Yuri Saalmann | University of Wisconsin-Madison (original) (raw)

Papers by Yuri Saalmann

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 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 Title: Receptors, circuits and neural dynamics for prediction

Learned associations between stimuli allow us to model the world and make predictions, crucial fo... more Learned associations between stimuli allow us to model the world and make predictions, crucial for efficient behavior; e.g., hearing a siren, we expect to see an ambulance and quickly make way. While theoretical and computational frameworks for prediction exist, circuit and receptor-level mechanisms are unclear. Using high-density 15 EEG and Bayesian modeling, we show that trial history and frontal alpha activity account for reaction times (a proxy for predictions) on a trial-by-trial basis in an audio-visual prediction task. Low-dose ketamine, a NMDA receptor blocker – but not the control drug dexmedetomidine – perturbed predictions, their representation in frontal cortex, and feedback to posterior cortex. This study suggests predictions depend on frontal alpha 20 activity and NMDA receptors, and ketamine blocks access to learned predictive information. One Sentence Summary: Predictions depend on NMDA receptors, representation in frontal cortex, and feedback to sensory cortex for c...

Research paper thumbnail of Integrated Network of Parietal Cortex, Striatum and Thalamus Predicts Level of Consciousness

SSRN Electronic Journal, 2020

The neural substrates of consciousness remain elusive. Competing theories that attempt to explain... more The neural substrates of consciousness remain elusive. Competing theories that attempt to explain consciousness disagree on the contribution of frontal versus posterior cortex, and omit subcortical influences. This lack of understanding impedes the ability to monitor consciousness, which can lead to adverse clinical consequences. To test substrates and measures of consciousness, we recorded simultaneously from frontal cortex, parietal cortex and subcortical structures, the striatum and thalamus, in awake, sleeping and anesthetized macaques. We manipulated consciousness on a finer scale using thalamic stimulation, rousing macaques from continuously administered anesthesia. Our results show that, unlike measures targeting complexity, a measure additionally capturing neural integration (Φ*) robustly correlated with changes in consciousness. Machine learning approaches show parietal cortex, striatum and thalamus contributed more than frontal cortex to decoding differences in consciousness. These findings highlight the importance of integration between parietal and subcortical structures, and challenge a key role for frontal cortex in consciousness.

Research paper thumbnail of Predictive feedback, early sensory representations and fast responses to predicted stimuli depend on NMDA receptors

Learned associations between stimuli allow us to model the world and make predictions, crucial fo... more Learned associations between stimuli allow us to model the world and make predictions, crucial for efficient behavior; e.g., hearing a siren, we expect to see an ambulance and quickly make way. While there are theoretical and computational frameworks for prediction, the circuit and receptor-level mechanisms are unclear. Using high-density EEG, Bayesian modeling and machine learning, we show that inferred “causal” relationships between stimuli and frontal alpha activity account for reaction times (a proxy for predictions) on a trial-by-trial basis in an audio-visual delayed match-to-sample task which elicited predictions. Predictive beta feedback activated sensory representations in advance of predicted stimuli. Low-dose ketamine, a NMDA receptor blocker – but not the control drug dexmedetomidine – perturbed behavioral indices of predictions, their representation in higher-order cortex, feedback to posterior cortex and pre-activation of sensory templates in higher-order sensory corte...

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

SSRN Electronic Journal, 2019

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 Pulvinar influences parietal delay activity and information transmission between dorsal and ventral visual cortex in macaques

The fronto-parietal attention network represents attentional priorities and provides feedback abo... more The fronto-parietal attention network represents attentional priorities and provides feedback about these priorities to sensory cortical areas. Sustained spiking activity in the posterior parietal cortex (PPC) carries such prioritized information, but how this activity is sustained in the absence of feedforward sensory information, and how it is transmitted to the ventral visual cortical pathway, is unclear. We hypothesized that the higher-order thalamic nucleus, the pulvinar, which is connected with both the PPC and ventral visual cortical pathway, influences information transmission within and between these cortical regions. To test this, we simultaneously recorded from the pulvinar, lateral intraparietal area (LIP) and visual cortical area V4 in macaques performing a selective attention task. Here we show that LIP influenced V4 during the delay period of the attention task, and that the pulvinar regulated LIP-V4 information exchange. Pulvino-cortical effects were consistent with ...

Research paper thumbnail of Temporal Dynamics and Response Modulation across the Human Visual System in a Spatial Attention Task: An ECoG Study

The Journal of Neuroscience, 2018

The selection of behaviorally relevant information from cluttered visual scenes (often referred t... more The selection of behaviorally relevant information from cluttered visual scenes (often referred to as "attention") is mediated by a cortical large-scale network consisting of areas in occipital, temporal, parietal, and frontal cortex that is organized into a functional hierarchy of feedforward and feedback pathways. In the human brain, little is known about the temporal dynamics of attentional processing from studies at the mesoscopic level of electrocorticography (ECoG), that combines millisecond temporal resolution with precise anatomical localization of recording sites. We analyzed high-frequency broadband responses (HFB) responses from 626 electrodes implanted in 8 epilepsy patients who performed a spatial attention task. Electrode locations were reconstructed using a probabilistic atlas of the human visual system. HFB responses showed high spatial selectivity and tuning, constituting ECoG response fields (RFs), within and outside the topographic visual system. In accordance with monkey physiology studies, both RF widths and onset latencies increased systematically across the visual processing hierarchy. We used the spatial specificity of HFB responses to quantitatively study spatial attention effects and their temporal dynamics to probe a hierarchical top-down model suggesting that feedback signals back propagate the visual processing hierarchy. Consistent with such a model, the strengths of attentional modulation were found to be greater and modulation latencies to be shorter in posterior parietal cortex, middle temporal cortex and ventral extrastriate cortex compared with early visual cortex. However, inconsistent with such a model, attention effects were weaker and more delayed in anterior parietal and frontal cortex.

Research paper thumbnail of Feedback from human posterior parietal cortex enables visuospatial category representations as early as primary visual cortex

Brain and behavior, 2018

Categorization is a fundamental cognitive process, whereby the brain assigns meaning to sensory s... more Categorization is a fundamental cognitive process, whereby the brain assigns meaning to sensory stimuli. Previous studies have found category representations in prefrontal cortex and posterior parietal cortex (PPC). However, these higher-order areas lack the fine-scale spatial representations of early sensory areas, and it remains unclear what mechanisms enable flexible categorization based on fine-scale features. In this study, we decoded functional MRI signals and measured causal influences, across visual, parietal, and prefrontal cortex from participants performing categorization based on coarse- or fine-scale spatial information in thirteen healthy adults. We show that category information based on coarse discriminations was represented in the PPC, in the intraparietal sulcus region, IPS1/2, at an early stage of categorization trials, whereas representations of category information based on fine-scale discriminations formed later during interactions between IPS1/2 and primary vi...

Research paper thumbnail of A Subcortical Pathway for Rapid, Goal-Driven, Attentional Filtering

Trends in Neurosciences, 2016

Research paper thumbnail of Neural Mechanisms of Spatial Attention in the Visual Thalamus

Oxford Handbooks Online, 2014

Neural mechanisms of selective attention route behaviourally relevant information through brain n... more Neural mechanisms of selective attention route behaviourally relevant information through brain networks for detailed processing. These attention mechanisms are classically viewed as being solely implemented in the cortex, relegating the thalamus to a passive relay of sensory information. However, this passive view of the thalamus is being revised in light of recent studies supporting an important role for the thalamus in selective attention. Evidence suggests that the first-order thalamic nucleus, the lateral geniculate nucleus, regulates the visual information transmitted from the retina to visual cortex, while the higher-order thalamic nucleus, the pulvinar, regulates information transmission between visual cortical areas, according to attentional demands. This chapter discusses how modulation of thalamic responses, switching the response mode of thalamic neurons, and changes in neural synchrony across thalamo-cortical networks contribute to selective attention.

Research paper thumbnail of The cognitive thalamus

Frontiers in systems neuroscience, 2015

Research paper thumbnail of Human fronto-parietal and parieto-hippocampal pathways represent behavioral priorities in multiple spatial reference frames

Bioarchitecture

We represent behaviorally relevant information in different spatial reference frames in order to ... more We represent behaviorally relevant information in different spatial reference frames in order to interact effectively with our environment. For example, we need an egocentric (e.g., body-centered) reference frame to specify limb movements and an allocentric (e.g., world-centered) reference frame to navigate from one location to another. Posterior parietal cortex (PPC) is vital for performing transformations between these different coordinate systems. Here, we review evidence for multiple pathways in the human brain, from PPC to motor, premotor, and supplementary motor areas, as well as to structures in the medial temporal lobe. These connections are important for transformations between egocentric reference frames to facilitate sensory-guided action, or from egocentric to allocentric reference frames to facilitate spatial navigation.

Research paper thumbnail of Thalamic Control of Visual Attention

The Neuroscience of AttentionAttentional Control and Selection, 2012

Page 70. 3 Thalamic Control of Visual Attention SABINE KASTNER, YURI B. SAALMANN, AND KEITH A. SC... more Page 70. 3 Thalamic Control of Visual Attention SABINE KASTNER, YURI B. SAALMANN, AND KEITH A. SCHNEIDER IN 1932, Le Gros Clark wrote about the thalamus: “Not only does the thalamus... determine a spa-tial location ...

Research paper thumbnail of The Pulvinar Regulates Information Transmission Between Cortical Areas Based on Attention Demands

Science, 2012

The Conductor in the Thalamus The pulvinar is the largest thalamic nucleus in the brain but its f... more The Conductor in the Thalamus The pulvinar is the largest thalamic nucleus in the brain but its functions remain unclear. The pulvinar is ideally positioned to synchronize activity across the visual cortex. Saalmann et al. (p. 753 ) combined diffusion tensor imaging with multi-electrode recordings from three different brain areas in monkeys to probe thalamo-cortical interactions during visual attention. The pulvinar was found to play a vital role in attention by routing behaviorally relevant information across the visual cortex.

Research paper thumbnail of Functional and structural architecture of the human dorsal frontoparietal attention network

Proceedings of the National Academy of Sciences, 2013

Significance Everyday actions require us to represent attentional priorities in different referen... more Significance Everyday actions require us to represent attentional priorities in different reference frames. For example, to pick up a cup of coffee, we need to know where the cup is relative to our body, and where the handle is relative to the cup (i.e., body-centered and object-centered reference frames). Multiple brain areas in frontal and parietal cortex help process attentional priorities. Although these areas are commonly conceptualized as an attentional network, it is not clear what neural pathways connect these areas, nor the pathways’ functions. We demonstrate that two pathways link these areas in frontal and parietal cortex. The pathways help represent attentional priorities in different reference frames, enabling us to flexibly interact with objects in our environment.

Research paper thumbnail of Electrophysiological Low-Frequency Coherence and Cross-Frequency Coupling Contribute to BOLD Connectivity

Neuron, 2012

Brain networks are commonly defined using correlations between blood oxygen level-dependent (BOLD... more Brain networks are commonly defined using correlations between blood oxygen level-dependent (BOLD) signals in different brain areas. Although evidence suggests that gamma-band (30-100 Hz) neural activity contributes to local BOLD signals, the neural basis of interareal BOLD correlations is unclear. We first defined a visual network in monkeys based on converging evidence from interareal BOLD correlations during a fixation task, task-free state, and anesthesia, and then simultaneously recorded local field potentials (LFPs) from the same four network areas in the task-free state. Low-frequency oscillations (<20 Hz), and not gamma activity, predominantly contributed to interareal BOLD correlations. The low-frequency oscillations also influenced local processing by modulating gamma activity within individual areas. We suggest that such cross-frequency coupling links local BOLD signals to BOLD correlations across distributed networks.

Research paper thumbnail of Cognitive and Perceptual Functions of the Visual Thalamus

Neuron, 2011

The thalamus is classically viewed as passively relaying information to the cortex. However, ther... more The thalamus is classically viewed as passively relaying information to the cortex. However, there is growing evidence that the thalamus actively regulates information transmission to the cortex and between cortical areas using a variety of mechanisms, including the modulation of response magnitude, firing mode, and synchrony of neurons according to behavioral demands. We discuss how the visual thalamus contributes to attention, awareness, and visually guided actions, to present a general role for the thalamus in perception and cognition. The [cortex] must depend entirely on the thalamus for the precise nature of the sensory material which it receives indirectly from peripheral receptors. It is true that there is evidence to indicate that cortical mechanisms can modify thalamic activities by inhibitory influences, but the fact remains that [.] the [cortex] from the developmental and functional point of view is to be regarded as a dependency of the thalamus and not vice versa.

Research paper thumbnail of Distracter filtering across the visual thalamocortical network

Research paper thumbnail of A role for the pulvinar in social cognition (Commentary on Nguyen et al .)

European Journal of Neuroscience, 2013

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 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 Title: Receptors, circuits and neural dynamics for prediction

Learned associations between stimuli allow us to model the world and make predictions, crucial fo... more Learned associations between stimuli allow us to model the world and make predictions, crucial for efficient behavior; e.g., hearing a siren, we expect to see an ambulance and quickly make way. While theoretical and computational frameworks for prediction exist, circuit and receptor-level mechanisms are unclear. Using high-density 15 EEG and Bayesian modeling, we show that trial history and frontal alpha activity account for reaction times (a proxy for predictions) on a trial-by-trial basis in an audio-visual prediction task. Low-dose ketamine, a NMDA receptor blocker – but not the control drug dexmedetomidine – perturbed predictions, their representation in frontal cortex, and feedback to posterior cortex. This study suggests predictions depend on frontal alpha 20 activity and NMDA receptors, and ketamine blocks access to learned predictive information. One Sentence Summary: Predictions depend on NMDA receptors, representation in frontal cortex, and feedback to sensory cortex for c...

Research paper thumbnail of Integrated Network of Parietal Cortex, Striatum and Thalamus Predicts Level of Consciousness

SSRN Electronic Journal, 2020

The neural substrates of consciousness remain elusive. Competing theories that attempt to explain... more The neural substrates of consciousness remain elusive. Competing theories that attempt to explain consciousness disagree on the contribution of frontal versus posterior cortex, and omit subcortical influences. This lack of understanding impedes the ability to monitor consciousness, which can lead to adverse clinical consequences. To test substrates and measures of consciousness, we recorded simultaneously from frontal cortex, parietal cortex and subcortical structures, the striatum and thalamus, in awake, sleeping and anesthetized macaques. We manipulated consciousness on a finer scale using thalamic stimulation, rousing macaques from continuously administered anesthesia. Our results show that, unlike measures targeting complexity, a measure additionally capturing neural integration (Φ*) robustly correlated with changes in consciousness. Machine learning approaches show parietal cortex, striatum and thalamus contributed more than frontal cortex to decoding differences in consciousness. These findings highlight the importance of integration between parietal and subcortical structures, and challenge a key role for frontal cortex in consciousness.

Research paper thumbnail of Predictive feedback, early sensory representations and fast responses to predicted stimuli depend on NMDA receptors

Learned associations between stimuli allow us to model the world and make predictions, crucial fo... more Learned associations between stimuli allow us to model the world and make predictions, crucial for efficient behavior; e.g., hearing a siren, we expect to see an ambulance and quickly make way. While there are theoretical and computational frameworks for prediction, the circuit and receptor-level mechanisms are unclear. Using high-density EEG, Bayesian modeling and machine learning, we show that inferred “causal” relationships between stimuli and frontal alpha activity account for reaction times (a proxy for predictions) on a trial-by-trial basis in an audio-visual delayed match-to-sample task which elicited predictions. Predictive beta feedback activated sensory representations in advance of predicted stimuli. Low-dose ketamine, a NMDA receptor blocker – but not the control drug dexmedetomidine – perturbed behavioral indices of predictions, their representation in higher-order cortex, feedback to posterior cortex and pre-activation of sensory templates in higher-order sensory corte...

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

SSRN Electronic Journal, 2019

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 Pulvinar influences parietal delay activity and information transmission between dorsal and ventral visual cortex in macaques

The fronto-parietal attention network represents attentional priorities and provides feedback abo... more The fronto-parietal attention network represents attentional priorities and provides feedback about these priorities to sensory cortical areas. Sustained spiking activity in the posterior parietal cortex (PPC) carries such prioritized information, but how this activity is sustained in the absence of feedforward sensory information, and how it is transmitted to the ventral visual cortical pathway, is unclear. We hypothesized that the higher-order thalamic nucleus, the pulvinar, which is connected with both the PPC and ventral visual cortical pathway, influences information transmission within and between these cortical regions. To test this, we simultaneously recorded from the pulvinar, lateral intraparietal area (LIP) and visual cortical area V4 in macaques performing a selective attention task. Here we show that LIP influenced V4 during the delay period of the attention task, and that the pulvinar regulated LIP-V4 information exchange. Pulvino-cortical effects were consistent with ...

Research paper thumbnail of Temporal Dynamics and Response Modulation across the Human Visual System in a Spatial Attention Task: An ECoG Study

The Journal of Neuroscience, 2018

The selection of behaviorally relevant information from cluttered visual scenes (often referred t... more The selection of behaviorally relevant information from cluttered visual scenes (often referred to as "attention") is mediated by a cortical large-scale network consisting of areas in occipital, temporal, parietal, and frontal cortex that is organized into a functional hierarchy of feedforward and feedback pathways. In the human brain, little is known about the temporal dynamics of attentional processing from studies at the mesoscopic level of electrocorticography (ECoG), that combines millisecond temporal resolution with precise anatomical localization of recording sites. We analyzed high-frequency broadband responses (HFB) responses from 626 electrodes implanted in 8 epilepsy patients who performed a spatial attention task. Electrode locations were reconstructed using a probabilistic atlas of the human visual system. HFB responses showed high spatial selectivity and tuning, constituting ECoG response fields (RFs), within and outside the topographic visual system. In accordance with monkey physiology studies, both RF widths and onset latencies increased systematically across the visual processing hierarchy. We used the spatial specificity of HFB responses to quantitatively study spatial attention effects and their temporal dynamics to probe a hierarchical top-down model suggesting that feedback signals back propagate the visual processing hierarchy. Consistent with such a model, the strengths of attentional modulation were found to be greater and modulation latencies to be shorter in posterior parietal cortex, middle temporal cortex and ventral extrastriate cortex compared with early visual cortex. However, inconsistent with such a model, attention effects were weaker and more delayed in anterior parietal and frontal cortex.

Research paper thumbnail of Feedback from human posterior parietal cortex enables visuospatial category representations as early as primary visual cortex

Brain and behavior, 2018

Categorization is a fundamental cognitive process, whereby the brain assigns meaning to sensory s... more Categorization is a fundamental cognitive process, whereby the brain assigns meaning to sensory stimuli. Previous studies have found category representations in prefrontal cortex and posterior parietal cortex (PPC). However, these higher-order areas lack the fine-scale spatial representations of early sensory areas, and it remains unclear what mechanisms enable flexible categorization based on fine-scale features. In this study, we decoded functional MRI signals and measured causal influences, across visual, parietal, and prefrontal cortex from participants performing categorization based on coarse- or fine-scale spatial information in thirteen healthy adults. We show that category information based on coarse discriminations was represented in the PPC, in the intraparietal sulcus region, IPS1/2, at an early stage of categorization trials, whereas representations of category information based on fine-scale discriminations formed later during interactions between IPS1/2 and primary vi...

Research paper thumbnail of A Subcortical Pathway for Rapid, Goal-Driven, Attentional Filtering

Trends in Neurosciences, 2016

Research paper thumbnail of Neural Mechanisms of Spatial Attention in the Visual Thalamus

Oxford Handbooks Online, 2014

Neural mechanisms of selective attention route behaviourally relevant information through brain n... more Neural mechanisms of selective attention route behaviourally relevant information through brain networks for detailed processing. These attention mechanisms are classically viewed as being solely implemented in the cortex, relegating the thalamus to a passive relay of sensory information. However, this passive view of the thalamus is being revised in light of recent studies supporting an important role for the thalamus in selective attention. Evidence suggests that the first-order thalamic nucleus, the lateral geniculate nucleus, regulates the visual information transmitted from the retina to visual cortex, while the higher-order thalamic nucleus, the pulvinar, regulates information transmission between visual cortical areas, according to attentional demands. This chapter discusses how modulation of thalamic responses, switching the response mode of thalamic neurons, and changes in neural synchrony across thalamo-cortical networks contribute to selective attention.

Research paper thumbnail of The cognitive thalamus

Frontiers in systems neuroscience, 2015

Research paper thumbnail of Human fronto-parietal and parieto-hippocampal pathways represent behavioral priorities in multiple spatial reference frames

Bioarchitecture

We represent behaviorally relevant information in different spatial reference frames in order to ... more We represent behaviorally relevant information in different spatial reference frames in order to interact effectively with our environment. For example, we need an egocentric (e.g., body-centered) reference frame to specify limb movements and an allocentric (e.g., world-centered) reference frame to navigate from one location to another. Posterior parietal cortex (PPC) is vital for performing transformations between these different coordinate systems. Here, we review evidence for multiple pathways in the human brain, from PPC to motor, premotor, and supplementary motor areas, as well as to structures in the medial temporal lobe. These connections are important for transformations between egocentric reference frames to facilitate sensory-guided action, or from egocentric to allocentric reference frames to facilitate spatial navigation.

Research paper thumbnail of Thalamic Control of Visual Attention

The Neuroscience of AttentionAttentional Control and Selection, 2012

Page 70. 3 Thalamic Control of Visual Attention SABINE KASTNER, YURI B. SAALMANN, AND KEITH A. SC... more Page 70. 3 Thalamic Control of Visual Attention SABINE KASTNER, YURI B. SAALMANN, AND KEITH A. SCHNEIDER IN 1932, Le Gros Clark wrote about the thalamus: “Not only does the thalamus... determine a spa-tial location ...

Research paper thumbnail of The Pulvinar Regulates Information Transmission Between Cortical Areas Based on Attention Demands

Science, 2012

The Conductor in the Thalamus The pulvinar is the largest thalamic nucleus in the brain but its f... more The Conductor in the Thalamus The pulvinar is the largest thalamic nucleus in the brain but its functions remain unclear. The pulvinar is ideally positioned to synchronize activity across the visual cortex. Saalmann et al. (p. 753 ) combined diffusion tensor imaging with multi-electrode recordings from three different brain areas in monkeys to probe thalamo-cortical interactions during visual attention. The pulvinar was found to play a vital role in attention by routing behaviorally relevant information across the visual cortex.

Research paper thumbnail of Functional and structural architecture of the human dorsal frontoparietal attention network

Proceedings of the National Academy of Sciences, 2013

Significance Everyday actions require us to represent attentional priorities in different referen... more Significance Everyday actions require us to represent attentional priorities in different reference frames. For example, to pick up a cup of coffee, we need to know where the cup is relative to our body, and where the handle is relative to the cup (i.e., body-centered and object-centered reference frames). Multiple brain areas in frontal and parietal cortex help process attentional priorities. Although these areas are commonly conceptualized as an attentional network, it is not clear what neural pathways connect these areas, nor the pathways’ functions. We demonstrate that two pathways link these areas in frontal and parietal cortex. The pathways help represent attentional priorities in different reference frames, enabling us to flexibly interact with objects in our environment.

Research paper thumbnail of Electrophysiological Low-Frequency Coherence and Cross-Frequency Coupling Contribute to BOLD Connectivity

Neuron, 2012

Brain networks are commonly defined using correlations between blood oxygen level-dependent (BOLD... more Brain networks are commonly defined using correlations between blood oxygen level-dependent (BOLD) signals in different brain areas. Although evidence suggests that gamma-band (30-100 Hz) neural activity contributes to local BOLD signals, the neural basis of interareal BOLD correlations is unclear. We first defined a visual network in monkeys based on converging evidence from interareal BOLD correlations during a fixation task, task-free state, and anesthesia, and then simultaneously recorded local field potentials (LFPs) from the same four network areas in the task-free state. Low-frequency oscillations (<20 Hz), and not gamma activity, predominantly contributed to interareal BOLD correlations. The low-frequency oscillations also influenced local processing by modulating gamma activity within individual areas. We suggest that such cross-frequency coupling links local BOLD signals to BOLD correlations across distributed networks.

Research paper thumbnail of Cognitive and Perceptual Functions of the Visual Thalamus

Neuron, 2011

The thalamus is classically viewed as passively relaying information to the cortex. However, ther... more The thalamus is classically viewed as passively relaying information to the cortex. However, there is growing evidence that the thalamus actively regulates information transmission to the cortex and between cortical areas using a variety of mechanisms, including the modulation of response magnitude, firing mode, and synchrony of neurons according to behavioral demands. We discuss how the visual thalamus contributes to attention, awareness, and visually guided actions, to present a general role for the thalamus in perception and cognition. The [cortex] must depend entirely on the thalamus for the precise nature of the sensory material which it receives indirectly from peripheral receptors. It is true that there is evidence to indicate that cortical mechanisms can modify thalamic activities by inhibitory influences, but the fact remains that [.] the [cortex] from the developmental and functional point of view is to be regarded as a dependency of the thalamus and not vice versa.

Research paper thumbnail of Distracter filtering across the visual thalamocortical network

Research paper thumbnail of A role for the pulvinar in social cognition (Commentary on Nguyen et al .)

European Journal of Neuroscience, 2013