NTRK2 and amyotrophic lateral sclerosis: These studies collectively do not present a consistent picture of BDNF and TrkB changes in ALS, and sometimes BDNF and TrkB levels change in opposite directions in the same studies, which has been interpreted as dysregulated or abnormal TrkB/BDNF signaling (Just-Borras et al., 2019; Rei et al., 2022).