Tiny antennae-like organelles, once thought to be remnants of our ancient past, seem play a crucial role in time tracking, according to a recent mouse study by researchers at the University of California, Irvine (UCI), in the United States.
Known as cilia, projections of microtubules can be found in the most complex branches of the tree of life, including on many of our own cells.
Where they often play a role in movement, either pushing cells or moving materials near their surface, most human bodies – described as primary cilia – are stationary.
The first investigations more than a century ago considered these types of structures as remains. Today, many primary cilia are recognized as part of a signaling hub system that allows the body to adapt and respond appropriately.
While various roles of primary cilia in receiving and responding to sensory information have been established, little is known about how these organelles integrate with higher-order cognitive functions that take place in the brain.
Part of the job of the area of the brain known as the striatum is to act as this central clock, coordinating motor movement, learning, planning and decision-making. It is also important for managing working memory and maintaining attention.
For their study, the researchers used a genetic manipulation technique to eliminate striatum cilia in mice, which had a dramatic effect.
While the mice could still retain long-term memories and habitual or previously learned motor skills, various negative effects were observed after the eyelashes were removed.
The rodents were unable to learn new motor tasks and showed repetitive motor behavior as well as noticeable delays in decision making. Their ability to quickly recall location and orientation information, and their ability to filter out irrelevant environmental sensory information, were negatively affected.
A variety of tests and exercises were performed with the mice to draw these conclusions, including running the animals through mazes and testing their ability to recognize objects and places.
“Successful performance of working memory, attention, decision-making, and executive function requires precise and precise timing judgment, typically within a millisecond to a minute,” says the UCI neuroscientist Amal Alatchkar.
“When this ability is impaired, it means losing the ability to quickly adjust behavior in response to changes in external stimuli and failing to maintain appropriate, goal-oriented motor responses.”
It is clear that all the impacts of eyelash removal have one common characteristic: the loss of the ability to rapidly change behavior in response to changes in the environment within an appropriate timeframe.
The relationship between the results of this study and humans is not yet fully known, but it is likely that the cilia in the human brain function in the same way as those in mice. The researchers are already working on follow-up studies to more closely analyze the relationship between eyelashes and the perception of time.
Not only does this discovery improve our understanding of how we perceive the world, but it could also help us fix it in case our view of time is wrong.
Poor perception of time and poor judgment of time are features found in many mental and neurological disorders, including schizophrenia, Parkinson’s disease, Tourette’s syndrome, autism spectrum disorders and Huntington.
“Our findings may open new avenues for effective intervention through cilia-targeted therapies for treatment,” says Alachkar.
“Our ongoing work aims to understand the mechanisms by which cilia regulate time perception and to develop targeted therapies to ameliorate behavioral deficits.”
The research has been published in Molecular Neurobiology.
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