Endogenous spatial attention directed to intracutaneous electrical stimuli on the forearms involves an external reference frame.

In the present study, we examined whether the direction of attention while anticipating intracutaneous electrical stimuli on the left or right forearm occurs within an internal somatotopic or an external body-based reference frame. Participants placed their hands on a table in front of them in a normal position or in a crossed-hands position. A symbolic cue with a validity of 80% instructed participants to attend to either the left or the right side, which varied from trial to trial. Crossing the hands induces a conflict of internal and external reference frames which allows to determine the dominating reference frame(s). Analyses of the electroencephalogram (EEG) during the orienting phase revealed that crossing the arms did not induce a reversal of neural activity over central sites as a late direction attention-related positivity and increased ipsilateral alpha power over occipital and central sites was observed in both conditions. Hand position influenced the processing of the electrical stimuli as no effect of cue validity was observed on the P3a component in the crossed-hands position. Our results indicate that endogenous spatial attention to intracutaneous electrical stimuli primarily occurs within an external reference frame.

Comparing the effects of sustained and transient spatial attention on the orienting towards and the processing of electrical nociceptive stimuli.

We examined whether sustained vs. transient spatial attention differentially affect the processing of electrical nociceptive stimuli. Cued nociceptive stimuli of a relevant intensity (low or high) on the left or right forearm required a foot pedal press. The cued side varied trial wise in the transient attention condition, while it remained constant during a series of trials in the sustained attention condition. The orienting phase preceding the nociceptive stimuli was examined by focusing on lateralized EEG activity. ERPs were computed to examine the influence of spatial attention on the processing of the nociceptive stimuli. Results for the orienting phase showed increased ipsilateral alpha and beta power above somatosensory areas in both the transient and the sustained attention conditions, which may reflect inhibition of ipsilateral and/or disinhibition of contralateral somatosensory areas. Cued nociceptive stimuli evoked a larger N130 than uncued stimuli, both in the transient and the sustained attention conditions. Support for increased efficiency of spatial attention in the sustained attention condition was obtained for the N180 and the P540 component. We concluded that spatial attention is more efficient in the case of sustained than in the case of transient spatial attention.

The importance of failure: feedback-related negativity predicts motor learning efficiency.

Learning from past mistakes is of prominent importance for successful future behavior. In the present study, we tested whether reinforcement learning signals in the brain are predictive of adequate learning of a sequence of motor actions. We recorded event-related potentials (ERPs) while subjects engaged in a sequence learning task. The results showed that brain responses to feedback (the feedback-related negativity [FRN]) predicted whether subjects learned to avoid an erroneous response the next time this action had to be performed. Our findings add to a growing literature on feedback-based performance adjustment, by showing that FRN amplitudes may reflect the acquisition of motor skill and the consolidation of contingencies between stimuli or cues and their associated responses, providing evidence that learning efficiency and future performance can be predicted by the neural response to current feedback: FRN amplitude associated with a mistake is predictive of whether this mistake will be repeated, or learned from.