The organization of the human cerebellum estimated by intrinsic functional connectivity. J Neurophysiol 106: 2322-2345. First published July 27, 2011 doi:10.1152/jn.00339.2011The cerebral cortex communicates with the cerebellum via polysynaptic circuits. Separate regions of the cerebellum are connected to distinct cerebral areas, forming a complex topography. In this study we explored the organization of cerebrocerebellar circuits in the human using restingstate functional connectivity MRI (fcMRI). Data from 1,000 subjects were registered using nonlinear deformation of the cerebellum in combination with surface-based alignment of the cerebral cortex. The foot, hand, and tongue representations were localized in subjects performing movements. fcMRI maps derived from seed regions placed in different parts of the motor body representation yielded the expected inverted map of somatomotor topography in the anterior lobe and the upright map in the posterior lobe. Next, we mapped the complete topography of the cerebellum by estimating the principal cerebral target for each point in the cerebellum in a discovery sample of 500 subjects and replicated the topography in 500 independent subjects. The majority of the human cerebellum maps to association areas. Quantitative analysis of 17 distinct cerebral networks revealed that the extent of the cerebellum dedicated to each network is proportional to the network's extent in the cerebrum with a few exceptions, including primary visual cortex, which is not represented in the cerebellum. Like somatomotor representations, cerebellar regions linked to association cortex have separate anterior and posterior representations that are oriented as mirror images of one another. The orderly topography of the representations suggests that the cerebellum possesses at least two large, homotopic maps of the full cerebrum and possibly a smaller third map. somatotopy; motor control; prefrontal; functional magnetic resonance imaging; default network; connectome THE ORGANIZATION OF THE CEREBELLUM has been the topic of debate for more than a century (Manni and Petrosini 2004). Although there is agreement that the cerebellum contains multiple somatomotor representations, a challenging feature of cerebellar anatomy prevents resolving its complete organization: the cerebellum is connected to the cerebral cortex only by way of polysynaptic circuits (Evarts and Thach 1969;Kemp and Powell 1971;Schmahmann and Pandya 1997a;Strick 1985). Efferent projections from the cerebrum synapse initially in the pontine nuclei and then project primarily to the contralateral cerebellar cortex (the pontocerebellar tract). Afferent projections first synapse in the deep cerebellar nuclei (e.g., dentate nucleus) and then project to a second synapse in the contralateral thalamus that in turn serves as a relay to the cerebral cortex (the dentatothalamocortical tract). There are no monosynaptic connections between the cerebrum and cerebellum. As a result, traditional anterograde and retrograde tracing techniques cannot be u...

Traumatic brain injury (TBI) is a major cause of death and disability in all age groups. Among TBI, penetrating traumatic brain injuries (PTBI) have the worst prognosis and represent the leading cause of TBI-related morbidity and death. However, there are no specific drugs/interventions due to unclear pathophysiology. To gain insights we looked at cerebral metabolism in a PTBI rat model: penetrating ballistic-like brain injury (PBBI). Early after injury, regional cerebral oxygen tension and consumption significantly decreased in the ipsilateral cortex in the PBBI group compared with the control group. At the same time point, glucose uptake was significantly reduced globally in the PBBI group compared with the control group. Examination of Fluorojade B-stained brain sections at 24 hours after PBBI revealed an incomplete overlap of metabolic impairment and neurodegeneration. As expected, the injury core had the most severe metabolic impairment and highest neurodegeneration. However, in the peri-lesional area, despite similar metabolic impairment, there was lesser neurodegeneration. Given our findings, the data suggest the presence of two distinct zones of primary injury, of which only one recovers. We anticipate the peri-lesional area encompassing the PBBI ischemic penumbra, could be salvaged by acute therapies.