Biology subjects

Schiller, J.

Publications and source records attributed to Schiller, J..

23 records · Page 2Linked to original sources

bioRxiv2020

Cell-type specific outcome representation in primary motor cortex

Adaptive movements are critical to animal survival. To guide future actions, the brain monitors different outcomes, including achievement of movement and appetitive goals. The nature of outcome signals and their neuronal and network realization in motor cortex (M1), which commands the performance of skilled movements, is largely unknown. Using a dexterity task, calcium imaging, optogenetic perturbations, and behavioral manipulations, we studied outcome signals in murine M1. We find two populations of layer 2-3 neurons, "success"- and "failure" related neurons that develop with training and report end-result of trials. In these neurons, prolonged responses were recorded after success or failure trials, independent of reward and kinematics. In contrast, the initial state of layer-5 pyramidal tract neurons contains a memory trace of the previous trials outcome. Inter-trial cortical activity was needed to learn new task requirements. These M1 reflective layer-specific performance outcome signals, can support reinforcement motor learning of skilled behavior.

neuroscience↗

bioRxiv2019

Stimjim: open source hardware for precise electrical stimulation

Electrical stimulation is a simple and powerful tool to perturb and evoke neuronal activity in order to understand the function of neurons and neural circuits. Despite this, devices that can provide precise current or voltage stimulation are expensive and closed-source. Here, we introduce Stimjim, a capable and inexpensive ($200 USD) open-source instrument for electrical stimulation that combines both function generation and electrical isolation. Stimjim provides microsecond temporal resolution with microampere or millivolt scale precision on two electrically isolated output channels. We demonstrate Stimjims utility both in vitro by precisely stimulating brain slices, and in vivo by training mice to perform intracranial self-stimulation (ICSS) for brain stimulation reward. During ICSS, Stimjim enables the experimenter to smoothly tune the strength of reward-seeking behavior by varying either the output frequency or amplitude. We envision Stimjim will enable new kinds of experiments due to its open-source and scalable nature.

neuroscience↗

bioRxiv2018

NMDA spikes mediate amplification of odor pathway information in the piriform cortex

The piriform cortex (PCx) receives direct input from the olfactory bulb (OB) and is the brains main station for odor recognition and memory. The transformation of the odor code from OB to PCx is profound: mitral and tufted cells in olfactory glomeruli respond to individual odorant molecules, whereas pyramidal neurons (PNs) in the PCx responds to multiple, apparently random combinations of activated glomeruli. How these \"discontinuous\" receptive fields are formed from OB inputs remains unknown. Counter to the prevailing view that olfactory PNs sum their inputs passively, we show for the first time that NMDA spikes within individual dendrites can both amplify OB inputs and impose combination selectivity upon them, while their ability to compartmentalize voltage signals allows different dendrites to represent different odorant combinations. Thus, the 2-layer integrative behavior of olfactory PN dendrites provides a parsimonious account for the nonlinear remapping of the odor code from bulb to cortex.

neuroscience↗

bioRxiv2018

Automated cellular structure extraction in biological images with applications to calcium imaging data

Recent advances in experimental methods in neuroscience enable measuring in-vivo activity of large populations of neurons at cellular level resolution. To leverage the full potential of these complex datasets and analyze the dynamics of individual neurons, it is essential to extract high-resolution regions of interest, while addressing demixing of overlapping spatial components and denoising of the temporal signal of each neuron. In this paper, we propose a data-driven solution to these challenges, by representing the spatiotemporal volume as a graph in the image plane. Based on the spectral embedding of this graph calculated across trials, we propose a new clustering method, Local Selective Spectral Clustering, capable of handling overlapping clusters and disregarding clutter. We also present a new nonlinear mapping which recovers the structural map of the neurons and dendrites, and global video denoising. We demonstrate our approach on in-vivo calcium imaging of neurons and apical dendrites, automatically extracting complex structures in the image domain, and denoising and demixing their time-traces.

neuroscience↗

bioRxiv2017

The fluid membrane determines mechanics of red blood cell extracellular vesicles and is softened in hereditary spherocytosis

Extracellular vesicles (EVs) are widely studied regarding their role in cell-to-cell communication and disease, as well as for applications as biomarker or drug delivery vehicle. EVs contain both membrane and intraluminal proteins, affecting their structural properties and thereby likely their functioning. Here, we use atomic force microscopy for the mechanical characterization of red blood cell (RBC) EVs from healthy individuals as well as from a patient with hereditary spherocytosis (HS) due to ankyrin deficiency. We show that the EVs are packed with proteins, yet their response to indentation is similar to that of a fluid lipid vesicle lacking proteins. The bending modulus of RBC EVs of healthy donors is ~15 kbT, agreeing well with the bending modulus of the RBC membrane. Surprisingly, whereas RBCs become more rigid in HS, the excreted vesicles of a patient with this blood disorder have a significantly (~50%) lower bending modulus than donor EVs. These results shed new light on the mechanism and effects of EV budding and may underlie the reported increase in vesiculation and stiffening of RBCs in hereditary spherocytosis patients.

biophysics↗