Behavioral Studies of Telencephalic Function in Reptiles

Afferent projections to the lateral hypothalamic area and dorsomedial hypothalamic nucleus of the lizard Gekko gecko were studied after applications of wheat germ agglutinin conjugated to horseradish peroxidase. Large applications into the hypothalamus labeled several telencephalic populations not observed after smaller injections. These included the rostrolateral area of the dorsal cortex, a sheet of cells deep to the caudal pole of the lateral cortex, the external amygdala, and part of the dorsal ventricular ridge. Other populations were labeled in the diencephalon, including the supraoptic nucleus and nucleus ovalis; in the medulla the medial reticular area was labeled. Injections into the lateral hypothalamic area labeled neurons in the rostrolateral dorsal cortex, anterior, lateral, and dorsal septal nuclei, the striatoamygdalar area, nucleus accumbens, vertical limb of the diagonal band, nucleus of the accessory olfactory tract, the interstitial, ventral anterior, and ventral posterior amygdalar nuclei, several hypothalamic nuclei, and the posteroventral thalamic nucleus. Labeled brainstem populations included the ventral tegmental area, torus semicircularis, parvocellular and ventral isthmal nuclei, superior raphe, and the solitary nucleus. Injections in the dorsomedial hypothalamic nucleus labeled neurons in the rostral and caudolateral poles of the dorsal cortex, anterior septal nucleus, horizontal limb of the diagonal band, nucleus of the anterior commissure, several hypothalamic areas, the lateral habenula, the posteroventral thalamic nucleus, and cells scattered around the dorsolateral anterior thalamic nuclei. Labeled brainstem populations included the torus semicircularis, ventral tegmental area, superior raphe, parvocellular and ventral isthmal nuclei, and the lateral dorsal tegmental nucleus. The results of these studies are compared with findings in amphibians and mammals.

Section: Comparisons With Amphibians and Mammalssupporting

confidence: 71%

Afferent Projections to the Lateral and Dorsomedial Hypothalamus in a Lizard, <i>Gekko gecko</i>

Bruce

Neary

1995

“…Both the lizard MC and DC appear to play a role in non-spatial memory tasks that are hippocampally dependent in mammals [Gray and McNaughton, 1983] such as long term memory, reversal learning, and extinction [Peterson, 1980;Ivazov, 1983]. We have recently completed a study examining the effects of MC and DC lesions in lizards (the active forager Cnemidophorus inornatus) on performance of a spatial task [Day et al, 1998].…”

Section: Discussionmentioning

confidence: 99%

“…Rather, two regions, the medial cortex (MC) and dorsal cortex (DC) of lizards, appear to be homologous as a field to the hippocampus proper and associated limbic areas such as the entorhinal, subicular, and cingulate cortices [Butler, 1976;Northcutt, 1978;Bruce and Butler, 1984;Berbel, 1987;Hoogland and Vermeulen-Van der Zee, 1987;Martinez-Garcia and Olucha, 1987;Davila et al, 1993;Luis de la Iglesia et al, 1994]. Relatively little attention has been paid to the functions of the MC and DC lizards, but it does appear that they are involved in learning [Morlock, 1972;Peterson, 1980;Ivazov, 1983;Font and Gomez-Gomez, 1991;Day et al, 1998]. …”

Section: Introductionmentioning

confidence: 99%

Relative Medial and Dorsal Cortex Volume in Relation to Foraging Ecology in Congeneric Lizards

Day¹,

Crews²,

Wilczynski³

1999

The need to locate distributed resources such as mates, food, and nests is correlated with an enlarged hippocampus in many mammalian and avian species. This correlation is believed to be a consequence of selection for spatial ability. Little is known about how such ecological needs affect non-mammalian, non-avian species. In lizards, the putative hippocampal homologues are the dorsal cortex (DC) and medial cortex (MC). We examined the relationship between foraging ecology and the size of the DC and MC in congeneric male lizards. We predicted based on the mammalian and avian literature that Acanthodactylus boskianus, an active forager that captures clumped, immobile prey would have a larger MC and DC than A. scutellatus, a sit-and-wait predator, that captures mobile prey. Our previous behavioral studies showed that A. boskianus did not differ from A. scutellatus on a spatial task but that A. boskianus was significantly better at the reversal of a visual discrimination, another task that is hippocampally dependent in mammals. In the current study, we found that, relative to telencephalon volume, the MC and DC were larger in the active forager whereas a control region, the lateral, olfactory, cortex, was similar in size between species. The current anatomical results suggest that MC and DC size is related to active foraging in lizards and, along with our previous behavioral studies, show that it is possible for this relationship to occur in the absence of evidence for species differences in spatial memory.

“…Rats (Rattus norvegicus) with HP lesions are impaired in both position and place reversals [Gray and McNaughton, 1983;Whishaw and Tomie, 1997]. Cats [Felis domesticus;Gray and McNaughton, 1983], pigeons [Columba livia ;Good, 1987], turtles [DC lesions in Chrysemys picta and MC lesions in Pseudemys scripta; Grisham and Powers, 1990;Rodriguez et al, 2002], lizards [DC lesions in Dipsosaurus dorsalis; Peterson, 1980] and goldfish [Carassius auratus;Flood et al, 1976;Lopez et al, 2000a] with HP lesions are all impaired on place or position reversals. For D. dorsalis lizards, only serial reversals, not initial reversals, are affected [Peterson, 1980].…”

Section: Impaired Reversal Learningmentioning

confidence: 99%

“…Cats [Felis domesticus;Gray and McNaughton, 1983], pigeons [Columba livia ;Good, 1987], turtles [DC lesions in Chrysemys picta and MC lesions in Pseudemys scripta; Grisham and Powers, 1990;Rodriguez et al, 2002], lizards [DC lesions in Dipsosaurus dorsalis; Peterson, 1980] and goldfish [Carassius auratus;Flood et al, 1976;Lopez et al, 2000a] with HP lesions are all impaired on place or position reversals. For D. dorsalis lizards, only serial reversals, not initial reversals, are affected [Peterson, 1980]. The result reported for C. auratus goldfish occurs when the entire telencephalon is ablated, but deficits may be due predominantly to the inclusion of the LP in these lesions [Overmier and Papini, 1985;Salas et al, 1996a, b;Rodriguez et al, 2002].…”

Section: Impaired Reversal Learningmentioning

confidence: 99%

The Importance of Hippocampus-Dependent Non-Spatial Tasks in Analyses of Homology and Homoplasy

Day

2003

The hippocampus or a homologous region plays a role in spatial tasks in a large number of vertebrate species. This result, in combination with recent findings of adaptive specializations of the hippocampus for spatial demands, has led to the conclusion that the prominent selective force behind hippocampal evolution was a need for spatial abilities. However, a review of non-spatial hippocampus-dependent tasks shows that many vertebrate species also share non-spatial functions of the hippocampus. Placed in the appropriate phylogenetic context, it becomes clear that non-spatial facets of hippocampal function were just as likely to be present in our vertebrate ancestors as spatial ones. In addition, the absence of spatial strategy use in three lineages suggests divergence of this feature. Divergence in this character and other characteristics of hippocampal function are meaningful indicators of lineage specific functions. Studies of the evolution of the hippocampus must include examination of spatial and non-spatial functions of the hippocampus and consider both conserved, as well as derived, features.