The sense of the body starts with the vestibular system and continues using joint angles and postures, starting with the head:
RP Lawson, CW Clifford and AJ Calder,
Journal of vision , Aug 26 2011
Head direction is a salient cue to the focus of other people's attention. Electrophysiology in macaques has shown head-selective cells in the superior temporal sulcus that are mostly tuned to different directions (up, down, left, right, front, back, etc.). However, there has been no systematic investigation into the visual representation of head direction in both the horizontal (left-right) and vertical (up-down) planes in humans. We addressed whether the coding of head direction is best accounted for by a multichannel system, with distinct pools of cells (or channels) tuned to different head views (i.e., left, right, direct, up, and down), or an opponent-coding system with two broadly tuned pools of cells responding to two extremes (i.e., left-right and up-down) and "direct" represented as the equilibrium state in the system. In a series of four experiments, we carried out two adaptation procedures for which multichannel and opponent coding predict distinct outcomes. The results support multichannel coding of head direction in both the vertical and horizontal axes.
http://www.physiology.org/doi/pdf/10.1152/jn.00988.2002
Look at this description of the top end of the posture and motor control system in the basal ganglia. Note that this has taps from the vestibular system not mentioned in this article:
Eventually, this works through the posture system and runs down the spine which is a powerful processor in its own right:
MD Johnson and CJ Heckman,
Frontiers in neural circuits , 2014
Motoneurons provide the only conduit for motor commands to reach muscles. For many years, motoneurons were in fact considered to be little more than passive "wires". Systematic studies in the past 25 years however have clearly demonstrated that the intrinsic electrical properties of motoneurons are under strong neuromodulatory control via multiple sources. The discovery of potent neuromodulation from the brainstem and its ability to change the gain of motoneurons shows that the "passive" view of the motor output stage is no longer tenable. A mechanism for gain control at the motor output stage makes good functional sense considering our capability of generating an enormous range of forces, from very delicate (e.g., putting in a contact lens) to highly forceful (emergency reactions). Just as sensory systems need gain control to deal with a wide dynamic range of inputs, so to might motor output need gain control to deal with the wide dynamic range of the normal movement repertoire. Two problems emerge from the potential use of the brainstem monoaminergic projection to motoneurons for gain control. First, the projection is highly diffuse anatomically, so that independent control of the gains of different motor pools is not feasible. In fact, the system is so diffuse that gain for all the motor pools in a limb likely increases in concert. Second, if there is a system that increases gain, probably a system to reduce gain is also needed. In this review, we summarize recent studies that show local inhibitory circuits within the spinal cord, especially reciprocal and recurrent inhibition, have the potential to solve both of these problems as well as constitute another source of gain modulation.
And get out to the end effectors with feedback to perform sensor fusion in the cortex:
N Bolognini and A Maravita,
Current biology : CB , Nov 2007 06
A touch on one hand can enhance the response to a visual stimulus delivered at a nearby location [1, 2], improving our interactions with the external world. In order to keep such visual-tactile spatial interactions effective, the brain updates the continuous postural changes, like those typically accompanying hand actions, through proprioception, thus maintaining the somatosensory and visual maps in spatial register [2, 3]. The posterior parietal cortex (PPC) might be critical for such a spatial remapping [4]; nevertheless, a direct causal demonstration of its involvement is lacking. Here, we found that unattended touches to one hand enhanced visual sensitivity for phosphenes induced by occipital trancranial magnetic stimulation (TMS) [5] when the touched hand was spatially coincident to the reported location of the phosphenes in external space. Notably, this spatially specific crossmodal facilitation was maintained after hand crossing, suggesting an efficient visual-tactile remapping. Critically, after 1 Hz repetitive TMS interference [6] over the PPC, but not over the primary somatosensory cortex, phosphene detection was still enhanced by spatially coincident touches with uncrossed hands, but it was enhanced by spatially noncoincident touches after hand crossing. This is the first causal evidence in humans that the PPC constantly updates the representation of the body in space in order to facilitate crossmodal interactions.
This large complicated control system is distributed over many parts of the neural system and has many different interacting parts; It’s not going to be all in the cortex.