Correlation between structural and functional changes in brain in an idiopathic headache syndrome.

Fundamental to the concept of idiopathic or primary headache, including migraine, tension-type headache and cluster headache, is the currently accepted view that these conditions are due to abnormal brain function with completely normal brain structure. Cluster headache is one such idiopathic headache with many similarities to migraine, including normal brain structure on magnetic resonance imaging and abnormal function in the hypothalamic grey matter by positron emission tomography. Given the consistency of the positron emission tomography findings with the clinical presentation, we sought to assess whether the brains of such patients were structurally normal. We used voxel-based morphometry, an objective and automated method of analyzing changes in brain structure, to study the structure of the brains of patients with cluster headache. We found a co-localization of structural changes and changes in local brain activity with positron emission tomography in the same area of the brain in the same patients. The results indicate that the current view of the neurobiology of cluster headache requires complete revision and that this periodic headache is associated with a hitherto unrecognized brain abnormality in the hypothalamic region. We believe that voxel-based morphometry has the potential to change in the most fundamental way our concept of primary headache disorders, requiring a radical reappraisal of the tenet of structural normality.

A common neural system mediating two different forms of social judgement.

BACKGROUND: A wide range of neuropsychiatric conditions, including schizophrenia and autistic spectrum disorder (ASD), are associated with impairments in social function. Previous studies have shown that individuals with schizophrenia and ASD have deficits in making a wide range of social judgements from faces, including decisions related to threat (such as judgements of approachability) and decisions not related to physical threat (such as judgements of intelligence). We have investigated healthy control participants to see whether there is a common neural system activated during such social decisions, on the basis that deficits in this system may contribute to the impairments seen in these disorders. METHOD: We investigated the neural basis of social decision making during judgements of approachability and intelligence from faces in 24 healthy participants using functional magnetic resonance imaging (fMRI). We used conjunction analysis to identify common brain regions activated during both tasks. RESULTS: Activation of the amygdala, medial prefrontal cortex, inferior prefrontal cortex and cerebellum was seen during performance of both social tasks, compared to simple gender judgements from the same stimuli. Task-specific activations were present in the dorsolateral prefrontal cortex in the intelligence task and in the inferior and middle temporal cortex in the approachability task. CONCLUSIONS: The present study identified a common network of brain regions activated during the performance of two different forms of social judgement from faces. Dysfunction of this network is likely to contribute to the broad-ranging deficits in social function seen in psychiatric disorders such as schizophrenia and ASD.

Evidence for the presence of neurokinin-1 receptors on dorsal horn spinocerebellar tract cells in the rat.

Dorsal horn spinocerebellar tract cells of adult rats were labelled by retrograde axonal transport with the B subunit of cholera toxin. Sections were prepared from lumbar and thoracic spinal segments and incubated with antisera which specifically recognise neurokinin-1 receptor protein and substance P. Labelled cells and immunoreactivity for the receptor and substance P were identified by using three different fluorophores and the relationships between them were assessed in single optical sections with three-colour confocal laser scanning microscopy. Forty-eight cells were examined and 23 of them displayed immunoreactivity for the receptor. Many substance P-immunoreactive profiles were present in lamina V and some formed contacts with spinocerebellar tract cells possessing neurokinin-1 receptor immunoreactivity. The evidence suggests that substance P may influence the activity of a subpopulation of dorsal horn spinocerebellar tract cells by acting through neurokinin-1 receptors.

Experience using central venous access for long-term hemodialysis. A new concept.

Central venous access for acute renal failure has been used for a number of years. The femoral vein and, more recently, the subclavian vein have been the routes of access. This technique has many advantages, however, it also has some significant limitations. We have recently been using a catheter for long- as well as short-term hemodialysis. The catheter is placed by means of a short incision through an opening in the internal jugular vein, and maneuvered so that the tip lies in the superior portion of the right atrium. After dialysis, the catheter is filled with heparin. The catheter then requires no additional care between between hemodialysis sessions. We have reported an experience of 50 patients in whom this catheter has been used. The complications have been remarkably few, and none were serious or fatal. At present, the patient using the catheter for the longest period of time has had it in position for approximately 19 months. We believe this technique provides a significant new choice among the ways in which hemodialysis can be achieved for short- or long-term needs.

Whose arm is it anyway? An fMRI case study of supernumerary phantom limb.

Under normal circumstances, information from a number of sources is combined to compute a unitary percept of the body. However, after pathology these influences may be perceived simultaneously, resulting in multiple dissociated conscious representations. In a recent paper, we described subject E.P., a right-handed female stroke patient with a right frontomesial lesion who sporadically experiences a supernumerary 'ghost' left arm that occupies the previous position of the real left arm after a delay of 60-90 s. We used a delayed response paradigm with functional MRI to examine the haemodynamic correlates of E.P.'s illusion. Comparison of periods of time during scanning when the ghost arm was present against when it was not revealed a single cluster (9 voxels, t = 5.11, P < 0.012 corrected for multiple comparisons) located on the right medial wall in the supplementary motor area ('SMA proper'). Our results suggest that areas traditionally classified as part of the motor system can influence the conscious perception of the body. We propose that, as a consequence of her injury, E.P. is aware of the position of the phantom limb in this 'action space' while also continuing to be aware of the true position of her real limb on the basis of afferent somatosensory information.

Variability in fMRI: an examination of intersession differences.

The results from a single functional magnetic resonance imaging session are typically reported as indicative of the subject's functional neuroanatomy. Underlying this interpretation is the implicit assumption that there are no responses specific to that particular session, i.e., that the potential variability of response between sessions is negligible. The present study sought to examine this assumption empirically. A total of 99 sessions, comprising 33 repeats of simple motor, visual, and cognitive paradigms, were collected over a period of 2 months on a single male subject. For each paradigm, the inclusion of session-by-condition interactions explained a significant amount of error variance (P < 0.05 corrected for multiple comparisons) over a model assuming a common activation magnitude across all sessions. However, many of those voxels displaying significant session-by-condition interactions were not seen in a multisession fixed-effects analysis of the same data set; i.e., they were not activated on average across all sessions. Most voxels that were both significantly variable and activated on average across all sessions did not survive a random-effects analysis (modeling between-session variance). We interpret our results as demonstrating that correct inference about subject responses to activation tasks can be derived through the use of a statistical model which accounts for both within- and between-session variance, combined with an appropriately large session sample size. If researchers have access to only a single session from a single subject, erroneous conclusions are a possibility, in that responses specific to this single session may be claimed to be typical responses for this subject.