e. nucleus raphe magnus, nucleus raphe dorsalis and locus coeruleus).

This possibility is supported by the observation that omnidirectional pause neurons (OPNs), which may modulate arousal in orienting subsystems such as the saccade generator (Optican, 2008), stop discharging during sleep (Henn et al., 1984). Further, OPN inactivation produces slower saccades (Kaneko, 1973). Consistent with this idea, increased TOT led to increased subjective Palbociclib perception of sleepiness (SSS) in the current study (Table 2). Increased air traffic density is one of the top five factors leading to poor ATC operator performance (Durso & Manning, 2008). Here we manipulated air traffic density to induce different levels of TC. Subjective and behavioral results confirmed our manipulations: higher traffic density (i.e. higher TC) led to slower RTs, more detection errors and higher levels of perceived exertion (Table 3). The above notwithstanding, increased TC did not impact (micro)saccadic or drift

dynamics our current experiment. Previous studies have found that increased TC affects saccadic dynamics (Galley & Andres, 1996; Di Stasi et al., 2010a,b, 2011) and microsaccadic rates (Pastukhov & Braun, 2010; Benedetto et al., 2011), albeit with inconsistent results. The difference between current and former

MDV3100 clinical trial results may be due partly to the presence of one or more secondary tasks (simultaneous to the participants’ primary task) in many of the previous experiments (Di Stasi et al., 2010a,b; Benedetto et al., 2011). Whatever the reason for the lack of effects of TC in our study, it is worth noting that it applied to both saccades and microsaccades, thereby lending additional support to the hypothesis that saccades and microsaccades share a common generator (Zuber et al., 1965; Otero-Millan et al., 2008, 2011; Rolfs et al., 2008; Engbert, 2012). To our knowledge, no previous research has investigated the effect of TC on drift. In our experiment, variations in TOT but not TC modulated PtdIns(3,4)P2 fixational and saccadic eye movement parameters. The dissociation of TOT and TC effects is important, as it satisfies several neuroergonomics criteria to establish an ideal measure of attentional state in applied settings (Parasuraman & Rizzo, 2007). Briefly, the main requirements of such an attentional measure (in our case, eye-movement based) are (Luximon & Goonetilleke, 2001): (i) sensitivity: it should detect significant variations in attentional levels; (ii) noninvasiveness: it should not interfere with the primary task; and (iii) selectivity: it should be immune to other variables.