1,053 research outputs found
Cholinergic modulation of the default mode like network in rats. Peeters, van den Berg, et al.
No full textHistology data
Note: The MRI Dataset of this article is accessible elsewhere: Xnat Central: [central.xnat.org - code: DMLN]
Feature selectivity of the gamma-band of the local field potential in primate primary visual cortex
No full textExtra-cellular voltage fluctuations (local field potentials; LFPs) reflecting neural mass action are ubiquitous across species and brain regions. Numerous studies have characterized the properties of LFP signals in the cortex to study sensory and motor computations as well as cognitive processes like attention, perception and memory. In addition, its extracranial counterpart – the electroencelphalogram (EEG) – is widely used in clinical applications. However, the link between LFP signals and the underlying activity of local populations of neurons remains largely elusive. Here, we review recent work elucidating the relationship between spiking activity of local neural populations and LFP signals. We focus on oscillations in the gamma-band (30-90Hz) of the local field potential in the primary visual cortex (V1) of the macaque that dominate during visual stimulation. Given that in area V1 much is known about the properties of single neurons and the cortical architecture, it provides an excellent opportunity to study the mechanisms underlying the generation of the local field potential
Orientation tuning of the local field potential and multi-unit activity in the primary visual cortex of the macaque
No full textOscillations in the local field potential (LFP) are abundant across species and brain regions. The possible relationship of these low-frequency extracelluar voltage fluctuations with the activity of the underlying local population of neurons remains largely elusive. To study this relationship, we used an array of chronically implanted tetrodes spanning a distance of 700 μm and simultaneously recorded action potentials from multiple well-isolated single units, multi unit activity (MUA) and LFP from area V1 of the awake, behaving macaque. Moving and static gratings of different orientations were used for visual stimulation. In agreement with previous studies we find that the increase of LFP gamma-band power is a function of the orientation of the stimulus. However, the power of the gamma-band contains much less information about the orientation of the stimulus than the MUA and SUA recorded at the same site (Figure 1A). The average discriminability d ‘between preferred and orthogonal orientation was 2.46 for MUA, 2.45 for SUA and 1.01 for the LFP. Moreover, in contrast to recent results from area MT (Liu and Newsome, 2006) we find only a weak correlation between the preferred orientation of the MUA tuning function and that of the LFP (Figure 1B, different colors indicate different animals). Interestingly, all nearby LFP recording sites in our array were tuned to a similar orientation while the preferred orientations of MUA tuning functions were widely scattered. These results suggest that the power of LFP signals does not capture local population activity at the scale of orientation columns in area V1
Orientation tuning of the local field potential and multi-unit activity in the primary visual cortex of the macaque
No full textOscillations in the local field potential (LFP) are abundant across species and brain regions. The possible relationship of these low-frequency extracelluar voltage fluctuations with the activity of the underlying local population of neurons remains largely elusive. To study this relationship, we used an array of chronically implanted tetrodes spanning a distance of 700 μm and simultaneously recorded action potentials from multiple well-isolated single units, multi unit activity (MUA) and LFP from area V1 of the awake, behaving macaque. Moving and static gratings of different orientations were used for visual stimulation. In agreement with previous studies we find that the increase of LFP gamma-band power is a function of the orientation of the stimulus. However, the power of the gamma-band contains much less information about the orientation of the stimulus than the MUA and SUA recorded at the same site (Figure 1A). The average discriminability d‘ between preferred and orthogonal orientation was 2.46 for MUA, 2.45 for SUA and 1.01 for the LFP. Moreover, in contrast to recent results from area MT (Liu and Newsome, 2006) we find only a weak correlation between the preferred orientation of the MUA tuning function and that of the LFP (Figure 1B, different colors indicate different animals). Interestingly, all nearby LFP recording sites in our array were tuned to a similar orientation while the preferred orientations of MUA tuning functions were widely scattered. These results suggest that the power of LFP signals does not capture local population activity at the scale of orientation columns in area V1
Decorrelated Neuronal Firing in Cortical Microcircuits
No full textCorrelated trial-to-trial variability in the activity of cortical neurons is thought to reflect the functional connectivity of the circuit. Many cortical areas are organized into functional columns, in which neurons are believed to be densely connected and to share common input. Numerous studies report a high degree of correlated variability between nearby cells. We developed chronically implanted multitetrode arrays offering unprecedented recording quality to reexamine this question in the primary visual cortex of awake macaques. We found that even nearby neurons with similar orientation tuning show virtually no correlated variability. Our findings suggest a refinement of current models of cortical microcircuit architecture and function: Either adjacent neurons share only a few percent of their inputs or, alternatively, their activity is actively decorrelated
Comparing the feature selectivity of the gamma-band of the local field potential and the underlying spiking activity in primate visual cortex
No full textThe local field potential (LFP), comprised of low-frequency extra-cellular voltage fluctuations, has been used extensively to study the mechanisms of brain function. In particular, oscillations in the gamma-band (30–90 Hz) are ubiquitous in the cortex of many species during various cognitive processes. Surprisingly little is known about the underlying biophysical processes generating this signal. Here, we examine the relationship of the local field potential to the activity of localized populations of neurons by simultaneously recording spiking activity and LFP from the primary visual cortex (V1) of awake, behaving macaques. The spatial organization of orientation tuning and ocular dominance in this area provides an excellent opportunity to study this question, because orientation tuning is organized at a scale around one order of magnitude finer than the size of ocular dominance columns. While we find a surprisingly weak correlation between the preferred orientation of multi-unit activity and gamma-band LFP recorded on the same tetrode, there is a strong correlation between the ocular preferences of both signals. Given the spatial arrangement of orientation tuning and ocular dominance, this leads us to conclude that the gamma-band of the LFP seems to sample an area considerably larger than orientation columns. Rather, its spatial resolution lies at the scale of ocular dominance columns
Factors affecting trust and communication in global virtual teams
No full textAuthor Georgios GousiasMasterarbeit Universität Linz 2022Arbeit auf den öffentlichen PCs in den Bibliotheken der JKU+Medizin abrufba
Factors affecting trust and communication in global virtual teams
No full textAuthor Georgios GousiasMasterarbeit Universität Linz 2022Arbeit auf den öffentlichen PCs in den Bibliotheken der JKU+Medizin abrufba
Unraveling the interplay of brain networks by combining neuromodulatory tools and in vivo MRI in rodents
No full textAbstract: The increasing prevalence of neurological disorders poses an ever-increasing healthcare burden on society. A better understanding of the underlying mechanisms mediating these neurological disorders is indispensable for the identification of new potential therapeutic targets. Various neurological disorders have been associated with disturbances in the interplay of functional brain networks. This thesis focuses on unraveling the relationships between functional brain networks, with particular interest for the default mode-like network and task-positive networks in rodents. We utilized a relatively new multi-modal approach combining chemogenetics and non-invasive functional magnetic resonance imaging (fMRI). This combined approach allows collecting valuable information about the role of specific subsets of cells in brain network function and dysfunction. In the first part of this thesis, we found that chemogenetic manipulation of a specific area, i.e. the anterior cingulate area (ACC), is able to modulate the neural activity and functional connectivity of brain networks. More specifically, silencing of the ACC resulted in altered neural activity and functional connectivity in brain networks including connections with sensory cortex, thalamus, basolateral amygdala and ventral pallidum, areas involved in attention processes, working memory, fear behavior and reward, respectively. In addition, we found that damage to the ACC is associated with decreased functional connectivity in the default mode-like network, the task-positive network and visual system. Interestingly, these affected functional networks demonstrated distinguishable recovery patterns over time. In the second part of this thesis, we focused on the interactions between the default mode-like network and attentional processes. We found that stimulating bottom-up sensory processes (by presenting continuous random flickering light to sedated rats) could decrease the activity and functional connectivity in the default mode-like network, similarly as task-related deactivations. In a next study, we aimed to shed light on the mechanisms involved in the deactivation of the default mode-like network during attentional processes. Our results indicated functional connectivity decreases in the default mode-like network upon chemogenetic stimulation of basal forebrain cholinergic neurons, suggesting a role for the cholinergic system in default mode-like network regulation. Taken together, this thesis provides unique insights on functional and dysfunctional brain networks. Furthermore, this thesis underscores the significance of combining chemogenetics with fMRI for future studies as well as its promise for future neurotherapeutics as it can eliminate the off-target effects of current therapeutics and allows the on-demand control of specified neurons
Recording Chronically from the same Neurons in Awake, Behaving Primates
No full textUnderstanding the mechanisms of learning requires characterizing how the response properties of individual neurons and interactions across populations of neurons change over time. In order to study learning in-vivo, we need the ability to track an electrophysiological signature that uniquely identifies each recorded neuron for extended periods of time. We have identified such an extracellular signature using a statistical framework which allows quantification of the accuracy by which stable neurons can be identified across successive recording sessions. Our statistical framework uses spike waveform information recorded on a tetrodes four channels in order to define a measure of similarity between neurons recorded across time. We use this framework to quantitatively demonstrate for the first time the ability to record from the same neurons across multiple consecutive days and weeks. The chronic recording techniques and methods of analyses we report can be used to characterize the changes in brain circuits du
e to learning
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