Age-related regional cerebral atrophy was evaluated in a small lissencephalic primate, model of cerebral aging. Twelve mouse lemurs (Microcebus murinus), ages 1.9 -10.9 years (maximum life span: 12 years), were studied. 3D inversion-recovery fast spin-echo MR images (isotropic resolution ‫؍‬ 234 m) were recorded at 4.7 T with a surface coil actively decoupled from the transmitting birdcage probe. The surface coil-related sensitivity gradient was corrected by normalization with images from an agar and NaCl phantom. An automatic statistical segmentation technique based on a classification-maximization algorithm was tested on digital phantoms that mimicked the brain and applied to the 3D brain images. Segmented 3D maps that displayed gray matter, white matter, and cerebro-spinal fluid (CSF) voxels were computed. The ventricles and peri-encephalic spaces were categorized into 14 regions, defined on brain atlases on the basis of cytoarchitectural and anatomical criteria. The volume of CSF voxels belonging to each of these regions was calculated as an index of regional atrophy. Dilation of the mammillary fossa was an early event in the aging process. CSF accumulation within the occipital, parieto-temporal, temporal, and frontal ventral peri-encephalic spaces was particularly marked in the oldest animals that also displayed ophthalmologic alterations.Magn Reson Med 50:984 -992, 2003.

SummaryMuscle spindles provide proprioceptive feedback supporting normal patterns of motor activity and kinesthetic sensibility. During mastication, jaw muscle spindles play an important role in monitoring and regulating the chewing cycle and the bite forces generated during mastication. Both acute and chronic orofacial pain disorders are associated with changes in proprioceptive feedback and motor function. Experimental jaw muscle pain also alters the normal response of masseter spindle afferents to ramp and hold jaw movements [1]. It has been proposed that altered motor function and proprioceptive input results from group III muscle afferent modulation of the fusimotor system which alters spindle afferent sensitivity in limb muscles [2]. The response to nociceptive stimuli may enhance or reduce the response of spindle afferents to proprioceptive stimuli. Several experimental observations suggesting the possibility that a similar mechanism also functions in jaw muscles are presented in this report. First, evidence is provided to show that nociceptive stimulation of the masseter muscle primarily influences the amplitude sensitivity of spindle afferents with relatively little effect on the dynamic sensitivity [3]. Second, reversible inactivation of the caudal trigeminal nuclei attenuates the nociceptive modulation of spindle afferents. Finally, functionally identified gamma-motoneurons in the trigeminal motor nucleus are modulated by intramuscular injection with algesic substances. Taken together, these results suggest that pain-induced modulation of spindle afferent responses are mediated by small diameter muscle afferents and that this modulation is dependent, in part, on the relay of muscle nociceptive information from trigeminal subnucleus caudalis onto trigeminal gamma-motoneurons. The implication of these results will be considered in light of current theories on the relationship between jaw muscle pain and oral motor function.

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Current auscultation training systems reproduce physiologic sounds routinely heard during patient examination; however, they do not capture, model and reproduce auditory/spatial physician‐patient interactions as immersive learning experiences. We hypothesize a schema for the capture and replay of diagnostic sound patterns and spatial coordination as exemplified by stethoscope placement coupled with the synched viewing of 3D CT anatomy that would significantly increase clinical insight and recall. Our simulation system digitally captures actual physician‐patient auscultation experiences as thoracic sound combinations, stethoscope head coordinate positions within a standardized space, and diagnostic signs and impressions as dictated by the examining physician. This is accomplished using an electronic stethoscope with spatial tracking capabilities and a laptop computer. This multimedia experiential “case profile” is then additionally enhanced via 3D CT/MRI visualizations synchronized with stethoscope head placement location patterns. Finally, our training system is able to replay this coordinated experience to students interactively using fellow students registered to the standard anatomic space.

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