of mixed axonal/demyelinating type. MRI of the brain showed pos-terior predominantly subcortical white matter hyperintensities onT2 and FLAIR images. The patient was treated with steroids,intravenous gammaglobulin and antibiotics. The patient made anuneventful recovery over 3 weeks. There are a handful of previouscase reports in which cerebral lesions have been seen in acuteGBS, one of whom was also found to have Mycoplasma. Thequestion arises as to whether these cerebral changes represent asso-ciated central demyelination due to common antigen or cross-reac-tivity, or whether a second para-infectious phenomenon hasoccurred.

doi:10.1016/j.jocn.2009.07.078

54. What is the effect of multiple sclerosis on employment?

Clarke Glynnis 1, Anderson Tim 1, Pearson John 2, Mason Deborah 3,Taylor Bruce 4

1 Department of Medicine, University of Otago, Christchurch, NewZealand2 Department of Public Health, University of Otago, Christchurch, NewZealand3 Department of Neurology, Christchurch Hospital, Christchurch, NewZealand4 Menzies Research Institute, University of Tasmania, Hobart, Australia

Introduction: Multiple sclerosis (MS) is the most common dis-abling neurological disease of young adults in Europe and NorthAmerica. It has an extremely variable clinical course which may re-sult in people living for many years with varying levels of disability.In 2006 a national prevalence study of multiple sclerosis wasconducted in New Zealand to determine the extent, distributionand impact of the disease on patients in this country.

Objective: To determine the impact multiple sclerosis has on anumber of socio-economic factors including employment status.This study was run to coincide with the New Zealand census 2006,enabling comparison with the total New Zealand population.

Methods: A cross-sectional study was conducted utilizingmultiple sources of notification, including MS society and hospitaldatabases, direct advertising and private practice records. A ques-tionnaire was sent to each person in New Zealand with MS. Theinformation collected included general demographics and data oneducation, work and income status.

Results: 2055 people responded to the survey (71% responserate). In March 2006 the labour force participation rate in NewZealand was 68.1%, whereas the rate for people with MS was 37%(p < 0.0001). The results show that 58% of respondents were not cur-rently employed, with 63% stating that their employment status hadchanged due to their MS. The median personal income for respon-dents aged 15 years and over with MS was $20,000, whereas themedian personal income for the New Zealand population on censusnight was $24,400. However 50% of respondents had a tertiaryqualification as compared with 40% of the New Zealand population.All age groups over 30 years with MS earned less than their NewZealand peers until they reached 70 years and over where therewas a leveling out of income which can be attributed to universalaccess to the New Zealand Government Superannuation.

Conclusions: These results show that multiple sclerosis is a dis-ease which has a significant impact on people’s ability to participatein the workforce. The early adult onset and chronic progressivenature of the disease compounds the effect, decreasing the person’sability to earn over time as compared with their peers in NewZealand.

Supported by: New Zealand HRC partnership funding grant withthe National MS Society of New Zealand.

doi:10.1016/j.jocn.2009.07.079

55. Neural networks involved in the control of skilled movement:correlated spike activity in the primary motor area of the cerebralcortex

Ghosh Soumya 1,2, Putrino David 1,2, Mastaglia Frank L 1

1 Centre for Neuromuscular & Neurological Disorders, University ofWestern Australia, QEII Medical Centre, Nedlands, WA 60092 School of Physiotherapy, Curtin University of Technology, Bentley, WA6102, Australia

Introduction: The motor areas of the cerebral cortex are impor-tant for the performance of skilled voluntary movement, and injuryto these areas is frequently associated with loss of motor skill. Tem-porally correlated (synchronized) neural activity has been proposedto play a role in cooperative action of motor cortex neurons, and mo-tor coordination. In order to study neural codes associated withcoordination of skilled reaching movements, we examined task re-lated and correlated spike activity of neurons in the primary motorcortex (MI) of cats.

Materials & Methods: The experiments were approved by theAnimal Ethics Committee of the University of Western Australia,and the National Health and Medical Research Council of Australia(NH& MRC) guidelines for the use of animals in experiments werefollowed throughout. Single unit activity was recorded from the mo-tor cortex of cats through chronically implanted microelectrodes,while they performed a trained reaching and retrieval task. Micro-electrodes were implanted into identified forelimb representation(shoulder, elbow, wrist or digits) of the motor cortex by prior stim-ulation mapping. Frame by frame analysis of video camera records ofthe task was used to time different stages of the task (premovement,reach, withdraw and feeding stages) and accurately relate neuralactivity to task stages. Temporal correlation between the spikeactivities of neurons was evaluated by shufflecorrected cross-correlograms.

Results: Over several months of recording, a variety of task re-lated modulations of neural activities were observed in individualefferent zones. Temporally correlated spike activity was rarely seenwhen the animal sat quietly, but often during task performance. Pos-itively correlated activity was frequently observed between neuronsactive during different movements (e.g. reaching and withdrawingthe forelimb), and between neurons in different representationzones (shoulder, elbow, wrist and digits). Most cross correlogramshad narrow peaks (<5 ms) and most peaks were centred on or closeto zero latency (<2 ms).

Discussion: This study found synchronization of action poten-tials among MI neurons specifically related to skilled motor tasks,and linking neurons controlling different aspects of the task. In pre-vious anatomical studies we have found extensive interconnectionsbetween representations of digits, wri st, elbow and shoulder, withinthe forelimb motor area of MI. These local intra-cortical networksmay play a role in synchronized spike activity and motor coordina-tion. A better understanding of the neural codes associated withmotor coordination is important for the development of corticallycontrolled limb prosthesis.

doi:10.1016/j.jocn.2009.07.080

1544 Abstracts / Journal of Clinical Neuroscience 16 (2009) 1514–1546