They then simultaneously presented the animals with conflicting commands from the lights and tones, but also cued them about which signal to disregard. In the study, the researchers used mice trained to run as directed by flashing lights and sweeping audio tones. In 2015, Halassa and his colleagues discovered another, finer level of gating that further implicated the TRN as part of Crick’s long-sought circuit - this time involving how animals select what to focus on when their attention is divided among different senses. By the time Halassa was a postdoctoral researcher, he had already found a coarse level of gating in that brain area: The TRN seemed to let sensory inputs through when an animal was awake and attentive to something in its environment, but it suppressed them when the animal was asleep. He was drawn to a thin layer of inhibitory neurons called the thalamic reticular nucleus (TRN), which wraps around the rest of the thalamus like a shell. He wanted to determine exactly how sensory inputs got filtered before information reached the cortex, to pin down the precise circuit that Crick’s work implied would be there. That didn’t stop Michael Halassa, a neuroscientist at the McGovern Institute for Brain Research at the Massachusetts Institute of Technology. He developed a theory in which the sensory thalamus acted not just as a relay station, but also as a gatekeeper - not just a bridge, but a sieve - staunching some of the flow of data to establish a certain level of focus.īut decades passed, and attempts to identify an actual mechanism proved less than fruitful - not least because of how enormously difficult it is to establish methods for studying attention in lab animals. A major departure from that line of thinking came in 1984, when Francis Crick, known for his work on the structure of DNA, proposed that the attentional searchlight was controlled by a region deep in the brain called the thalamus, parts of which receive input from sensory domains and feed information to the cortex. Hunting for Circuitsįor a long time, because attention seemed so intricately tied up with consciousness and other complex functions, scientists assumed that it was first and foremost a cortical phenomenon. Perhaps more importantly, they’ve found that this process involves more ancient regions much deeper in the brain - regions not often considered when it comes to attention.īy doing so, scientists have also inadvertently started to take baby steps toward a better understanding of how body and mind - through automatic sensory experiences, physical movements and higher-level consciousness - are deeply and inextricably intertwined.
But now, some researchers are trying a different approach, studying how the brain suppresses information rather than how it augments it.
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