The Organization and Evolution of Dorsal Stream Multisensory Motor Pathways in Primates

In Prosimian primates, New World monkeys, and Old World monkeys microstimulation with half second trains of electrical pulses identifies separate zones in posterior parietal cortex (PPC) where reaching, defensive, grasping, and other complex movements can be evoked. Each functional zone receives a different pattern of visual and somatosensory inputs, and projects preferentially to functionally matched parts of motor and premotor cortex. As PPC is a relatively small portion of cortex in most mammals, including the close relatives of primates, we suggest that a larger, more significant PPC emerged with the first primates as a region where several ethologically relevant behaviors could be initiated by sensory and intrinsic signals, and mediated via connections with premotor and motor cortex. While several classes of PPC modules appear to be retained by all primates, elaboration and differentiation of these modules likely occurred in some primates, especially humans

The role of cholinergic and serotonergic neocortical projections in controlling skilled movement in rats : evaluation of a model of dementia

vii, 166 leaves : ill. ; 28 cm.The ascending cholinergic and serotonergic projections are central to cortical activation and normal behavior. The objective of this thesis was to determine whether unilaterally damaging both of these systems would disrupt the production of skilled movements on the contralateral side of the body. Rats received unilateral damage to either the ascending cholinergic, or serotonergic, or both projections. The respective lesions reduced neocortical leveles of acetylcholine and serotonin as assessed by acetylcholinesterase reactivity and immunohistochemical staining for serotonin. Subjects were assessed on a battery of sensorimotor tasks sensitive to neocortical integrity. The cholinergic lesion produced mild deficits on some taks but damage to both together did not abolish skilled movement. The impairments are decreased in relation to the severe effects of bilateral lesions. The results show that the sensorimotor cortex remains functional following deafferentation of both cholinergic and serotonergic afferents

Modeling middle cerebral artery stroke in rats : an examination of the skilled reaching impairments

xiii, 345 leaves : ill. ; 29 cm. + 1 CD-ROMMiddle cerebral artery (MCA) stroke can produce chronic incapacitating motor impairments. Understanding the neural basis of the motor syndromes is complicated by the diversity of neural structures damaged but the problem can be addressed in laboratory rats by inducing selective infarcts. Nevertheless, the motor syndromes that ensue from stroke in rats remain poorly understood and undermine its potential as a model for clinical stroke. The objective of the present thesis was to document the skilled reaching impairments from neocortical and subcortical MCA infarcts in rats. In addition, the integrity of the motor system components spared by the infarct was assessed neurophysiologically and neuroanatomically. Characteristic reaching impairments emerged from each infarct but there were also some overlapping features that might be explained by neural dysfunction extending beyond the boundaries of the infarct. The present studies showed that the laboratory rat is an ideal animal model for studying stroke, which should be of interest to both clinical and research scientists studying stroke