Drifting sinusoidal gratings, moving bars, and moving spots were emplo
yed to study the direction sensitivity of 425 neurons in the A laminae
of the cat's LGNd. Thirty-two percent of X- and Y-type LGNd relay cel
ls exhibit significant direction sensitivity when tested with drifting
sinusoidal gratings. X and Y cells exhibit the same degree of directi
on sensitivity. Moving spots and bars elicit direction specific respon
ses from LGNd cells that are consistent with those elicited when drift
ing sinusoidal gratings are employed. For cells that are both orientat
ion and direction sensitive, the preferred direction tends to be ortho
gonal to the preferred orientation. In general, direction sensitivity
is strongest at relatively low spatial frequencies, well below the spa
tial-frequency cutoff for the cell. The presence of significant number
s of direction-sensitive LGNd cells raises the possibility that subcor
tical direction specificity is important for the generation of this pr
operty in the visual cortex.