Ph.D., Massachusetts Institute of Technology
947 E 58th St., Abbott 310
Chicago, Illinois 60637
David Freedman, Ph.D.
- Computational & Theoretical
- Systems / Behavior / Cognitive
We have a remarkable ability to learn from our experiences. Through experience, we learn to interpret the meaning of the sights and sounds around us and to behave in ways that move us closer to achieving our goals. This capacity to learn from and adapt to our ever changing environment is a foundation of complex behavior, as it allows us to make sense of incoming sensory stimuli and to plan successful behavioral responses. While much is known about the neural processing of simple visual features such as color, orientation and direction of motion, less is known about how the brain learns, stores, recognizes and recalls the behavioral significance, or meaning, of our sensory experiences.
Our goal is to understand how visual feature encoding in sensory brain areas is transformed into more abstract and experience-dependent representations that reflect the behavioral significance of stimuli. We use advanced neurophysiological techniques to monitor neuronal activity in multiple brain areas during visual learning, memory and recognition tasks. Visual categorization tasks have been useful tools for investigating how visual representations are transformed through learning. Previously, we compared neuronal activity in frontal, temporal and parietal lobes during visual categorization, and found that parietal and frontal lobe neurons reflected the learned category membership of visual stimuli. This contrasted sharply with activity in brain areas considered to be more involved in sensory processing (such as the middle temporal and inferior temporal cortices) which seemed more involved in visual feature encoding and did not reflect more abstract information about stimuli. Understanding how feature-based encoding in visual cortex is transformed into more abstract and meaningful representations in subsequent neuronal processing stages is a central goal of our research.
Rishel C.A., Huang G., and Freedman D.J. Independent Category and Spatial Encoding in Parietal Cortex. Neuron, in press.
Fitzgerald J.K., Freedman D.J., Fanini A., Bennur S., Gold J.I., and Assad J.A. Biased Associative Representations in Parietal Cortex. Neuron, 77: 180-191, 2013.
Swaminathan S.K. and Freedman D.J. Preferential Encoding of Visual Categories in Parietal Cortex Compared with Prefrontal Cortex. Nature Neuroscience, 15: 315-320, 2012.
Fitzgerald J.K, Freedman D.J., and Assad J.A. Generalized Associative Representations in Parietal Cortex. Nature Neuroscience, 14: 1075-1079, 2011.
Freedman D.J. and Assad J.A. A Proposed Common Neural Mechanisms for Categorization and Perceptual Decisions. Nature Neuroscience, 14:143-146, 2011.
Freedman D.J. and Assad J.A. Distinct Encoding of Spatial and Non-Spatial Factors in Parietal Cortex. Journal of Neuroscience, 29: 5671-5680, 2009.
Meyers E.M., Freedman D.J., Krieman G., Poggio T., and Miller E.K. Using Neuron Population Readout to Decode the Temporal Dynamics of Category Information. Journal of Neurophysiology 100: 1407-1419, 2008.
Freedman D.J. Neuronal Mechanisms of Visual Categorization and Category Learning. In: The Neuroscience of Rule-Guided Behavior. Wallis J.D. and Bunge S. (eds.). Oxford University Press, pp 391-418, 2007.
Freedman D.J. and Assad J.A. Experience-Dependent Representation of Visual Categories in Parietal Cortex. Nature 443: 85-88, 2006.
Freedman D.J., Riesenhuber M., Poggio T., and Miller E.K. Experience-Dependent Sharpening of Visual Shape Selectivity in Inferior Temporal Cortex. Cerebral Cortex, 16: 1631-1644, 2006.
Miller E.K., Nieder A., Freedman D.J., and Wallis J.D. Neural Correlates of Categories and Concepts. Current Opinion in Neurobiology, 13:2:198-203, 2003.
Freedman D.J., Riesenhuber M., Poggio T., and Miller E.K. A Comparison of Primate Prefrontal and Inferior Temporal Cortices During Visual Categorization. Journal of Neuroscience 23: 5235-5246, 2003.
Nieder A., Freedman D.J., and Miller E.K. Representation of the Quantity of Visual Items in the Primate Prefrontal Cortex. Science 297: 1708-1711, 2002.
Freedman D.J., Riesenhuber M., Poggio T., and Miller E.K. Visual Categorization and the Primate Prefrontal Cortex: Neurophysiology and Behavior. Journal of Neurophysiology 88: 914-928, 2002.
Freedman D.J., Riesenhuber M., Poggio T., Miller E.K. Categorical Representation of Visual Stimuli in the Primate Prefrontal Cortex. Science 291: 312-316, 2001.