Showing papers by "Russell A. Poldrack published in 2002"

Memory lateralization in medial temporal lobe epilepsy assessed by functional MRI.

Abstract: Summary: Purpose: To determine the utility of functional magnetic resonance imaging (fMRI) in preoperative lateralization of memory function in patients with medial temporal lobe epilepsy (MTLE). Methods: Nine patients with MTLE underwent standard preoperative assessment including video-EEG and intracarotid amytal testing (IAT). fMRI was performed while subjects encoded four types of stimuli (patterns, faces, scenes, and words). Activation maps were created for each subject representing areas more active for novel than for repeated stimuli. Regions of interest were drawn around the MTL in individual subjects, suprathreshold voxels were counted, and an asymmetry index was calculated. Results: In eight of nine subjects, lateralization of memory encoding by fMRI was concordant with that obtained from the IAT. Group-level analysis demonstrated greater activation in the MTL contralateral to the seizure focus such that in the left MTLE group, verbal encoding engaged the right MTL, whereas in the right MTLE group, nonverbal encoding engaged the left MTL. Conclusions: fMRI is a valid tool for assessing of memory lateralization in patients with MTLE and may therefore allow noninvasive preoperative evaluation of memory lateralization. FMRI revealed that memory encoding may be reorganized to the contralateral MTL in patients with MTLE. Key Words: Epilepsy—Medial temporal lobe—fMRI—Memory. Epilepsy surgery is an important tool for the treatment of patients with medically refractory seizures and is particularly effective in patients with medial temporal lobe epilepsy (MTLE). These patients have frequent complex partial seizures originating from a sclerosed hippocampus. In well-selected patients, temporal lobectomy with resection of the mesial structures can significantly reduce or eliminate seizures in up to 90% of patients (1–3). The challenge in epilepsy surgery is to remove the seizure focus completely without causing significant postoperative neurologic deficits; this requires an understanding of the underlying functional anatomy. Patients with longstanding epilepsy may have variable anatomic localization of neurologic functions, such as memory, because of cerebral reorganization induced by the disease process. Understanding this functional anatomy is vital when planning surgical resections and relies on complex preoperative evaluations.

Pediatric Functional Magnetic Resonance Imaging: Progress and Challenges

Abstract: Summary:Functional magnetic resonance imaging (fMRI) in the pediatric population promises to provide novel insights into the nature of both normal and abnormal functional brain development as well as changes in brain function due to various interventions. Although acquisition of fMRI data from child

Neural Systems for Perceptual Skill Learning

Abstract: Recent studies have begun to use functional neuroimaging techniques to examine the changes in brain activity that occur as humans learn new skills. This review outlines results from a number of imaging studies examining visual perceptual skill learning. Although the regions engaged during skill learning differ across tasks, a common finding has been increasing activation in the inferior temporal and fusiform gyri as skill is acquired and activation of the caudate nucleus in association with learning. Neuroimaging has great promise for the understanding of learning at the level of large neural populations, but further work is necessary to understand the specificity of learning-related changes and their relation to underlying neurophysiological plasticity.

Modeling of the Hemodynamic Response Function for Event Related Motor and Visual Stimuli as Measured by Near Infrared Spectroscopy

Abstract: The hemodynamic response function to motor and visual stimuli was measured by near infrared spectroscopy. A comparison with models of neuro-vascular coupling and hemodynamic response is made and implications discussed.