ISSN:1065-9471    

DOI:10.1002/hbm.460010102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractChanges in the regional cerebral blood flow (rCBF) are often used as an indicator of changes in local neuronal activity of the brain. We present here quantitative measurements with positron emission tomography (PET) of rCBF with a freely diffusible flow tracer15O‐butanol in control and activation states, and a pixel‐by‐pixel statistical parametric analysis of the rCBF changes combined with a cluster analysis. Anatomically standardized rCBF activation data from 39 normal subjects were analyzed for the occurrence of clustered voxels. Noise data was obtained from repeat measurements of rCBF with the brain in the activated state and from simulations. The variance in test‐control images was largest outside the skull, and large in soft tissue regions around the brain. It was moderate but inhomogenous in gray matter, and low and homogenous in white matter. A special picture was generated of the conformation of sampled data with a normal distribution. In the gray and white matter, the pixel values were fount to conform to a normal distribution, permitting calculation of Student's t‐images. In the cluster analysis, activations are detected as clusters of voxels with high t‐values. The clusters in activated regions, however, were considerably larger than the full width half‐maximum of spatial autocorrelation function and were easily detected. Tables of the empirical Poisson‐like distributions of the number of clusters of different sizes are provided, from whichPvalues of the significance of the occurrence of clusters of different sizes can be estimated. © 1993

ISSN:1065-9471    

DOI:10.1002/hbm.460010103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe understanding of the relationships between music and the brain is a legitimate goal of neuroscientific research. In spite of an already large body of experimental investigation, however, the outcome has not been as satisfactory as expected, to the point that some have voiced their incredulity at the feasibility of mapping musical functions onto cerebral structures. There are indeed considerable inconsistencies in the literature bearing on the neurobiological substrates of musical functions. Before giving in to skepticism, though, it is appropriate to examine whether such inconsistencies are unavoidable and a necessary outcome of neuroscientific investigation into musical functions. This paper, therefore, examines some of the reasons that may be responsible for the inconsistencies. Beyond the superficial similarities between language and music, these two domains are functionally distinct, yet neuropsychological research in music and its neurobiological substrates has been modeled after that in verbal language, borrowing concepts and methods that were not entirely suited to the study of musical functions. An examination of the diverse factors inherent in any study of music‐brain relationships reveals a variety of potential sources of difficulties, which, if properly controlled, would guarantee higher consistency and enhance the reliability of experimental findings. It is thus suggested that progress in understanding music‐brain relationships may result from (1) explicitly outlining the structural cognitive architecture of musical functions; (2) formulating the problems in terms of underlying operations rather than in terms of vague and unspecified dichotomic views of hemisphere processing; (3) designing experiments that are musically valid and coherent, and that do not lend themselves to multiple strategies; (4) setting up appropriate controls to ensure that subjects are performing as expected; (5) restricting the investigation to musically literate individuals; (6) selecting, among such individuals, a homogeneous set of subjects sharing common musical abilities; and (7) using investigatory techniques that yield reliable evidence of local cerebral involvement in realizing the tasks under study. © 1993 Wiley‐Lis

ISSN:1065-9471    

DOI:10.1002/hbm.460010104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractRecent advances in positron emission tomography techniques provide a way of studying the functional anatomy of language processes in the normal brain. A large amount of data have already been acquired using the subtractive activation method, which consists of comparing regional metabolic brain activities between two experimental conditions, a reference condition and an active condition (e. g., a language task). In spite of the potential interest of such results, their interpretation may be obscured by conflicting theoretical issues on the nature of brain‐language relationships and by various methodological problems, which are described in this review paper. The exact nature of the language task and stimuli used in the activation paradigms appear to be critical for this topic. Moreover, the strictly hierarchical, unidimensional subtractive method, previously described by Petersen et al. ([1988]: Nature 331:585–589) seems not to be adequate for generating appropriate contrasts between activation conditions in most language paradigms. Further progress in the analysis of task‐related changes in distribution of cerebral activities, are expected from: (1) other methods that should complement the subtractive approach, such as analysis of interregional correlations of cerebral activity which would account for the distributed anatomy of language functions; and (2) single‐subject studies in which issues of anatomical and cognitive interindividual variability may be addressed. © 1993 Wiley

ISSN:1065-9471    

DOI:10.1002/hbm.460010105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractWe recorded auditory evoked magnetic fields from nine healthy subjects with a 122‐channel whole‐head SQUID magnetometer. This type of measurement ensures that responses from both hemispheres are collected in the same stage of vigilance. The stimuli were 50‐ms 1‐kHz tones, delivered alternately to the two ears at interstimulus intervals (ISIs) of 1, 2, 4, 8, and 16 s per ear. In both hemispheres, the prominent 100‐ms response (N100m) was, on average, 22% larger and 9 ms earlier for contralateral than ipsilateral tones. The N100m amplitude increased as a function of ISI and saturated at ISIs of 8–16 s. The average ISI dependence of N100m was similar over both hemispheres and for both contralateral and ipsilateral stimuli, implying that tones leave neural traces of similar duration in both hemispheres. Differences were observed as well: the response waveforms were clearly asymmetric in one subject, and four subjects displayed an additional right‐hemisphere‐dominant 250‐ms deflection (N250m). © 19

ISSN:1065-9471    

DOI:10.1002/hbm.460010106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThis study evaluated whether cerebral blood flow positron emission tomography (CBF PET) could provide assessments of language dominance comparable to the invasive reference method, the Wada test (selective intracarotid injection of amytal with cognitive testing subsequent to the anesthesia of each hemisphere). In 9 of 11 patients with partial complex epilepsy who were operative candidates, the Wada test lateralized unequivocally; in two subjects Wasa results were indeterminate (no speech arrest following injection of either carotid). Of four brain regions selected a priori for PET analysis based on techniques developed from studies of normal volunteers, anterior frontal cortex (AFC) was most consistently detectable and lateralized. AFC laterality agreed with Wada laterality in eight of the nine subjects lateralized by Wada. In both subjects having an indeterminate Wada, PET demonstrated clear laterality. In one subject both PET and Wada lateralized, but in disagreement; anterior temporal lobectomy in the hemisphere indicated by PET as language‐dominant caused long‐lasting language impairment. We conclude that CBF PET: (1) provides an effective, noninvasive adjunct to the Wada test; and (2) permits assessment of language dominance in normal research volunteers. © 1993 Wiley‐Lis

ISSN:1065-9471    

DOI:10.1002/hbm.460010107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA voxel‐based method of measuring the effective connectivity between brain regions is presented. The approach is based on electrophysiological concepts and is applied to neurophysiological data obtained with [positron emission tomography (PET)] functional imaging. Time‐dependent changes in effective connectivity were assessed during a verbal fluency activation paradigm using 12 consecutive measurements of regional cerebral blood flow (rCBF). The changes observed were predicted by an associative (Hebbian) model of plasticity, applied to cortical activity, measured in terms of rCBF. The main finding was, in most regions, a selective enhancement of effective connections from the distributed brain regions exhibiting the dominant pattern of correlated activity. © 1993 Wiley‐Lis

ISSN:1065-9471    

DOI:10.1002/hbm.460010108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:1065-9471    

DOI:10.1002/hbm.460010101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY