Source Analysis of Event-related Cortical Activity during Visuo-spatial Attention

Abstract

Recordings of event-related potentials (ERPs) were combined with structural and functional magnetic resonance imaging (fMRI) to study the spatio-temporal patterns of cortical activity that underlie visual-spatial attention. Small checkerboard stimuli were flashed in random order to the four quadrants of the visual field at a rapid rate while subjects attended to stimuli in one quadrant at a time. Attended stimuli elicited enhanced ERP components in the latency range 80-200 ms that were co-localized with fMRI activations in multiple extrastriate cortical regions. The earliest ERP component (C1 at 50-90 ms) was unaffected by attention and was localized by dipole modeling to calcarine cortex. A longer latency deflection in the 150-225 ms range that was accounted for by this same calcarine source, however, did show consistent modulation with attention. This late attention effect, like the C1, inverted in polarity for upper versus lower field stimuli, consistent with a neural generator in primary visual cortex (area V1). These results provide support to current hypotheses that spatial attention in humans is associated with delayed feedback to area V1 from higher extrastriate areas that may have the function of improving the salience of stimuli at attended locations.

Learning related activation of somatosensory cortex by an auditory stimulus recorded with magnetoencephalography

“…Thus, in contrast to the current paradigm, in previous work participants were focusing only on stimulus presentation. Evoked responses in multiple sensory modalities have been shown to be substantially larger under conditions of direct attention ([Di Russo et al, 2003], [Giabbiconi et al, 2007], [Kida et al, 2004], [Martínez et al, 2006] and [Poghosyan and Ioannides, 2008]), and as mentioned previously, the evoked neural CR is smaller than the response to the US, even under conditions of direct attention (Moses et al, 2005). These observations may account for the lack of an evoked CR found in the current study.…”

Spatial attention facilitates selection of illusory objects: Evidence from event-related brain potentials

“…Attended corner offsets elicited enlarged P1 (80-128 msec) and N1 (160-196 msec) components, which is the typical pattern of ERP enhancement produced by spatial attention (e.g., (Di Russo et al 2003;Hopfinger et al 2004). In addition, there was a smaller augmentation of the N1 elicited by the offsets at the unattended end of the attended bar relative to the offsets occurring on the unattended bar.…”

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

“…In this early time window, ERP components, such as the N1 and P1, have been associated with the ability to inhibit responses to incoming sensory information (Di Russo et al 2003). N1 and P1 effects have primarily been identified in behavioral inhibition paradigms, such as the Stop-signal (Bekker et al 2005), Go/No-go (S. J.…”