Features of the auditory development of the short-tailed Brazilian opossum, Monodelphis domestica: evoked responses, neonatal vocalizations and synapses in the inferior colliculus.

The onset of hearing in anesthetized South American opossums (Monodelphis domestica) was determined by the measurement of evoked potentials to click stimuli from the vertex of the skull immediately over the inferior colliculus. Evoked potentials were first recorded at postnatal day 24 at a threshold of 83 dB SPL; thresholds declined over subsequent weeks to below 58 dB at 40 days. Isolation calls emitted by the pups had stereotypic spectra with peaks at near 13 kHz and an octave higher.

Proprioceptive versus visual control in autistic children.

The autistic child's presumed preference for proximal rather than distal sensory input was studied by requiring that autistic, retarded, and normal subjects adapt to a prism-induced lateral displacement of the visual field. Only autistic subjects demonstrated transfer of adaptation to the nonadapted hand, indicative of a reliance on proprioception rather than vision to accomplish adaptation. Such reliance on proprioception was explained as an alternative strategy compensating for an inability to use current visual control of reaching rather than as a preference for proximal information per se.

Auditory sensitivity of the albino rat.

The auditory sensitivity of the (Sprague-Dawley strain) albino rat was determined by the conditioned suppression technique. The three animals tested were found to have a range of hearing from 250 Hz to 80 kHz at 70 dB (SPL). They were most sensitive to tones of 8 kHz but were almost as sensitive at 38 kHz.

Contribution of auditory cortex to sound localization in the monkey (Macaca mulatta).

Monkeys with lesions of auditory cortex were tested for their ability to localize the source of brief sounds. Although those deprived of primary auditory cortex bilaterally were able to indicate the direction of a sound with near-normal acuity, they were unable to locate its source. This dissociation of abilities suggest that the role of auditory cortex in sound localization is not so much sensory or perceptual as it is auditomotor or associative.