This is an image of a human brain, courtesy of Michael Halassa.The thalamic reticular nucleus (TRN) surrounds the thalamus (pictured in red, with a switchboard in the background).
Findings help explain how the brain pays attention to what’s important and how neural circuits may be ‘broken’ in attention-deficit disorders. Researchers at NYU Langone Medical Center say they have added to evidence that the thalamic reticular nucleus or TRN in the central brain, is likely responsible for the ability to routinely and seamlessly multitask.
The process, they suggest, is done by individual TRN neurons that act like a “switchboard,” continuously filtering sensory information and shifting more or less attention onto one sense – like sight – while relatively blocking out distracting information from other senses, including sound.
In their research in mice, TRN neurons, which have been previously implicated in the dampening of brain signals in people, were also less active when the mice were led to focus on – and respond to – a visual flash of light to get a milk reward.
In contrast, when the mice were made to pay attention to a sound and ignore the flash of light, researchers say TRN neurons that controlled vision were more active, suppressing the visual signals in order to pay more attention to the sound. Earlier research by the same team of scientists showed that different TRN neurons controlled specific senses.
“Our latest research findings support a newly emerging model of how the brain focuses attention on a particular task, using neurons in the thalamic reticular nucleus as a switchboard to control the amount of information the brain receives, limiting and filtering out sensory information that we don’t want to pay attention to,” says senior study investigator and neuroscientist Michael Halassa, MD, PhD. “People need to be able to focus on one thing and suppress other distractions to perform everyday functions such as driving, talking on the phone, and socializing.”
The new research sets the stage for ever more detailed studies on the complex behavior involved in how the mammalian brain pays attention to what’s important, and especially how those neural circuits are broken in cases of attention-deficit diseases, such as ADHD, autism, and schizophrenia.
METHOD/RESULTS: behavioral experiment monitoring ability of mice to successfully collect a milk reward by paying attention to a light signal or a sound. The test was designed to gauge how well the area of the brain known to control higher behavioral functions, the prefrontal cortex, could direct the focus on one sense over another. They distracted the mice with opposing stimuli: If the mouse was expecting a flash of light to guide it to the milk reward, the researchers distracted it with a sound, and vice versa. Distracting the mice decreased their ability to collect the food reward to 70% from nearly 90%, even if the distracting stimulus was removed later.
Concurrently, theyrecorded electrical signals from TRN neurons and also tracked the mice’s behavior while at the same time inactivating various parts of the brain’s neural circuits with a laser beam.
MOA: inactivating the prefrontal region of the brain, which is believed responsible for decision-making in complex behaviors, disrupted TRN neural signaling and reduced mice to only random success in obtaining a milk reward when presented with specifically cued light or sound signals. Inactivating the TRN, while leaving the cortical regions intact, also diminished success with obtaining the prompted food reward. Halassa says these results demonstrate how the prefrontal cortex is essential to performing such behavioral tasks and how this part of the brain “stores the knowledge ultimately communicated to the TRN to control how much visual or auditory sensory information is suppressed or not, and how the brain ultimately multitasks.”
Halassa says the team next plans to study exactly how much “distracting” information the TRN can block or allow through and how this mechanism can get disrupted in models of disease, such as autism. http://www.eurekalert.org/pub_releases/2015-10/nlmc-srh101915.php
Recent Comments