Distinguishing subregions of the human MT+ complex using visual fields and pursuit eye movements

In humans, functional imaging studies have demonstrated a homologue of the macaque motion complex, MT+ [suggested to contain both middle temporal (MT) and medial superior temporal (MST)], in the ascending limb of the inferior temporal sulcus. In the macaque monkey, motion-sensitive areas MT and MST are adjacent in the superior temporal sulcus. Electrophysiological research has demonstrated that while MT receptive fields primarily encode the contralateral visual field, MST dorsal (MSTd) receptive fields extend well into the ipsilateral visual field. Additionally, macaque MST has been shown to receive extraretinal smooth-pursuit eye-movement signals, whereas MT does not. We used functional magnetic resonance imaging (fMRI) and the neural properties that had been observed in monkeys to distinguish putative human areas MT from MST. Optic flow stimuli placed in the full field, or contralateral field only, produced a large cluster of functional activation in our subjects consistent with previous reports of human area MT+. Ipsilateral optic flow stimuli limited to the peripheral retina produced activation only in an anterior subsection of the MT+ complex, likely corresponding to putative MSTd. During visual pursuit of a single target, a large portion of the MT+ complex was activated. However, during nonvisual pursuit, only the anterolateral portion of the MT+ complex was activated. This subsection of the MT+ cluster could correspond to putative MSTl (lateral). In summary, we observed three distinct subregions of the human MT+ complex that were arranged in a manner similar to that seen in the monkey.     

Pulmonary protective mechanisms in human infants

The flow of oral and nasal secretions into the pharynx is a recognized source of pulmonary aspiration during sleep in infants and adults alike. Such aspiration probably accounts for many cases of bacterial pneumonia. In infants, swallowing occurs frequently in sleep, and the rate of swallowing appears to be far greater than that of the sleeping adult. Such swallowing during sleep appears to be the major mechanism whereby oral and nasal secretions are transported to the digestive tract. Certain aspects of those swallows, such as "swallow-breaths" and their coordination with the respiratory cycle, have been documented. A brief period of airway closure is always seen during such nonfeeding swallows. Nonfeeding swallows are usually seen during mixed and obstructive apneic spells in preterm infants. The underlying reflex mechanisms responsible for such swallows during apnea are unclear. During ordinary postfeeding regurgitation, upper airway closure and swallowing occur in close temporal sequence. These events appear to be major mechanisms of airway protection during regurgitation. In certain infants, regurgitation and prolonged apnea often occur simultaneously. The mechanism underlying their association is unclear but may involve laryngeal chemoreceptors.     

Sampling density compensation in MRI: rationale and an iterative numerical solution.

Data collection of MRI which is sampled nonuniformly in k-space is often interpolated onto a Cartesian grid for fast reconstruction. The collected data must be properly weighted before interpolation, for accurate reconstruction. We propose a criterion for choosing the weighting function necessary to compensate for nonuniform sampling density. A numerical iterative method to find a weighting function that meets that criterion is also given. This method uses only the coordinates of the sampled data; unlike previous methods, it does not require knowledge of the trajectories and can easily handle trajectories that "cross" in k-space. Moreover, the method can handle sampling patterns that are undersampled in some regions of k-space and does not require a post-gridding density correction. Weighting functions for various data collection strategies are shown. Synthesized and collected in vivo data also illustrate aspects of this method.     

Canadian guidelines for economic evaluation of pharmaceuticals. Canadian Collaborative Workshop for Pharmacoeconomics

In 1994, Canada became the second country to release national guidelines for the economic evaluation of pharmaceuticals. The guidelines were developed over a period of 18 months through an elaborate process of broad consultation with a wide variety of relevant stakeholders. The intent of the guidelines is to provide guidance to doers and users of studies, by laying out the general 'state of the art' regarding methods, and by providing specific methodological advice on many matters. The aim is to improve the scientific quality and integrity of studies, and to enhance consistency and comparability across studies. This article presents the Canadian guidelines, both in summary and in detail. Because the techniques of economic evaluation are widely applicable beyond pharmaceuticals, the guidelines will be of interest to researchers and decision makers in all fields of healthcare. Because the methods are not country specific, the guidelines will be of interest to those in other countries as well as in Canada.     

Endoscopic carpal tunnel release: a single-portal technique

A safe single-portal technique for performing endoscopic carpal tunnel release is described. The procedure can be done using equipment already available in any standard operating room. Evaluation of 100 cases done by the author using this method has shown encouraging results.