Retinotopic organization of early visual spatial attention effects as revealed by PET and ERPs

Abstract

Cerebral blood flow PET scans and high-density event-related potentials (ERPs) were recorded (separate sessions) while subjects viewed rapidly-presented, lower-visual-field, bilateral stimuli. Active attention to a designated side of the stimuli (relative to passive-viewing conditions) resulted in an enhanced ERP positivity (P1 effect) from 80-150 msec over occipital scalp areas contralateral to the direction of attention. In PET scans, active attention vs. passive showed strong activation in the contralateral dorsal occipital cortex, thus following the retinotopic organization of the early extrastriate visual sensory areas, with some weaker activation in the contralateral fusiform. Dipole modeling seeded by the dorsal occipital PET foci yielded an excellent fit for the P1 attention effect. In contrast, dipoles constrained to the fusiform foci fit the P1 effect poorly, and, when the location constraints were released, moved upward to the dorsal occipital locations during iterative dipole fitting. These results argue that the early ERP P1 attention effects for lower-visual-field stimuli arise mainly from these dorsal occipital areas and thus also follow the retinotopic organization of the visual sensory input pathways. These combined PET/ERP data therefore provide strong evidence that sustained visual spatial attention results in a preset, top-down biasing of the early sensory input channels in a retinotopically organized way.

The Study of Spatial Selective Attention Effects by Event-Related Potentials

“…Maybe it is caused by performing the block 1 first. We can also infer from Table 3 and Table 4 that there was no great difference between attendleft and attend-right conditions, consistent with the previous findings [4,5,8,10,11]. Figure 3.…”

“…The previous studies had shown effects of lateralized spatial attention on the P1 amplitude [2,3,4,5,6,7]. ERPs recorded in these experiments provide critical information about the time course of stimulus-selection processes in these cortical areas.…”

“…Hemodynamically-based brain structural imaging methods (fMRI: functional magnetic resonance imaging; PET: positron emission tomography) have identified the specific areas activated in visuospatial attention with its high spatial resolution, which enable the localization of the level along the visual pathway where attention effect first took place [4]. Now most studies have pointed that activities in extrastriate visual cortical areas were modulated by spatial attention [4,5,6,7]. However fMRI and PET data could not provide any timing information about the processing in the brain because of their order of hundreds of milliseconds on the time resolution [5,6].…”

“…Now most studies have pointed that activities in extrastriate visual cortical areas were modulated by spatial attention [4,5,6,7]. However fMRI and PET data could not provide any timing information about the processing in the brain because of their order of hundreds of milliseconds on the time resolution [5,6]. On the contrast, the non-invasive scalp-recorded ERP timelocked to the standard stimuli with high temporal resolution (order of milliseconds) made it possible to acquire the time course of the visual processing reflected by brain neuronal activity, namely when direction of attention originally resulted in deflection along the pathway and the timing differences between two different sites, for example, the frontal and occipital activities [8,9].…”

Spatio-temporal dynamics of attentional selection stages during multiple object tracking

“…Importantly, in none of these studies the illusory figure was created from moving edges and the global form was changing every presented frame. Another important difference is that in our study the targets defining the global shape were continuously present on the display and we employed the probing technique to elicit the event-related potentials (Heinze et al, 1994;Mangun, 1995;Woldorff et al, 1997). In such cases, in contrast to sudden-onset conditions, when illusory figures are formed from cues that are already present on the display, the elicited ERPs have smaller N1 amplitudes .…”