ABSTRACT
Studies usually show better spatial learning in males and stronger emotional memory in females. Spatial memory differences could relate to diverse strategies, while dissimilar stress reactions could cause emotional memory differences. We compared male and female rats in two emotional (classical emotional conditioning and aversive discrimination memory) and two emotionally "neutral" tasks: (1) plus-maze discriminative avoidance, containing two open and two enclosed arms, one of which presenting aversive stimuli (light/noise). No differences were found in learning, retrieving, or basal emotional levels, while only male rats presented extinction of the task; (2) contextual fear conditioning--a cage was paired to mild foot shocks. Upon reexposure, freezing behavior was decreased in females; (3) spontaneous alternation--the animals were expected to alternate among the arms of a four-arm maze. No differences between genders were found and (4) open-field habituation was addressed in an arena which the rats were allowed to explore for 10 min. Habituation was similar between genders. Differences were found only in tasks with strong emotional contexts, where different fear responses and stress effects could be determinant. The lack of extinction of discriminative avoidance by females points out to stronger consolidation and/or impaired extinction of aversive memories.
Subject(s)
Avoidance Learning/physiology , Discrimination, Psychological/physiology , Emotions/physiology , Extinction, Psychological , Memory/physiology , Sex Characteristics , Analysis of Variance , Animals , Conditioning, Psychological/physiology , Electroshock , Exploratory Behavior/physiology , Fear/physiology , Female , Male , Rats , Rats, WistarABSTRACT
The plus-maze discriminative avoidance paradigm has been used to study the relationship between aversive memory and anxiety. The present study aims to verify if the elevated plus-maze can provide information about appetitive memory and anxiety-like behavior, through a task motivated by food reward. Animals were allowed to explore an elevated plus-maze and received reinforcement in one of the enclosed arms. In a test session performed 24h later, in the absence of reward, rats showed preference for the previously rewarded enclosed arm over the neutral enclosed arm. The administration of diazepam and pentylenetetrazole before training induced, respectively, anxiolytic and anxiogenic effects (as evaluated by open-arm exploration). Both drugs induced amnestic effects, i.e., lack of preference for the rewarded arm in the test session. The results suggest that appetitive memory can be influenced by anxiety levels as well. The plus-maze appetitive discrimination task seems to be a useful model to investigate the relationship between memory and anxiety.
Subject(s)
Anxiety/psychology , Appetitive Behavior/physiology , Discrimination Learning/physiology , Maze Learning/physiology , Neuropsychology/methods , Reward , Amnesia/chemically induced , Animals , Anti-Anxiety Agents/pharmacology , Anxiety/physiopathology , Appetitive Behavior/drug effects , Diazepam/pharmacology , Discrimination Learning/drug effects , Female , GABA Antagonists/pharmacology , Housing, Animal , Maze Learning/drug effects , Models, Animal , Neuropharmacology/instrumentation , Neuropharmacology/methods , Neuropsychology/instrumentation , Pentylenetetrazole/pharmacology , Rats , Rats, WistarABSTRACT
We have recently verified that the monoamine-depleting drug reserpine--at doses that do not modify motor function--impairs memory in a rodent model of aversive discrimination. In this study, the effects of reserpine (0.1-0.5 mg/kg) on the performance of rats in object recognition, spatial working memory (spontaneous alternation) and emotional memory (contextual freezing conditioning) tasks were investigated. While object recognition and spontaneous alternation behavior were not affected by reserpine treatment, contextual fear conditioning was impaired. Together with previous studies, these results suggest that low doses of reserpine would preferentially induce deficits in tasks involved with emotional contexts. Possible relationships with cognitive and emotional processing deficits in Parkinson disease are discussed.
