AUDITORY FREQUENCY AND INTENSITY DISCRIMINATION IN PIGMENTED RATS

Auditory function was investigated in seven pigmented hooded rats (str ain Long-Evans) with the aid of an operant conditioning procedure. Fre quency difference limen was measured at frequencies from 0.5 to 64 kHz at 50 dB sensation level (SL). Weber ratios (frequency difference lim en/frequency) in this range varied between 3.7 and 7.3%. The decline i n the intensity of the stimulus from 50 to 10 dB SL was accompanied by a slight increase in the frequency difference limen. The frequency di fference limen values were similar for frequency shifts upwards or dow nwards. Intensity discrimination was measured at 50 dB SL at frequenci es of 2, 8 and 32 kHz. Intensity difference limen was frequency indepe ndent and amounted to 2.9+/-0.5 dB in conditions of upward intensity s hift. The values of intensity difference limen measured in conditions of downward intensity shift were significantly larger and amounted to 6.5+/-1.6 dB. The characteristics of hearing function found in these e xperiments correspond with those described by other authors in albino rats and indicate that albinism in the rat has no significant influenc e on auditory frequency and intensity discrimination.