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Cortical Function (cortical + function)

Distribution by Scientific Domains

Medical Sciences	73%
Life Sciences	20%

Selected Abstracts

Virtual Lesions Examining Cortical Function with Reversible Deactivation

EUROPEAN JOURNAL OF NEUROLOGY, Issue 1 2003
K. A. Jellinger
No abstract is available for this article. [source]

Neurological examination of cortical function deficits

ACTA NEUROLOGICA SCANDINAVICA, Issue 2009
O. B. Tysnes
Human cortical functions have been elucidated by studies of deficits in traumatic and vascular brain damage, outcomes after elective neurosurgical procedures, studies in primates and in more recent years by imaging techniques. Cortical functions are well-defined for primary cortical areas like motor, sensory and visual functions. More complex cortical functions like language and to some degree memory are also well clarified. The associative cortical areas are more difficult to study as functions are integrated to and modulate primary cortical functions. Nevertheless, the structural basis for symptoms like neglect, apraxia and agnosia has been well established. Recent data from functional imaging indicate that large and diverse areas of the cerebral cortex are involved in planning motor tasks or coding (memory). This review focuses on the clinical neurological evaluation of cortical function deficits. [source]

Probing the corticospinal link between the motor cortex and motoneurones: some neglected aspects of human motor cortical function

ACTA PHYSIOLOGICA, Issue 4 2010
N. C. Petersen
Abstract This review considers the operation of the corticospinal system in primates. There is a relatively widespread cortical area containing corticospinal outputs to a single muscle and thus a motoneurone pool receives corticospinal input from a wide region of the cortex. In addition, corticospinal cells themselves have divergent intraspinal branches which innervate more than one motoneuronal pool but the synergistic couplings involving the many hand muscles are likely to be more diverse than can be accommodated simply by fixed patterns of corticospinal divergence. Many studies using transcranial magnetic stimulation of the human motor cortex have highlighted the capacity of the cortex to modify its apparent excitability in response to altered afferent inputs, training and various pathologies. Studies using cortical stimulation at ,very low' intensities which elicit only short-latency suppression of the discharge of motor units have revealed that the rapidly conducting corticospinal axons (stimulated at higher intensities) drive motoneurones in normal voluntary contractions. There are also major non-linearities generated at a spinal level in the relation between corticospinal output and the output from the motoneurone pool. For example, recent studies have revealed that the efficacy of the human corticospinal connection with motoneurones undergoes activity-dependent changes which influence the size of voluntary contractions. Hence, corticospinal drives must be sculpted continuously to compensate for the changing functional efficacy of the descending systems which activate the motoneurones. This highlights the need for proprioceptive monitoring of movements to ensure their accurate execution. [source]

Aging and the interaction of sensory cortical function and structure

HUMAN BRAIN MAPPING, Issue 1 2009
Ann M. Peiffer
Abstract Even the healthiest older adults experience changes in cognitive and sensory function. Studies show that older adults have reduced neural responses to sensory information. However, it is well known that sensory systems do not act in isolation but function cooperatively to either enhance or suppress neural responses to individual environmental stimuli. Very little research has been dedicated to understanding how aging affects the interactions between sensory systems, especially cross-modal deactivations or the ability of one sensory system (e.g., audition) to suppress the neural responses in another sensory system cortex (e.g., vision). Such cross-modal interactions have been implicated in attentional shifts between sensory modalities and could account for increased distractibility in older adults. To assess age-related changes in cross-modal deactivations, functional MRI studies were performed in 61 adults between 18 and 80 years old during simple auditory and visual discrimination tasks. Results within visual cortex confirmed previous findings of decreased responses to visual stimuli for older adults. Age-related changes in the visual cortical response to auditory stimuli were, however, much more complex and suggested an alteration with age in the functional interactions between the senses. Ventral visual cortical regions exhibited cross-modal deactivations in younger but not older adults, whereas more dorsal aspects of visual cortex were suppressed in older but not younger adults. These differences in deactivation also remained after adjusting for age-related reductions in brain volume of sensory cortex. Thus, functional differences in cortical activity between older and younger adults cannot solely be accounted for by differences in gray matter volume. Hum Brain Mapp 2009. © 2007 Wiley-Liss, Inc. [source]

A decade of functional brain imaging applied to bladder control

NEUROUROLOGY AND URODYNAMICS, Issue 1 2010
Clare J. Fowler
Abstract Over the last 10 years functional brain imaging has emerged as the most powerful technique for studying human brain function. Although the literature is now vast, including studies of every imaginable aspect of cortical function, the number of studies that have been carried out examining brain control of bladder function is relatively limited. Nevertheless those that have been reported have transformed our thinking. This article reviews that development in the context of emerging ideas of interoception and a working model of brain activity during bladder filling and emptying is proposed. Some studies have also been carried out using functional imaging methods to examine pathophysiological bladder conditions or the effect of treatments and these are reviewed and future work anticipated. Neurourol. Urodynam. 29: 49,55, 2010. © 2009 Wiley-Liss, Inc. [source]

Developmental plasticity connects visual cortex to motoneurons after stroke

ANNALS OF NEUROLOGY, Issue 1 2010
Anna Basu BM
We report motor cortical function in the left occipital cortex of a subject who suffered a left middle cerebral artery stroke early in development. Transcranial magnetic stimulation of the left occipital cortex evoked contraction of right hand muscles. Electroencephalogram recorded over the left occipital cortex showed: 1) coherence with electromyogram from a right hand muscle; 2) a typical sensorimotor Mu rhythm at rest that was suppressed during contraction of right hand muscles. This is the first evidence that cortical plasticity extends beyond reshaping of primary sensory cortical fields to respecification of the cortical origin of subcortically projecting pathways. ANN NEUROL 2010;67:132,136 [source]

Propagation of spreading depression inversely correlates with cortical myelin content,

ANNALS OF NEUROLOGY, Issue 3 2009
Doron Merkler MD
Objective Cortical myelin can be severely affected in patients with demyelinating disorders of the central nervous system. However, the functional implication of cortical demyelination remains elusive. In this study, we investigated whether cortical myelin influences cortical spreading depression (CSD). Methods CSD measurements were performed in rodent models of toxic and autoimmune induced cortical demyelination, in neuregulin-1 type I transgenic mice displaying cortical hypermyelination, and in glial fibrillary acidic protein,transgenic mice exhibiting pronounced astrogliosis. Results Cortical demyelination, but not astrogliosis or inflammation per se, was associated with accelerated CSD. In contrast, hypermyelinated neuregulin-1 type I transgenic mice displayed a decelerated CSD propagation. Interpretation Cortical myelin may be crucially involved in the stabilization and buffering of extracellular ion content that is decisive for CSD propagation velocity and cortical excitability, respectively. Our data thus indicate that cortical involvement in human demyelinating diseases may lead to relevant alterations of cortical function. Ann Neurol 2009;66:355,365 [source]

Diaschisis after thalamic stroke: a comparison of metabolic and structural changes in a patient with amnesic syndrome

ACTA NEUROLOGICA SCANDINAVICA, Issue 2007
V. Stenset
Introduction,, We present a patient with a left anteromedial thalamic lesion with an amnesic syndrome. The patient underwent neuropsychological testing, cerebrospinal fluid (CSF) analyses, magnetic resonance imaging (MRI) [T2, flair, and diffusion tensor imaging (DTI)] and [18F]-2-fluoro-deoxy- d -glucose positron emission tomography (FDG-PET) to assess indirect effects of thalamic lesions on cortical function. Case report,, A 67-year-old right-handed woman was admitted to a university-based memory unit because of memory and concentration problems. Neuropsychological testing revealed dysfunction of episodic memory, semantic memory and working memory. General intellectual function and attention capacity were preserved. MRI revealed an anteromedial thalamic lesion in the left hemisphere. FDG-PET showed decreased uptake in the frontal, parietal and temporal lobes of the left hemisphere. Regions of interest (ROI) in white matter were selected and left and right hemispheres were compared. Fractional anisotropy (FA) in ROI representing thalamo-cortical connections were decreased in the left hemisphere when compared with the right. Conclusion,, The results show the importance of a network that include the anterior and dorsomedian nuclei, which influence the activity in areas of the cortex responsible for memory processes. The imaging findings suggest that areas of cortical diaschisis after thalamic infarction correspond to areas affected by thalamo-cortical fibre loss as measured with FA. [source]

Imaging auditory hallucinations in schizophrenia

ACTA NEUROPSYCHIATRICA, Issue 2 2006
D. K. Tracy
It is increasingly recognized that there are a heterogeneous range of symptoms within the syndrome of schizophrenia and that some of these also occur frequently within other psychiatric conditions. An approach similar to that in neuropsychology, where cases are grouped based on a discrete deficit, or in this case a discrete symptom, rather than a cause or diagnosis, may be useful in exploring the neural correlates of psychotic symptomatology. Functional neuroimaging provides an excellent tool for investigating the in vivo cortical function of patients with schizophrenia. Auditory verbal hallucinations are one of the most commonly occurring psychotic symptoms in schizophrenia; and this paper examines the progress that has been made in utilizing neuroimaging techniques to investigate auditory hallucinations in schizophrenia and review potential implications for treatment and future directions for research. [source]

Clinical application of the multifocal visual evoked potential

CLINICAL AND EXPERIMENTAL OPTOMETRY, Issue 3 2004
David P. Crewther PhD
Background: Measures of visual function thresholds such as visual acuity and visual fields are generally dependent on subjective responses and assume maintenance of fixation, attention and motivation. In the young, elderly, cognitively impaired or malingering populations, such measures may be inaccurate or difficult to obtain. The Visual Evoked Response Imaging System (VERIS) has been claimed to give more objective topographic recordings of retinal and cortical function. This paper aims to explore the adequacy of this technique in four unusual, unrelated, clinically difficult cases. Methods: Multifocal visual evoked potentials (mfVEPs) recorded on the VERIS System 3.01 are used to assess visual function in four cases with contradictory clinical findings or unreliable subjective responses. Results: Patient 1 had sustained a head injury and had normal ocular and pupil examination but light perception in the right eye and 6/5 acuity in the left. Multifocal VEPs showed a marked depression of the right visual field with little macular response. Patient 2 had sustained a head injury, had a left field hemianopia, possible macular sparing and loss of much of the right field, reduced but variable visual acuities, good near vision and normal ocular fundi. Multifocal VEPs showed a severe depression in both visual fields (L more than R) with little macular response. Patient 3 had a left optic nerve meningioma and experienced great difficulty with visual field assessment. mfVEPs showed a bilateral depression in the superior field particularly the left field, with a larger deficit in the left eye. Patient 4 had unexplained visual acuity and peripheral field deficits. mfVEP results were inconclusive in this case. Discussion: Where there is difficulty performing traditional techniques or conflicting clinical findings, mfVEPs may provide additional objective information to aid in the assessment of patients. [source]

,Prefrontal' cognitive performance of healthy subjects positively correlates with cerebral FDOPA influx: An exploratory [18F]-fluoro-L-DOPA-PET investigation

HUMAN BRAIN MAPPING, Issue 10 2007
Ingo Vernaleken
Abstract Dopamine neurotransmission influences those cognitive processes, which are generally regarded as prefrontal cortical functions. In previous positron-emission-tomography (PET) studies, net blood-brain clearance of [18F]-fluoro-l-DOPA (FDOPA) correlated with impaired cognitive performance in patients with Parkinson's disease or schizophrenia. We hypothesized that FDOPA influx also correlates with performance of cognitive tasks associated with prefrontal functioning in healthy volunteers. The net blood-brain clearance of FDOPA (K) was mapped in a group of 11 healthy volunteers and calculated in striatal volumes-of-interest. The Wisconsin-Card-Sorting-Test (WCST), Stroop-Test, Trail-Making-Test (TMT-A/B), and Continuous-Performance-Test (CPT-M) had been administered previously to the same subjects. No correlation of K with perseverative errors in WCST or age could be found. However, there were significant positive correlations between the magnitude of K in caudate nucleus, putamen, and midbrain with performance of the TMT-B, CPT-M, and the Stroop test. Highest correlations were found between the time needed to perform the Stroop interference task and the K of striatal areas (Caudate nucleus: ,0.780, P = 0.005; putamen: ,0.870, P < 0. 001). Thus, the present findings reveal a strong correlation between dopamine synthesis capacity in striatum of healthy volunteers and performance of cognitive tasks linked to the prefrontal cortex. Hum Brain Mapp 2006. © 2006 Wiley-Liss, Inc. [source]

Medicinal chemistry approaches for the treatment and prevention of Alzheimer's disease

MEDICINAL RESEARCH REVIEWS, Issue 1 2003
S.O. Bachurin
Abstract Alzheimer's disease (AD) is the most common form of dementia, which is characterised by progressive deterioration of memory and higher cortical functions that ultimately result in total degradation of intellectual and mental activities. Modern strategies in the search of new therapeutic approaches are based on the morphological and biochemical characteristics of AD, and focused on following directions: agents that compensate the hypofunction of cholinergic system, agents that interfere with the metabolism of beta-amyloid peptide, agents that protect nerve cells from toxic metabolites formed in neurodegenerative processes, agents that activate other neurotransmitter systems that indirectly compensate for the deficit of cholinergic functions, agents that affect the process of the formation of neurofibrillary tangles, anti-inflammatory agents that prevent the negative response of nerve cells to the pathological process. The goal of the present review is the validation and an analysis from the point of view of medicinal chemistry of the principles of the directed search of drugs for the treatment and prevention of AD and related neurodegenerative disorders. It is based on systematization of the data on biochemical and structural similarities in the interaction between physiologically active compounds and their biological targets related to the development of such pathologies. The main emphasis is on cholinomimetic, anti-amyloid and anti-metabolic agents, using the data that were published during the last 3 to 4 years, as well as the results of clinical trials presented on corresponding websites. © 2002 Wiley Periodicals, Inc. Med Res Rev, 23, No. 1, 48,88, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/med.10026 [source]

ACTH and adrenocortical gap junctions

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2003
Sandra A. Murray
Abstract Since the initial identification of gap junctions in the adrenal gland, it has been proposed that a system involving direct cell,cell communication might be involved in adrenal cortical functions. Gap junction channels do, in fact, provide pathways for direct intercellular exchange of small molecules (<1,000 Da), many of which have the potential to influence a wide range of cellular activities. Gap junctions are composed of proteins called connexin which, in the adrenal cortex, have proven to be remarkably consistent in both type and zonal distribution with connexin 43 (Cx43) as the predominant component in mammalian adrenal glands thus far evaluated. Only the inner two zones of the cortex (zonae fasciculata and reticularis) exhibit significant amounts of Cx43 and functional coupling. Adrenocorticotropin (ACTH) has been shown to increase Cx43 protein in vivo and in vitro, and a strong correlation has been noted between the presence of gap junctions and certain adrenal cortical functions, especially steroidogenic capacity and cell proliferation. This review summarizes evidence of the Cx43 expression in adrenal cortical cells and the likely role of Cx43 in steroidogenesis and cell proliferation. It is concluded that control of gap junction expression in the adrenal gland is hormonally dependent and is functionally linked to adrenal gland zonation. Microsc. Res. Tech. 61:240,246, 2003. © 2003 Wiley-Liss, Inc. [source]

Neurological examination of cortical function deficits

2126: Retinal and cortical functions in adult mice lacking cannabinoid receptors

ACTA OPHTHALMOLOGICA, Issue 2010
C CASANOVA
Purpose Cannabinoid receptor type 1 (CB1R) has been localized in the adult retina of rodents. It is expressed in cones, horizontal, bipolar, some amacrine and ganglion cells. The expression of the cannabinoid receptor type 2 (CB2R) mRNA in the retina of adult rats was also reported. The goal of the present study was to investigate the functional roles of CB1R and CB2R in the retina by comparing retinal electrophysiological responses and cortical optical signals in normal and genetically modified mice. Methods Experiments were conducted on four different groups of C57BL/6 mice: CB1R wild type (WT), CB1R knockout (KO), CB2R WT and KO. Scotopic electroretinograms (ERG) luminance-response functions and photopic ERGs were recorded. In a subset of CB1 groups, intrinsic signals acquired by optical brain imaging were used to determine spatial frequency, contrast sensitivity and retinotopic maps in the visual cortex. Results The CB1R KO retina showed a stronger photopic response. No differences were observed for scotopic responses. For the CB2R groups, the scotopic b-wave response was stronger in the KO mice. No differences could be seen between visual cortices maps with respect to SF and contrast sensitivity. Retinotopic maps differed only along the azimuth. Significant differences were observed between hemodynamic response functions. Conclusion These results indicate that CB receptors can play a regulatory effect on the neurovascular coupling at the retinal and cortical levels and on the functional organization of the mice visual cortex along the azimuth Axis.(NSERC) [source]