CRCNS: Processing speed in the human connectome across the lifespan

The pathways in the human brain form a large network that supports brain function. The structure of this connectome changes across the life span, and it is well known that white matter pathways develop from childhood to old age. It is, however, less well understood how these changes influence the functional communication across these pathways, which processes information on the timescale of milliseconds. A unique way of studying these temporal properties of functional connectivity in the human brain is through single pulse, electrical stimulation of intracranial electrodes, where pulses spread along cortical networks and the directionality and transmission speed can be studied. However, these intracranial electrodes are placed for clinical purposes in epilepsy treatment, resulting in quite some variation in locations across patients. To enable comprehensive research on specific networks, we need to find a way of consolidating multi-subject intracranial neurophysiological data into a single coordinate space, and combine this in a dedicated and structured database. This collaborative project will organize a large database of existing and newly acquired intracranial electroencephalography (iEEG) data with single pulse electrical brain stimulation. Through a community effort, a standard structure for iEEG data is being developed: the iEEG extension to the Brain Imaging Data Structure (iEEG-BIDS). Neuroimaging data will be stored in the BIDS structure alongside iEEG data to map the anatomical location of every electrode, such that subjects with electrodes on the same network can be easily identified. All BIDS metadata are both human and machine readable, allowing the easy extraction of subjects with electrodes covering the same network. BIDS apps will be developed to determine the speed and directionality across networks from the stimulation-evoked responses, allowing us to assess age related changes in the temporal properties of feedforward and feedback processing across the human connectome, including the pathways involved in many cognitive functions and psychiatric illnesses. This project will add unique insight into the speed and directionality of transmission along the human connectome across the life span, which is necessary to build network models of human brain function and develop novel therapeutic brain stimulation technologies that modulate the networks involved in metal illnesses.