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At least 217 records · Page 12Linked to original sources
PubMed1991

High-resolution optical imaging of functional brain architecture in the awake monkey.

Optical imaging of the functional architecture of cortex, based on intrinsic signals, is a useful tool for the study of the development, organization, and function of the living mammalian brain. This relatively noninvasive technique is based on small activity-dependent changes of the optical properties of cortex. Thus far, functional imaging has been performed only on anesthetized animals. Here we establish that this technique is also suitable for exploring the brain of awake behaving primates. We designed a chronic sealed chamber and mounted it on the skull of a cynomolgus monkey (Macaca fascicularis) over the primary visual cortex to permit imaging through a transparent glass window. Restriction of head position alone was sufficient to eliminate movement noise in awake monkey imaging experiments. High-resolution imaging of the ocular dominance columns and the cytochrome oxidase blobs was achieved simply by taking pictures of the exposed cortex when the awake monkey was viewing video movies alternatively with each eye. Furthermore, the functional maps could be obtained without synchronization of the data acquisition to the animal's respiration and the electrocardiogram. The wavelength dependency and time course of the intrinsic signal were similar in anesthetized and awake monkeys, indicating that the signal sources were the same. We therefore conclude that optical imaging is well suited for exploring functional organization related to higher cognitive brain functions of the primate as well as providing a diagnostic tool for delineating functional cortical borders and assessing proper functions of human patients during neurosurgery.

Animals↗
PubMed1990

Effects of high dietary sulfur on brain functions using evoked potentials technique.

Brain stem auditory-evoked response (BAER) is a noninvasive technique used for detecting neurophysiological abnormalities of the brain stem along the auditory pathway. Brain stem auditory-evoked response recordings were obtained from subcutaneous skin electrodes from two control sheep and 22 other sheep fed high sulfur (S) diets with low or high concentration of thiamine (B1), copper (Cu), and molybdenum (Mo). At least four peaks (I,II,III,IV) of varied amplitude were observed in all animals. Neurophysiological abnormalities due to decreased conductivity and/or excitability of nerve fibers along the auditory pathway were found on the BAER recordings of sheep fed high S diet. Abnormalities of peaks and interpeak latencies within BAER recordings were related to histopathological observations of brain stem lesions. Lesions in the areas of the cochlear nuclei and lateral lemniscus were seen in conjunction with altered BAER components. However, abnormalities in BAER recordings and lesions in the brain stem also occurred in the absence of overt clinical signs. Analysis of interpeak latencies between peaks I and IV revealed significant differences among dietary groups. Sheep given diets low in Cu, Mo, and B1 were affected most. Factorial analysis indicated B1 and interactions among Cu, Mo, and B1 as significant factors influencing interpeak latencies.

Animals↗
PubMed1995

Lack of preservation of higher brain function during hypoglycaemia in patients with intensively-treated IDDM.

Severe hypoglycaemia with cognitive dysfunction is 3 times more common in intensively, rather than conventionally, treated insulin-dependent diabetes mellitus (IDDM). To investigate the effect of diabetes control on higher brain function during acute hypoglycaemia, we studied one of the earliest detectable changes in cognitive function, i.e. the four-choice reaction time, and symptomatic and hormonal responses during euglycaemic and hypoglycaemic clamping in human subjects. There were no changes in symptoms or counterregulatory hormones and four-choice reaction time was stable during 220 min of euglycaemic insulin clamping in five men with IDDM, with a coefficient of variation of less than 2.2% (1% for accuracy) for the cognitive function test. During stepped hypoglycaemic clamping however, hormonal responses and subjective awareness of hypoglycaemia occurred in all groups but started at much lower blood glucose concentrations in eight intensively-treated diabetic subjects (Group 1) than in ten conventionally-treated (Group 2) or in eight non-diabetic subjects (Group 3). For example, for adrenaline, plasma glucose thresholds were 2.7 +/- 0.2 vs 3.4 +/- 0.2 and 3.2 +/- 0.1 mmol/l, respectively, p < 0.05, Group 1 vs Groups 2 or 3 and for subjective awareness of hypoglycaemia 2.3 +/- 0.2 vs 3.0 +/- 0.1 and 3.2 +/- 0.1 mmol/l, p < or = 0.003), as in previous studies. In contrast, deterioration in reaction time occurred at 3.2 +/- 0.3, 3.2 +/- 0.2 and 3.0 +/- 0.2 mmol/l, respectively (p = NS), thus occurring at higher glucose levels than subjective awareness in the intensively-treated subjects only. The altered hierarchy of responses to hypoglycaemia in well-controlled intensively-treated diabetes explains the increased risk of severe hypoglycaemia without warning seen in such patients.

Adult↗
PubMed1968

Anaerobic brain function: effects of stagnant and anoxic anoxia on persistence of breathing in reptiles.

Turtles tolerate anoxic anoxia about 14 times longer than stagnant anoxia. In snakes and crocodiles this difference is much less marked. Apparently, the remarkable anaerobic viability of turtles is dependent on blood circulation, Analyses of plasma indicate that loss of brain function in anoxic crocodiles is not caused by systemic acidosis or hypoglycemia. It is suggested that the ability of the central nervous system of the turtle to function without oxygen is due to a comparatively high rate of anaerobic uptake or metabolism of glucose.

Animals↗
PubMed1978

Selective attention, cortical evoked responses, and brain function in human subjects: a critical review and theory.

A theoretical framework is proposed to account for the facts of selective attention in terms of cortical redundancy and cortical-subcortical interactions as measured by the Average Evoked Response and the background EEG. The recent research concerning AER correlations of selective attention is reviewed and found to be lacking in methodological coherence. This lack is found to contaminate existing theory regarding selective attention and brain function. An alternative approach is explored and its findings are found to yield the present theory.

Arousal↗
PubMed1994

The effects of sex steroids, and the X chromosome, on female brain function: a study of the neuropsychology of adult Turner syndrome.

Sex steroids and the X chromosome can independently affect cognitive abilities. Because subjects with Turner syndrome (TS) have gonadal aplasia, and various alterations in X chromosome structure and number, they provide a model to study the effects of sex steroids and of the X chromosome on human brain function. We used neuropsychological tests to study the cognitive abilities of 18 TS adults and 19 age/sex matched healthy controls. Nine TS subjects were mosaic for the 45,X karyotype, and 9 were non-mosaic 45,X (full TS). The TS group as a whole, compared to controls, had (i) significantly lower scores in tests of language and visual-spatial function, attention and memory, and (ii) a significantly greater discrepancy between verbal and performance scores. Mosaic TS subjects were intermediate between full TS and controls in some tests of verbal ability, but did not differ significantly from controls in others. Visuospatial ability was significantly lower than controls in both mosaic and full TS. Within the mosaic TS group, there was a significant negative correlation between visuospatial ability and % lymphocytes having a 45,X karyotype. Memory test scores were reduced independently of "X chromosome dosage" in all TS subjects. We conclude that in humans, the X chromosome is involved in development of both cerebral hemispheres, but moreso of the association neocortices. Also, sex steroids may modulate this effect--particularly in hippocampus.

Adolescent↗
PubMed1992

Intrinsic signal changes accompanying sensory stimulation: functional brain mapping with magnetic resonance imaging.

We report that visual stimulation produces an easily detectable (5-20%) transient increase in the intensity of water proton magnetic resonance signals in human primary visual cortex in gradient echo images at 4-T magnetic-field strength. The observed changes predominantly occur in areas containing gray matter and can be used to produce high-spatial-resolution functional brain maps in humans. Reducing the image-acquisition echo time from 40 msec to 8 msec reduces the amplitude of the fractional signal change, suggesting that it is produced by a change in apparent transverse relaxation time T*2. The amplitude, sign, and echo-time dependence of these intrinsic signal changes are consistent with the idea that neural activation increases regional cerebral blood flow and concomitantly increases venous-blood oxygenation.

Brain Chemistry↗
PubMed1990

Hypnosis and lateralized brain functions.

Bilateral EEG measures were obtained on 16 high hypnotizable Ss (scores of greater than 8 on the Harvard Group Scale of Hypnotic Susceptibility, Form A, Shor & E. Orne, 1962), while performing hemisphere-specific tasks during hypnosis and a no-hypnosis control condition. Conditions and tasks were presented in counterbalanced order, and Ss served as their own controls. The data call into question the right hemisphere activation interpretation of lateralized brain function during hypnosis; rather, the data suggest a lack of task appropriate activity during hypnosis. The failure to attend to baseline activity measurements and the use of ratios to evaluate interhemispheric lateralization may contribute to potential misinterpretations of data. It is critical that activity changes of the separate hemispheres be taken into account in the interpretative process.

Cerebral Cortex↗
PubMed1994

MRI changes and deficits of higher brain functions in preterm diplegia.

Forty-one preterm children (29 with spastic diplegia and 12 without motor deficits) who had a normal verbal IQ were studied to clarify the clinical significance of neuroanatomical abnormalities disclosed by T1-weighted and T2-weighted magnetic resonance imaging (MRI). Both types of images clearly showed abnormalities in the frontal corona radiata of the children with spastic diplegia, while there were no abnormalities in the children without motor deficits. We compared the T1-weighted imaging findings with deficits of higher brain functions, evaluated by the performance subtests of the Wechsler Intelligence Scale. Thinning of the parietal and/or occipital white matter was noted in children with visuospatial cognitive deficits. Thus, MRI may be helpful in confirming early clinical suspicions of visuospatial cognitive deficits as well as motor deficits in preterm children, especially those with spastic diplegia.

Brain↗
PubMed1996

Malnutrition and brain function: experimental studies using the phenomenon of cortical spreading depression.

Depending on its intensity and duration, nutritional deficiency can disrupt the structure and function of the nervous system of humans and other mammals, with consequences more or less devastating for the whole organism, particularly in the early postnatal life, when body growth is very rapid and the need for proteins, calories and other nutrients is greatest. In this review, electrophysiological data are presented regarding the use of the phenomenon of cortical spreading depression (CSD) to study effects of malnutrition on the brain. Several conditions of clinical importance and that are known to alter brain function are shown also to influence CSD features in experimental animals. Some of these conditions, (e.g., pharmacological manipulation of neurotransmitter systems, dietary treatment with Lithium, acute hyperglycemia, hypothyroidism, aging and environmental stimulation) decrease CSD susceptibility, while other conditions increase it, as, for example, systemic reduction of extracellular chloride levels, deprivation of REM-sleep, acute hypoglycemia, treatment with diazepam, consumption of ethanol and malnutrition. Particular emphasis is laid on the effect of early environmental enrichment on CSD in normal and malnourished animals. Our results suggest that such effect is more evident in the malnourished brain, as compared to the well-nourished one. The data also show that malnutrition alters the brain responsivity to some CSD-facilitatory or inhibitory agents. The underlying mechanisms to explain the observed effects are discussed.

Animals↗
PubMed1994

Patterns of recovery and change in verbal and nonverbal functions in a case of crossed aphasia: implications for models of functional brain lateralization and localization.

We present a 2-year verbal and nonverbal follow-up of a crossed aphasic patient. The patient had suffered from widespread ischemic damage in the area of right middle cerebral artery, with a parieto-temporal lesion. Three months postonset he showed classical Wernicke's aphasia associated with oral, limb and constructional apraxia and left hemineglect. However, follow-up findings showed a complex, dynamic pattern entirely consistent with cognitive models of language and nonlanguage abilities. Current models of functional brain lateralizations could not satisfactorily account for such longitudinal, fine-grain observations.

Agraphia↗