Neuroethological studies of working and long-term (emotional) memory were conducted on 15 male rats aged 15–16 months with the Alzheimer’s disease model induced by a single intrahippocampal injection of 15 nmol/l of β-amyloid peptide 40 aggregates. The control group included 5 intact rats, representative by age and sex. The concentration of endogenous β-amyloid peptide 42 was studied in separate brain structures (neocortex, hippocampus, olfactory bulbs, and olfactory tubercles) using the immunoassay. It has been found that an increase in the content of endogenous β-amyloid peptide 42 by 27% in the hippocampus caused a decrease in working memory, namely, violation of the differentiation of the shape of objects and forgetting the familiar object. It has been shown that an increase of signal reactions in 2,2 times and a decrease of extrasignal reactions in 1,7 times while maintaining the proportion of positive conditioned reflex responses against the background of an increased level of anxiety are indicators of early manifestations of impaired long-term emotional memory.