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  • Engler, Gerhard  (11)
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  • 1
    Language: English
    In: PLoS ONE, 01 January 2015, Vol.10(5), p.e0124952
    Description: During the last two decades ferrets (Mustela putorius) have been established as a highly efficient animal model in different fields in neuroscience. Here we asked whether ferrets integrate sensory information according to the same principles...
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 2
    Language: English
    In: Journal of neurophysiology, September 2013, Vol.110(6), pp.1333-45
    Description: In the superior colliculus (SC), visual afferent inputs from various sources converge in a highly organized way such that all layers form topographically aligned representations of contralateral external space. Despite this anatomical organization, it remains unclear how the layer-specific termination of different visual input pathways is reflected in the nature of visual response properties and their distribution across layers. To uncover the physiological correlates underlying the laminar organization of the SC, we recorded multiunit and local field potential activity simultaneously from all layers with dual-shank multichannel linear probes. We found that the location of spatial receptive fields was strongly conserved across all visual responsive layers. There was a tendency for receptive field size to increase with depth in the SC, with superficial receptive fields significantly smaller than deep receptive fields. Additionally, superficial layers responded significantly faster than deeper layers to flash stimulation. In some recordings, flash-evoked responses were characterized by the presence of gamma oscillatory activity (40-60 Hz) in multiunit and field potential signals, which was strongest in retinorecipient layers. While SC neurons tended to respond only weakly to full-field drifting gratings, we observed very similar oscillatory responses to the offset of grating stimuli, suggesting gamma oscillations are produced following light offset. Oscillatory spiking activity was highly correlated between horizontally distributed neurons within these layers, with oscillations temporally locked to the stimulus. Together, visual response properties provide physiological evidence reflecting the laminar-specific termination of visual afferent pathways in the SC, most notably characterized by the oscillatory entrainment of superficial neurons.
    Keywords: Ferret ; Oscillations ; Superior Colliculus ; Evoked Potentials, Visual ; Superior Colliculi -- Physiology
    ISSN: 00223077
    E-ISSN: 1522-1598
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  • 3
    In: Cerebral Cortex, 2018, Vol. 28(8), pp.2991-3003
    Description: Cortical single neuron activity and local field potential patterns change at different depths of general anesthesia. Here, we investigate the associated network level changes of functional connectivity. We recorded ongoing electrocorticographic (ECoG) activity from temporo-parieto-occipital cortex of 6 ferrets at various levels of isoflurane/nitrous oxide anesthesia and determined functional connectivity by computing amplitude envelope correlations. Through hierarchical clustering, we derived typical connectivity patterns corresponding to light, intermediate and deep anesthesia. Generally, amplitude correlation strength increased strongly with depth of anesthesia across all cortical areas and frequency bands. This was accompanied, at the deepest level, by the emergence of burst-suppression activity in the ECoG signal and a change of the spectrum of the amplitude envelope. Normalization of functional connectivity to the distribution of correlation coefficients showed that the topographical patterns remained similar across depths of anesthesia, reflecting the functional association of the underlying cortical areas. Thus, while strength and temporal properties of amplitude co-modulation vary depending on the activity of local neural circuits, their network-level interaction pattern is presumably most strongly determined by the underlying structural connectivity.
    Keywords: Amplitude Correlations ; Anesthesia ; Ecog ; Icm ; Ongoing Activity
    ISSN: 1047-3211
    E-ISSN: 1460-2199
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  • 4
    Language: English
    In: Science advances, August 2015, Vol.1(7), pp.e1500229
    Description: In the absence of sensory stimulation or motor output, the brain exhibits complex spatiotemporal patterns of intrinsically generated neural activity. Analysis of ongoing brain dynamics has identified the prevailing modes of cortico-cortical interaction; however, little is known about how such patterns of intrinsically generated activity are correlated between cortical and subcortical brain areas. We investigate the correlation structure of ongoing cortical and superior colliculus (SC) activity across multiple spatial and temporal scales. Ongoing cortico-tectal interaction was characterized by correlated fluctuations in the amplitude of delta, spindle, low gamma, and high-frequency oscillations (〉100 Hz). Of these identified coupling modes, topographical patterns of high-frequency coupling were the most consistent with patterns of anatomical connectivity, reflecting synchronized spiking within cortico-tectal networks. Cortico-tectal coupling at high frequencies was temporally parcellated by the phase of slow cortical oscillations and was strongest for SC-cortex channel pairs that displayed overlapping visual spatial receptive fields. Despite displaying a high degree of spatial specificity, cortico-tectal coupling in lower-frequency bands did not match patterns of cortex-to-SC anatomical connectivity. Collectively, our findings demonstrate that neural activity is spontaneously coupled between cortex and SC, with high- and low-frequency modes of coupling reflecting direct and indirect cortico-tectal interactions, respectively.
    Keywords: Corticotectal ; High Gamma ; Ongoing Neural Dynamics ; Oscillations ; Superior Colliculus
    ISSN: 2375-2548
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  • 5
    In: European Journal of Neuroscience, December 2018, Vol.48(12), pp.3583-3596
    Description: Synchronous spiking of multiple neurons is a key phenomenon in normal brain function and pathologies. Recently, approaches to record spikes from the intact cortical surface using small high‐density arrays of microelectrodes have been reported. It remained unaddressed how epicortical spiking relates to intracortical unit activity. We introduced a mesoscale approach using an array of 64 electrodes with intermediate diameter (250 μm) and combined large‐coverage epicortical recordings in ferrets with intracortical recordings via laminar probes. Empirical data and modelling strongly suggest that our epicortical electrodes selectively captured synchronized spiking of neurons in the cortex beneath. As a result, responses to sensory stimulation were more robust and less noisy compared to intracortical activity, and receptive field properties were well preserved in epicortical recordings. This should promote insights into assembly‐coding beyond the informative value of subdural EEG or single‐unit spiking, and be advantageous to real‐time applications in brain‐machine interfacing. We have compared spiking activity in simultaneous recordings from layers and the intact surface (ECoG) of sensory cortices in the ferret brain. Surface spiking reflected the truly representative activity of the cortical column, i.e. spikes fired in synchrony by several units. We show that this can sharpen tuning, reduce response variability and thus make single trial surface spiking data as informative as post hoc analyzed multi trial or population data from intracortical multi site recordings.
    Keywords: Assembly‐Coding ; Auditory Cortex ; Brain‐Machine Interfaces ; Electrocorticography ; Synchronous Spiking ; Visual Cortex
    ISSN: 0953-816X
    E-ISSN: 1460-9568
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  • 6
    In: European Journal of Neuroscience, May 2015, Vol.41(10), pp.1311-1320
    Description: The integration of visual and auditory spatial information is important for building an accurate perception of the external world, but the fundamental mechanisms governing such audiovisual interaction have only partially been resolved. The earliest interface between auditory and visual processing pathways is in the midbrain, where the superior () and inferior colliculi () are reciprocally connected in an audiovisual loop. Here, we investigate the mechanisms of audiovisual interaction in the midbrain by recording neural signals from the and simultaneously in anesthetized ferrets. Visual stimuli reliably produced band‐limited phase locking of local field potentials (s) in two distinct frequency bands: 6–10 and 15–30 Hz. These visual responses co‐localized with robust auditory responses that were characteristic of the . Imaginary coherence analysis confirmed that visual responses in the were not volume‐conducted signals from the neighboring . Visual responses in the occurred later than retinally driven superficial layers and earlier than deep layers that receive indirect visual inputs, suggesting that retinal inputs do not drive visually evoked responses in the . In addition, and recording sites with overlapping visual spatial receptive fields displayed stronger functional connectivity than sites with separate receptive fields, indicating that visual spatial maps are aligned across both midbrain structures. Reciprocal coupling between the and therefore probably serves the dynamic integration of visual and auditory representations of space. The earliest interface between auditory and visual processing pathways is in the midbrain, where the superior (SC) and inferior colliculi (IC) are reciprocally connected in an audiovisual loop. Here, we show that visual stimuli elicit phase locking in IC local field potentials, and that the timing of responses across the midbrain suggests the SC as a possible source of visually‐evoked entrainment in the IC.
    Keywords: Auditory ; Ferret ; Local Field Potential ; Midbrain ; Visual
    ISSN: 0953-816X
    E-ISSN: 1460-9568
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  • 7
    Language: English
    In: European Journal of Neuroscience, May, 2015, Vol.41(10), p.1311(10)
    ISSN: 0953-816X
    Source: Cengage Learning, Inc.
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  • 8
    Language: English
    In: Sci Rep, 2017, Vol.7(1), pp.8797-8797
    Description: Throughout each day, the brain displays transient changes in state, as evidenced by shifts in behavior and vigilance. While the electrophysiological correlates of brain states have been studied for some time, it remains unclear how large-scale cortico-cortical functional connectivity systematically reconfigures across states. Here, we investigate state-dependent shifts in cortical functional connectivity by recording local field potentials (LFPs) during spontaneous behavioral transitions in the ferret using chronically implanted micro-electrocorticographic (µECoG) arrays positioned over occipital, parietal, and temporal cortical regions. To objectively classify brain state, we describe a data-driven approach that projects time-varying LFP spectral properties into brain state space. Distinct brain states displayed markedly different patterns of cross-frequency phase-amplitude coupling and inter-electrode phase synchronization across several LFP frequency bands. The largest across-state differences in functional connectivity were observed between periods of presumed slow-wave and rapid-eye-movement-sleep/active-state, which were characterized by the contrasting phenomena of cortical network fragmentation and global synchronization, respectively. Collectively, our data provide strong evidence that large-scale functional interactions in the brain dynamically reconfigure across behavioral states.
    Keywords: Article;
    ISSN: 2045-2322
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  • 9
    Language: English
    In: European Journal of Neuroscience, 2015, Vol.41(10), p.1311(10)
    Description: To purchase or authenticate to the full-text of this article, please visit this link: http://onlinelibrary.wiley.com/doi/10.1111/ejn.12847/abstract Byline: Iain Stitt, Edgar Galindo-Leon, Florian Pieper, Karl J. Hollensteiner, Gerhard Engler, Andreas K. Engel Keywords: auditory; ferret; local field potential; midbrain; visual Abstract The integration of visual and auditory spatial information is important for building an accurate perception of the external world, but the fundamental mechanisms governing such audiovisual interaction have only partially been resolved. The earliest interface between auditory and visual processing pathways is in the midbrain, where the superior (SC) and inferior colliculi (IC) are reciprocally connected in an audiovisual loop. Here, we investigate the mechanisms of audiovisual interaction in the midbrain by recording neural signals from the SC and IC simultaneously in anesthetized ferrets. Visual stimuli reliably produced band-limited phase locking of IC local field potentials (LFPs) in two distinct frequency bands: 6-10 and 15-30 Hz. These visual LFP responses co-localized with robust auditory responses that were characteristic of the IC. Imaginary coherence analysis confirmed that visual responses in the IC were not volume-conducted signals from the neighboring SC. Visual responses in the IC occurred later than retinally driven superficial SC layers and earlier than deep SC layers that receive indirect visual inputs, suggesting that retinal inputs do not drive visually evoked responses in the IC. In addition, SC and IC recording sites with overlapping visual spatial receptive fields displayed stronger functional connectivity than sites with separate receptive fields, indicating that visual spatial maps are aligned across both midbrain structures. Reciprocal coupling between the IC and SC therefore probably serves the dynamic integration of visual and auditory representations of space.
    ISSN: 0953-816X
    Source: Cengage Learning, Inc.
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  • 10
    Language: English
    In: Science advances, April 2019, Vol.5(4), pp.eaar7633
    Description: Intrinsically generated patterns of coupled neuronal activity are associated with the dynamics of specific brain states. Sensory inputs are extrinsic factors that can perturb these intrinsic coupling modes, creating a complex scenario in which forthcoming stimuli are processed. Studying this intrinsic-extrinsic interplay is necessary to better understand perceptual integration and selection. Here, we show that this interplay leads to a reconfiguration of functional cortical connectivity that acts as a mechanism to facilitate stimulus processing. Using audiovisual stimulation in anesthetized ferrets, we found that this reconfiguration of coupling modes is context specific, depending on long-term modulation by repetitive sensory inputs. These reconfigured coupling modes lead to changes in latencies and power of local field potential responses that support multisensory integration. Our study demonstrates that this interplay extends across multiple time scales and involves different types of intrinsic coupling. These results suggest a previously unknown large-scale mechanism that facilitates multisensory integration.
    ISSN: Science Advances
    E-ISSN: 2375-2548
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