Cognitive Brain Research 13 (2002) 139–151 www.elsevier.com / locate / bres Research report Early involvement of the temporal area in attentional selection of grating orientation: an ERP study a,b,c, c b * Alice Mado Proverbio , Paola Esposito , Alberto Zani a Department of Psychology, University of Milano-Bicocca, Piazza dell’ Ateneo Nuovo, 1, 20126 Milan, Italy b Institute of Bioimaging and Molecular Physiology in Humans, Consiglio Nazionale delle Ricerche, Via Fratelli Cervi 93, 20090 Segrate, Milan, Italy c Laboratory of Cognitive Electrophysiology, Department of Psychology, University of Trieste, Trieste, Italy Accepted 6 September 2001 Abstract The aim of the present study was to investigate the neural mechanisms of stimulus orientation selection in humans by recording event-related potentials (ERPs) of the brain with a 32-channel montage. Stimuli were isoluminant black-and-white gratings (3 cpd) having an orientation of 508, 708, 908, 1108 and 1308, randomly presented in the foveal portion (28 of visual angle) of the central visual field. The task consisted in selectively attending and responding to one of the five grating orientations, while ignoring the others. ERP results showed that orientation selection affected neural processing starting already at an early post-stimulus latency. The P1 component (80–140 ms) measured at temporal area, which might well be reflecting the activity of the ventral stream (i.e. ‘WHAT’ system) of the visual pathways, showed an enhanced amplitude for target orientations. These effects increased with progressive neural processing over time as reflected by selection negativity (SN) and P300 components. In addition, both reaction times (RTs) and ERPs showed a strong ‘oblique’ effect, very probably reflecting the perceptual predominance of orthogonal versus oblique stimulus orientation in the human visual system: RTs were much faster, and SN and P300 components much larger, to gratings presented vertically than in other orientations.  2002 Elsevier Science B.V. All rights reserved. Theme: Neural basis of behavior Topic: Cognition Keywords: Attention; Electrophysiology; Sensory gating; Vision; VEP; Ventral stream; P1 component 1. Introduction investigate the neurofunctional bases of feature selection, and to determine the stage at which top-down processes Several functional neuroimaging studies have shown such as attention can affect sensory processing. The effect that visual attention selection modulates activity of the of selective attention to spatial frequency and orientation dorsal and ventral streams of the visual system [4,14,35]. on ERPs in humans was first measured in the pioneering This modulation has been also observed by measuring studies of Harter and co-workers [11,12,26]. They found changes in amplitude, latency and scalp topography of that attention enhanced N1 and N2 components of ERPs, event-related potentials (ERPs) to visual stimuli as a giving rise to a broad negative response called selection function of task relevance and attention condition (e.g. negativity which peaked at about 250 ms post-stimulus. Refs. [1,22,38]). Later electrophysiological studies described modulation A large number of ERP studies have attempted to of ERP responses earlier than selection negativity in attention tasks in which targets were alphanumeric stimuli [32], grating spatial frequency or orientation [18,27,38,39] *Corresponding author. Department of Psychology, University of and color [2]. However, relatively few studies provided Milano-Bicocca, Piazza dell’Ateneo Nuovo, 1, 20126 Milano, Italy. Tel.: evidence of an early modulation of surface sensory evoked 139-02-2171-7511. activity recorded at visual areas during selective attention E-mail addresses: mado.proverbi@unimib.it or zani@inb.mi.cnr.it (A.M. Proverbio). to non-spatial features (e.g. Refs. [8,17,30]). These differ- 0926-6410 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0926-6410(01)00103-3