Integrating attention, alertness and control in the brain: an electrophysiological approach

Converging evidences from neurophysiological, neuropsychological and functional neuroimaging literature suggested the involvement of a large-scale fronto-parietal network in the volitional and reflexive attentional control, which enables the biological systems to select relevant portions of the input stream for facilitating processing, in order to flexibly guide behavior on the basis of internal or external goals. This system acts in tight interplay with lateralized structures deputed to the achievement and maintenance of an adequate level of arousal, and with medial frontal structures responsible for the on-line modification of action and thought in response to an ever-changing external world. This project aims at clarifying the spatio-temporal dynamics of the recruitment of these three tightly related systems (alertness, orienting and executive control) and at a better explanation of integrative effects previously reported, by means of a series of high-density electrophysiological recording experiments combined with source localization methods. Experiment 1 combined a spatial cueing paradigm with a flanker task, showing early occipital and parietal activations in response to valid cues, and a lateralized pattern of sources for the responses of the phasic alertness system to both spatially valid and spatially neutral cues; additionally, we reported behavioral, electrophysiological and functional indexes of a modulation exerted by the orienting system upon the executive control one. Experiment 2 compared lateralized shifts of attention elicited by centrally and peripherally presented spatially valid and neutral cues, in a combined cueing and go/no-go task. The results again suggested an early involvement of the selective attention system in response to the task-relevant cues, as expressed in occipito-temporal enhanced responses to the valid cues as compared to the neutral ones; additionally, lateralized superior parietal and frontal activations were recorded, concurrently with attentional shifts. Again, a modulation of the conflict monitoring/response inhibition system was observed in case of validly cued stimuli, as indexed by anticipations of the fronto-central NoGoN2 in response to non-targets preceded by valid warning signals. Experiment 3 tested the hypothesis of bidirectional modulations between the attention and control systems, by means of an integrated stop-signal/flanker task. The results showed that the selective response inhibition, required in case of incompatible flankers in the primary stimuli, interfered with the attentional switch towards the relevant stop-signals, as reflected in dimmed auditory responses to the stop-tones. All in all, the present results point toward a complex interplay among the three systems, and suggest that any interpretation of the scientific results obtained in paradigms addressing the attentional networks should account also for alertness and executive control effects, which are indirectly manipulated when capitalizing on cueing/switching paradigms.