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Objectives: The present study investigated the influence of the cerebral maturity in the process of cue task-specific preparatory activation induced by an spatial cue using a central cue Posner paradigm. For these purposes, the behavioral responses and the Contingent Negative Variation (CNV) generated between the S1 (the warning stimulus) and the S2 (the imperative stimulus) were compared in 16 healthy children (8-13 years old) and 17 healthy young adults (18-23 years old). Methods:The EEG was recorded from 20 scalp sites of the International 10-20 system. The complete trial period included a central directional cue that was on for 300 ms and an attentive waiting period lasting 1360 ms. Finally, a peripheral target subtending a visual angle of 4.56º and situated 2.28º eccentrically in the horizontal meridian appeared. The early and late components of the CNV appearing in the period between the cue and the target were analyzed. Results:The CNV of children did not show contralateral cortical activation related to motor preparation. However, the young adults showed contralateral to the cue activation in motor areas.The children and young adults showed cortical activation in the posterior sensory areas, displaying a contralateral to the cue pattern of activation. In addition to this, a parietal positive component appeared in children during the CNV period. Conclusions:These results might reflect a higher immaturity of the motor preparation system compared with the sensory preparatory system in children. It is possible that children used different strategies than young adults to prepare for stimuli and responses.

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Abstract:In a spatial central cue Posner´s paradigm, positions in the vertical meridian were cued in order to evaluate the neuro-cognitive consequences in the processing of validly cued (VC) and invalidly cued (IC) targets. Sixty-four EEG channels were recorded and analyzed showing that IC targets produced an enhanced P3 component with respect to VC targets. With the purpose of reinforcing the idea of increased activation during IC targets and to define the areas in which the increased activation would occur, source localization was applied to the ERPs. LORETA and single dipole localization showed that the early P3 presented a localization in the dorsal part of the anterior cingulate cortex (dACC), while the late P3 was fitted by single dipole more posterior than the early P3, and LORETA added a source in the parahippocampal gyrus in addition to the already activated dACC. LORETA results also showed a differential activation of the inferior frontal gyrus when IC targets were processed. The previous results suggest that subjects prepare to accomplish the task upon specification of the cue. Therefore, when the IC target appears, it induces the activation of the frontal cortex including areas related to the conflict monitoring system and to the processing of unexpected events. The IC targets also induce the revision of internal models about the task, possibly by activation of the temporo-mesial surface. All the obtained current source differences indicate that a higher brain activation during IC trials with respect to VC trials occurs.

We examined evoked and induced modulations in theta, alpha and gamma oscillations, and also the P2 and late positive component of event-related potentials, during a visual discrimination task with target and nontarget letters. Results for target letters showed a decrease in the amplitude of alpha-band (10-11 Hz) activity and an increase in theta (4-7 Hz) and gamma (40-44 Hz) activities around 350 ms after stimulation. P2 and late positive component presented a higher amplitude to target than to repeated nontarget letters. Alpha reduction was inversely related to theta and late positive component increase. Moreover, gamma oscillation amplitude was directly related to theta amplitude. The findings suggest the importance of occipitoparietal alpha reduction for the development of task-related neuronal activity.