Comparing brain activity patterns during spontaneous exploratory and cue-instructed learning using single photon-emission computed tomography (SPECT) imaging of regional cerebral blood flow in freely behaving rats

Imaging of Functional Brain Circuits during Acquisition and Memory Retrieval in an Aversive Feedback Learning Task: Single Photon Emission Computed Tomography of Regional Cerebral Blood Flow in Freely Behaving Rats

Active avoidance learning is a complex form of aversive feedback learning that in humans and other animals is essential for actively coping with unpleasant, aversive, or dangerous situations. Since the functional circuits involved in two-way avoidance (TWA) learning have not yet been entirely identified, the aim of this study was to obtain an overall picture of the brain circuits that are involved in active avoidance learning. In order to obtain a longitudinal assessment of activation patterns in the brain of freely behaving rats during different stages of learning, we applied single-photon emission computed tomography (SPECT). We were able to identify distinct prefrontal cortical, sensory, and limbic circuits that were specifically recruited during the acquisition and retrieval phases of the two-way avoidance learning task.

Revisiting the role of anxiety in the initial acquisition of two-way active avoidance: pharmacological, behavioural and neuroanatomical convergence

Two-way active avoidance (TWAA) acquisition constitutes a particular case of approach -avoidance conflict for laboratory rodents. The present article reviews behavioural, psychopharmacological and neuroanatomical evidence accumulated along more than fifty years that provides strong support to the contention that anxiety is critical in the transition from CS (conditioned stimulus)-induced freezing to escape/avoidance responses during the initial stages of TWAA acquisition. Thus, anxiolytic drugs of different types accelerate avoidance acquisition, anxiogenic drugs impair it, and avoidance during these initial acquisition stages is negatively associated with other typical measures of anxiety. In addition behavioural and developmental treatments that reduce or increase anxiety/stress respectively facilitate or impair TWAA acquisition. Finally, evidence for the regulation of TWAA acquisition by septo-hippocampal and amygdala-related mechanisms is discussed. Collectively, the reviewed evidence gives support to the initial acquisition of TWAA as a paradigm with considerable predictive and (in particular) construct validity as an approach-avoidance conflict-based rodent anxiety model.

The role of anti-inflammatory cytokines in memory processing in a healthy brain

The purpose of the work was to study the role of anti-inflammatory cytokines in memory processing in a healthy brain. Wistar rats were trained to perform a task with positive (food) reinforcement; and then the task performance was tested after intraventricular injection of IL-10 or TGF-β1. A microinjection into the brain of either of the two cytokines did not affect the performance of the task and did not have an anti-amnesic effect when the retrieval was deteriorated with scopolamine. In addition, endogenous levels of IL-10 and TGF-β1 were determine in the prefrontal cortex and in the hippocampus after one and two training sessions, consisting of 10 runs each. The level of IL-10 did not change after training both in the prefrontal cortex and in the hippocampus. Endogenous level of TGF-β1 increased in the neocortex after the first training session, the second session, and recovered to the normal level three days after training. In contrast, in the hippocampus, the level of TGF-β1 was decreased: maximally after the first training session in the right hippocampus and after the second training session in the left one. Given the role of the prefrontal cortex in memory processing, we assume that a specific increase of TGF-β1 in the prefrontal cortex may indicate involvement in memory trace consolidation.