Our findings demonstrate that both dorsal and ventral attention networks specify the efficacy of task-irrelevant bottom-up signals for the orienting of covert spatial attention, and indicate a segregation of ongoing/continuous efficacy coding in dorsal regions and transient representations of attention-grabbing events in the ventral

network. The experimental procedure consisted of a preliminary behavioral study (n = 11) and an fMRI study in a different group of volunteers (n = 13). The aim of the preliminary study was to quantify the efficacy of bottom-up signals for visuo-spatial orienting, using overt eye movements during free viewing of the complex and dynamic visual stimuli (Entity and No_Entity videos, see below). The fMRI study was carried out with a

Siemens Allegra 3T scanner. Each participant underwent seven fMRI runs, either with eye BMS-354825 solubility dmso movements allowed (free viewing, overt spatial orienting) or with eye movements disallowed (central fixation, covert spatial orienting; cf. Table S1 in Supplemental Experimental Procedures). Our main fMRI analyses focused on covert orienting, but we also report additional results concerning runs with eye movements allowed (overt orienting in the MR scanner). Both the preliminary experiment and the main fMRI study used the same Microbiology inhibitor visual stimuli. These consisted of two videos depicting indoor and outdoor computer-generated scenarios, and containing many elements typical of real environments

(paths, walls, columns, buildings, stairs, furnishings, boxes, objects, cars, trucks, beds, etc.; see Figure 1A for some examples). The two videos followed the same route through the same complex environments, but one video also included 25 human-like characters (Entity video, Figures 2A and 2B), while the other did not (No_Entity video, Figure 1A). In the Entity video, the characters entered the scene in an unpredictable manner, coming in from various directions, mafosfamide walking through the field of view, and then exiting in other locations, as would typically happen in real environments. Each event/character was unique, unrepeated, and with its own features: they could be either male or female, have different body builds, be dressed in different ways, etc. (see Figure 2A for a few examples). For each frame of the No_Entity video, we extracted the mean saliency and the position of maximum saliency. Saliency maps were computed by using the “SaliencyToolbox 2.2.” (http://www.saliencytoolbox.net/). The mean saliency values were convolved with the statistical parametric mapping (SPM) hemodynamic response function (HRF), resampled at the scanning repetition time (TR = 2.08 s) and mean adjusted to generate the S_mean predictor for subsequent fMRI analyses. The coordinates of maximum saliency were combined with the gaze position data to generate the SA_dist predictor (i.e.