Clinical Research Unit for Eating Disorders, Clinical Psychology Unit
Professor Stephen Touyz was involved in the following research projects during 2000.
Development of an instrument to assess motivation for recovery in anorexia nervosa.This project was undertaken by Elizabeth Rieger, Stephen Touyz, David Schotte, Peter Beumont, Janice Russell, Simon Clarke, M Kohn and Ros Griffiths. The above study is aiming to develop an instrument to assess readiness to recover in anorexia nervosa based on Prochaska and DiClemente’s stages of change model (namely, the Anorexia Nervosa Stages of Change Questionnaire or ANSOCQ). The final sample will include 115 patients with anorexia nervosa from eight inpatient eating disorder units affiliated with the University of Sydney.
An initial analysis was carried out on data collected from 71 participants, with promising results obtained regarding the psychometric properties of the ANSOCQ. For example, the internal consistency coefficient for the scale was 0.90, while the test-retest reliability coefficient of the ANSOCQ over a one-week period was 0.89. Regarding concurrent validity, the correlations between the ANSOCQ and the four motivational scales of the URICA were significant, that is, -0.64 (p = .000) for the precontemplation scale, 0.66 (p = .000) for the contemplation scale, 0.72 (p = .000) for the action scale and 0.34 (p = .004) for the maintenance scale. Among the aspects of predictive validity investigated, scores obtained on the ANSOCQ correlated significantly with the amount of weight gained during the subsequent week (r = 0.40, p = .001), from weeks 1 to 4 of admission (r = 0.37, p = .002) and from weeks 4 to 8 of admission (r = 0.39, p = .008).
These preliminary results have been accepted for publication in the International Journal of Eating Disorders and have been presented at various conferences throughout 2000. The study was supported by a Research Fellowship from the New South Wales Institute of Psychiatry. Further manuscripts are being prepared for publication.
A comparison of group and individual cognitive-behavioural therapy for patients with bulimia nervosa. This project was undertaken by Eunice Chen, Stephen Touyz, Peter Beumont, Chris Fairburn, Ros Griffiths, Phyllis Butow, Jan Russell, David Schotte, Bob Gertler and Chris Basten in collaboration with Oxford University. The aim of this study is to develop Fairburn's individual CBT for BN into a group program and to compare both treatments in a randomised controlled fashion. 44 BN patients were referred by hospitals and GPs. Half were randomly assigned to Group CBT and the other half to Individual CBT. Both Individual and Group CBT followed Wilson, Fairburn and Agras, (1997). Fairburn reviewed and provided feedback on the group CBT manual. Group membership was closed and groups varied from 5-6 patients per group. Patients were assessed at pre-treatment and post-treatment with the Eating Disorder Exam (12th Edition) and self-report questionnaires examining weight and shape attitudes and general psychiatric symptomatology. Treatment sessions and EDE-12 assessments were audiotaped and 10% of each were validated by independent clinicians. Independent t-test and Chi-Squared tests found no differences between groups at pre-treatment assessment. 2 (Treatment modality) X 2 (Time) Repeated Measures ANOVAs of post-treatment data found a significant decrease in BN symptoms and general psychopathology for both treatments. No differences were found between Individual CBT and Group CBT on all the measures except for a treatment X time interaction for objective bingeing and vomiting. This suggests that Individual CBT may be more effective or act faster upon bingeing and vomiting than Group CBT. It also suggests that Group CBT is as effective as Individual CBT in dealing with the psychological attitudes and general psychopathology related to BN. This study was completed during 2000 and is being written up for publication. Eunice Chen was awarded a Post-Doctoral Fellowship at Yale University.
Eating disorders in pregnancy. This project was undertaken by Kate Baggs, Stephen Touyz, Sabina Kleitman, R. Gertler and A Korda. The present study investigated the prevalence of clinical eating disorders in a sample of 929 pregnant women aged between 16 and 40 years attending an ante-natal outpatient clinic. A two-stage screening survey methodology was employed using strict diagnostic criteria. At the initial screening phase participants were asked to complete standardised and reliable questionnaires concerning body image (Body Shape Questionnaire; BSQ; Cooper, Taylor, Cooper & Fairburn, 1987 and the Figure Rating Scale; FRS; Stunkard, Sorensen and Schulsinger, 1983) and eating disorder pathology (a self-report derived from the Eating Disorders Component of the Composite International Diagnostic Interview, 1993; CIDI; The Eating Disorders Examination, Self Report Questionnaire Version; EDEQ; Fairburn and Beglin, 1994). The second stage involved a semi structured interview based on the CIDI. Results indicated that the life-time prevalence rate is consistent with rates found in other community studies. In the current study the life-time prevalence rate for Anorexia Nervosa was estimated to be 1.2% and for Bulimia Nervosa it was 2.0%. Only one case was identified during pregnancy making the point prevalence rate 0.1%. This evidence suggests that women, on the whole do not engage in dysfunctional eating behaviours during pregnancy, and even if they fulfilled diagnostic criteria for eating disorder pathology at some stage in their life they tended to cease these behaviours before or during pregnancy.
Cross-culture research on anorexia nervosa: Assumptions regarding the role of body weight. This project was undertaken by Elizabeth Rieger, Stephen Touyz and Peter Beumont. The above study entailed a theoretical and empirical investigation of cross-cultural issues in anorexia nervosa. Contrary to widely held assumptions in current cross-cultural research on anorexia nervosa, it was argued that: (i) weight concern defined as weight loss which is positively valued by the individual (rather than defined as a fat phobia) is a defining characteristic of anorexia nervosa and is not limited to contemporary, Western cases of the disorder; and that (ii) the occurrence of anorexia nervosa in non-Western contexts cannot be solely attributed to the acceptance of Western thinness ideals since values and practices intrinsic to non-Western cultures are also likely to be aetiologically relevant. The paper has been accepted for publication in the International Journal of Eating Disorders.
Nutritional counselling in the treatment of bulimia nervosa: A combination of pharmacotherapy and nutritional management. This study was undertaken by Peter Talbot, Stephen Touyz, Peter Beumont, Janice Russell, Cathy Buckley, Kitty Lowinger and Gordon Johnson. The aim of this study was to determine whether nutritional counselling was associated with an improvement in bulimic symptomatelogy, whether this improvement was maintained during post-treatment follow-up and whether the addition of fluoxetine 3 x 20 mg/day confers additional benefit. This research has now been completed and is being written up for publication.
Energy wasting in anorexia nervosa. This study was undertaken by Janice Russell, Louise Baur, Peter Beumont, Suzanne Byrnes, Gaby Gross, Stephen Touyz, Suzanne Abraham and Stephen Sipfel. Optimal nutritional rehabilitation of anorexia nervosa requires more information concerning actual energy and substrate requirements. To this end, indirect calorimetry was performed in female patients (N = 34, age 20.9 + 1.2 yr, body mass index (BMI 15.6 + 0.2 kg/m2; mean + SEM) soon after commencement of refeeding and at the time of discharge from hospital (N = 18, BMI 19.0 + 0/3 kg/m2). Healthy female control (N = 18, age 24.6 + 1.3 yr, BMI 21.6 + 0.6 kg/m2) were also tested. Resting energy expenditure (REE) and respiratory quotient (RQ) were measured in the fasting state, followed by diet-induced thermogenesis (DIT) and RQ over a 4 h period following a 100 g oral glucose load. Compared with post-refeeding patients and controls, pre-refeeding patients had a high basal RQ and a low REE, with a paradoxically higher DIT (13.2 + 0.9% of REE vs 8.3 + 1.2% and 8.6 + 0.9% in post-refeeding patients and controls, respectively). RQ values in pre-refeeding patients exceeded unity following the glucose load, probably reflecting net lipogenesis, whereas in the post-refeeding patients, post-glucose RQ was similar to that of controls, suggesting premature curtailment of lipogenesis. These data demonstrate energy wasting in emaciated patients with anorexia nervosa. Biological repair processes could account for disproportionate energy loss early in refeeding and there may be some later impediment to full restoration of fat stores.
Relative effects of cognitive and behavioural components in group CBT for bulimia nervosa. This study was undertaken by Adele Hamilton, Stephen Touyz and Donald Byrne. CBT is recognised as an effective individual and group treatment for bulimia nervosa. The aim of this study was to identify those components of CBT which contributed most to treatment effectiveness.
Seventy-four patients with BN were allocated to one of three treatment groups receiving either conventional CBT, a dismantled version focussing on cognitive components (CT) or another dismounted version focussing on behavioural components (BT). They were compared with a wait-list control. At the 12-month follow-up the CBT group had a significantly lower frequency of bingeing, subjective loss of control, duration of binge episode and perceived fullness after a binge than the other two treatment groups. This work has now been completed and has been submitted for publication.
Assessment and treatment of anorexia nervosa. This study will be undertaken by Peta Hartman (who is completing a PhD at Griffiths University) with Paula Barrett and Stephen Touyz. This study is designed to develop an assessment and treatment protocol relevant to Anorexia Nervosa (AN). The American Psychiatric Association (APA; 1993) in developing practice guidelines for the treatment of eating disorders, identified several areas for future research. These areas included the need for better treatment and outcome studies specifically in relation to: addressing the biological, psychological and social predictors of developmental needs in children and adolescents and methods to facilitate early recognition of eating disorders. Two major studies are proposed. Cognitive biases hypothesised in the cognitive models of AN will be investigated using an information processing task. A volunteer sample of 40 adolescents aged 10-16 years with a DSM-IV diagnosis of AN will participate. To examine parental influence, a problem solving discussion will be completed by the adolescent and their family, the family then being requested to generate a practical and operable solution to the behavioural indicators of AN. Independent observers will rate the interaction on several dimensions including; support, effort, teamwork and solution practicality. Study two will be a treatment program for AN sufferers and their families. After assessment, sufferers will be allocated to one of three conditions: a 12 week treatment phase (using Cognitive Behavioural Therapy); a comparison intervention; or a wait list. Assessment will be made prior to treatment, post treatment and at three, six, and 12 month follow up.
The relationship between self-pathology and eating disorders. This project was undertaken by Chris Basten, Russell Meares and Stephen Touyz. The aims of this study are to 1) develop a new self-report questionnaire that assesses a person’s sense of identity or self 2) to evaluate the psychometric properties of this questionnaire 3) to examine the role of sense of self in patients with disordered eating.
Dr. Deborah Erickson's research continued on:
a) developing a Quality of Life scale for people with Myopia which integrates personality characteristics now has over 300 patients assessed and the statistical analysis is in progress.
b) Research on the cognitive processes of children and adolescents diagnosed as AD/HD and prescribed stimulant medication is in its final stages with 30 participants assessed pre-and post medication for any changes related to the medication in attention, planning, organisation and general cognitive processing strategies ($11,000 URG).
c) Research continues in Melbourne on developing a compliance scale for contact lens wear and maintenance of the lens. This scale will be used to assist practitioners in developing the appropriate educational intervention methods for patients who are non-compliant and prone to infections etc. related to mishandling of the of the lenses.
d) Research has been completed on the personality characteristics of patients wearing monovision lenses. One publication has been accepted in Perceptual Motor Skills and another publication is in process.
e). Research is just beginning on developing a quality of life scale for children with AD/HD. ($19,000 sesqui scheme grant).
1). Erickson, D.B. Stapleton, F. Giankoupolis, E & Erickson P. (in process) Quality of Life Scale for Patients with Myopia.
2). Erickson D.B. Stapleton, F., Erickson P., Holden B.A. (in process). Psychological variables affect self-reporting on a dry eye questionnaire.
3). Erickson D.B. Stapleton, F., Erickson P. (in process) Personality Influences Patient reporting of Dry Eye Symptoms.
4). Coles, C. Erickson D.B. & Brennan, N (in process). The effect of personality in the compliance of contact Lens Wear.
5). Erickson D.B. & Dutoit, R. N, (in process). Personality Correlates in Monovision Lens Wear.
6). Lang, M. & Erickson D.B. (in process). Cognitive processing gains after computer-based instruction of learning disabled youth.
7). Williams, M, Erickson D.B. Kohn, M & Clark, S (in process) Cognitive Processing Differences between children with different subtypes of attention deficit disorder.
8). Erickson D.B. Lang, M. Kohn, M. & Clark S. (in process). Cognitive Processing differences in Children before and after prescription medication.
Dr Caroline Hunt's main focus of research is the nature of Generalized Anxiety Disorder (GAD). An investigation into the role of thought suppression in GAD - a possible mechanism for the perceived uncontrollability of worry in these patients - has been completed in collaboration with Dr Rocco Crino (Director of the Anxiety Disorders Clinic, St. Vincent's Hospital), and Clinical Masters student Mr Peter Cowell. Data from a sample of patients with anxiety disorders is being analysed to assess the relationship between stress, anxiety, depression and worry and this work is being undertaken in collaboration with Associate Professor Peter Lovibond, School of Psychology, UNSW. Further investigations in collaboration with Dr Crino into the phenomenon of worry in anxiety disorders include an analysis of the specificity of worry to GAD using the Penn State Worry Questionnaire, and an investigation of the contribution of the construct of 'intolerance of uncertainty' to the cognitive behavioural model of GAD.
As a member of the WHO consortium to analyse the National Survey of Mental Health and Well Being, I am investigating the prevalence, disability and associated epidemiological factors in Generalized Anxiety Disorder. The Commonwealth's Mental Health Branch is funding the analysis of data from the survey to answer the following questions: How many people have mental disorders in Australia, how disabled are they by them, and what health services do they use? Further research into the factors that influence individual's decisions to seek treatment for their anxiety or depressive disorders is planned in collaboration with Ms Cathy Issakidis (Clinical Research Unit for Anxiety Disorder) and Clinical Masters student, Ms Anna Thompson. Additional collaborative projects in progress include early intervention in preventing post-natal depression (with Dr Marie-Paule Austin, POW Hospital and Mr John Kearney, Clinical Masters student) and a preparation programme for post-traumatic stress disorder (Ms Leanne Humphreys, Wesley Hospital and Ms Kathy Rooney, Clinical Masters student)
An NH&MRC funded project that aims to evaluate a school-based programme to prevent anxiety and depressive disorders is under way across 20 Catholic secondary schools in Sydney. A pilot study that will investigate factors influencing the incidence of bullying in schools has been funded for 2001.
• Perception Laboratories
Dr John Predebon commenced and continued research on:
Timing, including the effect of motion-direction changes on retrospective duration judgments. The results suggest an intriguing relationship between the 'psychological present' and the effectiveness of stimulus changes in influencing remembered duration.
Visual attention, specifically its role in modulating the magnitude of visual illusions and in mediating the phenomenon of illusion decrement.
The laboratory acquired an eye movement recording system which is being used by a doctoral student (Elaine Cornell) to measure the accuracy of vergence in naturalistic settings.
The Vision Sciences Lab
In 2000 Dr Rick van der Zwan continued research on symmetry perception mechanisms in the visual cortex. This work was achieved by collaboration with Professor David Badcock of the University of Western Australia. The work on internal clocks, by William Landers has progressed with some interesting data being gathered on the Ternus effect threshold. William found some interesting visual/auditory interactions and is designing and programming series of experiments to elucidate the mechanisms giving rise to those effects. Timothy Ikin, a PhD student, in collaboration with Associate Professor Mike Thompson of the School of Biological Sciences, is investigating the visually guided behaviour of the dragon lizard Ctenophorusnuchalis. Once we have some measures of their normal visual capacities we will investigate the mechanisms for plasticity within the optic tectum these animals seem to possess. Our first year on this project was successful in that we demonstrated C. nuchalis could be trained to run a Y-maze in a 2AFC in order to complete a 2AFC task. Anna Brooks continued a systematic investigation of the perceptual correlates of skin cancer identification by naïve observers (ie. non-medically trained personnel). Several earlier studies have indicated that discriminating between normal moles and moles that represent a skin cancer danger is difficult, yet it is an ability which can be learned. We have undertaken the first systematic investigation of how such learning might occur and the cues that could be used. Our first publication in this area was submitted in 2000 and several others will follow in 2001.
• Vestibular Research Laboratory
Professor Ian Curthoys was involved in the following research projects during 2000.
Vestibular research using guinea pigs. (DPD Gilchrist, IS Curthoys, J Kim, N Vibert (CNRS, Paris) et al).
The year 2000 saw the start of a new NHMRC project grant entitled "Experimental validation of a clinical indicator of utricular function". The aim of this project is to use guinea pig to investigate the physiology that underlies the behavioural responses to galvanic vestibular stimulation. It is possible that galvanic vestibular stimulation in human is a test of otolith function. The work directly complements ongoing human research that is also conducted in our laboratory. The current project involves a combination of behavioural and electrophysiological techniques.
Guinea-pig Behavioural Work. (DPD Gilchrist, IS Curthoys, J Kim)
The main focus of the behavioural work has been to measure the eye movement response to galvanic stimulation in restrained alert guinea pigs. At present all data have been collected from normal guinea pigs and a paper is currently in preparation detailing the exact characteristics of the 3-D eye movement response.
In addition to the eye movements, we are also interested in the postural response to galvanic vestibular stimulation. We have recently begun to examine postural responses in unrestrained guinea pigs using the postural measurement system Optotrak (TM). This has required the design and production of a small lightweight head-mounted device which can deliver the constant-current galvanic stimulation, and which contains small LEDS to measure the position of the head in space. It has been necessary to ensure that the apparatus is comfortable for the animal to wear and does not prevent natural movement. This part of the project is at a preliminary stage but the results already look very promising.
Another aspect of the behavioural work is to measure the guinea-pig eye-movement response to galvanic stimulation during a pitch or tilt of the animal. Whilst we already had a device for performing this type of experiment, Warren Davies (Technical Officer) was commissioned to build a larger unit to tilt and pitch guinea pigs, and allow the placement of additional electronics to measure binocular eye movements and head movements simultaneously. This will become operational in early 2001.
Electrophysiology. (D Gilchrist, I Curthoys, J Kim, T Murofushi)
Our electrophysiological experiments directly complement the behavioural work and the aim is to make extracellular recordings from single primary vestibular afferents to test which vestibular sensory regions are activated by galvanic stimulation. Excellent progress was made during 2000. The electrophysiological work began in June of 2000 and we were fortunate to have the assistance of Assoc. Prof. Toshi Murofushi from Japan for 1 month. We currently have recordings from some 200-300 neurons.
During the development of this part of the study a number of improvements in experimental methods have been made. At the beginning of 2000 we changed our procedures for anaesthetizing animals. Instead of injectable anaesthetic we moved to the use of the volatile anaesthetic halothane. We found that halothane provided excellent anaesthesia but also severely reduced the neural responses we were interested in measuring. We have subsequently returned to the use of injectable anaesthetic which has also improved the success of each experiment. In addition, to improve stability of the recording apparatus, a new purpose-built recording set-up was built and became operational in August 2000. Prof. I. S. Curthoys has continued to upgrade and improve the electronics for this experiment to produce a very low-noise recording system.
Response of human posture to galvanic stimulation. (P-P Vidal, H MacDougall, I Curthoys, D Gilchrist)
During November 2000 we were fortunate to have the company of Dr Pierre-Paul Vidal from CNRS in Paris, France. We have a strong collaboration with this group and during his two-week stay a number of experiments were conducted to look at the response of human posture to galvanic vestibular stimulation. The guinea-pig work we have been conducting has direct implications for the types of responses we were observing in humans.
Guinea-pig hippocampal stimulation. (S Hicks, I Curthoys, D Gilchrist)
Many of the procedures that we use for recording neural responses to galvanic stimulation have also proved useful for investigating the response of the hippocampal formation to electrical stimulation of the vestibular system.
Evidence for vestibular and optokinetic input to the hippocampus: evoked potentials and theta. (S Hicks; D Gilchrist; P Cuthbert; I Curthoys)
Since it is likely that the hippocampus (HPC) relies on vestibular information for efficient spatial navigation and path integration, we have conducted a series of behavioural and electrophysiological studies investigating the potential contribution of the vestibular and optokinetic (OK) systems to HPC function. Passively rotated, awake, restrained guinea pigs displayed HPC theta activity from chronic depth electrodes, depending on the characteristics of our rotational stimuli. Theta was significantly enhanced in light over darkness, demonstrating a strong optokinetic component. The visual component was demonstrated in stationary animals during purely OK stimulation. Theta activity was strongest at higher OK drum velocities and higher nystagmus rates. Theta-related waves were consistently generated during quick phase eye movements. In acute anaesthetised guinea pigs, electrical pulse-train stimulation of afferents from all the vestibular sensory regions evoked long latency (50ms) potentials in rostral CA1 and dentate gyrus, but not in surrounding regions (dorsal thalamus, caudate, corpus callosum).
Potentials were generated even when the stimuli were insufficient to produce detectable eye movements. Following the evoked potential there was an ultra long wave-like response of 4-5 Hz, suggestive of theta. These data demonstrate that both optokinetic and vestibular information influence hippocampal activity. Integration of these two sources of information, vital for efficient navigation and path integration, may be the result of a HPC response generated by sensory stimulation alone and not contingent on alertness or arousal.
Effects of galvanic vestibular stimulation (GVS) in the guinea pig. (IS Curthoys, J Kim, DPD Gilchrist).
Low intensity galvanic currents passed through the mastoid bones (behind the ear) generates torsional eye movements in humans (Watson et al., 1998, Exp. Brain Res., 122, 453). Many human studies have observed postural activation during surface GVS applied through the mastoids (e.g. Krizkova & Hlavacka, 1994, Physiological Research 43, 187). In continuing research, we have undertaken a series of experiments in guinea pigs using chronically implanted electrodes to deliver GVS. In addition to ocular responses, we have recently recorded postural activation in the guinea pig during GVS. In order to complement this behavioural aspect of our investigation, we have also observed the activity of single neuron responses to GVS.
Eye movements in response to rapid linear head accelerations. (AM Burgess, IS Curthoys, HG MacDougall, RA Black (Institute of Clinical Neurosciences, RPA))
We have been testing our head-sled apparatus with the aim of devising a new clinical test for otolith dysfunction. The apparatus consists of a linear slide to which a bite-bar may be attached. When the head is accelerated, the slide forces the head movements to be linear rather than a combination of linear and angular motion.
The stimuli may be active (subject-driven) or passive (machine-driven). A computer program, written in LabVIEW by H. MacDougall, can generate a waveform which is passed on to an amplifier and thence to two actuators on either side of the linear slide. This method delivers very rapid accelerations (for example, increasing from 0 m/s^2 to around 5 m/s^2 in about 5 milliseconds) and small displacements of a few millimeters.
During the experiment the subject's horizontal eye position is measured using a low-noise infrared detector, mounted on spectacle frames. Head acceleration is measured with linear accelerometers on the linear slide and on the spectacle frames. For some tests we also attached an accelerometer to a mouth guard made from a dental impression of the subject's mouth. Our measurements show a delay of about 2 ms between the onset of the sled movement and the onset of the spectacle movement; as would be expected, the onset of the mouth-guard movement is in between the two other onsets.
Our work so far has been concerned with eliminating any artifacts due to movement of the detector and/or the spectacle frames. Using elastic to fasten the spectacles tightly to the head greatly decreased some artifacts. We have performed tests using the Optotrak system to compare the displacements of the head-sled, spectacle frames and detector during the stimulus. Setting the detector in araldite, and gluing the detector to the magnet used to attach it to the spectacles, reduced the measured displacements by about half. We also plan to measure eye movements with magnetic search coils so as to verify our infrared measurements. Further artifact removal may require modification of the spectacles, a lower acceleration, and possibly a smoother acceleration onset. Once this is done, it should be straightforward to test large numbers of subjects in a variety of conditions.
Surfaces of the utricular and saccular maculae. (IS Curthoys, AM Burgess, HG MacDougall, A Kondrachuk).
We have anatomical data measured by Ian Curthoys for surfaces of the utricular and saccular maculae of several guinea pigs. We have written software to calculate the surface normals and the displacement of each point to the nearest point on the striola. Having done this, the program then calculates the activation of the macula when exposed to a force vector of an arbitrary direction.
We wish to use these patterns of activation to model the response of the otoliths to linear forces, and plan to use the eye-movement results of Hess & Dieringer (1991, J. Neurophysiol., 66, 1805) in combination with our anatomical data to make a coherent model of the direction of eye movements as a function of activation of locations on the macula.
Eye torsion and the perception of spatial orientation. (IS Curthoys, N Wade (Dundee University), HG MacDougall, AM Burgess).
When roll-tilted in darkness, a normal subject will make a setting of perceived tilt which usually differs considerably from the actual tilt. The subject's eyes also undergo torsion, known as counter-rolling. We wish to determine how much of a subject's perceived tilt is due to counter-rolling, by making simultaneous measures of eye torsion and perceived tilt. Eye torsion is measured using the VTM (Video Torsion Measurement) system, and the subject records perceived tilt by setting a bar of light to the perceived head median plane. The video screen is darkened momentarily when the subject makes a setting, thus allowing us to synchronise the perception and eye-movement data.
The subjects tested so far have widely varying different perception settings. For one subject during part of the test while seated upright, the setting of the head median plane was almost exactly the same as the eye torsion. For other parts of the experiment the relationship was more complex. We plan to do a more systematic study of a larger number of subjects, and to measure neck vibration while the subject is tilted. An Honours student, Mr Daniel Ooi, will be continuing the project in 2001.
Generation of the quick phase. (DPD Gilchrist, A Cartwright, IS Curthoys, AM Burgess)
During active or passive head movements, there are two main types of eye movement: the slow phase, in opposite direction to the head movement, and the quick phase, in the same direction as the head movement. The quick phase allows rapid repositioning of the eye in the orbit so that the eye is not driven to the edge of its rotational range.
As part of Andrew Cartwright's PhD project, guinea-pig eye movements were measured in response to sinusoidal angular accelerations. Our recent work with these data has focused on trying to find a threshold for generation of the quick-phase. For high-frequency sinusoids (2 Hz), we found that quick phase begins when the eye has moved about 12 degrees from the central position.
On the other hand, our low-frequency sinusoidal data (0.1 to 0.6 Hz) did not show any such clear trends. P-P Vidal (CNRS, Paris) speculated that at lower frequencies the data may be affected because for lower head velocities the animal has time to make several fixations during each cycle. We are therefore looking at present for a relation between the slow-phase durations and the frequency of the stimulus.
To explain our low-frequency data, we have decided that that trapezoidal impulses at a variety of accelerations and velocities would not only be a useful adjunct to sinusoids, but will probably be better for studying the quick phase. We therefore plan to obtain new trapezoidal data and examine archival human eye-movement data from the centrifuge at Royal Prince Alfred Hospital.
Response of the human neck to linear acceleration. (N Vibert (CNRS), I Curthoys, D Gilchrist, P-P Vidal (CNRS), et al).
In previous years we performed experiments in which human subjects were accelerated abruptly on our linear sled, and the head and body movements were measured using our Optotrak system. The results showed that some subjects consistently move rigidly when subjected to acceleration, whereas for other `floppy' subjects the head accelerates with respect to the body.
N. Vibert (CNRS, Paris) continued this project in 2000, by collecting data for a large number of normal subjects. He showed that there is some relation between the stiffness or floppiness of a subject's head movement and their field-dependence as measured by the rod-and-frame test and the embedded-figures test.
The accuracy of human vergence eye movements. (Elaine Cornell)
The aim of this study is to assess the accuracy of binocular function in subjects with normal binocular vision and to determine whether this accuracy is affected by the rate of change of fixation, the size of vergence change and the symmetry of vergence change. Many previous studies on the accuracy of binocular alignment have used a subjective method known as `fixation disparity' which involves careful observation and alignment by the subject of discrete targets induced under highly controlled conditions by haploscopic devices. Such studies usually indicate that errors of alignment are very small, usually no greater than 20 minutes of arc.
Other studies, which use objective methods, usually report larger errors of alignment. However, most of these also use highly artificial visual environments and/or unusual targets, such as random dot stereograms. The few studies which assess vergence accuracy under normal conditions confirm that significant errors of up to 3 degrees can occur, without diplopia. This finding therefore blurs the distinction between clinical normality and abnormality, and suggests that highly accurate alignment is not always necessary to produce symptom free binocular vision. The potential significance therefore, of our study, is to determine the extent of inaccurate alignment, without diplopia, that can occur under relatively normal conditions, and to identify whether such misalignments are influenced by the rate of change of fixation, the amount of vergence and the symmetry of vergence required.
A computer based eye movement detection and recording system (VidEyeO) developed in the Vestibular Research Laboratory of the Department of Psychology is being used. This device detects and records the centre of mass of each pupil. Additional software enables subsequent analyses of the recordings to determine the total vergence of the eyes and therefore subsequent under or over convergence (fixation error).
Binocular recordings are made under conditions that differ in terms of the rate of change of fixation (0.5Hz, 1Hz, 2Hz), angle of vergence change (5, 10, 15 degrees) and symmetry of vergence change (symmetrical/asymmetrical). Any variation of the position of one eye during binocular recording compared with its position during monocular calibration is recorded as a fixation. Errors both of vergence and lateral position can then be determined.
Chronic Vestibular Insufficiency - A Health Psychology Perspective. (D Erickson, GM Halmagyi, I Curthoys, A Bowman)
This research aims to address the mystery of why only a small minority of patients following development of the acute condition known as vestibular neuritis, report ongoing balance disturbance and adjustment difficulties; using a clinical health psychological perspective. In doing so, it aims to complement the ongoing investigations into possible psychophysiological explanations of chronic vestibular insufficiency, where as yet, no differences between well and poorly compensated patients have been found.
Over the course of 2000, an assessment battery of questionnaires and perceptual tasks was developed to use in assessing patients' adjustment to vestibular dysfunction. This involved both researching the most suitable and reliable measures of the various traits being investigated, and adapting some pre-existing questionnaires to be more encompassing for the target research population. The questionnaires aim to assess factors such as somatic amplification and hypochondriacal tendencies, and various personality traits, as well as to assess the patient's perceived quality-of-life and detect ongoing vestibular insufficiency. The perceptual tasks include the Embedded Figures task, and a portable computerised version of the Rod-and-Frame and Rod-and-Disc tests. An open-ended interview protocol was also developed to use for qualitative research, assessing the patient's illness cognitions and explore for possible psychopathology.
The assessment battery was tested with 1st-year students to practise administration techniques and determine the suitability of the methods used. Mature-age students were also recruited and tested to act as age-matched healthy controls. Pilot testing was commenced towards the end of the year with several patients with a variety of vestibular conditions, and amendments to the procedures and materials used were made accordingly. This included selecting a different vestibular condition to use as our sample, than was originally planned. Refining of the procedure and design is basically completed and the main recruitment and data collection stage is ready to commence early 2001.
Development and Application of Video Eye Movement Analysis Techniques. (HG MacDougall, IS Curthoys).
There is a strong trend towards computerized video eye movement analysis (video) both for primary research and for clinical assessment and diagnosis. Video has many advantages over more traditional eye movement analysis systems such as scleral search coils, differential infrared reflection, EOG and simple Frenzel viewing. Video is much more affordable, portable, noninvasive, stable and user-friendly than many of its alternatives, but its transfer from the research to the clinical environment is less than trivial. This project aims to develop video eye-movement analysis techniques by and for application to primary research and clinical testing.
Our video eye-movement measurement system (VTM: Video Torsion Measurement) has been developed over some years from strong theoretical principles established by Steven Moore and Ian Curthoys. H. MacDougall has embedded these principles in a functional system, which has many advantages over other commercially available systems.
We now have two binocular systems for horizontal, vertical and torsion, one binocular system for horizontal, vertical and vergence (synchronized), and three monocular systems for horizontal and vertical, used for perception studies. Sampling rates as high as video frame rate (50/60 Hz for horizontal and vertical; 25/30 Hz for torsion) allow analysis of dynamic eye movements such as the velocity of the slow phases of nystagmus.
VTM can be used either off-line from video recordings, or on-line to calculate eye position in real time, allowing interactive control of eye movement analysis and much more intuitive system operation.
Our video system development has now stabilized in a functional form friendly enough for use by several scientists at the University of Sydney. We plan to improve VTM with advances in hardware speed and with more robust algorithms such as partial ellipse fits to occluded pupils, and to apply the system to research and clinical investigations.
So far we have applied VTM to a broad range of research and clinical projects, including:
The comparison of ocular torsional responses to centrifugation and static tilt conditions with matched interaural acceleration to detect a saccular contribution.
Decompensation of the eye-movement control of unilateral deafferented subjects while stimulated by vibration delivered to the neck.
Assessment of the implications and clinical applications of nystagmic and torsional offset eye movements during galvanic stimulation of the vestibular system.
Correlation of perceptual measures, such as the biased settings of a horizontal bar, and torsional eye position offsets.
Investigation of torsional eye movements during on-centre rotation.
Analysis of horizontal, vertical and torsional slow-phase eye velocities during nystagmus generated by galvanic, rotation and optokinetic stimuli.
Understanding the effects of confounds which exist but are not measured by more basic eye-movement analysis systems. These confounds include those from suppression by fixation targets, blinking, pupil dilation, convergence, and gaze direction.
Interaction of maintained galvanic vestibular stimulation and linear acceleration. (HG MacDougall, I Curthoys, GM Halmagyi (RPA)).
We investigated the effect of maintained, constant-current, bitemporal, bipolar galvanic vestibular stimulation (GVS) as part of our ongoing search for clinically useful tests of vestibular and specifically otolith function. The eye-movement response to GVS was assessed and compared with responses to stimuli such as static roll-tilt, centred rotation and centrifugation. These tests were performed on six normal subjects, and on a patient with the CHARGE association, which includes absence of the utricular macula and semicircular canals.
The horizontal and torsional eye-movement response to GVS showed two components: some initial decay with a time constant of about 100s, and a longer-term maintained response. These components may be the result of stimulating two sensory systems: the canals (transient response) and otoliths (maintained response). This is consistent with the character of the CHARGE patient's response, as only the maintained response was present, presumably from stimulation of the saccular macula, their only vestibular organ. Although within-subject repeatability is high, the large between-subject variability may limit the usefulness of GVS as a clinical test.
Cognitive Neuroscience Unit
Dr Lea Williams is Head of the Cognitive Neuroscience Unit located within The Brain Dynamics Centre at Westmead Hospital. The psychophysiology laboratory within the Psychology Department is also part of this Unit. In 2000, 8 PhD students, 3 Clinical Masters and 7 fourth year research students from Psychology conducted their projects within the Cognitive Neuroscience Unit. We also have a strong collaboration with researchers at the Institute of Psychiatry, London. The Cognitive Neuroscience Unit brings a psychology focus to the integrative neuroscience approach of The Brain Dynamics Centre. This Centre comprises a large multidisciplinary team of researchers from psychology, psychiatry, mathematics, physics and medical backgrounds and includes a group of clinicians (from psychiatry, adolescent medicine, head injury) that head up the clinical applications of our research. A primary research theme of the Cognitive Neuroscience Unit is "Imaging our Emotions". We take an integrated approach to examining human emotional responses and dysfunctions and the associated cognitive processes, such as orienting and selective attention. Three complementary approaches are followed in the Unit:
1. Theoretical integration: Linking biological and cognitive models of the human brain (particularly emotion models),
2. Empirical data integration: Collection of data from complementary human brain imaging techniques (including eyemovement, arousal, EEG/ERP and functional MRI recording), and
3. Application to clinical disorders: The integrated theoretical and empirical approaches are applied to investigation of several psychological disorders, including schizophrenia, ADHD, PTSD and Borderline Personality).
In 2000, the research outcomes from the Unit included 15 refereed publications and three large competitive research grants. Further details are available on the web, by following the links from the Psychology homepage to The Brain Dynamics Centre. In affiliation with her role as Head of the Unit, Lea Williams is fMRI research coordinator for Westmead Hospital, Convenor of the Neuroimaging Panel of the NSW Institute of Schizophrenia and Allied Disorders and NSW representative on the NHMRC Consortium for Human Brain Research into Mental Disorders.
Associate Professor David Grayson undertook the following research in 2000:
1) Misunderstandings in psychology about quantitative methods,
2) Identification in MTMM (multitrait-multimethod) designs,
3) Ordinal “information” in psychometric tests,
4) History of regression in statistics and psychology,
5) Invariance in factor analysis.