Research news in brief

Decline in navigational skills linked with Alzheimer’s

International research published in Neuron has reviewed how changes in the way humans map their surroundings and construct and follow directions as they age could form the basis for tools for the early diagnosis of Alzheimer’s disease. Currently, Alzheimer’s disease is diagnosed based on an individual’s medical history, genetic risk factors, and performance on tests that measure memory, language and reasoning impairments. Researchers from Germany, the US and the UK suggested that navigational impairments are among the earliest signs of the Alzheimer’s progression. Healthy older individuals, for instance, strongly prefer to map objects and landmarks relative to their body position (an egocentric strategy) rather than in relation to external objects, such as global landmarks or boundaries (an allocentric strategy). This strategic bias makes it much more difficult for them to learn the spatial layout of an environment and can thus reduce their mobility, a worrisome sign in younger people. “It can take up to 10 years after the onset of Alzheimer’s for someone to show abnormal results on the standard cognitive tests that are available today, and that’s 10 years that you’ve lost for treating it, should an effective therapy come along down the road,” said lead researcher Thomas Wolbers. “This is where navigation-based diagnostics could contribute, by reducing that window.” Navigational testing is held back by the lack of standard tests for navigational tasks and population norms with which to evaluate results. However, more affordable and portable virtual reality technology is making standardised test conditions possible. The other barrier is that navigational abilities vary wildly from person to person, more so than for memory or other cognitive functions. An effective diagnostic tool may need to be longitudinal, tracking an individual’s navigation behaviours at different points in time throughout their life and looking for signs of early or accelerated decline.

Stem cell therapy for Parkinson’s disease

Japanese researchers have used stem cell therapy to restore nerve function and improve movement in monkeys with the equivalent of Parkinson’s disease, according to research published in Nature. The preclinical study showed that implantation of dopaminergic neurons derived from human induced pluripotent stem cells (iPSCs) can improve movement in affected monkeys. The results indicated that this approach could potentially be applied to the clinical treatment of human patients with Parkinson’s disease. iPSCs are adult cells that have been reprogrammed to become capable of differentiating into a range of different cells. Human iPSCs are a promising source for cell-based therapy to replace damaged nerve cells in the brains of patients with neurological disease (in the case of Parkinson’s disease, nerve cells that use dopamine to communicate – dopaminergic neurons – are those that are damaged). To date, no long term study of human iPSC-derived dopaminergic neurons in primate models of Parkinson’s disease has been performed. The researchers assessed the safety and function of such neurons by implanting them into the brains of monkeys exhibiting a model of Parkinson’s disease. They showed that these human-derived cells displayed long term survival, functioned as midbrain dopaminergic neurons, and restored a range of movements. The cells did not form any tumours in the brains for at least 2 years and elicited either no or only a mild immune response.

New screening test for pregnancy complications

Researchers from the Victorian Clinical Genetics Services at the Murdoch Childrens Research Institute and Illumina’s Northern California Services Laboratory have developed a method to allow women to gain greater insights into the health of their pregnancy. During pregnancy, small fragments of genetic material pass from the placenta into the mother’s bloodstream. This genetic material can be tested using a non-invasive prenatal test (NIPT) to provide important information on the health of pregnancy. Pregnant women can already access NIPT, which is a highly accurate method for screening chromosome conditions such as Down syndrome. Down syndrome, also known as trisomy 21, is caused by an extra copy of chromosome number 21, where there are three copies of chromosome 21 instead of the usual two. Current NIPT methods only test for the most common trisomies, including chromosomes 21, 18, 13, X and Y. The new research, published in Science Translational Medicine, is looking at the possibility of expanding this blood test to check for other important health concerns caused by rarer chromosome conditions. The study looked at nearly 90 000 pregnancy plasma samples from two clinical laboratory cohorts in Australia and the US. This study expanded the NIPT to look at all chromosomes. Both cohorts identified similar frequencies of rare trisomies, and trisomies 7, 15, 16 and 22 were the most frequently observed rare autosomal trisomies in both cohorts. Cytogenetic or pregnancy outcome data were available in 52 out of 60  cases (87%) with rare autosomal trisomies in cohort 2 – where rare autosomal trisomies detected were associated with miscarriage, fetal growth restriction and spontaneous fetal death. In some cases, only the placenta was affected by the rare trisomy and not the baby, but this could still cause serious problems for the normal development of the pregnancy. “This may help doctors in monitoring pregnancies at increased risk for complications, such as fetal growth restriction, and may also provide a reason for why some pregnancies have miscarried,” said Dr Mark Pertile, the lead author.

Interfacing brains with computers for stroke recovery

Researchers from the University of Adelaide and the University of South Australia have discovered that they can enhance stroke rehabilitation with the use of a brain-computer interface (BCI) system. The BCIs overcome a previous issue in the technology, in which the patient’s brain triggers a movement on a screen, but the patient receives no feedback to their senses. The authors wrote in Royal Society Open Science that their device provides the needed feedback, and it provided a single patient with a 36% increase in relevant test scores over the course of the training. “To the best of our knowledge, the optimal feedback update interval (FUI) during motor imagery remains unexplored,” the authors wrote. “There is evidence that sensory feedback disinhibits the motor cortex. Thus, in this study, we explore how shorter than usual FUIs affect behavioural and neurophysiological measures following BCI training for stroke patients using a single case proof-of-principle study design. The action research arm test was used as the primary behavioural measure and showed a clinically significant increase (36%) over the course of training. The neurophysiological measures including motor evoked potentials and maximum voluntary contraction showed distinctive changes in early and late phases of BCI training. Thus, this preliminary study may pave the way for running larger studies to further investigate the effect of FUI magnitude on the efficacy of restorative BCIs. It may also elucidate the role of early and late phases of motor learning along the course of BCI training.

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