ERP and fMRI correlates of endogenous and exogenous focusing of visual‐spatial attention

Abstract

The aim of this study was to investigate the neural correlates of the functional distinction underlying attentional mechanisms of endogenous-sustained and exogenous-transient spatial selection. We recorded event related potentials (ERPs) and used functional magnetic resonance imaging (fMRI) in separate experiments while subjects performed a simple reaction time (RT) to the same visual stimulus displayed to one of several field locations. Endogenous-sustained or exogenous-transient focusing of attention onto target location were obtained by presenting the stimulus in blocks of same-point vs. randomised-point trials, respectively. Same-point stimuli yielded overall faster RT than randomised stimuli, indicating a facilitating effect of endogenous-sustained spatial attention on the perceptual processing of the impending stimulus. Moreover, same-point vs. randomised presentations revealed significant increases in the fMRI signal in the bilateral lingual and fusiform gyri as well as in the right calcarine sulcus, in conjunction with a larger amplitude of the posterior P1 component of ERPs, but no modulation of the amplitude of the N1 component. Rather, a larger amplitude of N1 was found in the reverse contrast, randomised minus same-point trials, which revealed increases in the fMRI signal along the posterior left superior frontal sulcus and bilaterally in the superior precuneus. These findings indicate that N1 indexes exogenous orienting of attention and is likely to represent the activity of frontal and parietal components of the attention network involved in eliciting attention changes. In contrast, the effects of those changes, resulting in a modulation of activation in visual occipital areas, are indexed by P1.

Biasing Perception by Spatial Long-Term Memory

“…Resolving whether the observed N1 modulation is a memory-specific effect will require further investigation. The N1 reflects activation of several visual and possibly multisensory areas (Doherty et al, 2005;Natale et al, 2006), and its modulation can be highly tasksensitive to stimulus parameters and response requirements Luck et al, 1990;Mangun and Hillyard, 1991;Hillyard and Anllo-Vento, 1998).…”

Event-Related Brain Potentials in the Study of Inhibition: Cognitive Control, Source Localization and Age-Related Modulations

“…In summary, the P1 component that is elicited when inhibition processes are triggered may represent the visual processing of the stimulus, whereas the N1 may be related to the orientation of attention via the fronto-parietal attention network (Natale et al 2006).…”

Covert orienting of attention and overt eye movements activate identical brain regions

“…More specifically, it could be that endogenously driven covert shifts of attention lead to higher amounts of neural activation than endogenously driven overt shifts of attention while exogenously driven covert shifts of attention lead to lower amounts of neural activation than exogenously driven overt shifts of attention. While the results of some studies suggest that exogenously and endogenously driven shifts of attention are governed by the same neural mechanisms (Peelen et al, 2004;Rosen et al, 1999), the results of other studies suggest that exogenously and endogenously driven shifts of attention rely on distinct neural mechanisms (Natale et al, 2006;Hopfinger and West, 2006;Mayer et al, 2004;Mort et al, 2003;Corbetta and Shulman, 2002;Briand, 1998). However, it seems that regardless of whether covert or overt shifts of attention are required, endogenously driven shifts of attention are associated with either similar or higher amounts of neural activation compared to exogenously driven shifts of attention (Kincade et al, 2005;Peelen et al, 2004;Mayer et al, 2004;Mort et al, 2003;Rosen et al, 1999), consistent with the general idea that endogenously driven shifts of attention are more effortful than exogenously driven shifts of attention Schneider and Shiffrin, 1984).…”