Increased parietal activity after training of interference control.

Recent studies suggest that computerized cognitive training leads to improved performance in related but untrained tasks (i.e. transfer effects). However, most study designs prevent disentangling which of the task components are necessary for transfer. In the current study, we examined whether training on two variants of the adaptive dual n-back task would affect untrained task performance and the corresponding electrophysiological event-related potentials (ERPs). Forty three healthy young adults were trained for three weeks with a high or low interference training variant of the dual n-back task, or they were assigned to a passive control group. While n-back training with high interference led to partial improvements in the Attention Network Test (ANT), we did not find transfer to measures of working memory and fluid intelligence. ERP analysis in the n-back task and the ANT indicated overlapping processes in the P3 time range. Moreover, in the ANT, we detected increased parietal activity for the interference training group alone. In contrast, we did not find electrophysiological differences between the low interference training and the control group. These findings suggest that training on an interference control task leads to higher electrophysiological activity in the parietal cortex, which may be related to improvements in processing speed, attentional control, or both.

Sustained and transient attentional processes modulate neural predictors of memory encoding in consecutive time periods.

Memory formation is commonly thought to rely on brain activity following an event. Yet, recent research has shown that even brain activity previous to an event can predict later recollection (subsequent memory effect, SME). In order to investigate the attentional sources of the SME, event-related potentials (ERPs) elicited by task cues preceding target words were recorded in a switched task paradigm that was followed by a surprise recognition test. Stay trials, that is, those with the same task as the previous trial, were contrasted with switch trials, which included a task switch compared to the previous trial. The underlying assumption was that sustained attention would be dominant in stay trials and that transient attentional reconfiguration processes would be dominant in switch trials. To determine the SME, local and global statistics of scalp electric fields were used to identify differences between subsequently remembered and forgotten items. Results showed that the SME in stay trials occurred in a time window from 2 to 1 sec before target onset, whereas the SME in switch trials occurred subsequently, in a time window from 1 to 0 sec before target onset. Both SMEs showed a frontal negativity resembling the topography of previously reported effects, which suggests that sustained and transient attentional processes contribute to the prestimulus SME in consecutive time periods.

Different brain activities predict retrieval success during emotional and semantic encoding.

There is an increasing line of evidence supporting the idea that the formation of lasting memories involves neural activity preceding stimulus presentation. Following this line, we presented words in an incidental learning setting and manipulated the prestimulus state by asking the participants to perform either an emotional (neutral or emotional) or a semantic (animate or inanimate) decision task. Later, we tested the retrieval of each previously presented word with a recognition memory test. For both conditions, the subsequent memory effect (SME) was defined as ERP difference between subsequently remembered and forgotten words. Comparing the prestimulus SME between and within the two conditions yielded topographic differences in the time interval from -1300 to -700 msec before stimulus onset. This indicates that the activity of brain areas involved in incidental encoding of semantic information varied in the spatial distribution of ERPs, depending on the emotional and semantic requirements of the task. These findings provide evidence that there is a difference in semantic and emotional preparatory processes, which modulates successful encoding into episodic memory. This difference suggests that there are multiple task-specific functional neural systems that support memory formation. These systems differ in location and/or relative contribution of some of the brain structures that generate the measured scalp electric fields. Consequently, the cognitive processes that enable memory formation depend on the differential semantic nature of the study task and reflect differences in the preparatory processing of the multiple semantic components of a word's meaning.

Head-centred meridian effect on auditory spatial attention orienting.

Six experiments examined the issue of whether one single system or separate systems underlie visual and auditory orienting of spatial attention. When auditory targets were used, reaction times were slower on trials in which cued and target locations were at opposite sides of the vertical head-centred meridian than on trials in which cued and target locations were at opposite sides of the vertical visual meridian or were not separated by any meridian. The head-centred meridian effect for auditory stimuli was apparent when targets were cued by either visual (Experiments 2, 3, and 6) or auditory cues (Experiment 5). Also, the head-centred meridian effect was found when targets were delivered either through headphones (Experiments 2, 3, and 5) or external loud-speakers (Experiment 6). Conversely, participants showed a visual meridian effect when they were required to respond to visual targets (Experiment 4). These results strongly suggest that auditory and visual spatial attention systems are indeed separate, as far as endogenous orienting is concerned.