Yuri Saalmann - Academia.edu (original) (raw)

Papers by Yuri Saalmann

Research paper thumbnail of Layer-specific reorganization of mnemonic representations in primate retrosplenial cortex during learning

bioRxiv (Cold Spring Harbor Laboratory), Jul 2, 2024

Research paper thumbnail of Primate thalamic nuclei select abstract rules and shape prefrontal dynamics

bioRxiv (Cold Spring Harbor Laboratory), Mar 14, 2024

Research paper thumbnail of Cellular Distribution of the GABA<sub>A</sub>Receptor-Modulating 3?-Hydroxy, 5?-Reduced Pregnane Steroids in the Adult Rat Brain

Journal of Neuroendocrinology, Apr 1, 2007

The 3α‐hydroxy,5α‐reduced pregnane steroids, allopregnanolone and allotetrahydrodeoxycorticostero... more The 3α‐hydroxy,5α‐reduced pregnane steroids, allopregnanolone and allotetrahydrodeoxycorticosterone, are the most potent endogenous positive modulators of GABAA receptor‐mediated inhibition. This study presents the first immunohistochemical examination of the cellular distribution of 3α‐hydroxy,5α‐reduced pregnane steroids across the brain. We found a widespread distribution in the adult rat, with dense immunolabelling in the olfactory bulb, striatum and cerebral cortex, and lower density labelling in the brainstem reticular formation. In general terms, this distribution accords with the regional concentrations of 3α‐hydroxy,5α‐reduced steroids determined, in other laboratories, by brain region sampling and either gas chromatography‐mass fragmentography or radioimmunoassay. However, immunohistochemistry allowed for a more detailed examination of regional distribution and cellular specificity. All immunoreactivity was confined to the cell bodies and thick dendrites of neurones; no identifiable glia were labelled. In most brain areas, the location and morphology of labelled cells identified them as excitatory neurones. In addition, cell populations known to be projecting GABAergic neurones (e.g. cerebellar Purkinje cells) were immunoreactive, whereas local inhibitory neurones generally were not. The cellular distribution of 3α‐hydroxy,5α‐reduced steroids suggests that sensory, motor, limbic and homeostatic systems can be influenced by neurosteroids at multiple stages of processing.

Research paper thumbnail of The non-specific matrix thalamus facilitates the cortical information processing modes relevant for conscious awareness

Cell Reports, Aug 1, 2023

Research paper thumbnail of Brain Circuitry of Consciousness: A Review of Current Models and a Novel Synergistic Model With Clinical Application

PubMed, Jun 1, 2023

How consciousness arises in the brain has important implications for clinical decision-making. We... more How consciousness arises in the brain has important implications for clinical decision-making. We summarize recent findings in consciousness studies to provide a toolkit for clinicians to assess deficits in consciousness and predict outcomes after brain injury. Commonly encountered disorders of consciousness are highlighted, followed by the clinical scales currently used to diagnose them. We review recent evidence describing the roles of the thalamocortical system and brainstem arousal nuclei in supporting awareness and arousal and discuss the utility of various neuroimaging studies in evaluating disorders of consciousness. We explore recent theoretical progress in mechanistic models of consciousness, focusing on 2 major models, the global neuronal workspace and integrated information theory, and review areas of controversy. Finally, we consider the potential implications of recent research for the day-to-day decision-making of clinical neurosurgeons and propose a simple "three-strikes" model to infer the integrity of the thalamocortical system, which can guide prognosticating return to consciousness.

Research paper thumbnail of Thalamus Modulates Consciousness via Layer-Specific Control of Cortex

Neuron, Apr 1, 2020

Highlights d Central lateral thalamic stimulation arouses macaques from stable anesthesia d Thala... more Highlights d Central lateral thalamic stimulation arouses macaques from stable anesthesia d Thalamic and deep-layer cortical spiking correlate with consciousness level d Consciousness depends on feedforward, feedback, and intracolumnar signaling d Pathway-specific signaling operates at alpha and gamma during consciousness

Research paper thumbnail of Dynamics of coherent activity between cortical areas defines a two-stage process of selective attention

Analysing a visual scene requires the brain to briefly keep in memory potentially relevant parts ... more Analysing a visual scene requires the brain to briefly keep in memory potentially relevant parts and then direct attention to their locations for detailed processing. To reveal the neuronal basis of the underlying working memory and top-down attention processes, we trained macaques to match two patterns presented with a preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.

Research paper thumbnail of Subanaesthetic doses of ketamine reduce, but do not eliminate, predictive coding responses: implications for mechanisms of sensory disconnection

BJA: British Journal of Anaesthesia, Aug 1, 2023

Research paper thumbnail of In memoriam: Professor Ivan Pigarev (1941-2021)

Journal of Sleep Research, Oct 19, 2021

Research paper thumbnail of Faculty Opinions recommendation of Guarding the gateway to cortex with attention in visual thalamus

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature, Jan 21, 2009

Research paper thumbnail of Dynamics of coherent activity between cortical areas defines a two-stage process of top-down attention

Experimental Brain Research, Jul 9, 2021

Analysing a visual scene requires the brain to briefly keep in memory potentially relevant items ... more Analysing a visual scene requires the brain to briefly keep in memory potentially relevant items of that scene and then direct attention to their locations for detailed processing. To reveal the neuronal basis of the underlying working memory and top-down attention processes, we trained macaques to match two patterns presented with a delay between them. As the above processes are likely to require communication between brain regions, and the parietal cortex is known to be involved in spatial attention, we simultaneously recorded neuronal activities from the interconnected parietal and middle temporal areas. We found that mnemonic information about features of the first pattern was retained in coherent oscillating activity between the two areas in high-frequency bands, followed by coherent activity in lower frequency bands mediating top-down attention on the relevant spatial location. Oscillations maintaining featural information also modulated activity of the cells of the parietal cortex that mediate attention. This could potentially enable transfer of information to organize top-down signals necessary for selective attention. Our results provide evidence in support of a two-stage model of visual attention where the first stage involves creating a saliency map representing a visual scene and at the second stage attentional feedback is provided to cortical areas involved in detailed analysis of the attended parts of a scene.

Research paper thumbnail of Dynamic causal modelling of auditory surprise during disconnected consciousness: The role of feedback connectivity

Research paper thumbnail of Faculty of 1000 evaluation for The corticothalamocortical circuit drives higher-order cortex in the mouse

F1000 - Post-publication peer review of the biomedical literature, 2010

Research paper thumbnail of Thalamic deep brain stimulation paradigm to reduce consciousness: Cortico-striatal dynamics implicated in mechanisms of consciousness

PLOS Computational Biology

Anesthetic manipulations provide much-needed causal evidence for neural correlates of consciousne... more Anesthetic manipulations provide much-needed causal evidence for neural correlates of consciousness, but non-specific drug effects complicate their interpretation. Evidence suggests that thalamic deep brain stimulation (DBS) can either increase or decrease consciousness, depending on the stimulation target and parameters. The putative role of the central lateral thalamus (CL) in consciousness makes it an ideal DBS target to manipulate circuit-level mechanisms in cortico-striato-thalamic (CST) systems, thereby influencing consciousness and related processes. We used multi-microelectrode DBS targeted to CL in macaques while recording from frontal, parietal, and striatal regions. DBS induced episodes of abnormally long, vacant staring with low-frequency oscillations here termed vacant, perturbed consciousness (VPC). DBS modulated VPC likelihood in a frequency-specific manner. VPC events corresponded to decreases in measures of neural complexity (entropy) and integration (Φ*), proposed ...

Research paper thumbnail of Mapping the Hierarchical Neural Network of 3D Vision using Diffusion Tensor Imaging

Research paper thumbnail of Modulation of intracranial field potential responses in the human large-scale attention network during a spatial attention task

Journal of vision, 2015

Spatial attention is mediated through a large-scale network that includes occipital, temporal, pa... more Spatial attention is mediated through a large-scale network that includes occipital, temporal, parietal and frontal cortical regions. While the network architecture has been well characterized using neuroimaging methods, less is known about the temporal dynamics in local regions and across the network. Here, we explored the modulatory effects of spatial attention throughout this cortical network by analyzing intracranial field potentials recorded from 538 ECoG electrodes implanted in 6 epilepsy patients. We examined the effects of attention using a variant of the Eriksen flanker task, where subjects were cued by an exogenous stimulus to the spatial location of an upcoming target stimulus which, after a variable delay period, was presented embedded in a circular array of shapes. Subjects had to differentiate between barrel or bowtie target stimuli flanked either by congruent or incongruent shapes. Using our probabilistic atlas of the human visual system, we localized the recorded ECo...

Research paper thumbnail of Supplementary Materials

Research paper thumbnail of Microscale Multicircuit Brain Stimulation: Achieving Real-Time Brain State Control For Novel Applications

Research paper thumbnail of More than just front or back: Parietal-striatal-thalamic circuits predict consciousness level

Major theories of consciousness disagree on the key neural substrates. In Global Neuronal Workspa... more Major theories of consciousness disagree on the key neural substrates. In Global Neuronal Workspace Theory and Higher-order Theories, consciousness depends on frontal cortex, whereas Integrated Information Theory and Recurrent Processing Theory highlight posterior contributions. Most theories omit subcortical influences. To test these theories, we performed simultaneous frontal, parietal, striatal and thalamic recordings from awake, sleeping and anesthetized macaques, further manipulating consciousness with deep-brain thalamic stimulation. Information theoretic measures and machine learning approaches suggested parietal cortex, striatum and thalamus contribute more to consciousness level than frontal cortex. While these findings provide greater support for Integrated Information Theory than the others, the theory does not incorporate subcortical structures such as the striatum. We therefore propose that thalamo-striatal circuits have a cause-effect structure to generate integrated i...

Research paper thumbnail of Thalamic deep brain stimulation as a paradigm to reduce consciousness: implications for cortico-striatal dynamics, absence epilepsy and consciousness studies

ABSTRACTAnesthetic manipulations provide much-needed causal evidence for neural correlates of con... more ABSTRACTAnesthetic manipulations provide much-needed causal evidence for neural correlates of consciousness, but non-specific drug effects complicate their interpretation. Evidence suggests that thalamic deep brain stimulation (DBS) can either increase or decrease consciousness, depending on the stimulation target and parameters. The putative role of the central lateral thalamus (CL) in consciousness makes it an ideal DBS target to manipulate circuit-level mechanisms in cortico-striato-thalamic (CST) systems, thereby influencing consciousness and related processes. We used multi-microelectrode DBS targeted to CL in macaques while recording from frontal, parietal, and striatal regions. DBS induced episodes reminiscent of absence epilepsy, here termed absence-like activity (ALA), with decreased behavior and vacant staring coinciding with low-frequency oscillations. DBS modulated ALA likelihood in a frequency-specific manner. ALA events corresponded to decreases in measures of neural c...

Research paper thumbnail of Layer-specific reorganization of mnemonic representations in primate retrosplenial cortex during learning

bioRxiv (Cold Spring Harbor Laboratory), Jul 2, 2024

Research paper thumbnail of Primate thalamic nuclei select abstract rules and shape prefrontal dynamics

bioRxiv (Cold Spring Harbor Laboratory), Mar 14, 2024

Research paper thumbnail of Cellular Distribution of the GABA<sub>A</sub>Receptor-Modulating 3?-Hydroxy, 5?-Reduced Pregnane Steroids in the Adult Rat Brain

Journal of Neuroendocrinology, Apr 1, 2007

The 3α‐hydroxy,5α‐reduced pregnane steroids, allopregnanolone and allotetrahydrodeoxycorticostero... more The 3α‐hydroxy,5α‐reduced pregnane steroids, allopregnanolone and allotetrahydrodeoxycorticosterone, are the most potent endogenous positive modulators of GABAA receptor‐mediated inhibition. This study presents the first immunohistochemical examination of the cellular distribution of 3α‐hydroxy,5α‐reduced pregnane steroids across the brain. We found a widespread distribution in the adult rat, with dense immunolabelling in the olfactory bulb, striatum and cerebral cortex, and lower density labelling in the brainstem reticular formation. In general terms, this distribution accords with the regional concentrations of 3α‐hydroxy,5α‐reduced steroids determined, in other laboratories, by brain region sampling and either gas chromatography‐mass fragmentography or radioimmunoassay. However, immunohistochemistry allowed for a more detailed examination of regional distribution and cellular specificity. All immunoreactivity was confined to the cell bodies and thick dendrites of neurones; no identifiable glia were labelled. In most brain areas, the location and morphology of labelled cells identified them as excitatory neurones. In addition, cell populations known to be projecting GABAergic neurones (e.g. cerebellar Purkinje cells) were immunoreactive, whereas local inhibitory neurones generally were not. The cellular distribution of 3α‐hydroxy,5α‐reduced steroids suggests that sensory, motor, limbic and homeostatic systems can be influenced by neurosteroids at multiple stages of processing.

Research paper thumbnail of The non-specific matrix thalamus facilitates the cortical information processing modes relevant for conscious awareness

Cell Reports, Aug 1, 2023

Research paper thumbnail of Brain Circuitry of Consciousness: A Review of Current Models and a Novel Synergistic Model With Clinical Application

PubMed, Jun 1, 2023

How consciousness arises in the brain has important implications for clinical decision-making. We... more How consciousness arises in the brain has important implications for clinical decision-making. We summarize recent findings in consciousness studies to provide a toolkit for clinicians to assess deficits in consciousness and predict outcomes after brain injury. Commonly encountered disorders of consciousness are highlighted, followed by the clinical scales currently used to diagnose them. We review recent evidence describing the roles of the thalamocortical system and brainstem arousal nuclei in supporting awareness and arousal and discuss the utility of various neuroimaging studies in evaluating disorders of consciousness. We explore recent theoretical progress in mechanistic models of consciousness, focusing on 2 major models, the global neuronal workspace and integrated information theory, and review areas of controversy. Finally, we consider the potential implications of recent research for the day-to-day decision-making of clinical neurosurgeons and propose a simple "three-strikes" model to infer the integrity of the thalamocortical system, which can guide prognosticating return to consciousness.

Research paper thumbnail of Thalamus Modulates Consciousness via Layer-Specific Control of Cortex

Neuron, Apr 1, 2020

Highlights d Central lateral thalamic stimulation arouses macaques from stable anesthesia d Thala... more Highlights d Central lateral thalamic stimulation arouses macaques from stable anesthesia d Thalamic and deep-layer cortical spiking correlate with consciousness level d Consciousness depends on feedforward, feedback, and intracolumnar signaling d Pathway-specific signaling operates at alpha and gamma during consciousness

Research paper thumbnail of Dynamics of coherent activity between cortical areas defines a two-stage process of selective attention

Analysing a visual scene requires the brain to briefly keep in memory potentially relevant parts ... more Analysing a visual scene requires the brain to briefly keep in memory potentially relevant parts and then direct attention to their locations for detailed processing. To reveal the neuronal basis of the underlying working memory and top-down attention processes, we trained macaques to match two patterns presented with a preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.

Research paper thumbnail of Subanaesthetic doses of ketamine reduce, but do not eliminate, predictive coding responses: implications for mechanisms of sensory disconnection

BJA: British Journal of Anaesthesia, Aug 1, 2023

Research paper thumbnail of In memoriam: Professor Ivan Pigarev (1941-2021)

Journal of Sleep Research, Oct 19, 2021

Research paper thumbnail of Faculty Opinions recommendation of Guarding the gateway to cortex with attention in visual thalamus

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature, Jan 21, 2009

Research paper thumbnail of Dynamics of coherent activity between cortical areas defines a two-stage process of top-down attention

Experimental Brain Research, Jul 9, 2021

Analysing a visual scene requires the brain to briefly keep in memory potentially relevant items ... more Analysing a visual scene requires the brain to briefly keep in memory potentially relevant items of that scene and then direct attention to their locations for detailed processing. To reveal the neuronal basis of the underlying working memory and top-down attention processes, we trained macaques to match two patterns presented with a delay between them. As the above processes are likely to require communication between brain regions, and the parietal cortex is known to be involved in spatial attention, we simultaneously recorded neuronal activities from the interconnected parietal and middle temporal areas. We found that mnemonic information about features of the first pattern was retained in coherent oscillating activity between the two areas in high-frequency bands, followed by coherent activity in lower frequency bands mediating top-down attention on the relevant spatial location. Oscillations maintaining featural information also modulated activity of the cells of the parietal cortex that mediate attention. This could potentially enable transfer of information to organize top-down signals necessary for selective attention. Our results provide evidence in support of a two-stage model of visual attention where the first stage involves creating a saliency map representing a visual scene and at the second stage attentional feedback is provided to cortical areas involved in detailed analysis of the attended parts of a scene.

Research paper thumbnail of Dynamic causal modelling of auditory surprise during disconnected consciousness: The role of feedback connectivity

Research paper thumbnail of Faculty of 1000 evaluation for The corticothalamocortical circuit drives higher-order cortex in the mouse

F1000 - Post-publication peer review of the biomedical literature, 2010

Research paper thumbnail of Thalamic deep brain stimulation paradigm to reduce consciousness: Cortico-striatal dynamics implicated in mechanisms of consciousness

PLOS Computational Biology

Anesthetic manipulations provide much-needed causal evidence for neural correlates of consciousne... more Anesthetic manipulations provide much-needed causal evidence for neural correlates of consciousness, but non-specific drug effects complicate their interpretation. Evidence suggests that thalamic deep brain stimulation (DBS) can either increase or decrease consciousness, depending on the stimulation target and parameters. The putative role of the central lateral thalamus (CL) in consciousness makes it an ideal DBS target to manipulate circuit-level mechanisms in cortico-striato-thalamic (CST) systems, thereby influencing consciousness and related processes. We used multi-microelectrode DBS targeted to CL in macaques while recording from frontal, parietal, and striatal regions. DBS induced episodes of abnormally long, vacant staring with low-frequency oscillations here termed vacant, perturbed consciousness (VPC). DBS modulated VPC likelihood in a frequency-specific manner. VPC events corresponded to decreases in measures of neural complexity (entropy) and integration (Φ*), proposed ...

Research paper thumbnail of Mapping the Hierarchical Neural Network of 3D Vision using Diffusion Tensor Imaging

Research paper thumbnail of Modulation of intracranial field potential responses in the human large-scale attention network during a spatial attention task

Journal of vision, 2015

Spatial attention is mediated through a large-scale network that includes occipital, temporal, pa... more Spatial attention is mediated through a large-scale network that includes occipital, temporal, parietal and frontal cortical regions. While the network architecture has been well characterized using neuroimaging methods, less is known about the temporal dynamics in local regions and across the network. Here, we explored the modulatory effects of spatial attention throughout this cortical network by analyzing intracranial field potentials recorded from 538 ECoG electrodes implanted in 6 epilepsy patients. We examined the effects of attention using a variant of the Eriksen flanker task, where subjects were cued by an exogenous stimulus to the spatial location of an upcoming target stimulus which, after a variable delay period, was presented embedded in a circular array of shapes. Subjects had to differentiate between barrel or bowtie target stimuli flanked either by congruent or incongruent shapes. Using our probabilistic atlas of the human visual system, we localized the recorded ECo...

Research paper thumbnail of Supplementary Materials

Research paper thumbnail of Microscale Multicircuit Brain Stimulation: Achieving Real-Time Brain State Control For Novel Applications

Research paper thumbnail of More than just front or back: Parietal-striatal-thalamic circuits predict consciousness level

Major theories of consciousness disagree on the key neural substrates. In Global Neuronal Workspa... more Major theories of consciousness disagree on the key neural substrates. In Global Neuronal Workspace Theory and Higher-order Theories, consciousness depends on frontal cortex, whereas Integrated Information Theory and Recurrent Processing Theory highlight posterior contributions. Most theories omit subcortical influences. To test these theories, we performed simultaneous frontal, parietal, striatal and thalamic recordings from awake, sleeping and anesthetized macaques, further manipulating consciousness with deep-brain thalamic stimulation. Information theoretic measures and machine learning approaches suggested parietal cortex, striatum and thalamus contribute more to consciousness level than frontal cortex. While these findings provide greater support for Integrated Information Theory than the others, the theory does not incorporate subcortical structures such as the striatum. We therefore propose that thalamo-striatal circuits have a cause-effect structure to generate integrated i...

Research paper thumbnail of Thalamic deep brain stimulation as a paradigm to reduce consciousness: implications for cortico-striatal dynamics, absence epilepsy and consciousness studies

ABSTRACTAnesthetic manipulations provide much-needed causal evidence for neural correlates of con... more ABSTRACTAnesthetic manipulations provide much-needed causal evidence for neural correlates of consciousness, but non-specific drug effects complicate their interpretation. Evidence suggests that thalamic deep brain stimulation (DBS) can either increase or decrease consciousness, depending on the stimulation target and parameters. The putative role of the central lateral thalamus (CL) in consciousness makes it an ideal DBS target to manipulate circuit-level mechanisms in cortico-striato-thalamic (CST) systems, thereby influencing consciousness and related processes. We used multi-microelectrode DBS targeted to CL in macaques while recording from frontal, parietal, and striatal regions. DBS induced episodes reminiscent of absence epilepsy, here termed absence-like activity (ALA), with decreased behavior and vacant staring coinciding with low-frequency oscillations. DBS modulated ALA likelihood in a frequency-specific manner. ALA events corresponded to decreases in measures of neural c...