Biomedical subjects

S W Bottjer

Publications and source records attributed to S W Bottjer.

41 records · Page 3Linked to original sources

PubMed1984

Forebrain lesions disrupt development but not maintenance of song in passerine birds.

The magnocellular nucleus of the anterior neostriatum is a forebrain nucleus of passerine birds that accumulates testosterone and makes monosynaptic connections with other telencephalic nuclei that control song production in adult birds. Lesions in the magnocellular nucleus disrupted song development in juvenile male zebra finches but did not affect maintenance of stable song patterns by adult birds. These results represent an instance in which lesions of a discrete brain region during only a restricted phase in the development of a learned behavior cause permanent impairment. Because cells of the magnocellular nucleus accumulate androgens these findings raise the possibility that this learning is mediated by hormones.

Age Factors↗

PubMed1984

Sexual dimorphism and lack of seasonal changes in vocal control regions of the white-crowned sparrow brain.

The volumes of brain regions involved in vocal control were measured in adult male and female white-crowned sparrows (Zonotrichia leucophrys nuttali) captured in the summer, and in captive males held on long-day or short-day photoperiods. There is a large sex difference in the volume of two nuclei, the caudal nucleus of the hyperstriatum ventrale (HVc) and the robust nucleus of the archistriatum (RA), which correlates with a large sex difference in singing behavior. There were no differences in the size of HVc and RA in adult males held on summer or winter photoperiods, even though the 'summer' males had high androgen levels and were singing, whereas the 'winter' males had regressed testes and were not singing. The data bear on hypotheses concerning the relationship between size of brain nuclei and song learning.

Animals↗

PubMed1984

The role of feedback from the vocal organ. I. Maintenance of stereotypical vocalizations by adult zebra finches.

The stereotypical vocal patterns of adult male zebra finches (Poephila guttata) were examined before and after elimination of auditory feedback and/or feedback from the vocal organ (the syrinx). Elimination of auditory feedback was accomplished via bilateral removal of the cochleae, whereas feedback from the syrinx was eliminated by cutting hypoglossal afferent fibers while leaving hypoglossal efferents intact. Very little or no disruption of song was observed in birds which underwent deafening as well as unilateral deafferentation of the syrinx. Control experiments showed that the minor deficits observed were not attributable to lesion of pulmonary fibers in the descending branch of the vagus. There was also little deficit in song behavior of birds that were deafened and subjected to bilateral deafferentation of the syrinx. These results are consistent with the hypothesis that stable song patterns in adult passerine birds are not dependent on peripheral sources of feedback, but may be governed by a learned central control program.

Afferent Pathways↗

PubMed1982

Afferent neurons in the hypoglossal nerve of the zebra finch (Poephila guttata): localization with horseradish peroxidase.

Hypoglossal efferent fibers are known to innervate the vocal organ (syrinx) in songbirds. In order to determine the existence of afferent fibers from the syrinx in the zebra finch, horseradish peroxidase (HRP) was applied to the cut peripheral branch of the hypoglossal nerve that innervates the left side of the syrinx. Cell bodies in the ganglion of the left vagus nerve were labeled, but no transganglionic (anterograde) transport into the CNS was observed at transport intervals of 1 to 5 days. (In comparison applying HRP to the cut descending branch of the vagus produced labeled cell bodies in the vagal ganglion as well as heavy anterograde label extending into the solitary nucleus.) Injection of HRP conjugated to wheat germ agglutinin into the intrinsic syringeal muscles also labeled cell bodies in the vagal ganglion, and again no transganglionic label was observed. Application of HRP more proximally to the cut hypoglossal truck resulted in the appearance of labeled cell bodies in the vagal ganglion as well as the anterograde label extending from the descending trigeminal tract to the principal sensory nucleus of V. These results indicate that hypoglossal afferents have cell bodies in the vagal ganglion, enter the medulla dorsally with vagal fibers, and terminate in the trigeminal complex. The identification of these afferent fibers raises the important question of their role in vocal learning.

Afferent Pathways↗

PubMed1979

Food delivery as a conditional stimulus: Feature-learning and memory in pigeons.

Three experiments investigated the learning and memory of discriminations based on presence versus absence of a pre-trial food delivery. In Experiment 1 half the illuminations of a response key were followed by food regardless of the subject's behavior. In one group an extra food delivery preceded only reinforced trials (feature-positive condition), whereas in a second group it preceded only nonreinforced trials (feature-negative condition). Key pecks and approaches revealed more rapid and superior discrimination learning in the first group. Experiment 2 replicated the results of Experiment 1 but yielded no evidence that greater "unexpectedness" of pretrial food conditions facilitates discriminative performance. In Experiment 3, individual pigeons trained on a conditional discrimination exhibited a within-subject feature-positive superiority. Delay between pretrial and trial stimuli interacted with feature-positive versus feature-negative training in both the between-group (Experiment 2) and within-subject (Experiment 3) procedures: performance was decremented at both short and long delays in the feature-positive condition but was decremented only at longer delays in the feature-negative condition. The feature-positive superiority obtained here is incompatible with explanations based on either the general concept of "perceptual organization" or on the conditional nature of feature-negative discriminations.

Journal Article↗