Effects of cerebellar transcranial direct current stimulation on attentional processing of the stimulus: Evidence from an event-related potentials study.

Attentional processing consists of a set of processes that manage the flow of information through the nervous system and appropriately allocate attentional resources to relevant stimuli. Specific networks in the frontal and parietal regions appear to be involved in attention. The cerebellum has been identified as a subcortical structure that interacts with cortical brain areas, thereby controlling attentional processes. The aim of this study was to investigate the role of the cerebellum in attentional processing of the stimulus using a P300 Novelty task. We studied the effects of transcranial Direct Current Stimulation (tDCS) delivered over the left cerebellar hemisphere in cathodal, anodal and sham sessions on the P300 components in healthy subjects. Only cathodal cerebellar tDCS significantly reduced the amplitude of the N1, N2 and P3 components for both the target and novel stimuli. Moreover, N1 latency for all the stimuli was shorter after the cathodal tDCS session than after the sham or anodal sessions. These results point to a role of the cerebellum in attentional processing of the stimulus. The cerebellum may act indirectly by regulating and managing the activation and inhibition levels of the cortical areas involved in attentional networks.

The Role of the Right Dorsolateral Prefrontal Cortex in Phasic Alertness: Evidence from a Contingent Negative Variation and Repetitive Transcranial Magnetic Stimulation Study.

Phasic alertness represents the ability to increase response readiness to a target following an external warning stimulus. Specific networks in the frontal and parietal regions appear to be involved in the alert state. In this study, we examined the role of the right dorsolateral prefrontal cortex (DLPFC) during the attentional processing of a stimulus using a cued double-choice reaction time task. The evaluation of these processes was conducted by means of Event-Related Potentials (ERPs), in particular by using the Contingent Negative Variation (CNV), and repetitive 1-Hz Transcranial Magnetic Stimulation (rTMS). Transient virtual inhibition of the right DLPFC induced by real 1-Hz rTMS stimulation led to a significant decrease in total CNV and W1-CNV areas if compared with the basal and post-sham rTMS conditions. Reaction times (RTs) did not decrease after inhibitory rTMS, but they did improve after sham stimulation. These results suggest that the right DLPFC plays a crucial role in the genesis and maintenance of the alerting state and learning processes.

Phasic alertness in a cued double-choice reaction time task: a Contingent Negative Variation (CNV) study.

A phasic change in alertness is produced every time that a warning stimulus precedes a target, and it enhances and maintains the response readiness to an impending stimulus. In the present study, we investigated the Contingent Negative Variation (CNV) phenomenon, as index of phasic alertness, during a S1-S2 paradigm in which the imperative stimulus was represented by a double-choice reaction time task, designed to increase the executive requests at S2. Subjects performed the task at three consecutive time points in order to explore the CNV activity over time. The repetition of a cued double-choice reaction time task reduced the reaction times (RTs), while CNV amplitude remained steady along the sessions. Our data suggest that the continuous recruitment of attentional resources does not undergo habituation when it is related to the brain activity required in the maintenance of working memory when the mental model of the stimulus environment is updated.