RESUMEN
What mechanisms underlie the transfer of a working memory representation into a higher-level code for guiding future actions? Electrophysiological correlates of attentional selection and motor preparation processes within working memory were investigated in two retrospective cuing tasks. In the first experiment, participants stored the orientation and location of a grating. Subsequent feature cues (selective vs. neutral) indicated which feature would be the target for later report. The oscillatory response in the mu and beta frequency range with an estimated source in the sensorimotor cortex contralateral to the responding hand was used as correlate of motor preparation. Mu/beta suppression was stronger following the selective feature cues compared to the neutral cue, demonstrating that purely feature-based selection is sufficient to form a prospective motor plan. In the second experiment, another retrospective cue was included to study whether knowledge of the task at hand is necessary to initiate motor preparation. Following the feature cue, participants were cued to either compare the stored feature(s) to a probe stimulus (recognition task) or to adjust the memory probe to match the target feature (continuous report task). An analogous suppression of mu oscillations was observed following a selective feature cue, even ahead of task specification. Further, a subsequent selective task cue again elicited a mu/beta suppression, which was stronger after a continuous report task cue. This indicates that working memory is able to flexibly store different types of information in higher-level mental codes to provide optimal prerequisites for all required action possibilities.
Asunto(s)
Atención , Memoria a Corto Plazo , Atención/fisiología , Señales (Psicología) , Humanos , Memoria a Corto Plazo/fisiología , Percepción , Estudios Prospectivos , Estudios Retrospectivos , Percepción Visual/fisiologíaRESUMEN
How can we retrieve action plans in working memory (WM) after being distracted or interrupted? The present EEG study investigated this question using a WM task in which a random sequence of single numbers (1-4 and 6-9) was presented. In a given trial, participants had to decide whether the number presented in the preceding trial was odd or even. Additionally, interfering stimuli were randomly presented in 25% of all trials, requiring the participants to either ignore a colored number (distraction) or respond to it (interruption) while maintaining the previously formed action plan in WM. Our results revealed a detrimental impact of interruptions on WM performance in trials after interrupting stimuli compared to trials without a preceding interference. This was reflected in decreased task accuracy and reduced stimulus- and response-locked P3b amplitudes potentially indicating a hampered reactivation of stimulus-response links. Moreover, decreased contralateral mu suppression prior to a given response highlighted an impaired response preparation following interruptions. Distractions, on the other hand, did not negatively affect task performance but were followed by faster responses in subsequent trials compared to trials without prior interference. This result pattern was supported by stronger contralateral mu suppression indicating a facilitated response preparation. Overall, these results suggest that action representations in WM are resistant to distractions but do suffer from interruptions that disrupt or interfere with their implementation. We thus propose that the possibility of adequately preparing for an upcoming response is essential for behavioral guidance in the presence of external interference.
Asunto(s)
Ondas Encefálicas/fisiología , Potenciales Relacionados con Evento P300/fisiología , Función Ejecutiva/fisiología , Memoria a Corto Plazo/fisiología , Recuerdo Mental/fisiología , Actividad Motora/fisiología , Desempeño Psicomotor/fisiología , Adolescente , Adulto , Femenino , Humanos , Masculino , Adulto JovenRESUMEN
Attention can be allocated toward mental representations in working memory also after the initial encoding of information has been completed. It was shown that focusing on only one item within working memory transfers this representation into a protected state, reducing its susceptibility to interference by incoming signals. The present study investigated the nature of this retroactive cue (retro-cue) benefit by means of oscillatory activity in the EEG. In a working memory task with a retro-cue indicating one, two or three memory representations as relevant and a block-wise distractor display presented after the retro-cue, participants had to remember the orientation of a colored bar. On behavioral level, we found that the interfering effect of the distractor display on memory performance could be prevented when a retro-cue reduced the number of attended representations in working memory. However, only the one-item retro-cue led to an overall increase in task performance compared to a condition without a retro-cue. The neural basis of this special representational status was investigated by means of oscillatory parameters in the EEG and a clustering approach on level of the independent components (ICs) in the signal. The retroactive reduction of attended working memory representations was reflected in a suppression of alpha power over right parietal and parieto-occipital sites. In addition, we found that an IC cluster representing oscillatory activity in the mu/beta range (10-12 Hz and 20-24 Hz) with a source in sensorimotor cortex revealed a power suppression already prior to the memory probe following the one-item retro-cue. This suggests that the retro-cue benefit results in large parts from the possibility to focus attention on one particular item in working memory and initiate motor planning processes already ahead of the probe stimulus indicating the respective response.