Magnocellular and parvocellular influences on reflexive attention

Abstract

Previous studies have provided conflicting evidence regarding whether the magnocellular (M) or parvocellular (P) visual pathway is primarily responsible for triggering involuntary orienting. Here, we used event-related potentials (ERPs) to provide new evidence that both the M and P pathways can trigger attentional capture and bias visual processing at multiple levels. Specifically, cued-location targets elicited enhanced activity, relative to uncued-location targets, at both early sensory processing levels (indexed by the P1 component) and later higher-order processing stages (as indexed by the P300 component). Furthermore, the present results show these effects of attentional capture were not contingent on the feature congruency between the cue and expected target, providing evidence that this biasing of visual processing was not dependant on top-down expectations or within-pathway priming.

Figure 1

Trial sequence used in Experiments 1 and 2. The “P” cue (intended to produce strong activity in the parvocellular visual pathway) was a high spatial frequency grating that was isoluminant with the background. The “M” cue (intended to produce strong activity in the magnocellular pathway) was a low spatial frequency, low contrast, motion stimulus. Experiment 1 used a P-pathway target, whereas Experiment 2 used an M-pathway target. Both experiments used “P” and “M” cues. The trials depicted here are cued-location target trials (i.e., the cue and target appeared in the same spatial location). The arrows next to the “M” cue and “M” target are for illustrative purposes only and indicate the stimulus moved either up/down for the cue or right/left for the target. They were not seen during the experiment.

Figure 2

Experiment 1 (“P” Targets). A. ERPs showing the P1 component over lateral occipital electrodes in congruent and incongruent trials over short and long SOAs (top and bottom illustrations). These data are collapsed over contralateral scalp sites (i.e. left hemisphere data for right visual field targets were combined with right hemisphere data for left visual field targets). Topographic voltage maps from cued-uncued difference waves at the short SOA represent the distribution of neural activity highlighting the P1 attention effect (middle illustration). The right side of the topographic voltage maps represents neural activity contralateral to visual stimulation while the left side represents ipsilateral activity. B. ERPs showing the P300 component in congruent and incongruent trials over short and long SOAs.

Figure 3

Experiment 2 (“M” Targets). A. ERPs showing the P1 component over lateral occipital electrodes in congruent and incongruent trials over short and long SOAs (top and bottom illustrations). Topographic voltage maps from cued-uncued difference waves at the short SOA represent the distribution of neural activity highlighting the P1 attention effect (middle illustration). B. ERPs showing the P300 component in congruent and incongruent trials over short and long SOAs.