Brain charts for the human lifespan.

Over the past few decades, neuroimaging has become a ubiquitous tool in basic research and clinical studies of the human brain. However, no reference standards currently exist to quantify individual differences in neuroimaging metrics over time, in contrast to growth charts for anthropometric traits such as height and weight1. Here we assemble an interactive open resource to benchmark brain morphology derived from any current or future sample of MRI data ( http://www.brainchart.io/ ). With the goal of basing these reference charts on the largest and most inclusive dataset available, acknowledging limitations due to known biases of MRI studies relative to the diversity of the global population, we aggregated 123,984 MRI scans, across more than 100 primary studies, from 101,457 human participants between 115 days post-conception to 100 years of age. MRI metrics were quantified by centile scores, relative to non-linear trajectories2 of brain structural changes, and rates of change, over the lifespan. Brain charts identified previously unreported neurodevelopmental milestones3, showed high stability of individuals across longitudinal assessments, and demonstrated robustness to technical and methodological differences between primary studies. Centile scores showed increased heritability compared with non-centiled MRI phenotypes, and provided a standardized measure of atypical brain structure that revealed patterns of neuroanatomical variation across neurological and psychiatric disorders. In summary, brain charts are an essential step towards robust quantification of individual variation benchmarked to normative trajectories in multiple, commonly used neuroimaging phenotypes.

Whole-brain white matter organization, intelligence, and educational attainment.

General cognitive ability, sometimes referred to as intelligence, is associated with educational attainment throughout childhood. Most studies that have explored the neural correlates of intelligence in childhood focus on individual brain regions. This analytical approach is designed to identify restricted sets of voxels that overlap across participants. By contrast, we explored the relationship between white matter connectome organization, intelligence, and education. In both a sample of typically-developing children (N = 63) and a sample of struggling learners (N = 139), the white matter connectome efficiency was strongly associated with intelligence and educational attainment. Further, intelligence partially mediated the relationship between connectome efficiency and educational attainment. In contrast, a canonical voxel-wise analysis failed to identify any significant relationships. The results emphasize the importance of distributed brain network properties for cognitive or educational ability in childhood. Our findings are interpreted in the context of a developmental theory, which emphasizes the interaction between different subsystems over developmental time.

Modulation of alpha power at encoding and retrieval tracks the precision of visual short-term memory.

Our ability to hold information in mind is strictly limited. We sought to understand the relationship between oscillatory brain activity and the allocation of resources within visual short-term memory (VSTM). Participants attempted to remember target arrows embedded among distracters and used a continuous method of responding to report their memory for a cued target item. Trial-to-trial variability in the absolute circular accuracy with which participants could report the target was predicted by event-related alpha synchronization during initial processing of the memoranda and by alpha desynchronization during the retrieval of those items from VSTM. Using a model-based approach, we were also able to explore further which parameters of VSTM-guided behavior were most influenced by alpha band changes. Alpha synchronization during item processing enhanced the precision with which an item could be retained without affecting the likelihood of an item being represented per se (as indexed by the guessing rate). Importantly, our data outline a neural mechanism that mirrors the precision with which items are retained; the greater the alpha power enhancement during encoding, the greater the precision with which that item can be retained.

The strength of attentional biases reduces as visual short-term memory load increases.

Despite our visual system receiving irrelevant input that competes with task-relevant signals, we are able to pursue our perceptual goals. Attention enhances our visual processing by biasing the processing of the input that is relevant to the task at hand. The top-down signals enabling these biases are therefore important for regulating lower level sensory mechanisms. In three experiments, we examined whether we apply similar biases to successfully maintain information in visual short-term memory (VSTM). We presented participants with targets alongside distracters and we graded their perceptual similarity to vary the extent to which they competed. Experiments 1 and 2 showed that the more items held in VSTM before the onset of the distracters, the more perceptually distinct the distracters needed to be for participants to retain the target accurately. Experiment 3 extended these behavioral findings by demonstrating that the perceptual similarity between target and distracters exerted a significantly greater effect on occipital alpha amplitudes, depending on the number of items already held in VSTM. The trade-off between VSTM load and target-distracter competition suggests that VSTM and perceptual competition share a partially overlapping mechanism, namely top-down inputs into sensory areas.

The role of spatial information in advance task-set control: an event-related potential study.

Task-switching has proved to be a fruitful paradigm for studying cognitive control mechanisms. Interestingly, this avenue of study has revealed that subjects are, to some degree, able to bring about a change in task-set prior to the performance of that task (provided that they are given advance warning of the upcoming task, for instance in the form of a cue). Event-related potentials (ERPs) have proved to be a good way of measuring these rapid anticipatory control processes. To explore these processes further, the current study examined the relationship between the availability of spatial information and cue-locked task-switching ERP effects. Two groups of subjects were compared: one group could separate the task-sets on the basis of the targets' colour (the 'colour' group), the second on the basis of the targets' location (the 'spatial' group). The performance of both groups benefited to the same extent from advance cueing of task-transitions (switches or repeats), yet the ERP data revealed cue-locked (but not target-locked) differences between the two groups. The most striking of these differences was the absence of both a late positivity over posterior scalp and a late negativity over frontal scalp when the spatial group switched between tasks. Thus, it seems unlikely that these effects index stimulus-response 'reconfiguration'per se--as the mappings were identical for both groups of subjects--but rather that these task-switching processes are sensitive to how the mappings are represented.

Dissociating neural indices of dynamic cognitive control in advance task-set preparation: an ERP study of task switching.

Switching between different tasks is associated with performance deficits, or 'switch costs', relative to repeating the same task. Recent evidence suggests that response rather than task selection processes may be a major cause of switch costs [Schuch, S., Koch, I., 2003. The role of response selection for inhibition of task sets in task shifting. J Exp Psychol Hum Percept Perform, 29 (1) 92-105]. Thus, switch costs are not incurred if on the preceding trial a task has been prepared for but no response required (a 'no-go' trial). We investigated the relationship between response selection and the subsequent preparation of an alternative task set. While switch costs were absent following 'no-go' trials, ERP differences during the precueing interval showed that response selection has implications for subsequent task preparation as well as for task performance per se. The results are discussed in relation to the dissociation of intention versus action in behavioural control and the role of inhibition in switching between task sets.