The Effect of Mental Arithmetic on Cerebral Circulation and Metabolism 1

Sokoloff, Louis; Mangold, R.; Wechsler, Richard L.; Kennedy, Charles; Kety, Seymour S.

doi:10.1172/jci103159

Cited by 206 publications

(84 citation statements)

References 9 publications

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“…Thus, changes in absolute blood flow in areas typically affected by cognitive tasks are rarely Ͼ5-10% of the brain's resting blood flow. These modest modulations in ongoing circulatory activity often do not appreciably affect overall brain blood flows during even vigorous sensory and motor activity (45)(46)(47). For interesting exceptions related to more demanding cognitive tasks see refs.…”

Section: Discussionmentioning

confidence: 99%

Default brain functionality in blind people

Burton¹,

Snyder²,

Raichle³

2004

Proc. Natl. Acad. Sci. U.S.A.

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We studied whether default functionality of the human brain, as revealed by task-independent decreases in activity occurring during goal-directed behaviors, is functionally reorganized by blindness. Three groups of otherwise normal adults were studied: early blind, adventitiously blind, and normally sighted. They were imaged by using functional MRI during performance of a word association task (verb generation to nouns) administered by using auditory stimuli in all groups and Braille reading in blind participants. In sighted people, this task normally produces robust taskindependent decreases relative to a baseline of quiet wakefulness with eyes closed. Our functional MRI results indicate that taskindependent decreases are qualitatively similar across all participant groups in medial and dorsal prefrontal, lateral parietal, anterior precuneus, and posterior cingulate cortices. Similarities in task-independent decreases are consistent with the hypothesis that functional reorganization resulting from the absence of a particular sensory modality does not qualitatively affect default functionality as revealed by task-independent decreases. More generally, these results support the notion that the brain largely operates intrinsically, with sensory information modulating rather than determining system operations.M uch previous functional brain imaging work in normally sighted (NS) adult humans has documented activity decreases during performance of various goal-directed behaviors relative to a control state, such as quiet wakefulness with eyes closed, visual fixation, or a minimally demanding task (1-3). These activity decreases have a variable relationship to taskspecific activity increases. Some decreases appear to represent activity attenuation in sensory systems irrelevant to the task; these task-dependent decreases can occur in sensory cortex both within and separate from the modality engaged by the task (4-7).Other activity decreases appear to be independent of the performed task. With remarkable regularity, these taskindependent decreases occur in medial and lateral parietal cortices, posterior cingulate cortex, dorsal and ventral medial prefrontal cortex, and the amygdalae (reviewed in ref. 8). We propose that task-independent decreases represent suppression of default brain functionality (9) and have cited detailed circulatory and metabolic evidence showing that such decreases do not correspond to ''activations'' in the resting state, as has been suggested (3). Rather, task-independent decreases occur in areas that are functionally active but not physiologically ''activated.'' Default brain activity suggests spontaneous functions that are attenuated only when we reallocate resources to temporarily engage in goal-directed behaviors. Hence our designation of ''default'' functions (8, 9).Numerous studies show that blindness leads to cortical reorganization manifesting as increased visual cortex activity during performance of tasks involving tactile and auditory stimuli (reviewed in refs. 10 and 11). Of interest ...

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Section: Discussionmentioning

confidence: 99%

Default brain functionality in blind people

Burton¹,

Snyder²,

Raichle³

2004

Proc. Natl. Acad. Sci. U.S.A.

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“…Moving from the observation that cerebral metabolism during a quiet rest state is as vigorous as that when individuals solve externally administered matching problems [25], brain imaging research in recent years has completely changed the traditional view that FDG PET brain images at rest poorly reflect a homogeneous distribution of low levels of glucose consumption in cortical and subcortical regions. In this respect, novel insights have indicated the presence of multiple interacting systems called the "default network" which is preferentially active at rest when individuals are engaged in internally focused tasks including autobiographical memory retrieval, visualizing the future, and conceiving the perspectives of others [26].…”

Section: Baruch Spinozamentioning

confidence: 99%

The new FDG brain revolution: the neurovascular unit and the default network

Sestini¹,

Castagnoli²,

Mansi³

2009

Eur J Nucl Med Mol Imaging

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"Our aim is, more than see new things, to see with new eyes what has already been seen" Baruch SpinozaThe first FDG brain revolutionThe first revolution was explosive. Using 18 F-fluorodeoxyglucose (FDG), it was possible to see and study the living brain in humans! Pioneers were top experts who provided different specialized expertise, but strictly cooperating between themselves [1]. Physicists, engineers and mathematicians were actively involved in producing the best hardware and software. The research on crystals, in identifying the most effective electronics, in defining accurate methods for attenuation and scatter correction and so on, was nevertheless limited by the relatively poor technology, with the main consideration being limited computer power. These developments stimulated a major interest in the brain. Satisfactory sensitivity and resolution, together with reliable solutions to the technical problems, were only achieved with dedicated cerebral PET scanners which had a field of view that permitted exclusive analysis of the brain.Basic scientists had the possibility of realizing a scientific dream: the transfer of data on cerebral glucose metabolism acquired in animals by quantitative autoradiography to humans. Another issue in the original FDG PET research was to consider mandatory absolute quantification. Thus arterial (or arterialized) sampling, to obtain data to be included in mathematical models, was routinely performed. However, because the equations included nonmeasurable parameters, the presence of a lumped constant affected absolute measurement in an individual [2][3][4]. PET teams included (and were directed by) clinical experts including not only nuclear physicians, but also other professionals such as neuroradiologists, neurologists and psychiatrists, who frequently cooperated with psychologists, anatomists and physiologists.Because of the unsatisfactory spatial resolution and the negative influence of the partial volume effect, in presence of glucose uptake in the normal brain, only a low lesion/background ratio was achievable, except for hot spots, i.e. the presence of focal areas of increased uptake determined by physiological and/or pathological causes. Therefore, the use of FDG as a positive indicator was restricted in the first studies and in the search for hot spots, many studies involved physiological stimulation tests (closed/open eyes, auditory system, etc.) in normal subjects [5,6]. Similarly, major interest in pathological analysis was directed to the evaluation of brain tumours, starting from Warburg's hypothesis of higher FDG uptake in malignant lesions with respect to benign ones [7]. With further clinical experience, in the analysis of patients with epilepsy, a higher sensitivity was clearly demonstrated during the ictal phase, the focus being seen as a hot spot, with respect to the interictal period when the lesion was not easily detectable, being an area with a slightly reduced overall FDG uptake [8,9]. Discrepant results in epilepsy clearly demonstrate how, in the absenc...

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“…These changes are very small relative to the ongoing hemodynamic and metabolic activity of the brain. Attempts to measure whole brain changes in blood flow and metabolism during intense mental activity have failed to demonstrate any change (2). This finding is not entirely surprising considering both the accuracy of the methods and the small size of the observed changes.…”

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confidence: 94%

“…Remarkably, despite its relatively small size, the brain accounts for about 20% of the oxygen and, hence, calories consumed by the body (1). This high rate of metabolism is remarkably constant despite widely varying mental and motoric activity (2).…”

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confidence: 99%