Biology subjects

Dakin, S. C.

Publications and source records attributed to Dakin, S. C..

4 recordsLinked to original sources

bioRxiv2025

Hemodynamic modelling improves population receptive field estimates

Population receptive field (pRF) modelling is a ubiquitous tool in sensory neuroscience for estimating the functional architecture of the human brain. Most pRF models assume a canonical hemodynamic response function (HRF) to account for neurovascular effects. But how does this assumption affect results in practice? Here, we concurrently fit the HRF within the pRF model. Using simulations, we demonstrate that this algorithm accurately estimated different ground truth HRFs used for synthesizing data. Moreover, concurrent fitting improves the accuracy of pRF estimates, especially for the complex Difference-of-Gaussian model. Next, we reanalyzed empirical datasets with different stimulus paradigms and scanning parameters. Concurrent fitting substantially reduced the proportion of implausibly small pRFs. Importantly, the best-fitting HRF differed substantially from canonical HRFs or from those measured independently. HRFs also peaked earlier in higher than early visual cortex, suggesting response nonlinearities. This variability need not only be hemodynamic but could result from neural factors. Critically, all these differences could produce spurious pRF estimates and alter the interpretation of reported findings.

neuroscience↗

bioRxiv2024

Retinotopic mapping data permit accurate matching of participants across different datasets

Public sharing of neuroimaging data is becoming increasingly common for the advancement and validation of scientific research. However, this sharing poses challenges regarding privacy and data safety, and associated questions about the ownership of research data. Here we show that a simple pattern correlation algorithm can match nominally deidentified participants across two separate functional magnetic resonance imaging (fMRI) experiments. This re-identification procedure is effective despite functional maps being spatially warped to a common template brain. This work highlights the need for appropriate safeguards against possible misuse of shared neuroimaging data.

neuroscience↗

bioRxiv2024

Spatial frequency adaptation modulates population receptive field sizes

The spatial tuning of neuronal populations in the early visual cortical regions is related to the spatial frequency (SF) selectivity of neurons. However, there has been no direct investigation into how this relationship is reflected in population receptive field (pRF) sizes despite the common application of pRF mapping in visual neuroscience. We hypothesised that adaptation to high/low SF would decrease the sensitivity of neurons with respectively small/large receptive field sizes, resulting in a change in pRF sizes as measured by functional magnetic resonance imaging (fMRI). To test this hypothesis, we first quantified the SF aftereffect using a psychophysical paradigm where observers made SF judgments following adaptation to high/low SF noise patterns. We then incorporated the same adaptation technique into a standard pRF mapping procedure, to investigate the spatial tuning of the early visual cortex following SF adaptation. Results showed that adaptation to a low/high SF resulted in smaller/larger pRFs respectively, as hypothesised. Our results provide the most direct evidence to date that the spatial tuning of the visual cortex, as measured by pRF mapping, is related to the SF selectivity of visual neural populations. This has implications for various domains of visual processing, including size perception and visual acuity.

neuroscience↗

bioRxiv2021

Balanced, Orientation-Dependent Dichoptic Masking in Cortex of Visually Normal Humans Measured Using Electroencephalography (EEG)

In the human visual system, cerebral cortex combines left- and right-eye retinal inputs, enabling single, comfortable binocular vision. In visual cortex, the signals from each eye inhibit one another (interocular suppression). While this mechanism may be disrupted by e.g. traumatic brain injury, clinical assessments of interocular suppression are subjective, qualitative, and lack reliability. EEG is a potentially useful clinical tool for objective, quantitative assessment of binocular vision. In a cohort of normal participants, we measured occipital, visual evoked potentials (VEPs) in response to dichoptically-presented vertical and/or horizontal sine-wave gratings. Response amplitudes to orthogonal gratings were greater than that of parallel gratings, which were in turn greater than that of monocular gratings. Our results indicate that interocular suppression is (normally) balanced, orientation-tuned, and that suppression per se is reduced for orthogonal gratings. This objective measure of suppression may have application in clinical settings.

neuroscience↗