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Occipital Cortex (occipital + cortex)

Distribution by Scientific Domains

Medical Sciences	50%
Life Sciences	43%

Distribution within Medical Sciences

Neurology	46%
Psychiatry	26%

Selected Abstracts

Plasticity of the visual system after early brain damage

DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 10 2010
ANDREA GUZZETTA
The aim of this review is to discuss the existing evidence supporting different processes of visual brain plasticity after early damage, as opposed to damage that occurs during adulthood. There is initial evidence that some of the neuroplastic mechanisms adopted by the brain after early damage to the visual system are unavailable at a later stage. These are, for example, the ability to differentiate functional tissue within a larger dysplastic cortex during its formation, or to develop new thalamo-cortical connections able to bypass the lesion and reach their cortical destination in the occipital cortex. The young brain also uses the same mechanisms available at later stages of development but in a more efficient way. For example, in people with visual field defects of central origin, the anatomical expansion of the extrastriatal visual network is greater after an early lesion than after a later one, which results in more efficient mechanisms of visual exploration of the blind field. A similar mechanism is likely to support some of the differences found in people with blindsight, the phenomenon of unconscious visual perception in the blind field. In particular, compared with people with late lesions, those with early brain damage appear to have stronger subjective awareness of stimuli hitting the blind visual field, reported as a conscious feeling that something is present in the visual field. Expanding our knowledge of these mechanisms could help the development of early therapeutic interventions aimed at supporting and enhancing visual reorganization at a time of greatest potential brain plasticity. [source]

Relative increase in choline in the occipital cortex in chronic fatigue syndrome

ACTA PSYCHIATRICA SCANDINAVICA, Issue 3 2002
B. K. Puri
Puri BK, Counsell SJ, Zaman R, Main J, Collins AG, Hajnal JV, Davey NJ. Relative increase in choline in the occipital cortex in chronic fatigue syndrome. Acta Psychiatr Scand 2002: 106: 224,226. © Blackwell Munksgaard 2002. Objective:,To test the hypothesis that chronic fatigue syndrome (CFS) is associated with altered cerebral metabolites in the frontal and occipital cortices. Method:,Cerebral proton magnetic resonance spectroscopy (1H MRS) was carried out in eight CFS patients and eight age- and sex-matched healthy control subjects. Spectra were obtained from 20 × 20 × 20 mm3 voxels in the dominant motor and occipital cortices using a point-resolved spectroscopy pulse sequence. Results:,The mean ratio of choline (Cho) to creatine (Cr) in the occipital cortex in CFS (0.97) was significantly higher than in the controls (0.76; P=0.008). No other metabolite ratios were significantly different between the two groups in either the frontal or occipital cortex. In addition, there was a loss of the normal spatial variation of Cho in CFS. Conclusion:,Our results suggest that there may be an abnormality of phospholipid metabolism in the brain in CFS. [source]

Characterization of Neuronal Migration Disorders in Neocortical Structures: Loss or Preservation of Inhibitory Interneurons?

EPILEPSIA, Issue 7 2000
Petra Schwarz
Summary: Purpose: Neuronal migration disorders (NMD) are often associated with therapy-resistant epilepsy. In human cerebral cortex, this hyperexcitability has been correlated with a loss of inhibitory interneurons. We used a rat model of focal cortical NMD (microgyria) to determine whether the expression of epileptiform activity in this model coincides with a decrease in inhibitory interneurons. Methods: In 2- to 4-month-old rats, the density of interneurons immunoreactive for ,-aminobutyric acid (GABA), cal-bindin, and parvalbumin was determined in fronto-parietal cortex in nine 200-,m-wide sectors located up to 2.5 mm lateral and 2.0 mm medial from the lesion center in primary parietal cortex (Par 1). Quantitative measurements in homotopic areas of age-matched sham-operated rats served as controls. Results: The freeze lesion performed in newborn rat cortex resulted in adult rats with a microgyrus extending in a rostro-caudal direction from frontal to occipital cortex. The density of GABA- and parvalbumin-positive neurons in fronto-parietal cortex was not significantly different between lesioned and control animals. Only the density of calbindin-immunoreactive neurons located 1.0 mm lateral and 0.5 mm medial from the lesion was significantly (Student t test, p > 0.05) larger in freeze-lesioned rats (5.817 ± 562 and 6,400 ± 795 cells per mm3, respectively; n = 12) compared with measurements in homotopic regions in Parl cortex of controls (4,507 ± 281 and 4,061 ± 319 cells per mm3, respectively; n = 5). Conclusions: The previously reported widespread functional changes in this model of cortical NMD are not related to a general loss of inhibitory interneurons. Other factors, such as a decrease in GABA receptor density, modifications in GABAA receptor subunit composition, or alterations in the excitatory network, e.g., an increase in the density of calbindin-immunoreactive pyramidal cells, more likely contribute to the global disinhibition and widespread expression of pathophysiological activity in this model of cortical NMD. [source]

Enhancing multisensory spatial orienting by brain polarization of the parietal cortex

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2010
Nadia Bolognini
Abstract Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that induces polarity-specific excitability changes in the human brain, therefore altering physiological, perceptual and higher-order cognitive processes. Here we investigated the possibility of enhancing attentional orienting within and across different sensory modalities, namely visual and auditory, by polarization of the posterior parietal cortex (PPC), given the putative involvement of this area in both unisensory and multisensory spatial processing. In different experiments, we applied anodal or sham tDCS to the right PPC and, for control, anodal stimulation of the right occipital cortex. Using a redundant signal effect (RSE) task, we found that anodal tDCS over the right PPC significantly speeded up responses to contralateral targets, regardless of the stimulus modality. Furthermore, the effect was dependant on the nature of the audiovisual enhancement, being stronger when subserved by a probabilistic mechanism induced by blue visual stimuli, which probably involves processing in the PPC. Hence, up-regulating the level of excitability in the PPC by tDCS appears a successful approach for enhancing spatial orienting to unisensory and crossmodal stimuli. Moreover, audiovisual interactions mostly occurring at a cortical level can be selectively enhanced by anodal PPC tDCS, whereas multisensory integration of stimuli, which is also largely mediated at a subcortical level, appears less susceptible to polarization of the cortex. [source]

Perceptual load interacts with stimulus processing across sensory modalities

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2009
J. Klemen
Abstract According to perceptual load theory, processing of task-irrelevant stimuli is limited by the perceptual load of a parallel attended task if both the task and the irrelevant stimuli are presented to the same sensory modality. However, it remains a matter of debate whether the same principles apply to cross-sensory perceptual load and, more generally, what form cross-sensory attentional modulation in early perceptual areas takes in humans. Here we addressed these questions using functional magnetic resonance imaging. Participants undertook an auditory one-back working memory task of low or high perceptual load, while concurrently viewing task-irrelevant images at one of three object visibility levels. The processing of the visual and auditory stimuli was measured in the lateral occipital cortex (LOC) and auditory cortex (AC), respectively. Cross-sensory interference with sensory processing was observed in both the LOC and AC, in accordance with previous results of unisensory perceptual load studies. The present neuroimaging results therefore warrant the extension of perceptual load theory from a unisensory to a cross-sensory context: a validation of this cross-sensory interference effect through behavioural measures would consolidate the findings. [source]

The essential role of Broca's area in imitation

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2003
Marc Heiser
Abstract The posterior sector of Broca's area (Brodmann area 44), a brain region critical for language, may have evolved from neurons active during observation and execution of manual movements. Imaging studies showing increased Broca's activity during execution, imagination, imitation and observation of hand movements support this hypothesis. Increased Broca's activity in motor task, however, may simply be due to inner speech. To test whether Broca's area is essential to imitation, we used repetitive transcranial magnetic stimulation (rTMS), which is known to transiently disrupt functions in stimulated areas. Subjects imitated finger key presses (imitation) or executed finger key presses in response to spatial cues (control task). While performing the tasks, subjects received rTMS over the left and right pars opercularis of the inferior frontal gyrus (where Brodmann area 44 is probabilistically located) and over the occipital cortex. There was significant impairment in imitation, but not in the control task, during rTMS over left and right pars opercularis compared to rTMS over the occipital cortex. This suggests that Broca's area is a premotor region essential to finger movement imitation. [source]

Homeostatic sleep regulation is preserved in mPer1 and mPer2 mutant mice

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2002
Caroline Kopp
Abstract A limited set of genes, Clock, Bmal1, mPer1, mPer2, mCry1 and mCry2, has been shown to be essential for the generation of circadian rhythms in mammals. It has been recently suggested that circadian genes might be involved in sleep regulation. We investigated the role of mPer1 and mPer2 genes in the homeostatic regulation of sleep by comparing sleep of mice lacking mPER1 (mPer1 mutants) or a functional mPER2 (mPer2 mutants), and wild-type controls (WT) after 6 h of sleep deprivation (SD). Our main result showed that after SD, all mice displayed the typical increase of slow-wave activity (SWA; EEG power density between 0.75 and 4 Hz) in nonREM sleep, reflecting the homeostatic response to SD. This increase was more prominent over the frontal cortex as compared to the occipital cortex. The genotypes did not differ in the effect of SD on the occipital EEG, while the effect on the frontal EEG was initially diminished in both mPer mutants. Differences between the genotypes were seen in the 24-h distribution of sleep, reflecting especially the phase advance of motor activity onset observed in mPer2 mutants. While the daily distribution of sleep was modulated by mPer1 and mPer2 genes, sleep homeostasis reflected by the SWA increase after 6-h SD was preserved in the mPer mutants. The results provide further evidence for the independence of the circadian and the homeostatic components underlying sleep regulation. [source]

Visual Cortex Excitability in Migraine With and Without Aura

HEADACHE, Issue 6 2001
Wim M. Mulleners MD
Objectives.,Previous research using transcranial magnetic stimulation has produced equivocal findings concerning thresholds for the generation of visual phosphenes in migraine with aura. These studies were methodologically varied and did not systematically address cortical excitability in migraine without aura. We therefore studied magnetophosphene thresholds in both migraine with aura and migraine without aura compared with headache-free controls. Methods.,Sixteen subjects with migraine with aura and 12 subjects with migraine without aura were studied and compared with 16 sex- and age-matched controls. Using a standardized transcranial magnetic stimulation protocol of the occipital cortex, we assessed the threshold stimulation intensity at which subjects just perceived phosphenes via a method of alternating course and fine-tuning of stimulator output. Results.,There were no significant differences across groups in the proportion of subjects seeing phosphenes. However, the mean threshold at which phosphenes were reported was significantly lower in both migraine groups (migraine with aura=47%, migraine without aura=46%) than in controls (66%). Moreover, there was no significant correlation between individual phosphene threshold and the time interval to the closest migraine attack. Conclusion.,Our findings confirm that the occipital cortex is hyperexcitable in the migraine interictum, both in migraine with and without aura. [source]

Functional connectivity with the hippocampus during successful memory formation

HIPPOCAMPUS, Issue 8 2005
Charan Ranganath
Abstract Although it is well established that the hippocampus is critical for episodic memory, little is known about how the hippocampus interacts with cortical regions during successful memory formation. Here, we used event-related functional magnetic resonance imaging (fMRI) to identify areas that exhibited differential functional connectivity with the hippocampus during processing of novel objects that were subsequently remembered or forgotten on a postscan test. Functional connectivity with the hippocampus was enhanced during successful, as compared with unsuccessful, memory formation, in a distributed network of limbic cortical areas,including perirhinal, orbitofrontal, and retrosplenial/posterior cingulate cortex,that are anatomically connected with the hippocampal formation. Increased connectivity was also observed in lateral temporal, medial parietal, and medial occipital cortex. These findings demonstrate that successful memory formation is associated with transient increases in cortico-hippocampal interaction. © 2005 Wiley-Liss, Inc. [source]

Enhanced effectiveness in visuo-haptic object-selective brain regions with increasing stimulus salience

HUMAN BRAIN MAPPING, Issue 5 2010
Sunah Kim
Abstract The occipital and parietal lobes contain regions that are recruited for both visual and haptic object processing. The purpose of the present study was to characterize the underlying neural mechanisms for bimodal integration of vision and haptics in these visuo-haptic object-selective brain regions to find out whether these brain regions are sites of neuronal or areal convergence. Our sensory conditions consisted of visual-only (V), haptic-only (H), and visuo-haptic (VH), which allowed us to evaluate integration using the superadditivity metric. We also presented each stimulus condition at two different levels of signal-to-noise ratio or salience. The salience manipulation allowed us to assess integration using the rule of inverse effectiveness. We were able to localize previously described visuo-haptic object-selective regions in the lateral occipital cortex (lateral occipital tactile-visual area) and the intraparietal sulcus, and also localized a new region in the left anterior fusiform gyrus. There was no evidence of superadditivity with the VH stimulus at either level of salience in any of the regions. There was, however, a strong effect of salience on multisensory enhancement: the response to the VH stimulus was more enhanced at higher salience across all regions. In other words, the regions showed enhanced integration of the VH stimulus with increasing effectiveness of the unisensory stimuli. We called the effect "enhanced effectiveness." The presence of enhanced effectiveness in visuo-haptic object-selective brain regions demonstrates neuronal convergence of visual and haptic sensory inputs for the purpose of processing object shape. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source]

Spatiotemporal mapping of sex differences during attentional processing

HUMAN BRAIN MAPPING, Issue 9 2009
Andres H. Neuhaus
Abstract Functional neuroimaging studies have increasingly aimed at approximating neural substrates of human cognitive sex differences elicited by visuospatial challenge. It has been suggested that females and males use different behaviorally relevant neurocognitive strategies. In females, greater right prefrontal cortex activation has been found in several studies. The spatiotemporal dynamics of neural events associated with these sex differences is still unclear. We studied 22 female and 22 male participants matched for age, education, and nicotine with 29-channel-electroencephalogram recorded under a visual selective attention paradigm, the Attention Network Test. Visual event-related potentials (ERP) were topographically analyzed and neuroelectric sources were estimated. In absence of behavioral differences, ERP analysis revealed a novel frontal-occipital second peak of visual N100 that was significantly increased in females relative to males. Further, in females exclusively, a corresponding central ERP component at around 220 ms was found; here, a strong correlation between stimulus salience and sex difference of the central ERP component amplitude was observed. Subsequent source analysis revealed increased cortical current densities in right rostral prefrontal (BA 10) and occipital cortex (BA 19) in female subjects. This is the first study to report on a tripartite association between sex differences in ERPs, visual stimulus salience, and right prefrontal cortex activation during attentional processing. Hum Brain Mapp 2009. © 2009 Wiley-Liss, Inc. [source]

Rolandic alpha and beta EEG rhythms' strengths are inversely related to fMRI-BOLD signal in primary somatosensory and motor cortex

HUMAN BRAIN MAPPING, Issue 4 2009
Petra Ritter
Abstract Similar to the posterior alpha rhythm, pericentral (Rolandic) EEG rhythms in the alpha and beta frequency range are referred to as "idle rhythms" indicating a "resting state" of the respective system. The precise function of these rhythms is not clear. We used simultaneous EEG-fMRI during a bimanual motor task to localize brain areas involved in Rolandic alpha and beta EEG rhythms. The identification of these rhythms in the MR environment was achieved by a blind source separation algorithm. Rhythm "strength", i.e. spectral power determined by wavelet analysis, inversely correlated most strongly with the fMRI-BOLD signal in the postcentral cortex for the Rolandic alpha (mu) rhythm and in the precentral cortex for the Rolandic beta rhythm. FMRI correlates of Rolandic alpha and beta rhythms were distinct from those associated with the posterior "classical" alpha rhythm, which correlated inversely with the BOLD signal in the occipital cortex. An inverse correlation with the BOLD signal in the respective sensory area seems to be a general feature of "idle rhythms". Hum Brain Mapp 2009. © 2008 Wiley-Liss, Inc. [source]

Discrete dynamic Bayesian network analysis of fMRI data

HUMAN BRAIN MAPPING, Issue 1 2009
John Burge
Abstract We examine the efficacy of using discrete Dynamic Bayesian Networks (dDBNs), a data-driven modeling technique employed in machine learning, to identify functional correlations among neuroanatomical regions of interest. Unlike many neuroimaging analysis techniques, this method is not limited by linear and/or Gaussian noise assumptions. It achieves this by modeling the time series of neuroanatomical regions as discrete, as opposed to continuous, random variables with multinomial distributions. We demonstrated this method using an fMRI dataset collected from healthy and demented elderly subjects (Buckner, et al., 2000: J Cogn Neurosci 12:24-34) and identify correlates based on a diagnosis of dementia. The results are validated in three ways. First, the elicited correlates are shown to be robust over leave-one-out cross-validation and, via a Fourier bootstrapping method, that they were not likely due to random chance. Second, the dDBNs identified correlates that would be expected given the experimental paradigm. Third, the dDBN's ability to predict dementia is competitive with two commonly employed machine-learning classifiers: the support vector machine and the Gaussian naïve Bayesian network. We also verify that the dDBN selects correlates based on non-linear criteria. Finally, we provide a brief analysis of the correlates elicited from Buckner et al.'s data that suggests that demented elderly subjects have reduced involvement of entorhinal and occipital cortex and greater involvement of the parietal lobe and amygdala in brain activity compared with healthy elderly (as measured via functional correlations among BOLD measurements). Limitations and extensions to the dDBN method are discussed. Hum Brain Mapp, 2009. © 2007 Wiley-Liss, Inc. [source]

Selective visuo-haptic processing of shape and texture

HUMAN BRAIN MAPPING, Issue 10 2008
Randall Stilla
Abstract Previous functional neuroimaging studies have described shape-selectivity for haptic stimuli in many cerebral cortical regions, of which some are also visually shape-selective. However, the literature is equivocal on the existence of haptic or visuo-haptic texture-selectivity. We report here on a human functional magnetic resonance imaging (fMRI) study in which shape and texture perception were contrasted using haptic stimuli presented to the right hand, and visual stimuli presented centrally. Bilateral selectivity for shape, with overlap between modalities, was found in a dorsal set of parietal areas: the postcentral sulcus and anterior, posterior and ventral parts of the intraparietal sulcus (IPS); as well as ventrally in the lateral occipital complex. The magnitude of visually- and haptically-evoked activity was significantly correlated across subjects in the left posterior IPS and right lateral occipital complex, suggesting that these areas specifically house representations of object shape. Haptic shape-selectivity was also found in the left postcentral gyrus, the left lingual gyrus, and a number of frontal cortical sites. Haptic texture-selectivity was found in ventral somatosensory areas: the parietal operculum and posterior insula bilaterally, as well as in the right medial occipital cortex, overlapping with a medial occipital cortical region, which was texture-selective for visual stimuli. The present report corroborates and elaborates previous suggestions of specialized visuo-haptic processing of texture and shape. Hum Brain Mapp 2008. © 2007 Wiley-Liss, Inc. [source]

A comparison of brain activation patterns during covert and overt paced auditory serial addition test tasks

HUMAN BRAIN MAPPING, Issue 6 2008
Cristina Forn
Abstract The Paced Auditory Serial Addition test (PASAT) is a sensitive task for evaluating cognitive impairment in patients with diffuse brain disorders, such as multiple sclerosis patients. Brain areas involved in this task have been investigated in diverse fMRI studies using different methodologies to control the subjects' responses during scanning. Here, we examined the possible differences between overt and covert responses during the PASAT task in 13 volunteers. Results showed similar activations in parietal and frontal brain areas during both versions of the task. The contrast between the two conditions (overt and covert) indicated that differences in these two methodologies were minimal. Unlike the covert condition, the overt version of the task obtained significant activations in the left superior and inferior frontal gyrus, bilateral occipital cortex, caudate nucleus and cerebellum. As expected, no significant overactivations were observed in the covert when compared with the overt condition. Discussion focuses on the lower cost of using verbal responses to monitor performance during the PASAT task, which might be generalisable to other frontal lobe tasks requiring discrete responses. Hum Brain Mapp, 2008. © 2007 Wiley-Liss, Inc. [source]

Enhancement of activity of the primary visual cortex during processing of emotional stimuli as measured with event-related functional near-infrared spectroscopy and event-related potentials

HUMAN BRAIN MAPPING, Issue 1 2008
Martin J. Herrmann
Abstract In this study we investigated whether event-related near-infrared spectroscopy (NIRS) is suitable to measure changes in brain activation of the occipital cortex modulated by the emotional content of the visual stimuli. As we found in a previous pilot study that only positive but not negative stimuli differ from neutral stimuli (with respect to oxygenated haemoglobin), we now measured the event-related EEG potentials and NIRS simultaneously during the same session. Thereby, we could evaluate whether the subjects (n = 16) processed the positive as well as the negative emotional stimuli in a similar way. During the task, the subjects passively viewed positive, negative, and neutral emotional pictures (40 presentations were shown in each category, and pictures were taken from the International Affective Picture System, IAPS). The stimuli were presented for 3 s in a randomized order (with a mean of 3 s interstimulus interval). During the task, we measured the event-related EEG potentials over the electrode positions O1, Oz, O2, and Pz and the changes of oxygenated and deoxygenated haemoglobin by multichannel NIRS over the occipital cortex. The EEG results clearly show an increased early posterior negativity over the occipital cortex for both positive as well as negative stimuli compared to neutral. The results for the NIRS measurement were less clear. Although positive as well as negative stimuli lead to significantly higher decrease in deoxygenated haemoglobin than neutral stimuli, this was not found for the oxygenated haemoglobin. Hum Brain Mapp 29:28,35, 2008. © 2007 Wiley-Liss, Inc. [source]

Using fMRI to dissociate sensory encoding from cognitive evaluation of heat pain intensity

HUMAN BRAIN MAPPING, Issue 9 2006
Jian Kong
Abstract Neuroimaging studies of painful stimuli in humans have identified a network of brain regions that is more extensive than identified previously in electrophysiological and anatomical studies of nociceptive pathways. This extensive network has been described as a pain matrix of brain regions that mediate the many interrelated aspects of conscious processing of nociceptive input such as perception, evaluation, affective response, and emotional memory. We used functional magnetic resonance imaging in healthy human subjects to distinguish brain regions required for pain sensory encoding from those required for cognitive evaluation of pain intensity. The results suggest that conscious cognitive evaluation of pain intensity in the absence of any sensory stimulation activates a network that includes bilateral anterior insular cortex/frontal operculum, dorsal lateral prefrontal cortex, bilateral medial prefrontal cortex/anterior cingulate cortex, right superior parietal cortex, inferior parietal lobule, orbital prefrontal cortex, and left occipital cortex. Increased activity common to both encoding and evaluation was observed in bilateral anterior insula/frontal operculum and medial prefrontal cortex/anterior cingulate cortex. We hypothesize that these two regions play a crucial role in bridging the encoding of pain sensation and the cognitive processing of sensory input. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source]

Neuropathological evidence for ischemia in the white matter of the dorsolateral prefrontal cortex in late-life depression

INTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 1 2003
Alan J. Thomas
Abstract Background Signal hyperintensities on magnetic resonance imaging in late-life depression are associated with treatment resistance and poor outcome. These lesions are probably vascular in origin and proposed sites for vascular damage include the dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC). Methods We therefore examined white matter in these areas for microvascular disease and evidence of ischemia using intercellular adhesion molecule-1 (ICAM-1) and vascular adhesion molecule-1 (VCAM-1). We obtained postmortem tissue from elderly depressed (n,=,20) and control (n,=,20) subjects and blindly rated microvascular disease and ICAM-1 and VCAM-1 amount using quantitative image analysis in sections of the DLPFC, ACC and occipital cortex (OC; control area). Results We found a significant increase in ICAM-1 in the deep white matter of the DLPFC in the depressed group (p,=,0.01) and a trend towards an increase for VCAM-1 (p,=,0.10). In the gyral white matter there was a trend towards significance for both molecules (p,=,0.07 and 0.10). No differences were found in the ACC or OC or for microvascular disease in any area. Conclusions These findings are consistent with white matter ischemia in the DLPFC and lend support to the ,vascular depression' hypothesis. They implicate the DLPFC as an important site in the pathogenesis of late-life depression and have major implications for the understanding and management of late-life depression and raise the possibility of novel treatments being introduced in the future. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Early Postnatal Exposure to Alcohol Reduces the Number of Neurons in the Occipital but Not the Parietal Cortex of the Rat

ALCOHOLISM, Issue 4 2005
Sandra M. Mooney
Background: The rat brain undergoes a period of rapid growth in the early postnatal period. During this time, the neocortex seems to be vulnerable to ethanol injury. Subdivisions of the neocortex develop in a temporospatial gradient that is likely to determine their vulnerability to ethanol-induced damage and whether damage is permanent. Therefore, the authors investigated the effect of postnatal ethanol exposure on the neocortex and specific subregions at the cessation of exposure and in the mature brain. Methods: Four-day-old rat pups with intragastric cannulae were artificially reared from postnatal day (PN) 4 through PN9. Of 12 daily feeds, two consecutive feeds contained either ethanol (4.5 g/kg) or an isocaloric maltose/dextrin solution. On PN10 or PN115, animals were perfused intracardially, and the brains were removed. Stereological methods were used to determine the total number of neurons and glial cells in, and the volume of, the neocortex, the parietal cortex, and the occipital cortex. Results: Exposure to ethanol did not affect body or brain weight at PN10. In contrast, at PN115 forebrain weight was significantly lower in ethanol-exposed animals compared with control-treated animals. There was no effect of treatment on body weight at PN115. On PN10, neocortical volume was 15% smaller in the ethanol-exposed animals compared with controls, with no change in the total number of neurons or glial cells. Occipital cortical volume was reduced by 22% in the ethanol-exposed animals, with a significant deficit in the total number of neurons (ethanol-exposed, 2.62 × 106; gastrostomy control, 3.20 × 106). There was no effect of ethanol exposure on the total number of glial cells in the occipital cortex or on any parameter in the parietal cortex. There was also no significant effect of ethanol exposure on the occipital cortex on PN115. Conclusions: These findings provide support for the hypothesis that a specific area or cell population might be differentially vulnerable to ethanol exposure during the brain growth spurt and that cell deficits evident on PN10 may not be permanent. [source]

Proton spectral editing for discrimination of lactate and threonine 1.31 ppm resonances in human brain in vivo

MAGNETIC RESONANCE IN MEDICINE, Issue 3 2006
Changho Choi
Abstract A single-voxel proton NMR J-difference editing method for discriminating between the 1.31 ppm resonances of lactate (Lac) and threonine (Thr) in human brain in vivo at 3 T is reported. One double-band and two triple-band Gaussian 180° RF pulses, all with a bandwidth of 15 Hz, were employed within an adiabatic-refocused double-echo localization sequence to induce the target signals of Lac and Thr and simultaneously acquire a creatine singlet in each subscan. The optimum echo time and the editing efficiency were obtained by numerical analysis of the filtering performance. The Lac and Thr signals were extracted, without lipid contamination, from three subspectra. Using the calculated yields, the concentrations of Lac and Thr in the human occipital cortex were estimated to be 0.47 ± 0.07 and 0.56 ± 0.06 mM (mean ± SD, N = 7), respectively, with reference to Cr at 8 mM. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source]

Dimension-based attention modulates early visual processing

PSYCHOPHYSIOLOGY, Issue 5 2010
Klaus Gramann
Abstract Target selection can be based on spatial or dimensional/featural mechanisms operating in a location-independent manner. We investigated whether dimension-based attention affects processing in early visual stages. Subjects searched for a singleton target among an 8-item array, with the search display preceded by an identical cue array with a dimensionally non-predictive, but spatially predictive singleton. Reaction times (RTs) were increased for changes in the target-defining dimension but not for featural changes within a dimension. This RT effect was mirrored by modulations of the P1 and anterior transition N2 (tN2). Current density reconstructions revealed increased activity in dorsal occipital cortex and decreased activity in left frontopolar cortex owing to repeated dimensional pop-out identities. These findings strengthen dimension-based theories of visual attention by indicating dimension-, rather than feature-, specific influences within the first 110 ms of visual processing. [source]

Extrastriatal dopaminergic dysfunction in tourette syndrome

ANNALS OF NEUROLOGY, Issue 2 2010
Thomas D. L. Steeves MD
Objective Tourette syndrome (TS) is a neuropsychiatric disorder presenting with tics and a constellation of nonmotor symptoms that includes attention deficit hyperactivity disorder, obsessive,compulsive disorder, and impulse control disorders. Accumulated evidence from pharmacological trials and postmortem analyses suggests that abnormalities of dopaminergic neurotransmission play a key role in the pathogenesis of TS. A substantial body of evidence has also accrued to implicate regions outside the striatum in the generation of tics. Methods We initiated an [11C]FLB 457 positron emission tomography study in conjunction with an amphetamine challenge to evaluate extrastriatal dopamine (DA) D2/D3 receptor binding and DA release in a group of treatment-naive, adult TS patients compared with a group of age- and sex-matched controls. Results At baseline, TS patients showed decreased [11C]FLB 457 binding potentials bilaterally in cortical and subcortical regions outside the striatum, including the cingulate gyrus, middle and superior temporal gyrus, occipital cortex, insula, and thalamus. Amphetamine challenge induced DA release in both control and TS subjects bilaterally in many cortical regions; however, in TS patients, regions of increased DA release were significantly more widespread and extended more anteriorly to involve anterior cingulate and medial frontal gyri. Conversely, and in contrast to healthy controls, no significant DA release was noted in the thalami of TS patients. Interpretation These abnormalities of dopaminergic function localize to brain regions previously implicated in TS and suggest a mechanism for the hyperexcitability of thalamocortical circuits that has been documented in the disorder. ANN NEUROL 2010;67:170,181 [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]

Historical perspective: Neurological advances from studies of war injuries and illnesses,

ANNALS OF NEUROLOGY, Issue 4 2009
Douglas J. Lanska MD
Early in the 20th century during the Russo-Japanese War and World War I (WWI), some of the most important, lasting contributions to clinical neurology were descriptive clinical studies, especially those concerning war-related peripheral nerve disorders (eg, Hoffmann-Tinel sign, Guillain-Barré-Strohl syndrome [GBS]) and occipital bullet wounds (eg, the retinal projection on the cortex by Inouye and later by Holmes and Lister, and the functional partitioning of visual processes in the occipital cortex by Riddoch), but there were also other important descriptive studies concerning war-related aphasia, cerebellar injuries, and spinal cord injuries (eg, cerebellar injuries by Holmes, and autonomic dysreflexia by Head and Riddoch). Later progress, during and shortly after World War II (WWII), included major progress in understanding the pathophysiology of traumatic brain injuries by Denny-Brown, Russell, and Holbourn, pioneering accident injury studies by Cairns and Holbourn, promulgation of helmets to prevent motorcycle injuries by Cairns, development of comprehensive multidisciplinary neurorehabilitation by Rusk, and development of spinal cord injury care by Munro, Guttman, and Bors. These studies and developments were possible only because of the large number of cases that allowed individual physicians the opportunity to collect, collate, and synthesize observations of numerous cases in a short span of time. Such studies also required dedicated, disciplined, and knowledgeable investigators who made the most out of their opportunities to systematically assess large numbers of seriously ill and injured soldiers under stressful and often overtly dangerous situations. Ann Neurol 2009;66:444,459 [source]

Alzheimer's disease versus dementia with Lewy bodies: Cerebral metabolic distinction with autopsy confirmation

ANNALS OF NEUROLOGY, Issue 3 2001
Satoshi Minoshima MD
Seeking antemortem markers to distinguish Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD), we examined brain glucose metabolism of DLB and AD. Eleven DLB patients (7 Lewy body variant of AD [LBVAD] and 4 pure diffuse Lewy body disease [DLBD]) who had antemortem position emission tomography imaging and autopsy confirmation were compared to 10 autopsy-confirmed pure AD patients. In addition, 53 patients with clinically-diagnosed probable AD, 13 of whom later fulfilled clinical diagnoses of DLB, were examined. Autopsy-confirmed AD and DLB patients showed significant metabolic reductions involving parietotemporal association, posterior cingulate, and frontal association cortices. Only DLB patients showed significant metabolic reductions in the occipital cortex, particularly in the primary visual cortex (LBVAD ,23% and DLBD ,29% vs AD ,8%), which distinguished DLB versus AD with 90% sensitivity and 80% specificity. Multivariate analysis revealed that occipital metabolic changes in DLB were independent from those in the adjacent parietotemporal cortices. Analysis of clinically-diagnosed probable AD patients showed a significantly higher frequency of primary visual metabolic reduction among patients who fulfilled later clinical criteria for DLB. In these patients, occipital hypometabolism preceded some clinical features of DLB. Occipital hypometabolism is a potential antemortem marker to distinguish DLB versus AD. [source]

Relative increase in choline in the occipital cortex in chronic fatigue syndrome

MM2-cortical-type sporadic Creutzfeldt-Jakob disease with early stage cerebral cortical pathology presenting with a rapidly progressive clinical course

NEUROPATHOLOGY, Issue 6 2008
Yoshiki Niimi
We report the case of a 67-year-old man with MM2-cortical-type sporadic Creutzfeldt-Jakob disease (sCJD) with a rapidly progressive clinical course of 5 months. Initial symptoms were progressive memory disturbance and dementia. MRI revealed high signal-intensity lesions on diffusion-weighted images in the bilateral frontal and occipital cortices. Myoclonus and periodic sharp-wave complexes on the electroencephalogram were observed in the early disease stage. The clinical diagnosis was typical sCJD. Neuropathologic examination at autopsy showed widespread, characteristic cerebral neocortical involvement with large confluent vacuole-type spongiform change. Spongiform degeneration was also evident in the striatum and medial thalamus. In the cerebellar cortex, slight depletion of Purkinje neurons was evident without spongiform change in the molecular layer or apparent neuron loss in the granule cell layer. The inferior olivary nucleus showed slight hypertrophic astrocytosis without neuron loss. Prion protein (PrP) immunostaining showed widespread, characteristic perivacuolar-type PrP deposits with irregular plaque-like PrP deposits in the cerebral neocortex, striatum and medial thalamus. We believe this patient showed early-stage cerebral cortical pathology of MM2-cortical-type sCJD, which may provide clues regarding the pathologic progression of this rare sCJD subtype. Although MM2-cortical-type sCJD generally shows slow progression without myoclonus or periodic sharp-wave complexes, the present patient showed a rapidly progressive clinical course similar to that of MM1-type sCJD. [source]

Pick's disease with Pick bodies: An unusual autopsy case showing degeneration of the pontine nucleus, dentate nucleus, Clarke's column, and lower motor neuron

NEUROPATHOLOGY, Issue 1 2007
Tatsuro Oda
We report a 51-year-old female with Pick's disease with Pick bodies (PDPB) showing a brainweight of 530 g. This case was considered to be a very rare case of PDPB, in which the lesion developed in the temporal and frontal lobes and later spread to the parietal lobe, occipital lobe, brainstem, cerebellum and spinal cord. This case showed very atypical clinicopathological findings. Clinically, bulging eyes and myoclonus were observed. Neuropathologically, Pick bodies were widely distributed beyond the usual distribution areas to the parietal cortices, occipital cortices, dentate nuclei, motor neuron nuclei in the brain stem, and spinal cord. The atypical clinical symptoms and the widespread neuropathological abnormalities observed in this case seem to represent an extremely extended form of PDPB. [source]

Fleeting images: A new look at early emotion discrimination

PSYCHOPHYSIOLOGY, Issue 2 2001
Markus Junghöfer
The visual brain quickly sorted stimuli for emotional impact despite high-speed presentation (3 or 5 per s) in a sustained, serial torrent of 700 complex pictures. Event-related potentials, recorded with a dense electrode array, showed selective discrimination of emotionally arousing stimuli from less affective content. Primary sources of this activation were over the occipital cortices, extending to right parietal cortex, suggesting a processing focus in the posterior visual system. Emotion discrimination was independent of formal pictorial properties (color, brightness, spatial frequency, and complexity). The data support the hypothesis of a very short-term conceptual memory store (M. C. Potter, 1999),shown here to include a fleeting but reliable assessment of affective meaning. [source]