Glaucoma impacts vision by affecting visual processing at the retinal ganglion cell level. To recreate its impact on visual processing, photobleaching has been proposed to reversibly and temporarily induce glaucoma-like saccadic reaction time. It has been established that photobleaching elevates the threshold detection levels of visual stimuli in a healthy retina. This study investigated the potential implementation of photobleaching to recreate glaucoma-like SRTs. Results from the study show that photobleaching increased the SRT and reduced the ability to detect targets within the photobleaching zone of the visual field. The elevated SRTs obtained from the study indicate that photobleaching is a valid method for obtaining mild glaucoma-like SRTs. Furthermore, the effects of photobleaching were found to be highly localized, with the impact primarily observed within the bleaching zone. Attempts to replicate the localized effects of glaucoma using discrete photobleaching were inconclusive, with elevated SRTs observed in some cases, but the effect is directly related to the total area bleached. These findings provide the relationship between photobleaching, saccadic response, and their potential implications for artificially recreating glaucoma-like elevated SRTs

Although the roles of visual and haptic cues in motor tasks have been well studied, the benefits of audio cues in complex motor tasks have been underexplored. Audiovisual cues reduce reaction times and decrease the variance of endpoint responses in simple head-orienting localization tasks. The aim of this research is to explore the potential of audiovisual stimuli for motor tasks performed in a real-life environment. Participants performed simple head and arm localization tasks in an echoic room. Comparing audiovisual stimuli to unimodal stimuli, a decrease in reaction times was observed. For head responses, reaction times were reduced on average by 58 ms for visual stimuli and 35 ms for auditory stimuli. For arm responses, reaction times showed a decrease of 30 ms on average for both unimodal conditions. Likewise, we noted decreased endpoint variance in audiovisual responses in comparison to unimodal auditory responses. Moreover, we observed a modality-effector dependency in the weighting of auditory and visual signals in the audiovisual responses. These results show the potential of audiovisual stimuli for real-life applications in motor tasks.

Parkinson’s Disease is a neurodegenerative disease that has a decline in motor behaviour as one of its main symptoms. This decline is currently monitored using subjective measures, such as questionnaires and clinical observations. More detailed and objective tracking of this decline can improve treatment of the disease and allow for earlier identification. Earlier work in this area has lead to the development of a proof-of-concept for detecting behavioural changes in motor performance, but the linear regression model used was limited in its accuracy and had a high latency. This paper uses a non-linear Least Squares Support Vector Regression (LS-SVR) model to increase performance in those areas. LS-SVR was chosen for its ability to regress complex non-linear relationships and because it is highly adaptable and scalable, yet easy to understand and work with. Test data were simulated based on earlier measured data which resulted in a complete and varied data set that allows for exploring many different situations.
Results from the machine learning model when applied to the test data are promising. With the right combination of hyperparameter settings an improvement of 80% in accuracy was reached, and latency could be reduced by 30%. Additionally, a sensitivity analysis of the hyperparameters revealed further room for improvement with more careful tuning. Finally, it was shown that by using LS-SVR to make predictions on data from future trials a further reduction in latency can be achieved. Overall, the new model shows definite improvement over the earlier model and can be developed further in subsequent steps towards a clinical applicable method.

Eye movements are the result of complex interactions between cortical and sub-cortical regions. Consequently, they are considered as an important bio-marker for neurological function. Attempts to construct an oculomotor model rely on classic paradigms. In this research, a cybernetic approach was used to construct and examine a novel paradigm, which can be used as a new tool to quantify and classify neurodegeneration. Young, healthy adults (N = 24) participated in a quasi-random gaze pursuit tracking task to investigate horizontal and vertical gaze behavior in one- and two-dimensional tracking. Results indicate different horizontal gaze in terms of performance (13% and 23% better) and model parameters (5.6% and 10.2% higher Kg, 6.6% and 7.6% lower τg), comparing the 1D conditions and horizontal and vertical direction in the 2D condition, respectively. Vertical gaze due to cross-feed was observed up to 3 rad/s in presence of a horizontally moving target stimulus, varying in magnitude between subjects. For the proposed paradigm, an increased target signal bandwidth should be used, such that neuromuscular gaze dynamics can be captured as well, as these parameters are known to relate to neurodegeneration.