Vection in depth during treadmill walking

Vection has typically been induced in stationary observers (ie conditions providing visual-only information about self-motion). Two recent studies have examined vection during active treadmill walking--one reported that treadmill walking in the same direction as the visually simulated self-motion impaired vection (Onimaru et al, 2010 Journal of Vision 10(7):860), the other reported that it enhanced vection (Seno et al, 2011 Perception 40 747-750; Seno et al, 2011 Attention, Perception, & Psychophysics 73 1467-1476). Our study expands on these earlier investigations of vection during observer active movement. In experiment 1 we presented radially expanding optic flow and compared the vection produced in stationary observers with that produced during walking forward on a treadmill at a 'matched' speed. Experiment 2 compared the vection induced by forward treadmill walking while viewing expanding or contracting optic flow with that induced by viewing playbacks of these same displays while stationary. In both experiments subjects' tracked head movements were either incorporated into the self-motion displays (as simulated viewpoint jitter) or simply ignored. We found that treadmill walking always reduced vection (compared with stationary viewing conditions) and that simulated viewpoint jitter always increased vection (compared with constant velocity displays). These findings suggest that while consistent visual-vestibular information about self-acceleration increases vection, biomechanical self-motion information reduces this experience (irrespective of whether it is consistent or not with the visual input)

Adaptation to visual and nonvisual rearrangement

Role of informational feedback in producing visual adaptation to visual rearrangement and to various head, eye, and arm position

Visual experience is not necessary for efficient survey spatial cognition: Evidence from blindness

This study investigated whether the lack of visual experience affects the ability to create spatial infer-ential representations of the survey type. We compared the performance of persons with congenital blindness and that of blindfolded sighted persons on four survey representation-based tasks (Experiment 1). Results showed that persons with blindness performed better than blindfolded sighted controls. We repeated the same tests introducing a third group of persons with late blindness (Experiment 2). This last group performed better than blindfolded sighted participants, whereas differences between participants with late and congenital blindness were nonsignificant. The present findings are compatible with results of other studies, which found that when visual perception is lacking, skill in gathering environmental spatial information provided by nonvisual modalities may contribute to a proper spatial encoding. It is concluded that, although it cannot be asserted that total lack of visual experience incurs no cost, our findings are further evidence that visual experience is not a necessary condition for the development of spatial inferential complex representations. There is a general consensus on the crucial role of visual perception in guiding many of our daily movements in large- and small-scale environ

Representing 3D Space in Working Memory: Spatial Images from Vision, Hearing, Touch, and Language

The chapter deals with a form of transient spatial representation referred to as a spatial image. Like a percept, it is externalized, scaled to the environment, and can appear in any direction about the observer. It transcends the concept of modality, as it can be based on inputs from the three spatial senses, from language, and from long-term memory. Evidence is presented that supports each of the claimed properties of the spatial image, showing that it is quite different from a visual image. Much of the evidence presented is based on spatial updating. A major concern is whether spatial images from different input modalities are functionally equivalent— that once instantiated in working memory, the spatial images from different modalities have the same functional characteristics with respect to subsequent processing, such as that involved in spatial updating. Going further, the research provides some evidence that spatial images are amodal (i.e., do not retain modality-specific features)

Modelling Locomotor Control: the advantages of mobile gaze

In 1958, JJ Gibson put forward proposals on the visual control of locomotion. Research in the last 50 years has served to clarify the sources of visual and nonvisual information that contribute to successful steering, but has yet to determine how this information is optimally combined under conditions of uncertainty. Here, we test the conditions under which a locomotor robot with a mobile camera can steer effectively using simple visual and extra-retinal parameters to examine how such models cope with the noisy real-world visual and motor estimates that are available to humans. This applied modeling gives us an insight into both the advantages and limitations of using active gaze to sample information when steering

Functional analysis of the nonvisual opsins melanopsin and vertebrate ancient opsin (VA opsin) in Atlantic salmon (Salmo salar)

The role of nonvisual photoreceptors is yet to be elucidated regarding the link to biological function. This study aims to characterise the expression pattern of melanopsin and vertebrate ancient opsin during early developmental stages of Atlantic salmon, and to relate the function of these genes to hatching. Fertilised salmon’s eggs were subjected to different light qualities using LED technology where intensity and spectrum was manipulated. Two light regimes, 24 hours of continuous light (LL) and 14 hours of light:10 hours of darkness (LD) of white light of different intensities, high, medium, and low, beside different light spectrum of the same intensity, deep red, amber, green, blue, royal blue, and ultra violet were used. Continuous dark was used as a control. Eggs were monitored during the study period and hatched eggs recorded. In situ hybridization technique was used to characterise the expression of two nonvisual opsin, the vertebrate ancient opsin (VA) and melanopsin. The results from hatching experiment show that, while continues white light and LD cycles of white light of the medium intensity increase the hatching period (span), LD cycles of the low intensity white light decease it significantly. However, the time to 50% of hatching is significantly increased by LD cycles of green light blue light, and low intensity of white light. The results from the expression experiments has shown that both melanopsin and VA opsin are expressed in the brain of salmon during the early developmental stages. Both were found in the left habenula, thalamus, hindbrain and spinal cord. Moreover, they have been found to be colocalised in several regions in the brain. Furthermore, regional specific neural activation was found in the habenula and hindbrain, where melanopsin and VA opsin are co-localized, upon light stimulation. This indicate direct photoreception in these brain regions already around hatching. The result indicates that, apparently, the hatching process in salmon may be affected by light to some degree, but there is no strong inhibition of hatching by light such reported for Atlantic halibut. Other factors like the temperature and low levels of oxygen might be other environmental cues that are used by Atlantic salmon to regulate the time of hatching. The nonvisual system is clearly developed and functional prior to hatching and may be part of the regulation of hatching. The specific nonvisual hindbrain cluster found to regulate hatching in Atlantic halibut are not apparent in salmon. Our data clearly shows the important of nonvisual photoreception in the brain at early developmental stages of fish, prior to development of functional eyes. There seems to be species-specific patterning of the nonvisual photoreceptors in the brain, which indicates species specific tailoring of biological function.Master's Thesis in BiologyBIO39