The current state-of-the-art of spinal cord imaging: methods.

A first-ever spinal cord imaging meeting was sponsored by the International Spinal Research Trust and the Wings for Life Foundation with the aim of identifying the current state-of-the-art of spinal cord imaging, the current greatest challenges, and greatest needs for future development. This meeting was attended by a small group of invited experts spanning all aspects of spinal cord imaging from basic research to clinical practice. The greatest current challenges for spinal cord imaging were identified as arising from the imaging environment itself; difficult imaging environment created by the bone surrounding the spinal canal, physiological motion of the cord and adjacent tissues, and small cross-sectional dimensions of the spinal cord, exacerbated by metallic implants often present in injured patients. Challenges were also identified as a result of a lack of "critical mass" of researchers taking on the development of spinal cord imaging, affecting both the rate of progress in the field, and the demand for equipment and software to manufacturers to produce the necessary tools. Here we define the current state-of-the-art of spinal cord imaging, discuss the underlying theory and challenges, and present the evidence for the current and potential power of these methods. In two review papers (part I and part II), we propose that the challenges can be overcome with advances in methods, improving availability and effectiveness of methods, and linking existing researchers to create the necessary scientific and clinical network to advance the rate of progress and impact of the research

Ipsilateral involvement of primary motor cortex during motor imagery

To investigate whether motor imagery involves ipsilateral cortical regions, we studied haemodynamic changes in portions of the motor cortex of 14 right-handed volunteers during actual motor performance (MP) and kinesthetic motor imagery (MI) of simple sequences of unilateral left or right finger movements, using functional magnetic resonance imaging (fMRI). Increases in mean normalized fMRI signal intensities over values obtained during the control (visual imagery) task were found during both MP and MI in the posterior part of the precentral gyrus and supplementary motor area, both on the contralateral and ipsilateral hemispheres. In the left lateral premotor cortex, fMRI signals were increased during imagery of either left or right finger movements. Ipsilateral cortical clusters displaying fMRI signal changes during both MP and MI were identified by correlation analyses in 10 out of 14 subjects; their extent was larger in the left hemisphere. A larger cortical population involved during both contralateral MP and MI was found in all subjects. The overall spatial extent of both the contralateral and the ipsilateral MP + MI clusters was similar to 90% of the whole cortical volume activated during MP. These results suggest that overlapping neural networks in motor and premotor cortex of the contralateral and ipsilateral hemispheres are involved during imagery and execution of simple motor tasks

Temporal and intensity coding of pain in human cortex

We used a high-resolution functional magnetic resonance imaging (fMRI) technique in healthy right-handed volunteers to demonstrate cortical areas displaying changes of activity significantly related to the time profile of the perceived intensity of experimental somatic pain over the course of several minutes. Twenty-four subjects (ascorbic acid group) received a subcutaneous injection of a dilute ascorbic acid solution into the dorsum of one foot, inducing prolonged burning pain (peak pain intensity on a 0-100 scale: 48 +/- 3, mean +/- SE; duration: 11.9 +/- 0.8 min). fMRI data sets were continuously acquired for similar to 20 min, beginning 5 min before and lasting 15 min after the onset of stimulation, from two sagittal planes on the medial hemispheric wall contralateral to the stimulated site, including the cingulate cortex and the putative foot representation area of the primary somatosensory cortex (SI). Neural clusters whose fMRI signal time courses were positively or negatively correlated (P < 0.0005) with the individual pain intensity curve were identified by cross-correlation statistics in all 24 volunteers. The spatial extent of the identified clusters was linearly related (P < 0.0001) to peak pain intensity. Regional analyses showed that positively correlated clusters were present in the majority of subjects in ST, cingulate, motor, and premotor cortex. Negative correlations were found predominantly in medial parietal, perigenual cingulate, and medial prefrontal regions. To test whether these neural changes were due to aspecific arousal or emotional reactions, related either to anticipation or presence of pain, fMRI experiments were performed with the same protocol in two additional groups of volunteers, subjected either to subcutaneous saline injection (saline: n = 16), inducing mild short-lasting pain (peak pain intensity 23 +/- 4; duration 2.8 +/- 0.6 min) or to nonnoxious mechanical stimulation of the skin (controls: n = 16) at the same body site. Subjects did not know in advance which stimulus would occur. The spatial extent of neural clusters whose signal time courses were positively or negatively correlated with the mean pain intensity curve of subjects injected with ascorbic acid was significantly larger (P < 0.001) in the ascorbic acid group than both saline and controls, suggesting that the observed responses were specifically related to pain intensity and duration. These findings reveal distributed cortical systems, including parietal areas as well as cingulate and frontal regions, involved in dynamic encoding of pain intensity over time, a process of great biological and clinical relevance

Functional activity mapping of the mesial hemispheric wall during anticipation of pain

The relative contributions of autonomic arousal and of cognitive processing to cortical activity during anticipation of pain, and the role of changes in thalamic outflow, are still largely unknown. To address these issues, we investigated with functional magnetic resonance imaging (fMRI) the activity of the contralateral mesial hemispheric wall in 56 healthy volunteers while they expected the stimulation of one foot, which could be either painful or innocuous. The waiting period was characterized by emotional arousal, a moderate rise in heart rate, and by increases in mean fMRI signals in the medial thalamus, mid- and posterior cingulate cortex, and in the putative foot area of the primary somatosensory and motor cortex. The same brain regions, excepting posterior cingulate, were also activated by somatosensory stimulation. We identified by cross-correlation analysis a cluster population whose fMRI signal time course was related to the mean heart rate (HR) profile, showing selective changes of activity during the waiting period. Positively correlated clusters were found mainly in sensorimotor areas, mid- and posterior cingulate, and dorsomedial prefrontal cortex. Negatively correlated clusters predominated in the perigenual anterior cingulate and ventromedial prefrontal cortex. HR clusters had different characteristics from, and showed limited spatial overlap with, clusters whose fMRI signals were related to the psychophysical pain intensity profile; however, both cluster populations were affected by anticipation. These findings unravel a complex pattern of brain activity during uncertain anticipation of noxious input, likely related both to changes in the level of arousal and to cognitive modulation of the pain system. (C) 2003 Elsevier Science (USA). All rights reserved