Switching Attention without Shifting the Spotlight: Object-Based Attentional Modulation of Brain Potentials

Abstract

Although psychophysical evidence for object-based attention has been reported, corresponding studies with event-related potentials (ERPs) are scarce. Here subjects were presented with perceptual fields containing two superimposed objects (transparent surfaces generated by two sets of dots in rigid rotation around fixation, each set of a different color and direction of motion) or only one object (the same dots but either at rest or all rotating in the same direction). Brief (150-msec) rectilinear displacements affected either of the sets at random ISIs of 350 to 550 msec. Attention was directed to one set of dots, guided by color, in order to discriminate the direction of their displacement. Motion-onset ERPs elicited by these displacements were compared for attended and unattended dots. When the perceptual field consisted of two objects, strong suppression of P1 and N1 was obtained in the ERPs associated with the unattended object. No suppression was found with the field containing a single object, although an enhanced selection negativity was found in ERPs associated with attended dots (selected by color). Since the two objects occupied the same region of visual space, the suppression of P1/N1 cannot be explained by the space-based mechanisms but is consistent with object-based attentional selection at early stages of vision. The results highlight the role of perceptual organizations in enabling alternative attentional mechanisms.

Selective visual-spatial attention alters induced gamma band responses in the human EEG

“…Previous studies which investigated the motion VEP reported an increase in amplitude at electrode sites P3/4 and O1/2 of the international 10±20 system when the moving stimulus was attended and related this augmentation to activity in the dorsal stream Valdes-Sosa et al, 1998). Human fMRI studies showed an increase of metabolic activity related to the processing of moving stimuli in a cortical region which underlies approximately that area measured by P3/4 and O1/2 (Tootell et al, , 1996Sereno et al, 1995).…”

“…(3) Is the attentional enhancement of spectral power related to the processing of motion, i.e. resulting from an ampli®cation of neural synchronized activity in the dorsal pathway as suggested by studies using motion evoked VEPs (AnlloVento and Hillyard, 1996;Valdes-Sosa et al, 1998)? A 128-channels EEG montage was used in order to reveal high-density spatial information.…”

“…Probst et al, 1993;Anllo-Vento and Hillyard, 1996;Patzwahl et al, 1996;Buchner et al, 1997;Valdes-Sosa et al, 1998). On the basis of these results, we calculated two regional means for electrodes 71, 66 and 60 for the left and 84, 85 and 86 for the right hemisphere (see Fig.…”

Attention Modulates Initial Stages of Visual Word Processing

“…Attention to a spatial location enhances target processing as early as 80 msec after stimulus onset, as shown by a modulation of the P1 event-related potential (ERP) component. Attentional selection of objects or features also takes place early in time, starting around 100-150 msec (Schoenfeld et al, 2007;Valdes-Sosa, Bobes, Rodriguez, & Pinilla, 1998). Attention also modulates other, later stages, as indexed by the P300 or the N400 (Vogel, Woodman, & Luck, 2005).…”

Functionally independent components of early event-related potentials in a visual spatial attention task

“…However, neither the auditory nor the visual N1 responses are unitary (Naatanen & Picton 1987). In particular, visual N1 peak amplitude and latency are a¡ected by both stimulus and task variables, including response cueing and attention to location or movement (Mangun & Hillyard 1991;O'Donnell et al 1997;Kotchoubey et al 1997;Valdes-Sosa et al 1998). …”