The temporal order judgment paradigm: subcortical attentional contributionunder exogenous and endogenous cueing conditions

The role of subcortical attentional processing was investigated under exoge nous and endogenous cueing conditions. As retinotectal projections arise pr edominantly from the nasal retina i.e., temporal hemifield, subcortical att ention should be distributed asymmetrically under monocular viewing conditi ons with a temporal hemifield advantage. We compared the results of monocul ar and binocular viewing conditions using a temporal order judgment (TOJ) p aradigm. Subjects fixated a centrally located cross and two stimuli were pr esented with a variable onset asynchrony. Three experiments were conducted: no cue, exogenous cue and endogenous cue. Subjects reported which stimulus seemed to appear first. An effect consistent with subcortical processing w as found under exogenous cueing conditions. No such effect was found under endogenous cueing conditions. We believe that subcortical attentional proce ssing in response to an exogenous cue facilitates rapid shifts in attention towards environmental stimuli. We found no evidence for subcortical proces sing in voluntary directed attention and believe this process to be cortica l in nature. (C) 1999 Elsevier Science Ltd. All rights reserved.