It’s graduation time!

Last week a long-standing member of our lab, Dr Nikki Rubinstein, graduated with her PhD. Here is a bit about the research Nikki conducted over 4 years (minus 15 minutes):

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Nikki and Allison at Nikki’s graduation

Eye diseases such as glaucoma affect peripheral vision (aka side vision), while leaving central vision (used for reading) largely intact. The integrity of a person’s peripheral vision is measured clinically using a visual field machine: observers stare into a bowl and respond each time they see a dim light presented. The order and brightness levels of the light presentations is determined by an algorithm.

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A schematic of peripheral vision loss

During her PhD, Nikki developed new visual field algorithms in an attempt to reduce test time and test variability. One such algorithm, SWeLZ, reduced test times by approximately 25% in normally sighted observers. A variant of this algorithm has been implemented in the IMO head-mounted visual field machine in Japan.

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Observer sitting a visual field test

Nikki also investigated the limitations of interpreting visual field test results. Different observers have varying criteria for how bright a light needs to be before they respond. Nikki showed that the effect of this variability in response criterion makes it difficult to directly link visual field test results to underlying physiological changes.

We wish Nikki all the best in her future endeavours!

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Department of Optometry and Vision Sciences students celebrate with Nikki at her graduation

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SEMO 2018: 15th Scientific & 9th Educators meeting in optometry

The 15th Scientific & 9th Educators meeting in optometry was recently held in Melbourne on April 5th and 6th, and reunited optometrists, researchers and students from many universities across Australia and New Zealand.

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Attendees from CPU lab

The meeting was organized collaboratively between the Department of Optometry and Vision Sciences of the University of Melbourne and the Optometry division within the School of Medicine of Deakin University. The location for this meeting was at Deakin Downtown campus, in Melbourne CBD.

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Rekha and Juan were in charge of reception and registration

Presentations by the Clinical Psychophysics unit included the following talks:

Bao Nguyen: “Acute caffeine ingestion affects surround suppression of perceived contrast”

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Dr. Bao Nguyen, assisted by baby, presenting the effects of caffeine in surround suppression of perceived contrast

Janet Chan: “Elevated cortical GABA levels and stronger perceptual suppression with increasing days post-migraine”

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Dr. Janet Chan talking about cortical GABA levels and perceptual suppression after migraine

In poster format, Chongyue He presented her work called “The effects of luminance profile type on the strength of the Fraser-Wilcox illusion”

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Chongyue giving her 3 minutes poster introduction before poster session

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Chongyue and her poster showing the effects of luminance profile type on the strength of the Fraser-Wilcox illusion

The first day finished with a dinner at The General Assembly, a very beautiful place beside the Yarra river

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Allison greeting the attendees during the dinner

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The birthday boys: David Atchison and Juan

The next SEMO meeting will be held on 2020, in Auckland, New Zealand

 

2018 CPU ongoing research

After a while without posting, we are back. In this post we are presenting the current research areas and the new members of the Clinical Psychophysics Unit.

Current research areas

Our lab has interest in the following research areas:

  1. Effects of ageing on normal visual processing
  2. Effects of diseases such as glaucoma and migraine on visual processing
  3. Development of better clinical tests for the assessment of vision loss (such as visual field testing and ocular imaging)
  4. Study of the consequences of vision loss on performance in natural visual environments and day-to-day tasks
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CPU Lab retreat 2017

Current research projects ongoing within the Clinical Psychophysics unit

Our research projects include:

  1. Developing novel techniques and algorithms to assess the visual field, both functionally and anatomically using OCT. Students/researchers involved are Vasanth Muthusamy, Rekha Srinivasan, Virginia Liu and Professor Andrew Turpin from the School of Computing and Information Systems at the University of Melbourne
  2. Study of visual perception in migraine. Students/researchers involved are Chongyue He, Bao NguyenJanet Chan
  3. Study of changes in vision due to normal ageing, and how these may affect every day tasks such as driving. Students/researchers involved are Menaka Malavita, Juan Sepulveda, Soa Park, Janet Chan and Bao Nguyen.
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Some of the CPU lab members at the recent SEMO conference (Melbourne 2018)

 

Newly published: Neurochemical levels in the visual brain of older adults

Neurotransmitters are chemical messengers that are abundant in our brains and are responsible for communicating information throughout the nervous system. One key neurotransmitter, called gamma aminobutyric acid (or GABA), is critical for normal function of our visual system. GABA is an inhibitory neurotransmitter, which reduces rather than augments nerve impulses.

In the past there have been reports of healthy ageing being associated with changes in visual perception that are attributed to impaired GABAergic inhibition in the visual part of the brain. There are also suggestions from non-human primate studies of the visual cortex that ageing is associated with reduced GABA levels. However, no studies have directly measured GABA levels in the visual cortex of older humans.

In collaboration with colleagues at the Monash Biomedical Imaging facility of Monash University, we used a technique called magnetic resonance spectroscopy to measure neurotransmitter levels in the brains of older and younger adults. Magnetic resonance spectroscopy allows us to non-invasively compare the chemical composition of different parts of the brain. We found increased levels of GABA in the visual cortex in the older adults (see left hand side of Figure), but no changes in a non-visual part of the brain (dorsolateral prefrontal cortex, see right hand side of Figure). Furthermore, performance on two visual tasks that are considered measures of perceptual suppression (or inhibition), was correlated with GABA levels in the visual brain. These results challenge prior assumptions about how GABA is altered with healthy ageing.

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Above: GABA levels are increased in the visual cortex of older adults relative to younger adults, but no difference was observed in a non-visual part of the brain (dorsolateral prefrontal cortex, or DLPFC).

You can read the full article at Scientific Reports here.

Lab retreat 2017: Wilson’s Promontory

On a weekend in August our lab went on a winter retreat down at Wilson’s Promontory, the southernmost tip of mainland Australia. Fortunately the bucketing rain in Melbourne did not follow us south, and we enjoyed spectacular winter weather at ‘The Prom’.

Highlights of our trip include:

  • Spotting wombats in the national park
  • Dipping our feet into the (freezing) water at Squeaky Beach
  • Gas heated accommodation at the Tidal River huts
  • Short walks near Tidal River (Squeaky Beach track, Pillar Point, Loo Errn track)
  • Dinner, drinks and games and a big breakfast
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Part of the coastline at Wilson’s Promontory (Photo credit: Juan Sepulveda)

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On the Tidal River footbridge before heading on the Squeaky Beach walking track (Photo credit: Chongyue He)

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At Squeaky Beach (Photo credit: Chongyue He)

Latest lab celebrations and farewells

As we wrote previously in our lab blog, Nikki successfully submitted her PhD thesis within minutes of her 4-year deadline. It had been promised to Nikki that if she submitted her thesis before the 4 year due date, Allison and Andrew would throw a party in her honour. So this is how our lab ended up having a lab celebration party in July. It was also a party for Cassie and Kabilan who submitted their Masters and PhD theses, respectively.

The party was a chance to have some food and drink together, and to demonstrate our competitive spirits in a group scavenger hunt around the University of Melbourne. In order to gain points on the hunt, we circled the University campus, high-fived random strangers, took endless selfies at commemorative statues, tracked down obscure signs and patted dogs (real or not) along the way, while Allison tracked our progress in real time from the comfort of her desk. Thanks to Allison and Andrew for organising a fun way to get to know our work environment better!

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Above: Kabilan holding the traditional PhD submission balloon at the 1888 building, University of Melbourne. Below: Evidence of our scavenger hunt tasks

Later that week, it was time to farewell Astrid and Kabilan, who have both left our lab to start new projects in Europe. Astrid has relocated to Belgium to begin the next stage of her career, and Kabilan will soon start his first postdoctoral position working in Hamburg, Germany. We wish both of you all the best in your future projects!

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Astrid and Kabilan at Tsubu farewell drinks

 

 

Judging the timing of sight and sound: differences between older and younger adults

Our environment often contains visual and auditory information originating from separate events. Our brains need to be able to combine related sensory information coming from the same event and separate unrelated information from different events. One of the few common approaches to investigate such behaviour in human observers is known as audiovisual synchrony judgement: visual and auditory stimuli are presented at the same time or at some time offset from each other. Observers judge whether each stimulus pair is perceived as occurring at the same time (synchronous) or at different times (asynchronous). Previous work in our lab has shown that older adults are more likely to perceive asynchronous pairs as synchronous – i.e. older adults are more likely to incorrectly combine unrelated sensory information. How then does this reflect in the underlying brain processes involved in multisensory combination?

In this newly published study, we evaluated the impact of healthy ageing on the brain processes underlying audiovisual synchrony judgement using electroencephalography (EEG). EEG is used to measure brain activity in response to a stimulus (in this case, visual and auditory information). In the particular task used in this study, older and younger adults performed the same perceptually, but older adults recruited more widespread brain areas (specifically fronto-polar and frontal regions) to maintain the similar level of performance (see Figure 1 below).

 

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Figure 1: EEG activity indicating more widespread brain areas recruited by the older adults (bottom panel) to perform the audiovisual synchrony judgement task for synchronous pairs as compared to younger adults (top panel). A similar finding was also found for asynchronous audiovisual pairs (see published paper for details). Figure adapted from Figures 3 and 4 of Chan, Pianta, Bode & McKendrick (2017).

 

This work has been published in the journal Neurobiology of Aging (click here to view the abstract). A full copy of the paper can be requested by contacting Allison at allisonm@unimelb.edu.au