RESUMO
The ERN or Ne is a component of the event-related brain potential that occurs when human subjects make errors in reaction time tasks. It is observed in response-locked averages, time-locked to the execution of the incorrect response. Recent research has reported that this component is present on correct response trials, thereby challenging the idea that the component is specifically related to error-processing. In this paper, we argue that the ERN or Ne observed on correct trials can be attributed to one or both of two factors: either there is error-processing on correct trials, and/or the response-locked averages used to derive the ERN/Ne are contaminated by negative components evoked by the stimulus. For this reason, there is no reason to abandon theories that relate the ERN/Ne to error-processing.
Assuntos
Potenciais Evocados/fisiologia , Processos Mentais/fisiologia , Artefatos , Encéfalo/fisiologia , Humanos , Análise e Desempenho de TarefasRESUMO
Fournier, L. R., Eriksen, C. W. and Bowd, C. (1998. Multiple feature discrimination faster than single feature discrimination within the same object? Perception & Psychophysics 60, 1384-1405) found that judging the presence of multiple features within an object is faster than judging the presence of the least discriminable of these features alone (multiple feature benefits, MFBs). When an 'absent' response is required, responses are slower when some of the relevant (target) features are present (multiple feature costs, MFCs). The present study utilized psychophysiological measures (of the event-related brain potential and the electromyogram) to determine the contributions of response priming and stimulus evaluation processes (P300 latency) to these effects. P300 latency and reaction time (RT) both showed evidence of MFBs and MFCs. These findings suggest that MFBs and MFCs can be attributed to processing that occurs prior to response selection. No dissociations between P300 latency and RT measures were found for 'present' responses across the single and multiple feature judgements. However, for 'absent' responses, partial dissociations were found between these measures, and partial errors and longer response execution intervals were observed more often when an object contained some target features. These findings suggest that response priming contributes to MFCs, but may not contribute to MFBs.
Assuntos
Discriminação Psicológica/fisiologia , Potenciais Evocados P300/fisiologia , Potencial Evocado Motor/fisiologia , Potenciais Evocados Visuais/fisiologia , Detecção de Sinal Psicológico/fisiologia , Adulto , Sinais (Psicologia) , Eletromiografia , Feminino , Humanos , Masculino , Modelos Psicológicos , Período Refratário PsicológicoRESUMO
The nature of error detection as manifested by the error-related negativity was examined in both a Sternberg memory search task and a visual search task. Both tasks were performed in conditions with consistent or varied stimulus-response mapping and loads of three or six letters. After subjects were trained extensively in all conditions, they performed the tasks throughout the night without sleeping. The data suggest that the effectiveness of error detection decreases over time because of a decrease in the quality of perceptual processing. Error detection also suffers when performance requires more search-related resources. In both cases, the representation of the correct response is compromised. These results indicate that error detection depends on the same perceptual and cognitive processes that are required for correct performance.
Assuntos
Processos Mentais/fisiologia , Desempenho Psicomotor/fisiologia , Vigília/fisiologia , Adulto , Atenção/fisiologia , Humanos , Masculino , Memória/fisiologiaRESUMO
The psychophysiological approach was used to evaluate the effects of feature similarity and "intrinsic response mapping" on the flanker compatibility effect. Symbol (e.g., < > < and <) and letter arrays (e.g., HCH and SCS) were used. Results showed that delays in stimulus evaluation and both peripheral and central response competition contributed to the compatibility effect, with the contribution of these processes depending on feature similarity and the intrinsic response mapping of the stimuli. For letter stimuli, the difference in the size of the compatibility effect for similar and dissimilar arrays could be accounted for in terms of stimulus evaluation. For symbol arrays, differences in size of the compatibility effect could be accounted for by response competition. Thus, symbol and letter arrays do not appear to be processed differently; what is different is the degree to which stimulus and response-related processes are affected by incompatibility.
Assuntos
Atenção/fisiologia , Aprendizagem por Discriminação/fisiologia , Orientação/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Adulto , Córtex Cerebral/fisiologia , Potenciais Evocados P300/fisiologia , Feminino , Humanos , Masculino , Psicofisiologia , Tempo de Reação/fisiologiaRESUMO
Recent research has suggested that there is a component of the event-related brain potential, the error-related negativity (ERN), that is associated with error detection and remedial actions such as error inhibition, immediate error correction, or error compensation. The present experiment used a go/no-go task to define more precisely the functional significance of this component. In this task, an ERN was observed for incorrect responses on go trials (errors of choice) and for responses on no-go trials (errors of action). Because errors of action cannot be corrected immediately by executing another response, these results indicate that the process manifested by the ERN is not dependent on immediate error correction. Other aspects of the data converge in suggesting that the ERN process is more closely related to error detection and that the connections between detection and remedial actions may depend on the task situation.
Assuntos
Encéfalo/fisiologia , Desempenho Psicomotor/fisiologia , Adulto , Eletroencefalografia , Eletromiografia , Potenciais Evocados/fisiologia , Feminino , Humanos , Masculino , Tempo de Reação/fisiologiaRESUMO
Human performance is seldom perfect, and even when an overt response is correct it may be accompanied by partial-error activity that does not achieve the level of a complete incorrect response. Partial errors can be detected in measures of the lateralized readiness potential, of the electromyogram, and of response force. Correct responses accompanied by partial errors tend to have slower reaction times than "clean" correct responses (because of response competition), and condition differences in reaction time can, on some occasions, be explained in terms of differences in the incidence of partial errors. In two-choice reaction time tasks, partial errors are more frequent when the imperative stimulus contains information that favors both responses, than when it contains information that favors only one response. The non-random nature of partial errors supports the inference that partial information about the stimulus is used to guide responses. A similar inference is supported by the observation that, in hybrid choice Go/No-go tasks, the kinds of partial errors that follow a No-go stimulus represent activation of the response that would have been correct had the stimulus been a Go stimulus. Finally, we note that the human processing system is capable of monitoring its own behavior and of initiating remedial actions if necessary. The activity of an error-detection system, as revealed by measures of the error-related negativity, is related to the degree to which responses are slowed after errors.
Assuntos
Atenção , Desempenho Psicomotor , Tempo de Reação , Nível de Alerta , Comportamento de Escolha , HumanosRESUMO
We recorded event-related brain potentials (ERPs) from 13 patients with chronic fatigue syndrome (CFS) and 13 matched normal controls. To assess attentional and memory deficits in CFS patients, we used a short-term memory task in which events occurred in different spatial locations and the patients made a rapid-response (RT) when a letter in a relevant location matched a letter in the prememorized set (Attention paradigm). Time-on-task effects on the ERP and behavioral measures were assessed over the 2 1/4-hour duration of this task. Both groups also performed a visual Oddball paradigm, with an RT, before and after the Attention paradigm. The patients' RTs were much more variable and, in nine of 13 cases, slower than the mean RT of the controls in both paradigms. The patients' memory performance was not significantly different from that of the controls and there were no group differences in the overall amplitude, latency, or scalp distribution of the N1, P2, N2, or P300 components of the ERP in either paradigm. The ERP and performance data from both paradigms suggest that perceptual, attentional, and short-term memory processes were unaffected in CFS patients and that the differences were limited to response-related processes.
Assuntos
Atenção/fisiologia , Síndrome de Fadiga Crônica/fisiopatologia , Síndrome de Fadiga Crônica/psicologia , Memória de Curto Prazo/fisiologia , Adulto , Análise de Variância , Escolaridade , Potenciais Evocados/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
The effects of stimulus quality on the amplitude, peak latency, onset latency, and duration of the P300 component of the event-related brain potential were studied in patients with either a left or a right anterior temporal lobectomy and in normal controls. Stimulus quality was reduced by adding "noise" letters to words which signalled either a left or a right hand button press. Consistent with an interpretation that stimulus quality affects the subject's degree of equivocation, P300 peak latency, reaction time, and errors were all inversely related to stimulus quality, whereas P300 amplitude was directly related to stimulus quality. There were no significant differences between normal controls and either patient group for any of the ERP parameters or reaction time. Right temporal lobectomy patients made, however, significantly more errors, particularly on the catch trials, which suggests that they did not process the stimuli as thoroughly and accurately as the subjects in the other two groups. The absence of significant group differences in either the lateral symmetry or overall P300 amplitude extends the evidence against the idea that anterior temporal lobe structures make any substantial contribution to the scalp P300 in a visual discrimination paradigm. Because of observed delays in the onset of P300 in the low-quality stimulus condition, procedures were developed to quantify both P300 onset latency and P300 duration. Reduced stimulus quality significantly increased P300 onset latency whereas P300 duration remained unaffected, indicating that stimulus categorization must occur prior to, and not during, P300.
Assuntos
Nível de Alerta/fisiologia , Atenção/fisiologia , Aprendizagem por Discriminação/fisiologia , Dominância Cerebral/fisiologia , Epilepsia do Lobo Temporal/cirurgia , Reconhecimento Visual de Modelos/fisiologia , Complicações Pós-Operatórias/fisiopatologia , Psicocirurgia , Lobo Temporal/cirurgia , Adulto , Eletroencefalografia , Epilepsia do Lobo Temporal/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Mascaramento Perceptivo/fisiologia , Tempo de Reação/fisiologia , Lobo Temporal/fisiopatologiaRESUMO
In this study the organization of information processing in a selective search task was examined by analyzing event-related potentials. This task consisted of searching for target letters in a relevant (attended) color. The ERPs revealed two different effects of attention: an early occipital negativity (+/- 150 ms) reflecting feature-specific attention, and a later, central N2b component (+/- 240 ms) reflecting covert orienting of attention. A later, prolonged negativity (search-related negativity) (+/- 300 ms), maximal at Cz, was related to controlled search to letters in the attended color. Detection of relevant targets resulted in a parietal P3b component. Depending on stimulus presentation conditions an earlier response to both attended and unattended targets was found: an N2 component (+/- 250 ms). In these same conditions, C'3-C'4 asymmetries (Corrected Motor Asymmetries--CMA) suggested motor activation at +/- 300 ms, in the same time range as search-related negativity. It was argued that N2 and CMA suggest the existence of a preattentive target detection system, operating in parallel with a slower serial attentive system, as reflected by N2b and search negativity.
Assuntos
Nível de Alerta , Atenção , Percepção de Cores , Percepção de Forma , Orientação , Reconhecimento Visual de Modelos , Adulto , Feminino , Humanos , Masculino , Rememoração Mental , Desempenho PsicomotorRESUMO
ERPs and performance were measured in divided and focussed attention visual search tasks. In focussed attention tasks, to-be-attended and to-be-ignored letters were presented simultaneously. We varied display load, mapping conditions and display size. RT, P3b-latency and negativity in the ERP associated with controlled search all increased with display load. Each of these measures showed selectivity of controlled search, in that they decreased with focussing of attention. An occipital N230, on the other hand, was not sensitive to focussing of attention, but was primarily affected by display load. ERPs to both attended and unattended targets in focussed attention conditions showed and N2 compared to nontargets, suggesting that both automatic and controlled letter classifications are possible. These effects were not affected by display size. Consistent mapping resulted in shorter RT and P3b-latency in divided attention conditions, compared to varied mapping conditions, but had no effect in focussed attention conditions.