Neither sharpened or lost -- the unique role of attention in children's neural representations

One critical feature of childrens cognition is their relatively immature attention. Decades of research have shown that childrens attentional abilities mature slowly over the course of development, including the ability to filter out distracting information. Despite such rich behavioral literature, little is known about how developing attentional abilities modulate neural representations in children. This information is critical to understanding exactly how attentional development shapes the way children process information. One intriguing possibility is that attention might be less likely to impact neural representations in children as compared with adults. In particular, representations of attended items may be less likely to be sharpened relative to unattended items in children as compared to adults. To investigate this possibility, we measured brain activity using fMRI while adults (21-31 years) and children (7-9 years) performed a one-back working memory task in which they were directed to attend to either motion direction or an object in a complex display where both were present. We used multivoxel pattern analysis and compared decoding accuracy of attended and unattended information. Consistent with attentional sharpening, we found higher decoding accuracy for task-relevant information (i.e., objects in the object-attended condition) than for task-irrelevant information (i.e., motion in the object-attended condition) in adults visual cortices. However, in childrens visual cortices, both task-relevant and task-irrelevant information were decoded equally well. Whats more, exploratory whole-brain analysis showed that the children represent task-irrelevant information more than adults in multiple regions across the brain, including the prefrontal cortex. These findings show that 1) attention does not sharpen neural representations in the child visual cortex, and further 2) that the developing brain can represent more information than the adult brain.