Biology subjects

Schluppeck, D.

Publications and source records attributed to Schluppeck, D..

4 recordsLinked to original sources

bioRxiv2026

Frequency magnification in human primary auditory cortex nearly predicts behavioural frequency hyperacuity

The auditory system decomposes sounds into different frequencies, but does not represent them equally: in the human cochlea, lower frequencies occupy a larger spatial extent than higher frequencies, creating a quasi-logarithmic frequency map with finer low-frequency resolution. It remains unclear whether the primary auditory cortex preserves this quasi-logarithmic frequency mapping, or further magnifies behaviourally relevant frequencies, analogous to the foveal over-magnification in primary visual cortex that is thought to underpin visual hyperacuity phenomena such as Vernier acuity. Here, we used ultra-high field functional magnetic resonance imaging to quantify frequency magnification in the primary auditory cortex of 20 human listeners. We compared cortical frequency magnification to predictions based on published estimates of either cochlear frequency resolution or behavioural frequency discrimination performance, a form of perceptual frequency hyperacuity. Cortical frequency magnification was better predicted by frequency discrimination performance than by cochlear frequency resolution, with an additional unexpected over-representation of frequencies around 1 kHz. These findings suggest that frequency discrimination is constrained by cortical processes rather than by frequency information available at the cochlea, consistent with similar observations in the visual and tactile systems.

neuroscience↗

bioRxiv2025

Assessing the digit organisation of focal hand dystonia using 7T functional MRI

IntroductionFocal hand dystonia (FHD) is typically treated with Botulinum Toxin (BTX/BoNT-A/Botox/ Onabotulinum Toxin Type A) injected into digit and wrist muscles to provide temporary symptomatic relief from muscle spasm. We use 7T functional MRI (fMRI) to study 1) differences in somatosensory and motor cortical digit maps between FHD patients and age and sex-matched healthy volunteers (HV), 2) changes in cortical digit maps of FHD patients after BTX treatment. MethodsFour FHD patients underwent behavioural measures and 7T fMRI at two timepoints: [~]30 days after BTX treatment at peak efficacy (Post-BTX), immediately prior to their next injection [~]100 days after treatment when therapeutic effects had declined (Pre-BTX). HVs were scanned at a single time point. Behavioural measures included temporal discrimination (TDT), amplitude thresholding (AMP) and spatial acuity grating orientation tasks. A somatosensory travelling wave (TW) digit-mapping fMRI task was performed on dominant/affected and non-dominant/un-affected hands, and a motor TW digit-mapping task on the dominant/affected hand. Fourier analysis derived digit maps which were compared to a probabilistic digit atlas, and population receptive field (pRF) mapping performed. Structural and resting state fMRI data were acquired. ResultsSpatial acuity was lowered in the dominant/affected hand in FHD compared to HVs, while TDT and AMP measures showed no significant differences. Somatosensory and motor TW cortical digit maps in FHD and HV showed clear digit ordering. Somatosensory and motor cortical digit maps were more disordered in the dominant/affected hand than the non-dominant hand for FHD Post and Pre-BTX compared to HVs (DICE coefficient/Figure of Merit). Compared to the atlas, HV maps were in-line for both hands, while in FHD central tendency (CT) was lower in the dominant/affected hand than non-dominant hand. pRF sizes were larger in the FHD Pre-BTX group compared to HV and Post-BTX for the dominant hand. ConclusionBehaviourally, FHD patients had lower spatial acuity than HVs. FHD digit maps had typical D1-D5 ordering, but DICE coefficients identified a disordered dominant hand in FHD patients compared to HVs at both timepoints. The FHD Pre-BTX group had larger pRF sizes than Post-BTX and HVs, suggesting BTX treatment coincides with more localised touch perception.

neuroscience↗

bioRxiv2022

Fast event-related mapping of fingertip population receptive fields in human somatosensory and motor cortex

fMRI studies that investigate somatotopic tactile representations in the human cortex typically use either block or phase-encoded stimulation designs. Event-related (ER) designs allow for more flexible and unpredictable stimulation sequences than the other methods, but they are less efficient. Here we compared an efficiency-optimized fast ER design (2.8s average intertrial interval, ITI) to a conventional slow ER design (8s average ITI) for mapping voxelwise fingertip tactile tuning properties in the sensorimotor cortex of 6 participants at 7 Tesla. The fast ER design yielded more reliable responses compared to the slow ER design, but with otherwise similar tuning properties. Concatenating the fast and slow ER data, we demonstrate in each individual brain the existence of two separate somatotopically-organized tactile representations of the fingertips, one in the primary somatosensory cortex (S1) on the post-central gyrus, and the other shared across the motor and pre-motor cortices on the pre-central gyrus. In both S1 and motor representations, fingertip selectivity decreased progressively, from narrowly-tuned Brodmann areas 3b and 4a respectively, towards associative parietal and frontal regions that responded equally to all fingertips, suggesting increasing information integration along these two pathways. In addition, fingertip selectivity in S1 decreased from the cortical representation of the thumb to that of the pinky. Significance StatementSensory and motor cortices in the human brain contain map-like representations of the body in which adjacent brain regions respond to adjacent body parts. The properties of these somatotopic maps provide important insight into how tactile and motor information is processed by the brain. Here, we describe an efficient mapping method using functional MRI to measure somatotopic maps and their tuning properties. We used a fast event-related sequence to map the five fingers of the left hand in six human participants, and show that this method is more efficient than a conventional, slower event-related design. Furthermore, we confirm previously-identified tuning properties of fingertip representations in somatosensory cortex, and reveal a hitherto unknown tactile fingertip map in the motor cortex.

neuroscience↗

bioRxiv2017

Geospatial statistics of high field functional MRI reveal topographical clustering for binocular stereo depth in early visual cortex

Significance statementFunctional topography is present throughout the cerebral cortex, often in the form of columns or clusters of neurons with similar functional properties within identified cortical regions. Most of the evidence for these structures comes from work with non-human species. Using high-field strength magnetic resonance imaging in living human cortex, the search for this structure is frustrated by the presence of a background of local spatial correlations in the signal across the cortical surface. This structured background, which we term neural dust, is a form of noise that imposes a fundamental limit on the detection of clustering and topography. We apply a novel analysis approach that quantifies the background of spatial correlations, so that we achieve reliable identification of high-signal clusters of activation in the human cortex at a scale previously only visible with invasive optical imaging in animals. We searched specifically in visual cortex for correlates of binocular stereoscopic depth. We show both that signals for stereoscopic depth are clustered into specific zones within the cortex and that these signals occur within spatially extended cortical domains, which have similar preferences for the stereoscopic depth. The revealed structures are reliably identified in all subjects tested and in repeated testing of individual subjects. Our methods provide an objective approach for defining the size and locations of clusters of activation within functional images of neural activity.\n\nAbstractA characteristic principle of the organization of cerebral neocortex is the presence of clusters or columns of neurons with similar functional properties. Animals with forward-facing eyes exploit slight differences between the images in the two eyes to determine binocular depth using stereopsis. Evidence for an organized structure in human visual cortex for the representation of stereoscopic depth has proved elusive. Using 7-tesla functional MRI, with gradient-echo echo-planar imaging at 0.75 mm isotropic resolution and a novel analytical approach based on geospatial mapping methods, we find that clustered responses for disparity-defined depth can be clearly segregated from a background of spatially correlated signals in all subjects tested. High-signal clusters are associated with cortical domains as large as 12-15mm across the cortical surface, in which nearby points in the cortical map tend to respond to the same stereoscopic depth. These domains are found predominantly within visual cortical area V3A.

neuroscience↗