Role of acetylcholine in negative patterning in turtles (Chrysemys picta).

Abstract

Turtles were run on a negative patterning task involving 2 positive elements, a key with white stripes on a black background, and a solid red key, and a compound stimulus combining the 2 elements, white stripes on a red background. Injections of scopolamine, methylscopolamine, or saline were started at the same time that the compound stimulus was introduced, after the animals had been autoshaped to press the key for each of the elements. Scopolamine disrupted the learning of negative patterning, but methylscopolamine had no effect. In contrast, learning of a simple discrimination between the elements was not affected by scopolamine. These results show that muscarinic cholinergic receptors are involved in the learning of negative patterning in turtles.

Pharmacological evidence is consistent with a prominent role of spatial memory in complex navigation

“…Prior experimental work in this species showed no reductions in physiological drive or motivation associated with methylscopolamine, thereby confirming its validity as a PNS control (e.g. [31,32]). As before, we allowed turtles to navigate approximately half of their routes prior to manipulation.…”

“…This species has been studied extensively (e.g. [22,[31][32][33][34][35]), particularly in reference to movements, orientation and navigation (e.g. [23,29,34,[36][37][38][39]), learning (e.g.…”

“…To investigate the role of spatial memory in adult turtle navigation, we performed pharmacological manipulations of spatial memory using scopolamine, a mAChR antagonist known to disrupt spatial memory in this species [31,32]. We allowed turtles to navigate their routes naturally prior to manipulation, thereby allowing each individual to act as its own control.…”

“…Scopolamine is known to disrupt spatial memory in this species [31,32], but scopolamine might affect other cognitive or perceptual processes in the CNS unrelated to spatial memory or cognition (e.g. anxiety, motivation).…”

“…R. Soc. B 283: 20152548 Second, to control for possible effects of scopolamine in the peripheral nervous system (PNS), we treated a separate group of adults with methylscopolamine, which cannot enter the central nervous system (CNS) [31,32]. If adult turtles use some aspect of the CNS to navigate these routes, then methlyscopolamine should have no effect on navigation.…”