Global Motion Perception in 4.5-year-old Children Born at Risk of Abnormal Neurodevelopment ...

203 Pages·2015·3.11 MB·English

by  Arijit Chakraborty

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Global Motion Perception in 4.5-year-old
Children Born at Risk of Abnormal
Neurodevelopment

Arijit Chakraborty

A thesis submitted in fulfilment of the requirements for the degree of
Doctor of Philosophy in Optometry and Vision Science, The University of Auckland, 2015.
Abstract

AIM Dorsal extrastriate visual areas, which include regions specialized for motion
processing, are thought to be particularly vulnerable to the effects of abnormal
neurodevelopment. This thesis aimed to test the hypothesis that global motion perception,
an index of dorsal stream function, would be affected by two distinct perinatal risk factors for
abnormal neurodevelopment: prenatal exposure to recreational drugs and neonatal
hypoglycemia. Both of these risk factors are commonly reported among infants in developed
countries.

METHODS Global motion perception was assessed using random dot kinematograms in a
large cohort of 4.5-year-old children who participated in one of two multi-disciplinary,
longitudinal studies; the Infant Development, Environment and Lifestyle (IDEAL) study or the
Children with Hypoglycemia and their Later Development (CHYLD) study. This thesis is divided
into four parts. The first part explored the influence of early visual functions, such as contrast
sensitivity for motion direction discrimination and visual acuity on global motion perception
in 4.5-year-old children. The second part focused on the association between global motion
perception and neuromotor functions, both of which are thought to involve the dorsal
stream. The third and fourth parts investigated whether global motion perception was
affected by prenatal exposure to recreational drugs or neonatal hypoglycemia respectively.

RESULTS Global motion perception was found to be independent from contrast
sensitivity and visual acuity. Moreover, global motion perception was associated with
neuromotor function in children born at risk of abnormal neurodevelopment. With regard to
neurodevelopmental risk factors, global motion perception was significantly affected by
prenatal drug exposure whereby exposure to alcohol worsened and exposure to marijuana
improved motion processing in children. In addition, global motion perception was
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significantly poorer in children who experienced neonatal hypoglycemia compared to
children who were euglycemic despite having risk factors for neonatal hypoglycemia.

CONCLUSIONS Global motion perception in children reflects visual function beyond
the stage of contrast encoding and is associated with motor function. Global motion
perception is also influenced by perinatal risk factors in children. These results are consistent
with the dorsal stream vulnerability hypothesis and support the use of global motion
perception as a tool to investigate abnormal neurodevelopment in children.

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Dedication

To those 1.4 million children who cannot see this beautiful world

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Acknowledgements

Writing an acknowledgment is often more difficult than drafting a research manuscript. These
three and half years of my PhD have been an experience which I shall cherish for the rest of
my life. I take this opportunity to thank all my supporters and critics who have helped me to
learn so much in this incredible path of academic research.

I start this acknowledgement by expressing my heartfelt thanks to my supervisor, Associate
Professor Benjamin Thompson, for his continuous support and encouragement in this long
yet enchanting journey of doctoral studies. Ben, I am glad that I took the decision to quit my
academic job in Malaysia and pursue doctoral studies with you. Frankly, I have never idolized
anyone in the past; but today I do idolize you. You have been an inspiration to me on both a
personal and a professional level.

I would also like to thank deeply my co-supervisors, Associate Professor Robert Jacobs and Dr
Nicola Anstice, for their immense help in refining my clinical skills and also for their continuous
feedback on my thesis and manuscripts.

Sincere thanks to Distinguished Professor Jane Harding for allowing me to work in the CHYLD
study. It was indeed the experience of a lifetime to work alongside a diverse yet wonderfully
cohesive bunch of researchers.

Associate Professor Trecia Wouldes deserves a special mention in this acknowledgement for
providing me with the opportunity to join the exciting IDEAL study team. Her precious help
has enabled me to understand the core of neurobehavioral development and to analyse the
findings of this large-scale multidisciplinary research.

I also thank the development assessors of the CHYLD and IDEAL study team, Jenny Rogers and
Heather Stewart, for being such lovely travel companions while conducting assessments
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outside Auckland. Also, the amazing members of the study coordination and database team
of the IDEAL and CHYLD studies deserve a special mention.

I would also like to thank my fellow PhD students within the CHYLD study group, especially
Nabin Paudel and Dr Nataliia Burakevych, for the motivation and help they have provided
during the course of my PhD.

Special thanks to the past and present lab members within the Visual Neuroscience research
group, including Victor Borges, Dr Sandy Yu, Lisa Hamm, Dr Daniel Spiegel, Tanya Poppe, Tina
Gao, Myra Leung, Dr Alice Lagas, Dr Cindy Guo and Dr Joanne Black. You guys are just amazing
and have always helped me keep my morale high on this journey.

I also take this opportunity to thank the University of Auckland for awarding me the doctoral
scholarship to fund my PhD study. I would also like to thank the Maurice and Phyllis Paykel
Trust, the ARVO Foundation and the Faculty of Medical and Health Science Postgraduate
Students’ Association for awarding me travel grants at various stages of my PhD, which took
care of my travel expenses for attending international conferences. Also, additional funding
from Associate Professor Robert Jacob’s own research grant has ensured that monetary
constraints would not prevent me from presenting my doctoral work internationally.

A mere acknowledgement cannot repay the debt to our parents. My father had been
instrumental in my decision to take up a career in academia. He always wanted me to pursue
a career in Neuroscience. Unfortunately, he did not live to see the completion of this thesis.
The absence of my father had been somewhat overcome by the strong support of my mother,
who has always been encouraging in this journey of doctoral studies.

Lastly, but most importantly, I would like to thank my lovely wife Priyanka Roy for putting up
with all my eccentricities and insanities. Priyanka, even while being several thousand miles
away, in India, you have been the strongest pillar of strength in this interstellar journey of
doctoral studies. Thanks for supporting me through thick and thin. This thesis would not have
been possible without your constant motivation and support.

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Co-Authorship Forms

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