Conference Coverage

Conference News Update—Society for Neuroscience


Dot Test May Gauge the Progression of Dopamine Loss in Parkinson’s Disease
A simple dot test could help gauge the extent of dopamine loss in individuals with Parkinson’s disease, according to a pilot study by a multidisciplinary team of investigators. “It is difficult now to assess the extent of dopamine loss—a hallmark of Parkinson’s disease—in people with the disease,” said Katherine R. Gamble, a doctoral student in psychology at Georgetown University in Washington, DC. “This test, called the Triplets Learning Task (TLT), may provide some help for physicians who treat people with Parkinson’s disease, but we still have much work to do to better understand its utility,” she added.

The TLT tests implicit learning, which occurs without awareness or intent and relies on the caudate nucleus, an area of the brain affected by loss of dopamine. The test is a sequential learning task that does not require complex motor skills. In the TLT, participants see four open circles, and then two red dots appear. Patients are asked to respond when they see a green dot appear. Unknown to them, the location of the first red dot predicts the location of the green dot. Participants learn implicitly where the green dot will appear, and their responses become faster and more accurate.

Previous studies have shown that the caudate region in the brain underlies implicit learning. In the study, participants with Parkinson’s disease implicitly learned the dot pattern with training, but a loss of dopamine appears to negatively affect that learning. “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,” said Ms. Gamble. The current study included 27 patients with Parkinson’s disease. The research team is now testing how implicit learning may differ by different stages of Parkinson’s disease and drug doses.

The Eyes May Help Diagnose Alzheimer’s Disease
The loss of a particular layer of retinal cells may reveal the presence of Alzheimer’s disease and provide a new way to track disease progression, according to an international team of researchers. The investigators examined retinas from the eyes of mice genetically engineered to develop Alzheimer’s disease.

“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,” said R. Scott Turner, MD, PhD, Director of the Memory Disorders Program at Georgetown University Medical Center in Washington, DC. “We know there’s an association between glaucoma and Alzheimer’s disease, in that both are characterized by loss of neurons, but the mechanisms are not clear.” Many researchers increasingly view glaucoma as a neurodegenerative disorder similar to Alzheimer’s disease, he added.

Most of the research to date examining the relationship between glaucoma and Alzheimer’s disease focused on the retinal ganglion cell layer, which transmits visual information via the optic nerve into the brain. Before that transmission happens, though, the retinal ganglion cells receive information from another layer in the retina—the inner nuclear layer.

The researchers examined the thickness of the retina, including the inner nuclear layer (which had not been studied previously in this setting) and the retinal ganglion cell layer. They found a significant loss of thickness in both layers. The inner nuclear layer had a 37% loss of neurons, and the retinal ganglion cell layer had a 49% loss of neurons, compared with healthy, age-matched control mice.

In humans, the structure and thickness of the retina can be readily measured using optical coherence tomography. This new tool is finding an increasing number of applications in research and clinical care, said Dr. Turner.

“This study suggests another path forward in understanding the disease process 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. “Parallel disease mechanisms suggest that new treatments developed for Alzheimer’s disease may also be useful for glaucoma.”

Research Suggests Warning Signs and Potential Treatments for MS
Recent research is increasing clinicians’ understanding of multiple sclerosis (MS) and may lead to new treatments and management strategies, said investigators. One study has shed light on the way in which antibodies in the bloodstream break through the blood–brain barrier to attack the optic nerves, spinal cord, and brain, causing the symptoms of neuromyelitis optica. Understanding how the antibodies bypass the blood–brain barrier could provide new approaches to treating the disease.

A protein involved in blood clotting might serve as an early biomarker for MS before symptoms occur, said Katerina Akassoglou, PhD, Professor in Residence of Neurology at the University of California, San Francisco School of Medicine. Early detection of the disease could lead to more effective early treatments.

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