The Evolution of the Nervous system: Invertebrates vs. Vertebrates

NERVOUS SYSTEM FUNCTIONS, EVOLUTIVE PATTERN , AND RELATIONSHIP WITH SOME NEURODEGENERATIVE CONDITION: The nervous system directs and coordinates our movements. It receives stimuli from the environment around us and from all our internal organs. It interprets these stimuli and elaborates responses, which are transmitted to muscles or glands.To compare the nervous systems of invertebrates to vertebrates and between the various vertebrates Can be an useful instrument in field fo neuroscience, molecular biology, forensic science, and pharmacology, regenerative medicine. Why in example some neuronal circuits in superior vertebrates cross themselves like decussatio pyramid or in optical chiasm?And why in brain vs spinal cord grey matter and white matter are inverse (opposite)? And this fact make possible to verify relationship between degenerative pathology of cortex vs spinal cord under an evolutive approach. And this cam be related also to the "brain and spinal cord wasting system" functionality? Is universally knowed that different neurodegenerative disease involved different CNS parts: cortex( DA), PD(basal nuclei), ALS spinal cord preferentially.