vVSS 2020 – virtual conferences during COVID-19 pandemic

2020 has been a challenging year for everyone, and annual meetings and conferences have not been the exception. Originally scheduled for May 2020 at St. Pete Beach, Florida, the annual meeting of the Vision Sciences Society was moved to an online version held between 19 and 24 of June, 2020.

So, to participate in vVSS, Juan Sepulveda presented online the results of his second PhD experiment that investigated whether mesopic light levels impact on the perception of motion, considering the effects of age and location of the moving stimulus within the visual field. The term “mesopic” describes lighting levels that are very dim, but not quite dark. Mesopic conditions result in activation of both rods and cones in the retina. Rods and cones are separate forms of photoreceptors (cells in the retina that respond to light) that underpin our ability to encode information about the world in both dark (rods) and light (cones) conditions. When both are active (such as in mesopic conditions), visual perception can differ from that in either light or dark conditions. There has previously been very little study of motion perception in mesopic conditions, particularly within non-central vision.

Play here the pre-recorded video poster presentation

He found that under low light levels, both older and younger adults have difficulties in the identification of the direction of motion of low-contrast sinusoidal patterns and also in identifying the direction of motion of a human walker in both central and peripheral vision.

Global motion perception (the ability to determine the overall direction of motion of a complex stimulus of moving dots) was specifically impaired in dim lighting for older adults in peripheral vision.

Although this year Juan could not enjoy travelling to the hot and sunny Florida during the Australian winter (actually, he was awarded with a ‘travel grant’ for this conference), he enjoyed sharing his work with the vision sciences community, scheduling some online Q&A sessions regarding his work. He also participated in online discussions regarding topics such as: vision sciences outside North America, future careers in vision sciences; and underrepresented groups in vision sciences. Juan has said: “This was an interesting experience that for sure will be relevant for my future career (and as an anecdote for future generations).”

A pdf copy of the poster can be downloaded below.

Vision and ageing: what happens to the perception of moving things?

One crucial ability for humans is the perception of moving objects. There are many types of moving objects, with different levels of complexity. For example, we can track the motion of a tiny ant changing its position over a period of time. Or we can determine the overall direction of motion of a swarm of bees despite the individual bees moving somewhat chaotically. We also need to be able to judge the motion of other people, for example, to notice pedestrians beside a road, relative to other moving objects within the visual scene. These three examples are types of motion with different complexities that can be explored using specific experimental tests in the laboratory.

In our latest publication, we explored whether healthy ageing alters the perception of different types of motion considering also the location within the visual field. We tested 20 younger and 20 older healthy controls using a battery of computerised tests as shown in the figure below. Using these type of patterns, we explored seven components of motion processing.

Example of three stimuli used in our experiment. A) Grating, B) Dots, C) Human walker made by dots with a rightwards direction.

Tasks included the minimum percentage of contrast required to correctly identify the direction of motion of a grating (motion contrast), the minimum speed at which the observer can still identify the direction of motion of a grating (speed), the minimum displacement of a patch of dots required to identify as motion (D_min), the lowest percentage required to perceive the overall direction of motion of a pattern of dots (i.e. translational: rightwards/leftwards and radial: expanding/contracting) and biological motion.

Motion contrast, speed, D_min and biological motion were the tasks affected by age. Symbols represent the mean and error bars 95% CI of the mean.

In addition, we explored the amount of time required to correctly identify the direction of motion of two grating sizes (large and small). This task allows the exploration of a perceptual analogue of neuronal “surround suppression”: larger high contrast stimuli take longer to detect when compared to smaller.

Older adults presented less suppression in central vision but higher in peripheral.

Our findings revealed that most of the age-related changes in the perception of motion, except for the perception of biological motion, occur in tasks with lower levels of complexity. The only task where there was a profound relative difference between central vision and peripheral vision in older adults (when compared to younger adults) was the surround suppression of motion task.

This research forms part of the PhD studies of Juan Sepulveda (pictured below, pink shirt). The paper can be accessed online here: https://jov.arvojournals.org/article.aspx?articleid=2766226

Part of this work was presented in 2019 at the Association for Research in Vision annual meeting in Vancouver, Canada.