Influence of cueing on the preparation and execution of untrained and trained complex motor responses

This study investigated the influence of cueing on the performance of untrained and trained complex motor responses. Healthy adults responded to a visual target by performing four sequential movements (complex response) or a single movement (simple response) of their middle finger. A visual cue preceded the target by an interval of 300, 1000, or 2000 ms. In Experiment 1, the complex and simple responses were not previously trained. During the testing session, the complex response pattern varied on a trial-by-trial basis following the indication provided by the visual cue. In Experiment 2, the complex response and the simple response were extensively trained beforehand. During the testing session, the trained complex response pattern was performed in all trials. The latency of the untrained and trained complex responses decreased from the short to the medium and long cue-target intervals. The latency of the complex response was longer than that of the simple response, except in the case of the trained responses and the long cue-target interval. These results suggest that the preparation of untrained complex responses cannot be completed in advance, this being possible, however, for trained complex responses when enough time is available. The duration of the 1st submovement, 1st pause and 2nd submovement of the untrained and the trained complex responses increased from the short to the long cue-target interval, suggesting that there is an increase of online programming of the response possibly related to the degree of certainty about the moment of target appearance.

What ethologically based models have taught us about the neural systems underlying fear and anxiety

Classical Pavlovian fear conditioning to painful stimuli has provided the generally accepted view of a core system centered in the central amygdala to organize fear responses. Ethologically based models using other sources of threat likely to be expected in a natural environment, such as predators or aggressive dominant conspecifics, have challenged this concept of a unitary core circuit for fear processing. We discuss here what the ethologically based models have told us about the neural systems organizing fear responses. We explored the concept that parallel paths process different classes of threats, and that these different paths influence distinct regions in the periaqueductal gray - a critical element for the organization of all kinds of fear responses. Despite this parallel processing of different kinds of threats, we have discussed an interesting emerging view that common cortical-hippocampal-amygdalar paths seem to be engaged in fear conditioning to painful stimuli, to predators and, perhaps, to aggressive dominant conspecifics as well. Overall, the aim of this review is to bring into focus a more global and comprehensive view of the systems organizing fear responses.

The extinction of conditioned fear: structural and molecular basis and therapeutic use

OBJECTIVE: Through association, a large variety of stimuli acquire the property of signaling pleasant or aversive events. Pictures of a wedding or of a plane disaster may serve as cues to recall these events and/or others of a similar nature or emotional tone. Presentation of the cues unassociated with the events, particularly if repeated, reduces the tendency to retrieve the original learning based on that association. This attenuation of the expression of a learned response was discovered by Pavlov 100 years ago, who called it extinction. In this article we review some of the most recent findings about the behavioral and biochemical properties of extinction. RESULTS AND DISCUSSION: It has been shown that extinction is a new learning based on a new link formed by the cues and the absence of the original event(s) which originated the first association. Extinction does not consist of the erasure of the original memory, but of an inhibition of its retrieval: the original response reappears readily if the former association is reiterated, or if enough time is allowed to pass (spontaneous recovery). Extinction requires neural activity, signaling pathways, gene expression and protein synthesis in the ventromedial prefrontal cortex and/or basolateral amygdala, hippocampus, entorhinal cortex and eventually other areas. The site or sites of extinction vary with the task. CONCLUSIONS: Extinction was advocated by Freud in the 1920's for the treatment of phobias, and is used in cognitive therapy to treat diseases that rely on conditioned fear (phobias, panic, and particularly posttraumatic stress disorder). The treatment of learned fear disorders with medications is still unsatisfactory although some have been shown useful when used as adjuncts to behavioral therapy.

OBJETIVO: Muitos estímulos podem adquirir características prazerosas ou aversivas por meio da formação de associações. Fotografias de um casamento ou de um acidente aeronáutico podem servir como dicas para lembrar esses eventos e outros de natureza ou caráter emocional semelhante. Porém, sabe-se que a apresentação repetida de uma dica na ausência do estímulo ao qual está associada reduz a probabilidade de expressão da memória em questão. Este fenômeno de atenuação foi descoberto por Pavlov há quase 100 anos, recebendo o nome de extinção. Neste artigo de revisão, comentamos alguns dos achados mais recentes a respeito das propriedades comportamentais e bioquímicas do processo de extinção de memórias. RESULTADOS E DISCUSSÃO: Tem sido demonstrado que a extinção não envolve esquecimento, mas a inibição da expressão da memória original juntamente com um novo aprendizado, que inclui a formação de uma relação entre a dica e a ausência do estímulo que originou a primeira associação. De fato, a memória original reaparece rapidamente após a re-exposição ao estímulo adequado ou, simplesmente, com o passar do tempo (recuperação espontânea). A extinção requer atividade neural, diferente vias de sinalização neuronal, incluindo a expressão de genes e a síntese de proteínas, em diferentes áreas do cérebro. Estas variam com a tarefa, mas distintos estudos sugerem que tanto o córtex pré-frontal medial como o córtex entorrinal, a amígdala basolateral, hipocampo entre outras áreas desempenham um papel fundamental neste processo. CONCLUSÕES: Nos anos 20 do século XX, Freud recomendou a utilização de terapias baseadas na extinção para o tratamento de fobias. Hoje, a extinção é utilizada na terapia cognitiva de distintas desordens, incluindo o pânico e o estresse pós-traumático. Ainda que alguns medicamentos tenham demonstrado sua eficácia como coadjuvantes na terapia comportamental do medo aprendido, a resposta destes pacientes ao tratamento farmacológico ainda...

Context and Pavlovian conditioning

Procedurally, learning has to occur in a context. Several lines of evidence suggest that contextual stimuli actively affect learning and expression of the conditional response. The experimental context can become associated with the unconditional stimulus (US), especially when the US is presented in a context in the absence of a discrete conditional stimulus (CS). Moreover, context can modulate CS-US associations. Finally, it appears that context can become associated with the CS when it is presented before the CS-US training. The purpose of the present paper is to review some of the relevant literature that considers the context as an important feature of Pavlovian conditioning and to discuss some of the main learning theories that incorporate the context into their theoretical framework. The paper starts by mentioning historical positions that considered context an important variable in conditioning and then describes how the approach to contextual conditioning changed with the modem study of Pavlovian conditioning. Various forms of measurement of context conditioning are presented and the associative strength attached to context in several experimental paradigms is examined. The possible functions that context may acquire during conditioning are pointed out and related to major learning theories. Moreover, the effect of certain neurological manipulations on context conditioning is presented and these results are discussed in terms of possible functions that the context might acquire during Pavlovian conditioning. It is concluded that contextual stimuli acquire different functions during normal conditioning. A procedure in which animals are exposed to an aversive US immediately after they are placed in the experimental context is suggested as a useful control for the study of context conditioning.

Single neuronal activities from CA3 region of hippocampus during conditioning, in mobile unanaesthetised conscious rabbits.

Single neuronal activities of 93 units from CA3 region of hippocampus were studied in unanaesthetised mobile rabbits. Effects of repeated reinforced conditioned stimuli (CS+) were observed on these neuronal firing pattern. The conditioned stimuli (CS) consisted of a tone 600 Hz for 6 seconds which was reinforced by a subcutaneous electrical shock (0.4 V, frequency 250 sec, and pulse width 300 microsec) for one second duration (CS+). Ten such CS+ were applied at the gap of 5 min, in between. As majority of CA3 neurons showed irregular spontaneous activities-the histograms drawn after calculation of interspike intervals showed a definite pattern of discharge which could be compared before, during and after multiple CS+. Two groups of neurons could be identified by their resting firing pattern. One group consisting of 21 neurons (22.5% approximately) showed complex spikes, with spike frequency less than 2 to 8 per sec. They were complex spike cells (CSC). The other group consisting of majority of neurons (72 neurons, 77.5% approximately) showed comparatively high spike frequency greater than 8 to 40 per sec (theta cells). Both the group of neurons reacted tonically to CS+. All complex spike cells and 54% of theta cells showed inhibitory reaction and 46% of theta cells showed excitatory reaction to CS+. But with repeated presentation (4th to 5th) of CS+ the reaction gradually declined and finally after tenth CS+ it disappeared and resting firing pattern was observed. Thus it seems that the neurons of CA3 region have an intrinsic habituation capability. The probable cause, mechanism and the significance for the habituation has been discussed here.

Conditioned turning and functional recovery after unilateral substantia nigra lesion in rats

In order to invetigate whether conditioned circling interferes with recovery from turning induced by unilateral substantia nigra (SN) lesion, rats were trained to turn either ipsi-or contralateral to the lesioned side before and after the lesion was made. Two yoked groups served as controls. The number of turns contralateral to the trained side was significantly lower in relation to the pre-lesion value for the ipsilateral trained group and remained so until the end of the experiment. A partial recovery was observed on the 19th post-lesion day for the contralateral trained group. The results are discussed in terms of additive effects from training and the lesion symptoms