Biology subjects

Saurels, B. W.

Publications and source records attributed to Saurels, B. W..

6 recordsLinked to original sources

bioRxiv2025

People report having consistent idiosyncratic diets of imagined sensations when they re-experience the past, and pre-experience the future

To some extent, humans can re-experience the sensations of past events and pre-experience the future. These capacities are inter-related. But there are substantial individual differences. At the extremes, small minorities of people report that they either cannot have imagined experiences at all, or that their imagined sensations are as real to them as their actual experiences of the physical world. We wanted to know if such individual differences are uniform across different types of imagined experience (e.g. vision, audio, taste and smell), or if people generally have idiosyncratic patterns of different types (vision, audio, taste and smell) of imagined experiences. We find that people report having idiosyncratic diets of different types of imagined sensation, characterised by differences in salience. One person might have more salient imagined visual than taste experiences, while another reports the reverse. Moreover, these propensities are consistent across peoples attempts to re-experience the past, and to pre-experience the future, and they predict peoples experience and usage of different types of imagined sensation in their everyday lives.

neuroscience↗

bioRxiv2025

Vividness of mental imagery is a broad trait measure of internally generated visual experiences

Research on mental visual imagery typically relies on vividness ratings. However, vividness is ill-defined as it lacks an objective reference. Here, we present survey results that suggest vividness is nevertheless a robust measure. It explains individual differences of a broad range of subjective experiences, from the detail of mental imagery, the propensity to report having other internally generated visual experiences, and the vividness of visual dreams. Critically, simple vividness ratings can replace the protracted questionnaires commonly used for this purpose and reduce methodological issues with these instruments. We further find that vividness is closely linked with the experience of "seeing" mental images or projecting them into the external world. People who report seeing mental images with their eyes shut are also more likely to experience externally projected imagery. Nevertheless, many people report having mental depictions but without seeing. Overall, our results indicate we should redefine visual aphantasia to distinguish individuals with faint or unseen visual images from those completely lacking a pictorial representation.

neuroscience↗

bioRxiv2024

Imagery priming of binocular rivalry is not a reliable metric of individual differences in the subjective vividness of visualisations.

Most people can imagine images that they experience within their minds eye. However, there are marked individual differences, with some people reporting that they are unable to construct mental images at all (aphantasics), and others who report having imagined experiences that are as realistic as seeing (hyper-phantasics). The vividness of imagined images is most often measured via subjective self-report. Chang and Pearson (2018), however, have suggested that a binocular rivalry (BR) protocol can be used as an objective measure. They found that pre-imagining a moving input could enhance performance on an objective probe detection task when probes were embedded in imagery consistent inputs, as opposed to imagery inconsistent inputs. To date, nobody has assessed if this type of objective imagery priming can be used to predict the vividness of different peoples visualisations. Here, we report that imagery priming of objective sensitivity to probes within static BR inputs does not correlate with the typical ratings people use to describe the vividness of their visualisations (a between participants effect). However, objective priming of sensitivity to probes embedded in BR inputs was greater on trials when participants reported that their pre-imagined experience had been relatively vivid (a within participants effect). Overall, our data suggest that while imagery can prime objective sensitivity to probes during BR, there is currently no strong evidence that this effect can be used as an objective method of predicting the subjective vividness of different peoples visualisations. Highlights[tpltrtarr] There are marked individual differences in the subjective intensity of visual imagery [tpltrtarr]Most measures of the subjective intensity of visual imagery are subjective [tpltrtarr]A binocular rivalry probe-detection protocol has been suggested as an objective measure [tpltrtarr]The authors find that there is only a very small predictive relationship between outcomes in a binocular rivalry task and participants reported imagery strength [tpltrtarr]We still lack an objective measure that reliably predicts the subjective intensity of visual imagery

animal behavior and cognition↗

bioRxiv2023

Predicting the subjective intensity of imagined sensory experiences from electrophysiological measures of oscillatory brain activity.

Most people can conjure images and sounds that they experience in their minds. There are, however, marked individual differences. Some people report that they cannot generate imagined sensory experiences at all (aphantasics) and others report that they have unusually intense imagined experiences (hyper-phantasics). These individual differences have been linked to activity in sensory brain regions, driven by feedback. We would therefore expect imagined experiences to be associated with specific frequencies of oscillatory brain activity, as these can be a hallmark of neural interactions within and across regions of the brain. Replicating a number of other studies, relative to meditation we find that the act of engaging in imagining auditory or visual sensations is linked to reductions in the power of oscillatory brain activity across a broad range of frequencies, with prominent peaks in the alpha band (8-12 Hz). This oscillatory activity, however, did not predict individual differences in the subjective intensity of imagined experiences. For imagined audio experiences, these were rather predicted by reductions within the theta (6 - 9 Hz) and gamma (33 - 38 Hz) bands, and by increases in beta (15 - 17Hz) band activity. For imagined visual experiences these were predicted by reductions in lower (14 - 16Hz) and upper (29 - 32 Hz) beta band activity, and by an increase in mid-beta band (24 - 26 Hz) activity. Our data suggest that there is sufficient ground truth to the subjective reports that people use to describe the intensity of their imagined sensory experiences such that these can be predicted by the power of distinct rhythms of brain activity.

neuroscience↗

bioRxiv2020

Are alpha-band oscillations a default dynamic of the human visual brain, or a product of ongoing visual processes?

One of the seminal findings of cognitive neuroscience is that the power of alpha-band ([~]10 Hz) brain waves, in occipital regions, increases when people close their eyes. This has encouraged the view that alpha oscillations are a default dynamic, to which the visual brain returns in the absence of input. Accordingly, we might be unable to increase the power of alpha oscillations when the eyes are closed, above the level that would usually ensue. Here we report counter evidence. We used electroencephalography (EEG) to record brain activity when people had their eyes open and closed, before and after they had adapted to radial motion. The increase in the power of alpha oscillations when people closed their eyes was enhanced by adaptation to a broad range of radial motion speeds. This effect was greatest for 10Hz motion, but robust for other frequencies, and specifically for 7.5Hz. This last observation is important, as it rules against an ongoing entrainment of activity, at the adaptation frequency, as an explanation for our results. Instead, our data show that visual processes remain active when people close their eyes, and these can be modulated by adaptation to increase the power of alpha oscillations in occipital brain regions.

neuroscience↗

bioRxiv2020

Visual predictions, neural oscillations and Newtonian physics.

Prediction is considered a core function of the human visual brain, but relating this suggestion to real life is problematic, as findings regarding the neural correlates of prediction rely on abstracted experiments, not reminiscent of a typical visual diet. We addressed this by having people view videos of basketball, and asking them to predict jump shot outcomes while we recorded eye movements and brain activity. We used the brains understanding of physics to manipulate predictive success, by inverting footage. People had enhanced alpha-band activity in occipital brain regions when watching upright videos, and this predicted both an increase in predictive success and enhanced ball tracking. Alpha-band activity in visual brain regions has been linked to inhibition, so we regard our results as evidence that inhibition of task irrelevant information is a core function of predictive processes in the visual brain, enacted as people complete visual tasks typical of daily life.

neuroscience↗