fMRI Mapping Research Articles

Functional magnetic resonance imaging and transcranial magnetic stimulation

Functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) represent different approaches to mapping the motor cortex. fMRI identifies areas of hemodynamic changes during task performance while TMS provides electrophysiologic data concerning the localization and density of cortical motoneurons. Here we define the spatial correlation between fMRI and TMS maps and compared them with direct electrical cortical stimulation (ECS). We performed fMRI at 1.5 T on 3 normal subjects and 2 patients with mass lesions near the central sulcus using a multislice, asymmetric, spin-echo, echo-planar pulse sequence during the performance of a motor task. We also performed focal TMS with surface EMG recordings from the muscles primarily involved in the fMRI task. We coregistered the stimulation sites in real time with the fMRI maps using a frameless stereotactic system. In both patients we also performed ECS of the cortex during surgery under local anesthesia. fMRI maps were validated by the electrophysiologic data both pre- and intraoperatively. Our results suggest that regions of fMRI activation correspond spatially to areas of highest motoneuron density as demonstrated by electrophysiologic techniques.

Functional Magnetic Resonance Imaging Mapping of the Motor Cortex in Patients with Cerebral Tumors

Functional Magnetic Resonance Imaging Mapping of the Motor Cortex in Patients with Cerebral Tumors

Comparison of FMRI and surgical brain mapping

Comparison of FMRI and surgical brain mapping

Primary visual cortex activation during visual imagery in human brain: A fMRI mapping study

Primary visual cortex activation during visual imagery in human brain: A fMRI mapping study

Functional magnetic resonance imaging of regional brain activity in patients with intracerebral gliomas: findings and implications for clinical management.

Functional magnetic resonance imaging (fMRI) was performed in seven patients harboring intracerebral gliomas proven by histological analysis using a noninvasive blood oxygen level-dependent technique based on the documented discrepancy between regional increases in blood flow and oxygen use in response to regional brain activation. We combined fMRI with conventional magnetic resonance imaging (MRI) during motor or language task activation experiments to investigate the potential usefulness of mapping regional brain activity as part of treatment planning in patients with intracerebral gliomas, in whom preservation of areas of functioning brain tissue is critical. Statistical fMRI maps were generated and directly mapped onto conventional MRI scans obtained at the same session. Of the five patients cooperative enough to remain motionless for the study and perform the task, the location of activation in the primary sensorimotor cortex on the side of the tumor was clearly displaced compared with that in the normal contralateral hemisphere in four patients. Four of the five tumors in these patients showed fMRI activation within the periphery of (or immediately adjacent to) areas of presumed tumor based on spin-echo MRI. In some patients with neurological deficit, the extent of activation was reduced on the side of the tumor as compared with the normal hemisphere. The supplemental motor area and the ipsilateral primary motor cortex were also reproducibly activated during motor tasks. We conclude that blood oxygen level-dependent fMRI can localize areas of cortical function in patients undergoing treatment planning for gliomas so that therapy can be directed away from regions of residual function. Our preliminary data suggest that functioning cortex within or adjacent to tumor margins can be demonstrated, which may correspond to partial preservation of clinical function. Our preliminary data also suggest that there may be a quantifiable difference on fMRI between activation in tumor-bearing cortex and activation in corresponding normal cortex in the contralateral hemisphere. We postulate that the magnitude of this difference may relate to the severity of patient deficit.

Functional Magnetic Resonance Imaging Mapping of the Sensorimotor Cortex with Tactile Stimulation

Functional Magnetic Resonance Imaging Mapping of the Sensorimotor Cortex with Tactile Stimulation

Functional Magnetic Resonance Imaging Mapping of the Sensorimotor Cortex with Tactile Stimulation

The purpose of this study is to compare tactile stimulation of the palm with voluntary movement of the fingers as paradigms for mapping the sensorimotor cortex in functional magnetic resonance imaging. In 22 subjects, 24 sets of functional magnetic resonance images were obtained with echoplanar acquisitions and cross-correlation image processing techniques. Two tasks were employed: a motor task in which subjects moved the thumb and index finger of one hand and a sensory task in which the palm was scratched by another person. The activation from the two tasks coincided entirely in 20 sets and partially in 3 sets. In one case, no activation was seen with the motor task. The study suggests that tactile stimulation of the palm is useful and reliable for mapping the sensorimotor cortex.

Magnetic resonance imaging mapping of brain function. Human visual cortex.

Magnetic resonance imaging (MRI) studies of human brain activity are described. Task-induced changes in brain cognitive state were measured using high-speed MRI techniques sensitive to changes in cerebral blood volume (CBV), blood flow (CBF), and blood oxygenation. These techniques were used to generate the first functional MRI maps of human task activation, by using a visual stimulus paradigm. The methodology of MRI brain mapping and results from the investigation of the functional organization and frequency response of human primary visual cortex (V1) are presented.

New MRI Techniques Allow Noninvasive Peek Inside the Thinking Human Brain

NEW MAGNETIC RESONANCE imaging (MRI) techniques may allow researchers and clinicians to noninvasively make images of the thinking human brain. MRI already has been established as a high-resolution in vivo method for studying the anatomy of the human brain and other organs. However, recently developed high-speed MRI techniques that measure changes in blood volume, flow, and oxygenation are now being used to produce the first functional MRI maps of human brain activity. Until now, functional maps of the human brain have been made using the radionuclide imaging techniques, positron emission tomography (PET) and single photon computer tomography (SPECT). Still, these techniques suffer from limited spatial and temporal resolution and they require patients to be injected with radioactive compounds, says John W. Belliveau, PhD, director of Cognitive neuroimaging at Massachusetts General Hospital, Charlestown, and Harvard Medical School, Boston. Speaking recently at a conference in San Francisco, Calif, Belliveau—who with Kenneth K.

EEG, fMRI and brain stimulation evidence for epiphenomenal conscious will

Event Abstract Back to Event EEG, fMRI and brain stimulation evidence for epiphenomenal conscious will Magnus Jandel1* and Hans Liljenstrom2 1 Swedish Defence Research Agency, Biology Dep, Sweden 2 SLU, Division of Biometry and Systems Analysis, Sweden Aim: Scant evidence from neuroscience (1-2) is used to support the philosophical position that conscious will is not causally related to the willed action, i.e. epiphenomenal. We want to dispose of the superfluous philosophical ballast, clarify what the data really can tell us and point to a way forward for future empirical work. Methods: We review the present EEG, fMRI and brain stimulation evidence for epiphenomenal conscious will considering alternative interpretations and suggestions for refined experiments. Results: Systematic effects of pre-planning on the EEG readiness potential is investigated and found to explain much of the timing behaviour that traditionally has been taken as evidence for epiphenomenal conscious will. Soon et al. (2) investigated timing correlations between conscious will and brain events measured by MRI. The fMRI maps were fed to an algorithm that managed to predict the action with at most 60% accuracy, based on fMRI data that was captured about ten seconds before the willed action. We find that this correlation could alternatively be understood as an effect of occasional unreported pre-planning, a correlation between the memory of the previous action and the next action, or a weak correlation between unconscious precursor processes and a causally connected conscious will. Desmurget et al. (1) found that stimulation of parietal areas sometimes triggers conscious will and an illusory awareness of movement. Comparing with similar experiments we find many cases where brain stimulation triggers hallucinations. The pooled brain stimulation data cannot be taken as evidence for epiphenomenal conscious will in wakeful subjects. Conclusion: We find little experimental support for the hypothesis of epiphenomenal conscious will. Much of the recent literature on what neuroscience can say about conscious will draws unwarranted philosophical conclusions from inadequate data. This is unfortunate since beliefs about the nature of conscious will is known to impact on behaviour (3). Acknowledgments: This work was supported by the European Commission, the Swedish Foundation for Strategic Research and by the Swedish Research Council.