The Role of Apical Dendrites in Attention
Randy Bruno, Ph.D.
College of Physicians & Surgeons of Columbia University
David Mahoney Neuroimaging Program
September 2010, for 3 years
Examining how the brain facilitates the ability, or inability, to focus attention
Researchers will use two-photon cellular imaging in mice as an initial step in determining whether a specific brain network facilitates attention and, if disordered, fails to do so in human disorders such as Attention Deficit Hyperactivity Disorder (ADHD) and Schizophrenia.
The ability to selectively focus on relevant sensations while ignoring distracting ones is indispensible to normal behavior and the inability to do so is characteristic of people with ADHD and schizophrenia. While scientists have made progress in identifying and characterizing brain structures that allocate attention, the development of targeted drugs to treat disordered attention requires an understanding of which types of brain cells, which layers of cells in the brain, and which synapses (connections) among brain cells are involved. By studying animals during wakefulness (attention) and during anesthesia (lack of attention), the Columbia investigators found that higher order cortical areas in the brain exert top-down control of sensory regions. The axons (message senders) of cells in the cortex reach up to dendrites (message receivers) of sensory cells located near the brain’s surface, called “layer 1.” The investigators hypothesize that this top-down control by cortical neurons in layer 1 acts like a spotlight, focusing attention on selected, rather than less relevant
, sensory sensations.
They will test this hypothesis using two-photon imaging in mice while they perform a task that requires sensory attention. Because mice use their large facial whiskers to sense their environment though the sense of touch, they will be trained to detect an object presented at either of two spatial locations. Then, on some trials, a distracting object also will be presented. The researchers predict that attended objects will activate layer 1 more strongly than distracter objects; and that communication among cells in layer 1 is required for both neural activity and behavior. If this is the case, the results would provide an initial understanding at the cellular level of how attention affects sensory processing.
Significance: The results could provide targets for testing experimental drugs to treat attention disorders in animal models, such as the new mouse model for schizophrenia; successful therapies then could be tested in human clinical trials.