Biology subjects

Holcombe, A. O.

Publications and source records attributed to Holcombe, A. O..

6 recordsLinked to original sources

bioRxiv2024

No evidence that individual alpha frequency (IAF) represents a mechanism underlying motion-position illusions

Motion-Position Illusions (MPIs) involve the position of an object being misperceived in the context of motion (i.e. when the object contains motion, is surrounded by motion, or is moving). A popular MPI is the flash-lag effect, where a static object briefly presented in spatiotemporal alignment with a moving object, is perceived in a position behind the moving object. Recently, Cottier et al. (2023) observed that there are stable individual differences in the magnitude of these illusions, and possibly even their direction. To investigate the possible neural correlates of these individual differences, the present study explored whether a trait-like component of brain activity, individual alpha frequency (IAF), could predict individual illusion magnitude. Previous reports have found some correlations between IAF and perceptual tasks. Participants (N=61) viewed the flash-lag effect (motion and luminance), Frohlich effect, flash-drag effect, flash-grab effect, motion-induced position shift, twinkle-goes effect, and the flash-jump effect. In a separate session, five minutes of eyes-open and eyes-closed resting state EEG data was recorded. Correlation analyses revealed no evidence for a correlation between IAF and the magnitude of any MPIs. Overall, these results suggest that IAF does not represent a mechanism underlying MPIs, and that no single shared mechanism underlies these effects. This suggests that discrete sampling at alpha frequency is unlikely to be responsible for any of these illusions.

neuroscience↗

bioRxiv2022

Taxonomy of interventions at academic institutions to improve research quality

Research institutions and researchers have become increasingly concerned about poor research reproducibility and replicability, and research waste more broadly. Research institutions play an important role and understanding their intervention options is important. This review aims to identify and classify possible interventions to improve research quality, reduce waste, and improve reproducibility and replicability within research-performing institutions. Taxonomy development steps: 1) use of an exemplar paper of journal-level research quality improvement interventions, 2) 2-stage search in PubMed using seed and exemplar articles, and forward and backward citation searching to identify articles evaluating or describing research quality improvement, 3) elicited draft taxonomy feedback from researchers at an open-sciences conference workshop, and 4) cycles of revisions from the research team. The search identified 11 peer-reviewed articles on relevant interventions. Overall, 93 interventions were identified from peer-review literature and researcher reporting. Interventions covered before, during, and after study conduct research stages and whole of institution. Types of intervention included: Tools, Education & Training, Incentives, Modelling & Mentoring, Review & Feedback, Expert involvement, and Policies & Procedures. Identified areas for research institutions to focus on to improve research quality and for further research includes improving incentives to implement quality research practices, evaluating current interventions, encourage no- or low-cost/high-benefit interventions, examine institution research culture, and encourage mentor-mentee relationships.

scientific communication and education↗

bioRxiv2020

Hallucination of moving objects revealed by a dynamic noise background

We show that on a dynamic noise background, the perceived disappearance location of a moving object is shifted in the direction of motion. This "twinkle goes" illusion has little dependence on the luminance- or chromaticity-based confusability of the object with the background, or on the amount of background motion energy in the same direction as the object motion. This suggests that the illusion is enabled by the dynamic noise masking the offset transients that otherwise accompany an objects disappearance. While these results are consistent with an anticipatory process that pre-activates positions ahead of the objects current position, additional findings suggest an alternative account: a continuation of attentional tracking after the object disappears. First, the shift was greatly reduced when attention was divided between two moving objects. Second, the illusion was associated with a prolonging of the perceived duration of the object, by an amount that matched the extent of extrapolation inferred from the effect of speed on the size of the illusion (~50 ms). While the anticipatory extrapolation theory does not predict this, the continuation of attentional tracking theory does. Specifically, we propose that in the absence of offset transients, attentional tracking keeps moving for several tens of milliseconds after the target disappearance, and this causes one to hallucinate a moving object at the position of attention.

neuroscience↗

bioRxiv2020

Now you see it, now you don't: Overlapping neural representations for the position of visible and invisible objects

Humans can covertly track the position of an object, even if the object is temporarily occluded. What are the neural mechanisms underlying our capacity to track moving objects when there is no physical stimulus for the brain to track? One possibility is that the brain "fills-in" information about imagined objects using internally generated representations similar to those generated by feed-forward perceptual mechanisms. Alternatively, the brain might deploy a higher order mechanism, for example using an object tracking model that integrates visual signals and motion dynamics (Kwon et al., 2015). In the present study, we used electroencephalography (EEG) and time-resolved multivariate pattern analyses to investigate the spatial processing of visible and imagined objects. Participants tracked an object that moved in discrete steps around fixation, occupying six consecutive locations. They were asked to imagine that the object continued on the same trajectory after it disappeared and move their attention to the corresponding positions. Time-resolved decoding of EEG data revealed that the location of the visible stimuli could be decoded shortly after image onset, consistent with early retinotopic visual processes. For processing of unseen/imagined positions, the patterns of neural activity resembled stimulus-driven mid-level visual processes, but were detected earlier than perceptual mechanisms, implicating an anticipatory and more variable tracking mechanism. Encoding models revealed that spatial representations were much weaker for imagined than visible stimuli. Monitoring the position of imagined objects thus utilises similar perceptual and attentional processes as monitoring objects that are actually present, but with different temporal dynamics. These results indicate that internally generated representations rely on top-down processes, and their timing is influenced by the predictability of the stimulus. All data and analysis code for this study are available at https://osf.io/8v47t/.

neuroscience↗

bioRxiv2019

A delay in sampling information from temporally autocorrelated visual stimuli

Much of our world changes smoothly in time, yet the allocation of attention is typically studied with sudden changes - transients. When stimuli change gradually there is a sizeable lag between when a cue is presented and when an object is sampled (Carlson, Hogendoorn, & Verstraten, 2006; Sheth, Nijhawan & Shimojo, 2000). Yet this lag is not seen with rapid serial visual presentation (RSVP) stimuli where temporally uncorrelated stimuli are presented (Vul, Kanwisher & Nieuwenstein 2008; Goodbourn & Holcombe, 2015). These findings collectively suggest that temporal autocorrelation of a feature paradoxically increases the latency at which information is sampled. This hypothesis was tested by comparing stimuli changing smoothly in time (autocorrelated) to stimuli that change randomly. Participants attempted to report the color coincident with a visual cue. The result was a smaller selection lag for the randomly varying condition relative to the condition with a smooth color trajectory. Our third experiment finds that the increase in selection latency is due to the smoothness of the color change after the cue rather than extrapolated predictions based on the color changes presented before the cue. Together, these results support a theory of attentional drag, whereby attention remains engaged at a location longer when features are changing smoothly. A computational model provides insights into neural mechanisms that might underlie the effect.

neuroscience↗

bioRxiv2019

Attention updates the perceived position of moving objects

The information used by conscious perception may be somewhat different from that which drives certain actions. In support of this notion, recent studies reported that although internal grating motion can accumulate over seconds into a large illusory position shift, this position shift is not reflected in saccade targeting (action). Another possibility however is that rather than saccades and other actions having privileged access to the correct position, the attention shift thought to precede saccades resets the accumulated position shift to zero. Here we found that the accumulation of illusory position shift can be reset by transients near the moving object and also by the observer pressing a button at the time the object is perceived to reach a particular position. This creates a striking impression of the object jumping back to near its actual position. These results suggest that both stimulus-driven attention and attention associated with control of action may update the perceived position of moving objects and mediate the previously reported dissociation between conscious perception and saccades.

neuroscience↗