Reactivated memory of an inhibitory avoidance response in mice is sensitive to a nitric oxide synthase inhibitor

It is accepted that once consolidation is completed memory becomes permanent. However, it has also been suggested that reactivation (retrieval) of the original memory, again, makes it sensitive to the same treatments that affect memory consolidation when given after training. Previous results demonstrated that the immediate post-training intraperitoneal administration of N^ω-nitro-l-arginine methyl ester (L-NAME), a non-specific inhibitor of nitric oxide synthase (NOS), impairs retention test performance of a one-trial step-through inhibitory avoidance response in adult mice. The effect of L-NAME on retention was attributed to an action on memory consolidation of the original learning. For the first time, we report that the administration of L-NAME after the first retention test (memory reactivation) of the inhibitory avoidance response impairs retention performance over six consecutive days. This impairment effect is dose-and-time dependent and could not be attributed to a retrieval deficit since a mild footshock did not reinstate the original avoidance response and no spontaneous recovery was observed at least 21 days after training. Further support for a storage deficit interpretation as opposed to a retrieval deficit was obtained from the fact that L-NAME’s effects after retrieval were not due to state-dependency. The impairment effect of L-NAME was dependent on the age of the original memory. That is, there was an inverse correlation between the susceptibility of the memory trace when reactivated and the time elapsed between training and the first retrieval session. We suggest an action of L-NAME on memory reactivation-induced processes that are different from memory extinction of the original learning extending the biological significance of nitric oxide on memory.     

Between-task transfer of learning from spatial compatibility to a color stroop task

Responses to a relevant stimulus dimension are faster and more accurate when the stimulus and response spatially correspond compared to when they do not, even though stimulus position is irrelevant (Simon effect). It has been demonstrated that practicing with an incompatible spatial stimulus-response (S-R) mapping before performing a Simon task can eliminate this effect. In the present study we assessed whether a learned spatially incompatible S-R mapping can be transferred to a nonspatial conflict task, hence supporting the view that transfer effects are due to acquisition of a general "respond to the opposite stimulus value" rule. To this aim, we ran two experiments in which participants performed a spatial compatibility task with either a compatible or an incompatible mapping and then transferred, after a 5 min delay, to a color Stroop task. In Experiment 1, responses were executed by pressing one of two keys on the keyboard in both practice and transfer tasks. In Experiment 2, responses were manual in the practice task and vocal in the transfer task. The spatially incompatible practice significantly reduced the color Stroop effect only when responses were manual in both tasks. These results suggest that during practice participants develop a response-selection strategy of emitting the alternative spatial response.     

Long- and short-term plastic modeling of action prediction abilities in volleyball

Athletes show superior abilities not only in executing complex actions, but also in anticipating others' moves. Here, we explored how visual and motor experiences contribute to forge elite action prediction abilities in volleyball players. Both adult athletes and supporters were more accurate than novices in predicting the fate of volleyball floating services by viewing the initial ball trajectory, while only athletes could base their predictions on body kinematics. Importantly, adolescents assigned to physical practice training improved their ability to predict the fate of the actions by reading body kinematics, while those assigned to the observational practice training improved only in understanding the ball trajectory. The results suggest that physical and observational practice might provide complementary and mutually reinforcing contributions to the superior perceptual abilities of elite athletes. Moreover, direct motor experience is required to establish novel perceptuo-motor representations that are used to predict others' actions ahead of realization.     

Does aging affect the formation of new topographical memories? Evidence from an extensive spatial training

A decline in navigational abilities is a consistent feature of aging. Although many studies focused on recall of navigational information, the impact of time and type of learning on recall has received little attention. We submitted older adults and young participants to an extensive training of an ecological environment, from both route and survey perspectives. Then, we tested participants’ learning using from both route and survey perspectives. Although older adults benefit from the extensive training, they did not reach the same performance of the young participants. Despite this main effect of age, the effect of the type of learning was the same in the two groups. Congruence between type of learning and recall led to better performance in both groups. We discuss these findings in the light of cognitive models of human navigation and aging. Useful suggestions about how these findings may inform a specific cognitive intervention in older adults are also provided.     

Involvement of the basolateral amygdala in muscarinic cholinergic modulation of extinction memory consolidation

Previous studies have reported that drugs affecting neuromodulatory systems within the basolateral amygdala (BLA), including drugs affecting muscarinic cholinergic receptors, modulate the consolidation of many kinds of training, including contextual fear conditioning (CFC). The present experiments investigated the involvement of muscarinic cholinergic influences within the BLA in modulating the consolidation of CFC extinction memory. Male Sprague Dawley rats implanted with unilateral cannula aimed at the BLA were trained on a CFC task, using footshock stimulation, and 24 and 48 h later were given extinction training by replacing them in the apparatus without footshock. Following each extinction session they received intra-BLA infusions of the cholinergic agonist oxotremorine (10 ng). Immediate post-extinction BLA infusions significantly enhanced extinction but infusions administered 180 min after extinction training did not influence extinction. Thus the oxotremorine effects were time-dependent and not attributable to non-specific effects on retention performance. These findings provide evidence that, as previously found with original CFC learning, cholinergic activation within the BLA modulates the consolidation of CFC extinction.     

The role of Broca's area in speech perception: evidence from aphasia revisited

Motor theories of speech perception have been re-vitalized as a consequence of the discovery of mirror neurons. Some authors have even promoted a strong version of the motor theory, arguing that the motor speech system is critical for perception. Part of the evidence that is cited in favor of this claim is the observation from the early 1980s that individuals with Broca’s aphasia, and therefore inferred damage to Broca’s area, can have deficits in speech sound discrimination. Here we re-examine this issue in 24 patients with radiologically confirmed lesions to Broca’s area and various degrees of associated non-fluent speech production. Patients performed two same-different discrimination tasks involving pairs of CV syllables, one in which both CVs were presented auditorily, and the other in which one syllable was auditorily presented and the other visually presented as an orthographic form; word comprehension was also assessed using word-to-picture matching tasks in both auditory and visual forms. Discrimination performance on the all-auditory task was four standard deviations above chance, as measured using d′, and was unrelated to the degree of non-fluency in the patients’ speech production. Performance on the auditory–visual task, however, was worse than, and not correlated with, the all-auditory task. The auditory–visual task was related to the degree of speech non-fluency. Word comprehension was at ceiling for the auditory version (97% accuracy) and near ceiling for the orthographic version (90% accuracy). We conclude that the motor speech system is not necessary for speech perception as measured both by discrimination and comprehension paradigms, but may play a role in orthographic decoding or in auditory–visual matching of phonological forms.     

AF-DX 116, a Presynaptic Muscarinic Receptor Antagonist, Potentiates the Effects of Glucose and Reverses the Effects of Insulin on Memory

Male Swiss mice were tested 24 h after training in a one-trial step-through inhibitory avoidance task. Low subeffective doses of -(+)-glucose (10 mg/kg, ip), but not its stereoisomer -(−)-glucose (30 mg/kg, ip), administered immediately after training, and AF-DX 116 (0.3 mg/kg, ip), a presynaptic muscarinic receptor antagonist, given 10 min after training, interact to improve retention. Insulin (8 IU/kg, ip) impaired retention when injected immediately after training, and the effects were reversed, in a dose-related manner, by AF-DX 116 (0.3, 1.0, or 3.0 mg/kg, ip) administered 10 min following insulin. Since AF-DX 116 possibly blocks autoreceptors mediating the inhibition of acetylcholine release from cholinergic nerve terminals, the present data support the view that changes in the central nervous system glucose availability, subsequent to modification of circulating glucose levels, influence the activity of central cholinergic mechanisms involved in memory storage of an inhibitory avoidance response in mice.     

Opposite effects of a single versus repeated doses of gabapentin on retention performance of an inhibitory avoidance response in mice

CF-1 male mice were trained in an inhibitory avoidance (IA) task. A single gabapentin (GBP) administration (50mg/kg, ip) immediately after training enhanced retention performance when mice were tested 8 days after training. On the contrary, when the same dose of the anticonvulsant drug was given twice a day for 7 days (repeated treatment), a significant impairment on retention performance 12h after the last injection of GBP was observed. When the retention test was delayed 7 days after the end of the repeated treatment, the retention performance was not significant different from the control group, whereas if the retention test was delayed 14 days, retention performance was higher than control group but similar to that observed when GBP was administered once immediately after training. The impairment on retention performance was correlated with a significant decrease in the high affinity choline uptake in the hippocampus at the end of the retention test. The pretest administration of the direct muscarinic cholinergic agonist oxotremorine (50 microg/kg, ip) reversed the impairment on retention performance. This reversion was prevented by the muscarinic cholinergic antagonist scopolamine (0.5 mg/kg, ip). Taken together, these results suggest that the impairment on retention performance of an IA task in mice induced by repeated administration of GBP affected memory retrieval but not memory consolidation and that this impairment may be attributable to a reduction on central cholinergic activity.