Society for Neuroscience

Simple Test May Help Gauge Dopamine Loss in Parkinson’s.

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The Triplets Learning Task (TLT) may help determine the extent of dopamine loss in patients with Parkinson’s disease (PD), results of a pilot study hint.

The TLT tests implicit learning, a type of learning that occurs without awareness or intent and that relies on the caudate nucleus, an area of the brain affected by dopamine loss.

The test is a sequential learning task that doesn’t require complex motor skills, which tend to decline in people with PD. In the TLT, participants see 4 open circles, see 2 red dots appear, and are asked to respond when they see a green dot appear. Unbeknownst to them, the authors note, the location of the first red dot predicts the location of the green target. Participants learn implicitly where the green target will appear, and they become faster and more accurate in their responses.

Katherine R. Gamble, psychology PhD student at Georgetown University in Washington, DC, and colleagues had 27 patients with mild to moderate PD receiving dopaminergic medication and 27 healthy controls matched for age and education take the TLT on several occasions.

Patients with PD implicitly learned the dot pattern with training, as did controls, but a loss of dopamine appeared to “negatively impact” that learning compared with healthy older adults, Gamble noted in an interview with Medscape Medical News.

“Their performance began to decline toward the end of training, suggesting that people with Parkinson’s disease lack the neural resources in the caudate, such as dopamine, to complete the learning task,” she added in a conference statement.

Gamble reported the findings here at Neuroscience 2013, the annual meeting of the Society for Neuroscience.

Implicit Learning

In this study, participants responded to 6 “epochs” of the TLT, for a total of 1500 trials. All patients had been diagnosed with PD by a neurologist, and all were receiving treatment with anti-PD medication when they took the test.

Their results showed “significant implicit sequence learning” on the TLT test, the researchers report. Learning increased over the first 5 epochs of training, they note; patients continued to respond more quickly to high- vs low-probability triplets, but this plateaued between periods 5 and 6.

“We suggest that in people with PD, learning is intact early in training because less affected regions of the brain (eg, the hippocampus) can support learning,” they conclude. “However, PD-related dopamine deficits appear later in training when the caudate becomes more important.”

The TLT “may be a noninvasive way to evaluate the level of dopamine deficiency in PD patients, and which may lead to future ways to improve clinical treatment of PD patients,” said Steven E. Lo, MD, associate professor of neurology at Georgetown University Medical Center and a coauthor of the study, in a statement.

The researchers are now testing how implicit learning may differ by different PD stages and drug doses.

Evaluating Dopamine Deficiency

Asked to comment on this pilot study, Lidia Gardner, PhD, assistant professor, Department of Neurology, University of Tennessee Health Science Center in Memphis, said the “simple implicit learning test might be potentially a useful tool for neuropsychologists. I would like to know if there is any correlation between the disease progression and the time required for TLT training.”

However, she told Medscape Medical News, “Until a strong correlation is established, most physicians would shy away from using it as a diagnostic tool for the loss of dopamine neurons. However, in addition to other clinical tests it could be useful.”

“Currently, the loss of dopamine neurons can be visualized with PET [positron emission tomography] using 18F-DOPA or other radio-tracers. This technique can give a relatively close assessment of dopamine neurons in PD patients. A simple and inexpensive test (in comparison to PET or SPECT [single-photon emission computed tomography]) is always welcome in healthcare administration,” Dr. Gardner said.

Exercise while pregnant may boost baby’s brain.

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This week, Baby V and I have joined more than 30,000 neuroscientists in San Diego for the annual Society for Neuroscience meeting. We’ve wandered the miles of posters, dropped in on talks and generally soaked up the brain waves floating around this massive meeting of minds.

We’ve worked up a sweat more than once rushing around the meeting, so it’s nice to be reminded of all the exciting research on the benefits of physical exercise on the brain. Evidence is piling up that a fit body is one of the absolute best things you can do for a fit mind. And a study presented November 10 shows that if you’re pregnant, the benefits of exercise extend to your baby’s brain too.

Researchers from the University of Montreal asked pregnant women to exercise three times a week for 20 minutes until they were slightly short of breath. Other pregnant women didn’t exercise.  Eight to 12 days after the babies were born, the team recorded the electrical activity in sleeping babies’ brains.

Babies born to moms who exercised showed more localized brain activity patterns in response to sounds, the researchers found. This targeted brain activity is a sign of brain maturity, indicating that the brain is becoming more efficient. Babies whose mothers didn’t exercise during pregnancy showed more diffuse brain responses to sounds. The scientists plan on looking for lasting benefits by testing the babies at age 1.

Studies in rodents have found benefits of exercise during pregnancy: Rats born to moms who worked out have brains that are more resistant to low oxygen conditions, for instance. Maternal exercise boosts levels of cellular powerhouses called mitochondria in rat pups’ brains.  And exercise during pregnancy resulted in more newborn neurons in the mouse hippocampus, a brain region involved in learning and memory. Now, this new study suggests that some of these benefits might extend to people, too.

So, exercise is good for mom and good for baby. Now Baby V and I just need to find a study that reports exercise — specifically, walking miles and miles at a neuroscience conference — helps a baby to sleep through the night.

Eyes cells help diagnose Alzheimer’s

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Changes to specific cells in the retina could help diagnose and track the progression of Alzheimer’s disease, scientists say.

A team found genetically engineered mice with Alzheimer’s lost thickness in this layer of eye cells.

Alzheimer's brain (left) compared with healthy brain (right)

As the retina is a direct extension of the brain, they say the loss of retinal neurons could be related to the loss of brain cells in Alzheimer’s.

The findings were revealed at the US Society for Neuroscience conference.

The team believes this work could one day lead to opticians being able to detect Alzheimer’s in a regular eye check, if they had the right tools.

“Start Quote

[This] could lead to new ways to diagnose or predict Alzheimer’s that could be as simple as looking into the eyes”

Dr Scott Turner Georgetown University Medical Center

Alterations in the same retinal cells could also help detect glaucoma – which causes blindness – and is now also viewed as a neurodegenerative disease similar to Alzheimer’s, the researchers report.

Scott Turner, director of the memory disorders programme at Georgetown University Medical Center, said: “The retina is an extension of the brain so it makes sense to see if the same pathologic processes found in an Alzheimer’s brain are also found in the eye.”

Dr Turner and colleagues looked at the thickness of the retina in an area that had not previously been investigated. This included the inner nuclear layer and the retinal ganglion cell layer.

They found that a loss of thickness occurred only in mice with Alzheimer’s. The retinal ganglion cell layer had almost halved in size and the inner nuclear layer had decreased by more than a third.

“This suggests a new path forward in understanding the disease process in humans and could lead to new ways to diagnose or predict Alzheimer’s that could be as simple as looking into the eyes,” said Dr Turner.

Alzheimer’s disease

A coloured CT scan image of a human brain
  • Symptoms include loss of memory, mood changes, and problems with communication and reasoning
  • No one single factor has been identified as a cause for Alzheimer’s disease – a combination of factors, including age, genes, environment, lifestyle and general health are implicated
  • One of the leading theories involves the formation of clumps of a protein called beta-amyloid, which damage and kill brain cells

Treatments developed for Alzheimer’s could therefore also be useful for treating glaucoma, he added.

But he also said that so far it was still speculation to say that retinal thinning may predict impending Alzheimer’s disease.

“We’re hoping that this translates to human patients and we suspect that retinal thinning, just like cortical thinning, happens long before anyone gets dementia,” Dr Scott told BBC News.

“Human studies are needed to test this idea as a diagnostic [test]. Current leading biomarkers of Alzheimer’s disease are either very costly or invasive. A retinal thickness scan – as measured by optical coherence tomography – would be both inexpensive and non-invasive.”

Alzheimer’s is a neurodegenerative disease and is the most common type of dementia. The cause is still unknown and there is currently no cure. It often goes undetected for years until so many cells die that symptoms become increasingly prevalent.

But treating the disease early is believed to be vital to prevent memory loss.

Laura Phipps, at Alzheimer’s Research UK, said there was increasing evidence linking retinal cell loss to Alzheimer’s disease, and that it was “positive to see this line of research being followed up”.

“This early-stage study, which is yet to be published in full, was carried out in mice, and further research will be necessary to determine whether changes in the retina found here are also found in people with Alzheimer’s.

“Diagnosing Alzheimer’s with accuracy can be a difficult task, which is why it’s vital to continue investing in research to improve diagnosis methods,” Dr Phipps added.