Frequency transfer properties of three distinct types of cat horizontal cells

Intracellular responses of horizontal cells in the retina were recorded from the intact eye in situ of anesthetized and paralyzed cats. The responses to large (15 X 15 degrees) high modulation (0.6-0.9) photopic (140-200 cd/m2) sinewave light stimuli could be grouped unequivocally into three distinct classes on the basis of the critical flicker frequency (CFF); Hn-units had a CEF of 25-40 Hz, hm-units of 55-70 Hz and Hw-units of 95-110 Hz. For some stimulus situations small oscillations could be seen in Hm-responses (resonance frequency of about 43 Hz) and Hw-responses (resonance frequency 95 Hz). Hn-responses never showed such an oscillatory tendency. Frequency transfer functions are presented for the three types of H-units and a phenomenological model is discussed that describes these results quantitatively.