Evoked potential tone-on-tone masking patterns in the chinchilla.

Tone-on-tone masking patterns were measured in the chinchilla using the auditory evoked response from the inferior colliculus. The masker was a 2 kHz continuous tone presented at one of five levels from 20 to 70 dB SPL. The evoked response was elicited with tone bursts presented over a wide range of frequencies. Masking was defined as the difference between evoked response thresholds measured in the presence of the masker versus quiet. At low masker levels, the masking profile was symmetrical and centered around 2 kHz. However, as masker level increased, masking spread toward the high frequencies. Furthermore, at masker levels above 50 dB SPL, a low-threshold notch occurred above the masker. The masking profiles obtained with the evoked response are in good agreement with those obtained psychophysically.

A chest harness and pole-leash for routine transfer of rhesus monkeys from home cage to behavioral test apparatus and back.

A chest harness and pole-leash method to transfer rhesus monkeys (Macaca mulatta) weighing up to 16 kg from home cage to primate restraint chair was designed. The harness was made of leather straps that crossed the chest in an X-fashion, and created a V-neck. The V-neck eliminated the strangulation hazard of neck collars, and minimized interference between the harness and neck hole of restraint chairs. Two pole-leashes attached to 2 points on the harness gave the handler considerable control over the posture of the monkey, making it easier to teach the monkey to walk with a leash and to climb into its restraint chair or test apparatus. During transfer the rigid pole prevented escape and protected the handler from attack. Quick release mechanisms on the pole-leash allowed prompt, complete separation from the animal when it re-entered its home cage.