Bio

Academic Appointments


Administrative Appointments


  • Scientific Advisory Board, Max Planck Institute for Biological Cybernetics (2009 - Present)
  • McKnight Scholars Awards Selection Committee, McKnight Endowment Fund for Neuroscience (2007 - Present)
  • Scientific Advisory Board, Riken Brain Sciences Institute, Tokyo (2003 - Present)
  • Correspondent, Committee on Human Rights, National Academy of Sciences (2001 - Present)

Honors & Awards


  • Champalimaud Vision Award, Champalimaud Foundation, Lisbon (2010)
  • Karl Spencer Lashley Award, American Philosophical Society (2010)
  • Dan David Prize, Dan David Foundation and Tel Aviv University (2004)
  • Award for Outstanding Service to Graduate Students, Students, Stanford University School of Medicine (2003)
  • Distinguished Scientific Contribution Award, American Psychological Association (2002)
  • Elected to membership, National Academy of Sciences, USA (2000)
  • Investigator, Howard Hughes Medical Institute (1997)
  • Guggenheim Fellowship, Guggenheim Foundation (1995)
  • Fogarty International Senior Research Fellowship, Fogarty International Center, NIH (1995)
  • W. Alden Spencer Award for highly original contributions to research in neurobiology, Columbia University (1994)
  • MERIT Award, National Eye Institute (1993)
  • The Rank Prize in Optoelectronics, The Rank Prize Funds, London (1992)
  • Golden Brain Award, Minerva Foundation (1992)
  • Henry J. Kaiser Award for Excellence in Teaching, Students of the Stanford University School of Medicine (1991, 1997)

Professional Education


  • Ph.D., California Inst. of Technology, Neurobiology (1980)

Research & Scholarship

Current Research and Scholarly Interests


The long-term goal of our research is to understand the neuronal processes that mediate visual perception and visually guided behavior. To this end we are conducting parallel behavioral and physiological experiments in animals that are trained to perform selected perceptual or eye movement tasks. By recording the activity of cortical neurons during performance of such tasks, we gain initial insights into the relationship of neuronal activity to the animal's behavioral capacities. Hypotheses concerning this relationship are tested by modifying neural activity within local cortical circuits to determine whether behavior is effected in a predictable manner. Computer modelling techniques are then used to develop more refined hypotheses concerning the relationship of brain to behavior that are both rigorous and testable. This combination of behavioral, electrophysiological and computational techniques provides a realistic basis for neurophysiological investigation of cognitive functions such as perception, memory and motor planning.

Teaching

2013-14 Courses


Graduate and Fellowship Programs


Publications

Journal Articles


  • Dissociation of Neuronal and Psychophysical Responses to Local and Global Motion CURRENT BIOLOGY Hedges, J. H., Gartshteyn, Y., Kohn, A., Rust, N. C., Shadlen, M. N., Newsome, W. T., Movshon, J. A. 2011; 21 (23): 2023-2028

    Abstract

    Most neurons in cortical area MT (V5) are strongly direction selective, and their activity is closely associated with the perception of visual motion. These neurons have large receptive fields built by combining inputs with smaller receptive fields that respond to local motion. Humans integrate motion over large areas and can perceive what has been referred to as global motion. The large size and direction selectivity of MT receptive fields suggests that MT neurons may represent global motion. We have explored this possibility by measuring responses to a stimulus in which the directions of simultaneously presented local and global motion are independently controlled. Surprisingly, MT responses depended only on the local motion and were unaffected by the global motion. Yet, under similar conditions, human observers perceive global motion and are impaired in discriminating local motion. Although local motion perception might depend on MT signals, global motion perception depends on mechanisms qualitatively different from those in MT. Motion perception therefore does not depend on a single cortical area but reflects the action and interaction of multiple brain systems.

    View details for DOI 10.1016/j.cub.2011.10.049

    View details for Web of Science ID 000298028100031

    View details for PubMedID 22153156

  • Integration of Sensory and Reward Information during Perceptual Decision-Making in Lateral Intraparietal Cortex (LIP) of the Macaque Monkey PLOS ONE Rorie, A. E., Gao, J., McClelland, J. L., Newsome, W. T. 2010; 5 (2)

    Abstract

    Single neurons in cortical area LIP are known to carry information relevant to both sensory and value-based decisions that are reported by eye movements. It is not known, however, how sensory and value information are combined in LIP when individual decisions must be based on a combination of these variables. To investigate this issue, we conducted behavioral and electrophysiological experiments in rhesus monkeys during performance of a two-alternative, forced-choice discrimination of motion direction (sensory component). Monkeys reported each decision by making an eye movement to one of two visual targets associated with the two possible directions of motion. We introduced choice biases to the monkeys' decision process (value component) by randomly interleaving balanced reward conditions (equal reward value for the two choices) with unbalanced conditions (one alternative worth twice as much as the other). The monkeys' behavior, as well as that of most LIP neurons, reflected the influence of all relevant variables: the strength of the sensory information, the value of the target in the neuron's response field, and the value of the target outside the response field. Overall, detailed analysis and computer simulation reveal that our data are consistent with a two-stage drift diffusion model proposed by Diederich and Bussmeyer for the effect of payoffs in the context of sensory discrimination tasks. Initial processing of payoff information strongly influences the starting point for the accumulation of sensory evidence, while exerting little if any effect on the rate of accumulation of sensory evidence.

    View details for DOI 10.1371/journal.pone.0009308

    View details for Web of Science ID 000274923700012

    View details for PubMedID 20174574

  • Estimates of the Contribution of Single Neurons to Perception Depend on Timescale and Noise Correlation JOURNAL OF NEUROSCIENCE Cohen, M. R., Newsome, W. T. 2009; 29 (20): 6635-6648

    Abstract

    The sensitivity of a population of neurons, and therefore the amount of sensory information available to an animal, is limited by the sensitivity of single neurons in the population and by noise correlation between neurons. For decades, therefore, neurophysiologists have devised increasingly clever and rigorous ways to measure these critical variables (Parker and Newsome, 1998). Previous studies examining the relationship between the responses of single middle temporal (MT) neurons and direction-discrimination performance uncovered an apparent paradox. Sensitivity measurements from single neurons suggested that small numbers of neurons may account for a monkey's psychophysical performance (Britten et al., 1992), but trial-to-trial variability in activity of single MT neurons are only weakly correlated with the monkey's behavior, suggesting that the monkey's decision must be based on the responses of many neurons (Britten et al., 1996). We suggest that the resolution to this paradox lies (1) in the long stimulus duration used in the original studies, which led to an overestimate of neural sensitivity relative to psychophysical sensitivity, and (2) mistaken assumptions (because no data were available) about the level of noise correlation in MT columns with opposite preferred directions. We therefore made new physiological and psychophysical measurements in a reaction time version of the direction-discrimination task that matches neural measurements to the actual decision time of the animals. These new data, considered together with our recent data on noise correlation in MT (Cohen and Newsome, 2008), provide a substantially improved account of psychometric performance in the direction-discrimination task.

    View details for DOI 10.1523/JNEUROSCI.5179-08.2009

    View details for Web of Science ID 000266252300026

    View details for PubMedID 19458234

  • Can Monkeys Choose Optimally When Faced with Noisy Stimuli and Unequal Rewards? PLOS COMPUTATIONAL BIOLOGY Feng, S., Holmes, P., Rorie, A., Newsome, W. T. 2009; 5 (2)

    Abstract

    We review the leaky competing accumulator model for two-alternative forced-choice decisions with cued responses, and propose extensions to account for the influence of unequal rewards. Assuming that stimulus information is integrated until the cue to respond arrives and that firing rates of stimulus-selective neurons remain well within physiological bounds, the model reduces to an Ornstein-Uhlenbeck (OU) process that yields explicit expressions for the psychometric function that describes accuracy. From these we compute strategies that optimize the rewards expected over blocks of trials administered with mixed difficulty and reward contingencies. The psychometric function is characterized by two parameters: its midpoint slope, which quantifies a subject's ability to extract signal from noise, and its shift, which measures the bias applied to account for unequal rewards. We fit these to data from two monkeys performing the moving dots task with mixed coherences and reward schedules. We find that their behaviors averaged over multiple sessions are close to optimal, with shifts erring in the direction of smaller penalties. We propose two methods for biasing the OU process to produce such shifts.

    View details for DOI 10.1371/journal.pcbi.1000284

    View details for Web of Science ID 000263924500009

    View details for PubMedID 19214201

  • Context-Dependent Changes in Functional Circuitry in Visual Area MT NEURON Cohen, M. R., Newsome, W. T. 2008; 60 (1): 162-173

    Abstract

    Animals can flexibly change their behavior in response to a particular sensory stimulus; the mapping between sensory and motor representations in the brain must therefore be flexible as well. Changes in the correlated firing of pairs of neurons may provide a metric of changes in functional circuitry during behavior. We studied dynamic changes in functional circuitry by analyzing the noise correlations of simultaneously recorded MT neurons in two behavioral contexts: one that promotes cooperative interactions between the two neurons and another that promotes competitive interactions. We found that identical visual stimuli give rise to differences in noise correlation in the two contexts, suggesting that MT neurons receive inputs of central origin whose strength changes with the task structure. The data are consistent with a mixed feature-based attentional strategy model in which the animal sometimes alternates attention between opposite directions of motion and sometimes attends to the two directions simultaneously.

    View details for DOI 10.1016/j.neuron.2008.08.007

    View details for Web of Science ID 000260237300016

    View details for PubMedID 18940596

  • The temporal precision of reward prediction in dopamine neurons. Nature neuroscience Fiorillo, C. D., Newsome, W. T., Schultz, W. 2008

    Abstract

    Midbrain dopamine neurons are activated when reward is greater than predicted, and this error signal could teach target neurons both the value of reward and when it will occur. We used the dopamine error signal to measure how the expectation of reward was distributed over time. Animals were trained with fixed-duration intervals of 1-16 s between conditioned stimulus onset and reward. In contrast to the weak responses that have been observed after short intervals (1-2 s), activations to reward increased steeply and linearly with the logarithm of the interval. Results with varied stimulus-reward intervals suggest that the neural expectation was substantial after just half an interval had elapsed. Thus, the neural expectation of reward in these experiments was not highly precise and the precision declined sharply with interval duration. The neural precision of expectation appeared to be at least qualitatively similar to the precision of anticipatory licking behavior.

    View details for PubMedID 18660807

  • Local field potential in cortical area MT: Stimulus tuning and behavioral correlations JOURNAL OF NEUROSCIENCE Liu, J., Newsome, W. T. 2006; 26 (30): 7779-7790

    Abstract

    Low-frequency electrical signals like those that compose the local field potential (LFP) can be detected at substantial distances from their point of origin within the brain. It is thus unclear how useful the LFP might be for assessing local function, for example, on the spatial scale of cortical columns. We addressed this problem by comparing speed and direction tuning of LFPs obtained from middle temporal area MT with the tuning of multiunit (MU) activity recorded simultaneously. We found that the LFP can be well tuned for speed and direction and is highly correlated with that of MU activity, particularly for frequencies at and above the gamma band. LFP tuning is substantially poorer for lower frequencies, although tuning for direction extends to lower frequencies than does tuning for speed. Our data suggest that LFP signals at and above the gamma band reflect neural processing on the spatial scale of cortical columns, within a few hundred micrometers of the electrode tip. Consistent with this notion, we also found that frequencies at and above the gamma band measured during a speed discrimination task exhibit an effect known as "choice probability," which reveals a particularly close relationship between neural activity and behavioral choices. In the LFP, this signature of the perceptual choice comprises a shift in relative power from low-frequency bands (alpha and beta) to the gamma band. It remains to be determined how LFP choice probability, which is a temporal signature, is related to conventional choice probability effects observed in spike rates.

    View details for DOI 10.1523/JNEUROSCI.5052-05.2006

    View details for Web of Science ID 000239361200003

    View details for PubMedID 16870724

  • Choosing the greater of two goods: Neural currencies for valuation and decision making NATURE REVIEWS NEUROSCIENCE Sugrue, L. P., Corrado, G. S., Newsome, W. T. 2005; 6 (5): 363-375

    Abstract

    To make adaptive decisions, animals must evaluate the costs and benefits of available options. The nascent field of neuroeconomics has set itself the ambitious goal of understanding the brain mechanisms that are responsible for these evaluative processes. A series of recent neurophysiological studies in monkeys has begun to address this challenge using novel methods to manipulate and measure an animal's internal valuation of competing alternatives. By emphasizing the behavioural mechanisms and neural signals that mediate decision making under conditions of uncertainty, these studies might lay the foundation for an emerging neurobiology of choice behaviour.

    View details for DOI 10.1038/nrn1666

    View details for Web of Science ID 000228863100011

    View details for PubMedID 15832198

  • Choosing the greater of two goods: neural currencies for valuation and decision making Nature Reviews Neuroscience LP Sugrue, GS Corrado, WT Newsome 2005; 6: 363-375
  • Linear-Nonlinear-Poisson models of primate choice dynamics Journal of the Experimental Analysis of Behavior GS Corrado, LP Sugrue, WT Newsome 2005; 84: 581-617
  • Perceptual "read-out" of conjoined direction and disparity maps in extrastriate area MT PLOS Biology DeAngelis, G., WT Newsome 2004; 2: 394-404
  • Matching behavior and the encoding of value in parietal cortex Science Sugrue, L., GS Corrado, WT Newsome 2004; 304: 1782-1787
  • Neural basis of a perceptual decision in the parietal cortex (area LIP) of the rhesus monkey JOURNAL OF NEUROPHYSIOLOGY Shadlen, M. N., Newsome, W. T. 2001; 86 (4): 1916-1936

    Abstract

    We recorded the activity of single neurons in the posterior parietal cortex (area LIP) of two rhesus monkeys while they discriminated the direction of motion in random-dot visual stimuli. The visual task was similar to a motion discrimination task that has been used in previous investigations of motion-sensitive regions of the extrastriate cortex. The monkeys were trained to decide whether the direction of motion was toward one of two choice targets that appeared on either side of the random-dot stimulus. At the end of the trial, the monkeys reported their direction judgment by making an eye movement to the appropriate target. We studied neurons in LIP that exhibited spatially selective persistent activity during delayed saccadic eye movement tasks. These neurons are thought to carry high-level signals appropriate for identifying salient visual targets and for guiding saccadic eye movements. We arranged the motion discrimination task so that one of the choice targets was in the LIP neuron's response field (RF) while the other target was positioned well away from the RF. During motion viewing, neurons in LIP altered their firing rate in a manner that predicted the saccadic eye movement that the monkey would make at the end of the trial. The activity thus predicted the monkey's judgment of motion direction. This predictive activity began early in the motion-viewing period and became increasingly reliable as the monkey viewed the random-dot motion. The neural activity predicted the monkey's direction judgment on both easy and difficult trials (strong and weak motion), whether or not the judgment was correct. In addition, the timing and magnitude of the response was affected by the strength of the motion signal in the stimulus. When the direction of motion was toward the RF, stronger motion led to larger neural responses earlier in the motion-viewing period. When motion was away from the RF, stronger motion led to greater suppression of ongoing activity. Thus the activity of single neurons in area LIP reflects both the direction of an impending gaze shift and the quality of the sensory information that instructs such a response. The time course of the neural response suggests that LIP accumulates sensory signals relevant to the selection of a target for an eye movement.

    View details for Web of Science ID 000171562000035

    View details for PubMedID 11600651

  • Separate signals for target selection and movement specification in the superior colliculus SCIENCE Horwitz, G. D., Newsome, W. T. 1999; 284 (5417): 1158-1161

    Abstract

    At any given instant, multiple potential targets for saccades are present in the visual world, implying that a "selection process" within the brain determines the target of the next eye movement. Some superior colliculus (SC) neurons begin discharging seconds before saccade initiation, suggesting involvement in target selection or, alternatively, in postselectional saccade preparation. SC neurons were recorded in monkeys who selected saccade targets on the basis of motion direction in a visual display. Some neurons carried a direction-selective visual signal, consistent with a role in target selection in this task, whereas other SC neurons appeared to be more involved in postselection specification of saccade parameters.

    View details for Web of Science ID 000080359100034

    View details for PubMedID 10325224

  • Cortical area MT and the perception of stereoscopic depth NATURE DeAngelis, G. C., Cumming, B. G., Newsome, W. T. 1998; 394 (6694): 677-680

    Abstract

    Stereopsis is the perception of depth based on small positional differences between images formed on the two retinae (known as binocular disparity). Neurons that respond selectively to binocular disparity were first described three decades ago, and have since been observed in many visual areas of the primate brain, including V1, V2, V3, MT and MST. Although disparity-selective neurons are thought to form the neural substrate for stereopsis, the mere existence of disparity-selective neurons does not guarantee that they contribute to stereoscopic depth perception. Some disparity-selective neurons may play other roles, such as guiding vergence eye movements. Thus, the roles of different visual areas in stereopsis remain poorly defined. Here we show that visual area MT is important in stereoscopic vision: electrical stimulation of clusters of disparity-selective MT neurons can bias perceptual judgements of depth, and the bias is predictable from the disparity preference of neurons at the stimulation site. These results show that behaviourally relevant signals concerning stereoscopic depth are present in MT.

    View details for Web of Science ID 000075384200043

    View details for PubMedID 9716130

  • On neural codes and perception J. Cogn. Neurosci. Newsome, W. 1995; 7: 95-100

Conference Proceedings


  • Motion perception: Seeing and deciding Shadlen, M. N., Newsome, W. T. NATL ACAD SCIENCES. 1996: 628-633

    Abstract

    The primate visual system offers unprecedented opportunities for investigating the neural basis of cognition. Even the simplest visual discrimination task requires processing of sensory signals, formation of a decision, and orchestration of a motor response. With our extensive knowledge of the primate visual and oculomotor systems as a base, it is now possible to investigate the neural basis of simple visual decisions that link sensation to action. Here we describe an initial study of neural responses in the lateral intraparietal area (LIP) of the cerebral cortex while alert monkeys discriminated the direction of motion in a visual display. A subset of LIP neurons carried high-level signals that may comprise a neural correlate of the decision process in our task. These signals are neither sensory nor motor in the strictest sense; rather they appear to reflect integration of sensory signals toward a decision appropriate for guiding movement. If this ultimately proves to be the case, several fascinating issues in cognitive neuroscience will be brought under rigorous physiological scrutiny.

    View details for Web of Science ID A1996TR32600017

    View details for PubMedID 8570606

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