Reinstatement of short-latency responses after asymptotic Pavlovian conditioning training by the presentation of an extraneous stimulus

The purpose of this study was to examine whether the progressive disappearance of short-latency conditioned responses, or inhibition of delay, observed in Pavlovian conditioning with long inter-stimulus intervals, could be reverted by the presentation of a novel stimulus. In one experiment, two groups of rabbits received extensive training with a short (250 ms) or a long (1500 ms) tone that overlapped and terminated with a periorbital shock unconditioned stimulus. After training, the presentation of an extraneous stimulus prior to tone onset produced a reinstatement of short latency CRs in the group trained with the long CS, but did not affect CR latency in the group trained with the short CS. This finding is consistent with Pavlov's (1927) view that conditioning with long conditioned stimuli involves the acquisition of response tendencies in the early portion of the stimulus that are subsequently suppressed by the development of an inhibitory process.

Induction of Zenk protein expression within the nucleus taeniae of the amygdala of pigeons following tone and shock stimulation

In this study, we evaluated the expression of the Zenk protein within the nucleus taeniae of the pigeon’s amygdala (TnA) after training in a classical aversive conditioning, in order to improve our understanding of its functional role in birds. Thirty-two 18-month-old adult male pigeons (Columba livia), weighing on average 350 g, were trained under different conditions: with tone-shock associations (experimental group; EG); with shock-alone presentations (shock group; SG); with tone-alone presentations (tone group; TG); with exposure to the training chamber without stimulation (context group; CG), and with daily handling (naive group; NG). The number of immunoreactive nuclei was counted in the whole TnA region and is reported as density of Zenk-positive nuclei. This density of Zenk-positive cells in the TnA was significantly greater for the EG, SG and TG than for the CG and NG (P < 0.05). The data indicate an expression of Zenk in the TnA that was driven by experience, supporting the role of this brain area as a critical element for neural processing of aversive stimuli as well as meaningful novel stimuli.

Chlorpheniramine facilitates inhibitory avoidance in teleosts submitted to telencephalic ablation

The present study investigated the involvement of H(1) histaminegic receptor on the acquisition of inhibitory avoidance in Carassius auratus submitted to telencephalic ablation. The fish were submitted to telencephalic ablation 5 days before the experiment. The inhibitory avoidance procedure included 1 day for habituation, 3 days for training composed of 3 trials each (1st day: T1, T2, T3; 2nd day: 2T1, 2T2, 2T3; 3rd day: 3T1, 3T2, 3T3) and 1 day for test. On training days, the fish were placed in a white compartment, after 30 s the door was opened. When the fish crossed to a black compartment, a weight was dropped (aversive stimuli). Immediately after the third trial, on training days, the fish received, intraperitoneally, one of the pharmacological treatments (saline (N = 20), 8 (N = 12) or 16 (N = 13) µg/g chlorpheniramine, CPA). On the test day, the time to cross to the black compartment was determined. The latency of the saline group increased significantly only on the 3rd trial of the 2nd training day (mean ± SEM, T1 (50.40 ± 11.69), 2T3 (226.05 ± 25.01); ANOVA: P = 0.0249, Dunn test: P < 0.05). The group that received 8 µg/g CPA showed increased latencies from the 2nd training day until the test day (T1 (53.08 ± 17.17), 2T2 (197.75 ± 35.02), test (220.08 ± 30.98); ANOVA: P = 0.0022, Dunn test: P < 0.05)). These results indicate that CPA had a facilitating effect on memory. We suggest that the fish submitted to telencephalic ablation were able to learn due to the local circuits of the mesencephalon and/or diencephalon and that CPA interferes in these circuits, probably due an anxiolytic-like effect.

Uma maneira prática de distinguir abelhas africanizadas (Apis mellifera L. ) de abelhas européias usando o estado excitatório central, a mobilidade dos membros e viabilidade do ferrão / A practical means for distinguishing Africanized honey bees (Apis mellifera L. ) from european honey bees by using central excitatory state, appendage mobility and sting viability

Uma chave para o entendimento da expansão da abelha africanizada (Apis mellifera) é distinguir esta abelha agressiva de sua equivalente européia. Técnicas de identificação atual têm um grau de sucesso, mas cada método tem seu próprio conjunto de problemas, tornando-se proibitivo sua adoção e uso em larga escala. Este estudo examinou aspectos do estado excitatório central, persistência de mobilidade de apêndices e viabilidade da ferroada após decapitação como ferramenta na distinção entre essas duas raças. O estado excitatório central não foi útil na distinção entre a abelha africanizada e a européia; todavia, a mobilidade de apêndices e a viabilidade do ferrão foram significativamente diferentes entre essas duas raças. A mobilidade de apêndices e a viabilidade do ferrão são técnicas úteis na distinção das duas raças e atenua os aspectos relacionados a gastos, aplicação e precisão.

A key to understanding the expansion of Africanized honey bees (Apis mellifera) is distinguishing this aggressive form from its European relative. Current identification techniques have a degree of success, but each has its own set of problems, prohibiting wide-spread adoption and use. This study examined aspects of central excitatory state, persistence of mobile appendages, and a viable sting after decapitation for their use in distinguishing between these two races. Central excitatory state was not useful in distinguishing the Africanized honey bee from the European honey bee; however, appendage mobility and sting viability were significantly different between the two subspecies. Appendage mobility and sting viability are useful techniques for distinguishing the two subspecies, and alleviate the issues of expense, application, and accuracy.

Stimulus specificity in the acquisition and extinction of conditioned taste aversion

An experiment evaluated whether the acquisition and extinction of conditioned taste aversion in the rat is stimulus-specific by testing the degree of response transfer between sweet and salty tastes. Animals in the paired-same and paired-different groups received a presentation of a gustatory CS and a cyclophosphamide injection US. Nonconditioned control groups received unpaired CS /US presentations or the CS followed by a vehicle injection. Taste avoidance was evaluated in three nonreinforced test sessions. In the paired-same, unpaired and vehicle groups, all test sessions were conducted with the same flavor as originally used in training, whereas the paired-different group was tested with a novel flavor on the first and second sessions and with the originally trained flavor in last session. Stimulus specific acquisition was apparent in the first test session, when the animals in the group paired-same exhibited lower fluid intake than the other three groups. Evidence of specificity of extinction was apparent in the last test session, when animals in the group paired-different exhibited lower fluid intake than the other three groups. These results provide further evidence of stimulus specificity in acquisition and extinction of conditioned taste aversion, supporting the associative interpretation of these phenomena.

Role of the hippocampus in contextual memory after classical aversive conditioning in pigeons (C. livia)

We investigated the effects of hippocampal lesions with ibotenic acid (IBO) on the memory of the sound-context-shock association during reexposure to the conditioning context. Twenty-nine adult pigeons were assigned to a non-lesioned control group (CG, N = 7), a sham-lesioned group (SG, N = 7), a hippocampus-lesioned experimental group (EG, N = 7), and to an unpaired nonlesioned group (tone-alone exposure) (NG, N = 8). All pigeons were submitted to a 20-min session in the conditioning chamber with three associations of sound (1000 Hz, 85 dB, 1 s) and shock (10 mA, 1 s). Experimental and sham lesions were performed 24 h later (EG and SG) when EG birds received three bilateral injections (anteroposterior (A), 4.5, 5.25 and 7.0) of IBO (1 µl and 1 µg/µl) and SG received one bilateral injection (A, 5.25) of PBS. The animals were reexposed to the training context 5 days after the lesion. Behavior was videotaped for 20 min and analyzed at 30-s intervals. A significantly higher percent rating of immobility was observed for CG (median, 95.1; range, 79.2 to 100.0) and SG (median, 90.0; range, 69.6 to 95.0) compared to EG (median, 11.62; range, 3.83 to 50.1) and NG (median, 7.33; range, 6.2 to 28.1) (P<0.001) in the training context. These results suggest impairment of contextual fear in birds who received lesions one day after conditioning and a role for the hippocampus in the modulation of emotional aversive memories in pigeons

Anterograde effects of a single electroconvulsive shock on inhibitory avoidance and on cued fear conditioning

A single electroconvulsive shock (ECS) or a sham ECS was administered to male 3-4-month-old Wistar rats 1,2, and 4 h before training in an inhibitory avoidance test and in cued classical fear conditioning (measured by means of freezing time in a new environment). ECS impaired inhibitory avoidance at all times and, at 1 or 2 h before training, reduced freezing time before and after re-presentation of the ECS. These results are interpreted as a transient conditioned simulus (CS)-induced anxiolytic or analgesic effect lasting about 2 h after a single treatment, in addition to the known amnesic effect of the stimulus. This suggests that the effect of anterograde learning impairement is demonstrated unequivocally only when the analgesic/anxiolytic effect is over (about 4 h after ECS administration) and that this impairment of learning is selective, affecting inhibitory avoidance but not classical fear conditioning to a discrete stimulus.

Psiquiatria pavloviana: a mobilidade cortical e as neuroses experimentais / Pavlov's psychiatry: the cortical mobility and the experimental neuroses

Ivan Petrovitch Pavlov (1849/1936), descobridor dos reflexos condicionados, demonstrou com suas experiências em animais que o córtex é um órgäo em permanente mobilidade graças às propriedades de irradiaçäo e concentraçäo dos processos fundamentais da atividade nervosa superior, a excitaçäo e a inibiçäo. Demonstrou, ainda, que cada ponto excitado cria uma área de inibiçäo nas regiöes vizinhas (induçäo negativa) e cada ponto inibido gera o fenômeno inverso na cortiça cerebral (induçäo positiva). O conjunto desta atividade foi denominado de induçäo recíproca, segundo a qual há uma delimitaçäo exata e minuciosa dos pontos excitados e inibidos. Durante as experiências era freqüente o aparecimento de transtornos funcionais da atividade normal dos hemisférios cerebrais, dando origem a novas investigaçöes que culminaram com o importante capítulo das neuroses experimentais, distúrbios patológicos que aparecem quando ultrapassados os limites da capacidade de trabalho da cortiça cerebral dos animais

La actividad nerviosa superior / Higher nervous activity

Se expone la Actividad Nerviosa Superior considerándola como una nueva ciencia que inicia su camino gracias a la ingente labor de I.P. Pavlov. Se explica como la corteza cerebral a través de sus conexiones con la sub-corteza y por medio de ésta con todo el organismo va a constituir el centro superior de regulación orgánica. Se plantea como el reflejo condicionado, proceso al mismo tiempo fisiológico y psíquico, termina con el esquema dualista que existía en las ciencias del hombre. Se expone como con ayuda de los reflejos condicionados se integran todos los aspectos de la actividad del organismo: vegetativa, de conducta, psíquica

Effect of mid-dorsal caudate nucleus on conditioning for pain stimulus in rats.

Male rats were subjected to conditioning, with light source as conditioned stimulus, followed by a noxious stimulus applied to the tail as unconditioned stimulus. There was development of conditioned response after a few days, which was inhibited later on.