Linking brain and behaviour in motor sequence learning tasks

Sequence learning is a fundamental brain function that allows for the acquisition of a wide range of skills. Unlearned movements become faster and more accurate with repetition, due to a process called prediction. Predictive behaviour observed in the eye and hand compensates for the inherent temporal delays in the sensorimotor system and allows for the generation of motor actions prior to visual guidance. We investigated predictive behaviour and the brain areas associated with this processing in (i) the oculomotor system (Eye Only (EO): saccade vs. pursuit) and (ii) during eye and hand coordination (EH). Participants were asked to track a continuous moving target in predictable or random sequence conditions. EO and EH experiments were divided into 1) EO behavioural and 2) EO fMRI findings, and 3) EH behavioural and 4) EH fMRI findings. Results provide new insights into how individuals predict when learning a sequence of target movements, which is not limited to short--‐term memory capacities and that forms a link between shorter and longer--‐term motor skill learning. Furthermore, brain imaging results revealed distinct levels of activation within and between brain areas for repeated and randomized sequences that reflect the distinct timing threshold and adaptation levels needed for the two oculomotor systems. EH results revealed similar predictive behaviour in the eye and the hand, but also demonstrated enhanced coupling between the two motor systems during sequence learning. EH brain imaging findings have provided novel insights into the brain areas involved in coordination, and those areas more associated with sequence learning. Results show evidence of common predictive networks used for the eye and hand during learning

Eye-Hand Coordination in Time and Space

In dieser Arbeit wurden die Mechanismen der Auge-Hand-Koordination und ihre Abhängigkeit vom Aufgabenkontext untersucht

Naturalistic depth perception and binocular vision

Humans continuously move both their eyes to redirect their foveae to objects at new depths. To correctly execute these complex combinations of saccades, vergence eye movements and accommodation changes, the visual system makes use of multiple sources of depth information, including binocular disparity and defocus. Furthermore, during development, both fine-tuning of oculomotor control as well as correct eye growth are likely driven by complex interactions between eye movements, accommodation, and the distributions of defocus and depth information across the retina. I have employed photographs of natural scenes taken with a commercial plenoptic camera to examine depth perception while varying perspective, blur and binocular disparity. Using a gaze contingent display with these natural images, I have shown that disparity and peripheral blur interact to modify eye movements and facilitate binocular fusion. By decoupling visual feedback for each eye, I have found it possible to induces both conjugate and disconjugate changes in saccadic adaptation, which helps us understand to what degree the eyes can be individually controlled. To understand the aetiology of myopia, I have developed geometric models of emmetropic and myopic eye shape, from which I have derived psychophysically testable predictions about visual function. I have then tested the myopic against the emmetropic visual system and have found that some aspects of visual function decrease in the periphery at a faster rate in best-corrected myopic observers than in emmetropes. To study the effects of different depth cues on visual development, I have investigated accommodation response and sensitivity to blur in normal and myopic subjects. This body of work furthers our understanding of oculomotor control and 3D perception, has applied implications regarding discomfort in the use of virtual reality, and provides clinically relevant insights regarding the development of refractive error and potential approaches to prevent incorrect emmetropization

An investigation into the cognitive effects of delayed visual feedback

Abstract unavailable please refer to PD

Using Multi-Modal Bio-Digital Technologies to Support the Assessment of Cognitive Abilities of Children with Physical and Neurological Impairments

Current studies done using a learning test for children have problems as they only make evaluations of Physically and Neurologically Impaired (PNI) children who can succeed in the test and can be considered as a PASS/FAIL test. This pilot study takes a holistic view of cognitive testing of PNI children using a user-test-device triad model and provides a framework using non-PNI children and adults as controls. Comparisons using adapted off-the-shelf novel interfaces to the computer, in particular, an Electroencephalograph (EEG) head-set, an eye-tracker and a head-tracker and a common mouse were carried out. In addition, two novel multi-modal technologies were developed based on the use of brain-waves and eye-tracking as well as head-tracking technologies to support the study. The devices were used on three tests with increasing cognitive complexity. A self-developed measure based on success streaks (consecutive outcomes) was introduced to improve evaluations of PNI children. A theoretical model regarding a fit of ability to devices was initially setup and finally modified to fit the view of the empirical model that emerged from the outcomes of the study. Results suggest that while multi-modal technologies can address weaknesses of the individual component modes, a compromise is made between the user’s ability for multi-tasking between the modes and the benefits of a multi-modal device but the sample size is very small. Results also show children failing a test with a mouse but passing it subsequently when direct communication is used suggesting that a device can affect a test for children who are of a developing age. This study provides a framework for a more meaningful conversation between educational psychologists as well as other professionals and PNI parents because it provides more discrimination of outcomes in cognitive tests for PNI children. The framework provides a vehicle that addresses scientifically the concerns of parents and schools.EPSR

Repeatability and reproducibility of visual field tests in people with established visual field loss

The thesis investigated the repeatability of the Esterman Visual Field Test (EVFT) on the Humphrey Field Analyser (HFA), and the reproducibility of the EVFT on the HFA and Henson Pro 5000 Perimeter. The reproducibility of the Ring of Sight (ROS) 24-2 full threshold (FT) examination was also evaluated. These were investigated with participants with established visual field loss (VFL) using case control studies. The reduced sensitivity that influences test-retest variability in those with VFL and differences within the perimeter methodologies, including the influence of background luminance were considered. Agreement in sensitivity threshold values or the Esterman Efficiency Scores (EES) between perimeters were analysed and pointwise analysis was undertaken. Any change in fitness-to-drive status or ability to determine/rule out disease was investigated. Principal Findings: The EVFT possesses poor repeatability and reproducibility for individuals with VFL with significant change in EES on test-retest at different sessions and significant lack of agreement when comparing EES on the HFA and the Henson Pro 5000 Perimeter. The EVFT possesses good repeatability and reproducibility in fitness-to-drive status. The significant variation in EES and location of defect in those with VFL does not impact upon on an individual’s fitness-to-drive status. It is recommended that a repeat examination is performed on the HFA for those with VFL who fails the EVFT on initial examination to account for variability of test-retest and the significantly lower EES recorded by the Henson Pro 5000 Perimeter. There is a large proportion of those with VFL (33.33%) who are unable to see a target, which is required to be seen, in order to conduct a visual field test on the ROS. There is significant lack of agreement in defect depth, defect location, mean deviation and sensitivity threshold values found on the ROS 24-2 FT examination compared to the SITA Standard 24-2 examination performed on the HFA. The ROS possesses a sensitivity value of 33.33%