RESUMO
In action sequences, the eyes and hands ought to be coordinated in precise ways. The mechanisms governing the architecture of encoding and action of several effectors remain unknown. Here we study hand and eye movements in a sequential task in which letters have to be typed while they move down through the screen. We observe a strict refractory period of about 200 ms between the initiation of manual and eye movements. Subjects do not initiate a saccade just after typing and do not type just after making the saccade. This refractory period is observed ubiquitously in every subject and in each step of the sequential task, even when keystrokes and saccades correspond to different items of the sequence-for instance when a subject types a letter that has been gazed at in a preceding fixation. These results extend classic findings of dual-task paradigms, of a bottleneck tightly locked to the response selection process, to unbounded serial routines. Interestingly, while the bottleneck is seemingly inevitable, better performing subjects can adopt a strategy to minimize the cost of the bottleneck, overlapping the refractory period with the encoding of the next item in the sequence.
Assuntos
Movimentos Oculares/fisiologia , Mãos/fisiologia , Desempenho Psicomotor/fisiologia , Período Refratário Psicológico/fisiologia , Adulto , Feminino , Humanos , Masculino , Adulto JovemRESUMO
In spite of its massively parallel architecture [1], the human brain is fundamentally limited if required to perform two tasks at the same time [2, 3]. This limitation can be studied with the psychological refractory period (PRP) paradigm, where two stimuli that require speeded responses occur in close succession [4]. Interference generally takes the form of a delay in the time to respond to the second stimulus [5]. Previous studies suggested that sensory decisions require the accumulation of sensory evidence [6, 7] and that the PRP reflects the inability to form more than one decision at a time [4, 8]. In the present study, we used a psychophysical reverse-correlation technique [9, 10] to measure the time-course of evidence accumulation during the PRP. We found that the accumulation of evidence could occur during the PRP albeit with a reduced efficiency, which implies that multiple decision processes can occur in parallel in the human brain. In addition to the reduced efficiency of evidence accumulation, our results uncover an additional delay in the routing of the decision to motor structures during the PRP, which implies that the process of sensory decision making is separable from the preparation of a motor response [11-13].
Assuntos
Tomada de Decisões , Período Refratário Psicológico/fisiologia , Percepção Auditiva/fisiologia , Humanos , Experimentação Humana não TerapêuticaRESUMO
Which cognitive processes are accessible to conscious report? To study the limits of conscious reportability, we designed a novel method of quantified introspection, in which subjects were asked, after each trial of a standard cognitive task, to estimate the time spent completing the task. We then applied classical mental-chronometry techniques, such as the additive-factors method, to analyze these introspective estimates of response time. We demonstrate that introspective response time can be a sensitive measure, tightly correlated with objective response time in a single-task context. In a psychological-refractory-period task, however, the objective processing delay resulting from interference by a second concurrent task is totally absent from introspective estimates. These results suggest that introspective estimates of time spent on a task tightly correlate with the period of availability of central processing resources.
Assuntos
Atenção , Percepção do Tempo , Cognição , Estado de Consciência , Humanos , Tempo de Reação , Período Refratário Psicológico , Adulto JovemRESUMO
BACKGROUND: When two tasks are presented within a short interval, a delay in the execution of the second task has been systematically observed. Psychological theorizing has argued that while sensory and motor operations can proceed in parallel, the coordination between these modules establishes a processing bottleneck. This model predicts that the timing but not the characteristics (duration, precision, variability...) of each processing stage are affected by interference. Thus, a critical test to this hypothesis is to explore whether the quality of the decision is unaffected by a concurrent task. METHODOLOGY/PRINCIPAL FINDINGS: In number comparison--as in most decision comparison tasks with a scalar measure of the evidence--the extent to which two stimuli can be discriminated is determined by their ratio, referred as the Weber fraction. We investigated performance in a rapid succession of two non-symbolic comparison tasks (number comparison and tone discrimination) in which error rates in both tasks could be manipulated parametrically from chance to almost perfect. We observed that dual-task interference has a massive effect on RT but does not affect the error rates, or the distribution of errors as a function of the evidence. CONCLUSIONS/SIGNIFICANCE: Our results imply that while the decision process itself is delayed during multiple task execution, its workings are unaffected by task interference, providing strong evidence in favor of a sequential model of task execution.
Assuntos
Desempenho Psicomotor/fisiologia , Tempo de Reação/fisiologia , Período Refratário Psicológico , Estimulação Acústica , Adulto , Mapeamento Encefálico , Cognição , Humanos , Aprendizagem , Masculino , Processos Mentais , Modelos Estatísticos , Reprodutibilidade dos Testes , Fatores de Tempo , Percepção VisualRESUMO
The psychological refractory period (PRP) refers to the fact that humans typically cannot perform two tasks at once. Behavioral experiments have led to the proposal that, in fact, peripheral perceptual and motor stages continue to operate in parallel, and that only a central decision stage imposes a serial bottleneck. We tested this model using neuroimaging methods combined with innovative time-sensitive analysis tools. Subjects performed a dual-task visual-auditory paradigm in which a delay of 300 ms was injected into the auditory task either within or outside of the dual-task interference period. Event-related potentials indicated that the first approximately 250 ms of processing were insensitive to dual-task interference, and that the PRP was mainly reflected in a delayed global component. By a clustering analysis based on time-resolved functional magnetic resonance imaging, we identified networks with qualitatively different timing properties: sensory areas tracked the objective time of stimulus presentation, a bilateral parietoprefrontal network correlated with the PRP delay, and an extended bilateral network that included bilateral posterior parietal cortex, premotor cortex, supplementary motor area, anterior part of the insula, and cerebellum was shared by both tasks during the extent of dual-task performance. The results provide physiological evidence for the coexistence of serial and parallel processes within a cognitive task.
Assuntos
Percepção Auditiva/fisiologia , Mapeamento Encefálico , Encéfalo/fisiologia , Período Refratário Psicológico/fisiologia , Percepção Visual/fisiologia , Estimulação Acústica , Adulto , Encéfalo/irrigação sanguínea , Eletroencefalografia/métodos , Potenciais Evocados/fisiologia , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética/métodos , Masculino , Modelos Psicológicos , Oxigênio/sangue , Estimulação Luminosa/métodos , Prática Psicológica , Valor Preditivo dos Testes , Análise de Componente Principal , Tempo de Reação/fisiologia , Análise e Desempenho de TarefasRESUMO
The obsessive compulsive disorder (TOC) is a clinical disorder which represents a challenge for therapists, since not only the acute clinical state but also its evolution shows difficulties in its treatment , with high figures of little response or frequent relapses. Antidepressants have been considered as the drugs of choice, using other biological techniques or psychotherapy in parallel form to the antidepressants or because of deficient response to the drugs. The optimization of treatment depends on the correct use of drugs, for the adequate time or the use of a combination of antidepressants. There has been use of antipsychotics, studies which require a longer space of time in order to establish a clinical answer. In actuality these states, together with others, have been incorporated to the concept specter of obsessive-compulsiveness, which in conjunction with new therapeutic procedures with more mythological evidence could be of help to these syndromes.
El Trastorno obsesivo compulsivo (TOC) es un cuadro clínico que representa un desafío para los terapeutas, pues tanto el cuadro clínico agudo como su evolución muestra dificultades en su tratamiento, con cifras altas de escasa respuesta o recaídas frecuentes. Los antidepresivos han sido considerados como los fármacos de primera elección, empleándose otras técnicas biológicas o psicoterapéuticas ya sea en forma paralela al uso de antidepresivos o bien luego de la falta de respuesta a estos fármacos. La optimización del tratamiento depende del correcto uso de los fármacos, por tiempos adecuados o el uso de combinaciones de antidepresivos. Se han utilizado antipsicóticos, estudios que requieren un plazo más prolongado para establecer su respuesta clínica. En la actualidad estos cuadros junto a otros han sido incorporados bajo el concepto de espectro obsesivo-compulsivo, que junto a nuevos procedimientos terapéuticos con mayor evidencia metodológica podrán ser de ayuda en estos trastornos.
Assuntos
Humanos , Masculino , Feminino , Antidepressivos/uso terapêutico , Transtorno Obsessivo-Compulsivo/tratamento farmacológico , Período Refratário PsicológicoRESUMO
OBJETIVOS E MÉTODO: Os transtornos de humor estão entre os transtornos psiquiátricos mais prevalentes. Apesar de novas descobertas e avanços no estudo das bases neurobiológicas e abordagens terapêuticas no transtorno bipolar e depressão recorrente, elevadas taxas de recorrência, sintomas subsindrômicos persistentes e refratariedade terapêutica são aspectos clínicos desafiadores e precisam ser abordados. O objetivo desta revisão da literatura é o de avaliar os conceitos e critérios de resistência e refratariedade ao tratamento, e evidenciar as principais alternativas terapêuticas para transtornos do humor resistentes aos tratamentos disponíveis. RESULTADOS: Fatores genéticos, erro diagnóstico e de tratamento, não-aderência, e estressores biológicos e psicossociais podem levar à perda de mecanismos regulatórios e ao aumento na prevalência de casos de refratariedade nos transtornos de humor. Com relação aos tratamentos disponíveis, o uso de doses apropriadas, seguido por associação com um segundo ou terceiro fármaco, e após, se indicado, a troca de medicação, são etapas necessárias na busca de melhor eficácia. Entretanto, no paradigma de refratariedade terapêutica, tratamentos atuando em sistemas já conhecidos, especialmente monoaminas, freqüentemente apresentam limitada eficácia. Assim, a busca por tratamentos mais eficazes para os transtornos de humor torna-se um aspecto chave para diminuir sua morbidade. CONCLUSÃO: Estratégias focadas na regulação de vias ativadoras de neuroplasticidade, incluindo agentes antiglutamatérgicos, antagonistas de receptor glucocorticóide e neuropeptídeos, podem representar opções terapêuticas promissoras.
OBJECTIVE AND METHOD: Mood disorders are the most prevalent psychiatric disorders. Despite new insights and advances on the neurobiological basis and therapeutic approaches for bipolar disorders and recurrent depression, elevated prevalence of recurrence, persistent sub-syndromal symptoms and treatment resistance are challenging aspects and need to be urgently addressed. The objective of this literature review is to evaluate the current concepts of treatment resistance and refractoriness in mood disorders. RESULTS: Genetic factors, misdiagnosis, use of inappropriate pharmacological approaches, non-compliance and biological/psychosocial stressors account for dysfunctions in mood regulation, thus increasing the prevalence of refractory mood disorders. Regarding available treatments, the use of effective doses during an adequate period followed by augmentation with a second and/or third agent, and finally switching to other agent are steps frequently necessary to optimize efficacy. However, in the treatment-resistant paradigm, drugs mimicking standard strategies, which target preferentially the monoaminergic system, can present reduced therapeutic effects. Thus, the search for new effective treatments for mood disorders is critical to decreasing the overall morbidity secondary to treatment resistance. CONCLUSION: Emerging strategies targeting brain plasticity pathways or 'plasticity enhancers', including antiglutamatergic drugs, glucocorticoid receptor antagonists and neuropeptides, have been considered promising therapeutic options for difficult-to-treat mood disorders.
Assuntos
Humanos , Antidepressivos/uso terapêutico , Antipsicóticos/uso terapêutico , Transtornos do Humor/tratamento farmacológico , Transtorno Bipolar/tratamento farmacológico , Transtorno Depressivo Maior/tratamento farmacológico , Resistência a Medicamentos , Quimioterapia Combinada , Transtornos do Humor/fisiopatologia , Transtornos do Humor/psicologia , Plasticidade Neuronal , Período Refratário Psicológico , Estresse Psicológico/complicaçõesRESUMO
OBJECTIVE AND METHOD: Mood disorders are the most prevalent psychiatric disorders. Despite new insights and advances on the neurobiological basis and therapeutic approaches for bipolar disorders and recurrent depression, elevated prevalence of recurrence, persistent sub-syndromal symptoms and treatment resistance are challenging aspects and need to be urgently addressed. The objective of this literature review is to evaluate the current concepts of treatment resistance and refractoriness in mood disorders. RESULTS: Genetic factors, misdiagnosis, use of inappropriate pharmacological approaches, non-compliance and biological/psychosocial stressors account for dysfunctions in mood regulation, thus increasing the prevalence of refractory mood disorders. Regarding available treatments, the use of effective doses during an adequate period followed by augmentation with a second and/or third agent, and finally switching to other agent are steps frequently necessary to optimize efficacy. However, in the treatment-resistant paradigm, drugs mimicking standard strategies, which target preferentially the monoaminergic system, can present reduced therapeutic effects. Thus, the search for new effective treatments for mood disorders is critical to decreasing the overall morbidity secondary to treatment resistance. CONCLUSION: Emerging strategies targeting brain plasticity pathways or 'plasticity enhancers', including antiglutamatergic drugs, glucocorticoid receptor antagonists and neuropeptides, have been considered promising therapeutic options for difficult-to-treat mood disorders.
Assuntos
Antidepressivos/uso terapêutico , Antipsicóticos/uso terapêutico , Transtornos do Humor/tratamento farmacológico , Transtorno Bipolar/tratamento farmacológico , Transtorno Depressivo Maior/tratamento farmacológico , Resistência a Medicamentos , Quimioterapia Combinada , Humanos , Transtornos do Humor/fisiopatologia , Transtornos do Humor/psicologia , Plasticidade Neuronal , Período Refratário Psicológico , Estresse Psicológico/complicaçõesRESUMO
A paradigm based on conditioned suppression of ongoing motor activity, sensitive to latent inhibition (LI), was developed and tested in healthy volunteers. Subjects were trained to move disks from one peg to another with a high degree of regularity in the Tower of Toronto puzzle, a well-known cognitive skill learning task. Once this was achieved, they were submitted to a Pavlovian conditioning procedure. The conditioned stimulus (CS) was a pure tone and the unconditioned stimulus (US) a loud white noise. The resulting response suppression was assessed by a transient increase in latency of the hand movements. In control subjects, there was non-contingent CS and US presentation. The results evidenced conditioning after a single CS-US pairing. Following five preexposures to the to-be-conditioned CS, however, conditioning was abolished, seemingly expressing LI. Because a weak unconditioned response to the tone was observed after its first two presentations, an additional experiment was performed with two preexposures to the to-be-conditioned CS. With such procedure, conditioning was obtained, supporting the existence of LI in the preceding experiment. These results indicate that the present paradigm may be useful for the study of LI in human subjects, having the advantage of being similar to the experimental conditions used in the majority of LI studies in experimental animals.
Assuntos
Aprendizagem por Associação , Cognição , Condicionamento Clássico , Inibição Psicológica , Período Refratário Psicológico , Estimulação Acústica , Adulto , Feminino , Habituação Psicofisiológica , Humanos , Masculino , Modelos Psicológicos , Testes NeuropsicológicosRESUMO
The sensitivity of latent inhibition (LI) to amphetamine has been tested in humans with a paradigm close to the conditioned emotional response suppression currently used in experimental animals. The conditioned stimulus (CS) was a tone, the unconditioned stimulus (US) a strong white noise, and the response a transient delay in a regular sequence of hand movements in the resolution of the Tower of Toronto puzzle. The aim of this study was to verify whether the previously reported, disruptive effect of CS preexposure on conditioning really represents LI, by examining its sensitivity to amphetamine. Three groups of healthy volunteers received placebo, 5 or 10 mg of dexamphetamine sulphate, respectively, in a double-blind experimental design. The preexposure, conditioning and test phases were carried out under either amphetamine or placebo. The non preexposed groups treated with amphetamine were not different from the non preexposed placebo group, indicating that amphetamine did not affect conditioning. Among the preexposed groups, those receiving 10 mg of amphetamine showed normal rates of conditioning, whereas those treated with either 5 mg of amphetamine or placebo showed LI. Similar results have been reported in experimental animals. This sensitivity to amphetamine suggests that the present paradigm may be used to study LI in humans.
Assuntos
Estimulantes do Sistema Nervoso Central/farmacologia , Cognição/efeitos dos fármacos , Condicionamento Clássico/efeitos dos fármacos , Dextroanfetamina/farmacologia , Inibição Psicológica , Período Refratário Psicológico , Estimulação Acústica , Adulto , Análise de Variância , Método Duplo-Cego , Feminino , Humanos , Masculino , Testes NeuropsicológicosRESUMO
Os autores relatam o caso de um paciente de 36 anos, portador de transtorno bipolar tipo I, com predominio de episodios maniacos, refratario a varios esquemas terapeuticos ha mais de uma decada. Com a introducao da clozapina em associacao com valproato de sodio, houve remissao do quadro de humor e foi possivel reduzir a sua politerapia farmacologica a apenas duas medicacoes. Uma revisao de literatura sobre o papel da clozapina no transtorno bipolar...