Dorsal Cortex Lesions Impair Habituation in Turtles <i>(Chrysemys picta)</i>

Abstract

Two experiments investigated habituation in painted turtles (Chrysemys picta). In the first, turtles were given lesions of the dorsal cortex or sham lesions and then trained on a restraint. Although the sham-lesioned turtles learned to tolerate the restraint, the lesioned animals continued to struggle against it. Thus dorsal cortex lesions disrupted habituation to restraint. In order to test habituation to a looming stimulus in a second experiment, all animals were habituated to the restraint before surgery. Postoperatively they continued to be habituated to the restraint. The looming stimulus was a circular shadow that enlarged suddenly on a screen in front of the turtle. It was presented 5 times per day for 15 days. Between-day or long-term habituation was impaired by dorsal cortex lesions.

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

“…The MC of turtles is supposed to be homologous to the dentate gyrus and Ammon's horn in rats. Thus the fact that a variety of tasks that are HP dependent in rats such as go, no-go problems, extinction of a key press, and reversal of simultaneous and successive visual discriminations [Grisham and Powers, 1990;Powers, 1990;Moran et al, 1998], are not affected by MC lesions in turtles contrasts not only with findings for lizards but findings in mammals as well. This suggests a divergence in the function of the MC in turtles.…”

“…Autoshaping in both rats (R. norvegicus) and pigeons (C. livia) is reduced in animals with HP lesions. Habituation is impaired in rats (R. norvegicus) and cats (F. domesticus) with HP lesions [Gray and McNaughton, 1983] and turtles (C. picta) with DC lesions [Moran et al, 1998]. The acquisition of go, no-go problems is impaired in both rats with HP lesions [Amsel, 1993] and turtles (C. picta) with DC lesions [Grisham and Powers, 1989].…”

The Role of Acetylcholine in Attention in Turtles (<b><i>Chrysemys picta</i></b>)

“…Turtles with dorsal cortex lesions showed slower long-term habituation than sham-lesioned turtles in two situations, habituation to restraint and habituation to a looming stimulus [Moran et al, 1998]. These deficits suggest that turtles with these lesions have difficulty in learning to ignore irrelevant stimuli.…”

“…Dorsal cortex lesions in turtles also disrupted long-term habituation [Moran et al, 1998], and this deficit took the form of greater responsiveness to the stimulus in the lesioned group, which continued to respond to a stimulus that had no significance. We hypothesized that the habituation deficit might reflect an inability to suppress response to irrelevant stimuli (an orienting deficit) and that this impairment would translate to an inability to focus on the relevant stimuli in a learning experiment.…”

Proliferation, Migration, and Survival of Cells in the Telencephalon of the Ball Python, Python Regius

“…In reptiles, spatial learning has been demonstrated in Elaphe guttata guttata (corn snakes) (Holtzman et al, 1999) and Tiliqua rugosa (blue tongued skinks) (Zuri and Bull, 2000). Also, lesioning the medial and dorsal cortices of turtles causes a reduction in maze navigation ability (Lopez et al, 2003;Rodriguez et al, 2002) and produces deficits in a variety of non-spatial tasks such as discrimination and restraint habituation (Blau and Powers, 1989;Grisham and Powers, 1989;Moran et al, 1998). In squamate reptiles including snakes, the MC is also associated with navigation ability (Baird Day et al, 1999a;Baird Day et al, 1999b;Crews and Wilczynski, 2000;Holding et al, 2012;LaDage et al, 2009;Roth et al, 2006).…”