Biomedical subjects

Patrick W Stroman

Publications and source records attributed to Patrick W Stroman.

10 recordsLinked to original sources

PubMed2007

Comparison of functional activity in the rat cervical spinal cord during alpha-chloralose and halothane anesthesia.

Alpha-chloralose is commonly used during animal fMRI studies for anesthesia, however, recovery of animals is difficult, limiting experimental design. The use of a less invasive anesthetic would enable chronic experiments. The present study compares functional activity in the spinal cord of the alpha-chloralose and halothane-anesthetized rat. Functional MRI of the rat cervical spinal cord was performed on 6 alpha-chloralose and 6 halothane-anesthetized rats in a Bruker 7 T MR system during electrical stimulation of the right forepaw. Following imaging, four animals from each group were perfused and spinal cords removed for immunohistochemical analysis. Areas of c-fos expression were identified with immunofluorescent labeling to confirm the presence of neuronal activity. Functional activity and c-fos expression were observed predominantly between the fifth and seventh cervical spinal cord segments. Areas of fMRI activation in the spinal cord correspond well with spinal cord physiology. Areas of c-fos expression confirmed that neuronal activity was present in the regions of fMRI activity. The regions and amount of fMRI activity observed were similar for both anesthetics. Functional magnetic resonance imaging of the spinal cord can be achieved using both alpha-chloralose and halothane anesthesia in rats. We therefore suggest that halothane may be used as an anesthetic agent for chronic fMRI studies of the spinal cord.

Anesthetics, Inhalation↗

PubMed2005

Functional magnetic resonance imaging based on SEEP contrast: response function and anatomical specificity.

Functional magnetic resonance imaging based on a non-BOLD-contrast mechanism, which we have termed "SEEP" (Signal Enhancement by Extravascular water Protons), has previously been demonstrated. Here the reproducibility of areas of activity identified with both SEEP and BOLD contrast is assessed in duplicate experiments in healthy volunteers, with relatively high resolution (1.6 mm) image data at 1.5 T. These areas of activity are equally well localized to voxels containing primarily gray matter with the two contrast mechanisms. As in previous studies, areas of SEEP activity are observed to be immediately adjacent to areas of BOLD activity, with very little overlap. The response functions were estimated for both SEEP and BOLD contrast, and are observed to be distinct. The peak SEEP response is observed to lag the BOLD response by approximately 1 s and to decay more slowly with no poststimulus undershoot. Average BOLD signal changes (GE-EPI, TE=50 ms) were observed to be 3.4+/-1.2% (mean+/-S.D.), whereas SEEP signal changes (SE-EPI, TE=23 ms) were 1.9+/-0.5%, consistent with previous studies carried out at 0.2 and 3 T. These observations provide further support for the existence of a non-BOLD-contrast mechanism for fMRI, based on changes in extravascular spin density.

Brain↗

PubMed2005

The role of the striatum in implicit learning: a functional magnetic resonance imaging study.

Previous research has posited striatal involvement in implicit learning. However, imaging studies have not directly compared learners with non-learners. Using functional magnetic resonance imaging with 15 study participants, we used an implicit learning task previously associated with striatal recruitment. Dorsal and ventral striatum activation was observed in the eight participants who demonstrated implicit learning. Ventral striatum activations occurred to a greater extent in implicit learning versus non-implicit learning participants, and were correlated with the degree of reaction time advantage in implicit learning participants, even after controlling for general decreases in reaction time over time. These findings strengthen the specificity of the striatum in implicit learning and are suggestive of a dissociation of striatal regions relative to elements of implicit learning performance.

Adolescent↗

PubMed2005

An improved method for spinal functional MRI with large volume coverage of the spinal cord.

PURPOSE: To develop a spinal functional MRI (fMRI) method with three-dimensional coverage of a large extent of the spinal cord with minimal partial volume effects MATERIALS AND METHODS: fMRI data of the cervical spinal cord were obtained at 1.5 T with a single-shot fast spin-echo imaging method, from thin contiguous sagittal slices spanning the cord. Thermal stimulation was applied to the palm of the hand in a block pattern with 15 degrees C for stimulation and 32 degrees C during baseline periods. Prior to analysis, the image data at each time point were reformatted into three-dimensional volumes and resliced perfectly transverse to the spinal cord. Smoothing was applied only in the superior-inferior (S/I) direction across uniform tissue types. Active voxels were then identified by means of a correlation to a model paradigm. RESULTS: The resulting activity maps demonstrate activity primarily in ipsilateral sensory areas and in some motor areas, consistent with the spinal cord neuroanatomy. These data also demonstrate detail of the subsegmental organization of the spinal cord, as well as anatomical detail of the spinous processes and positions of nerve roots. CONCLUSION: The spinal fMRI method described enables large volume coverage of the spinal cord in three dimensions, with reliable and reproducible results.

Humans↗

PubMed2005

Magnetic resonance imaging of neuronal function in the spinal cord: spinal FMRI.

A review of the current literature on magnetic resonance imaging of neuronal function in the spinal cord (spinal fMRI) is presented. The unique challenges of spinal fMRI are identified as being the small cross-sectional dimensions of the spinal cord, magnetic field inhomogeneity caused by the bone and cartilage in the spine, and motion of cerebrospinal fluid, blood, adjacent tissues and organs and of the spinal cord itself. Techniques have been developed to overcome or compensate for these challenges and the result is a fMRI method which is distinct from that used for mapping function in the brain. Evidence that the current spinal fMRI method provides accurate and sensitive maps of neuronal function is also discussed. Studies presented in the literature have demonstrated areas of neuronal activity corresponding with spinal cord neuroanatomy as a result of thermal and electrical stimuli and motor tasks with the hands, arms and legs. Signal intensity changes detected in active areas have also been demonstrated to depend on the intensity of the stimuli with both thermal stimulation and a motor task, providing evidence of the correspondence between spinal fMRI results and neuronal activity in the spinal cord.

Animals↗

PubMed2004

Correlation of functional activation in the rat spinal cord with neuronal activation detected by immunohistochemistry.

The relationship between neuronal activity in the rat cervical and lumbar spinal cord was examined using functional magnetic resonance imaging (fMRI) and immunohistochemistry. Neuronal activity determined by c-fos staining was greatest between L4 and L6, and C5 to C7 spinal cord segments during noxious electrical stimulation of the rat hindpaw and forepaw, respectively. Areas of activity determined by fMRI are consistent with spinal cord physiology, and are predominantly found in regions of the spinal cord associated with pain, namely the dorsal horn. Activity in the ventral region of the cord was also observed, as expected. Combined results from repeated experiments demonstrated consistent areas of activity in response to stimulation, and show a high degree of reproducibility. Good correspondence was observed between functional MRI and sites of neuronal activity determined by c-fos labeling.

Afferent Pathways↗

PubMed2003

Functional MRI of the rat lumbar spinal cord involving painful stimulation and the effect of peripheral joint mobilization.

PURPOSE: To examine neuronal activation in the spinal cord due to secondary hyperalgesia resulting from intrajoint capsaicin injection, and the effect of physiotherapy manipulation, using functional magnetic resonance imaging (fMRI), in alpha-chloralose anesthetized rats. MATERIALS AND METHODS: FMRI of the rat lumbar spinal cord was performed at 9.4 Tesla. Stimuli included injection of 25 microL of capsaicin (128 microg/mL in 7.5% dimethyl sulfoxide [DMSO]) into the right forepaw or 75 microL into the right ankle joint followed by a light touch stimulus, with and without physiotherapy manipulation. RESULTS: Activation of pain areas of the spinal cord (dorsal horn) was found in all animals after injection of capsaicin into the plantar surface of the rat hindpaw and ankle joint. Overlay maps depicting activations and deactivations showed significant reproducibility between experiments. Greater overlay of activations were observed for intrajoint compared to intradermal capsaicin injection. The distribution of activations after stimulation of the hindpaw using a light touch stimulus was somewhat more varied; activation of the dorsal horn was evident, with greater overlap resulting when joint mobilization was not performed. CONCLUSION: Results suggest a trend toward decreased areas of activation in the spinal cord associated with pain, as a result of hyperalgesia, following physiotherapy joint mobilization.

Animals↗

PubMed2003

Functional MRI involving painful stimulation of the ankle and the effect of physiotherapy joint mobilization.

We examined whether cerebral activation due to secondary hyperalgesia resulting from intrajoint capsaicin injection could be detected using functional magnetic resonance imaging (fMRI) in alpha-chloralose anesthetized rats. We also examined whether we could detect analgesic changes in the central nervous system response to pain as a result of physiotherapy joint manipulation. Robust activation of areas of the brain known to be associated with the processing of pain, namely the anterior cingulate (bilateral), frontal cortex (bilateral) and sensory motor cortex (contralateral), was found in all animals following injection of 25 microl of capsaicin (128 microg/ml in 7.5% DMSO) into the plantar surface of the rat hindpaw (n = 7) and 75 microL into the ankle joint (n = 13). Significantly greater activation was observed when capsaicin was injected into the plantar surface of the hindpaw compared to the ankle joint. Mechanical allodynia and secondary hyperalgesia following capsaicin injection into the ankle joint also resulted in activation of the same brain regions. Trends toward decreased areas of activation in brain regions associated with pain in animals following physiotherapy joint mobilization were observed.

Animals↗

PubMed2003

Pain modulates cerebral activity during cognitive performance.

The present study investigates how pain modulates brain activity during the performance of a semantic cognitive task. Based on previous observations, we hypothesized that a simultaneous painful stimulus will induce an activation increase in brain regions engaged in the cognitive task. High-field BOLD-fMRI experiments were conducted on 12 young healthy subjects, using a 2 x 2 factorial design. Painful stimuli were induced by thermal hot stimulation (46-49 degrees C) on the palmar surface of the hand, using a contact thermode. Cognitive tasks consisted of either word generation (category fluency) or word repetition. Brain activity owing to the semantic tasks in the group was highly consistent with previous neuroimaging studies. When the painful stimulus was added to the cognitive task, activity in brain regions involved in semantic cognition, such as Broca's area, was increased (P < 0.01). Pain also modulated activity in brain areas not directly engaged in cognition. A positive modulation effect was observed in the midcingulate and the dorsomedial prefrontal cortex (P < 0.05). A negative modulation effect was observed in perigenual cingulate cortex, insula, and medial thalamus (P < 0.05).

Algorithms↗

PubMed2002

Functional imaging of the rat cervical spinal cord.

PURPOSE: To examine functional magnetic resonance imaging (fMRI) of the rat cervical spinal cord using painful stimulation. MATERIALS AND METHODS: fMRI of the rat cervical spinal cord was performed at 9.4 T. Stimuli included injection of 25 microL of capsaicin (128 microg/mL in 7.5% dimethylsulfoxide (DMSO)) into the right dorsal forepaw and electrical stimulation (15 V, 0.3 msec, 3 Hz) of the left dorsal forepaw. RESULTS: Activation in the dorsal horn of the spinal cord, which is known to be associated with the transmission of pain, was found in all rats (N = 4) following injection of capsaicin into the dorsal forepaw. It was possible to reproduce the pain response in a given animal several times throughout the course of an experiment, provided that sufficient time was allowed between capsaicin injections. Regions of the spinal cord associated with motor and pain response were observed in functional imaging experiments involving subcutaneous electrical stimulation of the dorsal forepaw. CONCLUSION: Spinal fMRI using electrical stimulation and capsaicin-induced painful stimulation can be a useful tool in an animal model of pain and injury.

Afferent Pathways↗