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tgastrell.bsky.social
Tim Gastrell
@tgastrell.bsky.social
64 followers 170 following 9 posts
Kiwi in QLD 🥝 Science nerd 🔭 Computer enjoyer 💻 PhD researcher in Cognitive/Computational Neuroscience 🧠 Studying how the brain leverages experience to support sensory processing and decision-making under uncertainty. Distractions encouraged.
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Reposted by Tim Gastrell
emilya-izzeddin.bsky.social
Emily A-Izzeddin @emilya-izzeddin.bsky.social · 1d
The final bit of work from my PhD just got published at JOV! We looked at similarity judgements made for naturalistic image patches, and whether these are predicted by simple image statistics… (spoiler: yep!)

Link to paper: doi.org/10.1167/jov....

1/11
Low-level features predict perceived similarity for naturalistic images | JOV | ARVO Journals
doi.org
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Reposted by Tim Gastrell
emilya-izzeddin.bsky.social
Emily A-Izzeddin @emilya-izzeddin.bsky.social · 10d
Just published some work at Scientific Reports! We investigated visual adaptation following free viewing of a film (Casablanca) that had its oriented contrast altered. To our surprise, we found adaptation effects to be pretty negligible…

www.nature.com/articles/s41...

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Investigating orientation adaptation following naturalistic film viewing - Scientific Reports
Scientific Reports - Investigating orientation adaptation following naturalistic film viewing
www.nature.com
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Reposted by Tim Gastrell
brainboyben.bsky.social
Benjamin Lowe @brainboyben.bsky.social · Aug 19
🚨Pre-print of some cool data from my PhD days!
doi.org/10.1101/2025...

☝️Did you know that visual surprise is (probably) a domain-general signal and/or operates at the object-level?
✌️Did you also know that the timing of this response depends on the specific attribute that violates an expectation?
The Latency of a Domain-General Visual Surprise Signal is Attribute Dependent
Predictions concerning upcoming visual input play a key role in resolving percepts. Sometimes input is surprising, under which circumstances the brain must calibrate erroneous predictions so that perc...
doi.org
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Reposted by Tim Gastrell
tararas.bsky.social
Tara Rasmussen @tararas.bsky.social · Jul 19
My final Registered Report from my PhD is now out in Cortex!
We investigated the role of dopamine & HD-tDCS in mind wandering & sustained attention. While stimulation had no effect, increasing dopamine reduced spontaneous thought and may protect against performance deficits. doi.org/10.1016/j.co...
On the neural substrates of mind wandering and dynamic thought: A drug and brain stimulation study
The impact of mind wandering on our daily lives ranges from diminishing productivity, to facilitating creativity and problem solving. There is evidenc…
www.sciencedirect.com
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Reposted by Tim Gastrell
brainboyben.bsky.social
Benjamin Lowe @brainboyben.bsky.social · Jul 15
I really like this paper. I fear that people think the authors are claiming that the brain isn’t predictive though, which this study cannot (and does not) address. As the title says, the data purely show that evoked responses are not necessarily prediction errors, which makes sense!
tyrellturing.bsky.social
Blake Richards @tyrellturing.bsky.social · Jul 11
1/3) This may be a very important paper, it suggests that there are no prediction error encoding neurons in sensory areas of cortex:

www.biorxiv.org/content/10.1...

I personally am a big fan of the idea that cortical regions (allo and neo) are doing sequence prediction.

But...

🧠📈 🧪
Sensory responses of visual cortical neurons are not prediction errors
Predictive coding is theorized to be a ubiquitous cortical process to explain sensory responses. It asserts that the brain continuously predicts sensory information and imposes those predictions on lo...
www.biorxiv.org
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tgastrell.bsky.social
Tim Gastrell @tgastrell.bsky.social · Jul 18
Well said. Love this take.
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tgastrell.bsky.social
Tim Gastrell @tgastrell.bsky.social · Jun 20
Excited to be presenting behavioral and modeling work looking at perceptual decision making under uncertainty with recently learned priors at the EPC/APCV joint meeting today at UNSW, Sydney!

Catch me at 2:45pm in Gallery 1!

@expsyanz.bsky.social

#epc2025
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tgastrell.bsky.social
Tim Gastrell @tgastrell.bsky.social · Jun 4
5/5 So the mystery of mechanism remains, but the take home message is this:

Visual awareness is not just about the integration of stimulus history with stimulus content - visual field location matters as well!

OA paper (Gastrell et al., 2025, Journal of Vision): 🔗 doi.org/10.1167/jov....
Fixation versus periphery in visual awareness: Differential effects of recent perceptual experience | JOV | ARVO Journals
doi.org
tgastrell.bsky.social
Tim Gastrell @tgastrell.bsky.social · Jun 4
4/5 Next, we asked whether differences in fixational stability between foveal and peripheral viewing might drive the effect?

In a 4th Exp., we replicated the original effect *again* (so this really IS a thing!), but spatial differences in fixational stability did not correlate either.
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tgastrell.bsky.social
Tim Gastrell @tgastrell.bsky.social · Jun 4
3/5 We now knew this was a low-level (spatially specific) effect, so in Exp. 3 we replicated it, and also probed motion adaptation - a likely mechanism.

We found that adaptation to our unambiguous prime generated stronger motion after effects in the periphery, but didn't predict SFM effect! 🤯
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tgastrell.bsky.social
Tim Gastrell @tgastrell.bsky.social · Jun 4
2/5 In Exp. 2 we abolished the effect by moving the stimulus between v.f. locations as it changed from unambiguous to ambiguous motion.

This ruled out a high-level (non-retinotopic) visual explanation whereby the influence of a prime on object-level representations might depend on its precision.
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tgastrell.bsky.social
Tim Gastrell @tgastrell.bsky.social · Jun 4
1/5 Using unambiguous → ambiguous SFM sequences, we tested whether priming effects on perception of bistable structure from motion vary between fixation and the periphery.

In Exp. 1 we show that immediate perception of a target is more biased towards primes when sequences are fixated v peripheral.
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tgastrell.bsky.social
Tim Gastrell @tgastrell.bsky.social · Jun 4
New paper @ JOV!

With Matt Oxner, Frank Schumann and David Carmel.

🧠 Perception of ambiguous motion is shaped by recent visual experience - but does this differ across the visual field?

Yes!

Full open access paper here (Gastrell et al., 2025, Journal of Vision): 🔗 doi.org/10.1167/jov....

🧵
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Reposted by Tim Gastrell
nkgarg.bsky.social
Nikhil Garg @nkgarg.bsky.social · Mar 10
*Please repost* @sjgreenwood.bsky.social and I just launched a new personalized feed (*please pin*) that we hope will become a "must use" for #academicsky. The feed shows posts about papers filtered by *your* follower network. It's become my default Bluesky experience bsky.app/profile/pape...
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Reposted by Tim Gastrell
jorge-morales.bsky.social
Jorge Morales @jorge-morales.bsky.social · Mar 17
William James's take on psychophysics is *incredible*. Worth reading the whole quote. #psychSciSky #philsky #VisionScience

"But psychology is passing into a less simple phase. Within a few years what one may call a microscopic psychology has arisen in Germany, carried on by experimental methods,
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Reposted by Tim Gastrell
zoelittle.bsky.social
Zoë Little @zoelittle.bsky.social · Mar 8
Out now in AP&P!
jsaito25.bsky.social
Joey Saito @jsaito25.bsky.social · Mar 7
Effects of perceptual and decisional uncertainty on serial dependence in orientation perception
link.springer.com/article/10.3...
Effects of perceptual and decisional uncertainty on serial dependence in orientation perception - Attention, Perception, & Psychophysics
Where assimilative serial dependence occurs in perception, responses to visual attributes such as orientation are typically biased towards the attributes of visual stimuli seen in the recent past. Ser...
link.springer.com
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Reposted by Tim Gastrell
sbmost.bsky.social
Steve Most @sbmost.bsky.social · Jan 31
Cognitive psych is often traced back to the 1950s.
Psychology is often traced to Wundt's lab in 1879.
Textbooks speak of "proto-psychologists" like Fechner & Helmholtz in the 1800s... Westerners all.

Have you heard about Ibn al-Haytham, whose work predated them by 100s of years?

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Reposted by Tim Gastrell
joemelling.bsky.social
Joe Melling @joemelling.bsky.social · Nov 16
Excited to share my first paper: a novel visual illusion discovered by my co-authors Will Turner and Hinze Hogendoorn which we call the "Split-Stimulus Effect", in which a single flashed stimulus is perceived to be in two different locations simultaneously jov.arvojournals.org/article.aspx... [1/5]
Concurrent perception of competing predictions: A “split-stimulus effect” | JOV | ARVO Journals
jov.arvojournals.org
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Reposted by Tim Gastrell
willjharrison.bsky.social
Will Harrison @willjharrison.bsky.social · Jan 29
New from my lab: "Priors for natural image statistics inform confidence in perceptual decisions"

We used a natural image statistics approach to investigate the computations underlying perceptual confidence. 🧵

Article: www.sciencedirect.com/science/arti...
A scientific image showing an original image (grayscale dog), the same image after processing with oriented edge filters, and then the spectral power as a function of orientation.
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Reposted by Tim Gastrell
arc-tracker.bsky.social
ARC Tracker @arc-tracker.bsky.social · Jan 16
“The PhD stipend is $33,511 … well below minimum wage of $47,627”

“Universities can raise the stipend to a maximum of $52,352, but a ACGR survey found none have done so. The highest stipend is just over $40,000 … with the average at $34,244.”

#RaiseTheStipend
PhD student Jesse Gardner-Russell earns $20 an hour. Experts say low pay is turning Australia’s best and brightest away
The University of Melbourne student whose work could contribute to curing blindness says ‘people are shocked to find out how unlivable it is’
www.theguardian.com
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Reposted by Tim Gastrell
neuronomist.bsky.social
Dragan Rangelov @neuronomist.bsky.social · Jan 6
🖨️ Fresh off the press! www.sciencedirect.com/science/arti...
We have shown that the brain processes visual input differently as a function of display density, violating predictions of dominant cognitive control theories.
Prefrontal dimension change-related activation differs for visual search in sparse and dense displays
Changes of the target-defining feature dimension have previously been shown to elicit anterior prefrontal activation increases. In the majority of stu…
www.sciencedirect.com
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Reposted by Tim Gastrell
marlenecohen.bsky.social
Marlene Cohen @marlenecohen.bsky.social · Jan 4
New results for a new year! “Linking neural population formatting to function” describes our modern take on an old question: how can we understand the contribution of a brain area to behavior?
www.biorxiv.org/content/10.1...
🧠👩🏻‍🔬🧪🧵
#neuroskyence
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Linking neural population formatting to function
Animals capable of complex behaviors tend to have more distinct brain areas than simpler organisms, and artificial networks that perform many tasks tend to self-organize into modules (1-3). This sugge...
www.biorxiv.org
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Reposted by Tim Gastrell
psyarxivbot.bsky.social
PsyArXivBot @psyarxivbot.bsky.social · Jan 1
Conscious awareness, sensory integration, and evidence accumulation in bodily self-perception: http://osf.io/e6tdy/
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Reposted by Tim Gastrell
tomerullman.bsky.social
Tomer Ullman @tomerullman.bsky.social · Dec 19
"The Illusion-Illusion: Vision Language Models See
Illusions Where There are None"

osf.io/preprints/ps...

(this is a more systematic examination of the thing I was looking at a few days ago)
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Reposted by Tim Gastrell
xkcd.com
Randall Munroe @xkcd.com · Dec 16
Phase Transition xkcd.com/3025
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