Combined Voltage and Calcium Epifluorescence Imaging In Vitro and In Vivo Reveals Subthreshold and Suprathreshold Dynamics of Mouse Barrel Cortex

2007 ◽  
Vol 97 (5) ◽  
pp. 3751-3762 ◽  
Author(s):  
Thomas Berger ◽  
Aren Borgdorff ◽  
Sylvain Crochet ◽  
Florian B. Neubauer ◽  
Sandrine Lefort ◽  
...  
Keyword(s):  
Barrel Cortex ◽  
Imaging Techniques ◽  
Receptive Fields ◽  
Cortical Function ◽  
Action Potential Firing ◽  
Spatiotemporal Resolution ◽  
Optical Signals ◽  
Potential Firing

Cortical dynamics can be imaged at high spatiotemporal resolution with voltage-sensitive dyes (VSDs) and calcium-sensitive dyes (CaSDs). We combined these two imaging techniques using epifluorescence optics together with whole cell recordings to measure the spatiotemporal dynamics of activity in the mouse somatosensory barrel cortex in vitro and in the supragranular layers in vivo. The two optical signals reported distinct aspects of cortical function. VSD fluorescence varied linearly with membrane potential and was dominated by subthreshold postsynaptic potentials, whereas the CaSD signal predominantly reflected local action potential firing. Combining VSDs and CaSDs allowed us to monitor the synaptic drive and the spiking activity of a given area at the same time in the same preparation. The spatial extent of the two dye signals was different, with VSD signals spreading further than CaSD signals, reflecting broad subthreshold and narrow suprathreshold receptive fields. Importantly, the signals from the dyes were differentially affected by pharmacological manipulations, stimulation strength, and depth of isoflurane anesthesia. Combined VSD and CaSD measurements can therefore be used to specify the temporal and spatial relationships between subthreshold and suprathreshold activity of the neocortex.

scholarly journals The thalamic low-threshold Ca 2+ potential: a key determinant of the local and global dynamics of the slow (<1 Hz) sleep oscillation in thalamocortical networks

2011 ◽  
Vol 369 (1952) ◽  
pp. 3820-3839 ◽  
Author(s):  
Vincenzo Crunelli ◽  
Adam C. Errington ◽  
Stuart W. Hughes ◽  
Tibor I. Tóth
Keyword(s):  
Action Potential ◽  
Slow Oscillation ◽  
Global Dynamics ◽  
Action Potential Firing ◽  
Local And Global Dynamics ◽  
Up States ◽  
Potential Firing ◽  
Low Threshold

During non-rapid eye movement sleep and certain types of anaesthesia, neurons in the neocortex and thalamus exhibit a distinctive slow (<1 Hz) oscillation that consists of alternating UP and DOWN membrane potential states and which correlates with a pronounced slow (<1 Hz) rhythm in the electroencephalogram. While several studies have claimed that the slow oscillation is generated exclusively in neocortical networks and then transmitted to other brain areas, substantial evidence exists to suggest that the full expression of the slow oscillation in an intact thalamocortical (TC) network requires the balanced interaction of oscillator systems in both the neocortex and thalamus. Within such a scenario, we have previously argued that the powerful low-threshold Ca 2+ potential (LTCP)-mediated burst of action potentials that initiates the UP states in individual TC neurons may be a vital signal for instigating UP states in related cortical areas. To investigate these issues we constructed a computational model of the TC network which encompasses the important known aspects of the slow oscillation that have been garnered from earlier in vivo and in vitro experiments. Using this model we confirm that the overall expression of the slow oscillation is intricately reliant on intact connections between the thalamus and the cortex. In particular, we demonstrate that UP state-related LTCP-mediated bursts in TC neurons are proficient in triggering synchronous UP states in cortical networks, thereby bringing about a synchronous slow oscillation in the whole network. The importance of LTCP-mediated action potential bursts in the slow oscillation is also underlined by the observation that their associated dendritic Ca 2+ signals are the only ones that inform corticothalamic synapses of the TC neuron output, since they, but not those elicited by tonic action potential firing, reach the distal dendritic sites where these synapses are located.

scholarly journals A Membrane-Targeted Photoswitch Potently Modulates Neuronal Firing

2019 ◽  
Author(s):  
Mattia L. DiFrancesco ◽  
Francesco Lodola ◽  
Elisabetta Colombo ◽  
Luca Maragliano ◽  
Giuseppe M. Paternò ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Neural Activity ◽  
Neuronal Firing ◽  
Physiological Effects ◽  
Action Potential Firing ◽  
Polar Groups ◽  
Potential Firing ◽  
Spatio Temporal

ABSTRACTOptical technologies allowing modulation of neuronal activity at high spatio-temporal resolution are becoming paramount in neuroscience. We engineered novel light-sensitive molecules by adding polar groups to a hydrophobic backbone containing azobenzene and azepane moieties. We demonstrate that the probes stably partition into the plasma membrane, with affinity for lipid rafts, and cause thinning of the bilayer through their trans-dimerization in the dark. In neurons pulse-labeled with the compound, light induces a transient hyperpolarization followed by a delayed depolarization that triggers action potential firing. The fast hyperpolarization is attributable to a light-dependent decrease in capacitance due to membrane relaxation that follows disruption of the azobenzene dimers. The physiological effects are persistent and can be evoked in vivo after labeling the mouse somatosensory cortex. These data demonstrate the possibility to trigger neural activity in vitro and in vivo by modulating membrane capacitance, without directly affecting ion channels or local temperature.

Independent Neuronal Oscillators of the Rat Globus Pallidus

2003 ◽  
Vol 89 (3) ◽  
pp. 1713-1717 ◽  
Author(s):  
I. M. Stanford
Keyword(s):  
Globus Pallidus ◽  
Action Potential Firing ◽  
Bath Application ◽  
Potential Firing ◽  
Intrinsic Oscillation ◽  
Cross Correlations ◽  
Neuronal Oscillators ◽  
Membrane Oscillations

In vivo, neurons of the globus pallidus (GP) and subthalamic nucleus (STN) resonate independently around 70 Hz. However, on the loss of dopamine as in Parkinson's disease, there is a switch to a lower frequency of firing with increased bursting and synchronization of activity. In vitro, type A neurons of the GP, identified by the presence of Ih and rebound depolarizations, fire at frequencies (≤80 Hz) in response to glutamate pressure ejection, designed to mimic STN input. The profile of this frequency response was unaltered by bath application of the GABAA antagonist bicuculline (10 μM), indicating the lack of involvement of a local GABA neuronal network, while cross-correlations of neuronal pairs revealed uncorrelated activity or phase-locked activity with a variable phase delay, consistent with each GP neuron acting as an independent oscillator. This autonomy of firing appears to arise due to the presence of intrinsic voltage- and sodium-dependent subthreshold membrane oscillations. GABAA inhibitory postsynaptic potentials are able to disrupt this tonic activity while promoting a rebound depolarization and action potential firing. This rebound is able to reset the phase of the intrinsic oscillation and provides a mechanism for promoting coherent firing activity in ensembles of GP neurons that may ultimately lead to abnormal and pathological disorders of movement.

Increasing Extracellular Potassium Results in Subthalamic Neuron Activity Resembling That Seen in a 6-Hydroxydopamine Lesion

2008 ◽  
Vol 99 (6) ◽  
pp. 2902-2915 ◽  
Author(s):  
Ulf Strauss ◽  
Fu-Wen Zhou ◽  
Jeannette Henning ◽  
Arne Battefeld ◽  
Andreas Wree ◽  
...  
Keyword(s):  
Neuronal Activity ◽  
Potassium Concentration ◽  
Neuron Activity ◽  
Extracellular Potassium ◽  
Action Potential Firing ◽  
Extracellular Potassium Concentration ◽  
Potential Firing ◽  
6 Hydroxydopamine

Abnormal neuronal activity in the subthalamic nucleus (STN) plays a crucial role in the pathophysiology of Parkinson's disease (PD). Although altered extracellular potassium concentration ([K+]o) and sensitivity to [K+]o modulates neuronal activity, little is known about the potassium balance in the healthy and diseased STN. In vivo measurements of [K+]o using ion-selective electrodes demonstrated a twofold increase in the decay time constant of lesion-induced [K+]o transients in the STN of adult Wistar rats with a unilateral 6-hydroxydopamine (6-OHDA) median forebrain bundle lesion, employed as a model of PD, compared with nonlesioned rats. Various [K+]o concentrations (1.5–12.5 mM) were applied to in vitro slice preparations of three experimental groups of STN slices from nonlesioned control rats, ipsilateral hemispheres, and contralateral hemispheres of lesioned rats. The majority of STN neurons of nonlesioned rats and in slices contralateral to the lesion fired spontaneously, predominantly in a regular pattern, whereas those in slices ipsilateral to the lesion fired more irregularly or even in bursts. Experimentally increased [K+]o led to an increase in the number of spontaneously firing neurons and action potential firing rates in all groups. This was accompanied by a decrease in the amplitude of post spike afterhyperpolarization (AHP) and the amplitude and duration of the posttrain AHP. Lesion effects in ipsilateral neurons at physiological [K+]o resembled the effects of elevated [K+]o in nonlesioned rats. Our data suggest that changed potassium sensitivity due to conductivity alterations and delayed clearance may be critical for shaping STN activity in parkinsonian states.

Response Sensitivity of Barrel Neuron Subpopulations to Simulated Thalamic Input

2010 ◽  
Vol 103 (6) ◽  
pp. 3001-3016 ◽  
Author(s):  
Michael J. Pesavento ◽  
Cynthia D. Rittenhouse ◽  
David J. Pinto
Keyword(s):  
Barrel Cortex ◽  
Brain Slices ◽  
Input Resistance ◽  
Inhibitory Neurons ◽  
Membrane Properties ◽  
Cortical Function ◽  
Thalamic Input ◽  
Intrinsic Membrane Properties

Our goal is to examine the relationship between neuron- and network-level processing in the context of a well-studied cortical function, the processing of thalamic input by whisker-barrel circuits in rodent neocortex. Here we focus on neuron-level processing and investigate the responses of excitatory and inhibitory barrel neurons to simulated thalamic inputs applied using the dynamic clamp method in brain slices. Simulated inputs are modeled after real thalamic inputs recorded in vivo in response to brief whisker deflections. Our results suggest that inhibitory neurons require more input to reach firing threshold, but then fire earlier, with less variability, and respond to a broader range of inputs than do excitatory neurons. Differences in the responses of barrel neuron subtypes depend on their intrinsic membrane properties. Neurons with a low input resistance require more input to reach threshold but then fire earlier than neurons with a higher input resistance, regardless of the neuron's classification. Our results also suggest that the response properties of excitatory versus inhibitory barrel neurons are consistent with the response sensitivities of the ensemble barrel network. The short response latency of inhibitory neurons may serve to suppress ensemble barrel responses to asynchronous thalamic input. Correspondingly, whereas neurons acting as part of the barrel circuit in vivo are highly selective for temporally correlated thalamic input, excitatory barrel neurons acting alone in vitro are less so. These data suggest that network-level processing of thalamic input in barrel cortex depends on neuron-level processing of the same input by excitatory and inhibitory barrel neurons.

Integration of Synaptic Responses to Neighboring Whiskers in Rat Barrel Cortex In Vivo

2005 ◽  
Vol 93 (4) ◽  
pp. 1920-1934 ◽  
Author(s):  
Michael J. Higley ◽  
Diego Contreras
Keyword(s):  
Barrel Cortex ◽  
Single Cells ◽  
Receptive Fields ◽  
Synaptic Integration ◽  
Synaptic Response ◽  
Cortical Function ◽  
Sensory Stimuli ◽  
Paired Stimulation ◽  
The Individual

Characterizing input integration at the single-cell level is a critical step to understanding cortical function, particularly when sensory stimuli are represented over wide cortical areas and single cells exhibit large receptive fields. To study synaptic integration of sensory inputs, we made intracellular recordings from the barrel cortex of anesthetized rats in vivo. For each cell, we deflected the principal whisker (PW) either alone or preceded by the deflection of a single adjacent whisker (AW) at an interval of 20 or 3 ms. At the 20-ms interval in all cases, prior AW deflection significantly suppressed the PW-evoked spike output and caused the underlying synaptic response to reach a peak Vm less depolarized than that arising from PW deflection alone. The decrease in peak Vm was not attributed to hyperpolarizing inhibition but to a divisive reduction in PW-evoked PSP amplitude. The reduction in amplitude was not a result of shunting inhibition but was mostly a result of removal of the synaptic drive, or disfacilitation. When the AW–PW interval was shortened to 3 ms, spike suppression was observed in a subset of the cells studied. In most cases, a divisive reduction in synaptic response amplitude was offset by summation with the preceding AW-evoked depolarization. To determine whether suppression is a general feature of synaptic integration by barrel cortex neurons, we also characterized the interaction of responses evoked by local electrical stimulation. In contrast to the whisker data, we found that responses to paired stimulation at the same intervals produced more spikes and reached a peak Vm more depolarized than the individual responses alone, suggesting that whisker-evoked suppression is not a result of postsynaptic mechanisms. Instead, we propose that cross-whisker response suppression depends on sensory-specific mechanisms at cortical and subcortical levels.

scholarly journals Activity of Cerebellar Nuclei Neurons Correlates with ZebrinII Identity of Their Purkinje Cell Afferents

Cells ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2686
Author(s):  
Gerrit C. Beekhof ◽  
Simona V. Gornati ◽  
Cathrin B. Canto ◽  
Avraham M. Libster ◽  
Martijn Schonewille ◽  
...  
Keyword(s):  
Action Potential ◽  
Bimodal Distribution ◽  
Cerebellar Nuclei ◽  
Firing Frequency ◽  
Action Potential Firing ◽  
Adult Mice ◽  
Electrophysiological Recordings ◽  
Potential Firing

Purkinje cells (PCs) in the cerebellar cortex can be divided into at least two main subpopulations: one subpopulation that prominently expresses ZebrinII (Z+), and shows a relatively low simple spike firing rate, and another that hardly expresses ZebrinII (Z–) and shows higher baseline firing rates. Likewise, the complex spike responses of PCs, which are evoked by climbing fiber inputs and thus reflect the activity of the inferior olive (IO), show the same dichotomy. However, it is not known whether the target neurons of PCs in the cerebellar nuclei (CN) maintain this bimodal distribution. Electrophysiological recordings in awake adult mice show that the rate of action potential firing of CN neurons that receive input from Z+ PCs was consistently lower than that of CN neurons innervated by Z– PCs. Similar in vivo recordings in juvenile and adolescent mice indicated that the firing frequency of CN neurons correlates to the ZebrinII identity of the PC afferents in adult, but not postnatal stages. Finally, the spontaneous action potential firing pattern of adult CN neurons recorded in vitro revealed no significant differences in intrinsic pacemaking activity between ZebrinII identities. Our findings indicate that all three main components of the olivocerebellar loop, i.e., PCs, IO neurons and CN neurons, operate at a higher rate in the Z– modules.

scholarly journals Detecting apoptosis as a clinical endpoint for proof of a clinical principle

2020 ◽  
Author(s):  
Piero Zollet ◽  
Timothy E.Yap ◽  
M Francesca Cordeiro
Keyword(s):  
Drug Development ◽  
Therapeutic Response ◽  
Imaging Techniques ◽  
Brain Diseases ◽  
Promising Strategy ◽  
Sight Loss ◽  
Apoptosis Detection ◽  
Novel Therapeutic Strategies

The transparent eye media represent a window through which to observe changes occurring in the retina during pathological processes. In contrast to visualising the extent of neurodegenerative damage that has already occurred, imaging an active process such as apoptosis has the potential to report on disease progression and therefore the threat of irreversible functional loss in various eye and brain diseases. Early diagnosis in these conditions is an important unmet clinical need to avoid or delay irreversible sight loss. In this setting, apoptosis detection is a promising strategy with which to diagnose, provide prognosis, and monitor therapeutic response. Additionally, monitoring apoptosis in vitro and in vivo has been shown to be valuable for drug development in order to assess the efficacy of novel therapeutic strategies both in the pre-clinical and clinical setting. Detection of Apoptosing Retinal Cells (DARC) technology is to date the only tool of its kind to have been tested in clinical trials, with other new imaging techniques under investigation in the fields of neuroscience, ophthalmology and drug development. We summarize the transitioning of techniques detecting apoptosis from bench to bedside, along with the future possibilities they encase.

scholarly journals Optimization of X-ray Investigations in Dentistry Using Optical Coherence Tomography

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4554
Author(s):  
Ralph-Alexandru Erdelyi ◽  
Virgil-Florin Duma ◽  
Cosmin Sinescu ◽  
George Mihai Dobre ◽  
Adrian Bradu ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Radiation Dose ◽  
Imaging Techniques ◽  
Image Resolution ◽  
Optical Coherence ◽  
X Rays ◽  
High Quality ◽  
X Ray

The most common imaging technique for dental diagnoses and treatment monitoring is X-ray imaging, which evolved from the first intraoral radiographs to high-quality three-dimensional (3D) Cone Beam Computed Tomography (CBCT). Other imaging techniques have shown potential, such as Optical Coherence Tomography (OCT). We have recently reported on the boundaries of these two types of techniques, regarding. the dental fields where each one is more appropriate or where they should be both used. The aim of the present study is to explore the unique capabilities of the OCT technique to optimize X-ray units imaging (i.e., in terms of image resolution, radiation dose, or contrast). Two types of commercially available and widely used X-ray units are considered. To adjust their parameters, a protocol is developed to employ OCT images of dental conditions that are documented on high (i.e., less than 10 μm) resolution OCT images (both B-scans/cross sections and 3D reconstructions) but are hardly identified on the 200 to 75 μm resolution panoramic or CBCT radiographs. The optimized calibration of the X-ray unit includes choosing appropriate values for the anode voltage and current intensity of the X-ray tube, as well as the patient’s positioning, in order to reach the highest possible X-rays resolution at a radiation dose that is safe for the patient. The optimization protocol is developed in vitro on OCT images of extracted teeth and is further applied in vivo for each type of dental investigation. Optimized radiographic results are compared with un-optimized previously performed radiographs. Also, we show that OCT can permit a rigorous comparison between two (types of) X-ray units. In conclusion, high-quality dental images are possible using low radiation doses if an optimized protocol, developed using OCT, is applied for each type of dental investigation. Also, there are situations when the X-ray technology has drawbacks for dental diagnosis or treatment assessment. In such situations, OCT proves capable to provide qualitative images.

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