Sex differences in brain regions activated by grammatical and reading tasks

Do the brains of men and women show similar patterns of functional organization for language, or are men more strongly lateralized? We used PET to measure cerebral blood flow (CBF) as men and women read real and nonce verbs, and produced past tense forms. While the overall patterns of reaction time, error, and brain activation were similar, there were also significant sex-related differences in CBF patterns. During the past tense generation tasks, men showed left-lateralized activation while women recruited bilateral perisylvian cortex, confirming differences in functional laterality. During all tasks, women showed higher activation in occipital and/or cerebellar regions, suggesting differences in basic reading strategies. We conclude that sex differences in functional cortical organization exist in the absence of significant behavioral differences.     

The human pulvinar and stimulus-driven attentional control.

The present study compared the behavioral effects of sudden motion onsets or color changes (i.e., featural changes) with the effects of new objects (i.e., multiple changes). Experiments 1 and 2 showed that lesions of the pulvinar affect stimulus-driven attentional control only when it is triggered by featural changes, but not by new objects. Experiment 3 revealed that when appended on a new object, a featural change is processed as a part of a more massive new object: Its attentional effects are larger and remain undisturbed by lesions of the pulvinar. In Experiment 4 a temporal superiority effect was found for featural changes, but not for new objects in healthy subjects. These results suggest that featural changes and new objects may be processed through different pathways and that the pulvinar may be particularly involved in stimulus-driven attentional control by sudden events entailing featural changes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immunogenetics and the cause of autoimmune disease

Up until recently, neurology was dominated by localisatory thinking. Language and other so-called "centers" were considered to be centers of command controlling the respective functions. Today, there is general agreement that, instead, for every brain function numerous brain regions must act together. For the exploration of these manifold topographic cooperations produced by cognitive tasks, coherence of long-term EEG periods proved to be a proficient parameter for the representation of functionally essential connections. Because of the unequivocal meaningfulness of absolute coherence values, instead, only the signs of significant differences between coherence values during cognitive tasks and periods of EEG at rest before and after the task were considered for all possible electrode pairings and charted on schematic maps of the brain. In addition, the signs of significant changes of amplitude were entered. This procedure was performed for each of 6 frequency bands and for the 19 electrodes of the 10/20 system, thus yielding 171 possible plus or minus values for coherence and 19 for amplitude, respectively. The positions of the electrodes were marked by an MRI contrast medium. After the EEG, MRI examination was performed. The MRI data were segmented and the cortex was mapped onto a plane using a method similar to cartography. The exact electrode positions are registered from a similarly obtained map of the scalp and the electrode position pattern is used as basis for the coherence graphs. A detailed map of the cortex based on the segmented MRI data with the electrode positions marked is provided as a reference enabling allocation of the electrodes to the cortical structures. The usefulness of this procedure is demonstrated with a single subject by means of different cognitive tasks including musical thinking.     

Age and individual differences in prospective memory during a "Virtual Week": The roles of working memory, vigilance, task regularity, and cue focality.

Young (ages 18–22 years) and older (ages 61–87 years) adults (N = 106) played the Virtual Week board game, which involves simulating common prospective memory (PM) tasks of everyday life (e.g., taking medication), and performed working memory (WM) and vigilance tasks. The Virtual Week game includes regular (repeated) and irregular (nonrepeated) PM tasks with cues that are either more or less focal to other ongoing activities. Age differences in PM were reduced for repeated tasks, and performance improved over the course of the week, suggesting retrieval was more spontaneous or habitual. Correlations with WM within each age group were reduced for PM tasks that had more regular or focal cues. WM (but not vigilance) ability was a strong predictor of irregular PM tasks with less focal cues. Taken together, these results support the hypothesis that habitual and focally cued PM tasks are less demanding of attentional resources (specifically, WM), whereas tasks that are more demanding of controlled attentional processes produce larger age differences, which may be attributable to individual differences in WM. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rational diagnosis and surgical therapy of renal cell carcinoma with tumor thrombosis in the vena cava

Cerebral blood flow (CBF) rises when the glucose supply to the brain is limited by hypoglycemia or glucose metabolism is inhibited by pharmacological doses of 2-deoxyglucose (DG). The present studies in unanesthetized rats with insulin-induced hypoglycemia show that the increases in CBF, measured with the [14C]iodoantipyrine method, are relatively small until arterial plasma glucose levels fall to 2.5 to 3.0 mM, at which point CBF rises sharply. A direct effect of insulin on CBF was excluded; insulin administered under euglycemic conditions maintained by glucose injections had no effects on CBF. Insulin administration raised plasma lactate levels and decreased plasma K+ and HCO3- concentrations and arterial pH. These could not, however, be related to the increased CBF because insulin under euglycemic conditions had similar effects without affecting CBF; furthermore, the inhibition of brain glucose metabolism with pharmacological doses (200 mg/kg intravenously) of DG increased CBF, just like insulin hypoglycemia, without altering plasma lactate and K+ levels and arterial blood gas tensions and pH. Nitric oxide also does not appear to mediate the increases in CBF. Chronic blockade of nitric oxide synthase activity by twice daily i.p. injections of NG-nitro-L-arginine methyl ester for 4 days or acutely by a single i.v. injection raised arterial blood pressure and lowered CBF in normoglycemic, hypoglycemic, and DG-treated rats but did not significantly reduce the increases in CBF due to insulin-induced hypoglycemia (arterial plasma glucose levels, 2.5-3 mM) or pharmacological doses of deoxyglucose.     

Effect of kanji and kana reading on cerebral blood flow patterns measured by PET

To investigate the respective functions of pathways in processing visual information from different types of symbols, by positron emission tomography (PET) we examined the effect on cerebral blood flow (CBF) of reading the Japanese morphogram (kanji) versus the syllabogram (kana). Nine Japanese men were presented with three visual conditions in random order 2 minutes before the scan: eyes open controls, kanji morphogram reading, and kana syllabogram reading. Three words written in kanji or kana were shown, and subjects were instructed to read them silently and to identify the word unrelated logically to the other two. The reading and analyzing tasks activated wide areas of vision-related cortices. The comparison of the kanji and kana readings showed higher metabolism, with the former only in the posterior part of the primary visual cortex. Most of the CBF increases were common for both stimuli, although the patterns of these increases differed slightly. The correlation matrix of CBF change in the left hemisphere showed a ventral connection in kanji reading and a dorsal connection in kana reading. Our results suggest there is a functional differentiation in the brain between patterned and sequential perception when reading Japanese morphograms and syllabograms.     

Conceptual processing during the conscious resting state. A functional MRI study

Localized, task-induced decreases in cerebral blood flow are a frequent finding in functional brain imaging research but remain poorly understood. One account of these phenomena postulates processes ongoing during conscious, resting states that are interrupted or inhibited by task performance. Psychological evidence suggests that conscious humans are engaged almost continuously in adaptive processes involving semantic knowledge retrieval, representation in awareness, and directed manipulation of represented knowledge for organization, problem-solving, and planning. If interruption of such 'conceptual' processes accounts for task-induced deactivation, tasks that also engage these conceptual processes should not cause deactivation. Furthermore, comparisons between conceptual and nonconceptual tasks should show activation during conceptual tasks of the same brain areas that are 'deactivated' relative to rest. To test this model, functional magnetic resonance imaging data were acquired during a resting state, a perceptual task, and a semantic retrieval task. A network of left-hemisphere polymodal cortical regions showed higher signal values during the resting state than during the perceptual task but equal values during the resting and semantic conditions. This result is consistent with the proposal that perceptual tasks interrupt processes ongoing during rest that involve many of the same brain areas engaged during semantic retrieval. As further evidence for this model, the same network of brain areas was activated in two direct comparisons between semantic and perceptual processing tasks. This same 'conceptual processing' network was also identified in several previous studies that contrasted semantic and perceptual tasks or resting and active states. The model proposed here offers a unified account of these findings and may help to explain several unanticipated results from prior studies of semantic processing.     

Color functional images of the cerebral blood flow

Functional gamma imaging, in color, was established for regional cerebral blood flow (rCBF) using 133Xe. During 10 min after intracarotid injection of 133Xe in saline, 60 picture frames of the 133Xe clearance curve for the entire hemisphere were obtained. After nine-point smoothing, the rCBF for each of the 4,096 picture elements was calculated by two methods: the half-time method and the height-over-area method. Both the 133Xe clearance half-times and the calculated CBF values were displayed, using 13 steps of color, as functional CBF images of the brain. Images of peak count and total count were also displayed on the same frame of the color television. Forty-six studies, performed on 37 patients with various cerebral disorders, were divided into two types: diffuse and focal. In the diffuse type, a decrease in CBF was noted in cases of normal-pressure hydrocephalus; successful ventriculoperitoneal shunt operations were followed by recovery of CBF. Occlusion of the middle cerebral artery showed up as a wedge-shaped area of decreased CBF, even when the conventional brain scan looked normal. Increased perfusion to a tumor was frequently associated with decreased CBF in the rest of the lateral hemisphere; such a decrease could be improved by surgical removal of the tumor.     

Important points in therapy of pulmonary tuberculosis and atypical mycobacterium respiratory infections

PURPOSE: Our goal was to elucidate the temporal profile of cerebral circulation and its relationship to prognosis in patients with diffuse brain injury by using single-photon emission CT (SPECT) and 123I-iodoamphetamine (IMP). METHODS: A total of 67 assessments were made in 26 patients with diffuse brain injury (Glasgow Coma Scale score < or = 8). The microsphere method was used for quantifying cerebral blood flow (CBF). The hemispheric CBF was defined as a mean regional CBF (rCBF), and the total cerebral hemispheric CBF (tCBF) as a mean of the bilateral hemispheric CBF. The relationship between patient outcome and tCBF was investigated. RESULTS: The rCBF in patients with diffuse brain injury showed dynamic and global changes with little regional differences. The tCBF values increased in 1 to 3 days, and they were higher in the poor-outcome group than in the good-outcome group. During the period of 14 to 42 days, the tCBF values stayed within normal range in the good-outcome group, whereas they were below normal range in the poor-outcome group. CONCLUSION: Our results revealed a good correlation between patient outcome and CBF values. Quantitative and sequential CBF studies with IMP SPECT are promising for helping to determine the prognosis for patients with diffuse brain injury.     

Losses in gross brain volume and cerebral blood flow account for age-related differences in speed but not in fluid intelligence.

Age-related gross head size; adjusted age-related change in brain volume and carotid and basilar blood flow; as well as scores on 3 tests of fluid intelligence (gf), 2 tests of information-processing speed, 2 memory tests, and 3 tests of executive function were obtained from 69 volunteers aged from 62 to 84 years. Brain volume negatively predicted scores on all 10 cognitive tasks, accounting for up to 78% of age-related variance in scores on the speed tasks and on 1 executive task. Cerebral blood flow (CBF) negatively predicted scores on 8 cognitive tasks, accounting for up to 36% of age-related variance in speed scores. However, neither brain volume nor CBF accounted for significant age-related variance between individuals on any of 3 gf tests. We conclude that speed, but not gf, is an exceptionally sensitive behavioral index of the progress of gross brain changes that affect cognition in old age and that speed and gf do not reflect integrity of the same functional systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in skill learning: An integration of psychometric and information processing perspectives.

Reexamines the nature of individual differences in novel and practiced performance on skill learning tasks from an information processing framework. Two major sources of data and discussion are reanalyzed and critically evaluated. One source concerns the changes in interindividual between-subjects variability with task practice; the other pertains to associations between intellectual abilities and task performance during skill acquisition. Early studies yielded mixed results regarding the convergence or divergence of individual differences with practice. Other studies indicated small or trivial correlations between individual differences in intelligence and "gain" scores. More recent studies indicated small correlations between performance measures on skill learning tasks and standard intellectual and cognitive ability measures, as well as increasing amounts of task-specific variance over learning trials. Data confirm the proposition that individuals converge on performance as tasks become less dependent on attentional resources with practice. When appropriate methodological techniques are used and crucial task characteristics are taken into account, intellectual abilities play a substantial part in determining individual differences in skill learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correlation of cerebral blood flow with outcome in head injured patients

In order to determine the relationship of cerebral blood flow (CBF) to the clinical outcome of head injury, serial determinations of CBF were performed by the intravenous Xenon technique in 24 patients. The patients were of mixed injury severity and were classified into four groups depending on the neurological exam at the time of each CBF study. All eight patients who were lethargic on admission demonstrated increases in their minimally depressed CBF as they improved to normal status. Eleven patients in deep stupor or coma ultimately recovered. Ten of these patients initially had moderate to profound decreases in CBF which improved as recovery occurred. The single exception was an adolescent whose initial CBF was high but became normal at recovery. Five comatose patients died. In four of these, already depressed CBF fell even lower, while one adolescent with initially increased CBF developed very low CBF preterminally. The data presented in this report demonstrated a good correlation between CBF and clinical outcome. In every one of the adult survivors, depressed CBF increased as the patient recovered to normal status. All adults who died showed a deterioration of CBF as the neurological status worsened. The only exceptions were two adolescents who initially showed high CBF values. In the adolescent who died, CBF dropped to low levels while in the survivor a normal CBF was achieved. Thus in adults a traumatic brain injury was associated with depressed CBF which increased with recovery or decreased further with deterioration while the reaction to injury was quite different in the younger brain.     

Cerebral blood flow and the response to acetazolamide during the acute, subacute, and chronic stages of aneurysmal subarachnoid hemorrhage

Cerebral blood flow (CBF) and response to acetazolamide were measured during the acute, subacute, and chronic stages after aneurysmal subarachnoid hemorrhage and correlated with symptomatic vasospasm and clinical outcome in 45 patients who underwent early clipping of ruptured cerebral aneurysms, of whom 18 had symptomatic vasospasm and 27 did not. Xenon-enhanced computed tomography was used to measure CBF in both groups during the acute, subacute, and chronic stages, defined as days 0-4, 5-20, and > or = 21, respectively. Vasoresponse was assessed by the CBF increase in response to 1 g of acetazolamide administered after the baseline CBF study, except in the subacute stage of patients with symptomatic vasospasm. Outcome was scored based on activities of daily living 2-3 months after subarachnoid hemorrhage. CBF values and the response to acetazolamide were preserved during the acute stage but CBF values fell considerably below control values during the subacute stage in patients with vasospasm. The regions with flow values below 15 ml/100 g/min subsequently converted to infarction and the regions with those above 19 ml/100 g/min remained intact without infarction. During the chronic stage, low CBF persisted, but the response to acetazolamide was higher than that of the control group. Outcome scores were good and fair. CBF values were normal during all stages in patients without vasospasm. The response to acetazolamide fell transiently during the subacute stage. All outcome scores were excellent. In conclusion, the CBF informations soon after the onset of symptomatic vasospasm are useful to predict a reversibility of ischemic brain tissue and a final outcome. We suggest that vasospasm may cause a pathological or ischemic insult to brain tissue during the subacute stage, and the brain may remain metabolically depressed thereafter, leading to a poor outcome. Even clinically asymptomatic patients may suffer mildly vasospastic or ischemic conditions during the subacute stage.     

A possible visual pathway to the cat caudate nucleus involving the pulvinar

Electrical stimulation of the thalamic nucleus pulvinar was found to influence unit activity in the feline caudate nucleus. Twenty-six (18.3%) units were encountered, in this subcortical region of the brain, that responded to activation of the pulvinar input in anesthetized cats and 41 (54%) in awake animals. In the two types of experiments, stimulation of the pulvinar induced mainly an initial excitatory reaction (81% and 78% of responsive cells, respectively). A latency analysis indicated that the majority of responses occurred at a long latency, while 9 (34.6%) cells in anesthetized cats and 5 (12%) in awake animals were excited at a short latency. The short latency is compatible with the involvement of a monosynaptic pathway between the pulvinar and the caudate nucleus. Units that responded to thalamic stimulation were found predominantly in the posterior regions of the caudate nucleus. These results confirm previous neuroanatomical findings of a direct projection from the pulvinar to the feline caudate nucleus. In awake animals, neurons activated by pulvinar stimulation were also tested, using visual stimuli of various orientations. Out of 41 units, 63% were classified as having "visual responses". Of these, 5 cells were found to respond selectively to a particular orientation of the visual stimulus. Three of these were excited at a short latency by pulvinar stimulation. The possible involvement of a direct pathway from the pulvinar to the caudate nucleus in the processing of visual information is discussed.     

Perinatal choline supplementation improves cognitive functioning and emotion regulation in the Ts65Dn mouse model of Down syndrome.

In addition to mental retardation, individuals with Down syndrome (DS) also develop the neuropathological changes typical of Alzheimer's disease (AD) and the majority of these individuals exhibit dementia. The Ts65Dn mouse model of DS exhibits key features of these disorders, including early degeneration of cholinergic basal forebrain (CBF) neurons and impairments in functions dependent on the two CBF projection systems; namely, attention and explicit memory. Herein, we demonstrate that supplementing the maternal diet with excess choline during pregnancy and lactation dramatically improved attentional function of the adult trisomic offspring. Specifically, the adult offspring of choline-supplemented Ts65Dn dams performed significantly better than unsupplemented Ts65Dn mice on a series of 5 visual attention tasks, and in fact, on some tasks did not differ from the normosomic (2N) controls. A second area of dysfunction in the trisomic animals, heightened reactivity to committing an error, was partially normalized by the early choline supplementation. The 2N littermates also benefited from increased maternal choline intake on 1 attention task. These findings collectively suggest that perinatal choline supplementation might significantly lessen cognitive dysfunction in DS and reduce cognitive decline in related neurodegenerative disorders such as AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Backbone mutations in transmembrane domains of a ligand-gated ion channel: implications for the mechanism of gating

The relationship between regional parenchymal cerebral blood volume (CBV), regional cerebral blood flow (CBF) and the calculated mean transit time (MTT) was investigated in 14 newborn piglets. The effects of combined hypoxic hypoxia (PaO2 = 32 +/- 5 mm Hg) and hypercapnia (paCO2 = 68 +/- 5 mm Hg) were measured in seven animals. Remaining animals served as the control group. During baseline conditions the highest CBF and CVB values were found in the lower brainstem and cerebellum, whereas white matter exhibited the lowest values (p < 0.05). MTT was prolonged within the cerebral cortex (2.34 +/- 0.42 s-1) compared with the thalamic MTT (1.53 +/- 0.38 s-1) (p < 0.05). Under moderate hypoxia/hypercapnia, a CBF increase to the forebrain (p < 0.05) resulted in an elevated brain oxygen delivery (p < 0.05) and so CMRO2 remained unchanged. Moreover, a moderate increase of CBV and a marked shortening of MTT occurred (p < 0.05). The CBV increase was higher in structures with lowest baseline values, i.e., thalamus (66% increase) and white matter (62% increase) (p < 0.05). MTT was between 22% of baseline in the lower brainstem and 49% in white matter (p < 0.05). We conclude that under normoxic and normocapnic conditions the newborn piglets exhibit a comparatively enlarged intraparenchymal CBV. Moderate hypoxia and hypercapnia induced a marked increase in cerebral blood flow which appears to be caused by an increased perfusion velocity, expressed by a strongly reduced mean transit time and by a concomitant CBV increase.     

Some relationships between skills in word-category recall and factors in adults' aphasia

It has long been recognized that a basic dimension to the lexical organization of the brain is semantic, and some brain mapping studies have indicated that the brain fields are distinctly different from some grammatical classes. Findings from the present investigation showed consistent relationships between 29 aphasic adults' performances on tasks involving graphic and gestural skills and those involving sequential recall of spoken words from different word categories. Each adult received the Porch Index of Communication Abilities which relies upon the physical manipulation of objects to assess verbal, gestural, and graphic abilities. Scores on a test requiring recall of word strings of nouns, verbs, adverbs, adjectives, or prepositions were used to predict the subscale scores from the Graphic and Gestural factors of the index. Recall scores for verb and preposition were predictive of the aphasic subjects' performances on the Graphic subscale, and noun and preposition scores were predictors of subjects' scores on the Gestural subscale. The results are related to other research showing that verb and preposition skills are predictive of fine motor abilities of children with communication disorders and brain-mapping studies. Some discussion centers on possible overlapping functions of brain activity involving word categories, language, and fine motor skills.     

Young children learn to produce passives with nonce verbs

Younger and older children (mean ages = 2 years 11 months and 3 years 5 months) learned 2 nonce verbs in a full passive or active transitive construction. When asked patient-focused questions encouraging passive-voice replies (e.g., "What happened to the ball?") or agent-focused questions encouraging active-voice replies (e.g., "What did Elmo do?"), children used a variety of strategies to meet the demands of the questions, usually without changing the construction in which the verb occurred. In Study 2 in which passive and active constructions were primed, 40% of the almost 3-year-old children used an active-introduced verb in a passive construction and 35% used a passive-introduced verb in an active transitive construction when discourse demands encouraged them to do so. Thus, before their 3rd birthdays, some children have an understanding of the passive and active transitive constructions general enough to support productive usages with newly learned verbs.     

Quantitative cerebral blood flow and metabolism determination in the first 48 hours after severe head injury with a new dynamic SPECT device

OBJECTIVE: To determine cerebral blood flow (CBF) and metabolism in the acute phase after severe head injury by a new dynamic SPECT device using 133Xenon and to evaluate a possible role of CBF and metabolism in the determination of prognosis. DESIGN: Prospective study. SETTING: General intensive care unit in a universitary teaching hospital. SUBJECTS: 23 severely head injured patients having CT scan and CBF determination, intracranial pressure (ICP) and jugular bulb oxygen saturation monitoring in the first 48 hours. MEASUREMENTS AND MAIN RESULTS: CBF varied from 18.0 to 60.0 ml/100 g/min. No correlation was found between early CBF and severity of trauma evaluated with the Glasgow Coma Score (GCS) (F = 2.151, p = 0.142) and between CBF and prognosis at 6 months evaluated with Glasgow outcome score (GOS) (F = 0.491, p = 0.622: rs = 0.251, p = 0.246). CMRO2 was depressed in relation to the severity of injury, specifically ranging from 0.9 +/- 0.5 ml/100 g/min in patients with GCS 3 to 1.7 +/- 0.8 ml/100 g/min in patients with GCS 6-7. In no patient with CMRO2 less than 0.8 ml/100 g/min was a good outcome observed. A significant correlation was found between GCS and GOS (rs = 0.699, p = 0.0002), between CMRO2 and GOS (F = 4.303, p = 0.031; rs = 0.525, p = 0.013) and between AJDO2 and GOS (F = 3.602, p = 0.046; rs = 0.491, p = 0.017). Fronto-occipital ratio (F/O) of CBF distribution was significantly lower than normal values (chi 2 = 18.658, p = 0.001) but did not correlate either with prognosis (chi 2 = 1.626, p = 0.443) or with severity (chi 2 = 1.913, p = 0.384). CONCLUSIONS: CBF in the first 48 hours after trauma varies within a large range of values and is not correlated with severity and prognosis. Clinical evaluation with GCS and CMRO2 are much more reliable indicators of severity of head trauma and have a significant role in the determination of prognosis. F/O ration is significantly altered from normal values confirming "post-traumatic hypofrontalism" but does not correlate with severity and prognosis.     

Visuospatial neglect: the ultimate deconstruction?

Unilateral visuospatial neglect is now widely acknowledged to be a highly heterogeneous condition: The overt manifestations of visual neglect can vary as a function of task, spatial domain, and mode of response (at least). Double dissociations (sometimes of the strong form) have already been reported between most of the components of what was originally thought to be a relatively stable construct within the visual modality. Nonetheless, throughout successive fractionations of neglect, reported cases of bidirectional task-specific neglect after unilateral brain damage are rare. We now report two such cases. After right hemisphere stroke, the first patient reliably showed severe left neglect on cancellation but right neglect on line bisection. After left hemisphere stroke, the second case showed right neglect on cancellation but left neglect on line bisection. Extensive investigation of case 1 confirmed our previous conjecture that the crucial distinction between these tasks lies in the presence or the absence of an overt target. In contrast to cancellation, line bisection demands the internal computation of the location of the "target" (the midpoint), followed by executing a motor response toward the precise location of that "imaginary" midpoint. The relative attentional and premotor contributions of the intact and damaged hemispheres to these forms of bidirectional neglect are also assessed.