N Schluter | PubMed Health

PubMed1998

How do visual instructions influence the motor system?

The paper distinguishes the use of visual cues to guide reaching and grasping, and the ability to learn to associate arbitrary sensory cues with movements. Using positron emission tomography (PET), we have shown that the arbitrary association of visual cues and movements involves the ventral visual system (prestriate, inferotemporal and ventral prefrontal cortex), the basal ganglia and the dorsal premotor cortex. Using functional magnetic resonance imaging (fMRI), we have shown that the evoked haemodynamic responses in the ventral visual system are time-locked to the presentation of the visual cues, that the response in the motor cortex is locked to the time of response, and that the response in the dorsal premotor cortex shows cuerelated, movement-related and set-related components. Using PET we have shown that there are learning-related changes in activation in both the ventral prestriate cortex and the basal ganglia (globus pallidus) when subjects learn a visuomotor associative task. We argue that the basal ganglia may act as a flexible system for learning the association of sensory cues and movements.

Humans↗

PubMed1985

Vasopressin neuron survival in neonatal Brattleboro rats; critical factors in graft development and innervation of the host brain.

Previously it was found that grafts of supraoptic plus paraventricular areas from 19-day-old foetal normal rats survived in the third ventricle of the brain of 4- to 6-day-old, vasopressin-deficient Brattleboro pups, but could not alleviate their polyuria. In the present series, factors important in graft development were analysed. Again using day-19 fetuses as donors, anterohypothalamus grafts as well as grafts placed near a crushed median eminence survived relatively poorly, but showed the presence of vasopressin neurons immunocytochemically one month post-grafting. Homotopic grafting in the supraoptic nucleus, however, even failed to show surviving vasopressin neurons. Graft survival was improved by the use of donor tissue of fetuses younger than day 19. Parvocellular vasopressin cells were frequently seen, organized into clusters resembling the normal suprachiasmatic nucleus. However, magnocellular neurons, as normally seen in supraoptic and paraventricular nuclei, only survived grafting when taken between days 11 and 15 of fetal age. It was concluded that only immature vasopressin neurons survived grafting under the condition employed. Magnocellular neurons had a limited fiber outgrowth into the host brain and median eminence. Most large neurons only stained with non-specific neurophysin antiserum, not with specific vasopressin-associated neurophysin antiserum. Thin fibers of the parvocellular vasopressin neurons provided only occasional and sparse innervation of the host median eminence and lateral septum (one case), but several examples of massive fiber bundles running dorsally from graft into host brain were observed. These fibers terminated in the thalamic periventricular area, a nucleus that is normally innervated by the vasopressin neurons of the suprachiasmatic nucleus. The failure of the grafts to provide adequate vasopressinergic innervation of the host median eminence probably explains why none of the nearly 200 Brattleboro neonates operated upon showed any sign of relief of their diabetes insipidus. It suggests, however, that the present procedures might be useful in restoring central vasopressinergic functions in the developing Brattleboro rat.

Aging↗

PubMed1984

A procedure for small-volume brain grafting; vasopressin cells in neonatal and adult Brattleboro rats.

A simple and reliable technique is described for the transplantation of fetal vasopressin (VP) neurons in the third ventricle of the brain of homozygous Brattleboro neonates. Small-volume grafting is introduced by microdissection of paraventricular and supraoptic areas and by pelleting the minced tissue for insertion into the transplantation cannula. Morphological and immunocytochemical evaluation yielded results in both neonatal and adult host brain that were similar to those described for anterior hypothalamic grafts in adult Brattleboro brain. The present protocol circumvents some of the general problems encountered when the use of small grafts is imperative, and is also applicable to the implantation of pelleted cell suspensions.

Animals↗