across the cortex receive inputs to layer I from M-type thalamic neurons distributed in most thalamic nuclei [59–64]. In addition, pyramidal neurons in layer-VI are known to target all thalamic nuclei. Furthermore, FC between somatosensory thalamus (ventral posterolateral nucleus, VPL) and layers IV and VI of the primary somatosensory cortex (S1), must be stronger than other layers. This follows from the well-known C-type thalamic neurons in VPL that primarily target layer IV in the primary somatosensory cortex, and then corticothalamic pyramidal neurons in layer VI are known to project back to C-type thalamic neurons in VPL [65, 66], (2) inter-hemispheric cortico-cortical FC (i.e., between the left and right brain regions of the same area) in superficial layers (layers I–III) must be higher compared to deep layers (layers V–VI). This follows from evidence in rodents that 80% of the cell bodies of those callosal projecting neurons are distributed in layer II and layer III, with only 20% in layers V and VI [67, 68]. Other studies have claimed that layers I through III are the main target of inter-hemispheric cortico-cortical afferents, while some suggest that layer III is the main source of cortico-cortical efferents [69–71]. Taken together, it makes sense to
