This paper describes a major cerebral system whose contours are only emerging: the "basal ganglia related system". This is made up of the "system of the basal ganglia" itself plus its inputs and outputs. The system of the basal ganglia may be divided into the "basal ganglia core" comprising the striatum and its pallidal and nigral targets and the "regulators of the core". Distinguishable include regulators of the striatum (the dopaminergic pars compacta and the central complex of the thalamus or centre median-parafascicularis), regulators of the pallidonigrum (the subthalamic nucleus and the pedunculopontine complex) and internal regulators (at first the lateral nucleus of the pallidum). The main input to this system comes from the cerebral cortex. The main output is the thalamus and from it to the cortex. The whole "basal ganglia related system" may thus be seen as a cortico-cortical circuit passing through the basal ganglia. Information processing in the system is very complex. New data presented here emphasize two connections: cortico-striate and striato-pallidonigral connections. It is stressed that the first uses complex combinations of confluence or difluence on small matricial islands. This step could be a selection and reorganisation of cortical information. The second process is a strong "dynamically focused convergence" combining information from different upstream sources in order to derive an adequate informational product for the production of harmonious and adapted motricity.