Circumscribed low grade astrocytomas in the dominant opercular and insular region: A pilot study

Summary Intraoperative mapping techniques allow a reliable identification or exclusion of eloquent brain areas and are well tolerated by the patients. In dominant opercular tumours radical surgery can only be achieved without lasting deficits with intraoperative histological examination of the resection line and mapping. If an early post-operative MRI shows residual opercular tumour in non-eloquent areas re-operation is recommended.In large dominant insular or opercular-insular tumours only biopsy is recommended, because only an incomplete removal can be accomplished, because the trial of radical removal carries a high risk of postoperative deficits due to possible vascular damage of the lenticulo-striate arteries or internal capsule. Because subtotal removal of low grade gliomas does not increase the progression free interval, we would not recommend surgery in these cases, as they carry a significant risk of a further deficit.     

An integrative psychophysiological approach to brain hemisphere functions in schizophrenia

The present paper proposes a new psychophysiological approach to the genesis of positive and negative schizophrenic symptoms. According to this approach, the initial factor in schizophrenic disorders is a functional insufficiency of the right hemisphere which can be determined by early emotional experience in combination with subtle brain damage. This functional insufficiency causes (a) the inability to grasp and select information before its realization; and (b) the inability to produce a polysemantic context which is crucial for creativity, psychological defense, and the restoration of search activity, all of which determine psychophysiological adaptation to the environment. Right hemisphere insufficiency causes left hemisphere hyperactivity as an ineffective attempt to compensate for this functional deficiency. As a result, normal search activity is replaced by artificial search activity which is represented by “positive” symptoms, and which uses the predisposition of the left hemisphere's catecholamine system for its increased activity. The suggestion is made that cognitive impairment in schizophrenia (the inability to use appropriate previous information in relation to current perceptual input) is related to the competition between information processing which requires left hemisphere activity, and the formation of positive symptoms, also based on left hemisphere activity.     

磁共振波谱评价大脑半球代谢物的偏侧优势

为了利用无创性的磁共振波谱成像技术研究大脑半球代谢物的非对称性,本研究对56例正常成年人行磁共振波谱成像,主要对双侧大脑半球的4个解剖区域:额叶、颞叶、枕叶及顶叶的代谢物天门冬氨酸(NAA)、肌酸(Cr)、胆碱(Cho)进行测量,并以Cr为内参照物比较NAA和Cho相对含量(NAA/Cr、Cho/Cr)的侧别差异。结果表明:双侧额叶之间的NAA/Cr存在显著性差异,而Cho/Cr无显著性差异;在双侧颞叶之间,这2种比值均存在显著性差异;双侧枕叶之间Cho/Cr存在显著性差异,而NAA/Cr无显著性差异;双侧顶叶之间的NAA/Cr存在显著性差异,而Cho/Cr无显著性差异。本研究结果提示双侧大脑半球的代谢物存在偏侧优势。     

The effects of competition and motor reprogramming on visuomotor selection in unilateral neglect

Patients with unilateral neglect following right hemisphere damage may have difficulty in moving towards contralesional targets. To test the hypothesis that this impairment arises from competing motor programs triggered by irrelevant ipsilesional stimuli, we examined 16 right hemisphere patients, eight with left visual neglect and eight without, in addition to eight healthy control subjects. In experiment 1 subjects performed sequences of movements using their right hand to targets on the contralesional or ipsilesional side of the responding limb. The locations of successive targets in each sequence were either predictable or unpredictable. In separate blocks of trials, targets appeared either alone or with a simultaneous distractor located at the immediately preceding target location. Neglect patients were significantly slower to execute movements to contralesional targets, but only for unpredictable movements and in the presence of a concurrent ipsilesional distractor. In contrast, healthy controls and right hemisphere patients without neglect showed no directional asymmetries of movement execution. In experiment 2 subjects were required to interrupt a predictable, reciprocating sequence of leftward and rightward movements in order to move to an occasional, unpredictable target that occurred either in the direction opposite to that expected, or in the same direction but twice the extent. Neglect patients were significantly slower in reprogramming the direction and extent of movements towards contralesional versus ipsilesional targets, and they also made significantly more errors when executing such movements. Right hemisphere patients without neglect showed a similar bias in reprogramming direction (but not extent) for contralesional targets, whereas healthy controls showed no directional asymmetry in either condition. On the basis of these findings we propose that neglect involves a competitive bias in favour of motor programs for actions directed towards ipsilesional versus contralesional events. We suggest that programming errors and increased latencies for contralesional movements arise because the damaged right hemisphere can no longer effectively inhibit the release of inappropriate motor programs towards ipsilesional events. Received: 1 October 1996 / Accepted: 21 October 1997     

Dreaming in agenesis of the corpus callosum: laboratory and home assessment of four cases

Laboratory and home dream recall was studied in four subjects with agenesis of the corpus callosum and in four control subjects who were matched for age, gender, and handedness. In addition, the structural and emotional content of home dreams was compared for these two groups. Results indicate that acallosal subjects recalled fewer dreams in the laboratory than did control subjects, but recalled the same number of dreams at home. They also reported more contentless dreams in both situations. Furthermore, although acallosal subjects used fewer words to describe their dream content in both contexts, the number of content categories they reported differed little from the number reported by control subjects. However, some trends were found for acallosal's home dreams to differ from those of controls, i.e. more dreams with known characters and fewer dreams with unknown characters, animals, and colours. Differences in emotional contents were few; acallosals reported more distress than controls. The shorter length of acallosals' dreams might be explained, in part, by their lower verbal IQs. Other characteristics of dream content (e.g. more distress, fewer dreams with unknown and animal characters) may reflect limited social experiences in this group. However, the greater frequency of contentless dreams and the lower frequency of dreams with colour are trends consistent with the possibility that the corpus callosum may be implicated in processes of dream production and dream recall.     

Kissing laterality and handedness

Kissing behaviour was observed between kissing couples: about 80% turned their heads to the right to kiss. To remove the influence of one kissing partner upon the other, kissing behaviour was also observed between participants and a symmetrical doll's face: about 77% turned their heads to the right to kiss. There was no significant difference in handedness between right- and left-kissers: both groups were predominantly right-kissers. It is thought that motor bias rather than emotive bias influences kissing behaviour.     

Theory of mind impairment in right hemisphere damage: A review of the evidence

Among the hypothesized causes of communication impairments in people with damage to the right cerebral hemisphere (RHD) is an underlying impairment in Theory of Mind (ToM) (the ability to make inferences about other peoples' mental states). In this review, evidence is considered for a ToM impairment in adults with RHD by approaching the issue from two directions. First, indirect evidence for impairment of ToM is reviewed by looking at studies on the effects of RHD on the comprehension of indirect requests, that is, requests in which the speaker's wishes are not explicitly stated but must be inferred by the listener. Second, studies that directly investigate the effects of RHD on performance on tasks intended to tap ToM are reviewed. On the basis of the papers reviewed here, it is concluded that although people with RHD do show impairments on a variety of tasks that are thought to involve ToM cognition, evidence for a specific ToM impairment is still inconclusive. It is recommended that future studies take care to distinguish individual differences in participants' linguistic production and lesion location, that more care is taken to control for task difficulty, and that well-controlled studies are combined with more naturalistic, ecologically valid tasks.     

Regional drought-induced reduction in the biomass carbon sink of Canada's boreal forests

The boreal forests, identified as a critical "tipping element" of the Earth's climate system, play a critical role in the global carbon budget. Recent findings have suggested that terrestrial carbon sinks in northern high-latitude regions are weakening, but there has been little observational evidence to support the idea of a reduction of carbon sinks in northern terrestrial ecosystems. Here, we estimated changes in the biomass carbon sink of natural stands throughout Canada's boreal forests using data from long-term forest permanent sampling plots. We found that in recent decades, the rate of biomass change decreased significantly in western Canada (Alberta, Saskatchewan, and Manitoba), but there was no significant trend for eastern Canada (Ontario and Quebec). Our results revealed that recent climate change, and especially drought-induced water stress, is the dominant cause of the observed reduction in the biomass carbon sink, suggesting that western Canada's boreal forests may become net carbon sources if the climate change-induced droughts continue to intensify.     

Magical ideation is related to questionnaire but not behavioural measures of handedness

Magical ideation has repeatedly been shown to be related to handedness, with mixed-handers exhibiting higher levels of magical thinking. However, most previous research has assessed hand preference with a questionnaire measure, leaving open the possibility that the correlation reflects some aspect of questionnaire-taking behaviour and not an underlying neuropsychological relationship. The present study addressed this issue by administering the Magical Ideation Scale (Eckblad & Chapman, 1983), the Waterloo Handedness Questionnaire-Revised (Elias, Bryden, & Bulman-Fleming, 1998), and a manual dot-filling task (Tapley & Bryden, 1985) as a behavioural measure of handedness to an undergraduate student sample. The expected relationship between magical ideation and handedness as assessed by the questionnaire was observed. However, magical ideation was not related to the behavioural measure of handedness. Results cast doubt on a neuropsychological interpretation of the relationship between handedness and magical ideation in sub-clinical populations.