Sex differences in social modulation of learning in rats.

In its simplest form, empathy can be characterized as the capacity to share the emotional experiences among individuals, a phenomenon known as emotional contagion. Recent research shows that emotional contagion and its adaptive role can be studied in rodents. However, it is not known whether sex differences observed in human empathy extend to its more primitive forms.

Social modulation in extinction of aversive memories.

Return of fear after extinction is a considerable challenge for the efficacy of exposure-based therapies. Fear recovery is most often modeled in the laboratory by changing the experimental context and studied in isolated animals. Since social context is an important factor affecting behavior, the question arises how it influences the recovery of extinguished fear.

Functional anatomy of neural circuits regulating fear and extinction.

The memory of fear extinction is context dependent: fear that is suppressed in one context readily renews in another. Understanding of the underlying neuronal circuits is, therefore, of considerable clinical relevance for anxiety disorders. Prefrontal cortical and hippocampal inputs to the amygdala have recently been shown to regulate the retrieval of fear memories, but the cellular organization of these projections remains unclear.

Differential startle magnitude in mice selected for high and low swim analgesia is not related to difference in nociception.

The acoustic startle response (ASR) elicited by 110 dB 10-ms pulses was studied in relation to pain sensitivity in mouse lines selectively bred for high (HA) and for low (LA) swim analgesia. The magnitudes of ASR, similarly as hot-plate latencies, differed between the lines in the rank order HA is greater than unselected controls (C) greater than LA. The animals' nociception did not change after the ASR session consisting of a sequence of 20 acoustic stimuli.

Acoustic startle and disruption of prepulse inhibition by dizocilpine in selectively bred mice.

In this study we examined the relationship between genetically produced differences in the magnitude of prepulse inhibition (PPI) of the acoustic startle response (ASR) and stress induced swim analgesia in genetically different strains of mice. Prepulse inhibition of the ASR and its changes due to dizocilpine (MK-801) injection were studied in 180 mice. The animals used in this study were obtained from our colony of 54 generation, Swiss-Webster mice selectively bred for high and low magnitude of analgesia.

Social modulation of learning in rats.

It is well known that emotions participate in the regulation of social behaviors and that the emotion displayed by a conspecific influences the behavior of other animals. In its simplest form, empathy can be characterized as the capacity to be affected by and/or share the emotional state of another. However, to date, relatively little is known about the mechanisms by which animals that are not in direct danger share emotions.

Functional internal complexity of amygdala: focus on gene activity mapping after behavioral training and drugs of abuse.

The amygdala is a heterogeneous brain structure implicated in processing of emotions and storing the emotional aspects of memories. Gene activity markers such as c-Fos have been shown to reflect both neuronal activation and neuronal plasticity. Herein, we analyze the expression patterns of gene activity markers in the amygdala in response to either behavioral training or treatment with drugs of abuse and then we confront the results with data on other approaches to internal complexity of the amygdala.

Differential involvement of the central amygdala in appetitive versus aversive learning.

Understanding the function of the distinct amygdaloid nuclei in learning comprises a major challenge. In the two studies described herein, we used c-Fos immunolabeling to compare the engagement of various nuclei of the amygdala in appetitive and aversive instrumental training procedures. In the first experiment, rats that had already acquired a bar-pressing response to a partial food reinforcement were further trained to learn that an acoustic stimulus signaled either continuous food reinforcement (appetitive training) or a footshock (aversive training).

Between-subject transfer of emotional information evokes specific pattern of amygdala activation.

Emotional states displayed by an animal or a human can seriously affect behavior of their conspecifics. The amygdala plays a crucial role in the processing of emotions. In this study, we describe an experimental rat model of between-subject transfer of emotional information and its effects on activation of the amygdala.

Effects of stimulus modality on the shuttle activity in rats.

Shuttle activity during repeated presentation of irrelevant auditory (white band noise) and visual (darkness) stimuli was studied in 32 male Möll-Wistar rats. The subjects were randomly divided into two groups. In Group ND the auditory stimulus was used in the first habituation session, and the visual stimulus in the second habituation session.

Complex effects of NMDA receptor antagonist APV in the basolateral amygdala on acquisition of two-way avoidance reaction and long-term fear memory.

Although much has been learned about the role of the amygdala in Pavlovian fear conditioning, relatively little is known about an involvement of this structure in more complex aversive learning, such as acquisition of an active avoidance reaction. In the present study, rats with a pretraining injection of the N-methyl-D-aspartate (NMDA) receptor antagonist, 2-amino-5-phosphonopentanoic acid (APV), into the basolateral amygdala (BLA) were found to be impaired in two-way active avoidance learning. During multitrial training in a shuttle box, the APV-injected rats were not different from the controls in sensitivity to shock or in acquisition of freezing to contextual cues.

Effects of social rearing conditions on conditioned suppression in rats.

Twenty-two rats were reared in standard conditions during the first two months of their life. Then the animals were divided into two groups exposed to different rearing conditions. Twelve animals (Group SO) were housed socially, six animals per cage, and for three weeks they were subjected to sensory stimulation in an enriched environment.

Involvement of the lateral and dorsolateral amygdala in conditioned stimulus modality dependent two-way avoidance performance in rats.

Post-lesion learning and performance of shuttle-box avoidance and subsequent transfer to two warning signals (CSs) of different modality were investigated in 27 rats subjected either to a sham lesion (Group NORM), electrolytic injuries of the lateral amygdaloid nucleus (Group LAT), or combined lesions of the amygdalostriatal transition area and dorsolateral amygdala (Group D-LAT). All groups were divided into two subgroups according to warning signal sequences. In the first subgroup (D-DN-N sequence) the subjects were initially trained with the visual CS (darkness - D), then transferred to the more salient visual and auditory compound CS (darkness and noise - DN), and finally to the auditory CS alone (noise - N).