The Role of Acetylcholine in Attention in Turtles (Chrysemys picta).

Research on mammals and turtles has suggested that acetylcholine is involved in attention in these groups. Two experiments investigated the ability of painted turtles (Chrysemys picta) to ignore irrelevant stimuli when the basal forebrain acetylcholine system was compromised. In experiment 1, turtles given lesions of the basal magnocellular cholinergic nucleus (NBM) or sham lesions were tested on a go/no go discrimination between horizontal and vertical stripes with or without irrelevant inserts in the box. The irrelevant inserts were blue and white checked walls and green carpet on the floor. The group with lesions of the NBM and no irrelevant inserts had no difficulty learning the task, but the lesioned group with irrelevant inserts was impaired on the discrimination. The sham-lesioned group was not impaired by the presence of irrelevant inserts. In experiment 2, turtles were given either the acetylcholine muscarinic receptor blocker scopolamine or saline and tested on the same task. The turtles given scopolamine had no difficulty learning the task in the absence of irrelevant inserts, but they were severely impaired when irrelevant inserts were present. The irrelevant inserts did not affect the learning of control turtles given saline. These findings provide evidence that acetylcholine enhances turtles' ability to orient to relevant stimuli and suggest that its role in learning and memory may be to allow animals to orient to the stimuli relevant to a task and to ignore irrelevant stimuli.

Plasticity and Adult Neurogenesis in Amphibians and Reptiles: More Questions than Answers.

Studies of the relationship between behavioral plasticity and new cells in the adult brain in amphibians and reptiles are sparse but demonstrate that environmental and hormonal variables do have an effect on the amount of cell proliferation and/or migration. The variables that are reviewed here are: enriched environment, social stimulation, spatial area use, season, photoperiod and temperature, and testosterone. Fewer data are available for amphibians than for reptiles, but for both groups many issues are still to be resolved. It is to be hoped that the questions raised here will generate more answers in future studies.

Housing experience affects adult neurogenesis in turtles (Chrysemys picta).

Adult neurogenesis increases in mammals when they are exposed to an enriched environment or given the opportunity to exercise. In this experiment, we investigated whether turtles would show differences in the number of new neurons in the telencephalon when they were exposed to deep water, conspecifics, and plants and logs (EE group), compared to a group of animals housed in individual cages with shallow water (IN group). A control group (EX) was given deep water and conspecifics but no plants and logs. We gave nine injections of BrdU over a 3-week period, starting when the turtles were introduced to the housing. The results showed that both the EE and the EX groups had more new cells in the dorsal ventricular ridge (DVR), a sensory area of the telencephalon. The two groups did not differ from one another. The group-housed animals also had a higher percentage of new neurons in the DVR that were double labeled for NeuN, a marker of neurons, compared to the IN group. There were no significant differences between groups in the number of new cells in the medial cortex, the homolog of the hippocampus. These findings demonstrate that the housing experience influences the number of new cells that survive in the brains of turtles. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Affective ratings and startle modulation in people with nonclinical depression.

This study tested predictions based on the emotion context insensitivity (ECI) hypothesis of Rottenberg, Gross, and Gotlib (2005) that a nonclinical sample of people with depressive symptoms would show reduced responses to both positive and negative stimuli relative to people without depression and would show an enhanced response to novelty. Seventy individuals completed diagnostic questionnaires, made ratings of 21 affectively valenced pictures, and then viewed the same 21 pictures and 21 novel pictures while startle blink responses were recorded from electromyographic activity of the orbicularis oculi. People with scores on the Beck Depression Inventory (BDI; Beck, Ward, Mendelson, Mock, & Erbaugh, 1961) indicative of depression demonstrated a lack of affective startle modulation compared to the nondepression group. For all participants, the startle response was larger for novel pictures than for previously viewed pictures, but scores on the BDI were not related to response to novelty. Taken together, the results suggest that nonclinical depression is associated with a lack of affective modulation of startle, as has been shown for clinical depression.

Effects of blocking nitric oxide on learning in turtles (Chrysemys picta).

Turtles (Chrysemys picta) were given the nitric oxide synthase inhibitor NW-nitro-L-arginine methyl ester (L-NAME) or its inactive isomer NW-nitro-D-arginine methyl ester (D-NAME) and were trained on a negative patterning task or a simple go/no-go discrimination task. L-NAME impaired the learning of negative patterning but did not affect retention of the task if it had already been learned. D-NAME had no effect. Go/no-go discrimination learning was not affected by L-NAME. These findings support the notion that nitric oxide plays a role in complex configural learning in a reptile closely related to the ancestors of mammals.

Sensation seeking and startle modulation by physically threatening images.

The potential moderating effect of sensation seeking on anxious reactivity to threatening experiences was assessed using the affective modulation of startle-blink paradigm. Startle blinks, as measured by electromyographic (EMG) activity in response to loud (100 dB) white-noise stimuli, were elicited during the presentation of positive, neutral, and threatening visual images. Unlike participants low in sensation seeking who showed blink potentiation during threatening versus neutral images, participants high in sensation seeking showed equal magnitudes of startle to neutral and threatening images. The results suggest that individuals high compared with low on sensation seeking are less anxiously reactive to physically threatening visual stimuli. No attenuation in startle magnitude was elicited by positive images among low or high sensation seekers suggesting that the positive images employed in the current study were not arousing enough to activate the appetitive arousal system.

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

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.