Neuronal Density in Navigation-Related Regions of the Adult Leopard Gecko Brain

Hypoxic conditions disrupt brain development in many species, but oxygen deprivation may be particularly detrimental to ectotherms such as reptiles. Our preliminary data suggest the brains of embryonic leopard geckos (Eublepharis macularius) are damaged following brief hypoxic conditions in ovo, and these developmental changes are associated with altered exploratory behavior in adulthood. The objective of this study is to understand the effects of such hypoxic conditions neuronally once the geckos have reached adulthood. However, no previous studies have evaluated the neuronal density of navigation-related brain regions in normal adult geckos, or whether these regions are sensitive to early hypoxia. Here, we present the optical density measurements from the medial cortex, the dorsal and lateral cortex, the dorsal lateral thalamus, and the septal region of adult geckos (n=2) that developed in normoxic conditions, to establish a baseline measure of cell density. Mean (SEM) optical density values are shown in the Table. These optical density values provide an important baseline for our on-going evaluation of neuronal sensitivity to hypoxic conditions in ovo. We anticipate that neuronal density values from hypoxic geckos will be reduced, relative to those of geckos that develop in normoxic conditions

Embryonic Hypoxia Alters Exploratory Movement in Adult Geckos

Environmental changes, such as temporary hypoxia, during the embryonic stage can impair brain development in leopard geckos (Eublepharis macularius). We therefore tested whether this early brain damage produces behavioral deficits that persist into adulthood. The organization and kinematic properties of non-visual exploration between normal (n = 14) and hypoxia (n = 3) geckos were compared. Geckos were individually placed on a circular table (diam=91cm) and allowed to explore darkness for 60min while being recorded. The gecko\u27s coordinates were calculated at 5frames/second. Movement properties within each trial were evaluated across five 10min epochs. Total distance, peak speed, movement scaling (correlation between path length and peak speed), distance ratio, heading error, total stop time, mean stop time, number of stops, number of progressions, and progression distance were compared between groups and across epochs with a mixed Group X Epoch ANOVA. Movement properties did not differ across time epochs. However, hypoxia animals showed significantly lower peak speed [F(1,15) = 6.18, p = .025], and greater movement scaling [F(1,15) = 5.78, p = .03] scores, compared to controls. These results indicate that brain damage caused by early hypoxia causes adult geckos to move slowly, but they retain the ability to move normally and accurately estimate distance. Thus, the reduced speed is not caused by a general movement deficit. These preliminary results suggest that embryonic hypoxia alters exploratory behavior that persists into adulthood. This on-going study will continue to evaluate exploratory movement, and data will be added to the presentation as they become available

Overachieving Pigeons: The Justification of Effort Impact on Reward Value

Research in animal and human models suggests that greater reward value is associated with tasks requiring more effort or time to obtain the reward, called the Justification of Effort (JoE). Through a series of two experiments, this study incorporates touchscreen operant chambers to assess the choice preference in a pigeon model. Experiment 1 focuses on physical tasks differentiated between a difficult task (20 pecks to a target) and an easy task (1 peck to a target). After training with the two choice stimuli (correct and incorrect), we begin the critical test. This test assesses the preference between the correct choice after the hard task and after the easy task. Pigeons will be presented with both correct stimuli and asked to choose. The Justification of Effort theory predicts that subjects should prefer the stimulus that followed the hard task over the easy one. Once completed, Experiment 2 will test this same phenomenon except with a cognitively difficult task (perceptually similar stimuli) or a cognitively easy task (perceptually distinct stimuli), rather than the physical task in Experiment 1. Results will follow