Bluegills were stimulated electrically while swimming free in an aquarium containing other bluegills, a mirror, gravel and food. Stimulation sites have been plotted on representative frontal sections for which a nomenclature system was developed. Nestbuilding was evoked in both sexes by stimulation near the area dorsalis telencephali pars centralis, while strong after-responses were elicited from the ventral preoptic region. Stimulation in the preoptic region slightly rostral to the habenula simultaneously inhibited aggressive behavior and evoked courtship. Feeding (snapping up prey, gravel or debris) and aggressive behavior (chasing and biting another bluegill) resulted from stimulation in the region surrounding the lateral recess of the third ventricle of the inferior lob:: of the hypothalamus. In several cases feeding and aggressive responses alternated during stimulation; a similar pattern was observed as an after-response to stimulation in the nucleus rotundus. These results are discussed with regard to possible anatomical systems controlling reproductive, feeding and aggressive behavior in fishes.Electrical stimulation of the brain in free-ranging unanesthetized birds and mammals has been used to identify areas of the telencephalon and hypothalamus associated with reproductive, feeding and aggressive behavior (Akerman, '66a,b; Harwood and Vowles, '66; Kaada, '67; Roberts et al., '67; Robinson and Mishkin, '66, '68; see Demski, '69, for additional references). Similar investigations have located some comparable regions in fishes (Fiedler, '64, '67; Grimm, '60) and amphibians (Schmidt, '68). More detailed information on the areas related to the above responses in the lower vertebrates could lead to a better understanding of the functional evolution of the forebrain. For this reason, the present mapping experiments were carried out. The bluegill sunfish was chosen as a representative species because of its availability, adaptability to the laboratory and wellstudied social behavior (Breder, '36; Miller, '63 Nieuwenhuys, '59; Tuge et al., '68), none were found that covered the entire region in a form suitable for plotting stimulation sites. For this reason, a series of representative frontal sections and a nomenclature system were developed for these areas of the bluegill brain. The indifferent lead consisted of a bare wire placed in the water of the test aquarium, Stimulation was provided by a Grass S-8 stimulator with two stimulus isolation units feeding into transistorized constant current converters modified after Bignall ('63). The output current was measured on a Hewlett-Packard 130C oscilloscope as the voltage drop across a 1000 ohm resistor in series with the fish. The stimulus used consisted of a pair of square wave pulses of opposite polarity, with a half wave duration of 1-2 msec, a frequency in the range of 2 to 100 Hz and a maximum current strength of 400 microamp. The length of the stimulation ranged from 5 sec-3 min, depending on the response being studied. MATERIALS AND METHODS Anim...

Three interrelated pallial areas mediate behaviors reflective of the cognitive and emotional aspects of the teleost mind. The dorsocentral area (Dc) has specific associations with both of the other pallial areas and projects to major lower sensorimotor centers. While Dc generally functions as an output or modulatory component of the pallium, it probably also has integrative features important for certain behaviors. The dorsolateral region (Dl) has dorsal (Dld) and ventral (Dlv) divisions. In association with the dorsal part of Dc, Dld processes visual information via a ‘tectal loop' which is hypertrophied in certain coral reef species. The region also receives afferents related to other modalities. Functionally, Dld resembles the tetrapod sensory neocortex. Anatomical and behavioral data (i.e. involvement in spatial and temporal learning) strongly suggest that Dlv is homologous to the tetrapod hippocampus. The dorsal part of the dorsomedial area (Dmd) processes acoustic, lateral line, gustatory, and multimodal information. It has reciprocal connections with Dld such that the Dmd and Dld together can be considered the teleost nonolfactory ‘sensory pallium'. Behavioral studies indicate that Dmd creates the ‘fear' necessary for defense/escape and avoidance behaviors and controls several components of species-typical sexual and aggressive behavior (responsiveness, behavioral sequencing, and aspects of social cognition). While the functional results generally support the anatomical evidence that Dmd is homologous to the tetrapod amygdala, a case can also be made that Dmd has ‘sensory neocortex-like' features. Understanding the interrelationships of Dl, Dmd, and Dc seems a necessary ‘next step' in the identification of the neural processes responsible for mental experiences such as those of a unified sensory experience (Umwelt) or of feelings of discomfort versus well- being.

This report describes the distribution of tyrosine hydroxylase immunoreactive (TH-ir) structures in the brain of the goldfish (Carassius auratus). The localization of TH-ir cell groups revealed by immunocytochemical techniques is largely in accordance with catecholamine distribution previously reported in teleosts by using monoamine fluorescence; however, in the telencephalon and diencephalon, several new cell groups are elucidated. In the telencephalon, TH-ir cell bodies are observed in the olfactory bulb, area ventralis telencephali, and the central zone of the area dorsalis telencephali. TH-ir fibers and terminals are moderately dense throughout the telencephalon except for a sparse innervation of the area dorsalis, pars medialis. Immunostained cells are present in the suprachiasmatic nucleus and magnocellular and parvicellular components of the preoptic nucleus. Immunoreactive fibers from preoptic cells can be traced caudally in two main tracts to the infundibulum. Dense immunoreactivity around cells in the pituitary provides anatomical support for catecholamine involvement in the neuroendocrine axis probably via preopticohypophysial connections. At middiencephalic levels, immunoreactive cells are present in the ventral thalamus, nucleus pretectalis periventricularis, pars ventralis, and paraventricular organ pars anterioris. In the caudal diencephalon, TH-ir cells are seen within the posterior tuberal nuclei and dorsal to posterior recess. No immunostained cells are observed in the midbrain. In the hindbrain, tyrosine hydroxylase containing cells comprise three groups similar to that described using Falck-Hillarp histofluorescence (Parent et al., '78), i.e., isthmal, central medullary, and medullospinal groups. Tyrosine hydroxylase immunoreactivity is interpreted as evidence for the presence of catecholamines and not only provides an anatomical basis for the functional significance of catecholamines in teleosts, but may be useful in elucidating homologous structures in tetrapod vertebrates, although certain sites of immunoreactivity may prove to be unique to teleosts.

Cranial nerve 0 or the terminal nerve (nervus terminahs: TN) refers to a nerve or in some cases possibly a complex of nerves that most likely derive from the olfactory placodes and relate the most anterior forebrain derivatives to nasal and olfactory structures. Such a nerve(s) has been observed in at least some stages of development in all major groups of vertebrates save myxinoids or haghsh. The phylogenetic variation of TN components is presented in some detail. The functions of TN components are not yet well identified, but some indications are that it is sensory but not chemosensory, controls blood vessels and glands in the nose and has peptide-containing fibers that may control reproductive development and behavior as well as other neural functions. This paper has three parts: (1) a historical review, which provides a conceptual framework necessary for understanding current problems in the anatomy and physiology of the TN; (2) a section on recent studies in areas selected for their potential impact on understanding the TN, and (3) a brief summary, which provides some tentative answers to the questions ‘what is the TN and what does it do?’ and suggests directions for continued research on the TN.

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