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Results for “Brain Mapping”

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PubMed2001

Sequential activation brain mapping after subcortical stroke: changes in hemispheric balance and recovery.

We prospectively studied 5 patients while they were recovering from left-sided subcortical stroke affecting the cortico-spinal tract, and examined them twice with H(2)(15)O-PET over several months while performing an identical task with the affected hand. Concomitant motor recovery was assessed by measuring the number of thumb-to-index tappings performed in 15 s at each PET session. Across patients, the hemispheric activation balance tended to shift over time toward the unaffected hemisphere, but the magnitude of this shift was highly variable from patient to patient and significantly correlated with recovery. Thus, in subcortical stroke, a shift of activation balance towards the unaffected hemisphere appears associated with lesser initial recovery and, conversely, the more this physiological balance is maintained over time the better the recovery.

Brain Mapping↗

PubMed1990

C-EEG brain mapping in DSM-III schizophrenics after acute and chronic haloperidol treatment.

A multi-lead C-EEG investigation was carried out, in order to evaluate changes induced by acute and chronic treatment with haloperidol in DSM-III-R schizophrenics. After the acute treatment the main C-EEG changes were (1) a significant decrease of delta relative power (RP) over all the explored leads and of theta 1 over the occipital leads; (2) an increase in alpha 2 and beta 2 RP, as well as a decrease of beta 3 RP confined to the anterior temporal leads (T3, T4). During chronic treatment, C-EEG changes observed were (1) a significant decrease of delta RP and an increase of theta 1 RP; (2) an increase of alpha 1 and alpha 2 RP; (3) a significant decrease of beta 1, beta 2 and beta 3.

Adult↗

PubMed2003

Spatiotemporal activation of the two visual pathways in form discrimination and spatial location: a brain mapping study.

To address the question of the relationship between the two visual pathways, a ventral stream for object and form vision and a dorsal stream for spatial and motion vision, we measured the spatiotemporal activation patterns in the two pathways responding to an integrated visuospatial task to which form discrimination and spatial location were assigned simultaneously. The two cognitive components of form discrimination and spatial location were interwoven in the task; however, the fMRI data demonstrated that such a task still activated both ventral GTi/GF (the inferior temporal gyrus/the fusiform gyrus) and dorsal Ga/PCu (the angular gyrus/Precuneus), which are supposed to mediate form discrimination and spatial location, respectively. In addition, the source waveforms of the fMRI foci based on the source analysis of the fMRI-seeded dipole modeling and the moving dipole modeling indicated that in responding to the task combining simultaneously form perception and spatial location, the activity in Ga/PCu begins earlier than that in GTi/GF, but it peaks later and lasts longer.

Adult↗

PubMed2004

Functional brain mapping of the macaque related to spatial working memory as revealed by PET.

To define the cortical areas that subserve spatial working memory in a nonhuman primate, we measured regional cerebral blood flow (rCBF) with [(15)O]H(2)O and positron emission tomography while monkeys performed a visually guided saccade (VGS) task and an oculomotor delayed-response (ODR) task. Both Statistical Parametric Mapping and regions of interest-based analyses revealed an increase of rCBF in the area surrounding the principal sulcus (PS), the superior convexity, the anterior bank of the arcuate sulcus (AS), the lateral orbitofrontal cortex (lOFC), the frontal pole (FP), the anterior cingulate cortex (ACC), the lateral bank of the intraparietal sulcus (lIPS) and the prestriate cortex. In the prefrontal cortex (PS, superior convexity, AS, lOFC and FP), rCBF values correlated positively with ODR task performance scores. From the hippocampus, rCBF values correlated negatively with ODR task performance. From the AS, superior convexity, lOFC, FP, ACC and lIPS, rCBF values of the PS correlated positively with rCBF values and negatively with hippocampus rCBF values. These results suggest that neural circuitry in the prefrontal cortex directly contributes the spatial working memory processes and that, in spatial working memory processes, the posterior parietal cortex and hippocampus have a different role to the prefrontal cortex.

Animals↗

PubMed1999

Spectral structure and brain mapping of human alpha activities in different arousal states.

In a study with 10 young, healthy subjects, alpha activities were studied in three different arousal states: eyes closed in relaxed wakefulness (EC), drowsiness (DR), and REM sleep. The alpha band was divided into three subdivisions (slow, middle, and fast) which were analyzed separately for each state. The results showed a different spectral composition of alpha band according to the physiological state of the subject. Slow alpha seemed to be independent of the arousal state, whereas middle alpha showed a difference between REM and the other states. The fast-alpha subdivision appears mainly as a waking EEG component because of the increased power displayed only in wakefulness and lower and highly stable values for DR and REM. Scalp distribution of alpha activity was slightly different in each state: from occipital to central regions in EC, this topography was extended to fronto-polar areas in DR, with a contribution from occipital to frontal regions in REM sleep. These results provide evidence for an alpha power modulation and a different scalp distribution according to the cerebral arousal state.

Adult↗

PubMed1989

Technical and clinical aspects of topographic brain mapping.

TBM provides physiological and diagnostic information which is quite complementary to EEG, but does not replace the need for standard EEG recordings. For example, it does not show subtle morphologic abnormalities such as FIRDA, PLEDs or epileptiform discharges. Simultaneous EEG recording as well as impeccable technique are essential in proper recording of TBM, particularly as it can generate new forms of artifact. By prolonging the averaging time to over 180 seconds, and by application of flexible montages, a more accurate and cleaner record with less artifact can be obtained. Certain phenomena such as "centrifugal effect" and "comet effect" are examples of new problems generated by the advent of TBM. On the other hand, TBM can demonstrate subtle asymmetries, lateralization and localization effects more efficiently than a standard EEG. TBM is quite helpful clinically, when recording is done properly from a technical standpoint, in the diagnosis of post-traumatic syndrome and post-traumatic seizure disorder. It demonstrates subtle focal and lateralized asymmetries in cerebral hemispheric frequency bands in such patients. This information helps differentiate neurologic complications from psychiatric disorders. TBM plays a useful role in the differentiation and management of various other disorders, including depression, behavioral disturbances and dementias.

Adolescent↗

PubMed1992

Brain mapping in dysphonemic dyslexia: in resting and phonemic discrimination conditions.

Topographic mapping of EEG bands and alpha asymmetry were analyzed during resting conditions and an auditory phonemic discrimination task (APD) in carefully screened samples of 9.0- to 12-year-old control and dysphonemic-sequencing dyslexic children. The EEG was recorded over the entire scalp, with a linked ears reference. We found: (1) no differences between groups during resting conditions in any frequency band analyzed; (2) a left hemisphere alpha responsiveness in dyslexic children during the APD condition; and (3) a beta 2 decrease in the left posterior quadrant in dyslexics during the APD condition. We conclude that the lower alpha and beta 2 responsiveness may be due to a diminished cortical reactivity and may be related to intrinsic disorganization of the neural processors associated directly with the APD task demands, the alpha activity reflecting poor attention to an external stimuli source and the beta 2 decrease reflecting an unusual processing associated with the linguistic cognitive requirements.

Auditory Perception↗

PubMed2001

Human brain mapping in dystonia reveals both endophenotypic traits and adaptive reorganization.

Dystonia has a wide clinical spectrum from early-onset generalized to late-onset sporadic, task-specific forms. The genetic origin of the former has been clearly established. A critical role of repetitive skilled motor tasks has been put forward for the latter, while underlying vulnerability traits are still being searched for. Using magnetoencephalography, we looked for structural abnormalities reflecting a preexisting dysfunction. We studied finger representations of both hands in the primary sensory cortex, as compared in 23 patients with unilateral task-specific dystonia and 20 control subjects. A dramatic disorganization of the nondystonic hand representation was found in all patients, and its amount paralleled the severity of the dystonic limb motor impairment. Abnormalities were also observed in the cortex coding the dystonic limb representation, but they were important only in the most severely affected patients. The abnormal cortical finger representations from the nondystonic limb appear to be endophenotypic traits of dystonia. That finger representations from the dystonic limb were almost normal for the less severely affected patients may be due to intrinsic beneficial remapping in reaction against the primary disorder.

Adaptation, Physiological↗

PubMed2005

TMS motor cortical brain mapping in patients with complex regional pain syndrome type I.

OBJECTIVE: The motor cortical representation in patients with complex regional pain syndrome type I (CRPS I) was determined under the assumption that the motor cortex undergoes representational adaptations in the course of CRPS. METHODS: A total of 14 patients with CRPS I and a group of healthy subjects without any known neurological symptoms participated in the study. The motor cortical representation, i.e. the size of representation (cm2), motor-evoked potentials (MEP), the calculated volume (cm2 mV), and the center of gravity (CoG) were measured by transcranial magnetic stimulation. Recordings were made of the long extensor muscles of the forearm of the affected and unaffected hand. RESULTS: Analyses of the results revealed a significant asymmetry between the two hemispheres: the motor cortical representation corresponding to the unaffected hand was significantly larger. While the CoG data did not differ statistically between the two hemispheres, the CoG coordinates corresponding to the affected hand indicated a larger variability. CONCLUSIONS: The presence of pain and other CRPS symptoms may induce lasting changes in motor cortical plasticity, as it also does in the sensory cortex. SIGNIFICANCE: This could be of importance in rehabilitative strategies for the sensory motor system in CRPS I patients.

Adolescent↗

PubMed1998

Metabolic brain mapping in Alzheimer's disease using proton magnetic resonance spectroscopy.

Alzheimer's disease (AD) is a progressive disorder associated with disruption of neuronal function and neuronal loss. N-acetylaspartate (NAA) is a marker of neuronal content and can be assessed using proton (1H) magnetic resonance spectroscopy (MRS). We utilized 1H-MRS (two-dimensional chemical-shift imaging) to assess amplitudes and areas of NAA, as well as choline moieties (Cho), creatine (Cr) and myo-inositol (mI), in 15 AD patients compared with 14 control subjects. Voxels were classified as predominantly cortical gray matter (CGM), subcortical gray matter (SGM), or white matter (WM). Compared with control subjects, AD patients exhibited decreased NAA/Cho and NAA/Cr amplitudes, whereas an increase was observed in Cho/Cr and in amplitude ratios involving mI. Area ratios were significant in the same direction for NAA/Cho, NAA/Cr, mI/Cr and mI/NAA. No significant effects of tissue type were observed; however, significant group x tissue type interactions were noted for Cho/Cr and mI/Cr amplitudes. Our study confirms that 1H-MRS can identify distinct physicochemical alterations in AD patients, reflecting membrane changes and diminished neuronal function. These alterations can be used as longitudinal markers for the disease.

Aged↗

PubMed1996

[Digital EEG with brain mapping in Alzheimer's dementia and Parkinson's disease. A prospective controlled study].

In order to evaluate the EEG activity during wakefulness in senile dementia of the Alzheimer type (AD) and Parkinson's disease (PD), a prospective controlled study was performed. We compared 6 AD and 11 PD patients with a control group of 12 patients with mild to moderate major chronic depression (DSM-III-R, 1987). The median of the frequencies and the power of the posterior dominant activity was obtained in the three groups using spectral analysis. The posterior activity had a frequency of 8.79 +/- 0.52 (mean +/- sd) in the control group, 6.65 +/- 0.80 (mean +/- sd) in the AD group and 7.69 +/- 1.39 (mean +/- sd) in the PD group. The experimental hypothesis that patients with AD and PD differ from controls in relation to the background activity (defined as abnormal < 8) was confirmed by the chi square test (p = 0.01) and the t test showed that the mean of the frequency of the posterior power was significantly lower in AD (p = 0.01) and PD (p = 0.05) patients, compared with the controls. The results indicate that this abnormality could be correlated with the degree of cortical damage and natural history of these disorders.

Aged↗

PubMed1995

Repeated penicillin-induced amygdala epileptic focus in freely moving cats. EEG, polysomnographic (23-h recording), and brain mapping study.

The effect of repeated Na-penicillin (PCN) microinjections in the temporal lobe amygdala (AM) of free-moving cats was investigated in order to establish if kindling epileptogenesis is possible with this procedure. The cortical propagation of the PCN-induced post-discharge in AM and the sequence of behavioral changes induced by PCN were similar to those of AM electrical kindling. Nevertheless, the epileptogenic effect of PCN had a different evolution from that of electrical kindling, since some PCN habituation was observed after several doses. Repeated microinjections of PCN did not produce lasting alterations in sleep onset and organization. The only mild changes recorded in the 23 h following PCN microinjections were an increased latency of the first rapid eye movement (REM) sleep episode, a SWS II total time and percentage increase, and, with the highest PCN doses, a not very significant diminution of REM sleep total time. Another finding was the occurrence of REM sleep ponto-geniculo-occipital (PGO) waves, coinciding with a depression of the frequency and amplitude of interictal amygdaloid and cortical spikes. The results showed that a microinjection of PCN in the AM produced a reliable model of interictal spikes, paroxysms and generalized convulsive seizures. Nevertheless, long lasting kindling effect was not observed.

Amygdala↗

PubMed1997

[15O]-water PET and intraoperative brain mapping: a comparison in the localization of eloquent cortex.

[15O]-water PET was performed on 12 patients with structural lesions for localization of the motor (n = 5), language (receptive and expressive; n = 6), and visual cortex (n = 1). All these patients underwent interactive image-guided surgery using an infrared digitizer and intraoperative electrical stimulation mapping for motor, sensory, language, and visual cortex location. MRI-PET coregistration was performed using a surface matching approach that integrated functional information with interactive image guidance during the surgical procedure. An awake craniotomy with motor and sensory intraoperative stimulation was performed using a registered bipolar electrode that was tracked on real-time during the surgical procedure. Intraoperative functional findings were displayed and saved on the registered MRI images. The sites of functional PET activation during the performance of motor, visual and language tasks were then compared to the results of intraoperative cortical stimulation in 11 patients and visual evoked potentials in one. The results of the PET activation studies were concordant with the findings of intraoperative stimulation in all cases. During resection of the structural lesions, intraoperative stimulation was continued in the subcortical pathways, and five patients had positive responses on areas not identified by the functional PET. Furthermore, 3 patients showed transitory changes in function (speech arrest 1, naming difficulty 1, and motor weakness 1) that were reversible after changing the dissection technique or a brain retractor. [15O]-water PET was reliable in identifying the motor, visual, and language cortex. Language-related rCBF increases were highly distributive, although only part of these activations were subjected to intraoperative stimulation. We conclude that [15O]-water PET can be used for preoperative noninvasive identification of functional cortex and may be useful in neurosurgical preplanning. Intraoperative mapping still remains the main means to avoid neurological damage as it can be performed during the entire surgical procedure to avoid damage to cortex, pathways, and damage secondary to ischemia or edema (brain retraction).

Adolescent↗

PubMed2000

EEG brain mapping of phonological and semantic tasks in Italian and German languages.

OBJECTIVES: Event-related potential correlates of phonological encoding - as compared with lexical access and semantic categorization - were measured in two studies involving two groups of 14 German and 14 Italian subjects. METHODS: A two stimulus reaction time paradigm was used. Stimulus pairs presented one-by-one with 2 s inter-stimulus intervals (ISI) had to be matched with respect to lexical identity (word-picture) in a word comprehension task or with respect to the phonological representative of objects in a rhyming task. A semantic categorization task was added for the Italian sample. In both studies, the EEG was recorded from 26 scalp electrodes according to the 10-20 system. The slow negative potential during the ISI (CNV) was determined as the electrocortical correlate of preparation for and activation of the specific language-related task. RESULTS: In both samples, phonological encoding (rhyming) evoked a more pronounced CNV over the left- compared with the right-frontal area, while less lateralized central dominance of the CNV was found in the word comprehension task. Semantic categorization was accompanied by the least asymmetry of activity. CONCLUSIONS: Results indicate that the different degree of asymmetry induced by phonological and semantic processing may be determined from the scalp distribution of slow cortical potentials with cross-lingual reliability.

Acoustic Stimulation↗

PubMed2000

ERPs and PET analysis of time perception: spatial and temporal brain mapping during visual discrimination tasks.

ERPs were recorded from 12 subjects performing duration and intensity visual discrimination tasks which have been previously used in a PET study. PET data showed that the same network was activated in both tasks [P. Maquet et al., NeuroImage 3:119-126, 1996]. Different ERP waveforms were observed for the late latency components depending on the dimension of the stimulus to be processed: frontal negativity (CNV) for the duration task and parieto-occipital positivity (P300) for the intensity task. Using BESA software, the sources were first modelled with a "PET dipolar model" (right prefrontal, right parietal, anterior cingulate, left and right fusiforms). To obtain a better fit for ERPs recorded in each task, two sources (cuneus, left prefrontal area) had to be added. Consistently with PET findings, dipole modelling indicates that duration and intensity dimensions of a visual stimulus are processed in the same areas. However, ERPs also reveal prominent differences between the time course of the dipole activations for each task, particularly for sources contributing to the late latency ERP components. In the intensity task, dipoles located in the cuneus, the anterior cingulate, and the left prefrontal area yield largest activity within the P300 interval, then activity diminishes rapidly as the stimulus ends, whereas in the duration task, the cuneus and anterior cingulate are still active several hundred milliseconds following stimulus offset. Moreover, in the duration task, the activity of the right frontal dipole parallels the CNV waveform, whereas in the intensity task, this dipole is largely inactive. We assume that the right frontal area plays a specific role in the formation of temporal judgments.

Adult↗

PubMed2000

Functional connectivity of the anterior cingulate cortex within the human frontal lobe: a brain-mapping meta-analysis.

A database of positron-emission-tomography studies published between January 1993 and November 1996 was created to address several questions regarding the function and connectivity of the human anterior cingulate cortex (ACC). Using this database, we have previously reported on the relationship between behavioural variables and the probability of blood-flow response in distinct subdivisions of the ACC. The goal of the current analysis was to discover which areas of the frontal cortex show increased blood-flow co-occurring consistently with increased blood-flow in the ACC. Analyses of the frequency distributions of peaks in the ACC and the remaining frontal cortex (FC) yielded several important findings. First, FC peaks in the precentral gyrus, superior frontal gyrus, middle frontal gyrus, inferior frontal gyrus, medial frontal gyrus and orbitomedial frontal gyri were more frequent in subtractions that also yielded a peak in the ACC than in those that did not yield an ACC peak. Second, regional differences in the frequency distribution of these FC peaks were observed when the ACC peaks were subdivided into the rostral versus caudal ACC and supracallosal versus subcallosal ACC. Peaks in the precentral gyrus and in the vicinity of the supplementary motor area were more prevalent in subtractions with co-occurring peaks in the caudal than with the rostral ACC. Peaks in the middle frontal gyrus were more frequent in subtractions with co-occurring peaks in the paralimbic part of the supracallosal ACC, relative to the subcallosal or limbic supracallosal ACC. These observations are consistent with known differences in the anatomic connectivity in these cortical regions, as defined in non-human primates. Further analyses of the influence of behavioural variables on the relationships between the ACC and other regions of the frontal cortex suggested that this type of meta-analysis may provide testable hypotheses about functional and effective connectivity within the human frontal lobe.

Brain Mapping↗

PubMed2006

Statistical representation of mean diffusivity and fractional anisotropy brain maps of normal subjects.

PURPOSE: To create diffusion tensor atlases from echo planar imaging (EPI) images acquired at 3 T in 10 normal subjects. MATERIALS AND METHODS: Data from 10 right-handed healthy adult volunteers (mean age of 31 +/- 3 years; eight males) were acquired using a 3.0-T scanner. Geometric distortion artifacts correction was accomplished by combining parallel acquisition to reduce the distortion as well as postprocessing by registration to a geometrically accurate T2-weighted fast-spin-echo image. This reduced distortions to within a voxel for most of the internal structures of the brain. The apparent diffusion coefficient (ADC) and fractional anisotropy (FA) atlases were created by warping images using an iterative optical-flow-based local deformation algorithm that used two channels of data: ADC and FA. RESULTS: A three-dimensional distance measure was used to evaluate the accuracy of the registration algorithm with contours defined on two structures: the corpus callosum and cerebellum. The average three-dimensional distance value for the nine subjects (with the 10th as the reference) was 0.2 mm for the corpus callosum and 1.2 mm for the cerebellum. CONCLUSION: A high-resolution, diffusion MR atlas with full brain coverage was developed. Additionally, maps of the SD of the diffusion indices were also generated to provide an estimate of the variance within a normal population. Active shape and texture models were also generated for the corpus callosum as an alternate method of representing the variance in morphology and diffusion indices.

Adult↗

PubMed2002

Introspection and cognitive brain mapping: from stimulus-response to script-report.

Cognitive science has wholeheartedly embraced functional brain imaging, but introspective data are still eschewed to the extent that it runs against standard practice to engage in the systematic collection of introspective reports. However, in the case of executive processes associated with prefrontal cortex, imaging has made limited progress, whereas introspective methods have considerable unfulfilled potential. We argue for a re-evaluation of the standard 'cognitive mapping' paradigm, emphasizing the use of retrospective reports alongside behavioural and brain imaging techniques. Using all three sources of evidence can compensate for their individual limitations, and so triangulate on higher cognitive processes.

Journal Article↗