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At least 1,171 records · Page 65Linked to original sources
PubMed2001

Nasal bilevel positive airway pressure therapy in children with a sleep-related breathing disorder and attention-deficit hyperactivity disorder: effects on electrophysiological measures of brain function.

OBJECTIVE: To examine the effect of nasal bilevel positive airway pressure (BiPAP) treatment for concurrent sleep-related breathing disorders (SRBDs) and attention-deficit hyperactivity disorder (ADHD) on electrophysiological measures of spontaneous brain activity and auditory stimulus processing. METHODS: Nineteen children diagnosed with both SRBD and ADHD participated. Electroencephalogram (EEG) activity was recorded during a resting period and an auditory oddball task before beginning BiPAP treatment, after 6 months on treatment, and after a subsequent 1 week non-treatment period. Treatment effects on EEG and event-related potentials (ERPs) to target stimuli were examined via topographic analysis. RESULTS: Thirteen of the initial 19 children completed 6 months of BiPAP therapy, with six lost mainly due to compliance problems. Children on BiPAP therapy showed a significant decrease in slow-wave (delta and theta) and an increase in fast wave (beta) EEG activity. The P3 component of the ERP showed treatment effects in amplitude and latency. CONCLUSIONS: The electrophysiological data suggest that SRBDs may contribute to ADHD symptomatology. Treatment of SRBD with BiPAP therapy in children with concurrent ADHD can lead to significant changes, in the direction of normalization, of the typical electrophysiological features of ADHD.

Journal Article↗
PubMedDate not supplied

Visual memory, visual imagery, and visual recognition of large field patterns by the human brain: functional anatomy by positron emission tomography.

We measured the regional cerebral blood flow (rCBF) in 11 healthy volunteers with PET (positron emission tomography). The main purpose was to map the areas of the human brain that changed rCBF during (1) the storage, (2) retrieval from long-term memory, and (3) recognition of complex visual geometrical patterns. A control measurement was done with subjects at rest. Perception and learning of the patterns increased rCBF in V1 and 17 cortical fields located in the cuneus, the lingual, fusiform, inferior temporal, occipital, and angular gyri, the precuneus, and the posterior part of superior parietal lobules. In addition, rCBF increased in the anterior hippocampus, anterior cingulate gyrus, and in several fields in the prefrontal cortex. Recognition of the patterns increased rCBF in 18 identically located fields overlapping those activated in learning. In addition, recognition provoked differentially localized increases in the pulvinar, posterior hippocampus, and prefrontal cortex. Learning and recognition of the patterns thus activated identical visual regions, but different extravisual regions. A surprising finding was that the hippocampus was also active in recognition. Recall of the patterns from long-term memory was associated with rCBF increases in yet different fields in the prefrontal cortex, and the anterior cingulate cortex. In addition, the posterior inferior temporal lobe, the precuneus, the angular gyrus, and the posterior superior parietal lobule were activated, but not any spot within the occipital cortex. Activation of V1 or immediate visual association areas is not a prerequisite for visual imagery for the patterns. The only four fields activated in storage recall and recognition were those in the posterior inferior temporal lobe, the precuneus, the angular gyrus, and the posterior superior parietal lobule. These might be the storage sites for such visual patterns. If this is true, storage, retrieval, and recognition of complex visual patterns are mediated by higher-level visual areas. Thus, visual learning and recognition of the same patterns make use of identical visual areas, whereas retrieval of this material from the storage sites activates only a subset of the visual areas. The extravisual networks mediating storage, retrieval, and recognition differ, indicating that the ways by which the brain accesses the storage sites are different.

Adult↗
PubMed1999

Computational modeling of high-level cognition and brain function.

This article describes a computational modeling architecture, 4CAPS, which is consistent with key properties of cortical function and makes good contact with functional neuroimaging results. Like earlier cognitive models such as SOAR, ACT-R, 3CAPS, and EPIC, the proposed cognitive model is implemented in a computer simulation that predicts observable variables such as human response times and error patterns. In addition, the proposed 4CAPS model accounts for the functional decomposition of the cognitive system and predicts fMRI activation levels and their localization within specific cortical regions, by incorporating key properties of cortical function into the design of the modeling system.

Brain↗
PubMed2000

The effects of surgical treatment of Parkinson's disease on brain function: PET findings.

Positron emission tomography allows a quantitative assessment of the impact of functional neurosurgery in Parkinson's disease (PD) by measuring regional cerebral flow and glucose and oxygen consumption as indicators of metabolic activity of specific brain regions. PET can also be used to study the dopaminergic nigrostriatal system, and therefore serves as a surrogate marker of the evolution of striatal grafts for PD. Pallidotomy has been associated with increased activation of premotor areas (supplementary motor area and dorsolateral prefrontal cortex) and reduced hyperactivity of the lentiform nucleus (augmented preoperatively). Pallidal (GPi) and subthalamic (STN) stimulation also increase activation of premotor areas but decrease activation of primary motor area. Suppression of unilateral tremor with thalamic stimulation is associated with a reduction in cerebellar blood flow. These main findings are in keeping with the general notion that increased activity in the STN GPi projection is directly implicated in the pathophysiology of PD. Surgical blockage of these output nuclei leads to partial restoration of cortical physiology.

Adult↗
PubMedDate not supplied

[The role of the electromechanical and reaction-diffusion system of intraneuronal information processing in brain function].

The experimental data of previous papers are considered as a basis for the hypothesis about intraneuronal system controlled by cyclic nucleotides and changing the membrane permeability upon creating the generatory potential. This system is suggested to be an extremal molecular regulator in which the price of action per single operation approximates the physical limit. The electro-mechanical intraneuronal system is capable of solving multidimensional physical problems by means of molecular "digital" hypersound holo-gram coded by DNA molecular text which is an image of functions of target search.

Animals↗
PubMed2003

Very slow activity fluctuations in monkey visual cortex: implications for functional brain imaging.

We examined fluctuations in band-limited power (BLP) of local field potential (LFP) signals recorded from multiple electrodes in visual cortex of the monkey during different behavioral states. We asked whether such signals demonstrated coherent fluctuations over time-scales of seconds and minutes, and would thus serve as good candidates for direct comparison with data obtained from functional magnetic resonance imaging (fMRI). We obtained the following results. (i) The BLP of the local field displayed fluctuations at many time-scales, with particularly large amplitude at very low frequencies (<0.1 Hz). (ii) These fluctuations exhibited high coherence between electrode pairs, particularly for BLP signals derived from the gamma frequency range. (iii) Coherence in the BLP, unlike that in the raw LFP, did not fall off sharply as a function of cortical distance. (iv) The structure and coherence of BLP changes were highly similar under distinctly different behavioral states. These results demonstrate the existence of widespread coherent activity fluctuations in the brain of the awake monkey over very long time-scales. We propose that such signals may make a significant contribution to the high variability observed in the time course of physiological signals, including those measured with functional imaging techniques. The results are discussed in the context of combined fMRI/electrophysiological recordings.

Animals↗
PubMedDate not supplied

Neuromagnetism: a new approach for localizing brain function.

The physical origins of neuromagnetic signals are described from which it is concluded that magnetoencephalography is potentially much more applicable than electroencephalography for localizing the sources of a variety of neural activities in the brain. The magnitudes of typical neuromagnetic signals are discussed. Selected examples of MEG studies are given. Recent experiments which appear to indicate directly the association of spreading cortical depression with migraine headache are briefly described.

Brain↗
PubMed2002

Brain function in fetal alcohol syndrome assessed by single photon emission computed tomography.

This case series reports results of single photon emission computed tomography (SPECT) studies in three patients with fetal alcohol syndrome (FAS), who had previously undergone structural magnetic resonance imaging (MR). The MR studies revealed several brain anomalies, including microcephaly, agenesis or hypoplasia of corpus callosum and agenesis of hippocampal commissure. The SPECT data revealed that the CBF was reduced by at least 25% in the temporal region relative to the cerebellum in all three patients. By contrast, the temporal-cerebellar differences were between 4% and 7% in two controls. The functional abnormalities in FAS, like neuroanatomical abnormalities, are likely to be multiple and varied because of heterogeneity of this syndrome. Our findings suggest the need for a larger study to test the hypothesis that temporal lobe abnormalities are a notable occurrence in FAS. Discovery of specific regional brain dysfunctions (such as temporal lobe dysfunction) that are particularly vulnerable to alcohol's teratogenic effect may allow clinicians and researchers to look for markers useful in FAS screening and may have implications for prevention and treatment of FAS.

Adolescent↗
PubMed2006

Independent component model of the default-mode brain function: Assessing the impact of active thinking.

The "default-mode" network is an ensemble of cortical regions, which are typically deactivated during demanding cognitive tasks in functional magnetic resonance imaging (fMRI) studies. Using functional connectivity, this network can be conceptualized and studied as a "stand-alone" function or system. Regardless of the task, independent component analysis (ICA) produces a picture of the "default-mode" function even when the subject is performing a simple sensori-motor task or just resting in the scanner. This has boosted the use of default-mode fMRI for non-invasive research in brain disorders. Here, we studied the effect of cognitive load modulation of fMRI responses on the ICA-based pictures of the default-mode function. In a standard graded working memory study based on the n-back task, we used group-level ICA to explore the variability of the default-mode network related to the engagement in the task, in 10 healthy volunteers. The analysis of the default-mode components highlighted similarities and differences in the layout under three different cognitive loads. We found a load-related general increase of deactivation in the cortical network. Nonetheless, a variable recruitment of the cingulate regions was evident, with greater extension of the anterior and lesser extension of the posterior clusters when switching from lower to higher working memory loads. A co-activation of the hippocampus was only found under no working memory load. As a generalization of our results, the variability of the default-mode pattern may link the default-mode system as a whole to cognition and may more directly support use of the ICA model for evaluating cognitive decline in brain disorders.

Adult↗
PubMed2006

Three-dimensional locations and boundaries of motor and premotor cortices as defined by functional brain imaging: a meta-analysis.

The mesial premotor cortex (pre-supplementary motor area and supplementary motor area proper), lateral premotor cortex (dorsal premotor cortex and ventral premotor cortex), and primary sensorimotor cortex (primary motor cortex and primary somatosensory cortex) have been identified as key cortical areas for sensorimotor function. However, the three-dimensional (3-D) anatomic boundaries between these regions remain unclear. In order to clarify the locations and boundaries for these six sensorimotor regions, we surveyed 126 articles describing pre-supplementary motor area, supplementary motor area proper, dorsal premotor cortex, ventral premotor cortex, primary motor cortex, and primary somatosensory cortex. Using strict inclusion criteria, we recorded the reported normalized stereotaxic coordinates (Talairach and Tournoux or MNI) from each experiment. We then computed the probability distributions describing the likelihood of activation, and characterized the shape, extent, and area of each sensorimotor region in 3-D. Additionally, we evaluated the nature of the overlap between the six sensorimotor regions. Using the findings from this meta-analysis, along with suggestions and guidelines of previous researchers, we developed the Human Motor Area Template (HMAT) that can be used for ROI analysis. HMAT is available through e-mail from the corresponding author.

Algorithms↗
PubMedDate not supplied

Noninvasive detection of functional brain activity with near-infrared diffusing-wave spectroscopy.

We use near-infrared dynamic multiple scattering of light [diffusing-wave spectroscopy (DWS)] to detect the activation of the somato-motor cortex in 11 right-handed volunteers performing a finger opposition task separately with their right and left hands. Temporal autocorrelation functions g(1)(r,tau) of the scattered light field are measured during 100-s periods of motor task alternating with 100-s resting baseline periods. From an analysis of the experimental data with an analytical theory for g(1)(r,tau) from a three-layer geometry with optical and dynamical heterogeneity representing scalp, skull, and cortex, we obtain quantitative estimates of the diffusion coefficient in cortical regions. Consistent with earlier results, the measured cortical diffusion coefficient is found to be increased during the motor task, with a strong contralateral and a weaker ipsilateral increase consistent with the known brain hemispheric asymmetry for right-handed subjects. Our results support the interpretation of the increase of the cortical diffusion coefficient during finger opposition being due to the functional increase in cortical blood flow rate related to vasodilation.

Adult↗