Optogenetic techniques have been used to alter the attention spans of mice, helping to shed light on how the brain mediates internal thoughts and external distractions. A team from New York University’s Langone Medical Center focused on the thalamic reticular nucleus (TRN) of the mouse brain. Introducing light-sensitive molecules into the region allowed the researchers to precisely control the firing patterns of visual TRN cells with laser pulses. Located deep inside the brain, the thalamus relays information from the body to the cerebral cortex. The TRN cells are thought to act as switchboard operators that control the flow of information, the researchers said. “Now we may have a handle on how this tiny part of the brain exerts tremendous control over our thoughts and perceptions,” said lead researcher Dr. Michael Halassa, an assistant professor at Langone. “These results may be a gateway into understanding the circuitry that underlies neuropsychiatric disorders.” The researchers identified TRN cells that send inhibitory signals to the areas of the thalamus known to relay visual information to the cortex. Using multielectrode recordings, they demonstrated that sleep and concentration affected such cells in opposite ways. Well-rested mice needed just a second or two to find food, whereas sleep-deprived mice took longer. But when the researchers used flashes of laser light to inhibit the firing of optogenetically-engineered visual TRN cells in sleep-deprived mice, the mice found the food faster. In contrast, using optogenetics to induce sleep-like firing patterns caused well-rested mice to take longer finding the food. “It’s as if with a flick of a switch we could alter the mental states of the mice and either mimic or cure their drowsiness,” Halassa said. The research was published in Cell (doi: 10.1016/j.cell.2014.06.025). For more information, visit www.med.nyu.edu.