Attention recruits frontal cortex in human infants

Abstract

Young infants learn about the world by overtly shifting their attention to perceptually salient events. In adults, attention recruits several brain regions spanning the frontal and parietal lobes. However, it is unclear whether these regions are sufficiently mature in infancy to support attention and, more generally, how infant attention is supported by the brain. We used event-related functional magnetic resonance imaging (fMRI) in 24 sessions from 20 awake behaving infants 3 mo to 12 mo old while they performed a child-friendly attentional cuing task. A target was presented to either the left or right of the infant's fixation, and offline gaze coding was used to measure the latency with which they saccaded to the target. To manipulate attention, a brief cue was presented before the target in three conditions: on the same side as the upcoming target (valid), on the other side (invalid), or on both sides (neutral). All infants were faster to look at the target on valid versus invalid trials, with valid faster than neutral and invalid slower than neutral, indicating that the cues effectively captured attention. We then compared the fMRI activity evoked by these trial types. Regions of adult attention networks activated more strongly for invalid than valid trials, particularly frontal regions. Neither behavioral nor neural effects varied by infant age within the first year, suggesting that these regions may function early in development to support the orienting of attention. Together, this furthers our mechanistic understanding of how the infant brain controls the allocation of attention.

Keywords: attentional cuing; early development; fMRI; frontoparietal network; gaze coding.

Fig. 1.

Task design and behavioral evidence of stimulus-driven attention in infants. (A) Trial sequence: Participants were presented with an attention getter until they fixated. A cue was then presented briefly before a target appeared. The cue was either in the same location as the target (valid), in the opposite location (invalid), or cues were presented bilaterally (neutral). (B) Average RT in seconds for each trial type. Error bars indicate SE across sessions. Gray lines connect individual session data across the three trial types. (C) Relationship of different condition comparisons to age in months.

Fig. 2.

Whole-brain statistical map of difference between conditions. Contrasts for each session were aligned to standard space and tested for reliability with a group t test. Three tests were performed: (A) invalid > valid, (B) neutral > valid, and (C) invalid > neutral. An uncorrected threshold is used for visualization (P < 0.05). Coordinates are in adult MNI space.

Fig. 3.

Neural evidence of stimulus-driven attention in infants. (A) Individual ROIs from functional analysis with coordinates in MNI space. Contrasts were extracted from these ROIs, averaged across voxels, and tested for reliability with bootstrap resampling. Three tests were performed: (B) invalid > valid, (C) neutral > valid, and (D) invalid > neutral. Lowercase “r” and “l” indicate left and right hemispheres, respectively. Error bars indicate SE across sessions. * = P < 0.05, ∼ ⁼ P < 0.075.