Researchers
at the University of Pittsburgh School of Medicine discovered that a 24-hour circadian
rhythm controls almost all brain and body processes, such as the sleep/wake
cycle, metabolism, alertness and cognition.
According to
Wikipedia, Circadian Rhythm is any biological process that
displays an endogenous, entrainable oscillation of about 24 hours. These
24-hour rhythms are driven by a circadian clock, and they have been widely
observed in plants, animals, fungi, and cyanobacteria.
The
first-of-its-kind study, published in the journal Proceedings
of the National Academy of Sciences, also suggest that a novel
biological clock begins ticking only in the older brain.
"Studies
have reported that older adults tend to perform complex cognitive tasks better
in the morning and get worse through the day,"
"We
know also that the circadian rhythm changes with aging,
leading to awakening earlier in the morning, fewer hours of sleep and less
robust body temperature rhythms.” said Colleen McClung, Ph.D., associate
professor of psychiatry, Pitt School of Medicine.
Etienne
Sibille, PhD, senior co-investigator and Campbell Family Chair in Clinical
Neuroscience at the Centre for Addiction and Mental Health at the University of
Toronto - had also previously shown that gene changes or "molecular
aging" occurs in the brain.
Both teams
set out to investigate
the effects of normal aging on molecular rhythms in the human prefrontal
cortex – part of the brain responsible for learning, memory and other aspects
of cognitive performance. [ওজন কমাতে প্রতিদিন আপনার কতটুকু কার্বোহাইড্রেট
খাওয়া উচিৎ?]
The
researchers analyzed
thousands of genes from brain samples of 146 people with no history of
mental health or neurological problems whose families had donated their remains
for medical research and for whom the time of death was known.
The brains
were categorized depending on whether they had come from a person younger than
40 or older than 60. Next, they analyzed two tissue samples from the prefrontal
cortex for rhythmic activity, or expression, of thousands of genes by using a
newly developed statistical technique.
They used
information about the time of death and identified 235 core genes that make up
the molecular clock in this part of the brain.
The team
discovered that the daily rhythm in all the classic “clock” genes were present
in younger people. Older people however, seemed to have lost rhythm in many of
these genes.
"As we
expected, younger people had that daily rhythm in all the classic 'clock'
genes," said Dr. McClung.
"But
there was a loss of rhythm in many of these genes in older people, which might
explain some of the alterations that occur in sleep, cognition and mood in
later life."
The team was
surprised to find a set of genes that gained rhythmicity in older individuals.
The findings
could be helpful in developing treatments for cognitive impairment and sleep
problems that may occur with aging, as well as a possible treatment for
"sundowning," a condition which makes older people with dementia
become agitated and confused in the evening.
"Since depression is associated with accelerated molecular aging, and with disruptions in daily routines, these results also may shed light on molecular changes occurring in adults with depression."
For further studies, the team is planning to explore the function of the brain's circadian-rhythm genes in lab and animal models. They also find out whether these circadian-rhythm genes altered in people with psychiatric or neurological illnesses,
