Bidirectional cells are a subset of neurons found in mammalian brains in region MT. They are characterised by having a peak response to visual motion in two, opposing, directions. They were discovered in 1984 by Albright et al.[1][2]
^Albright, Thomas D.; Desimone, R.; Gross, C. G. (January 1984). "Columnar organization of directionally selective cells in visual area MT of the macaque". Journal of Neurophysiology. 51 (1): 16–31. doi:10.1152/jn.1984.51.1.16. ISSN0022-3077. PMID6693933.