This review examines evidence for a neurobiological explanation of executive functions of working memory.  We suggest that executive control stems from information about task rules acquired by mixed selective, adaptive coding, multifunction neurons in the prefrontal cortex.  Their output dynamically links the cortical-wide networks needed to complete the task.  The linking may occur via synchronizing of neural rhythms, which may explain why we have a limited capacity for simultaneous thought.

Roy et al show that the activity of neurons in the prefrontal cortex (pFC) are linked to categorical decisions.  Monkeys were trained to categorize a set of computer-generated images as “cats” vs “dogs”.  Then, they were shown ambiguous images were centered on a category boundary, that is, they were a mix of 50% of cats and dogs and therefore had no category information.  The monkeys guessed at their category membership.  Activity to the same ambiguous image differed significantly, depending on the monkey’s decision about the image’s category.  Thus, pFC activity reflects categorical decisions.

Earl Miller is quoted on NBCnews.com.  In brief: Don’t multitask and if you do don’t drive.
NBCnews.com: The ‘smart life’: How connected cars, clothes and homes could fry your brain

Miller Lab alumnus David Freedman has been awarded tenure at the University of Chicago.  Congrats, Dave!  We’re happy, proud, and not surprised.

Our work with Stefano Fusi’s Lab makes  The Wall Street Journal.

Miller Lab alumnus Jon Wallis and crew studied two different types of cost-benefit decisions (delay vs effort).  They found that different neurons in the dorsolateral prefrontal cortex, orbitofrontal, and anterior cingulate encoded the different types of decisions.  Thus, rather than have neurons encode decisions on an abstract level, frontal cortex neurons encode stimuli based on their exact consequences.

Blogger John Borghi lists the most highly cited papers in neuroscience and has kind words for Miller and Cohen (2001).  Thanks, John!

  • Miller, E.K. and Cohen, J.D. (2001) An integrative theory of prefrontal cortex function. Annual Review of Neuroscience, 24:167-202.
    Designated a Current Classic by Thomson Scientific as among the most cited papers in Neuroscience and Behavior. View PDF »

Bob Desimone (Director of the McGovern Institute for Brain Research at MIT) demonstrates auto-synchronization of metronomes

There was a segment titled “There’s No More Single Tasking”

Watch it here (archived):
http://live.huffingtonpost.com/r/segment/the-lost-ability-to-do-one-task-at-a-time/525fff6b78c90a6d7e00020f

Miller Lab alumnus Melissa Warden wins NYSCF Robertson Neuroscience Award. Melissa is now a professor at Cornell.  Congrats, Melissa!

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

Miller Lab alumnus Andreas Nieder shows that dopamine (DA) has different effects on two different classes of neurons in the prefrontal cortex.  For neurons with a short latency visual response, DA suppressed activity but preserved their signal to noise ratio.  For neurons with a longer visual latency (exclusively broad-spiking, putative pyramidal neurons), DA increased excitability and enhanced signal/noise ratio.  Thus, DA can shape how the prefrontal cortex processes bottom-up sensory inputs.
Jacob et al

A Neuron Preview for Miller Lab graduate student Simon Kornblith’s paper on a network for scene processing:
Scene Areas in Humans and Macaques by Epstein and Julian

Here’s the original post on Simon’s paper and a link to it:
A Network For Scene Processing

Slideshow: The 6th Annual Dana and Betty Fisher Retreat of MIT’s Picower Institute for Learning and Memory
http://www.youtube.com/watch?v=mu-0CW5Nyl4&feature=share

Miller Lab graduate student Simon Kornblith publishes a paper in Neuron from work in his old lab.  By combining FMRI with electrode recording and stimulation, they found an area in the occipitotemporal cortex that has many scene-selective neurons, the lateral place patch (LPP).  By stimulating it, they discover connections to several other cortical areas, including a medial place patch (MPP) in the parahippocampal gyrus.  Elegant and important work, Simon, congratulations!  Now, get back to work. 🙂

Miller Lab alumnus, Andreas Nieder, finds that abstract decisions divorced from motor plans are distributed across frontal areas, even those traditionally thought of as motor areas.  In fact, they are more strongly encoded in the presupplementary motor area than the prefrontal cortex.
Merten and Nieder 2013

Miller Lab work cited:
Freedman, D.J., Riesenhuber, M., Poggio, T., and Miller, E.K. (2001) Categorical representation of visual stimuli in the primate prefrontal cortex. Science, 291:312-316. View PDF »

Miller, E.K. and Cohen, J.D. (2001) An integrative theory of prefrontal cortex function. Annual Review of Neuroscience, 24:167-202.  Designated a Current Classic by Thomson Scientific as among the most cited papers in Neuroscience and Behavior. View PDF »

Miller, E.K. (2000) The prefrontal cortex and cognitive control. Nature Reviews Neuroscience, 1:59-65.

Wallis, J.D., Anderson, K.C., and Miller, E.K. (2001) Single neurons in the prefrontal cortex encode abstract rules. Nature, 411:953-956. View PDF »

It was a good week for Miller Lab alumnus David J. Freedman (now a professor at University of Chicago).

Dave won the Distinguished Investigator Award in the Biological Sciences at The University of Chicago (http://www.freedmanlab.org/), was elected to the International Neuropsychological Symposium (INS History), and his band FuzZz had a CD release party.

When you’re hot, you’re hot.

 

Miller Lab alumnus, Andreas Nieder, shows number tuned neurons in pefrontal and parietal cortices of naive (untrained) subjects.
Viswanathan and Nieder 2013 

Andreas Nieder’s Miller Lab work on the neural substrates for numerosity:

Nieder, A., Freedman, D.J., and Miller, E.K. (2002) Representation of the quantity of visual items in the primate prefrontal cortex.  Science. 297:1708-1711. View PDF »

Nieder, A. and Miller, E.K. (2003) Coding of cognitive magnitude: Compressed scaling of numerical information in the primate prefrontal cortex. Neuron. 37:149-157. View PDF »

Nieder, A. and Miller, E.K. (2004) A parieto-frontal network for visual numerical information in the monkey. Proceedings of the National Academy of Sciences, 101:7457-7462. View PDF »

Nieder, A. and Miller, E.K. (2004) Analog numerical representations in rhesus monkeys: Evidence for parallel processing. Journal of Cognitive Neuroscience. 16:889-901. View PDF »

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)

For years, neurophysiologists have observed that many neurons in higher-level cortex have “weird” properties.  They activate across a wide range of seemingly unrelated conditions and thus don’t  seem to fit into the traditional view of brain function in which each neuron has a single function or message.  They were often considered a “complicating nuisance” at best or dismissed at worst.  It turns out that these mixed selectivity neurons may be the most critical for complex behavior and cognition.   They greatly expand the brain’s computational power.

Read MIT press release: Complex brain function depends on flexibility

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

This study shows oscillatory synchrony between different frontal lobe areas  during preparatory focusing of attention.  Interestingly, the same neurons participated in attention and motor networks, only at different frequencies.  This is further evidence that rhythmic synchrony may allow neurons to multiplex their functions.
Totah et al Cerebral Cortex 2013

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 »

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 »

Miller, E.K. and Cohen, J.D. (2001) An integrative theory of prefrontal cortex function. Annual Review of Neuroscience, 24:167-202.  Designated a Current Classic by Thomson Scientific as among the most cited papers in Neuroscience and Behavior. View PDF »

Rainer, G., Rao, S.C., and Miller, E.K. (1999)  Prospective coding for objects in the primate prefrontal cortex.  Journal of Neuroscience, 19:5493-5505. View PDF »

 

The human prefrontal cortex may not be special in terms of its size relative to other primates, but it is still a pretty special.
http://blogs.scientificamerican.com/beautiful-minds/2013/05/16/gorillas-agree-human-frontal-cortex-is-nothing-special/?utm_source=feedly

Want to know what it does?  Here’s a start:
Miller, E.K. and Cohen, J.D. (2001) An integrative theory of prefrontal cortex function. Annual Review of Neuroscience, 24:167-202.  Designated a Current Classic by Thomson Scientific as among the most cited papers in Neuroscience and Behavior. View PDF »

This paper reports FMRI in humans performing a task requiring first-order rules (S-R associations with a specific motor output) and second order rules that govern the use of the first-order rules.  Cerebellum lobules that project to the prefrontal cortex show activation for both types of rules.  This suggests that the cerebellum contributes to rule-based behaviors even when the rules are higher-order and don’t directly involve a motor command.
http://cercor.oxfordjournals.org/content/23/6/1433.abstract

For further reading on the role of rules in cognition and their neural implementation see:
Miller, E.K. and Cohen, J.D. (2001) An integrative theory of prefrontal cortex function. Annual Review of Neuroscience, 24:167-202.  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

Wallis, J.D., Anderson, K.C., and Miller, E.K. (2001) Single neurons in the prefrontal cortex encode abstract rules. Nature, 411:953-956. View PDF »

Miller Lab Research Scientist Vicky Puig quoted in a article in El Pais.  The Picower Institute at MIT is called  “one of the best neuroscience centers in the world”.  One of the?

In Spanish, but that’s why we have Google Translate.
http://elpais.com/elpais/2013/05/01/eps/1367419412_106866.html

A nice article in the Wall Street Journal describing Jack Gallant’s recent FMRI work.  They didn’t just  subtract conditions and come up with a typical imaging map with one or a few isolated bits of activation.  Jack L. Gallant, Tolga Çukur and colleagues used sophisticated  analyses to find the relationship between the patterns of whole brain activity and the content of videos watched by the subjects.  This revealed wide networks, not isolated patches, of neurons engaged by attention to different things in the video (humans vs vehicles, etc).

It also showed how dynamic and flexible the brain is.  When subjects looked for humans, large portions of the cortex were sensitive to humans and less sensitive to vehicles. When subjects looked for vehicles, large portions of the cortex became vehicle detectors.  Many of the same brain areas were involved in multiple networks, changing when people changed the focus of their attention.  Thus, rather than the cortex being composed of modules with strict specializations, high-level information is spread across wide-ranging cortical networks of neurons that participate in many different functions, adapting their properties to current cognitive demands.

We have long argued that mixed selectivity, adaptive coding neurons are crucial for hallmarks of cognition like flexibility.  And in forthcoming paper (Rigotti et al), we show computationally that you can’t build a complex brain w/o them.

For a brief discussion of this issue, read this Preview of a paper by Stokes et al:
Miller, E.K. and Fusi, S. (2013) Limber neurons for a nimble mind. Neuron. 78:211-213. View PDF

And stay tuned for this paper:
Rigotti, M., Barak, O., Warden, M.R., Wang, X., Daw, N.D., Miller, E.K., & Fusi, S. (in press) The importance of mixed selectivity in complex cognitive tasks. Nature.