More than just front or back: Parietal-striatal-thalamic circuits predict consciousness level (original) (raw)
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Central thalamus modulates consciousness by controlling layer-specific cortical interactions
Consciousness is the capacity to experience one's environment and internal states. The minimal mechanisms sufficient to produce this experience, the neural correlates of consciousness (NCC), are thought to involve thalamocortical and intracortical interactions, but the key operations and circuit paths are unclear. We simultaneously recorded neural activity in central thalamus and across layers of fronto-parietal cortex in awake, sleeping and anesthetized macaques. Spiking activity was selectively reduced in deep cortical layers and thalamus during unconsciousness, as were intracolumnar and interareal interactions at alpha and gamma frequencies. Gamma-frequency stimulation, when focused on the central lateral thalamus of anesthetized macaques, counteracted these neural changes and restored consciousness. These findings suggest that the NCC involve both corticocortical feedforward and feedback pathways coordinated with intracolumnar and thalamocortical loops.
PLOS Computational Biology
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 ...
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 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
The neuronal basis for consciousness
Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 1998
Attempting to understand how the brain, as a whole, might be organized seems, for the first time, to be a serious topic of inquiry. One aspect of its neuronal organization that seems particularly central to global function is the rich thalamocortical interconnectivity, and most particularly the reciprocal nature of the thalamocortical neuronal loop function. Moreover, the interaction between the specific and non-specific thalamic loops suggests that rather than a gate into the brain, the thalamus represents a hub from which any site in the cortex can communicate with any other such site or sites. The goal of this paper is to explore the basic assumption that large–scale, temporal coincidence of specific and non–specific thalamic activity generates the functional states that characterize human cognition.
Neural correlates of consciousness
A basic understanding of consciousness and its neural correlates is of major importance for all clinicians, especially those involved with patients with altered states of consciousness. In this paper it is shown that consciousness is dependent on the brainstem and thalamus for arousal; that basic cognition is supported by recurrent electrical activity between the cortex and the thalamus at gamma band frequencies; and that some kind of working memory must, at least fleetingly, be present for awareness to occur. The problem of cognitive binding and the role of attention are briefly addressed and it is shown that consciousness depends on a multitude of subconscious processes. Although these processes do not represent consciousness, consciousness cannot exist without them.
Consciousness and the thalamocortical loop
International Congress Series, 2003
Attempting to understand how the brain might be organized seems, for the first time, to be a serious topic of inquiry. One aspect of its neuronal organization that seems particularly central to global function is the rich thalamocortical interconnectivity and most particularly the reciprocal nature of the thalamocortical neuronal loop function. Moreover, the interaction between the specific and nonspecific thalamic loops suggests that rather than a gate into the brain, the thalamus represents a hub from which any site in the cortex can communicate with any other such site or sites. The goal of this paper is to explore the basic assumption that large-scale, temporal coincidence of specific and nonspecific thalamic activity generates the functional states that characterize human cognition.
Review: Neural correlates of consciousness
African Journal of Psychiatry, 2009
A basic understanding of consciousness and its neural correlates is of major importance for all clinicians, especially those involved with patients with altered states of consciousness. In this paper it is shown that consciousness is dependent on the brainstem and thalamus for arousal; that basic cognition is supported by recurrent electrical activity between the cortex and the thalamus at gamma band frequencies; and that some kind of working memory must, at least fleetingly, be present for awareness to occur. The problem of cognitive binding and the role of attention are briefly addressed and it is shown that consciousness depends on a multitude of subconscious processes. Although these processes do not represent consciousness, consciousness cannot exist without them.
A double anniversary for the neural correlates of consciousness: Editorial introduction
Philosophy and the Mind Sciences
This special issue celebrates the double anniversary of the neural correlates of consciousness (NCCs): 30 years since the research programme for finding neural correlates of consciousness was brought back onto the scientific agenda and 20 years since the standard definition of an NCC was published in a seminal anthology. Here, we take up some of the conceptual, methodological, and empirical questions raised and take stock of how the field has developed since then.
The neural correlates of consciousness
2003
Portas, C and Maquet, P and Rees, G and Blakemore, SJ and Frith, C (2003) The neural correlates of consciousness. In: Frackowiak, RSJ and Friston, KJ and Frith, CD and Dolan, RJ and Price, CJ and Zeki, S and Ashburner, J and Penny, W, (eds.) Human Brain Function. (269 - 301). Elsevier Press: London. ... Full text not available from this repository.
Neural correlates of consciousness in humans
2002
The directness and vivid quality of conscious experience belies the complexity of the underlying neural mechanisms, which remain incompletely understood. Recent work has focused on identifying the brain structures and patterns of neural activity within the primate visual system that are correlated with the content of visual consciousness.