Psychologists: study behavior...
PhD or PsyD in an area of psychology

Neuropsychologists: study brain-behavior relationships
Doctoral degree and specialization training

Neurologists: identify and treat disorders of the nervous system (ie, anatomy)
Premed, MD, residency in neurology

Neuropsychiatrists: are concerned with organic aspects of mental disorders
MD, residency in psychiatry, specialization

Neurosurgeons: specialize in surgery of nervous system structures
MD, residency in surgery, specialized training

Neuroscientists: are interested in composition and function of the NS
doctorate in psychology or biology and research/teaching experience