title: Ageing, Motion Perception and the Compensation for Eye Movements

authors: Rawley, Kirstyn Michelle

subjects: ageing

abstract: Smooth pursuit over a textured background introduces full-field motion to the retinal image in the direction opposing the eye movement. If this motion is not correctly attributed to the eye movement, it can be falsely perceived as motion in the world (Haarmeier, Thier, Repnow & Petersen, 1997). In order to correctly attribute retinal motion, the visual system must compensate for the effects of eye movements on the retinal image in motion perception. Visual motion perception is important for safely navigating the environment and has been linked to difficulties experienced by older adults while driving (Conlon & Herkes, 2008; Raghuram & Lakshminarayanan, 2006) and walking (Cavanaugh, 2002). The experiments reported in this thesis were devised in order to examine the effects of ageing on the perception of illusory motion during eye movements and therefore on the ability to compensate for eye movements in motion perception. The perception of motion during smooth pursuit eye movements was assessed in adults ranging in age from 17 to 79 years. The computer based task required participants to respond to the speed and direction of motion of a large-field random dot pattern while following a moving target dot with the eyes. For this task, a magnitude estimation tool was especially designed based on the direction response method of Bennett, Sekuler and Sekuler (2007). During the experimental session an eye tracker recorded the participant's eye movements. For the purposes of analysis, four groups were defined by age. It was found that the smooth pursuit of adults from ~40 years of age was slower than that of the younger age groups. With stationary eyes, the oldest age group ranging in age from 60 to 79 years tended to overestimate the speed of the dot pattern as compared to younger observers. This tendency decreased at higher background speeds. Eye movements appeared to affect the perception of the dot field's motion more in the group of participants ranging in age from 40 to 54 years than in the younger age groups. This also seemed to be the case for participants aged over 60 when viewing horizontal motion but not vertical motion. The results of this study suggest that older observers may be less able to compensate for the effects of eye movements on the retinal image. This could potentially affect their ability to safely and confidently navigate the environment.

text: Ageing, Motion Perception and the Compensation for Eye Movements Smooth pursuit over a textured background introduces full-field motion to the retinal image in the direction opposing the eye movement. If this motion is not correctly attributed to the eye movement, it can be falsely perceived as motion in the world (Haarmeier, Thier, Repnow & Petersen, 1997). In order to correctly attribute retinal motion, the visual system must compensate for the effects of eye movements on the retinal image in motion perception. Visual motion perception is important for safely navigating the environment and has been linked to difficulties experienced by older adults while driving (Conlon & Herkes, 2008; Raghuram & Lakshminarayanan, 2006) and walking (Cavanaugh, 2002). The experiments reported in this thesis were devised in order to examine the effects of ageing on the perception of illusory motion during eye movements and therefore on the ability to compensate for eye movements in motion perception. The perception of motion during smooth pursuit eye movements was assessed in adults ranging in age from 17 to 79 years. The computer based task required participants to respond to the speed and direction of motion of a large-field random dot pattern while following a moving target dot with the eyes. For this task, a magnitude estimation tool was especially designed based on the direction response method of Bennett, Sekuler and Sekuler (2007). During the experimental session an eye tracker recorded the participant's eye movements. For the purposes of analysis, four groups were defined by age. It was found that the smooth pursuit of adults from ~40 years of age was slower than that of the younger age groups. With stationary eyes, the oldest age group ranging in age from 60 to 79 years tended to overestimate the speed of the dot pattern as compared to younger observers. This tendency decreased at higher background speeds. Eye movements appeared to affect the perception of the dot field's motion more in the group of participants ranging in age from 40 to 54 years than in the younger age groups. This also seemed to be the case for participants aged over 60 when viewing horizontal motion but not vertical motion. The results of this study suggest that older observers may be less able to compensate for the effects of eye movements on the retinal image. This could potentially affect their ability to safely and confidently navigate the environment.

year: 2010

title: Marine pests in paradise: capacity building, awareness raising and preliminary introduced species port survey results in the Republic of Palau

authors: Campbell, Marnie L.

subjects: non-indigenous species

abstract: Introduced marine species can have a large impact upon small countries that are reliant on marine tourism. Non-governmental organisations, such as the World Conservation Union (IUCN), are working with technical experts to implement capacity building and awareness programs that transfers introduced marine species knowledge to countries in need of aid. The Republic of Palau is reliant on tourism and as such is proactively engaging in this process to ensure that it has the necessary skills to determine and manage its introduced marine species pathways and vectors. The IUCN with the aid of technical experts implemented a four day training workshop that provided both theoretical and practical field experience with introduced marine species port surveys. An outcome of this exercise was the detection of 11 introduced marine species, the training of 10 Palau agencies and two international organisations, and recommendations for future implementation that will aid Palau to address the problem of introduced marine species within their borders.

text: Marine pests in paradise: capacity building, awareness raising and preliminary introduced species port survey results in the Republic of Palau Introduced marine species can have a large impact upon small countries that are reliant on marine tourism. Non-governmental organisations, such as the World Conservation Union (IUCN), are working with technical experts to implement capacity building and awareness programs that transfers introduced marine species knowledge to countries in need of aid. The Republic of Palau is reliant on tourism and as such is proactively engaging in this process to ensure that it has the necessary skills to determine and manage its introduced marine species pathways and vectors. The IUCN with the aid of technical experts implemented a four day training workshop that provided both theoretical and practical field experience with introduced marine species port surveys. An outcome of this exercise was the detection of 11 introduced marine species, the training of 10 Palau agencies and two international organisations, and recommendations for future implementation that will aid Palau to address the problem of introduced marine species within their borders.

year: 2016

title: Book review: Beyond the scene: Landscape and identity in Aotearoa New Zealand – Edited by Janet Stephenson, Mick Abbott and Jacinta Ruru

authors: Beattie, James John

subjects: book review

abstract: This article reviews the book: “Beyond the scene: Landscape and identity in Aotearoa New Zealand”, edited by Janet Stephenson, Mick Abbott and Jacinta Ruru.

text: Book review: Beyond the scene: Landscape and identity in Aotearoa New Zealand – Edited by Janet Stephenson, Mick Abbott and Jacinta Ruru This article reviews the book: “Beyond the scene: Landscape and identity in Aotearoa New Zealand”, edited by Janet Stephenson, Mick Abbott and Jacinta Ruru.

year: 2010-12