DIRECTION-SENSITIVE X-CELL AND Y-CELL WITHIN THE A-LAMINAE OF THE CATS LGND

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.