While maintaining balance appears effortless and relatively simple, it depends on a complex integration of sensory and motor signals that originate from a variety of sources in the body. When you turn your head, even though the vestibular organs of the inner ear change their orientation relative to the body, they still provide information which can be used to aid balance. This response relies on information received from vestibular organs (which measure linear and angular acceleration of the head) and sensory information from the neck (which conveys the head’s position). These two signals are then integrated to provide contextually specific directional information to the brain. As such, patients with damage to their vestibular organs tend to be posturally unstable. The cerebellum has emerged as a potential contributor to the convergence and interpretation of vestibular and somatosensory information in the brain. Patients with cerebellar dysfunction often exhibit similar abnormal balance behaviour to those with vestibular damage. Christopher Dakin is investigating the cerebellum’s role in the vestibular systems influence on balance. He is comparing postural responses associated with vestibular activation among two groups: healthy people, whose cerebellar function is temporarily inhibited by a technique called Transcranial magnetic stimulation; and individuals with spinocerebellar ataxia, a neurological disease marked by atrophy (wasting) of the cerebellum. By increasing our understanding of the human nervous system as it relates to cerebellar processing of vestibular information, Dakin’s research will contribute to more accurate balance disorder diagnoses and treatments. Ultimately, his work could lead to improved therapeutic and rehabilitative techniques directed towards patients with vestibulo-cerebellar dysfunction.
Research Pillar: Clinical
Effect of cam-type deformity associated with femoroacetabular impingement on hip mechanics
Hip osteoarthritis (OA) is a painful condition affecting 4.4 per cent of the population aged 55 and older. Currently, there are very limited treatment options and no known cure for OA. Improving prevention and treatment of early hip OA requires a thorough understanding of the joint mechanics and how these mechanics affect the initiation and progression of the disease. Hip OA can either be primary (occurs with no previously known cause) or it can be secondary to a known deformity. It has recently been hypothesized that most “”primary”” cases are actually caused by small deformities in the joint that were previously unnoticed. One deformity that has been found to have a strong correlation with hip OA is called a cam deformity, which can cause pain and decreased range of motion in the hip. Cam deformities occur on the upper femur (thigh bone) and cause increased contact between the femur and the acetabulum (hip socket). Joint contact pressure is thought to play a role in accelerating the onset of OA. To determine the association between cam deformity and the onset of hip OA, Laura Given is studying how the joint mechanics change depending on the degree of cam deformity. She will track how the joint translations and rotations are affected throughout the range of motion of the hip and determine how the range of motion is affected by simulated cam deformity. By describing how the size of cam deformity affects joint mechanics, Given’s research will help surgeons understand how to effectively correct the deformity in an effort to slow or even stop the osteoarthritic disease progression. It could also lead to preliminary guidelines in arthritis screening programs. This could reduce the number of cases of hip OA seen in the future.
The reliability and validity of the External Hostile Attributions Scale (EHAS) in a sample of civil psychiatric patients and criminal offenders
Violence, victimization, and suicide-related behaviours have many negative consequences on society and are viewed as critical public health issues. It is estimated that 2,000,000 violent crimes are committed each year in Canada, and that costs to victims, such as health services, approximate $47 billion annually (Statistics Canada, 2003). In addition to the important costs to the healthcare system, these violent outcomes greatly affect individuals’ quality of life as well as mental and physical health. Melissa Hendry’s research aims to reduce the risk of these negative behaviours by investigating risk factors for such behaviours; specifically, she is interested in hostile attributions, which is the attribution of malevolent intent to others, which she will study in a sample of civil psychiatric patients and criminal offenders. This research will assess participants’ level of hostile attributions using a new measure of hostile attributions, as well as other variables such as psychiatric symptoms, substance use, and criminal attitudes, to see how these relate to one another. Another purpose of her project is to look at the association between hostile attributions and behaviours such as violence, victimization, self-harm, and suicidal ideation and attempts. Exploring this research area to a greater degree could have far-reaching consequences in terms of decreasing the incidence of violence-related adverse outcomes in civil psychiatric patients and criminal offenders, thereby enhancing overall population health and reducing health care system costs. The results of Melissa’s research are expected to raise implications for reducing the risk of harmful behaviours in these individuals in terms of implementing new treatment and intervention programs.
Can intrapulmonary arteriovenous shunting explain exercise-induced arterial hypoxemia in women?
The cardio-respiratory system (heart and lungs) is efficient in maintaining oxygen and carbon dioxide levels in the blood most of the time. However, during very strenuous exercise, the cardio-respiratory system may become less efficient in maintaining equilibrium of these gases. Known as exercise-induced arterial hypoxemia (EIAH), this condition is characterized by a reduction in oxygen levels in the arterial blood, starving muscles of oxygen and impairing exercise capacity. In men, EIAH has been found to be prevalent mainly in highly-trained endurance athletes at near maximal exercise intensities. However, research has demonstrated that women who are not highly trained may experience EIAH, and at lower exercise intensities. This may be due to anatomical differences: women have smaller lungs, airways, and surface areas for gas exchange relative to men. One potential explanation for the EIAH phenomenon is through intrapulmonary arteriovenous shunting, where instead of taking its normal route through the lungs to gain oxygen, deoxygenated blood from the veins is diverted directly back into the heart. This results in lower oxygen levels in the arterial blood and less oxygen available for the working muscles. Research suggests that intrapulmonary arteriovenous shunting exists in healthy, exercising humans. Jill Kennedy is conducting the first systematic study of whether intrapulmonary arteriovenous shunting accounts for EIAH observed in women during exercise. She will also explore whether this relationship is influenced by fitness. Kennedy’s research will shed new light on female physiological responses to dynamic exercise with respect to the pulmonary system. Ultimately, this knowledge could lead to the establishment of scientifically-based, gender-specific exercise prescription guidelines for women throughout their life span.
BPD as a disorder of intersubjectivity: identity disturbances in borderline personality disorder
Borderline Personality Disorder (BPD) is a psychiatric condition marked by instability in interpersonal relationships, behaviour, mood and self-image. BPD is associated with high rates of suicide, self-harm, substance abuse and hospitalization, and comes at a significant cost to both individuals and society. One symptom of BPD is an inability to maintain a stable sense of identity, which is associated with distress and health risk behaviours. However, the specific types of identity problems, the factors that contribute to identity problems, and the effects of identity disturbance in BPD are unclear. In recent decades, it has been proposed that personal identity is related to life narratives, where a cohesive life story helps a person to maintain a stable sense of identity. Nathalie Lovasz is clarifying the specific identity problems experienced by persons with BPD. Using measures of identity disturbance, she is comparing people with and without BPD. She is also examining potential contributors to identity disturbance in BPD, focusing in particular on whether narrative coherence mediates or accounts for identity disturbance, and the relationship between identity disturbances and emotional states. This research could help clinicians zero in on the specific types of identity problems faced by people with BPD. This research could also lead to improved diagnosis, identifying components of the symptom that are most unique and important to BPD.
Neural connectivity and memory in schizophrenia patients and healthy controls
Schizophrenia is a brain disease that affects one per cent of Canadians — more than 300,000 people — causing hallucinations, disordered thought and memory dysfunction. Two specific types of memory are known to be affected in schizophrenia: working memory, or the ability to temporarily store and manipulate information (e.g. remembering a phone number until you can write it down); and source memory – the ability to recall where a memory, idea or piece of information came from (e.g. remembering that it was your sister who told you that Oslo is the capital of Norway). Paul Metzak is measuring brain activity during these two types of memory in both healthy volunteers and schizophrenia patients. His goal is to see how differences in activity in various areas of the brain can lead to selective memory impairments. He is using newly-developed statistical tools to look at how networks of brain areas interact to give rise to successful remembering. These tools also enable him to determine how the different components of successful remembering are affected in the schizophrenic brain – whether memory impairment arises from a failure in storing the memory properly, or from an inability to retrieve the correct item once it has already been stored. By identifying the dysfunctional components of brain activity that give rise to memory disorders in schizophrenia, Metzak’s research provides a vital first step on the road to improving memory problems. This work could lead to the development of strategies, therapies, and techniques that can minimize the impact of memory deficiencies in the day-to-day life of patients suffering from these impairments.
Temporal processing deficits in developmental dyslexia – a functional MRI study
Developmental dyslexia is defined as the difficulty in learning to read, and affects between 5 and 17.5 per cent of school-age children. The cause of dyslexia is unknown, but there may be a neurobiological basis. Current diagnostic tests for dyslexia are typically conducted by grade two or three, however by this time, the child already displays significant reading difficulties and may never catch up to their peers. Developing diagnostic tests to assess or predict reading difficulties at an earlier age could allow for earlier intervention and prevention of academic and social difficulties associated with dyslexia. For many children, the main problem in dyslexia involves sound (phonological) processing. For instance, the child may not be able to link sounds to letters, or break words up into their individual sounds. Also, people with dyslexia may show deficits in visual and auditory temporal processing, which is the perception and integration of rapidly presented stimuli. For example, the child may have difficulty with determining the direction of motion or sound. It is unknown whether there is a link between reading and temporal processing skills. Marita Partanen is examining whether reading and temporal processing use overlapping brain networks, and whether these brain areas are affected in children with dyslexia. She is using functional magnetic resonance imaging (fMRI) to track brain activation in children as they complete simple tasks. If a link between reading ability and temporal processing can be established, there is potential for simpler and earlier diagnostic tests for dyslexia that assess temporal processing. Ultimately, the ability to diagnose dyslexia at a younger age may lead to new programs that can improve academic and social outcomes for people with dyslexia.
Measuring confidence with wheelchair mobility
In 2000/01, approximately 264 000 Canadians required a wheelchair for mobility. Independence with mobility is important for day-to-day living, social activities, and overall quality of life. However, although wheelchair skills training has become much more prevalent in the past decade, more than half of Canadians using a wheelchair are not independent and require assistance with their mobility. One factor that has not yet been explored by research is the impact of confidence on a person’s mobility and independence. Confidence contributes to the acquisition of knowledge and refinement of new abilities. It also influences an individual’s choice of activities, motivational level, effort, resilience, life choices, and perseverance in the face of difficulties. Preliminary research suggests that confidence may affect wheelchair mobility, but there is currently no tool to assess or address this important factor. Paula Rushton is developing and validating an assessment tool to measure wheelchair skills confidence. The creation of this tool involves input from occupational therapists, physical therapists and physicians, as well as wheelchair users in the community. The second phase of her project will involve testing the tool with one hundred community dwelling wheelchair users. The creation and validation of this tool is an important first step in developing treatment strategies that could address low confidence with wheelchair mobility. Ultimately, this work could result in better mobility and independence for people who use wheelchairs, and a decreased burden on the health care system and on caregivers.
Motion perception deficits in children with amblyopia: a functional MRI investigation
Amblyopia – commonly known as “”lazy eye”” – is a developmental disorder that causes poor vision in one eye compared to the other eye. Amblyopia can arise from an inward or outward turn of the weaker eye. This prevents both eyes from working together to form one image and results in double vision. It can also arise when one eye has much better focus than the other eye. In both cases, as the brain matures it will begin to ignore the image coming from the weaker eye, eventually causing vision in that eye to deteriorate. Regardless of how amblyopia arises, the most common treatment is to place an eye patch over the good eye. This forces the maturing brain to start using the weaker eye, so that vision in this eye will “”catch up”” to the vision of the good eye. This form of treatment has been very effective in treating some cases of amblyopia, but not other cases. Currently, eye care professionals primarily use letter charts to assess how the ability to process form is affected in amblyopia. Research over the years has found that in addition to abnormalities in processing form, there are also abnormalities in motion processing. Typically, eye care professionals do not assessmotion perception, so any abnormalities in motion processing that may develop currently do not get treated. Using functional magnetic resonance imaging (fMRI), John Secen is looking at differences in brain activity between children with and without amblyopia as they perform a motion processing task. This research will improve upon the current understanding of the neural basis behind motion-processing deficits in amblyopia, and hopefully, this knowledge could lead to the development of new screening techniques so that these abnormalities in motion processing can be detected and treated.
Examining the link between cognitive deficits in the elderly and suboptimal activity of the locus coeruleus-norepinephrine system
A working brain produces electrical activity that can be recorded at the scalp. An event-related potential (ERP) is a characteristic electrophysiological response to any specific category of stimulus or event. The P300 is an ERP associated with stimuli that must be attended. It has been suggested that the P300 may be a manifestation of functioning in the locus coeruleus – norepinephrine system (LC-NE system), a neuromodulatory system that is associated with arousal , vigilance and attention. A link has been suggested between cognitive deficits in the elderly and suboptimal activity in the LC-NE system. Christopher Warren is attempting to demonstrate the link between the P300 and the LC-NE system, and describe the related changes in the brain that occur with age. He is assessing the performance of elderly participants on a specific attentional task, while simultaneously recording the electrophysiological activity of their brain using electroencephalograph recording equipment. The data will be compared with a control group of younger participants. Chris is looking for specific, key differences in electrophysiological activity and behavioural performance between elderly participants and controls, which will support the link between the LC-NE system and the P300, and will allow inference as to how the LC-NE system is behaving in the elderly participants.. Chris’s results will describe, and possibly implicate suboptimal function of the LC-NE system in cognitive decline with age. This research has direct implications for understanding the cognitive decline associated with healthy aging, potentially describing the function and malfunction of the LC-NE system in aging populations. It could also generate a model that could be applied to understanding LC-NE function in people with attention deficit/hyperactivity disorder, dementia, schizophrenia, or traumatic brain injury. A comprehensive theory of the LC-NE system could inform the development of clinical strategies and tools to help elderly citizens effectively work around attention-related cognitive deficits that occur with age