The Miller Lab @ MIT

  • New review: Goal-direction and top-down control

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    Goal-direction and top-down control
    Timothy J. Buschman and Earl K. Miller

    We 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.

    Read it here

  • Beyond the Connectome: The Dynome

    Miller Lab

    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.

  • Functional Specialization in the Human Brain Estimated By Intrinsic Hemispheric Interaction

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    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 »

  • Synchronized brain waves enable rapid learning

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    Antzoulatos EG and Miller EK  (in press) Increases in Functional Connectivity between Prefrontal Cortex and Striatum during Category Learning. Neuron, in press.
    DOI: http://dx.doi.org/10.1016/j.neuron.2014.05.005

    Animals were trained to learn new category groupings by trial and error.  Once they started to “get” the categories, there was an increase in beta-band synchrony between the prefrontal cortex and striatum, two brain areas critical for learning.  By the time the categories were well-learned, the beta synchrony between the areas became category-specific, that is, unique sets of sites in the prefrontal cortex and striatum showed increased beta synchrony for the two different categories.  This suggests that synchronization of brain rhythms can quickly establish new functional brain circuits and thus support cognitive flexibility, a hallmark of intelligence.

    MIT Press release:
    Synchronized brain waves enable rapid learning
    MIT study finds neurons that hum together encode new information.

  • Neuronal Correlates of Visual Working Memory in the Corvid Endbrain

    Miller Lab
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    A well-known correlate of working memory is sustained neural activity that bridges short gaps in time.  It is well-established in the primate brain, but what about birds?  They have working memory.  (In fact, there is a lot of classic work that detailed the behavioral characteristics of working memory in pigeons).

    Miller Lab alumnus Andreas Nieder and crew trained crows to perform a working memory task and found sustained activity in the nidopallium caudolaterale (NCL).  This is presumably a neural correlate of the crow’s visual working memory.

    Now if crows could only pass that causality test.

  • Induced Alpha Rhythms Track the Content and Quality of Visual Working Memory Representations with High Temporal Precision

    Miller Lab

    Anderson et al used scalp EEG recordings to decode the content of working memory and its quality.  Subjects performed a orientation working memory task.  Anderson et al found that the spatial distribution of alpha band power could be used to determine what orientation the subject was remembering and how precisely they were remembering it.  Cool.

  • Different Neuronal Computations of Working Memory Across Visual Hemifields

    Miller Lab

    Matsushima and Tanaka compared neural correlates of spatial working memory for locations within the same hemifield or across hemifields.  When the two remembered locations were in the same hemifield (right or left side of vision), the neural response in the prefrontal cortex was intermediate to the two cues presented alone.  When the cues were across hemifields, the neural response was the same as the preferred cue presented alone.  In other words, remembered locations within a hemifield seemed to be in competition with each other whereas locations across the hemifields seemed to be have no interaction at all.  In yet other words, it was as if the (intact) monkeys had their brains split down the middle. The authors concluded local inhibitory interactions between cues within, but not across, hemifields.

    This confirms Buschman et al (2011) who found that independent capacities for visual working memory in the right and left hemifields.

    Further reading:
    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 »

  • Functions of gamma-band synchronization in cognition

    Miller Lab

    Gamma band oscillations are seen throughout the cortex and subcortex.  Do they have a single or different functions?  Bosman et al review the literature and conclude the latter but nonetheless point out that gamma likely rises from a cortical motif involving interactions between excitatory and inhibitory neurons. So, just as activity of individual neurons means different things in different brain areas so does gamma rhythms.

  • Executive control processes underlying multi-item working memory

    Miller Lab

    Does the prefrontal cortex (PFC) maintain the contents of working memory or does it direct the focus of attention?  Lara and Wallis asked this question by training monkeys to perform a multi-color change detection task.  Few PFC neurons encoded the color of the stimuli. Instead, the dominant signals were the spatial location of the item and the location of focal attention. This suggests that the PFC is more involved in directing attention than retaining information in working memory.  Supporting this was increased power in alpha and theta power in the PFC, frequency bands associated with long-range neural communication.

  • Different Neuronal Computations of Spatial Working Memory for Multiple Locations within versus across Visual Hemifields

    Miller Lab

    Matsushima and Tanaka examined the neural correlates of spatial working memory for one vs two locations.  When the two locations were in the same (right or left) hemifield, the level neural activity was intermediate between that elicited from either cue alone.  By contrast, when the cues were presented in opposite hemifields, neural activity to each cue was as if the cue was presented alone.  This lends support to other observations (e.g., Buschman et al 2011) that there are independent capacities for working memory in the right and left visual hemifields, as if the brain was split down the middle.

    Further reading:
    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 »