Fitzpatrick Lab

We study the Functional Architecture and Development of the Cerebral Cortex

David Fitzpatrick

Chief Executive Officer,
Scientific Director

(561) 972-9000
info@maxplanckflorida.org
www.fitzpatricklab.org

Bio

Dr. Fitzpatrick was named Chief Executive Officer and Scientific Director of the Max Planck Florida Institute on January 3, 2011. Prior to his arrival in Jupiter, Fitzpatrick was the James B. Duke Professor of Neurobiology at the Duke University School of Medicine, Durham, NC, and Director of the Duke Institute for Brain Sciences. His scientific contributions have earned him international recognition as a leader in systems neuroscience, with a focus on the functional organization and development of neural circuits in the cerebral cortex — the largest and most complex area of the brain, whose functions include sensory perception, motor control, and cognition.

Fitzpatrick’s research has played a pivotal role in defining the functional organization of cortical circuits, exploring rules of intracortical connectivity, addressing mechanisms of neural coding, and probing the role of experience in the maturation of cortical circuits. His current research utilizes state-of-the-art in vivo imaging techniques to probe the functional synaptic architecture of circuits in primary visual cortex, defining the circuit mechanisms that build the selective response properties of cortical neurons and the critical role that neural activity plays in the proper maturation of these circuits.

Education

  • PhD, Duke University, Psychology/Neuroscience (1982)
  • BS, Pennsylvania State University, Biology (1974)

Research Topic

Our research focuses on the functional organization and development of neural circuits in the cerebral cortex, the largest and most complex area of the brain, comprising 20 billion neurons and 60 trillion synapses–a neuronal network whose proper function is critical for sensory perception, motor control, and cognition.

State of the art anatomical, electrophysiological, and imaging techniques are used to study neural circuits in primary visual cortex, an area where the emergence of novel response properties raises a host of tractable questions about the neural basis of visual perception. More broadly, the study of circuits in visual cortex provides a window into fundamental mechanisms of cortical processing that underlie a wide range of brain functions and serves as a model system for exploring the role of neural activity in the construction of cortical circuits.

Individual neurons in visual cortex have receptive fields that are responsive to small regions of visual space, and within this region, to specific properties of the visual stimulus such as the orientation of edges, their direction of motion, and color. Moreover, in species with well-developed visual capabilities, neurons exhibiting these properties are arrayed in a systematic fashion that reflects the underlying radial and tangential structure of cortical anatomy. Neurons with similar response properties are clustered together forming radial ‘columns’ that extend from the cortical surface to the white matter. Nearby columns generally have similar but slightly shifted stimulus preferences, an arrangement that results in orderly ‘maps’ of stimulus properties. Our research has played a pivotal role in defining the columnar architecture of cortical circuits and using this architecture as a functional referent to explore rules of intracortical connectivity, address questions of neural coding and behavior, and probe activity dependent mechanisms of cortical development.

Current studies in visual cortex employ in vivo 2-photon imaging, correlative light and electron microscopy, whole cell patch clamp recording, and targeted optogenetic stimulation to:

  • Define the functional architecture of the synaptic inputs to the dendritic spines of individual cortical neurons
  • Determine the functional organization of GABAergic neurons in visual cortex and their contribution to specific response properties
  • Explore the early postnatal patterns of spontaneous neural activity in cortical circuits, follow their development over time, and determine their relation to the emergence of network representations of visual stimuli.
  • Understand the changes in the response properties of cortical neurons that are responsible for the ability to learn fine visual discriminations

Current Projects

Project 1 – Functional synaptic architecture of visual cortex

The discovery by Hubel and Wiesel more than 60 years ago that neurons in visual cortex exhibit remarkably selective responses to specific features of visual stimuli such as the orientation of edges and their direction of motion provided a fundamental mystery of cortical circuit organization that remains unsolved to this day: How do individual neurons compute their functionally selective response properties? The answer to this question is critical to understanding cortical circuit function and development, but until recently we lacked the tools that would allow us to dissect the various factors that contribute to a given response property. By employing in vivo functional imaging and selective stimulation of excitatory and inhibitory neurons at columnar, cellular, and synaptic levels of resolution in the visual cortex of species that have well-developed columnar maps (tree shrew and ferret), we are gaining fundamental new insights into the logic used by cortical circuits to build sensory representations.

Project 2 – Perceptual learning in primary visual cortex

While the selective responses of neurons in primary sensory areas of cortex are well known, how these cortical neurons contribute to perceptual learning remains unclear. At one extreme, V1 neurons may act as a bank of quasi-linear filters which contribute relatively constant sensory signals to downstream areas independent of behavioral context. Alternatively, depending on the behavioral task, the responses of V1 neurons could undergo changes that enhance the sensory basis for behavioral performance. To address the contribution of V1 to perceptual learning, we are using in vivo imaging techniques to explore the responses of layer 2/3 neurons in the visual cortex of tree shrews that learn to make a fine visual discrimination.

Project 3 – Experience-dependent development of cortical networks

The proper construction of cortical circuits depends on a complex sequence of events orchestrated by the interaction of molecular guidance cues and activity dependent mechanisms of synaptic plasticity. We have developed a chronic ferret in vivo imaging paradigm that has made it possible for the first time to track the development of functional cortical representations in individual animals with columnar, cellular, and synaptic level resolution. One set of experiments is probing the emergence of orientation selective responses prior to and after eye opening, and a second examines the developmental mechanisms that are responsible for integrating the inputs from the two eyes to create a single coherent binocular representation.

Project 4 – Functional organization and development of intercortical visual networks

Visual perception is the product of synaptic interactions between neurons in a number of different cortical areas. The functional organization of visual cortical areas beyond primary visual cortex and the nature of their interactions with primary visual cortex remains poorly understood. We are employing a combination of functional imaging and anatomical tracing techniques to map the representation of visual stimuli in extra-striate visual cortical areas and to probe the functional synaptic organization of the reciprocal connections with primary visual cortex in the tree shrew and ferret. Future experiments will employ optogenetic techniques to examine the contribution of feedforward and feedback projections to the responses in different cortical areas, and to visually guided behavior. We also plan to explore the development of intercortical networks and the role of visual experience in their proper formation.

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Fitzpatrick Lab

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