Common Blood Flow Changes across Visual Tasks: II. Decreases in Cerebral Cortex

Shulman, Gordon L.; Fiez, Julie A.; Corbetta, Maurizio; Buckner, Randy L.; Miezin, Francis M.; Raichle, Marcus E.; Petersen, Steven E.

doi:10.1162/jocn.1997.9.5.648

Cited by 1,756 publications

(1,644 citation statements)

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“…They are activated more by words than nonwords during lexical decision Binder et al, in press;Ischebeck et al, 2004) and more by concrete words than abstract words (Binder et al, in press). This network has also been repeatedly shown to ddeactivateT during active tasks relative to resting or passive stimulation conditions (Binder et al, 1999;Mazoyer et al, 2001;McKiernan et al, 2003;Raichle et al, 2001;Shulman et al, 1997). This latter effect was also clear in our contrasts between the naming conditions and passive fixation (Fig.…”

Section: Discussionsupporting

confidence: 78%

Some neurophysiological constraints on models of word naming

et al. 2005

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The pronunciation of irregular words in deep orthographies like English cannot be specified by simple rules. On the other hand, the fact that novel letter strings can be pronounced seems to imply the existence of such rules. These facts motivate dual-route models of word naming, which postulate separate lexical (whole-word) and non-lexical (rulebased) mechanisms for accessing phonology. We used fMRI during oral naming of irregular words, regular words, and nonwords, to test this theory against a competing single-mechanism account known as the triangle model, which proposes that all words are handled by a single system containing distributed orthographic, phonological, and semantic codes rather than word codes. Two versions of the dual-route model were distinguished: an dexclusiveT version in which activation of one processing route predominates over the other, and a dparallelT version in which both routes are equally activated by all words. The fMRI results provide no support for the exclusive dual-route model. Several frontal, insular, anterior cingulate, and parietal regions showed responses that increased with naming difficulty (nonword > irregular word > regular word) and were correlated with response time, but there was no activation consistent with the predicted response of a nonlexical, rule-based mechanism (i.e., nonword > regular word > irregular word). Several regions, including the angular gyrus and dorsal prefrontal cortex bilaterally, left ventromedial temporal lobe, and posterior cingulate gyrus, were activated more by words than nonwords, but these dlexical routeT regions were equally active for irregular and regular words. The results are compatible with both the parallel dual-route model and the triangle model. dLexical routeT regions also showed effects of word imageability. Together with previous imaging studies using semantic task contrasts, the imageability effects are consistent with semantic processing in these brain regions, suggesting that word naming is partly semantically-mediated. D 2005 Elsevier Inc. All rights reserved. Keywords: Word naming; Dual-route model; Triangle model IntroductionThe correspondence between spoken and written forms of a language is not always systematic. While in some alphabetic orthographies the sound of a word can be worked out using rules of pronunciation, in most, there are varying degrees of irregularity in the mapping between print and sound. In English, for example, Bernard Shaw pointed out that the word ''fish'' could be written ghoti if one were mischievous enough to borrow the spelling for /f/ from rough, the spelling of /I/ from women, and the spelling of /sh/ from nation. Words like colonel and yacht are only some of the more extreme examples of such irregularity of pronunciation, which is pervasive in English and is seen in many of its more common words, including some, many, of, the, and word just used in this sentence.While the pronunciation of these dirregularT words would seem to be learned through rote memorization of the whole word, there is...

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Section: Discussionsupporting

confidence: 78%

Some neurophysiological constraints on models of word naming

et al. 2005

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“…45 Contemporary networks consisted of regions identified from resting-state fMRI experimental results. 42,[46][47][48][49][50][51][52] Sizes of classic networks varied from B11% (medial limbic area) to 35% (frontal lobe) of gray-matter space, whereas sizes of contemporary networks varied substantially, for example, a frontal network Table 2). The dashed blue line represents the best-fit linear regression of all human data (i.e., CMR glc ¼ 0.003 BIS þ 0.06, R 2 ¼ 0.984), which is insignificantly different if the two vegetative state data points are removed (i.e., CMR glc ¼ 0.003 BIS þ 0.04, R 2 ¼ 0.986).…”

Section: Regional Oxidative Demand For Glutamatergic Activity In the mentioning

confidence: 99%

Glutamatergic Function in the Resting Awake Human Brain is Supported by Uniformly High Oxidative Energy

Hyder

Fulbright

Shulman

et al. 2013

J Cereb Blood Flow Metab

107

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Rodent 13 C magnetic resonance spectroscopy studies show that glutamatergic signaling requires high oxidative energy in the awake resting state and allowed calibration of functional magnetic resonance imaging (fMRI) signal in terms of energy relative to the resting energy. Here, we derived energy used for glutamatergic signaling in the awake resting human. We analyzed human data of electroencephalography (EEG), positron emission tomography (PET) maps of oxygen (CMR O2 ) and glucose (CMR glc ) utilization, and calibrated fMRI from a variety of experimental conditions. CMR glc and EEG in the visual cortex were tightly coupled over several conditions, showing that the oxidative demand for signaling was four times greater than the demand for nonsignaling events in the awake state. Variations of CMR O2 and CMR glc from gray-matter regions and networks were within ±10% of means, suggesting that most areas required similar energy for ubiquitously high resting activity. Human calibrated fMRI results suggest that changes of fMRI signal in cognitive studies contribute at most ± 10% CMR O2 changes from rest. The PET data of sleep, vegetative state, and anesthesia show metabolic reductions from rest, uniformly 420% across, indicating no region is selectively reduced when consciousness is lost. Future clinical investigations will benefit from using quantitative metabolic measures. Keywords: astrocytes; baseline; field potentials; glutamate; multiunit activity; resting state INTRODUCTIONThe human brain consumes 20% of the body's energy at rest despite being only 2% of total body mass. 1 Normally glucose oxidation is the source of energy production supporting brain function 2 in which gray-matter signaling (i.e., events associated with neuronal firing) is dominated by glutamatergic neurons. 3 Estimates of the fraction of resting brain energy devoted to signaling were originally quite low. 4 But recent experimental studies in rodents and theoretical modeling have converged on the conclusion that majority of the resting energy consumption supports glutamatergic signaling and the energy demand changes linearly with pyramidal neuron firing rates and glutamate neurotransmitter release and reuptake. [5][6][7][8][9] Therefore in rodent models it is possible, to a first order, to show that the resting energy is primarily dedicated to total glutamatergic signaling, and the changes in neuronal signaling relative to a well-defined resting activity level can be used to calibrate changes in energy consumption during functional magnetic resonance imaging (fMRI) experiments. 10,11 In the awake human brain, however, the fraction of resting energy usage devoted to glutamatergic signaling is less well understood. The magnitude of neuronal signaling in the human brain, and by inference the commensurate energy demand, underscores the functional relevance of resting activity and has profound implications for interpreting fMRI experiments in humans. [12][13][14] Given the rapidly increasing use of resting-state fMRI in mapping networks-defined as a...

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“…However, besides the low LFPR, the component's location adjacent to the anterior insula, a region prone to respiration‐related artifacts (Shulman et al. 1997; Fox et al. 2005) may also suggest artifact contamination.…”

Section: Discussionmentioning

confidence: 99%

Dynamic interactions of the cortical networks during thought suppression

et al. 2016

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ObjectivesThought suppression has spurred extensive research in clinical and preclinical fields, particularly with regard to the paradoxical aspects of this behavior. However, the involvement of the brain's inhibitory system in the dynamics underlying the continuous effort to suppress thoughts has yet to be clarified. This study aims to provide a unified perspective for the volitional suppression of internal events incorporating the current understanding of the brain's inhibitory system.Materials and MethodsTwenty healthy volunteers underwent functional magnetic resonance imaging while they performed thought suppression blocks alternating with visual imagery blocks. The whole dataset was decomposed by group‐independent component analysis into 30 components. After discarding noise components, the 20 valid components were subjected to further analysis of their temporal properties including task‐relatedness and between‐component residual correlation.ResultsCombining a long task period and a data‐driven approach, we observed a right‐side‐dominant, lateral frontoparietal network to be strongly suppression related. This network exhibited increased fluctuation during suppression, which is compatible with the well‐known difficulty of suppression maintenance.ConclusionsBetween‐network correlation provided further insight into the coordinated engagement of the executive control and dorsal attention networks, as well as the reciprocal activation of imagery‐related components, thus revealing neural substrates associated with the rivalry between intrusive thoughts and the suppression process.

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Common Blood Flow Changes across Visual Tasks: II. Decreases in Cerebral Cortex

Cited by 1,756 publications

References 13 publications

Some neurophysiological constraints on models of word naming

Some neurophysiological constraints on models of word naming

Glutamatergic Function in the Resting Awake Human Brain is Supported by Uniformly High Oxidative Energy

Dynamic interactions of the cortical networks during thought suppression

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