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     The main focus of our research is to understand how different regions in the brain interact and exchange information to mediate behavior in health and neurological disorders.
     Our laboratory focuses on three main topics: Attention Networks; Electrophysiology and Function of Intrinsic Activity; and, Neurological Mechanisms of Recovery.
     Our interest in attention stems from its importance as one of the foundations of cognition. Without attention no other cognitive function is possible. Attention involves the selection of important stimuli and responses, thus the coordination of activity in space and time across regions and networks of the brain.  We have discovered two networks (the dorsal and ventral attention networks) that are specialized for attention control, and we are studying their spatial and temporal properties as people perform cognitive tasks.
     The coordination among brain regions requires among other things an interaction between ongoing patterns of intrinsic activity and task-evoked activity/networks.  The brain contains 1012 neurons and each neuron is connected approximately with 104 other neurons leading to an estimate of about 1016 synapses in the brain.  Interestingly, only about 1 million axons enter the brain from the retina, and about only 1 million axons exit the brain toward the spinal cord to control movement.  Therefore, the majority of brain activity is intrinsic, not sensory or motor-driven.  Furthermore, through fMRI studies we know that intrinsic activity is organized in a finite number of brain networks that are synchronized at rest, but combined in different motifs during behavior. We are currently investigating not only the neurophysiological basis of intrinsic activity, but also its modification during task performance.
     Finally, networks of intrinsic or task-driven activity are disrupted by focal brain injuries (stroke, traumatic brain injury). We have shown that behavioral deficits depend on the physiological disruption of brain regions/networks that are not directly damaged.  Similarly, recovery of function may depend on the functional reorganization of structurally intact regions of the brain. We are currently characterizing patterns of network damage for different types of behavioral impairment (motor, attention, memory, language), and assess the relative importance of structural vs. functional damage.  These studies will not only elucidate the normal organization of the brain, but also identify patterns of activity that are potentially treatable through a variety of different approaches (rehabilitation, stimulation, brain-computer interface) to improve function.

contact hoffmant@npg.wustl.edu