Ultimately, understanding cortical circuit function and development requires elucidating the functional synaptic architecture of individual neurons—characterizing the functional properties of a neuron’s synaptic inputs, their strength, their source, how they are arranged within the dendritic field, and how this relates to somatic output.  To address this challenging problem, we have combined in vivo functional imaging of dendritic spines with correlative light and electron microscopy to explore the functional synaptic architecture of excitatory inputs to individual orientation tuned pyramidal neurons in layer 2/3 of visual cortex of the ferret.  Individual pyramidal neurons receive a functionally diverse set of excitatory synaptic inputs that includes preferred orientations that do not elicit a somatic response. Surprisingly, we find no correlation between ultrastructural measures of the synaptic strength of individual spines (spine size and postsynaptic density area), and degree of similarity of spine tuning to that of the soma. Instead, tuning curves based on the relative number of active spines and the aggregate PSD area strongly predict somatic preferred orientation. Our analyses also reveal a high degree of order in the topology of synaptic inputs within the dendritic field including microscale (<10 um) functional clustering and macroscale branch biases relevant to the representation of orientation and visual space, as well as binocular integration.  The functional synaptic architecture of cortical circuits harbors a wealth of under-explored specializations that may be critical for building coherent cortical representations.  


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.

Dr 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.

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

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