When the Brain Loses Its Self: Prefrontal Inactivation during Sensorimotor Processing
TL;DR: The results support the notion that self-related processes are not necessarily engaged during sensory perception and can be actually suppressed, and show a complete segregation between the two patterns of activity.
About: This article is published in Neuron.The article was published on 2006-04-20 and is currently open access. It has received 552 citations till now. The article focuses on the topics: Perception & Brain activity and meditation.
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TL;DR: Evidence is presented that self‐generated thought is a multifaceted construct whose component processes are supported by different subsystems within the network, and clinical implications of disruptions to the integrity of the network are discussed.
Abstract: Though only a decade has elapsed since the default network (DN) was first defined as a large-scale brain system, recent years have brought great insight into the network's adaptive functions. A growing theme highlights the DN as playing a key role in internally directed or self-generated thought. Here, we synthesize recent findings from cognitive science, neuroscience, and clinical psychology to focus attention on two emerging topics as current and future directions surrounding the DN. First, we present evidence that self-generated thought is a multifaceted construct whose component processes are supported by different subsystems within the network. Second, we highlight the dynamic nature of the DN, emphasizing its interaction with executive control systems when regulating aspects of internal thought. We conclude by discussing clinical implications of disruptions to the integrity of the network, and consider disorders when thought content becomes polarized or network interactions become disrupted or imbalanced.
1,471 citations
TL;DR: How integrated information theory accounts for several aspects of the relationship between consciousness and the brain is discussed and can be used to develop new tools for assessing consciousness in non-communicative patients.
Abstract: Uncovering the neural basis of consciousness is a major challenge to neuroscience. In this Perspective, Tononi and colleagues describe the integrated information theory of consciousness and how it might be used to answer outstanding questions about the nature of consciousness. In this Opinion article, we discuss how integrated information theory accounts for several aspects of the relationship between consciousness and the brain. Integrated information theory starts from the essential properties of phenomenal experience, from which it derives the requirements for the physical substrate of consciousness. It argues that the physical substrate of consciousness must be a maximum of intrinsic cause–effect power and provides a means to determine, in principle, the quality and quantity of experience. The theory leads to some counterintuitive predictions and can be used to develop new tools for assessing consciousness in non-communicative patients.
928 citations
TL;DR: This target article argues for an abstract solution to the problem and exhibits a source of empirical data that is relevant, data that show that in a certain sense phenomenal consciousness overflows cognitive accessibility and can be found a neural realizer of this overflow.
Abstract: How can we disentangle the neural basis of phenomenal consciousness from the neural machinery of the cognitive access that underlies reports of phenomenal consciousness? We see the problem in stark form if we ask how we can tell whether representations inside a Fodorian module are phenomenally conscious. The methodology would seem straightforward: Find the neural natural kinds that are the basis of phenomenal consciousness in clear cases - when subjects are completely confident and we have no reason to doubt their authority - and look to see whether those neural natural kinds exist within Fodorian modules. But a puzzle arises: Do we include the machinery underlying reportability within the neural natural kinds of the clear cases? If the answer is "Yes," then there can be no phenomenally conscious representations in Fodorian modules. But how can we know if the answer is "Yes"? The suggested methodology requires an answer to the question it was supposed to answer! This target article argues for an abstract solution to the problem and exhibits a source of empirical data that is relevant, data that show that in a certain sense phenomenal consciousness overflows cognitive accessibility. I argue that we can find a neural realizer of this overflow if we assume that the neural basis of phenomenal consciousness does not include the neural basis of cognitive accessibility and that this assumption is justified (other things being equal) by the explanations it allows.
715 citations
TL;DR: This work predicts spatially distinct "persistent modes" of dementia that recapitulate known patterns of dementia and match recent reports of selectively vulnerable dissociated brain networks, and closely match T1-weighted MRI volumetrics of 18 Alzheimer's and frontotemporal dementia subjects.
610 citations
Cites background from "When the Brain Loses Its Self: Pref..."
...Degeneration of the orbitofrontal cortex was linked to disinhibited behavior, and the superior frontal gyrus has been associated with self-awareness (Goldberg et al., 2006)....
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References
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Book•
01 Jan 1890
TL;DR: For instance, the authors discusses the multiplicity of the consciousness of self in the form of the stream of thought and the perception of space in the human brain, which is the basis for our work.
Abstract: Arguably the greatest single work in the history of psychology. James's analyses of habit, the nature of emotion, the phenomenology of attention, the stream of thought, the perception of space, and the multiplicity of the consciousness of self are still widely cited and incorporated into contemporary theoretical accounts of these phenomena.
14,049 citations
TL;DR: A baseline state of the normal adult human brain in terms of the brain oxygen extraction fraction or OEF is identified, suggesting the existence of an organized, baseline default mode of brain function that is suspended during specific goal-directed behaviors.
Abstract: A baseline or control state is fundamental to the understanding of most complex systems. Defining a baseline state in the human brain, arguably our most complex system, poses a particular challenge. Many suspect that left unconstrained, its activity will vary unpredictably. Despite this prediction we identify a baseline state of the normal adult human brain in terms of the brain oxygen extraction fraction or OEF. The OEF is defined as the ratio of oxygen used by the brain to oxygen delivered by flowing blood and is remarkably uniform in the awake but resting state (e.g., lying quietly with eyes closed). Local deviations in the OEF represent the physiological basis of signals of changes in neuronal activity obtained with functional MRI during a wide variety of human behaviors. We used quantitative metabolic and circulatory measurements from positron-emission tomography to obtain the OEF regionally throughout the brain. Areas of activation were conspicuous by their absence. All significant deviations from the mean hemisphere OEF were increases, signifying deactivations, and resided almost exclusively in the visual system. Defining the baseline state of an area in this manner attaches meaning to a group of areas that consistently exhibit decreases from this baseline, during a wide variety of goal-directed behaviors monitored with positron-emission tomography and functional MRI. These decreases suggest the existence of an organized, baseline default mode of brain function that is suspended during specific goal-directed behaviors.
10,708 citations
"When the Brain Loses Its Self: Pref..." refers background or result in this paper
...These regions likely correspond to the previously termed ‘‘default’’ brain network (Raichle et al., 2001)....
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...…lateral occipital complex (LOC; Malach et al., 2002), and major specializations such as faceselective cortex in the fusiform gyrus are all examples of robust and consistent activation patterns produced by sensory stimulation (for reviews, see Grill-Spector and Malach, 2004; Tootell et al., 1996)....
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...We indeed found consistent and Activity maps for introspection versus slow categorization tasks during the visual scan shown in a folded view of both hemispheres in their anatomical relations (center-top panel), inflated (middle), and unfolded (bottom) formats....
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...The inhibition of cortical area by sensory stimulation is also reminiscent to that found in the ‘‘default mode’’ brain network of areas (Raichle et al., 2001), which undergo inactivation during a wide variety of goal-directed cognitive tasks and involve also regions in the precuneus and inferior…...
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...Interestingly, these areas show substantial overlap with the ‘‘default mode’’ network of areas (Raichle et al., 2001), which are intriguingly related to high-level mental functions such as ‘‘theory of mind’’ and social cognition (Vogeley and Fink, 2003; Iacoboni et al., 2004)....
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Book•
01 Jan 1994
TL;DR: The authors argued that rational decisions are not the product of logic alone - they require the support of emotion and feeling, drawing on his experience with neurological patients affected with brain damage, Dr Damasio showed how absence of emotions and feelings can break down rationality.
Abstract: Descartes' Error offers the scientific basis for ending the division between mind and body. Antonio Damasio contends that rational decisions are not the product of logic alone - they require the support of emotion and feeling. Drawing on his experience with neurological patients affected with brain damage, Dr Damasio shows how absence of emotions and feelings can break down rationality. He also offers a new perspective on what emotions and feelings actually are: a direct view of our own body states; a link between the body and its survival-oriented regulation on the one hand, and consciousness on the other. Written as a conversation between the author and an imaginary listener, Descartes' Error leads us to conclude that human organisms are endowed from their very beginning with a spirited passion for making choices, which the social mind can then use to build rational behaviour.
9,648 citations
9,362 citations
"When the Brain Loses Its Self: Pref..." refers background or methods in this paper
...The cortical surface in a Talairach coordinate system (Talairach and Tournoux, 1988) was reconstructed for each subject from the 3D-spoiled gradient echo scan....
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...Before discussing the possible implications of this finding, we discuss the possible reservations....
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