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fMRI Paradigm (fmri + paradigm)

Distribution by Scientific Domains

Medical Sciences	75%

Selected Abstracts

CNS response to a thermal stressor in human volunteers and rats may predict the clinical utility of analgesics

DRUG DEVELOPMENT RESEARCH, Issue 1 2007
David Borsook
Abstract fMRI was used to test the hypothesis that global brain activation following a stressor (a thermal stimulus) that activates multiple brain circuits in healthy subjects can predict which drugs have higher potential for clinical utility for neuropathic pain. The rationale is that a drug will modulate multiple neural circuits that are activated by the system-specific stressor (e.g., pain). In neuropathic pain, some brain circuits have altered function, but most brain systems are "normal." Thus, the manner in which a drug effect on neural circuits is modulated by the stressor may provide insight into the clinical utility based on the readout of brain activation in response to the stimulus. Six drugs with known clinical efficacy (or lack thereof) in treating neuropathic pain were selected and the CNS response to each drug in the presence or absence of a pain stimulus was examined. The present results suggest that it is possible to identify potentially effective drugs based on patterns of brain activation in healthy human subjects and indicate that CNS activity is a more sensitive measure of drug action than standard psychophysical measures of pain intensity. This approach was repeated in rats and showed that a similar fMRI paradigm segregates these drugs in a similar manner suggesting a potential "translational tool" in evaluating drug efficacy for neuropathic pain. The sensitivity of this paradigm using fMRI allows clinical screening in small groups of healthy subjects, suggesting it could become a useful tool for drug development as well as for elucidating the mechanisms of neuropathic disease and therapy. Drug Dev. Res. 68:23,41, 2007. © 2007 Wiley-Liss, Inc. [source]

Functional MRI Predicts Memory Performance after Right Mesiotemporal Epilepsy Surgery

EPILEPSIA, Issue 2 2005
Jozsef Janszky
Summary:,Purpose: Anterior temporal lobe resection (ATR) is a treatment option in drug-resistant epilepsy. An important risk of ATR is loss of memory because mesiotemporal structures contribute substantially to memory function. We investigated whether memory-activated functional MRI (fMRI) can predict postoperative memory loss after anterior temporal lobectomy in right-sided medial temporal lobe epilepsy (MTLE). Methods: We included 16 patients (10 women) aged 16,54 years. The mean age at epilepsy onset was 12.5 years (range, 1,26 years). The patients' mean Wechsler IQ score was 95.2 (range, 62,125). The activation condition of fMRI consisted of retrieval from long-term memory induced by self-paced performance of an imaginative walk. All but one patient had left-sided speech dominance according to speech-activated fMRI. Outside the scanner, we evaluated the pre- and postoperative visual memory retention by using Rey Visual Design Learning Test. Results: We found a correlation between the preoperative asymmetry index of memory- fMRI and the change between pre- and postsurgical measures of memory retention. Reduced activation of the mesiotemporal region ipsilateral to the epileptogenic region correlated with a favorable memory outcome after right-sided ATR. Conclusions: In light of the postoperative results, the theoretical implication of our study is that fMRI based on a simple introspective retrieval task measures memory functions. The main clinical implication of our study is that memory- fMRI might replace the invasive Wada test in MTLE by using a simple fMRI paradigm. Predictive power, however, will be studied in larger patient samples. Other studies are required for left-sided MTLE and neocortical epilepsies to assess the clinical usefulness of memory- fMRI. [source]

Biphasic hemodynamic responses influence deactivation and may mask activation in block-design fMRI paradigms

HUMAN BRAIN MAPPING, Issue 4 2008
Jed A. Meltzer
Abstract A previous block-design fMRI study revealed deactivation in the hippocampus in the transverse patterning task, specifically designed, on the basis of lesion literature, to engage hippocampal information processing. In the current study, a mixed block/event-related design was used to determine the temporal nature of the signal change leading to the seemingly paradoxical deactivation. All positive activations in the hippocampal-dependent condition, relative to a closely matched control task, were seen to result from positive BOLD transients in the typical 4,7 s poststimulus time range. However, most deactivations, including in the hippocampus and in other "default mode" regions commonly deactivated in cognitive tasks, were attributable to enhanced negative transient signals in a later time range, 10,12 s. This late hemodynamic transient was most pronounced in medial prefrontal cortex. In some regions, the hippocampal-dependent condition enhanced both the early positive and late negative transients to approximately the same degree, resulting in no significant signal change when block analysis is used, despite very different event-related responses. These results imply that delayed negative transients can play a role in determining the presence and sign of brain activation in block-design studies, in which case an event-related analysis can be more sensitive than a block analysis, even if the different conditions occur within blocks. In this case, default mode deactivations are timelocked to stimulus presentation as much as positive activations are, but in a later time range, suggesting a specific role of negative transient signals in task performance. Hum Brain Mapp, 2008. © 2007 Wiley-Liss, Inc. [source]

Abnormal visual activation in Parkinson's disease patients,

MOVEMENT DISORDERS, Issue 11 2010
Ellison Fernando Cardoso MD
Abstract Among nonmotor symptoms observed in Parkinson's disease (PD) dysfunction in the visual system, including hallucinations, has a significant impact in their quality of life. To further explore the visual system in PD patients we designed two fMRI experiments comparing 18 healthy volunteers with 16 PD patients without visual complaints in two visual fMRI paradigms: the flickering checkerboard task and a facial perception paradigm. PD patients displayed a decreased activity in the primary visual cortex (Broadmann area 17) bilaterally as compared to healthy volunteers during flickering checkerboard task and increased activity in fusiform gyrus (Broadmann area 37) during facial perception paradigm. Our findings confirm the notion that PD patients show significant changes in the visual cortex system even before the visual symptoms are clinically evident. Further studies are necessary to evaluate the contribution of these abnormalities to the development visual symptoms in PD. © 2010 Movement Disorders Society [source]