Fig. 6: Cell type wiring diagram of the MOp-ul.

a, Summary of the output connections of multiple MOp-ul cell types (ET, CT and IT) compared to those of the MOp-ul as a whole (left, black). Along each vertical path, the outputs from one Cre line tracing or single cell reconstruction experiment (identified by the prefix S, followed by a number) are summarized. The outputs begin at top with the originating MOp-ul layer(s); branches perpendicular to the main vertical path that end in ovals represent ipsilateral (right) and contralateral (left) sites of termination, identified by the brain division abbreviations at left. Branch thickness and oval size represent relative connection strength. b, A summary wiring diagram of MOp-ul cell types and predicted functional roles. A subset of cortical and striatal projection patterns is shown from the diverse MOp-ul IT cell types (six IT cell types in L2–L6b). Three types of CT neurons are shown representing different combinations of thalamic targets and MOp-ul layers of origin. Three of four types of ET neurons are also shown, projecting to subcortical targets involved in different motor functions: (1) cortico-spinal outputs to the cervical spinal cord controlling goal-directed upper limb motor activities, such as reaching and grasping; (2) cortico-medullar projections to and output from the reticular formation (for example, medullary reticular nucleus (MDRN)) are implicated in task-specific aspects of skilled motor programs⁴⁹; (3) cortico-tectal projections to the SC are implicated in coordinating movements of eye, head, neck and forelimbs during navigation and goal-oriented behaviours (such as defensive and foraging behaviour) and (4) cortico-pontine projections to the pontine grey, which generates mossy fibres to the cerebellum (which is critically involved in associative motor learning). These ET neurons also generate collateral projections to other structures in the motor system, such as GPe, ZI, STN, RN and IO. ACAv/d, anterior cingulate area, ventral and dorsal part; AIp, agranular insular area, posterior part; AIv, agranular insular area, ventral part; CBN, cerebellar nuclei; CNU, cerebral nuclei; CTX, cortex; MB, midbrain; MDc, mediodorsal nucleus of thalamus, capsular part; NPC, nucleus of the posterior commissure; P, pons; ORBvl/l, orbital area, ventrolateral and lateral part; PARN, parvicellular reticular nucleus; SMT, submedial nucleus of the thalamus; SPFp, subparafascicular nucleus, pavicellular part; TH, thalamus.