Dr. John E. Richards - Conference Presentations

Richards, J.E. (2008). Infant sustained attention affects brain areas controlling covert orienting. International Conference on Infant Studies, Vancouver. (PDF)

  Infants covertly move attention around in space without moving fixation. This is shown in the “spatial cueing” procedure in which a cue indicates the side of an upcoming target or is contralateral to the target (“valid” and “invalid”). Infants localize the target more quickly on valid trials than on invalid trials (“facilitation”), though at certain stimulus-onset-asychrony durations target localization may be delayed (“inhibition of return”). Several prior studies of infant participants with scalp-recorded event-related-potentials (ERP) find an enhancement of the first positive component (P1 component?) to target onset for the validly cued trials (P1 validity effect) and the cortical source for this component is the contralateral extrastriate occipital cortex and fusiform gyrus. The current study used heart-rate-defined attention phases to examine this effect under conditions of attention and inattention.

 The infants in this study were 14 or 20 weeks of age.  A continuous spatial cueing procedure was used in which a stimulus was presented until the infant fixated it, a cue was presented in the periphery for 300 ms, and then a “target” was presented on the same side as the cue (“valid”), on the opposite side of the cue (“invalid”), or a target was presented without a prior cue (“neutral”). Heart rate was recorded continuously and heart rate slowing and the return of heart rate to a prestimulus level were used to define periods of attentiveness and inattentiveness. The EEG was recorded using 124 scalp channels and two eye movement channels. ERP averages were computed around the time of the target onset and immediately preceding the saccade towards the target. Cortical source analysis was used to identify the location and activation of the places in the cortex responsible for generating the P1 validity effect.

 Traditional ERP analyses showed a “validity effect” in which there was an enhanced P1 on valid trials over invalid and neutral trials. This P1 component was enhanced if the infant was attentive, and primarily on short SOA trials. Cortical source analysis was used to identify the cortical areas involved in this ERP effect. Two cortical sources could be identified that accounted for ERP activity occurring about 100 to 130 ms following target onset. The current sources were located in the extrastriate occipital cortex (BA 18, 19) and fusiform gyrus contralateral to the cue. This area was activated most highly for validly cued targets relative to either neutral trials (no cue) or invalidly cued targets (contralateral cue). The activity in these cortical locations was larger when the infant was attentive than when inattentive, and the activity level in these areas during attention was negatively correlated with reaction time (high amplitude cortical activation, short reaction time, facilitation of responding). These results suggest that the “P1 validity effect” in infants is due to short-latency enhancement of the secondary visual areas (“covert orienting”) rather than to feedback from higher cortical areas (“covert attention”).