Collins, Peter (2016) The remediation of oculomotor and attentional deficits of children with ADHD

339 Pages·2017·5.37 MB·English

by  Christine Middleton

The remediation of oculomotor and attentional deficits of children with ADHD:
identifying and training control mechanisms based on ocular data

By
Peter Andrew Collins, BA. MA.
Student Number: 4174190

Division of Psychiatry and Applied Psychology
School of Medicine
The University of Nottingham

Thesis submitted to the University of Nottingham for the degree of Doctor of
Philosophy in the School of Medicine, September 2015
I
Abstract
This project set out to develop a cognitive training intervention for individuals with
attention deficit hyperactivity disorder (ADHD). The thesis builds on research suggesting
that reinforcement deficits in the ADHD population give rise to the underdevelopment of
a number of cognitive abilities, in particular inhibitory control skills. Arguing that this skill
is explicitly trainable and that training inhibitory gaze control is a means of training
inhibitory control, this thesis set out to utilise eye-tracking technology to assess
inhibitory gaze control performance in ADHD and to develop an engaging intervention in
the form of a computer game capable of training the inhibitory gaze control system.
Drawing on literature on inhibitory control in ADHD, the saccadic system, game
development, and cognitive load theory a training intervention and battery of
assessment tasks were developed iteratively across a number of pilot studies. The
development process and resultant cognitive training interventions are described. The
final proof-of-concept study was trialled for eight one-hour training sessions with an
ADHD population (N = 8). Comparisons of pre- and post-training assessments produced
strong effects for measures of gaze control, inhibitory control, timing, and attention. The
results are interpreted and a number of limitations noted. The potential benefits of such
interventions to aid clinicians to diagnose, to monitor, and to treat ADHD are considered.
The relevance of cognitive interventions in contributing to research attempting to
identify endophenotypes of ADHD is also discussed.

II
Declaration
I declare that this thesis is the result of my own work which has been undertaken during
my period of registration for this degree at The University of Nottingham. I have
complied with the word limit for my degree (as stated in the Quality Manual).

Acknowledgements
I would like to thank the Institute of Mental Health for funding this research. I am
grateful to the Adult ADHD clinic at QMC, QbTech Ltd, the Eunethydis Network, and
ESSEM for supporting this work. My sincere thanks also go to the many members of staff
at the QMC and Institute of Mental Health for their support, in particular Dr Maddie
Groom, Professor David Daly, Professor Chris Hollis, and my fellow PhD candidates. I am
especially grateful to my supervisors Dr Elizabeth Liddle and Professor Georgina Jackson
for their tireless patience, motivation, and immense knowledge. This project could not
have been achieved without the support of the Nottingham ADHD Support Group, the
Mellers and Portland primary schools, the Nottingham University’s Summer Scientist
Week, and especially not without all the participants who gave up their time to
contribute to this project. I would like to thank friends and family, without their support
it would not have been possible to conduct this research. Finally, I would like to thank
my partner Christina for supporting me throughout writing this thesis and my life in
general.

III
TABLE OF CONTENTS
CORE THESIS ARGUMENT AND STRUCTURE 1
1 INTRODUCTION 4
1.1 OVERVIEW OF ADHD 4
1.1.1 COGNITIVE DEFICITS IN ADHD 7
1.1.2 INHIBITORY CONTROL 10
1.1.3 PRIMARY VERSUS SECONDARY COGNITIVE DEFICITS 12
1.2 PROGRESS IN THE FIELD 14
1.2.1 MODELS OF ADHD 14
1.3 DYNAMIC DEVELOPMENTAL THEORY OF ADHD 17
2 RATIONALE FOR THE CURRENT INTERVENTION 19
2.1 ARGUMENT FOR TRAINING INHIBITORY CONTROL 19
2.2 TRAINING GAZE CONTROL 22
3 COGNITIVE TRAINING 25
3.1 TRAINING GENERAL INTELLIGENCE 26
3.2 ADHD AND COGNITIVE TRAINING 29
4 GAZE CONTROL IN ADHD 32
4.1 THE VISUAL SYSTEM 32
4.1.1 ANTICIPATORY AND FEED-FORWARD MODELS OF VISION 34
4.1.2 COMPETITIVE INTEGRATION MODEL 36
4.1.3 THE NEURAL ACTIVITY OF SACCADE GENERATION 37
4.2 SACCADE CONTROL IN ADHD 38
4.2.1 PROSACCADE 38
4.2.2 ANTISACCADE 40
4.2.3 STOP-SIGNAL TASK 42
4.2.4 FIXATION TASK 43
4.2.5 PUPILLOMETRY 44
5 WHAT TO TRAIN 45
5.1 INHIBITORY CONTROL CANNOT BE VIEWED IN ISOLATION 45
5.1.1 ATTENTION AND TIMING IN INHIBITORY GAZE CONTROL 46
5.1.2 TIMING 47
5.1.3 ATTENTION 51
6 HOW TO TRAIN 53
6.1 PRINCIPLES AND DESIGN 53
6.1.1 COMPLEXITY VERSUS SPECIFICITY 54
6.1.2 COGNITIVE LOAD THEORY 57
6.2 MOTIVATION 62
6.3 GAMES 67
6.3.2 INTRINSIC INTEGRATION 70
6.4 EXERCISE 72
IV
7 EQUIPMENT, PROGRAMMING, AND ALGORITHMS 75
7.1 EQUIPMENT 75
7.1.1 LIMITATION OF THE EYE-TRACKER 78
7.2 PROGRAMMING TASKS 81
7.2.1 SACCADE IDENTIFICATION 81
7.2.2 PROGRAMMING LOGIC AND ALGORITHMS 86
7.2.3 EYE-TRACKING PROCEDURE 88
8 PILOT STUDIES 91
8.1 EARLY PILOT STUDIES 93
8.1.2 ADULT POPULATION 1 95
8.1.3 ADULT POPULATION 2 97
8.2 LATER PILOT STUDIES 99
8.2.1 SUMMER SCIENTIST WEEK 2012 106
8.2.2 SUMMER SCIENTIST WEEK 2013 108
8.2.3 SCHOOL DATA 110
8.3 SUMMARY OF RESULTS 114
8.4 TASK REFINEMENT 115
9 A PROOF-OF-CONCEPT STUDY 122
9.1 METHODS 126
9.1.1 STUDY DESIGN 126
9.1.2 ETHICS 126
9.1.3 RECRUITMENT 127
9.1.4 PARTICIPANTS 128
9.2 PROCEDURE 129
9.2.1 ASSESSMENT PROCEDURE 129
9.3 ASSESSMENT TASKS 130
9.3.1 ASSESSMENT OF TRAINED TASKS 131
9.3.2 ASSESSMENT OF UNTRAINED TASKS 134
9.3.3 STANDARD ASSESSMENT TESTS 135
9.4 THE TRAINING GAME 139
9.4.1 THE ROLE OF THE EXPERIMENTER 144
9.4.2 TRAINING GAME TASKS 150
9.5 DATA PROCESSING 166
9.6 ANALYSIS 169
10 RESULTS 171
10.1 RESULTS 171
10.1.1 RESULTS FOR TRAINED TASKS 171
10.1.2 RESULTS FOR PUPIL DILATION FOR TRAINED SACCADE TASKS 173
10.1.3 RESULTS FOR NON-TRAINED EYE-TRACKING TASKS 174
10.1.4 RESULTS FOR THE STANDARD ASSESSMENT TASKS 175
10.2 RESULTS DISCUSSION 177

V
11 CASE STUDIES 187
11.1 PARTICIPANT 1016 191
11.2 PARTICIPANT 1087 199
11.3 PARTICIPANT 1134 207
11.4 PARTICIPANT 1358 215
11.5 PARTICIPANT 1434 223
11.6 PARTICIPANT 1523 231
11.7 PARTICIPANT 1633 239
11.8 PARTICIPANT 1864 247
11.9 DISCONTINUED PARTICIPANTS 255
12 DISCUSSION 259
12.1 PROJECT SUMMARY 259
12.2 PROOF-OF-CONCEPT GROUP RESULTS 261
12.3 USING EYE-TRACKING 266
12.4 LIMITATIONS 267
12.5 CONTINUATION OF THE WORK 268
12.6 FUTURE DEVELOPMENTS 271
12.7 A WIDER DISCUSSION OF THE ISSUES RAISED 272
12.7.1 COGNITIVE TRAINING 272
12.7.2 COMBINING COGNITIVE TRAINING WITH OTHER INTERVENTIONS 276
12.1 CONCLUDING REMARKS 284
13 REFERENCES 286
14 APPENDIX 317
14.1 POTENTIAL TASKS IMPROVES 317
14.2 USING THE EYE TRACKER - QUICK START GUIDE 319
14.3 SAMPLE SCRIPT 324
14.4 READING TEXT SAMPLE 330
14.5 RECRUITMENT POSTER 332

VI
1
Core thesis argument and structure
Sagvolden's Dynamic Developmental Theory proposes that the primary deficit in
attention deficit hyperactivity disorder (ADHD) is an atypical dopamine system,
which leads to reinforcement deficits (Chapter 1). The intervention developed as part
of this thesis is based on the assumption that, at least for a sub-group of those with
ADHD, a reinforcement deficit is a primary deficit. Due to this primary reinforcement
deficit learning is impaired in individuals with ADHD and they fail to acquire a
number of skills for which they have capacity, among them inhibitory control, and
specifically inhibitory gaze control. Inhibitory gaze control is of particular interest in
ADHD as it lies at the intersection of attentional, hyperactive, and impulsive
symptoms. In light of research that suggests that children acquire inhibitory control
skills, and that individuals with Tourette Syndrome and bilingual speakers
demonstrate enhanced inhibitory control I argue that it is a trainable skill. With the
correct performance contingent incentives inhibitory control may be trainable in
ADHD. A targeted training intervention was designed to utilise the proposed latent
capacity to remediate the inhibitory gaze control deficits seen in the ADHD
population (Chapter 2).
Mixed results have been observed in the cognitive training literature generally and
more specifically with ADHD (Chapter 3). In the development of the intervention I
draw upon the anticipatory, feed-forward, and competitive integration models of the
visual system, and review a number of saccade control paradigms and the
associated deficits observed in ADHD populations (Chapter 4). Building on this work
I argue that aspects of attention and timing are critically linked to inhibitory control
and should therefore also be targeted. A brief review of the literature on timing and
attention is provided (Chapter 5). Having identified the target of the intervention the
literature on motivation, gaming, and exercise is reviewed to identify principles the
training intervention can draw upon (Chapter 6).
I then outline the process by which the intervention was programmed. I discuss the
equipment used, as well as the algorithms and methods utilised to identify saccades
from the eye gaze data gathered (Chapter 7). A number of pilot studies conducted
to inform the development of the training intervention and the pre- and post-training
2
assessment tasks are reported. The process of task refinement and the changes
made are discussed (Chapter 8). The main proof-of-concept study, including the
methods and procedures, are described in full and a detailed description of the
training intervention and assessment tasks are given (Chapter 9). A comparison of
the pre- and post-training assessment tasks is presented and discussed (Chapter
10), followed by case studies of each of the participants (Chapter 11). The thesis
concludes with a discussion of the findings, limitations, and consideration of the
utility of cognitive interventions. A wider discussion of the potential use of cognitive
interventions as an alternatives and compliments to medication is considered
(Chapter 12).
3
1 Introduction
This project set out to develop a cognitive training intervention for individuals with
ADHD. In chapter 1 I present the context for the development of the training
intervention developed. I begin by providing an overview of ADHD; its classification,
prevalence, and impact on the individual and society. I provide a sketch of the
current state of the field, giving a summary of the cognitive deficits associated with
ADHD and an outline of some prominent theories attempting to account for these
deficits.
1.1 Overview of ADHD
Attention deficit hyperactivity disorder (ADHD) is a common highly heritable
persistent disorder with a childhood onset. While commonly present to some degree
in the general population, the diagnostic symptoms - impulsivity, hyperactivity and
inattention - are considered as being excessively intense or frequent, and age
inappropriate in cases of ADHD. Along with opposition defiance disorder, conduct
disorder and antisocial personality disorder, ADHD is classified as a disruptive
disorder (American Psychiatric Association, 2013). It is a highly heritable condition
with genes accounting for an estimated 76-80% of an individual’s susceptibility
(Faraone & Doyle, 2001). ADHD as classified by the American Psychiatric
Association’s criteria (American Psychiatric Association, 2010) has a prevalence rate
of 3% to 5% (Barkley et al., 2002). A diagnosis of Hyperkinetic Disorder is based on
a very similar set of symptoms published by The World Health Organisation in the
ICD-10. The ICD-10 diagnosis requires greater impairment than the DSM-5 and
emphasises impulse-control problems, resulting in the lower prevalence rate of 1-2%
(Banaschewski et al., 2009; Döpfner et al., 2008).
A diagnosis of ADHD is normally made by a clinician based on the presence of
symptoms that map onto the diagnostic criteria of the DSM-5 or ICD-10. A diagnosis
can be made primarily on the existence of attention problems, e.g. ‘has problems
maintaining focus on a task’, on hyperactivity/impulsivity symptoms, e.g. ‘often
fidgets with hands or feet or squirms in seat’ (American Psychiatric Association,
2013), or both. A diagnosis is a categorical decision based on a threshold number of
symptoms exhibited. The clinician draws on multiple sources of information to make
4