Jarl Risberg

Regional cerebral blood flow measurements by 133Xe-inhalation: Methodology and applications in neuropsychology and psychiatry ☆

This review describes methodological improvements of the 133Xe-inhalation technique for measurement of regional cerebral blood flow (rCBF) comprising correction routines both for scattered radiation from air passages and for remaining activity from previous measurements, as well as a new index of curve fit exactness. Measurements in normals are described showing new characteristics of the resting flow pattern and localized flow changes during activation with a variety of mental tasks. Our clinical applications in psychiatry are reviewed demonstrating the ability of the rCBF technique for differential diagnosis of dementia, for the evaluation of treatment by drugs, ECT, or psychosurgery, as well as for following, cases of toxic influence. The paper finally discusses the potentials as well as the limitations and artifacts of the technique.

On the neurobiology of creativity. Differences in frontal activity between high and low creative subjects

The aim was to investigate the relationship between creativity and hemispheric asymmetry, as measured by regional cerebral blood flow (rCBF). Two groups, each consisting of 12 healthy male subjects, who got either very high or low scores on a creativity test, were pre-selected for the rCBF investigation. rCBF was measured during rest and three verbal tasks: automatic speech (Auto), word fluency (FAS) and uses of objects (Brick). State and trait anxiety inventories were answered after the rCBF measurements. Intelligence tests were also administered. It was predicted that highly creative subjects would show a bilateral frontal activation on the divergent thinking task (Brick), while low creative subjects were expected to have a unilateral increase. Calculations were made of differences in blood flow levels between the FAS and the Brick measurements in the anterior prefrontal, frontotemporal and superior frontal regions. In accordance with our prediction, repeated measure-ANOVAs showed that the creativity groups differed significantly in all three regions. The highly creative group had increases, or unchanged activity, while the low creative group had mainly decreases. The highly creative group had higher trait anxiety than the low creative group. On the intelligence tests the low creative group was superior both on logical-inductive ability and on perceptual speed, while the groups were equal on verbal and spatial tests. The results are discussed in terms of complementary functions of the hemispheres.

Sex Differences in Regional Cerebral Blood Flow

Regional cerebral blood flow was measured by the 133-xenon inhalation method during resting in 38 healthy men and 38 healthy women matched pairwise for age in the range 18–72 years. The results showed 11% higher global flow level in the women in all ages. A similar and significant regression of flow by age was seen for both sexes. The regional flow distribution also showed some sex-related differences. Frontal regions showed an asymmetry in the men with higher values on the right side. The female flows were more symmetric. As a hypothesis, it is suggested that the higher flow level in women may be a systemic phenomenon. In fact, other authors have found a higher cardiac index in females. The sex differences in regional flow pattern might be due to differences in the functional organization of the cortex and/or to differences in the mental processes of the “resting” state.

Increase of regional cerebral blood flow during mental effort in normals and in patients with focal brain disorders

SummaryRegional cerebral blood flow (rCBF) was recorded simultaneously in four circumscribed hemisphere regions in 30 subjects in double determinations by means of the intra-arterial 133Xenon clearance technique. Group I was a control group of 10 subjects. Group II consisted of 12 subjects of which 4 were normals and 8 were patients without signs of organic local or diffuse cerebral disorders. Group III consisted of 8 patients with localized hemisphere lesions. During one of the rCBF measurements, the subjects in Groups II and III were asked to perform a digit-span-backward test. In Group II the test gave rise to a small but significant increase in rCBF which averaged about 2.2 ml/100 g/min in mean rCBF, i. e. an increase of about 5 %, and 5.7 ml/100 g/min for gray matter flow, i.e. an increase of 8%. This increase was most evident in “suprasylvian” parts of the hemisphere. An increase in rCBF was also found in Group III with focal cerebral lesions. In four cases with circumscribed lesions which all involved superficial parts of the hemisphere, only small or no changes were seen during mentation within the lesions, and some marked augmentations outside the pathologic areas.The augmentation of rCBF during the test probably reflects more or less regional functional (metabolic) accompaniments to mentation. It is likely that both general changes of the ‘arousal’ type, as well as localized gray matter changes take part in these events.

Observations on the functional significance of regional cerebral blood flow in "resting" normal subjects.

Abstract Regional Cerebral Blood Flow (rCBF) of 16 cortical regions was measured bilaterally in 22 healthy adults, with 4–8 repeated measurements per individual. All measurements were done during “rest”, i.e. with minimal external stimulation, by the Xe-133 inhalation method. The data are presented to serve as normal controls for research and clinical work, but more importantly because of their significance for neuropsychological theory. Some rCBF variance is shown to be meaningfully related to handedness, habituation processes, biological rhythms and possibly to regional lateral dominance. Further data and discussion relate to the possible role of frontal lobe structures during non-task-oriented cognition. Finally, data are interpreted as showing that regional functional coupling across the midline, in this situation, is inversely related to the characteristic level-of-processing associated with each area.

The Swedish Centenarian Study: A Multidisciplinary Study of Five Consecutive Cohorts at the Age of 100

Centenarians born 1887–91, who lived in southern Sweden were asked to participate in this multidisciplinary study (N = 164). Of the survivors (N = 143), 70 percent agreed (N = 100). The purpose was to describe the population from physical, social, and psychological points of view; to characterize centenarians with various health conditions and diverse degrees of autonomy and life satisfaction; and to identify factors at 100 years that predict future survival. Results: Eighty-two percent were women, 25 percent lived in their own home, 37 percent in old age homes, and 38 percent in nursing homes. Socioeconomic status showed a similar distribution compared to nationally representative data. Fifty-two percent managed activities of daily living with or without minor assistance. The incidence of severe diseases was low. In 39 percent a disorder of the circulatory system was found. Thirty-nine percent (women) and 11 percent (men) had had at least one hip fracture. Twenty percent had good hearing and good vision. Twenty-seven percent were demented according to DSM III-R criteria. Means on cognitive tests (word-list, digit-span, learning, and memory) were lower compared to seventy to eighty year old groups. The variation in performance was extremely widespread. Personality profiles (MMPI) indicated that the centenarians were more responsible, capable, easygoing and less prone to anxiety than the population in general. Extensive neuropathological investigation revealed no major diseases or large lesions but mild though multiple changes. Results suggest that centenarians are a special group genetically. A causal structure model emphasized body constitution, marital status, cognition and blood pressure as particularly important determinants for survival after 100 years.

Changes of cortical activity patterns during habituation to a reasoning test: A study with the 133Xe inhalation technique for measurement or regional cerebral blood flow

Abstract Measurements of the regional cerebral blood flow in eight regions of the left hemisphere using the 133 Xe inhalation technique were carried out on 12 healthy male right-handed volunteers during two consecutive days in a rest-test experimental paradigm using the Ravens Advanced Progressive matrices. The first testing session showed increases of blood flow in frontal and posterior regions; the frontal increases, however, did not appear during the second measurement session when a parallel version of the test was presented, while the posterior increases were as evident as on the first day. The results are interpreted as showing habituation of the frontal regions supposedly engaged in processes of non-specific nature and the specific involvement of the posterior cortex in problem-solving.

Intravenous physostigmine treatment of Alzheimer's disease evaluated by psychometric testing, regional cerebral blood flow (rCBF) measurement, and EEG.

Ten patients with Alzheimers disease were treated with intravenous infusion of physostigmine for 2 h. The acute effects on cognitive function, regional cerebral blood flow, and EEG were compared to placebo (isotonic glucose) using a double-blind cross-over design. Physostigmine causes a limited improvement of psychomotor performance and EEG and an increase of blood flow in the most severely affected cortical areas, predominantly in an early phase of Alzheimers disease.

Regional cerebral blood flow in long-term heavy cannabis use

Regional cerebral blood flow (rCBF) was measured by the 133Xenon inhalation method in nine male chronic cannabis users. The rCBF level in cannabis users was significantly (11%) lower than that of age- and sex-matched healthy controls. Four of the subjects were reexamined after 9-60 days of detoxification and showed a significant (12%) increase of the CBF level at followup. No significant regional flow abnormalities were noted. The global CBF reduction seen in the early phase of detoxification is most likely the consequence of the dysfunction of the central nervous system accompanying chronic cannabis use.

Regional cerebral blood flow characteristics and variations with age in resting normal subjects

Regional cerebral blood flow (rCBF) was measured during resting in 97 normal subjects, 19-68 years old. The results showed that the mean CBF level decreased progressively with age. The decrease was more prominent in frontotemporal and inferior Rolandic areas bilaterally. Frontal areas showed the highest values in all age groups. This hyperfrontality weakened somewhat with age. Mean CBF in the right hemisphere was significantly higher than in the left, as was flow in superior frontal, inferior frontal, and parietal areas. These asymmetries were age invariant. The age-related decrease of rCBF is interpreted as reflecting aging of the brain per se, although the influence of asymptomatic brain disease can not be ruled out. The flow asymmetries are interpreted as being related to functional lateralization of some aspects of attentional activation.