The Pallium and Mind/Behavior Relationships in Teleost Fishes

Abstract

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.

Cytoarchitecture of the Telencephalon in the Coral Reef Multiband Butterflyfish (<b><i>Chaetodon multicinctus</i></b>: Perciformes)

“…The function of the enlarged Dc of butterflyfishes is unknown. The dorsal division of the enlarged Dc of reef-dwelling squirrelfishes (non-perciform fishes) is important for visual processing [Demski, 2013]. This region is likely homologous to the caudal portion of the Dc1 or part of the Dc2 in C. multicinctus.…”

“…While the visual system of C. multicinctus is well developed [Losey et al, 2003] and clearly important for social communication [Fricke, 1986], it is unlikely to be the sole reason for the hypertrophied Dc. Neuroanatomical tracing studies indicate that the Dc is interconnected with the OB, tectum, torus semicircularis, cerebellum and hypothalamus as well as many other telencephalic and diencephalic regions [reviewed in Demski, 2013]. These studies underscore the potential importance of this region for behavioral modulation and multimodal stimulus processing.…”

The Integration of Sociality, Monoamines, and Stress Neuroendocrinology in Fish Models: Applications in the Neurosciences

“…Based on topology, hodology, and expression of receptors for sexual hormones, O'Connell & Hofmann (2011b) proposed direct one-to-one homologs of the periaqueductal gray area and POA in fish, and the anterior and ventral tuberal regions as homologues for anterior and ventromedial hypothalamus, respectively; these structures would comprise the social behaviour network in fish. In the mesolimbic reward system, homologues have been proposed for the basolateral (pallial) amygdala (= dorsomedial telencephalon, Dm; Maximino et al, 2013); and hippocampus (= dorsolateral telencephalon, Dl;Demski, 2013). Subpallial structures in the mesolimbic reward system probably represent partial homologies, with the ventral telencephalon (Vd, Vv, Vc) presenting a pallidal portion and a striatal portion that are equivalent to defining projection does not appear to exist in teleosts, a mesolimbic reward system has been identified, with an analogue in the ascendig projections of the posterior tuberculum.…”

The Integration of Sociality, Monoamines, and Stress Neuroendocrinology in Fish Models: Applications in the Neurosciences

“…Based on topology, hodology, and expression of receptors for sexual hormones, O'Connell & Hofmann (2011b) proposed direct one-to-one homologs of the periaqueductal gray area and POA in fish, and the anterior and ventral tuberal regions as homologues for anterior and ventromedial hypothalamus, respectively; these structures would comprise the social behaviour network in fish. In the mesolimbic reward system, homologues have been proposed for the basolateral (pallial) amygdala (= dorsomedial telencephalon, Dm; Maximino et al, 2013); and hippocampus (= dorsolateral telencephalon, Dl; Demski, 2013). Subpallial structures in the mesolimbic reward system probably represent partial homologies, with the ventral telencephalon (Vd, Vv, Vc) presenting a pallidal portion and a striatal portion that are equivalent to functional (analogical) equivalent is the ascending dopaminergic projection that originates in the posterior tuberculum (Rink & Wullimann, 2001, 2004Tay et al, 2011).…”