Beyond illusions : on the limitations of perceiving relational properties

Explaining the perception of our visual world is a hard problem because the visual system has to fill the gap between the information available to the eye and the much richer visual world that is derived from the former. Perceptual illusions continue to fascinate many researchers because they seem to promise a glimpse of how the visual system fills this gap. Illusions are often interpreted as evidence of the error -prone nature of the process. Here I will show that the opposite is true. To do so, I introduce a novel stance on what constitutes an illusion, arguing that the traditional view (illusion as mere discrepancy between stimulus and percept) has to be replaced by illusion as a manifest noticed discrepancy. The two views, unfortunately, are not necessarily related. On the contrary; we experience the most spectacular illusions where our perception is pretty much on target. Once our interpretation of the sensory data is off the mark, we usually no longer experience illusions but live happily without ever noticing the enormous perceptual and conceptual errors we make. The farther we move away from simple pictorial stimuli as the subject of our investigations, the more commonplace a discrepancy between percept and reality does become —and the less likely we are willing to call it illusory. Two case studies of our perception of relational properties will serve to illustrate this idea. The case studies are based on the conviction that perceiving is more than mere sensation, and that some degree of (unconscious) judgment is a necessary ingredient of perception. We understand little about how to balance objects and we make fundamental mistakes when perceiving the slipperiness of surfaces. All the while, we never experience illusions in this context. Thus, when dealing with simple percepts, illusions may be revealing. But when it comes to percepts that involve relational properties, illusions fail to arise, as perception is not concerned with veridicality but appears to be satisfied with the first solution that does not interfere with our daily activities

A Novel Haptic Simulator for Evaluating and Training Salient Force-Based Skills for Laparoscopic Surgery

Laparoscopic surgery has evolved from an \u27alternative\u27 surgical technique to currently being considered as a mainstream surgical technique. However, learning this complex technique holds unique challenges to novice surgeons due to their \u27distance\u27 from the surgical site. One of the main challenges in acquiring laparoscopic skills is the acquisition of force-based or haptic skills. The neglect of popular training methods (e.g., the Fundamentals of Laparoscopic Surgery, i.e. FLS, curriculum) in addressing this aspect of skills training has led many medical skills professionals to research new, efficient methods for haptic skills training. The overarching goal of this research was to demonstrate that a set of simple, simulator-based haptic exercises can be developed and used to train users for skilled application of forces with surgical tools. A set of salient or core haptic skills that underlie proficient laparoscopic surgery were identified, based on published time-motion studies. Low-cost, computer-based haptic training simulators were prototyped to simulate each of the identified salient haptic skills. All simulators were tested for construct validity by comparing surgeons\u27 performance on the simulators with the performance of novices with no previous laparoscopic experience. An integrated, \u27core haptic skills\u27 simulator capable of rendering the three validated haptic skills was built. To examine the efficacy of this novel salient haptic skills training simulator, novice participants were tested for training improvements in a detailed study. Results from the study demonstrated that simulator training enabled users to significantly improve force application for all three haptic tasks. Research outcomes from this project could greatly influence surgical skills simulator design, resulting in more efficient training

Ability of Audio Feedback in E-books to compensate for haptic attachment to print books

Retinal degenerations encompass a large number of diseases in which the retina and associated retinal pigment epithelial (RPE) cells progressively degenerate leading to severe visual disorders or blindness. Retinal degenerations can be divided into two groups, a group in which the defect has been linked to a specific gene and a second group that has a complex etiology that includes environmental and genetic influences. The first group encompasses a number of relatively rare diseases with the most prevalent being Retinitis pigmentosa that affects approximately 1 million individuals worldwide. Attempts have been made to correct the defective gene by transfecting the appropriate cells with the wild-type gene and while these attempts have been successful in animal models, human gene therapy for these inherited retinal degenerations has only begun recently and the results are promising. To the second group belong glaucoma, age-related macular degeneration (AMD) and diabetic retinopathy (DR). These retinal degenerations have a genetic component since they occur more often in families with affected probands but they are also linked to environmental factors, specifically elevated intraocular pressure, age and high blood sugar levels respectively. The economic and medical impact of these three diseases can be assessed by the number of individuals affected; AMD affects over 30 million, DR over 40 million and glaucoma over 65 million individuals worldwide. The basic defect in these diseases appears to be the relative lack of a neurogenic environment; the neovascularization that often accompanies these diseases has suggested that a decrease in pigment epithelium-derived factor (PEDF), at least in part, may be responsible for the neurodegeneration since PEDF is not only an effective neurogenic and neuroprotective agent but also a potent inhibitor of neovascularization. In the last few years inhibitors of vascularization, especially antibodies against vascular endothelial cell growth factors (VEGF), have been used to prevent the neovascularization that accompanies AMD and DR resulting in the amelioration of vision in a significant number of patients. In animal models it has been shown that transfection of RPE cells with the gene for PEDF and other growth factors can prevent or slow degeneration. A limited number of studies in humans have also shown that transfection of RPE cells in vivo with the gene for PEDF is effective in preventing degeneration and restore vision. Most of these studies have used virally mediated gene delivery with all its accompanying side effects and have not been widely used. New techniques using non-viral protocols that allow efficient delivery and permanent integration of the transgene into the host cell genome offer novel opportunities for effective treatment of retinal degenerations

Determining the Contribution of Visual and Haptic Cues during Compliance Discrimination in the Context of Minimally Invasive Surgery

While minimally invasive surgery is replacing open surgery in an increasing number of surgical procedures, it still poses risks such as unintended tissue damage due to reduced visual and haptic feedback. Surgeons assess tissue health by analysing mechanical properties such as compliance. The literature shows that while both types of feedback contribute to the final percept, visual information is dominant during compliance discrimination tasks. The magnitude of that contribution, however, was never quantitatively determined. To determine the effect of the type of visual feedback on compliance discrimination, a psychophysical experiment was set up using different combinations of direct and indirect visual and haptic cues. Results reiterated the significance of visual information and suggested a visio-haptic cross-modal integration. Consequently, to determine which cues contributed most to visual feedback, the impact of force and position on the ability to discriminate compliance using visual information only was assessed. Results showed that isolating force and position cues during indentation enhanced performance. Furthermore, under force and position constraints, visual information was shown to be sufficient to determine the compliance of deformable objects. A pseudo-haptic feedback system was developed to quantitatively determine the contribution of visual feedback during compliance discrimination. A psychophysical experiment showed that the system realistically simulated viscoelastic behaviour of compliant objects. Through a magnitude estimation experiment, the pseudo-haptic system was shown to be successful at generating haptic sensations of compliance during stimuli indentation only by modifying the visual feedback presented to participants. This can be implemented in research and educational facilities where advanced force feedback devices are inaccessible. Moreover, it can be incorporated into virtual reality simulators to enhance force ranges. Future work will assess the value of visual cue augmentation in more complicated surgical tasks

A study of behavioural, cognitive and neural markers underlying visuospatial learning

Visuospatial (VS) learning is an education format noted for encouraging an individual to use visual exploration and their innate spatial ability in constructing a flexible ‘internal mental representation’ of three-dimensional information. Being a discipline reliant upon this informed consideration, VS methods have found particular application in anatomy education – with tangential evidence linking the inclusion of these methods to greater student understanding of anatomical concepts. Building on these findings, this thesis investigates: (i) the extent of individual and group learning benefits that accompany VS instruction within anatomy education, and (ii) a novel exploration of the cognitive and neuroscientific mechanisms that govern their success. To chart the success of instructional methodology in our reporting, we selected an array of academic performance and accompanying engagement indices. These items had been expressed by numerous modestly-powered prior studies, encompassing a diversity of anatomy cohorts, to be heightened under VS learning. Our initial work in Chapter 2 was therefore to determine if these effects were preserved when VS instruction was introduced within a substantially larger undergraduate anatomy cohort. Findings substantiated the wider applicability of this teaching method, with academic scores in each of the examined categories (didactic, spatial, and extrapolation) being superior to standard course delivery. Conflictingly, lower engagement and desire for VS inclusion was noted in the group receiving this instruction – leading us to attribute this to prevailing misconceptions about the nature of VS learning. In order to determine whether benefits found to characterise VS teaching in anatomy were universally applicable, or attributable to a myriad of demographic and cognitive factors, Chapter 3 explored variation in individual spatial capacity. Interestingly, the prevailing advantage of raw spatial aptitude in males was not associated with improved practical performance. This subsequently allowed a component of underlying psychological reasoning, namely visualisation (Vz) ability, to be highlighted as the clearest indicator of one’s ability to transfer raw spatial intelligence into practical VS understanding. Accompanying the misconceptions of VS learning reported in Chapter 2, participants were found to be poor estimators of their VS ability. Having established that spatial reasoning in anatomy possesses a physiological basis, we conducted a novel exploration of the neuroscientific mechanism evoked in VS learning using electroencephalography (EEG) technology (Chapter 4). This was evaluated by monitoring the neural signals of individuals engaged in two anatomical education workshops (featuring standard or VS instruction). No significant differences in oscillatory power accounted for the influence of VS instruction within any of the assessed frequency ranges (2-45Hz). Objective task outcomes were consistent with those in Chapter 2, finding a similarly elevated ability to address spatial questions following VS instruction. When placed together, the results of Chapters 2, 3 and 4 demonstrate the explicit advantages present for VS instruction in anatomy education. Though further work is required to isolate the specific underlying neural pathways, this appears linked to passive changes in how the human brain processes and later consolidates this information. Findings have important implications for advancing medical educational strategy (Appendix Descriptive Review), and wider understanding of the mechanisms that govern learning.Thesis (Ph.D.) -- University of Adelaide, Adelaide Medical School, 202

Optimising the use and assessing the value of intraoperative shear wave elastography in neurosurgery

The clinical outcomes for epilepsy and brain tumour surgery depend on the extent of resection. Neurosurgeons frequently rely on subjective assessment of stiffness and adherence to achieve maximal resection. However, due to similarity in tactile texture and visual appearance of these lesions to normal brain, this can lead to inadequate resection. Magnetic resonance imaging (MRI) has not completely solved this problem for various reasons, including the existence of MRI-negative lesions. Shear wave elastography (SWE) is an ultrasound-based quantitative elasticity imaging technique that provides an objective assessment of stiffness, which has not previously been applied intraoperatively during neurosurgery. This thesis describes the optimisation and assessment of implementing intraoperative SWE in neurosurgery. The aims of the work described in this thesis were to validate SWE measurements; to optimise intraoperative applications by investigating the artefacts of SWE; to evaluate SWE performance in detecting epileptogenic lesions, residual tumour and slippery boundaries; and to determine the histopathological correlation with SWE measurements. Using gelatine phantoms and post-mortem mouse brains, SWE measurements were validated. Through phantom models and ex vivo porcine brains and spinal cords, the factors affecting SWE measurements were established and SWE settings optimised. In addition, novel features of slippery tumour-brain interface were demonstrated in vitro and confirmed intraoperatively. Clinical implementation of SWE in epilepsy (38 patients) and brain tumour surgery (34 patients), demonstrated SWE’s capability in differentiating epileptogenic lesions (p<0.001) and brain tumours (p=0.003) from normal brain. SWE was shown to be superior to MRI in detecting epileptogenic lesions (p=0.001), in particular MRI-negative cases where SWE managed to demonstrate lesions in 4 cases with positive histology. For detecting residual tumour, SWE was shown to be superior to surgeons’ opinion (p=0.001), and similar to MRI (p=1.000) and intraoperative B-mode ultrasound (p=0.727). Histopathologically, there was no correlation with SWE measurements, except for proliferation (p=0.007). In conclusion, this thesis demonstrated potential patient benefit of integrating intraoperative SWE into neurosurgical practice, and therefore, a compelling reason to continue development and optimisation of this technology