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Biomedical subjects

H E Heffner

Publications and source records attributed to H E Heffner.

48 records · Page 3Linked to original sources
PubMed1986

Hearing loss in Japanese macaques following bilateral auditory cortex lesions.

The hearing ability of five Japanese macaques (Macaca fuscata) was assessed following two-stage bilateral auditory cortex lesions. The animals were tested using a shock-avoidance procedure with a conditioned-suppression procedure used for comparison in two cases. The animals initially were unable to respond to sound, and the first signs of hearing appeared as late as 13 wk after surgery. Hearing levels improved gradually over time, with maximal recovery reached at 24-35 wk after surgery. Recovery was most pronounced for low frequencies (63-250 Hz) and very high frequencies (32 kHz), which generally returned to normal or near-normal levels. However, the monkeys appeared to have suffered a permanent hearing loss throughout most of their hearing range, especially in the midfrequency range, where they are normally most sensitive. A review of the animal literature reveals little support for the previous view that bilateral auditory cortex lesions have little or no effect on absolute sensitivity in primates and carnivores. Most previous studies did not conduct detailed hearing tests, and those that did often noted a hearing loss. The hearing loss found in monkeys is similar to that noted in human cases following bilateral auditory cortex lesions. The current findings thus provide experimental verification of the clinical phenomenon of cortical deafness.

Adaptation, Physiological↗
PubMed1986

Effect of unilateral and bilateral auditory cortex lesions on the discrimination of vocalizations by Japanese macaques.

Ten Japanese macaques were trained to discriminate between two types of Japanese macaque coo vocalizations before and after auditory cortex ablation. Five of the animals were tested following left unilateral ablation, whereas the other five were tested following right unilateral ablation. After postoperative testing, symmetrical lesions were made in the remaining hemisphere in two animals from each group and the effect of bilateral lesions was assessed. The animals were tested using a shock avoidance procedure. Unilateral ablation of left auditory cortex consistently resulted in an initial impairment in the ability to discriminate between the vocalizations with the animals regaining normal performance in 5-15 sessions. In contrast, right unilateral ablation had no detectable effect on the discrimination. Bilateral auditory cortex ablation rendered the animals permanently unable to discriminate between the coos. Although the monkeys could learn to discriminate the coos from noise and from 2- and 4-kHz tones, they had great difficulty in discriminating between the coos and tones in the same frequency range as the coos (i.e., 500 Hz and 1 kHz). The initial impairment following left unilateral lesions indicates that the ability to perceive species-specific vocalizations is lateralized to the left hemisphere. The observation that bilateral lesions abolish the discrimination indicates that the recovery in the left lesion cases was the result of the right hemisphere mediating the discrimination.

Animals↗
PubMed1985

Hearing range of the domestic cat.

The behavioral audiograms of two cats were determined in order to establish the upper and lower hearing limits for the cat. The hearing range of the cat for sounds of 70 dB SPL extends from 48 Hz to 85 kHz, giving it one of the broadest hearing ranges among mammals. Analysis suggests that cats evolved extended high-frequency hearing without sacrifice of low-frequency hearing.

Animals↗
PubMed1985

Sound localization in wild Norway rats (Rattus norvegicus).

The ability of three wild Norway rats to localize sound was determined for single clicks and 100-ms white noise bursts. Chance level localization thresholds were 12 degrees for clicks and 9.7 degrees for white noise. A comparison of these results with published localization thresholds for the domestic albino rat yielded no significant differences. It appears that the combined effects of domestication and albinism have not affected the ability of the laboratory rat to localize sound. Instead, the relatively poor localization acuity of these rats appears to be part of the normal variation in sound localization acuity found among different species of mammals.

Animals↗
PubMed1985

Hearing in two cricetid rodents: wood rat (Neotoma floridana) and grasshopper mouse (Onychomys leucogaster).

The audiograms of two wood rats and three grasshopper mice were determined with a conditioned avoidance procedure. The wood rats were able to hear tones from 940 Hz to 56 kHz at a level of 60 dB (SPL), with their best sensitivity of -3 dB occurring at 8 kHz. The hearing of the grasshopper mice ranged from 1.85 kHz to 69 kHz at 60 dB (SPL), with their best sensitivity of 9 dB also occurring at 8 kHz. These results support the relation between interaural distance and high-frequency hearing and between high- and low-frequency hearing. The inability of the grasshopper mouse to hear low frequencies as well as other desert rodents such as kangaroo rats and gerbils demonstrates that not all rodents found in deserts have developed good low-frequency hearing. The degree to which general and specific selective pressures have played a role in the evolution of rodent hearing is discussed.

Animals↗
PubMed1984

Hearing loss in dogs after lesions of the brachium of the inferior colliculus and medial geniculate.

Seven dogs were tested for their sensitivity to pure tones following lesions of the brachium of the inferior colliculus and medial geniculate body. Bilateral section of the brachium of the inferior colliculus consistently resulted in an average hearing loss of as much as 37 dB in the midrange of the animals' audiograms. Lesions of the medial geniculate appear to produce a similar hearing loss if the ventral division of the medial geniculate is completely destroyed.

Animals↗
PubMed1984

Temporal lobe lesions and perception of species-specific vocalizations by macaques.

Japanese macaques were trained to discriminate two forms of their coo vocalization before and after unilateral and bilateral ablation of the temporal cortex. Unilateral ablation of the left superior temporal gyrus, including auditory cortex, resulted in an initial impairment in the discrimination, but similar unilateral ablation of the right superior temporal gyrus had no effect. Bilateral temporal lesions including auditory cortex completely abolished the ability of the animals to discriminate their coos. Neither unilateral nor bilateral ablation of cortex dorsal to and sparing the auditory cortex had any effect on the discrimination. The perception of species-specific vocalizations by Japanese macaques seems to be mediated by the temporal cortex, with the left hemisphere playing a predominant role.

Animals↗
PubMed1984

Sound localization in large mammals: localization of complex sounds by horses.

The idea that large mammals localize sounds more accurately than small mammals has been noted frequently and is usually explained by reference to their large interaural distance and the correspondingly broad binaural time (delta t) and spectral (delta fi) differences between their two ears. Sound-localization thresholds for single clicks and 100-ms noise bursts were determined for horses, and the magnitude of the binaural time (delta t) and spectral (delta fi) cues for sound direction were measured on a horse. Although horses have relatively large interaural distances and physically broad binaural-localization cues available to them, their sound direction thresholds were markedly poorer than those of other large mammals--averaging 22 degrees for noise and 30 degrees for clicks. It appears that sound-localization acuity is not determined simply by the physical availability of binaural cues.

Animals↗
PubMed1983

Occurrence of the cattle ear mite (Raillietia auris) in southeastern Kansas.

Forty-seven cattle from 8 separate herds in southeastern Kansas were examined for ear mites (Raillietia auris). Ear mites were directly observed in 12 of the animals while 19 others showed signs of infestation consisting of ulceration and blockage of the auditory canal by a thick plug of pus. The observed occurrence of infestation in 66 percent of the animals examined is higher than expected based on previous reports.

Animals↗
PubMed1982

Hearing in the elephant (Elephas maximus): absolute sensitivity, frequency discrimination, and sound localization.

A young Indian elephant was tested to determine its absolute sensitivity, frequency-discrimination thresholds, and sound-localization thresholds. The elephant was found to have an audibility curve similar to that of other mammals but one that is more sensitive to low frequencies and less sensitive to high frequencies than any other mammalian audiogram including human's. The elephant's sensitivity to frequency differences at low frequencies was found to equal that of humans. Finally, the elephant was found to be very accurate at localizing sounds in the azimuthal plane, with thresholds around 1 degree for broad-band noise. The elephant's ability to localize pure tones suggested that it could use both binaural time- and intensity-difference cues to localize sound.

Animals↗
PubMed1976

Evoked unit activity in auditory cortex of monkeys performing a selective attention task.

Single-unit responses were recorded from the auditory cortex of rhesus monkeys performing a selective atteintion task which used combined light and sound stimuli. The animals were first trained to push a lever to the left for a noise burst and to the right for a tone burst, and then trained to push left for a left light and right for a right light. Subsequently, one of the four possible light and sound stimulus combinations (Noise + Left Light, Noise + Right Light, Tone + Left Light, Tone + Right Light) was randomly presented on each trial. In blocks of 100 trials only one part of the combined stimulus (either the light or the sound) determined the direction of lever push that would be reinforced. Responses of single units to identical sound stimuli were compared for blocks in which sound was the relevant cue and blocks in which light was the relevant cue. Typically, differences were in response strength without alteration of response pattern. Even the earliest response components (15-20 msec latency) could show changes. Two-thirds of the response comparisons showed differences in strength depending upon whether sound or light was the relevant cue, with about as many responses stronger for light relevant as for sound relevant. Independent of which modality was relevant, unit responses for trials in which both parts of the combined light and sound stimulus indicated the same direction of lever push were generally stronger than unit responses for trials in which the two parts of the combined stimulus signalled opposite directions of lever pushes.

Animals↗