Spatiotemporal dynamics of visuospatial orienting, reorienting and updating processes: a behavioral and functional investigation

In the last twenty years, considerable research has been encouraged by the concept of two distinct attention networks in the human brain for the voluntary deployment of attention and the reorientation to unexpected events, respectively. Despite the general agreement about the main crucial nodes constituting the two networks (i.e., a dorsal network for goal-directed allocation of attention, DAN, and a ventral network for reorienting attention, VAN), some aspects are still waiting for clarification, mainly regarding each region’s specific contribution and the interplay between the two networks for flexible attentional control. With this work, therefore, we tried to elucidate these still unresolved issues by exploiting novel and avant-garde behavioral and functional approaches. In the first study, Event-Related Optical Signal (EROS) data were collected from participants performing a detection task of a Posner-like paradigm with the aim of characterizing the spatiotemporal dynamics of attentional processes and examining the predictive interactions between and within the two attention systems. Functional analyses, which were complemented by Granger Causality Analysis, revealed a recursive predictive interplay between definite dorsal parietal regions and visual areas subserving both attentional orienting and reorienting. Furthermore, a specific contribution of the left ventral network was found in allocating attention after the occurrence of a central predictive cue. In contrast, the right ventral network activity could reflect post-perceptual updating of the internal task-related expectations. This result is specifically derived from the investigation of the right temporoparietal junction (rTPJ), which stands for one of the most essential hubs of the VAN. Accordingly, the second study was conducted in order to better understand the implication of the rTPJ in visuospatial attentional processes. More precisely, we applied neuronavigated repetitive transcranial magnetic stimulation (rTMS, three pulses at 20 Hz per trial) over rTPJ while administering a cued discrimination task of a Posner-like paradigm. We were thus enabled to interfere online with rTPJ activity and observe potential behavioral effects related either to the reorienting process or to the mechanism of updating internal predictions about cue-target associations on a trial-by-trial basis. Behavioral analyses corroborated 6 our first study results: rTPJ seems to be involved in the capability of updating internal models contextually linked to task contingencies. Consequently, the last study of this work concerns the investigation of the behavioral implementation of the updating mechanism. More precisely, behavioral data were collected from the saccadic version of both a Posner paradigm and a Location distribution paradigm in order to validate these task variants in unveiling behavioral signatures of updating mechanisms of the corresponding internal models (i.e., the trialwise cue predictability and the underlying spatial distribution of target locations, respectively). Secondly, we aimed to discover possible associations between the two updating mechanisms. However, although our findings confirmed the adequacy of our saccadic task versions, we did not find any correlational pattern between performances. Taken together, the current findings shed light on the still debating aspects concerning visuospatial attentional orienting and reorienting and updating processes.