Time course of memory formation for an appetitive, one-trial, water-reward task in day-old chicks.

Researchers studying learning and memory in the day-old chick have developed a one-trial taste avoidance learning task, in which a chick pecks a bead coated with an aversive-tasting liquid such as methylanthranilate. The current study examined, in two experiments, whether chicks could demonstrate learning of an appetitive version of the one-trial task, and how long this memory might last. The results demonstrate that chicks show significantly decreased latencies to peck a test bead similar to that pecked at training coated with water, and that this memory lasted for at least 6 h after training. These results demonstrate that this appetitive task produces significant learning.

Amelioration of scopolamine-induced amnesia by phosphatidylserine and curcumin in the day-old chick.

In the one-trial taste-avoidance task in day-old chicks, acetylcholine receptor activation has been shown to be important for memory formation. Injection of scopolamine produces amnesia, which appears to be very similar in type to that of Alzheimer's disease, which is correlated with low levels of acetylcholine in the brain. Traditional pharmacological treatments of Alzheimer's disease, such as cholinesterase inhibitors and glutamate receptor blockers, improve memory and delay the onset of impairments in memory compared with placebo controls. These agents also ameliorate scopolamine-induced amnesia in the day-old chick trained on the one-trial taste-avoidance task. The present experiments examined the ability of two less traditional treatments for Alzheimer's disease, phosphatidylserine and curcumin, to ameliorate scopolamine-induced amnesia in day-old chicks. The results showed that 37.9 mmol/l phosphatidylserine and 2.7 mmol/l curcumin significantly improved retention in chicks administered scopolamine, whereas lower doses were not effective. Scopolamine did not produce state-dependent learning, indicating that this paradigm in day-old chicks might be a useful one to study the effects of possible Alzheimer's treatments. In addition, chicks administered curcumin or phosphatidylserine showed little avoidance of a bead associated with water reward, indicating that these drugs did not produce response inhibition. The current results extend the findings that some nontraditional memory enhancers can ameliorate memory impairment and support the hypothesis that these treatments might be of benefit in the treatment of Alzheimer's disease.

Discrimination of shape and size sues by day-old chicks in two one-trial learning tasks.

The ability of day-old chicks (Gallus gallus domesticus) to discriminate between the shape and size of beads was investigated in two one-trial tasks, taste avoidance and sickness-conditioned learning. Previous studies determined that color is a critical classification cue for conditioned stimuli in these tasks. In taste avoidance learning, a chick pecks a bead coated with a bitter substance. In sickness-conditioned learning, chicks peck a dry bead and are injected 30min later with lithium chloride. Chicks could discriminate beads of different sizes, but not different shapes, when trained in the taste avoidance task, whereas in the sickness-conditioned learning task, chicks could discriminate shape, but not size. These results suggest that chicks use a number of classificatory cues to remember an avoidance response, and, in the absence of color cues, chicks rely on different cues for different learning tasks.

Memantine improves observational learning in day-old chicks.

Evidence of observational learning (social learning) is present in many species. One such task is the one-trial taste-avoidance task, in which Actor chicks peck a bead coated with an aversant substance. Observer chicks learn to avoid beads that are similar in appearance to the one presented to the Actors. It has been firmly established that active learning of the one-trial taste-avoidance task is dependent on a constrained level of glutamate receptor activation. The current study examined the effects of memantine, a noncompetitive N-methyl-D-aspartate receptor antagonist, on the learning by Observers. Memantine produced an inverted U-shaped dose-dependent response curve; 1.0 mmol/l memantine produced significant improvement. These results demonstrate that memantine influences memory formation for observational learning in the day-old chick and support the hypothesis that memantine can improve memories by altering levels of glutamate during memory formation.

Memantine ameliorates scopolamine-induced amnesia in chicks trained on taste-avoidance learning.

In day-old chicks trained on the one-trial taste-avoidance task, activation of NMDA receptors by glutamate is particularly important in the initial stages of memory consolidation. In addition, acetylcholine receptor activation has been shown to be a necessary component of memory formation for this task because injection of scopolamine produces amnesia. Memantine, a non-competitive NMDA receptor antagonist, improves memory formation under certain impairing circumstances, despite inhibiting the activation of NMDA receptors. The present experiments tested the hypothesis that memantine can ameliorate scopolamine-induced amnesia in day-old chicks (Gallus gallus domesticus) trained on the one-trial taste-avoidance task. Three experiments assessed the effects of scopolamine, memantine, and glutamate in this task. The results of Experiment 1 demonstrated that 50.0mM scopolamine produces significant amnesia. In Experiment 2, 1.0mM memantine reversed the scopolamine-induced amnesia, while other doses were ineffective. In Experiment 3, injection of 50.0mM glutamate in combination with scopolamine reversed the memantine amelioration. These results indicate a relationship between glutamate and acetylcholine in memory formation in the day-old chick.

Memantine improves memory for taste-avoidance learning in day-old chicks exposed to isolation stress.

Activation of NMDA receptors by glutamate is particularly important in the initial stages of memory consolidation. Memantine, a noncompetitive NMDA receptor antagonist, ameliorates memory impairment under certain circumstances, despite blocking the activation of NMDA receptors. The present experiments tested the hypothesis that memantine can improve memory deficits induced by isolation stress in day-old chicks (Gallus gallus domesticus) trained in a one-trial taste-avoidance task. Three experiments assessed the effects of memantine at different concentrations and in combination with isolation stress. The results of Experiment 1 indicate that, under normal, non-stressed conditions, memory in control animals is strong and 15.0 mM memantine impairs memory, similar to that seen in many studies of the effects of NMDA receptor antagonists on learning. However, the results of Experiments 2 and 3 showed that, when chicks were exposed to isolation stress during the pre-training period, memory formation for saline-injected control animals was impaired and 5.0 mM memantine significantly improved memory in an inverted U-shaped dose response function. The current results extend the findings that memantine can ameliorate memory impairment and supports the hypothesis that memantine, despite its action to reduce NMDA receptor activity, can facilitate normalized memory acquisition.