Two-way Active Avoidance Training Research Articles

Infant avoidance training alters cellular activation patterns in prefronto-limbic circuits during adult avoidance learning: II. Cellular imaging of neurons expressing the activity-regulated cytoskeleton-associated protein (Arc/Arg3.1).

Positive and negative feedback learning is essential to optimize behavioral performance. We used the two-way active avoidance (TWA) task as an experimental paradigm for negative feedback learning with the aim to test the hypothesis that neuronal ensembles activate the activity-regulated cytoskeletal (Arc/Arg3.1) protein during different phases of avoidance learning and during retrieval. A variety of studies in humans and other animals revealed that the ability of aversive feedback learning emerges postnatally. Our previous findings demonstrated that rats, which as infants are not capable to learn an active avoidance strategy, show improved avoidance learning as adults. Based on these findings, we further tested the hypothesis that specific neuronal ensembles are "tagged" during infant TWA training and then reactivated during adult re-exposure to the same learning task. Using cellular imaging by immunocytochemical detection of Arc/Arg3.1, we observed that, compared to the untrained control group, (1) only in the dentate gyrus the density of Arc/Arg3.1-expressing neurons was elevated during the acquisition phase of TWA learning, and (2) this increase in Arc/Arg3.1-expressing neurons was not specific for the TWA learning task. With respect to the effects of infant TWA training we found that compared to the naïve non-pretrained group (a) the infant pretraining group displayed a higher density of Arc/Arg3.1-expressing neurons in the anterior cingulate cortex during acquisition on training day 1, and (b) the infant pretraining group displayed elevated density of Arc/Arg3.1-expressing neurons in the dentate gyrus during retrieval on test day 5. Correlation analysis for the acquisition phase revealed for the ACd that the animals which showed the highest number of avoidances and the fastest escape latencies displayed the highest density of Arc/Arg3.1-expressing neurons. Taken together, we are the first to use the synaptic plasticity protein Arc/Arg3.1 to label neuronal ensembles which are involved in different phases of active avoidance learning and whose activity patterns are changing in response to previous learning experience during infancy. Our results indicate (1) that, despite the inability to learn an active avoidance response in infancy, lasting memory traces are formed encoding the subtasks that are learned in infancy (e.g., the association of the CS and UCS, escape strategy), which are encoded in the infant brain by neuronal ensembles, which alter their synaptic connectivity via activation of specific synaptic plasticity proteins such as Arc/Arg3.1 and Egr1, and (2) that during adult training these memories can be retrieved by reactivating these neuronal ensembles and their synaptic circuits and thereby accelerate learning.

Context-dependent differences in grooming behavior among the NIH heterogeneous stock and the Roman high- and low-avoidance rats

Grooming occurs during/after stress and seems to accompany dearousal. Here, grooming was investigated under testing situations involving different levels of aversiveness, taking advantage of differences among three rat strains in fearfulness/anxiety. Inbred Roman High Avoidance (RHA-I) rats are less anxious/fearful than inbred Roman Low Avoidance (RLA-I). The outbred genetically heterogeneous stock of rats (NIH-HS), which resembles the RLA-I in many behavioral traits, was also studied. Adult male rats (RLA-I: n=9, RHA-I: n=10, NIH-HS: n=12) were observed for 30min in: a novel open-field, a novel hole-board and in the home-cage. They were also observed during two-way active avoidance training. Differences in grooming depended on test situation: (a) No differences were found in the home-cage. (b) While tested in a novel environment, RHA-I showed less grooming activity than the other rats. (c) After avoidance responses appeared, differences among the strains were opposite to the observed in novelty tests. Furthermore, results suggest that (i) grooming is mostly suppressed when assured aversive experience is under way; (ii) rostral grooming prevails when experience with aversive stimuli is unpredictable (novelty) or potential (avoidance training); (iii) body grooming increases for a period in novel environments. In general, our results support that grooming takes place during dearousal.

Infant Cognitive Training Preshapes Learning-Relevant Prefrontal Circuits for Adult Learning: Learning-Induced Tagging of Dendritic Spines

Work in various animal models has demonstrated that cognitive training in infancy has a greater effect on adult cognitive performance than pretraining in adulthood. Since the underlying synaptic mechanisms are unclear, the aim of this study was to test the working hypothesis that associative training "preshapes" synaptic circuits in the developing infant brain and thereby improves learning in adulthood. Using a two-way active avoidance (TWA) paradigm, we found that avoidance training during infancy, even though the infant rats were not capable to learn a successful avoidance strategy, improves avoidance learning in adulthood. On the neuroanatomical level we show here for the first time that infant TWA training in the ventromedial prefrontal cortex suppresses developmental spine formation. In contrast in the lateral orbitofrontal cortex, developmental spine pruning is suppressed, possibly by "tagging" activated synapses, which thereby are protected from being eliminated. Moreover, we demonstrate that infant TWA training alters learning-induced synaptic plasticity in the adult brain. The synaptic and dendritic changes correlate with specific behavioral parameters. Taken together, these results support the working hypothesis that infant cognitive training interferes with developmental reorganization and maturation of dendritic spines and thereby "optimizes" prefrontal neuronal circuits for adult learning.

Sex-specific positive and negative consequences of avoidance training during childhood on adult active avoidance learning in mice

In humans and animals cognitive training during childhood plays an important role in shaping neural circuits and thereby determines learning capacity later in life. Using a negative feedback learning paradigm, the two-way active avoidance (TWA) learning, we aimed to investigate in mice (i) the age-dependency of TWA learning, (ii) the consequences of pretraining in childhood on adult learning capacity and (iii) the impact of sex on the learning paradigm in mice. Taken together, we show here for the first time that the beneficial or detrimental outcome of pretraining in childhood depends on the age during which TWA training is encountered, indicating that different, age-dependent long-term “memory traces” might be formed, which are recruited during adult TWA training and thereby either facilitate or impair adult TWA learning. While pretraining during infancy results in learning impairment in adulthood, pretraining in late adolescence improved avoidance learning. The experiments revealed a clear sex difference in the group of late-adolescent mice: female mice showed better avoidance learning during late adolescence compared to males, and the beneficial impact of late-adolescent pretraining on adult learning was more pronounced in females compared to males.

Impaired active avoidance learning in infant rats appears to be related to insufficient metabolic recruitment of the lateral septum

The temporal dissociation between early information acquisition and output of complex behaviors is a common principle during development. Thus, although infant rats are not able to generate sufficient avoidance behavior during two-way active avoidance (TWA) training they obviously deposit a certain “memory trace” ( Schäble, Poeggel, Braun, & Gruss, 2007). The ontogeny of learning is probably mirrored by the maturing functionality of different basal forebrain regions. Two of the basal forebrain regions involved in TWA learning are the medial septum/diagonal band of Broca (MS/DB), which is essential for the encoding and retrieval of memory and the lateral septum (LS) that plays a role in the generation of behavior. Mapping 2-fluoro-deoxy-glucose utilization in freely behaving animals, the aim of this study was to assess the functional recruitment of the MS/DB and LS in infant (P17–P21) and adolescent (P38–P42) rats during the first (acquisition) and fifth (retrieval) TWA training. Metabolic activity in the MS/DB was similar in both age groups during acquisition and retrieval indicating that this region is already mature in the infant rat. In contrast, metabolic activity in the LS was generally lower in the infant rats suggesting that this region is not yet fully functional during P17 and P21. This insufficient recruitment may be one reason for the poor TWA performance of infant rats. Finally, the LS displayed significantly higher activity during acquisition than during retrieval indicating that the highest amount of energy is consumed during the initial learning phase.

Improvement of two-way active avoidance memory requires protein kinase a activation and brain-derived neurotrophic factor expression in the dorsal hippocampus.

Previous studies have shown that two-way active avoidance (TWAA) memory processing involves a functional interaction between the pontine wave (P wave) generator and the CA3 region of the dorsal hippocampus (DH-CA3). The present experiments examined whether the interaction between P wave generator activity and the DH-CA3 involves the intracellular protein kinase A (PKA) signaling system. In the first series of experiments, rats were subjected to a session of TWAA training followed immediately by bilateral microinjection of either the PKA activation inhibitor (KT-5720) or vehicle control into the DH-CA3 and tested for TWAA memory 24 h later. The results indicated that immediate KT-5720 infusion impaired improvement of TWAA performance. Additional experiments showed that KT-5720 infusion also blocked TWAA training-induced BDNF expression in the DH-CA3. Together, these findings suggest that the PKA activation and BDNF expression in the DH-CA3 is essential for the improvement of TWAA memory.

Activation of phasic pontine‐wave generator in the rat: a mechanism for expression of plasticity‐related genes and proteins in the dorsal hippocampus and amygdala

A number of behavioral studies have emphasized the importance of interactions between the pontine-wave (P-wave) generator and the dorsal hippocampus (DH) in two-way active avoidance (TWAA) memory processing; however, the direct involvement of the P-wave generator in the TWAA training trial-induced molecular events in the DH and amygdala has not been systematically evaluated. Here we demonstrate that the TWAA learning training trials activate P-wave generator, and increase phosphorylation of CREB (pCREB) and expression of activity-regulated cytoskeletal-associated (Arc) protein, as well as messenger ribonucleic acid (mRNAs) of Arc, brain-derived nerve growth factor (BDNF) and early growth response-1 (Egr-1) in the DH and amygdala. Selective elimination of P-wave-generating cells abolished P-wave activity and suppressed TWAA learning training trial-induced expression of pCREB and Arc proteins and Arc, BDNF and Egr-1 mRNAs in the DH and amygdala. Following a session of TWAA training, all rats were equal in terms of time spent in wakefulness, slow-wave sleep and rapid eye movement (REM) sleep irrespective of P-wave lesions. The second set of experiments demonstrated that localized cholinergic stimulation of the P-wave generator increased expression of Arc, BDNF and Egr-1 mRNAs in the DH. Together, these findings provide the first direct evidence that activation of P-wave-generating cells is critically involved in the TWAA training trial-induced expression of plasticity-related genes in the DH and amygdala. These findings are discussed in relation to the role of P-wave generator activation for the REM sleep-dependent development and cognitive functions of the brain.

Two‐way active avoidance training‐specific increases in phosphorylated cAMP response element‐binding protein in the dorsal hippocampus, amygdala, and hypothalamus

Previous studies have demonstrated that the activation of pontine-wave (P-wave) generating cells in the brainstem during post-training rapid eye movement (REM) sleep is critical for the consolidation of memory for two-way active avoidance (TWAA) learning in the rat. Here, using immunocytochemistry, we investigated the spatio-temporal distribution of CREB phosphorylation within different parts of the dorsal hippocampus, amygdala, and hypothalamus following a session of TWAA training in the rat. We show that the TWAA training trials increased phosphorylation of CREB (p-CREB) in the dorsal hippocampus, amygdala, amygdalo-hippocampal junction (AHi), and hypothalamus. However, the time intervals leading to training-induced p-CREB activity were different for different regions of the brain. In the dorsal hippocampus, p-CREB activity was maximal at 90 min and this activity disappeared by 180 min. In the AHi, activity of the p-CREB peaked by 180 min and disappeared by 360 min. In the amygdala, the p-CREB activity peaked at 180 min and still remained higher than the control at the 360 min interval. In the hypothalamus, at 90 min p-CREB activity was present only in the ventromedial hypothalamus; however, by 180 min this p-CREB activity was also present in the dorsal hypothalamus, perifornical area, and lateral hypothalamus. By 360 min, p-CREB activity disappeared from the hypothalamus. This TWAA training trials-induced spatiotemporal characteristic of CREB phosphorylation, for the first time, suggests that REM sleep P-wave generator activation-dependent memory processing involves different parts of the dorsal hippocampus, amygdala, and hypothalamus.

Differential response of two subdivisions of lateral amygdala to aversive conditioning as revealed by c-Fos and P-ERK mapping.

Rats were subjected to two aversive learning protocols: either classical (fear conditioning) or instrumental (two-way active avoidance training). Next, immunocytochemical mapping of phosphorylated extracellular signal-regulated kinase (P-ERK) and c-Fos transcription factor protein was performed, and the expression pattern of both markers within the dorsal nucleus of lateral amygdala (LaD) was analyzed. As immunocytochemical studies revealed, aversive training induced ERK phosphorylation and c-Fos expression specifically in ventral but not dorsal tip of LaD. These data show for the first time molecular distinction between subdivisions of LaD as well as they also strengthen the idea of Repa that the neurons in the ventral tip of LaD are involved in storage of long-lasting changes associated with formation of fear memories.

Post-trial sleep sequences including transition sleep are involved in avoidance learning of adult rats

High resolution computerized EEG analyses, and behavioral observations were used to identify slow wave sleep (SS), paradoxical sleep (PS) and transition sleep (TS) in adult male Wistar rats exposed to a session of two-way active avoidance training. Of the four sleep sequences that could be identified, two included TS (SS→TS→W and SS→TS→PS), while the other two did not (SS→W and SS→PS). Comparison of post-trial sleep variables between fast learning rats (FL, reaching criterion in the training session), slow learning rats (SL, reaching criterion in the retention session the following day), and non learning rats (NL, failing to reach criterion) indicated that the total amounts of SS, TS and PS of the SS→TS→PS sequence was markedly higher in FL rats than in SL rats. In addition, in comparison with the corresponding baseline period, the average duration and total amount of SS and TS episodes of the SS→TS→PS sequence increased in FL rats, while the number of SS→TS→W sequences decreased. On the other hand, the average duration of SS episodes increased in the SS→TS→W and SS→W sequences of SL rats, and in the SS→W and SS→TS→PS sequences of NL rats. Correlative analyses between number of avoidances and post-trial sleep variables demonstrated that avoidances were directly correlated with the duration of SS episodes of the SS→TS→PS sequence and with the duration of TS episodes of the SS→TS→W sequence, but inversely correlated with the number and amount of SS episodes of the SS→W sequence and with the duration and amount of SS episodes of the SS→PS sequence. On the whole, the data supported the view that TS-containing sleep sequences are involved in long-term storage of novel adaptive behavior, while sleep sequences lacking TS are involved in the maintenance of innate behavioral responses.

Developmental lead exposure and two-way active avoidance training alter the distribution of protein kinase C activity in the rat hippocampus.

Long-term exposure to a low level of lead is associated with learning deficits. Several types of learning have been correlated to hippocampal protein kinase C (PKC) activation. This study was designed to determine if there is a correlation between the effects of lead on hippocampal PKC activation and those on learning performance. Rats were exposed to 0.2% (w/v) lead acetate at different developmental stages including a maternally exposed group, a postweaning exposed group, and a continuously exposed group. The continuously lead exposed rats tended to avoid less frequently and not respond more frequently in two-way active avoidance training than did controls. This training process was associated with translocation of hippocampal PKC activity from cytosol to membrane. Two-way analysis of variance of data indicates that there is a significant training and lead treatment interaction in the ratio of membrane to cytosolic PKC activity (F3,32 = 3.013; p = 0.044). The interaction is attributable to the absence of the training-induced PKC translocation in the continuously lead exposed rats. In addition, no significant changes were observed in learning performance and training-induced hippocampal PKC activation after maternal and postweaning lead exposure. Continuous and longer duration of lead exposure appears to affect the learning performance and hippocampal PKC activation. These data suggest that a change in the activation of hippocampal PKC may be involved in the lead-induced deficit in learning.

The Structure of Sleep is Related to the Learning Ability of Rats

Using electroencephalographic methods, rats learning or not learning a two-way active avoidance task were found to differ significantly in the structure of sleep determined the day before training. The main differences concerned (i) synchronized sleep episodes followed by wakefulness, which were longer and fewer in learning rats; (ii) paradoxical sleep episodes, which were longer in learning rats. Significant correlations were present between the number and/or the average duration of synchronized sleep episodes followed by wakefulness or by paradoxical sleep and the number of avoidances or escapes scored in the training session. Power spectral analysis indicated that the relative output in the 6-7-Hz region was higher in learning rats, notably during short episodes of synchronized sleep followed by paradoxical sleep. As two-way active avoidance training induces comparable modifications in postacquisition sleep (Ambrosini et al., Physiol. Behav., 51, 217-226, 1992), the features of preacquisition sleep which prevail in learning rats might directly determine their capacity to learn. Alternatively, they might reflect the existence of a genetic determinant independently conditioning the ability to learn.

The sequential hypothesis of sleep function. III. The structure of postacquisition sleep in learning and nonlearning rats

EEG methods were used to examine the structure of postacquisition sleep in learning (L) and nonlearning (NL) rats previously exposed to a session of two-way active avoidance training, and in control rats (C) left in their home cages. In agreement with literature data, the number and total amount of paradoxical sleep (PS) episodes were higher in L rats than in NL rats. In addition, significant differences between L and NL rats concerned the episodes of synchronized sleep followed by wakefulness or by PS (SS-W and SS-PS, respectively). The average duration and related parameters of SS-W episodes, and the average duration, number, amount and related parameters of SS-PS episodes increased in NL and L rats in comparison with C rats. Longer SS-W episodes occurred early in NL and L rats, but the effect lasted longer in NL rats. On the other hand, the increments concerning SS-PS episodes occurred earlier, were more pronounced and lasted longer in L rats. The results support a role of SS in brain information processing, as envisaged by the sequential hypothesis on the role of sleep. They suggest, furthermore, that memory traces lacking adaptive value may be destabilized and cleared away during SS-W and SS-PS episodes, while the remaining memory traces may be retained and eventually stored again in more integrated form during SS-PS and PS episodes, respectively.

The sequential hypothesis on sleep function. II. A correlative study between sleep variables and newly synthesized brain DNA

The information acquired by brain during wakefulness (W) may be processed in two sequential steps occurring during synchronized sleep (SS) and paradoxical sleep (PS), respectively. On the assumption that brain molecules synthesized during the acquisition step undergo a comparable sleep processing, we have designed an experiment aimed at the verification of the sequential hypothesis. Groups of adult female Wistar rats received [ 3H-methyl] thymidine by intraventricular injection 30 min before being exposed to a 4 hr session of a two-way active avoidance training. Animals failing to achieve the learning criterion were further allowed a period of 3 hr during which they were left free to sleep, or were deprived of PS or of total sleep. Control rats were similarly treated, but were left in their home cages in the same training room during the period of acquisition. The results of correlative study among behavioral, sleep and biochemical variables demonstrate that the specific radioactivity of DNA in the cerebral cortex, cerebellum and brainstem is correlated with several variables of postacquisition sleep, mostly SS parameters. The correlations depend on the previous waking experience of the rats. The data substantiate the two main consequences of the hypothesis, i.e., (1) the involvement of SS in brain information processing; and (2) the dependence of the operations performed by the sleeping brain on the nature of the previous waking experience. The results also provide some insight into the kind of processing which occurs in the sleeping brain.