Targetting the impact of HAND

HIV-associated neurocognitive disorder (HAND) is a major neurological complication in HIV-positive persons. It impairs cognitive activity, including memory, learning, attention, problem solving and decision making. Symptoms can vary from confusion to forgetfulness, behavioural changes, nerve pain and sometimes apathy.

Dr Lucette Cysique

Dr Lucette Cysique

The widespread use of combined antiretroviral treatment has reduced the incidence of the most severe form of the disorder, HIV-associated dementia, from 8% to 2%. However, the prevalence of mild to moderate degrees of neurocognitive deficits persists in up to 50% of sufferers, with phases of relapse and remission. Symptoms are not severe enough to be referred to as dementia, yet they impact on quality of life and independence.

Research questions being asked at NeuRA include: to what extent does HAND regress with antiretroviral treatment or cognitive training? Can early treatment reduce HAND incidence? Are HIV-positive persons more likely to have HAND as they age, and could this accelerate common neurodegenerative diseases? Do alcohol and substance use disorders exacerbate HAND? How can we improve the early detection of HAND using improved neuropsychological and/or neuroimaging methods?

To answer these questions, Dr. Lucette Cysique leads and co-leads several studies in Australia working with partners including the UNSW, St Vincent’s Hospital, The Alfred Hospital in Melbourne, and HIV clinics in NSW. Internationally, the University of California San Diego and McGill University in Canada are also part of the research program. NeuRA’s research is pivotal to this exchange network.

A pilot study to assess if computerised cognitive training will improve symptoms of HAND is currently recruiting participants.

Visible neuroscience

Imaging techniques enable neuroscientists to learn about the structure and function of cells in the nervous system. Here, Dr Zoltán Rusznák shares some captivating images of the brain and how they were made.

Neurons are the building block cells of the brain and spinal cord, communicating with each other through synapses to regulate nervous system function. Relating the shape, size, and location of neurons to their function is important in understanding mechanisms in brain health and disease. However, because neurons are small, three-dimensional, and embedded among many other cells in the nervous system, special techniques are required to be able to see them. The following pictures show neurons in the cochlear nucleus, which is the part of the brain that decodes sound information from the ear.

Stacking up to localise sound

Globular bushy cells illuminated by a fluorescent stain

Globular bushy cells illuminated by a fluorescent stain

What’s in this picture? Globular bushy cells are neurons in the cochlear nucleus that act as sophisticated timing devices. They measure tiny delays in how quickly a sound reaches both ears, which is the basis of how we localise the source of a sound.

How was it made? The picture on the left was taken with a camera attached to a microscope. It shows a round bushy cell body in the middle of a single, very thin slice of brain tissue – a slice only 0.06% of the thickness of a grain of salt! The right-hand picture is a stack of 40 images taken from successive slices of the same piece of brain tissue – imagine a stack of salami coming out of a deli slicer. The image stack results in a view of much greater depth, so that a second bushy cell body becomes visible, as well as a detailed view of the synaptic nerve terminals, indicated by the several bright green structures on the cell bodies.

Putting the puzzle together

Giant neurons illuminated by a fluorescent stain

Giant neurons illuminated by a fluorescent stain

What’s in this picture? ‘Giant neurons’ of the cochlear nucleus receive sound information from the ear and help to localise the source of sound from a single ear.

How was it made? These pictures are also made from stacks of single images, like in the previous picture. However, since the giant neurons are so, well, giant, many adjacent image stacks have to be assembled like a puzzle in order to capture the many branching nerve endings. Each square in the pictures corresponds to a single field of view of the microscope.

Merging muscarinic receptors

Granule cells and muscarinic receptors illuminated by fluorescent stains

Granule cells and muscarinic receptors illuminated by fluorescent stains

What’s in this picture? These small round neurons in the cochlear nucleus are called granule cells. Neurons have proteins on their surface called receptors that respond to chemical messengers and transmit signals throughout the neuron. Sometimes we want to know the specific type and location of receptors that a messenger binds to in order to transmit its signal.

How was the picture made? Different fluorescent dyes are used to distinguish the receptor from the rest of the neuron. The left-most image shows green, bead-like dots that indicate the presence of a particular type of receptor called a muscarinic M3 receptor in a slice of brain tissue. The middle picture is taken from the very same piece of brain tissue, but the tissue is instead stained blue to define the nucleus of the granule cells. When the green and blue images are merged (right-hand picture), the green dots are showed to be surrounding the blue cell nuclei. This tells us that the receptors are located on the surface of the granule cells, and suggests that these receptors mediate the effects of certain neurochemical messengers in the cochlear nucleus. This information is helpful to determine how hearing works and what might go wrong in auditory disorders.

Dementia: when do I know I have a problem, and what is happening in my brain?

Dr James Burrell is a Senior Research Officer and clinical neurologist whose research interests lie in linking clinical symptoms and pathology in dementia syndromes.

Dr James Burrell

Dr James Burrell

In my work as a clinical neurologist, I often encounter people who are concerned that they might be developing the dreaded d-word: dementia. They report being more forgetful than previously, forgetting the names of people, places or things, or perhaps just not feeling as ‘sharp’ as they once did. In my experience, these sorts of concerns are common. Importantly, however, only a proportion of people with such symptoms actually go on to develop dementia.

Working out who will develop dementia, and more specifically which type of dementia will be developed, is one of the major challenges cognitive researchers and clinicians face. We are presented with two separate, but related problems: first, how can we tell when minor forgetfulness heralds the onset of something more serious? Secondly, if someone has an obvious dementia, how can we make an early and accurate molecular diagnosis?

We know from many well-designed studies that neurodegenerative disorders begin years before any symptoms develop, and that to be effective a treatment will most likely need to start at the very earliest stages, before any significant and permanent damage develops. On the other hand, not everyone with mild cognitive symptoms actually progresses to develop dementia. Being able to accurately identify patients at risk of developing dementia at a very early stage is one of the major goals of research in neurodegenerative diseases.

In the Frontier clinic based here at NeuRA, we are often faced with the opposite problem: we assess patients with early dementia who present with memory, language, or behavioural disturbances, but it can be difficult to work out the specific underlying brain disease. In many ways, our research aims to bridge this gap between the problems related to ageing that people face in their everyday lives and the physical changes in the brain that are ultimately responsible. We use a combination of methods, including detailed clinical assessment, neuropsychological or cognitive testing, sophisticated brain imaging, neurophysiological techniques, gene testing, and even blood and tissue biomarkers, to try and better link cognitive symptoms and specific brain diseases. With collaborators in the UK we have even developed a new app, for cognitive testing in clinical practice (ACEmobile™ for iPad, available from the Apple App Store). Only after we can make an early and accurate diagnosis of a neurodegenerative brain disorder will the hunt for a meaningful treatment really forge ahead.

Contracture: understanding mechanisms and testing treatments

As part of a new National Health and Medical Research Council Program Grant on motor impairment, Prof Rob Herbert aims to advance the transfer of new understanding of physiology and pathophysiology in motor impairment toward the clinical outcome of improved motor function.

Prof Rob Herbert

Prof Rob Herbert

Motor impairment is a common consequence of a number of illnesses and injuries. One type of motor impairment that is an important cause of physical disability is muscle contracture. A contracture is a stiffening of the muscles that limits normal joint movement, and severe contractures cause deformities that are the most visible manifestation of brain damage. Contractures arise when brain lesions, including those that arise from stroke or traumatic brain injury, cause paralysis or spasticity. Paralysis and spasticity change the mechanical environment of muscles – that is, they cause muscles to experience different patterns of activity, different changes in length and different forces than would normally be experienced. The muscles adapt in response to their altered mechanical environment by becoming stiffer, causing joints to become less mobile.

Contracture is a common problem. In a recent study, my colleagues and I monitored 200 consecutive people admitted to a Sydney hospital with the diagnosis of stroke. Six months after admission, half of all those people had developed at least one contracture. Contractures are also common in people with many other sorts of brain lesions. For example, contractures are prevalent in people who have had a traumatic brain injury, or who have multiple sclerosis or cerebral palsy.

Contractures prevent joint movement, so they cause physical disability. For example, many people who have had a stroke or traumatic brain injury develop contractures of the calf muscles. Calf muscle contractures impede ankle motion, making it difficult to stand up from a chair or walk normally. In the same way, contractures of shoulder muscles can impair the ability to reach and contractures of wrist and finger muscles can impair grasp. Severe muscle contractures can cause the limb to adopt a fixed position. For many people, contractures become a much greater impediment to normal movement than the paralysis or spasticity that initially caused the contracture to develop.

There has been surprisingly little research into the mechanisms of contracture. As a result, the mechanisms are poorly understood. Studies on animals have shown that it is possible to make muscles become short or stiff with a number of experimental procedures. For example, leg muscles can be made short by immobilising the leg in a plaster cast, and diaphragm muscles can be made short by inducing emphysema (a lung disease). These studies show that the stiffening of muscles can occur either because of changes in the muscle tissue (the muscle “fibres” or “fascicles”), or because of changes in the tendons that join muscle fascicles to bones. But studies on animal muscles can’t tell us about the mechanisms of contractures seen in human populations. Surprisingly, it is still not clear whether contractures in people who have had a stroke or traumatic brain injury are due to changes in the muscle fascicles or tendons.

There is just as much uncertainty about how to prevent and treat contracture. For the last half-century, physiotherapists and nurses have applied stretches to muscles, or passively moved limbs, or applied splints or casts to stretch the limb, with the aim of preventing or treating contractures. But recent research suggests these interventions have little effect. For example, in one study, 63 volunteers who had experienced a stroke were randomly allocated to receive either a wrist splint or no splint. Two months later there was no discernable difference in the stiffness of the wrist of people who had or had not been splinted. There have now been over 35 studies like these, and they quite consistently show little or no effect of stretch or movement-based interventions. For now at least, there are no treatments that have been clearly shown to prevent or reverse contracture.

Eventually, scientific research will provide answers, both about the mechanisms of contracture, and about how to prevent and treat contracture. The first steps have been made in identifying the abnormalities of gene expression that are ultimately expressed as contracture. New ideas for treatments are being generated by basic research, for subsequent testing in clinical trials. Our motor impairment program will study human volunteers and patients to learn more about normal motor function and the mechanisms of motor impairment, and to test the clinical efficacy and mechanisms of novel treatment interventions. The development of new techniques for imaging and measuring the internal architecture of muscles using MRI provides one promising advance. One study will look at how muscle tendons and fascicles are recruited during movement, which will inform subsequent clinical studies in people in whom contracture is common, such as people with stroke, spinal cord injury and multiple sclerosis.

Hopefully, the next decade will see major advances in both our understanding of the mechanisms of contracture and how to treat them.

An example of one of the unique muscle images generated by Prof Herbert's team. In the centre is a human leg muscle. The blue lines show the course of muscle cells in six locations in the muscle. The insets provide information about how the cells terminate on the tendinous sheets that cover the upper and lower surfaces of the muscle.

An example of one of the unique muscle images generated by Prof Herbert’s team. In the centre is a human leg muscle. The blue lines show the course of muscle cells in six locations in the muscle. The insets provide information about how the cells terminate on the tendinous sheets that cover the upper and lower surfaces of the muscle.

An international approach to tackling Parkinson’s disease

Dr Nic Dzamko and Prof Glenda Halliday have put together an international team dedicated to researching the causes of Parkinson’s disease. They will be the first in the world to use valuable early clinical samples to identify the genetic and molecular underpinnings of this brain illness.

Parkinson’s disease is a debilitating neurodegenerative disorder with no current cure. 1 in every 30 Australians is diagnosed with Parkinson’s disease, and these numbers are predicted to rise. Over the last 10-15 years, it has emerged that genes play an important role in the risk of developing Parkinson’s disease. Approximately 16 genes have now been identified that increase the risk of developing Parkinson’s disease. Understanding what these genes do in the healthy brain, and how their functionality might go wrong, has become a major focus in the search for clues about the cause of this disease.


Dr Nic Dzamko in the laboratory

One of these genes, called LRRK2, has received considerable attention. The LRRK2 gene encodes a protein that belongs to a class of enzymes called kinases, which is interesting to researchers because many anti-cancer drugs developed by the pharmaceutical industry also act by blocking kinases. In the past few years, more than 20 drugs that can block the kinase LRRK2 have been patented. While it is hoped that these drugs may be beneficial for the treatment of Parkinson’s disease, more work needs to be done to understand exactly what LRRK2 does, and therefore whether drugs that block its action will be safe and therapeutically useful. To better understand the function of LRRK2, our team at NeuRA has initiated two new projects in collaboration with scientists from around the world.

The first project involves us leading a group of scientists from London, Tokyo, California and the Netherlands. Using 400 samples that have been sent to us from these locations, and that cover a range of brain regions at different disease stages, we will determine if, when and where the expression of the LRRK2 enzyme goes wrong in the Parkinson’s brain.

The second project aims to investigate the idea that inflammation is linked with Parkinson’s disease, in collaboration with researchers in the US and Europe. This project is particularly exciting, as it may identify much-needed markers of early disease. By working with the worldwide LRRK2 Cohort Consortium, established by the Michael J Fox Foundation for Parkinson’s Research, we have access to more and better samples to ultimately obtain more meaningful data. We will measure a range of biological markers associated with inflammation in serum and cerebrospinal fluid. By comparing the extent and type of inflammation in people who do and do not have certain genetic mutations, and between people with Parkinson’s disease and healthy controls, we will identify whether inflammation is an early sign of Parkinson’s disease. This world-first access to blood samples from people with a large genetic risk of getting Parkinson’s, but who do not yet have the disease symptoms, is a chance to try and identify potential treatments for the early stages of this illness.

These projects have taken about a year and over 300 emails to come together. Although meetings are often scheduled in the very early hours of the morning to accommodate time zones, working together as an international team to leverage skills and resources is an important step toward solving the problem of Parkinson’s disease. Of course, our work would not be possible without the funding we have received for these projects from the Michael J Fox Foundation and the Shake it Up Australia Foundation.

Of squiggly lines and schizophrenia

Dr Jason Bruggemann is investigating new ways of identifying children at risk of developing schizophrenia.

I am relatively new to schizophrenia research, so I was surprised by the sheer diversity of people I have met who have schizophrenia – men and women from a wide variety of backgrounds with distinct personalities who don’t conform to any particular stereotype. While the disease affects them in different ways, however, they have all described the significant challenges that schizophrenia has posed for them and their families.

Schizophrenia is a neurodevelopmental disorder that typically begins during late adolescence or early adulthood. Healthy development during adolescence involves large-scale reorganisation and restructuring of the brain, including changes to the delicate excitatory/inhibitory balance of the brain’s neurotransmitter systems and underlying brain structure. This process seems to go awry for people with schizophrenia. Environmental factors like stress also appear to contribute to the onset of the disease.

Dr Jason Bruggemann

Dr Jason Bruggemann holds an EEG ‘net’, made up of wires and electrodes.

We know that early diagnosis and treatment can significantly improve long-term outcomes and help minimise the damaging effects of schizophrenia. Hence, current research is focused on potential ways of identifying children at risk of developing schizophrenia. Our colleague Dr Kristin Laurens and her team from Kings College London are currently evaluating a combination of factors as potential early markers, including subtle peculiarities of speech and movement, lower IQ and poorer academic achievement, disturbances in social, emotional, and behavioural functioning, and subclinical psychotic-like experiences such as occasionally hearing voices that nobody else can hear.

At NeuRA, we are conducting research into another potential marker of schizophrenia risk called the mismatch negativity (MMN). The MMN is an index of the brain’s electrical response to changing patterns of sounds. It’s derived from a measure of the electrical activity of the brain called the electroencephalograph (EEG), more commonly known as ‘brainwaves’. The raw EEG signal may look like just a bunch of squiggly lines running across the computer screen but, once analysed, the resulting data can help us better understand patterns of normal and abnormal brain function.

An example of a raw EEG

The squiggly lines of a raw EEG read out.

In adults with schizophrenia, the size of the MMN has been related to disease severity, ability to function in the wider-community (functional outcome), and grey matter volume loss in the frontal and temporal brain regions. The MMN is usually smaller in adults with chronic schizophrenia compared with typical individuals. In light of this, we recently investigated whether a group of children who may be at increased risk of schizophrenia (based on having some of the risk factors described above or having a first-degree relative with schizophrenia) also have a smaller MMN relative to typically developing children.

Our results showed that although the MMN exhibited by the children at risk of schizophrenia was unlike that of their typically developing peers, it also differed from the smaller MMN observed in adults with schizophrenia. In fact, we found a relative increase in the MMN over the frontal brain region, rather than a decrease!

“If we can reliably identify at-risk children then perhaps we can reduce the burden of schizophrenia for future generations.”

It was difficult for us to interpret this result in the context of what we know about MMN in adults with chronic schizophrenia. We looked at MRI data from an overlapping sample of children, which revealed differences in grey and white matter volume in the same brain regions that produce the electrical activity seen in the MMN. Also, the developmental literature indicates that the MMN tends to be larger in young children compared to adults. This has led us to speculate that perhaps the ‘at-risk’ children are on a different developmental trajectory than their peers. It is possible that this unusual MMN result may reflect the complex interplay between developmental changes and the factors placing these children at higher risk of developing schizophrenia.

It’s essential to conduct long-term follow-up of these potentially at-risk children to establish who goes on to develop schizophrenia and how their MMN changes as they mature. This follow-up work, being completed by our colleague Dr Kristen Laurens, will tell us whether the increased MMN we found in this study may indeed be a useful way of identifying children at risk of developing schizophrenia.

The unique people with schizophrenia that I have met currently live their lives as best they can despite the challenges raised by this condition. If we can reliably identify at-risk children then, with appropriate early treatment, perhaps we can reduce the burden of schizophrenia for future generations.

Is high cholesterol putting your brain at risk?

If you want to reduce your risk of Alzheimer’s disease, says Dr Scott Kim, be mindful of your cholesterol levels.

Notwithstanding the recent debate in the media, most of us understand that high cholesterol is harmful to your health because it can negatively affect your heart and arteries.

What you may not know, however, is that high cholesterol can also affect your brain; specifically, there’s growing evidence leading neuroscientists like me to suspect that high cholesterol may increase your risk of developing Alzheimer’s disease.

NeuRA's Dr Scott Kim is investigating the role of cholesterol in Alzheimer's disease

NeuRA’s Dr Scott Kim is investigating the role of cholesterol in Alzheimer’s disease

The growing evidence

Why do we suspect this? Firstly, we know that factors that increase your risk of developing heart disease – specifically, high blood cholesterol levels but also high blood pressure and a history of stroke and diabetes – also increase your risk of developing Alzheimer’s disease. Furthermore, there’s evidence that taking cholesterol-lowering drugs, called statins, decreases your likelihood of developing Alzheimer’s disease.

Another red flag is data from several animal studies suggesting a link between cholesterol and the production of amyloid-beta, the protein that accumulates abnormally in the brains of people with Alzheimer’s disease.

So how is it that high cholesterol increases your risk of Alzheimer’s disease? At NeuRA, we are trying to answer that question.

Cholesterol in the brain

Cholesterol is abundant in our brains; although the brain makes up only two per cent of body’s weight, it contains nearly a quarter of all the body’s cholesterol stores. Cholesterol has important jobs in the brain such as storing energy, acting as a structural component of the cell membrane and acting as a signalling (communication) molecule.

Cholesterol is transported out of cells by transporter proteins, and it’s these proteins – known as ABC transporters – that are the main focus of our research.

Our work has shown that ABC transporters are key regulators of how much cholesterol is inside brain cells. Just recently, we demonstrated that deleting a specific ABC transporter, called ABCA7, in a mouse model of Alzheimer’s disease caused significant increases in amyloid-beta levels. We suspect that the ABCA7 transporter facilitates the clearing of amyloid-beta from the brain. This is direct evidence that ABCA7 is crucial in the development of Alzheimer’s disease.

It’s important to understand what’s happening at a molecular level in Alzheimer’s disease so that we can discover new targets for drug treatments. By understanding the role of ABCA7, we may be able to learn how to inhibit the build-up of amyloid-beta protein and therefore provide potential therapeutic avenues for the treatment of Alzheimer’s disease.

In the meantime…

In the meantime, what can you do in terms of cholesterol to decrease your risk of developing Alzheimer’s disease?

Although controlling cholesterol levels in the brain by altering what you eat is generally very difficult, you can lead a healthy lifestyle and reduce foods in your diet that contain high levels of saturated fat. This will help to reduce the risk factors associated with Alzheimer’s disease that I mentioned earlier on.

Apart from healthy eating and regular exercise, keeping your brain active is also helpful. If playing games, writing a letter or simply interacting with others sounds easy (and it is!), then don’t delay – as the saying goes, ‘use it or lose it’!