Biology subjects

Scheer, I.

Publications and source records attributed to Scheer, I..

5 recordsLinked to original sources

bioRxiv2026

Proprioceptive Neurons in Somatosensory Cortex Implement Optimal State Estimation

While the primary somatosensory cortex (S1) is known to be essential for skilled limb movements, it remains unclear how distinct functional ensembles within its network uniquely contribute to motor control. By isolating a stable population of proprioceptive S1 neurons in layer 2/3, we demonstrate how their selective removal impacts goal-directed reaching. We found that following their microablation global reach kinematics remained stable, yet natural movement variability was reorganized. Trajectories became more spatially dispersed while simultaneously becoming more geometrically stereotyped. Through computational modeling, we show that this seemingly paradoxical increase in one form of variability alongside a reduction in another reflects a failure in optimal state estimation. In contrast, broad S1 lesions mask the unique contribution of this ensemble, revealing instead that cortical feedback is temporally phased, engaging during high-precision grasping and retrieval rather than initial reaching. These findings identify a functionally defined subset of cortical neurons as the biological substrate for a core postulate of optimal control theory, operating within a broader S1 circuit specialized for fine motor refinement.

neuroscience↗

bioRxiv2025

The olivocerebellar system differentially encodes the effect sensory events exert on behavior

Inferior olive neurons convey information about sensorimotor events via climbing fibers to the cerebellum, but their functional significance remains unclear. We directly imaged, with two-photon microscopy, climbing fiber axonal terminals in the cerebellum during a task that successively exposed mice to a force perturbation, a movement instruction and reward; each followed by multiple modes of motor activity. Climbing fiber activations by the sensory events were either generic or informative about the consequences the encoded event has on behavior. The number of informative cells and the information strength are regulated by event modality and functional complexity of the cells activity. We observed an additional, previously unreported activation of climbing fibers: they carried probabilistic information on the behavioral context during idle waiting periods preceding stimulus presentation. Our findings reveal properties of olivary neurons that are key for defining their function in the cerebellum-dependent control of behavior. They suggest that the inferior olive flexibly instructs the cerebellum of any process that may shape an animals action.

neuroscience↗

bioRxiv2022

Spatial encoding of forelimb proprioception in the mouse somatosensory cortex

Conscious perception of limb movements depends on proprioceptive neural responses in the somatosensory cortex. In contrast to tactile sensations, proprioceptive cortical coding is barely studied in the mammalian brain and practically non-existent in rodent research. To understand the cortical representation of this important sensory modality we developed a passive forelimb displacement paradigm in behaving mice and also trained them to perceptually discriminate where their limb is moved in space. We delineated, for the first time, the rodent proprioceptive cortex with wide-field calcium imaging and optogenetic silencing experiments during awake behavior. Our results reveal that proprioception is represented in both sensory and motor cortical areas. In addition, behavioral measurements and responses of layer 2/3 neurons imaged with two-photon microscopy reveal that passive limb movements are both perceived and encoded in the mouse cortex as a spatial direction vector that interfaces the limb with the bodys peripersonal space.

neuroscience↗

bioRxiv2017

Intra-voxel incoherent motion magnetic resonance imaging of the living human fetus: the technique and within-subject reproducibility

Our purpose was to test the within-subject repeatability of the perfusion fraction, diffusion coefficient and pseudo diffusion coefficient measurements in various fetal organs and in the placenta based on the intra-voxel incoherent motion imaging principle. In utero diffusion-weighted magnetic resonance imaging was performed on 1.5T and 3.0T clinical scanners with b-factors ranging from 0 to 900 s/mm2 in 16 steps and a tetrahedral diffusion-weighting encoding scheme. Data from 16 pregnant women (maternal age: 34 {+/-} 4.9 years, range: 24.6 -40.8) were included in this pilot study. For 15 cases, IVIM was repeated (maternal age: 33.7 {+/-} 5.2 years, range: 24.6 - 40.8). A bi-exponential model was fitted on the volume-averaged diffusion values and the perfusion fraction (f), diffusion coefficient (d) and pseudo diffusion coefficient (D*) were calculated. Within-subject repeatability was given as the test-retest variability of the IVIM parameters in the fetal frontal cortex, frontal white matter, cerebellum, lungs, kidneys, liver and in the placenta. An in-house developed image processing script was utilized to remove the image frames with excessive motion, and to perform motion correction by using non-linear freeform deformations. For the fetal lungs, liver and the placenta, within-subject variability ranged from 14.4% to 20.4% for f, 12.2% to 14.1% for d and 16.8% to 25.3% for D*. The diffusion coefficients of the investigated brain regions were moderately to highly reproducible (4.8% to 15.2%), however, f and D* showed inferior reproducibility compared to corresponding measures derived for the lungs, liver and placenta. The IVIM-based parameters of the fetal kidney were revealed to be highly variable across scans. Our results indicate that in utero intra-voxel incoherent motion magnetic resonance imaging potentially provides a novel method for examining microvascular perfusion and diffusion in the developing human fetus. The reproducible quantification of the perfusion and diffusion parameters depend greatly upon data quality, fetal and maternal movements, and image post processing to detect and remove corrupted data before calculating the IVIM model.

bioinformatics↗

bioRxiv2017

In Utero Diffusion Tensor Imaging Of The Fetal Brain: A Reproducibility Study

Our purpose was to evaluate the within-subject reproducibility of in utero diffusion tensor imaging (DTI) metrics and the visibility of major white matter structures.\n\nImages for 30 fetuses (20-33. postmenstrual weeks, normal neurodevelopment: 6 cases, cerebral pathology: 24 cases) were acquired on 1.5T or 3.0T MRI. DTI with 15 diffusion-weighting directions was repeated three times for each case, TR/TE: 2200/63 ms, voxel size: 1*1 mm, slice thickness: 3-5 mm, b-factor: 700 s/mm2. Reproducibility was evaluated from structure detectability, variability of DTI measures using the coefficient of variation (CV), image correlation and structural similarity across repeated scans for six selected structures. The effect of age, scanner type, presence of pathology was determined using Wilcoxon rank sum test.\n\nWhite matter structures were detectable in the following percentage of fetuses in at least two of the three repeated scans: corpus callosum genu 76%, splenium 64%, internal capsule, posterior limb 60%, brainstem fibers 40% and temporooccipital association pathways 60%. The mean CV of DTI metrics ranged between 3% and 14.6% and we measured higher reproducibility in fetuses with normal brain development. Head motion was negatively correlated with reproducibility, this effect was partially ameliorated by motion-correction algorithm using image registration. Structures on 3.0 T had higher variability both with- and without motion correction.\n\nFetal DTI is reproducible for projection and commissural bundles during mid-gestation, however, in 16-30% of the cases, data were corrupted by artifacts, resulting in impaired detection of white matter structures. To achieve robust results for the quantitative analysis of diffusivity and anisotropy values, fetal-specific image processing is recommended and repeated DTI is needed to ensure the detectability of fiber pathways.\n\nAbbreviations

neuroscience↗