The most distinct feature of the mammalian cerebral cortex is its laminar structure, comprised of cortical columns. A cortical column is a unit of complex information processing. It consists of processing chains that overlap, linking multiple inputs to multiple other outputs [1]. A single column of cerebral cortical gray matter normally has six layers. Different layers in the column have distinct distribution and types of neurons as well as separate connections with other cortical and subcortical regions. Our knowledge about cortical laminar-specific connections is mostly derived from invasive studies including histology, anatomical tract tracing, electrophysiology, and lesion methods [2–7], given that non-invasive modalities, such as magnetic resonance imaging (MRI), both anatomical and functional, have typically lacked the resolution to resolve layer-specific differences.
