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PubMed2004

Song function and the evolution of female preferences: why birds sing, why brains matter.

Analyzing the function of song and its evolution as a communication signal provides an essential backdrop for understanding the physiological and neural mechanisms responsible for song learning, perception, and production. The reverse also is true-understanding the mechanisms underlying song learning provides insight into how song has evolved as a communication signal. Song has two primary functions: to repel other males from a defended space and to attract females and stimulate their courtship. The developmental stress hypothesis we present here builds on studies of the development of the song system to suggest how learned features of song, including complexity and local dialect structure, can serve as indicators of male quality useful to females in mate choice. The link between song and male quality depends on the fact that brain structures underlying song learning largely develop during the first few months post-hatching and that during this same period, songbirds are likely to be subject to nutritional and other developmental stresses. Individuals faring well in the face of stress are able to invest more resources to brain development and are expected to be correspondingly better at song learning. Learned features of song thus become reliable indicators of male quality, with reliability maintained by the developmental costs of song. Data from both field and laboratory studies are now beginning to provide broad support for the developmental stress hypothesis, illustrating the utility of connecting mechanistic and evolutionary analyses of song learning.

Animal Communication↗
PubMed1999

Inhibitory control of competing motor memories.

The ability to inhibit previously learned visuomotor associations is essential for efficient learning of novel behaviors. While the neural basis of the system that might control interactions between competing motor memories is not known, it has been demonstrated that animals with ventral and orbital prefrontal cortex (PFC) deficits have particular difficulties in learning to withhold responses to previously conditioned sensory stimuli. Here we measured regional cerebral blood flow (rCBF), using positron emission tomography, during learning of a novel motor task that required inhibition of a previously learned motor memory. Subjects (n=24) learned reaching movements in a force field (field A). After a variable time interval, some subjects (n=15) learned to reach in a field with a reversed pattern of forces (field B). When the time interval was short (10 min), learning in field B was coincident with a reactivation of regions that had become initially activated during learning in field A: the left putamen and bilaterally in the dorsolateral PFC. Behaviorally, this was accompanied with perseveration that lasted for hundreds of movements, suggesting an instantiation of the internal model for field A during learning in field B. Neither the reactivation nor the perseveration were observed in a different group of subjects that learned field B at 5.5 h. We found that the regions which significantly differentiated the two groups during learning of B were in the ventrolateral PFC (bilaterally): there were sharp decreases in rCBF here in the 5.5 group but not in the 10-min group. At 5.5 h motor learning again involved the striatum, but this time in the left caudate. Neither the caudate nor the ventral PFC had exhibited learning-related activity in field A. Instead, they showed changes in rCBF during the reversal of the learning problem when the previously acquired motor memory was successfully gated. The results demonstrate that: (1) perseveration of a competing motor memory may be linked to reactivation of the neural circuit that participated in acquiring that memory, and (2) the ventral PFC may play an important role in the inhibitory control of the competing motor memory.

Adult↗
PubMed1996

A high linoleate and a high alpha-linolenate diet induced changes in learning behavior of rats. Effects of a shift in diets and reversal of training stimuli.

Rats fed from weaning on semi-purified diets supplemented either with linoleate-rich safflower oil (S) or alpha-linolenate-rich perilla oil (P) were mated. Half of the progeny were weaned to the original diet of the dams (SS and PP), the other two groups were shifted to diets enriched in the other fatty acid (SP and PS). Brightness-discrimination learning ability was tested daily for 30 d beginning at 11 weeks of age, with a bright light as the positive stimulus. The learning performance was inferior in the group fed the safflower diet through two generations (SS) as compared with groups fed the perilla diet through two generations (PP) or for which the diets were shifted at weaning (PS and SP). The docosahexaenoate content of brain phospholipids was significantly less in the SS group compared with the three other groups. After 30 d of the learning test, the effect of shifting the stimulus was tested for another 30 d, this time using a dim light as the positive stimulus. The learning performance was superior in the PP group to the SS group throughout the latter 30 sessions, the difference being even more obvious than during the first 30 d. These results indicate that the decrease in the discrimination-learning ability induced by alpha-linolenate deficiency is a relatively reversible process; both the docosahexaenoate content in brain and the learning performance were restored by supplementing alpha-linolenate after the weaning.

Animals↗
PubMed2006

Treadmill running reverses retention deficit induced by morphine.

Human and animal studies have suggested that exercise has benefits overall health and cognitive function. The aim of this study was to investigate the effect of treadmill running on passive avoidance learning and memory deficit in morphine-treated rats. The passive avoidance learning was measured in different time intervals (1, 2 and 24 h as well as 1 week and 1 month). Four groups of rats were included as follows: control, morphine-treated, exercised-saline and exercised-morphine-treated group. The electrical foot shock and treadmill training (2 h at a speed of 5 m/min for 10 days) were applied for all the groups. The data obtained was analyzed using unpaired Students t-test and ANOVA test with group as the independent variable, and performance in each session (avoidances and crossings) as the dependent variables. The results show that the total time staying in dark box was decreased in exercised-saline and exercised-morphine-treated rats by treadmill running (P<0.05). The avoidance learning was significantly reduced in morphine-treated group as indicated by the increased total time of staying in the dark box compared with the control group (P<0.05). We could conclude that exercise increased the delay time of entry to the dark electrical foot shock box, suggesting that morphine impaired the short-term memory and learning and this was reversed by the treadmill running.

Analgesics, Opioid↗
PubMed1970

Fixation produced by conflict.

All rats given a choice between a rewarded alternative and a conflict alternative (rewarded and punished) developed position fixations when the position of the alternatives was reversed. In contrast, all animals given one rewarded alternative and another nonrewarded (or punished and nonrewarded) alternative learned to choose the rewarded side during 25 successive reversals.

Animals↗
PubMed1976

Position reversal deficit in young ferrets.

Young ferrets (6 and 10 weeks old at the start of the experiments) were compared to adult ferrets on learning (1) a Lashley III maze, (2) a left-right discrimination in T-maze with identical choice arms, and (3) a reversal of the left-right discrimination. The young were not inferior to the adults in learning either the Lashley III maze or the initial discrimination in the T-maze. However, the young were markedly (and significantly) inferior to the adults in learning to reverse.

Age Factors↗
PubMed2006

Olfactory repeated discrimination reversal in rats: effects of chlordiazepoxide, dizocilpine, and morphine.

Effects of a benzodiazepine (chlordiazepoxide), an N-methyl-D-aspartate receptor antagonist (dizocilpine), and an opiate agonist (morphine) were studied with a procedure designed to assess effects of drugs and other manipulations on nonspatial learning in rats. In each session, rats were exposed to 2 different 2-choice odor-discrimination problems with food reinforcement for correct responses. One problem (performance discrimination) remained the same throughout the study. That is, 1 odor was always correct (S+) and the other was never correct (S-). For the other problem (reversal discrimination), stimuli changed every session. Six different odors were used to program the reversal discrimination; on any given session, S+ was a stimulus that had served as S- the last time it had appeared, S- was a stimulus that had been S+ on its last appearance. Thus, in each session, learning a discrimination reversal could be studied along with the performance of a comparable, but previously learned, discrimination. Chlordiazepoxide interfered with reversal learning at doses that had no effect on the performance discrimination. Morphine and dizocilpine also impaired reversal learning but only at doses that also affected performance of the well-learned performance discrimination.

Analgesics, Opioid↗
PubMed1977

Unit activity in cingulate cortex and anteroventral thalamus of the rabbit during differential conditioning and reversal.

Multiple-unit activity was recorded from the rabbit anterior cingulate cortical area (AC) and from the anteroventral nucleus of the thalamus (AV) during differential avoidance conditioning and reversal. The positive and negative conditioned stimuli were tones of different frequency, and the unconditioned stimulus (UCS) was shock delivered through the grid floor of a rotating-wheel conditioning apparatus. Conditioning was preceded by pretraining with tones and noncontingent presentations of the shock UCS. The results showed associative (differential) neuronal activity in both AC and AV during differential conditioning. The effect in AC occurred in the intermediate and final sessions of conditioning. A very large differential effect appropriate to original conditioning occurred in AC in the first two sessions of reversal training. The differential effect in AV occurred in the final session of conditioning when the behavioral response was well learned. There was no clear neuronal reversal in AC or AV.

Acoustic Stimulation↗
PubMed2001

Could the 5-HT1B receptor inverse agonism affect learning consolidation?

Diverse evidence indicates that, the 5-HT system might play a role in learning and memory, since it occurs in brain areas mediating such processes and 5-HT drugs modulate them. Hence in this work, in order to explore further 5-HT involvement on learning and memory 5-HT1B receptors' role is investigated. Evidence indicates that SB-224289 (a 5-HT1B receptor inverse agonist) post-training injection facilitated learning consolidation in an associative autoshaping learning task, this effect was partially reversed by GR 127935 (a 5-HT1B/1D receptor antagonist), but unaffected by MDL 100907 (a 5-HT2A receptor antagonist) or ketanserin (a 5-HT1D/2A/7 receptor antagonist) at low doses. Moreover, SB-224289 antagonized the learning deficit produced by TFMPP (a 5-HT1A/1B/1D/2A/2C receptor agonist), GR 46611 (a 5-HT1A/1B/1D receptor agonist), mCPP (a 5-HT2A/2C/3/7 receptor agonist/antagonist) or GR 127935 (at low dose). SB-224289 did not alter the 8-OH-DPAT (a 5-HT1A/7 receptor agonist) learning facilitatory effect. SB-224289 eliminated the deficit learning produced by the anticholinergic muscarinic scopolamine or the glutamatergic antagonist dizocilpine. Administration of both, GR 127935 (5mg/kg) plus ketanserin (0.01 mg/kg) did not modify learning consolidation; nevertheless, when ketanserin dose was increased (0.1-1.0mg/kg) and SB-224289 dose was maintained constant, a learning facilitation effect was observed. Notably, SB-224289 at 1.0mg/kg potentiated a subeffective dose of the 5-HT1B/1D receptor agonist/antagonist mixed GR 127935, which facilitated learning consolidation and this effect was abolished by ketanserin at a higher dose. Collectively, the data confirm and extend the earlier findings with GR 127935 and the effects of non-selective 5-HT(1B) receptor agonists. Clearly 5-HT1B agonists induced a learning deficit which can be reversed with SB-224289. Perhaps more importantly, SB-224289 enhances learning consolidation when given alone and can reverse the deficits induced by both cholinergic and glutamatergic antagonist. Hence, 5-HT1B receptor inverse agonists or antagonists could represent drugs for the treatment of learning and memory dysfunctions.

Child↗
PubMed1999

Effects of the novel acetylcholinesterase inhibitor N-octyl-1,2,3, 4-tetrahydro-9-aminoacridine on locomotor activity and avoidance learning in mice.

The acetylcholinesterase reversible inhibitor N-octyl-1,2,3, 4-tetrahydro-9-aminoacridine (THA-C8) is a new synthesized derivative of tacrine (THA) characterized by an alkyl chain in the molecular structure which ameliorates the penetrability of the compound into the central nervous system. THA-C8 (0.1-5 mg/kg) significantly reduced spontaneous locomotor activity in CD1 mice at a dose of 3 mg/kg. Moreover, THA-C8 (0.2-2 mg/kg) significantly improved shuttle-box avoidance acquisition at doses (0.25, 0.3, 1 mg/kg) not affecting locomotion and that are much lower than the doses reported to be effective for THA in animal models. From the data reported it seems that the new compound could be interesting for therapeutic purposes.

Alzheimer Disease↗
PubMed2000

Experimental evidence for spatial learning on octopuses (octopus bimaculoides).

Octopuses forage far from temporary home dens to which they return for shelter. Spatial tasks may assess learning. Octopuses (Octopus bimaculoides) were placed in a novel arena, and their movements were tracked for 72 hr. Movements around the arena decreased across time, consistent with exploratory learning. Next, octopuses were given 23 hr to move around an arena; after a 24-hr delay, their memory of a burrow location was tested. Most remembered the location of the open burrow, demonstrating learning in 1 day. Finally, octopuses were trained to locate a single open escape burrow among 6 possible locations. Retention was tested after a week and was immediately followed by reversal training (location rotated 180 degrees ). Octopuses learned the original location of the burrow, remembering it for a week. Path lengths increased significantly after reversal, gradually improving and showing relearning. Octopuses show exploratory behavior, learning, and retention of spatial information.

Animals↗
PubMed2004

The effect of reversible inactivation of the supramammillary nucleus on passive avoidance learning in rats.

Previous studies have shown that the presence of hippocampal theta activity is important for learning and memory, and that the medial supramammillary nucleus (mSuM) is involved in the control of the frequency of theta rhythm. It has also been shown that the depression of mSuM activity by chlordiazepoxide causes modest impairment of spatial learning. On the other hand, the lateral supramammillary nucleus (lSum) increases long-term potentiation (LTP) of hippocampal population spikes. However, to our knowledge, no reports exist concerning the role of the supramammillary area (SuM) in passive avoidance (PA) learning. In the present study, rats were chronically implanted with a cannula aimed at SuM and were trained on a step-through PA task. They received intra-SuM injection of lidocaine or saline at the following intervals: 5 min before training, 5, 90, and 360 min after the acquisition trial, or 5 min before the retrieval test. When lidocaine was injected 5 min before training there was no effect on acquisition of PA but retrieval was significantly poorer than the control group injected with saline. Lidocaine injection 5 min after the acquisition trial impaired PA retention, but reversible inactivation of SuM at 90 and 360 min after training and 5 min before the retrieval test showed no significant effect on PA retention. It can be concluded that SuM contributes to PA consolidation at least 5 min after the acquisition trial and that this effect may be accomplished through SuM projections to the septal and/or hippocampal areas participating in the PA memorization processes.

Analysis of Variance↗