Increased attentive use leads to more idiosyncratic functional connections.

Experience is thought to modify neural connections to adapt the network to be more optimal for the environment. Given the brain's complexity, multiple network changes could each move the system toward optimality. Standard methods ignore this multiplicity and examine each connection independently; these studies have often shown considerable inter-individual variability and modest effects (1). Here, we take a different strategy, determining how a whole-brain connection pattern differs from the typical pattern, that is, how 'idiosyncratic' the pattern is. We examined how the idiosyncrasy of whole brain connection patterns varies with frequency of the use of that part of cortex for attention-demanding tasks, focusing on central versus peripheral vision in healthy individuals (where individuals use central vision more frequently for attention-demanding tasks). We found that the whole-brain pattern of functional connections to the cortical representations of central vision is idiosyncratic, whereas patterns of connections to representations of peripheral vision were very similar person-to-person. In a second set of analyses, we examined the brains of people with central vision loss who use a portion of peripheral vision (called the preferred retinal locus) more frequently for attention-demanding tasks in their daily lives. The cortical representation of the preferred retinal locus exhibits more idiosyncratic connections, compared to a control brain region, or compared to the same brain region in matched control participants with healthy vision. These results are consistent with the hypothesis that increased attentive use of a brain area results in idiosyncratic patterns of whole brain connections. Significance Statement: We found that increased attentive use of a brain region results in more idiosyncratic patterns of connections of that region to the rest of the brain. Our findings support the view that V1 retains the capacity for plasticity well beyond the critical period and that these adaptations are idiosyncratic to the individual's experiences. This approach suggests that tailoring personalized rehabilitation plans for individuals with retinal diseases may be more effective than a 'one size fits all' approach. More generally, it offers a promising framework for investigating brain plasticity in both typical and clinical populations, especially in the context of sensory loss and compensatory adaptation.