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2022 ◽  
Author(s):  
Andrew Tyler Landau ◽  
Pojeong Park ◽  
David Wong-Campos ◽  
Tian He ◽  
Adam Ezra Cohen ◽  
...  

Back-propagating action potentials (bAPs) regulate synaptic plasticity by evoking voltage-dependent calcium influx throughout dendrites. Attenuation of bAP amplitude in distal dendritic compartments alters plasticity in a location-specific manner by reducing bAP-dependent calcium influx. However, it is not known if neurons exhibit branch-specific variability in bAP-dependent calcium signals, independent of distance-dependent attenuation. Here, we reveal that bAPs fail to evoke calcium influx through voltage-gated calcium channels (VGCCs) in a specific population of dendritic branches in cortical layer 2/3 pyramidal cells, despite evoking substantial VGCC-mediated calcium influx in sister branches. These branches contain VGCCs and successfully propagate bAPs in the absence of synaptic input; nevertheless, they fail to exhibit bAP-evoked calcium influx due to a branch-specific reduction in bAP amplitude. We demonstrate that these branches have more elaborate branch structure compared to sister branches, which causes a local reduction in electrotonic impedance and bAP amplitude. Finally, we show that bAPs still amplify synaptically-mediated calcium influx in these branches because of differences in the voltage-dependence and kinetics of VGCCs and NMDA-type glutamate receptors. Branch-specific compartmentalization of bAP-dependent calcium signals may provide a mechanism for neurons to diversify synaptic tuning across the dendritic tree.


2022 ◽  
Vol 13 ◽  
Author(s):  
Francisco Javier Fuentealba-Villarroel ◽  
Josué Renner ◽  
Arlete Hilbig ◽  
Oliver J. Bruton ◽  
Alberto A. Rasia-Filho

The human posteromedial cortex (PMC), which includes the precuneus (PC), represents a multimodal brain area implicated in emotion, conscious awareness, spatial cognition, and social behavior. Here, we describe the presence of Nissl-stained elongated spindle-shaped neurons (suggestive of von Economo neurons, VENs) in the cortical layer V of the anterior and central PC of adult humans. The adapted “single-section” Golgi method for postmortem tissue was used to study these neurons close to pyramidal ones in layer V until merging with layer VI polymorphic cells. From three-dimensional (3D) reconstructed images, we describe the cell body, two main longitudinally oriented ascending and descending dendrites as well as the occurrence of spines from proximal to distal segments. The primary dendritic shafts give rise to thin collateral branches with a radial orientation, and pleomorphic spines were observed with a sparse to moderate density along the dendritic length. Other spindle-shaped cells were observed with straight dendritic shafts and rare branches or with an axon emerging from the soma. We discuss the morphology of these cells and those considered VENs in cortical areas forming integrated brain networks for higher-order activities. The presence of spindle-shaped neurons and the current discussion on the morphology of putative VENs address the need for an in-depth neurochemical and transcriptomic characterization of the PC cytoarchitecture. These findings would include these spindle-shaped cells in the synaptic and information processing by the default mode network and for general intelligence in healthy individuals and in neuropsychiatric disorders involving the PC in the context of the PMC functioning.


2021 ◽  
Vol 11 (4) ◽  
pp. 288-292
Author(s):  
V. A. Ananev ◽  
V. N. Pavlov ◽  
A. M. Pushkarev

Background. Modern minimally invasive surgical techniques reduce traumatism of operative interventions and aggressive anaesthesia, which accordingly shortens the patient’s hospital stay and rehabilitation period.Aim. An improvement of surgical outcomes in patients with purulent pyelonephritis via introduction of laparoscopic techniques.Materials and methods. Th e study included 80 purulent pyelonephritis patients operated at the Territorial Clinical Hospital during 2006—2018. Th e patients were divided between two cohorts. Cohort 1 included 40 (50 %) patients operated with standard techniques (ST), cohort 2 — 40 (50 %) patients having surgery by an original minimally invasive technique (OT). Kidney decapsulation was found to outcome in parenchymal decompression and blood circulation restore in cortical layer. Intraarterial infusion of alprostadil prevents further spread of purulent-destructive processes in kidney.Results and discussion. In patients with the minimally invasive technique, postoperative period proceeded at no complications. On day 1, the patients reported reduced pain syndrome in the surgical area. Contrasted renal MSCT before and aft er surgery showed the recovery of renal blood flow and significant diminishing of destruction foci in short term. Nephrectomy was not performed as no-indication.Conclusion. The treatment outcomes in 40 patients having the new surgical technique demonstrate its efficacy and applicability in clinical practice.


2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Talis Bachmann

Abstract Theories of consciousness using neurobiological data or being influenced by these data have been focused either on states of consciousness or contents of consciousness. These theories have occasionally used evidence from psychophysical phenomena where conscious experience is a dependent experimental variable. However, systematic catalog of many such relevant phenomena has not been offered in terms of these theories. In the perceptual retouch theory of thalamocortical interaction, recently developed to become a blend with the dendritic integration theory, consciousness states and contents of consciousness are explained by the same mechanism. This general-purpose mechanism has modulation of the cortical layer-5 pyramidal neurons that represent contents of consciousness as its core. As a surplus, many experimental psychophysical phenomena of conscious perception can be explained by the workings of this mechanism. Historical origins and current views inherent in this theory are presented and reviewed.


2021 ◽  
Author(s):  
Mitchell P Morton ◽  
Sachira Denagamage ◽  
Isabel J Blume ◽  
John H Reynolds ◽  
Monika P Jadi ◽  
...  

Identical stimuli can be perceived or go unnoticed across successive presentations, producing divergent behavioral readouts despite similarities in sensory input. We hypothesized that fluctuations in neurophysiological states in the sensory neocortex, which could alter cortical processing at the level of neural subpopulations, underlies this perceptual variability. We analyzed cortical layer-specific electrophysiological activity in visual area V4 during a cued attention task. We find that hit trials are characterized by a larger pupil diameter and lower incidence of microsaccades, indicative of a behavioral state with increased arousal and perceptual stability. Target stimuli presented at perceptual threshold evoke elevated multi-unit activity in V4 neurons in hit trials compared to miss trials, across all cortical layers. Putative excitatory and inhibitory neurons are strongly positively modulated in the input (IV) and deep (V & VI) layers of the cortex during hit trials. Excitatory neurons in the superficial cortical layers exhibit lower variability in hit trials. Deep layer neurons are less phase-locked to low frequency rhythms in hits. Hits are also characterized by greater interlaminar coherence between the superficial and deep layers in the pre-stimulus period, and a complementary pattern between the input layer and both the superficial and deep layers in the stimulus-evoked period. Taken together, these results indicate that a state of elevated levels of arousal and perceptual stability allow enhanced processing of sensory stimuli, which contributes to hits at perceptual threshold.


2021 ◽  
Vol 17 (11) ◽  
pp. e1009601
Author(s):  
Natalie Klein ◽  
Joshua H. Siegle ◽  
Tobias Teichert ◽  
Robert E. Kass

Because local field potentials (LFPs) arise from multiple sources in different spatial locations, they do not easily reveal coordinated activity across neural populations on a trial-to-trial basis. As we show here, however, once disparate source signals are decoupled, their trial-to-trial fluctuations become more accessible, and cross-population correlations become more apparent. To decouple sources we introduce a general framework for estimation of current source densities (CSDs). In this framework, the set of LFPs result from noise being added to the transform of the CSD by a biophysical forward model, while the CSD is considered to be the sum of a zero-mean, stationary, spatiotemporal Gaussian process, having fast and slow components, and a mean function, which is the sum of multiple time-varying functions distributed across space, each varying across trials. We derived biophysical forward models relevant to the data we analyzed. In simulation studies this approach improved identification of source signals compared to existing CSD estimation methods. Using data recorded from primate auditory cortex, we analyzed trial-to-trial fluctuations in both steady-state and task-evoked signals. We found cortical layer-specific phase coupling between two probes and showed that the same analysis applied directly to LFPs did not recover these patterns. We also found task-evoked CSDs to be correlated across probes, at specific cortical depths. Using data from Neuropixels probes in mouse visual areas, we again found evidence for depth-specific phase coupling of primary visual cortex and lateromedial area based on the CSDs.


Author(s):  
Д. В. Веселкова ◽  
Н. Г. Свиркина ◽  
О. И. Успенская ◽  
М. В. Добровольская ◽  
И. В. Рукавишникова ◽  
...  

В ходе археологических исследований кургана № 2 из группы из двух курганов у с. Льговского (Республика Крым) было исследовано 22 погребения эпохи бронзы - раннего железного века. В одном из погребений эпохи бронзы был обнаружен скелет молодого мужчины, на черепе которого были зафиксированы следы трепанации. В статье представлены результаты ее комплексного исследования. Данная трепанация отличается крупным размером и сохранением тонкой нижней пластинки кортикального слоя кости на большей части поверхности места операционного вмешательства. Преобладающей техникой выполнения операции было скобление каменным орудием. Трасологический анализ выявил комплекс следов, оставленных по меньшей мере двумя инструментами с различным рабочим лезвием. Выдвигается предположение о лечебной цели проведения манипуляции. The archaeological excavations of kurgan 2 from the group of two kurgans near the L'govskoye village (Republic of Crimea) examined 21 burials dating to the Bronze Age - Early Iron Age. One of the Bronze Age burials yielded a skeleton of a young man with traces of trepanation on the skull. The paper reports on the results of its comprehensive research. This trepanation is noted for its large size and preservation of a thin lower plate of the bone cortical layer on a large surgically treated region. Scraping with a stone tool was a prevailing method of surgical procedures. The trace wear analysis revealed a series of traces left by at least two tools with different cutting edges. The paper also suggests that this surgical intervention was performed for treatment purposes.


Nature ◽  
2021 ◽  
Author(s):  
Lou Beaulieu-Laroche ◽  
Norma J. Brown ◽  
Marissa Hansen ◽  
Enrique H. S. Toloza ◽  
Jitendra Sharma ◽  
...  
Keyword(s):  

2021 ◽  
Author(s):  
Chao Han ◽  
Gwendolyn English ◽  
Hannes P. Saal ◽  
Giacomo Indiveri ◽  
Aditya Gilra ◽  
...  

In complex natural environments, sensory systems are constantly exposed to a large stream of inputs. Novel or rare stimuli, which are often associated with behaviorally important events, are typically processed differently than the steady sensory background, which has less relevance. Neural signatures of such differential processing, commonly referred to as novelty detection, have been identified on the level of EEG recordings as mismatch negativity and the level of single neurons as stimulus-specific adaptation. Here, we propose a multi-scale recurrent network with synaptic depression to explain how novelty detection can arise in the whisker-related part of the somatosensory thalamocortical loop. The architecture and dynamics of the model presume that neurons in cortical layer 6 adapt, via synaptic depression, specifically to a frequently presented stimulus, resulting in reduced population activity in the corresponding cortical column when compared with the population activity evoked by a rare stimulus. This difference in population activity is then projected from the cortex to the thalamus and amplified through the interaction between neurons of the primary and reticular nuclei of the thalamus, resulting in spindle-like, rhythmic oscillations. These differentially activated thalamic oscillations are forwarded to cortical layer 4 as a late secondary response that is specific to rare stimuli that violate a particular stimulus pattern. Model results show a strong analogy between this late single neuron activity and EEG-based mismatch negativity in terms of their common sensitivity to presentation context and timescales of response latency, as observed experimentally. Our results indicate that adaptation in L6 can establish the thalamocortical dynamics that produce signatures of SSA and MMN and suggest a mechanistic model of novelty detection that could generalize to other sensory modalities.


2021 ◽  
Vol 17 (11) ◽  
pp. e1009558
Author(s):  
Eilam Goldenberg Leleo ◽  
Idan Segev

The output of neocortical layer 5 pyramidal cells (L5PCs) is expressed by a train of single spikes with intermittent bursts of multiple spikes at high frequencies. The bursts are the result of nonlinear dendritic properties, including Na+, Ca2+, and NMDA spikes, that interact with the ~10,000 synapses impinging on the neuron’s dendrites. Output spike bursts are thought to implement key dendritic computations, such as coincidence detection of bottom-up inputs (arriving mostly at the basal tree) and top-down inputs (arriving mostly at the apical tree). In this study we used a detailed nonlinear model of L5PC receiving excitatory and inhibitory synaptic inputs to explore the conditions for generating bursts and for modulating their properties. We established the excitatory input conditions on the basal versus the apical tree that favor burst and show that there are two distinct types of bursts. Bursts consisting of 3 or more spikes firing at < 200 Hz, which are generated by stronger excitatory input to the basal versus the apical tree, and bursts of ~2-spikes at ~250 Hz, generated by prominent apical tuft excitation. Localized and well-timed dendritic inhibition on the apical tree differentially modulates Na+, Ca2+, and NMDA spikes and, consequently, finely controls the burst output. Finally, we explored the implications of different burst classes and respective dendritic inhibition for regulating synaptic plasticity.


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