Mechanisms of Visuospatial Attention: Evidence from Event-related Brain Potentials

Abstract

A series of experiments are reviewed that studied mechanisms underlying visuospatial attention by measuring the influence of attentional selectivity on event-related brain potentials (ERPs). The results are interpreted within a theoretical framework developed by LaBerge (1995)and LaBerge and Brown (1989). Spatial attention can have an effect on occipital P1 and N1 components in trial-by-trial cueing situations, which indicate a spatially selective modulation of processing in the VI-IT pathway. However, this effect is strongly attenuated when unattended locations are potentially relevant, suggesting that early attentional modulations within the ventral stream are optional rather than obligatory. A distinct parietal negativity (Nd1) that is elicited in cued attention tasks is assumed to reflect the existence of a transient location expectation gradient within the posterior parietal cortex (PPC). This effect is not present in sustained attention situations. The factthatthis effectis also observed with auditory stimuli suggests that this spatially selective PPC activity is modality-unspecific. Attentional selectivity in multi-stimulus arrays is reflected by the N2pc component, which may indicate location-specific processing modulations in the ventral pathway that are contingent upon an initial feature analysis.