Jacob L. Dubbeldam

Brainstem Mechanisms for Feeding in Birds: Interaction or Plasticity

Starting from a functional-anatomical analysis of the feeding apparatus of a bird, some expectations are formulated regarding the organization of the neuronal systems controlling the activity of this feeding apparatus. The organization of the premotor-motor system of the jaw muscles, of the exteroceptive system conveying tactile sense from tongue and beak to the brain and of the proprioceptive system of the jaw muscles is discussed. An attempt is made to relate specific structural features of these systems to their function in the control of the different feeding patterns of birds.

Afferent Connections of Nervus facialis and Nervus glossopharyngeus in the Pigeon (Columba livia) and Their Role in Feeding Behavior

The afferent connections of the facial nerve and glossopharyngeal nerve in the pigeon have been studied with the Fink-Heimer I method after ganglion lesions. The nucleus ventrolateralis anterior of the solitary complex and an indistinct cell group S VII medial to the nucleus interpolaris of the descending trigeminal tract are the terminal fields for facial afferents. The n. ventrolateralis anterior also receives an important projection from the distal glossopharyngeal ganglion. Other projection areas of this ganglion are the n. presulcalis , n. centralis anterior, n. intermedius anterior and the parasolitary nucleus. Both ganglia have only ipsilateral projections. A lesion in the jugular ganglion complex causes degeneration throughout the ipsilateral solitary complex, in the contralateral n. commissuralis and n. centralis posterior and in the n. cuneatus externus. The lack of a substantial contribution to the trigeminal system is ascribed to the absence of mechanoreceptors in the tongue. The implications for the organization of neuronal pathways related to the feeding behavior are discussed.

The identification of the motor nuclei innervating the tongue muscles in the mallard (Anas platyrhynchos); an HRP study

Horseradish peroxidase (HRP) histochemistry was used to identify the motoneurons innervating the tongue muscles in the mallard. Four nuclei are involved: the intermediate motor nucleus of N.VII innervating the stylohyoid, serpihyoid and ceratohyoid muscles, the retrofacial nucleus of N.IX innervating the m. geniohyoideus and the n. intermedius or motor nucleus of N.XII that innervates the mm. ceratoglossus and hyoglossus anterior and obliquus. The m. intermandibularis is innervated by a trigeminal motor subnucleus. There is no clear intranuclear organization. The results are summarized in Table I and discussed in connection with the role of each of the muscles during movements of the tongue.

Do craniocervical and jaw motor nuclei receive input from the same population of reticular premotor neurons ? a double labeling tracing study in the mallard (Anas platyrhynchos)

As part of a study concerning the organization of premotor areas in the medullary reticular formation in birds we used a fluorescent retrograde double labeling technique to localize the premotor neurons of the trigeminal (mV) and supraspinal motor nucleus (SSp). Diamidino Yellow injections in mV and Fast Blue injections in SSp demonstrated that mV and SSp do not share premotor neurons, but the premotor neurons form a mixed population in the ventromedial part of the parvocellular reticular formation.

Central connections of the nucleus mesencephalicus nervi trigemini in the mallard (Anas platyrhynchosL.).

In the mallard duck, functionally distinct groups of jaw muscles are each innervated by a different subnucleus of the main trigeminal (mV) or facial (mVII) motor nucleus. The other subnuclei of mV and mVII innervate several head muscles, including lingual muscles. The reticular premotor cells of the trigeminal and facial jaw motor subnuclei occupy different areas in the parvocellular reticular formation (RPc). The cell bodies of jaw muscle spindle afferents are situated in the mesencephalic nucleus (MesV). In the present study, the central connections of MesV with jaw motor subnuclei and their premotor areas are investigated.

The Vestibular Nuclei and Vestibuloreticular Connections in the Mallard (Anas platyrhynchos L.)

The vestibular apparatus provides information about the position and movements of the head. Craniocervical muscles position the head with respect to the upper part of the neck. Motoneurons innervating these muscles are located in the supraspinal nucleus and ventral horn of the rostral cervical cord. Premotor neurons of craniocervical muscles have been found in the medial two-thirds of the medullary reticular formation: the ventromedial part of the parvocellular reticular formation and the gigantocellular reticular formation. In the present study, projections from vestibular nuclei upon craniocervical premotor neurons were investigated using anterograde and retrograde tracers. Vestibulospinal fibers run bilaterally in the medial vestibulospinal tract and ipsilaterally in the lateral vestibulospinal tract. Vestibuloreticular projections are mainly ipsilateral, and originate from the n. vestibularis lateralis pars ventralis and pars dorsalis, and from the n. vestibularis descendens. Terminal labeling is found in the border zone between the parvocellular and gigantocellular reticular formation. These projections show that in addition to direct bilateral vestibulo-craniocervical projections an indirect vestibular pathway to craniocervical motor nuclei exists. The direct pathway probably is the neural substrate for the vestibulocollic reflex, whereas the vestibular projection upon the reticular formation might influence head orientation during various kinds of activities, such as pecking, preening and so on.

Brain organization and behaviour

Central question of this essay is, whether it is possible to relate specific aspects of the organization of sensorimotor systems to specific aspects of the behaviour. The role of the auditory system as part of a system for vocalization (song-birds) or as part of a system for prey localization (owls) and the different roles of the trigeminal system in the feeding behaviour of different birds are considered. The ascending sensory systems seem to possess a comparable organization in the various species. Also the descending ‘motor’ pathways from archistriatum and paleostriatal complex seem to be basically similar. Behavioural specialization may be expressed particularly in the organization of the intratelencephalic circuits and thus in the involvement of specific regions of neostriatum and hyperstriatum ventrale. In discussions on cerebralisation it will be necessary to take such differences in intratelencephalic organization into account.

Teder behaviour (tenderness) – an exploration into the neural pathways of mild touch perception in mammals and birds

A category of teder interaction is proposed as the main source of (mutual) mild touch stimuli in higher vertebrates. The somatosensory circuits for the perception of these stimuli in mammals and birds are discussed using data from the literature. In addition to the usual somatosensory areas of the brain, in mammals mild touch signals are also conducted to the insula, which is closely connected to the limbic system. This separate processing of mild touch stimuli lends more substance to the category of teder behaviour. The comparable neuroanatomy in birds is more difficult to interpret. There are some intriguing parallels between the relevant circuits of mammals and birds, though in the telencephalic parts in particular, conclusions are limited by uncertainties as to the homologies of the mammalian and avian brains.

A reappraisal of the existence of an avian pyramidal tract, a review

This communication presents a concise overview of reports in the literature concerning the occurrence of extratelencephalic fibre tracts in birds and the comparability of these tracts with the mammalian pyramidal tract. Emphasis is on the intratelencephalic organization, in particular that of the intratelencephalic sensorimotor circuits processing information from all important types of sense organs. It is suggested that two descending tracts, the occipitomesencephalic tract and the basal tractus superficialis medialis in birds have the same role in guiding behaviour as the pyramidal pathway in mammals. However, the differences in origin, trajectory and targets suggest that two independent systems may have developed in birds. One of these, the basal tractus superficialis medialis, represents the homologue of the pyramidal tract. It is suggested that the occipitomesencephalic tract is a specific feature of birds that has developed during the evolution from the early dinosaurs to birds. This suggestion follows from recent observations on the evolution of birds.

An annotated bibliography of C.J. van der Klaauw with notes on the impact of his work

Van der Klaauw was a professor of Descriptive Zoology in the period 1934–1958. This paper presents a concise annotated overview of his publications. In his work three main topics can be recognized: comparative anatomy of the mammalian auditory region, theoretical studies about ecology and ecological morphology, and vertebrate functional morphology. In particular van der Klaauw developed new concepts on functional morphology, based upon a holistic approach. A series of studies in functional morphology of Vertebrates by his students is added. An overview of recent morphological and theoretical studies show that this new approach had a long lasting impact in studies of functional morphology.