Department of Brain and Cognitive Sciences
The human brain is the most complex, sophisticated, and powerful information-processing device known. To study mechanisms of the brain and mind, the Department of Brain and Cognitive Sciences at the combines the experimental technologies of neuroscience and psychology with the theoretical power of computational methods and cognitive science. The department's research focuses on several themes, with each studied at multiple levels of analysis using cellular, systems, computational and cognitive approaches.
Brain Mechanisms of Vision
Bart Anderson's lab has made significant theoretical advances toward understanding the mechanisms underlying depth and surface. They have demonstrated that motion sensitive mechanisms play a critical role in solving the binocular matching problem and also discovered the critical image properties that human observers use to compute the opacity and lightness of partially transparent and translucent surfaces. They are using these discoveries to develop a quantitative theory of this perceptual ability.
Nancy Kanwisher's lab has employed a new event-related fMRI adaptation paradigm to characterize visual representations in a variety of different cortical areas, and have used this technique to demonstrate a cortical area that represents perceived shape. Second, they have discovered a new category-selective cortical region that responds to the appearance of the human body. They also collected both behavioral and fMRI data that argue against the long-held assumption that image segmentation is distinct from, necessary for, and prior to object recognition.
Peter Schiller's lab examines the neural control of visually guided eye movements and the neural mechanisms of depth perception. They have reported several significant new findings about the manner in which the occipital, parietal and frontal cortices contribute to eye-movement control in the primate. They characterized six cortical areas that play a central role in directing the eyes to selected visual targets.
Gerald Schneider's research group has developed methods for obtaining an unprecedented amount of axon regeneration in the visual pathway of the adult brain, with return of visual function in animals that had been blind after brain injury.
To study the limits of human visual recognition processes, Pawan Sinha's laboratory established data that benchmarks performance of human observers on several ecologically important recognition tasks. They constructed both a scheme for encoding impoverished image structure and a computational framework. To then determine if these limits serve as quantitative markers for diagnosing visual disorders, they developed and clinically tested an experimental paradigm as a tool for diagnosing subtle forms of visual agnosia and for evaluating changes in perception caused by abnormal developmental histories.
Learning and Memory
Research in Emilo Bizzi's laboratory has been aimed at describing plasticity in the motor cortex and in assessing the feasibility of a remotely supervised, computer-enabled physical therapy device, administered over high-speed telecommunications for patients recovering from stroke.
Suzanne Corkin's laboratory strives to elucidate the cognitive and neural organization of human memory systems. In patients with Alzheimer's disease (AD) or Parkinson's disease, their results indicate that the respective neuropathological changes exert dissociable effects on working memory capacities. In healthy volunteers, aging disturbs the frontal lobe contribution to semantic processing (semantic encoding and categorization easily verbalized material), whereas AD also disturbs the temporal lobe contribution (perceptual encoding and analysis; representation of long-term semantic knowledge).
Ann Graybiel's lab has carried out ensemble recording from multiple neurons in the neocortex and basal ganglia of rodents and monkeys. In the rodents, they found large-scale changes in neural activity in the striatum as animals learn in procedural learning tasks. They also found that these changes in neural activity are reversed when the animals are then placed in situations in which performing the procedure is no longer rewarded. However, when reward is again instated, the neural activity changes begin to return to the cortical-basal ganglia network. A similar result was found in monkeys. These studies demonstrate a remarkably tight brain-behavior relationship during the course of learning.
Earl Miller's lab studied the ability to group stimuli into meaningful categories. They trained monkeys to categorize computer-generated stimuli as "cats" and "dogs." They found neural correlates of these categories in the lateral prefrontal cortex, a brain region associated with the highest levels of cognitive function. The ability to abstract principles or rules from experience allows behavior to extend beyond specific circumstances that have been directly experienced. The most prevalent neuronal activity observed in the prefrontal cortex reflected the coding of the abstract 'match' and 'nonmatch' rules.
Tomaso Poggio's lab studies the problem of learning, as the gateway to the problem of intelligence both in brains and machines, focusing on three main directions: theory; engineering applications; and neuroscience. Their engineering applications include bioinformatics (diagnostic of human cancers from gene expression data), information extraction from text and the web, financial markets, trainable man-machines interfaces and computer vision for object detection. In the neurosciences, they have described a theory of visual cortex underlying object recognition and object categorization.
Molly Potter's lab has studied: short-term memory for naturalistic pictures, showing that the immediate representation is of gist, not just visual features; competition for attention between two near-simultaneous written words, showing intense competition over SOAs of at least 500 ms; and interaction between pictured objects and words in rapidly presented sequences.
Sebastian Seung's lab developed a new theory of hybrid analog-digital computation in the brain and about how the brains circuitry calculates in a manner that is a hybrid of analog and digital. They are developing this further in an application for object recognition.
Through fMRI, Anthony Wagner's lab examines how human memory is organized and supported by the mind and brain by exploring the cognitive control of memory. Recent advances include demonstration that frontal lobe short-term memory processes contribute to long-term memory formation; characterization of frontal lobe processes that guide semantic memory retrieval; and specification of the neural computations that accompany the unique state of memory failure known as the tip-of-the-tongue phenomenon. They recently initiated efforts to examine how age-related changes in frontal lobe circuits contribute to memory decline in the elderly.
By studying the interactions between brain areas using simultaneous neural recording techniques, Matthew Wilson's lab is pursuing the flow of mnemonic information during awake and sleep states between brain areas involved in memory formation and areas involved in higher-level cognition and decision making. They have recently found direct evidence of dreaming in rodents by identifying the reactivation during REM sleep of memory patterns established during recent awake experience-the first demonstration of a neural correlate of dreaming.
Brain Development and Plasticity
Guosong Liu's lab studied the functional maturation of glutamatergic synapses, a critical process during the formation of functional neural networks. In contrast to the prevailing hypothesis that silent synapses lack functional AMPA receptors, they found that these synapses contain functional AMPA receptors, but cannot release transmitters from presynaptic terminals properly. These results suggest new directions for identifying the locus of synaptic plasticity.
Elly Nedivi's lab has developed a highly sensitive subtractive cloning and differential screening method that has allowed them to identify and isolate a large pool of genes involved in neuronal plasticity. These 377 candidate plasticity-related genes (cpgs) constitute the basis of their studies. One of the cpgs that is currently under full scale investigation in the lab is cpg2. They found that cpg2 is a structural protein and because of its similarity to members of the spectrin/dystrophin protein family, it is possible that it also functions to regulate attachment or localization of synaptic components to the membrane and/or cytoskeleton.
Amnesiac is a fly mutant that William Quinn's lab isolated many years ago because the mutation shortens memory. The amnesiac gene encodes one or more peptide neurotransmitters. This year, they found that the peptides are concentrated in two cells in the fly (Drosophila) brain, and that neurotransmission from these two cells is necessary and sufficient for normal memory in the fly.
Mriganka Sur's laboratory demonstrated several basic mechanisms of plasticity in the developing and adult brain. In developing animals, his laboratory showed that mice lacking genes for ephrins A2 and A5 exhibit pronounced plasticity of retinal projections directed to the auditory thalamus. The ephrins act as barriers that normally prevent such plasticity. In adult animals, his lab showed that visual cortex neurons exhibit much greater plasticity of orientation tuning at pinwheel centers rather than at orientation domains. Visual cortex in alert monkeys also exhibited orientation plasticity based on features of stimuli, and such plasticity would serve to enhance the discrimination of orientations during natural viewing of scenes.
Richard Wurtman has been using weight loss treatment strategies based on discoveries in his lab involving the ability of certain dietary carbohydrates to increase brain serotonin, thereby both decreasing the appetite and diminishing depressive symptoms. He is also studying the ability of this program to block the massive weight gain observed in many patients taking drugs for schizophrenia, bipolar depression, and epilepsy.
Language and Number Systems of the Brain
Edward Gibson's lab has shown that that connecting two words in a sentence is affected by the complexity of the inferences that are needed in the intervening material; and also discovered that intonational boundaries (e.g., pauses) are more likely to be placed at points of long integrations, and before complex constituents.
Steven Pinker has begun using fMRI to study the differences between regular and irregular inflection, and their implications for the interaction between memory and computation in language.
Elizabeth Spelke has been on sabbatical in the lab of Stanislas Dehaene in France doing behavioral and neuroimaging studies of representations of number in human adults and infants.
Kenneth Wexler's lab continued researching language development. They have shown that the important early linguistic stage that Wexler discovered covered a wide variety of other processes, including word order problems in Korean negation. They also continued developing an innovative new standard test for detecting children with Specific Language Impairment.
Matthew Wilson was granted tenure, Nancy Kanwisher was promoted to full Professor, Guosong Liu was promoted to Associate Professor without tenure, and Earl Miller was appointed Associate Director of the Center for Learning and Memory. In addition, Morgan Sheng joined the faculty as the Menicon Professor of Neuroscience; Yasunori Hayashi is a new Assistant Professor in the Riken/MIT Neuroscience Research Center, and Lera Boroditsky is a newly hired Assistant Professor of Cognitive Science. The weekly colloquium series, begun last year, has enjoyed enormous success, as have the two Hans-Lukas Memorial lectures, the Margaret Roche Donlan Bidwell lecture and the social event at the annual Society for Neuroscience Meeting.
Twenty graduate students entered in fall 2000, one with an NDSEG Fellowship, one with an NSF Fellowship, one with a Lee Kuan Yew Fellowship (Singapore), one with an NSERC Fellowship (Canada). Three of the new incoming students were funded by Rosenblith Fellowships (supported by a generous grant from Walter A. Rosenblith), and the rest were supported by department NIH training grants or other funds.
During this year, two students graduated with a Master of Science degree, and five graduated with the Ph.D. All five of the latter assumed postdoctoral positions in universities or research institutions (Department of Brain and Cognitive Sciences at MIT, Visual Sciences Laboratory of the Psychology Department at Harvard, Neuroscience Statistics Research Laboratory at MGH and in the Division of Applied Science and Engineering at Harvard).
The department had a total of 97 undergraduates this year, with 29 graduating seniors. A record number of 43 freshmen joined the department as new majors at the end of the 2001 spring term.
The newly revised undergraduate curriculum, described in last year's President's Report, was approved by the Committee on Curricula and will be implemented in AY2002. This will provide a streamlined approach to the major, making it simpler for students to complete the requirements while gaining a broad knowledge of the brain and cognitive sciences.
Emilio Bizzi was invited to serve on the Board of Scientific Directors, Institute for Scientific Information in Turin, Italy. He was also invited to serve on the International Scientific Valuation Committee of the International Institute for Advanced Studies (SISSA) in Trieste, Italy.
Ann Graybiel received the Outstanding Women in Neuroscience Award from Brown University.
Yasunori Hayashi received an Ellison Medical Foundation New Scholar in Aging award.
Earl Miller received the Young Investigator Award, Society for Neuroscience, 2000.
Elizabeth Spelke received the Ipsen Prize in Neuronal Plasticity, 2001 (shared with A. Galaburda and J. Morton) and America's Best in Science and Medicine, Time Magazine (one of 20 selected - issue to appear in early August).
Anthony Wagner received the McKnight Scholar Award, 2001-2003, and the Paul E. Newton Career Development Professorship in Neuroscience, 2000-2003.
Mriganka Sur received the Sigma Xi Distinguished Lecturer, 2001-2003.
More information about the Department of Brain and Cognitive Sciences can be found online at http://web-bcs.mit.edu/.