20 Hz) in the frontoparietal cortex was correlated with attentional load.   Load-dependent strengthening of 20-90 Hz oscillations was predictive of individual capacity.  This supports hypotheses that oscillations play major role in attention and are responsible for the limited bandwidth of cognition.

    Further reading on attention, capacity, and oscillations:

    • Buschman,T.J. and Miller, E.K. (2010) Shifting the Spotlight of Attention: Evidence for Discrete Computations in Cognition. Frontiers in Human Neuroscience. 4(194): 1-9. 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 »
    • 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. 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 »
    • Siegel, M., Warden, M.R., and Miller, E.K. (2009) Phase-dependent neuronal coding of objects in short-term memory. Proceedings of the National Academy of Sciences, 106: 21341-21346. View PDF »

  • Attentional Modulation of Cell-Class-Specific Gamma-Band Synchronization

    Miller Lab

    Visual attention increases synchrony of neural activity in visual cortex.  Fries and colleagues showed that synchronization differs for putative excitatory (broad-spiking) and inhibitory (narrow-spiking) neurons.  The inhibitory neurons synchronize in the gamma band twice as strongly as excitatory neurons but the excitatory neurons synchronize to an earlier phase than inhibitory neurons.  Further, attention increases gamma synchrony for the most active neurons but decreases synchrony for the least active neurons.  These results show that attention-related neural synchrony is not uniform but instead an orchestration between different neuron types showing different types of synchrony.  This lends further support for the role of neural synchrony in attention.

  • Frequency-specific mechanism links human brain networks for spatial attention

    Miller Lab

    Corbetta and colleagues studied attention by recording from patients undergoing surgery for epilepsy.  They found evidence for frequency-based attention mechanisms, in particular phase modulation at lower frequencies.  Different types of attentional operations (holding vs shifting attention) were associated with synchrony at different frequencies.

  • Evidence for a fixed capacity limit in attending multiple locations

    Miller Lab

    Everybody agrees that we can only hold a few things in mind simultaneously.  However, there is disagreement about why.  One theory is that limited cognitive resources are flexible and spread among the items held in mind; the more items, the “thinner” the information about each.  Another theory is more of a fixed limit model: Resources are allocated in a discrete fashion and there is a fixed number of items that can be held in mind.  Ester et al provide evidence for the latter, fixed, model.  Subjects monitored a number of locations and then asked details about one of the locations.  The subject’s performance and neural data was best described by a fixed limit model.

  • Task-Relevant and Accessory Items in Working Memory Have Opposite Effects on Activity in Extrastriate Cortex

    Miller Lab

    Peters et al used functional imaging in humans to examine the effects of the contents of working memory on extrastriate visual cortex.  Subjects performed a visual search task.  The target item in working memory enhanced processing of a matching visual input whereas other “accessory” items held in working memory suppressed extrastriate activity.  These dual effects may help focus on relevant tasks while avoiding distractions.

  • Evidence for differential top-down and bottom-up suppression in posterior parietal cortex

    Miller Lab

    Mirpour and Bisley recorded neural responses and local field potentials from the lateral intraparietal cortex (LIP) during visual search.  Previously fixated non-target stimuli elicited greater lower frequency (alpha and beta) oscillations.  This suggested that reduced neural responses (and attention) to previously seen stimuli results from oscillatory-based top-down influences from the frontal cortex.

  • Dynamic Construction of a Coherent Attentional State in a Prefrontal Cell Population

    Miller Lab

    John Duncan and colleagues examined dynamic allocation of attention in the prefrontal cortex.  A behaviorally relevant target and non-target were simultaneously presented in both visual hemifields.  At first, activity in each hemifield was dominated by the stimulus in the contralateral field but then all activity became dominated by the target alone.  The speed and degree of attentional reallocation depend on relative attentional weights; more experience with a target led to faster and greater allocation to the target.  Because neurons rapidly shifted their representation from an irrelevant to relevant stimulus in the opposite hemifield, these results are consistent with adaptive coding models of neural representation.
    Kadohisa et al (2013) Dynamic Construction of a Coherent Attentional State in a Prefrontal Cell Population

    Further reading on adaptive coding:
    Miller, E.K. and Cohen, J.D. (2001) An integrative theory of prefrontal cortex function. Annual Review of Neuroscience, 24:167-202.  View PDF »

    Duncan, J. and Miller, E.K. (2013) Adaptive neural coding in frontal and parietal cortex. In: Stuss, D.T. and Knight, R.T. (Eds). Principles of Frontal Lobe Function: Second Edition.

    Rigotti, M., Barak, O., Warden, M.R., Wang, X., Daw, N.D., Miller, E.K., & Fusi, S. “The importance of mixed selectivity in complex cognitive tasks”. Nature, 497, 585-590, 2013 doi:10.1038/nature12160. View PDF

  • Video game training enhances cognitive control in older adults

    Miller Lab
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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

    The Atlantic: How To Rebuild An Attention Span

  • Top-Down Beta Rhythms Support Selective Attention via Interlaminar Interaction: A Model

    Miller Lab

    Lee, Whittington, and Kopell review recent studies of the role of beta-band oscillations in top-down control of attention and model it.  In their model, top-down beta rhythms activate layer-specific ascending projections that mediate biased competition.  Interneurons resonate with the beta oscillations and help modulate superficial layer activity according to attentional demands.

  • Gamma-band synchronization and information transmission

    Miller Lab

    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.