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A microphone collar for obtaining good quality recordings of animal vocalizations is described. An inexpensive, commercially available wireless microphone was modified and mounted on a collar with a hearing-aidbattery pack. The complete assembly weighs 25 g, and is readily accepted by domestic cats.
The neural mechanisms involved in the detection of natural complex sounds were studied by recording single-neuron responses from 132 cells in the primary auditory cortex of the cat. The cats were paralyzed and under neuroleptanalgesia (NLA). The cells were first stimulated with pure tones; the responses were then compared with those evoked by many different types of complex sounds, most of which were animal vocalizations. Per-stimulus-time (PST) histograms constructed from the responses to repetitive stimuli were compared with the corresponding sound spectrograms formed from the sounds used as stimuli. Of 100 cells 68 per cent gave predictable responses to complex sounds on the basis of their responses to different pure tone frequencies. In 32 per cent of the cells the responses were unpredictable. Half of these cells did not react to pure tones at all but responded to one or more animal vocalizations or generator sounds with different patterns. Some cells reacted to pure tones in quite a different way than to certain complex sounds, e.g. with inhibition instead of excitation. These results indicate that cells in the primary auditory cortex of the cat reacting in an unpredictable way to sounds with a complex structure have a more or less specialized function, in detecting and analyzing natural and other complex sound patterns. Cells reacting phasically to pure tones seem to be involved in the detection of transient sound elements.
The paper gives a short survey of the phylogenetic development of the laryngeal and supralaryngeal apparatus from amphibians to man. The increasing differentiation of vocal behaviour, paralleling the differentiation of the vocal apparatus, is outlined and special reference is made to the non-verbal component in human language. It is stressed that animal vocal repertoires can be extremely rich, but in contrast to human verbal behaviour they are generated almost exclusively by laryngeal modulations and only to a minimal degree by supralaryngeal activity (i.e. articulation). A phylogenetic development can also be seen in the cerebral organization of vocal behaviour. In amphibians, reptiles and lower mammals, the dorsal midbrain-pons transitional zone seems to be the only area responsible for the production of vocal utterances. This area probably serves in integrating vocal fold movements, expiration, intra- and extra-oral muscle activity into species-specific vocal patterns; its destruction results in mutism. In higher mammals, including man, this area does not lose its original function but is brought under the control of the cortex around the anterior sulcus cinguli (supplementary motor area and anterior cingulate gyrus). The latter seems to play an essential role in the initiation of vocal utterances in situations which do not have a rigid stimulus-response characteristic, i.e. in voluntary vocal behaviour. The highest level of voice production, finally is represented by the cortical face area, the destruction of which is without consequence to the innate vocal behaviour of animals but produces dysarthria in man. This area (together with its associated structures, such as the cortex-pontine nuclei-cerebellum-thalamus-cortex circuit) seems to be essential for the production of verbal or, more generally, learned vocal behaviour.
Both fat and glycogen are present in abundance in the larynx muscles of anurans. To clarify their role, the Musculus dilatator laryngis of the male fire-bellied toad, Bombina bombina was studied. In untreated males, the mean fat content of this larynx muscle was 14%; the muscle contained glycogen amounting to 57% of that measured in the liver tissue of the same animal. After thirteen days of continual calling activity induced by administration of a gonadotropin, the fat content fell to 6%, the glycogen to 34%. The fat content was essentially unchanged (13%) by four hours of electrical stimulation of the muscle; the glycogen content, however, had fallen to 42% after this treatment. Neither component was altered in amount by castration, the fat content being about 13% and that of glycogen, 52%. Nor did treatment with gonadotropic hormone reduce either the fat content (13%) or the amount of glycogen (59%). From these results it was concluded that fats represent a direct source of energy for the larynx muscles, which is used up gradually over long periods of calling. The glycogen in these muscles, on the other hand, is a short-term store sufficient to supply energy for only a few hours of calling activity.
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Oppositely sexed pairs of gorillas exhibit some behavior indicative of higher cognitive functioning, such as individual partner preferences and varied copulatory positions, but also mate in a cyclic manner closely related to the degree of female genital swelling. The latter finding is contrary to predictions based on their advanced position in phylogeny.
Two types of sounds produced by the cichlid fish Simochromis diagramma, are recorded and analysed. A br-r-r sound, with a main frequency of 200 Hz and a chewing sound with a main frequency of 6,000-10,000 Hz are produced during threatening; the former sound can also be heard during quivering. No sound was recorded with fighting or anxious fishes.
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Inhibition of the release call in gravid female frogs facilitates maintenance of the male's clasp so that oviposition and spawning can occur. Arginine-8 vasotocin inhibits the release call by causing an accumulation of water and internal pressure.
Behavioural experiments with Y-maze showed that phonotaxis in female crickets to male calling songs (CS) depends on the spectrum of the latter. Conservation of the first low-frequency (5 kc. p. s.) component of the spectrum is the necessary and sufficient condition for the development of normal phonotaxis. Signals which in their temporal characteristics are identical to the CS, but their spectrum contains only high-frequency (12.5 kc. p. s.) component, do no evoke positive phonotaxis. High-frequency signals (10-40 kc. p. s.) induce negative phonotaxis of females in the stationary flight. Beginning from the tympanic organ, the auditory system of crickets exhibits distinct differentiation of elements, which provide the analysis of low- and high-frequency signals. Two types of ascending interneurons transmitting information about the sound from the first auditory center to the brain were described in detail. The first type is associated mainly with low-frequency receptors and effectively transmits all that is necessary for the recognition of temporal characteristics of the CS. The second type presumably accounts for the negative phonotaxis. It is associated mainly with high-frequency receptors, exhibits for the negative phonotaxis. It is associated mainly with high-frequency receptors, exhibits significant after-effect, higher sensitivity to sounds of weak intensities, emphasizes the onset of the stimulus effect, and rapidly habituates to repetitive stimulation.
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Castration of adult male zebra finches (Poephila guttata, Estrildidae) reduces their singing rate and the tempo of song, but castrates continue to sing song identical in form to preoperative song. Injection or implantation of testosterone propionate (TP) but not of vehicle alone reverses the changes produced by castration. Castration or partial castration also reduces the frequency of courtship, copulation, and aggression. Androgen (TP) replacement reverses these changes, but control injections do not. The persistence of song after castration contrasts with the abolition of song by castration in other birds, and this may be related to the natural history of zebra finches.
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The course of several behavioural patterns could be influenced by controlling the state of the nest available to a pair of ring doves (Streptopelia risoria). These patterns were: wing-flipping, handling of nesting material, nest bowl occupancy, and nervous activities. In groups having to build nests, the onset of wing-flipping by the female occurred at a predictable time before egg-laying. It is argued that during nest-building a female influences the male to carry material to her by sitting in the nest bowl and wing-flipping. In pairs provided with a completed nest, the course of the pre-laying cycle was changed and the 'typical' sex roles did not emerge. The relationships between the male and female are discussed.
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