Tuesday, December 12, 2017
Friday, December 8, 2017
Out of the mouths of babes and sucklings
There is an ongoing debate about where Parkinson’s starts. The most accepted hypothesis of Braak and colleagues suggests that it starts outside the brian, either in the olfactory (smelling) nerve, or potentially in the gut. Some evidence suggested that people who had had surgery to cut the nerve to their stomach to treat stomach ulcers were at lower risk of Parkinson’s, which added weight to the theory that Parkinson’s might ‘ascend’ through the nerves of the gut to the brain. This fits nicely with the theory that changes in the microbiome (the overall ecosystem of bacteria and other microorganisms) in the gut plays a part in Parkinson’s. However, this finding has been disputed by other studies.
A report published this month, continues the story elsewhere in the digestive tract. Using the highly reliable public health records of the Danish health and civil registration scheme, they tried to find a relationship between having a tonsillectomy and future risk of Parkinson’s. They examined ther records of over a million people, including 195,000 who’d had tonsillectomy, primarily in childhood. They found 100 people who developed Parkinson’s from the tonsillectomy group at a rate of 0.31 (true figure in the region of 0.22-0.34) cases of Parkinson’s per 100,000 person-years, and 568 cases of Parkinson’s in the comparison group at 0.27 (true figure in the region of 0.29-0.34) cases of Parkinson’s per 100,000 person-years. There was no significant difference between the two groups. Therefore, there is no evidence of any effect of tonsillectomy on the risk of developing Parkinson’s.
This is an important negative finding, and the editor of Movement Disorders should be congratulated on publishing it. It is notoriously difficult to publish ‘negative’ studies, as they rarely make headlines in the broadsheets (when was the last time you read that X had no effect on Y, compared to the last story you read claiming that your favourite food put you at risk of …) Although they found no evidence of an effect, that still isn’t quite the same of finding evidence of no effect; and so the debate rages on.
Tonsillectomy and Risk of Parkinson’s Disease: A Danish Nationwide Population-Based Study
Svensson E1,2, Henderson VW1,3,4, Szépligeti S1, Stokholm MG5, Klug TE6, Sørensen HT1,3, Borghammer P5.
Background: We hypothesized that tonsillectomy modifies the risk of PD.
Objectives: To test the hypothesis in a nationwide population-based cohort study.
Methods: We used Danish medical registries to construct a cohort of all patients in Denmark with an operation code of tonsillectomy 1980-2010 (n = 195,169) and a matched age and sex general population comparison cohort (n = 975,845). Patients were followed until PD diagnosis, death, censoring, or end of follow-up 30 November 2013. Using Cox regression, we computed hazard ratios for PD and corresponding 95% confidence intervals, adjusting for age and sex by study design, and potential confounders.
Results: We identified 100 and 568 patients diagnosed with PD among the tonsillectomy and general population comparison cohort, respectively, finding similar risks of PD (adjusted hazard ratio = 0.95 [95% confidence interval: 0.76-1.19]; for > 20 years' follow-up (adjusted hazard ratio = 0.96 [95% confidence interval: 0.64-1.41]).
Conclusion: Tonsillectomy is not associated with risk of PD, especially early-onset PD. © 2017 International Parkinson and Movement Disorder Society
Tuesday, November 28, 2017
Neuroscience says it's good to daydream
MORE STORIES FROM THIS EPISODE
- Meet the human guinea pig who hacked his own DNA
- If you're going to get hurt, you're better off doing it during the day
- Neuroscience says it's good to daydream
- What's the one thing scientists want the world to know about their field?
- Find out why scientists no longer fear a discovery that dwarfs the power of an H-bomb
- FULL EPISODE
Poets and philosophers have long talked about the quiet, contemplative times of reflection in our lives. Now neuroscientists are finding our brains are really on fire during these restful periods when the brain daydreams.
People had assumed that since we're not doing anything during daydreams that the brain would be on idle.
In fact, a network of activity takes place during daydreams.
The neuroscientists say, daydreams reflect the brain's default mode network — the attentional system when you're not in control of your thoughts and they drift loosely from one to another. It's when much of our creativity and problem solving occurs.
Dr. Daniel Levitin, an emeritus professor of neuroscience and music at McGill University in Montreal, saw it when he scanned the brain of Grammy winner Sting.
To study brain activity, Levitin uses EEG and a functional magnetic resonance imaging (fMRI) scanner, a machine that noninvasively measures brain activity by detecting changes in blood flow.
When Sting composed in the scanner, Levitin was surprised to find the musician's visual cortex at the back of his head was active. Normally, scientists only see activity there when a subject is watching a movie or dreaming of a scene.
"I asked him about it and he said that when he composes music, he thinks of music as architecture as having different levels of structure and buttresses," Levitin tells CBC Radio Quirks & Quarks host Bob McDonald. "He thinks of it in a very visual, spatial way."
Levitin says we're experiencing daydreams when the brain drifts as we read, as our eyes seem to get ahead of us and we don't know what we just took in, or when a driver misses an exit on the highway as the conscious part of the brain fails to pay attention.
To neuroscientists, the daydream or default brain network isn't a physical place in the brain. It's a network of brain circuits connected together.
Like Levitin, Dr. Kalina Christoff is drawn to the study of how the default brain network fuels creativity. Christoff is a professor of psychology and Peter Wall scholar at the University of British Columbia in Vancouver.
Christoff first became interested in daydreams during her childhood growing up in Bulgaria. She spent the summers physically wandering through orchards and fields, where she found that letting her mind wander was extremely enjoyable.
As an adult, she realized this resting state of the brain baffled psychologists because they couldn't explain it.
Christoff says most creative people, regardless of the type of art, flip flop between spontaneously brain storming and appraising the results.
"Unbridled freedom of thought and spontaneity could be hugely important for creativity but it's only half of what's necessary," Christoff says. "The other half is to be incredibly critically and in a very constrained way evaluate the products."
But when people show extremes in that range between freedom and constraints in their thoughts, mental illnesses can occur, Christoff says.
For instance, she says extreme freedom of thought correlates with the disordered thoughts of psychosis. In depression and obsession, thoughts are extremely constrained.
She says healthy, creative people reach those extremes, but they don't get stuck there.
In contrast in rumination, our thoughts become fixated on a particular worry, such as an argument with a friend.
Christoff collaborates with Dr. Zach Irving of the University of Virginia.
- Dr. Zach Irving
Irving is an assistant professor of philosophy with a personal interest in attention deficit hyperactivity disorder. He was diagnosed as being on the spectrum for ADHD as an adult and was drawn to study how his mind works differently from others.
In ADHD, daydreams or mind wandering is exaggerated, Irving says. It can have costs in terms of not being able to concentrate in class, but it also has benefits.
"People with ADHD tend to have more creative achievements than their age-matched peers," Irving says.
He acknowledges there's been a bit of a pushback from some in the ADHD community with more severe forms who don't want the debilitating aspects of the illness to be characterized as a positive. It's important to consider how ADHD affects someone's life, Irving says.
Irving sees the limitations of research that fails to distinguish between concepts like mind wandering and rumination. It's why he and Christoff published what he calls a dynamic framework for mind wandering in a recent issue of Nature Reviews Neuroscience.
At her lab, Christoff continues to study how people talk their way through puzzles that have no obvious answer. The puzzles offer a non-technological way for her to explore how creativity relates to spontaneous thought.
Other neuroscientists are exploring how daydreams contribute to intelligence.
Last month, Christine Godwin, a PhD candidate at the Georgia Institute of Technology, published a study based on brain pattern measurements of more than 100 people who laid in a MRI machine.
Those who reported more frequent daydreams scored higher on intellectual and creative ability and had more efficient brain systems as measured in the MRI, Godwin found.