<p>Cognitive functions in neurodegenerative diseases begin to change long before the formation of the main clinical and pathomorphological core of the disease. At the same time, patients do not show marked clinical manifestations for many years, due to the active functioning of compensatory mechanisms. Subsequently, the leading symptom complex formed on the background of decompensation becomes essentially insensitive to modern drug therapy. Thus, the search for the early signs of cognitive and neurological changes that might serve as reliable markers of the development of the neurodegenerative process is an urgent task in the diagnosis of these diseases. At present, the practical work of psychiatrists and neurologists overwhelmingly uses cognitive test batteries based on questionnaires with scale-type results for screening diagnosis of cognitive impairment; these have sufficiently high sensitivity for the advanced stages of disease but insufficient for the prodromal stages of cognitive impairment. Thus, creation of an objective screening tool for early stages of cognitive impairment able to combine efficiency and ease of use is an important and modern direction in neuroscience. The objective of this review is to analyze and summarize existing data on changes in reaction times at the onset of neurological diseases. The need for modernization of neuropsychological diagnostics by integrating sensorimotor tests with computer technologies is identified; this should increase the reliability and accessibility of screening assessments. In addition to simple reaction time (SRT), reaction indicators such as reaction time variability (RTV), choice reaction time (CRT), and reaction time dynamics are shown to be objective and independent markers of the efficiency of information processing by the nervous system.</p>