MECHANISMS influencing clinical recovery from hemiparesis in brain infarction involve hemodynamic, biochemical, neurophysiological, and neuropsychological factors that we are only begining to understand.^1,2 Evidence based on large clinical cohorts indicates that approximately 45% of patients with hemiplegic stroke suffer from persistent hemiparesis,^3,4 whereas the larger proportion of patients recover mostly during the first 4 weeks after stroke.^5,6 As demonstrated by neurophysiological and morphometric studies, the severity of pyramidal tract damage appears to be a major predictor of outcome.⁷ Accordingly, in patients with striatocapsular stroke, initial hemiplegia may regress completely when the posterior part of the internal capsule is spared⁸ or when the magnetic evoked motor potentials are preserved.⁹ Activation studies with positron emission tomography (PET) in such patients showed that the sensorimotor cortex is recruited when the recovered hand is moved.^9,10 Against this background, the additional bilateral premotor cortical activations not seen in normal subjects during the same motor tasks¹¹ seemed to participate in rather than substitute motor cortex activity.

Background and Purpose —Recovery from hemiparesis after stroke has been shown to involve reorganization in motor and premotor cortical areas. However, whether poststroke recovery also depends on changes in remote brain structures, ie, diaschisis, is as yet unresolved. To address this question, we studied regional cerebral blood flow in 7 patients (mean±SD age, 54±8 years) after their first hemiparetic stroke. Methods —We analyzed imaging data voxel by voxel using a principal component analysis by which coherent changes in functional networks could be disclosed. Performance was assessed by a motor score and by the finger movement rate during the regional cerebral blood flow measurements. Results —The patients had recovered ( P <0.001) from severe hemiparesis after on average 6 months and were able to perform sequential finger movements with the recovered hand. Regional cerebral blood flow at rest differentiated patients and controls ( P <0.05) by a network that was affected by the stroke lesion. During blindfolded performance of sequential finger movements, patients were differentiated from controls ( P <0.05) by a recovery-related network and a movement-control network. These networks were spatially incongruent, involving motor, sensory, and visual cortex of both cerebral hemispheres, the basal ganglia, thalamus, and cerebellum. The lesion-affected and recovery-related networks overlapped in the contralesional thalamus and extrastriate occipital cortex. Conclusions —Motor recovery after hemiparetic brain infarction is subserved by brain structures in locations remote from the stroke lesion. The topographic overlap of the lesion-affected and recovery-related networks suggests that diaschisis may play a critical role in stroke recovery.

The dorsal mesial frontal cortex contains the supplementary motor area (SMA) and the pre-supplementary motor area (pre-SMA), which play an important role in action and cognition. Evidence from cytoarchitectonic, stimulation, and functional studies suggests structural and functional divergence between the two subregions. However, a microstructural map of these areas obtained in a representative sample of brains in a stereotaxic reference space is still lacking. In the present study we show that the dorsal mesial frontal motor cortex comprises two microstructurally different brain regions: area SMA and area pre-SMA. Area-specific cytoarchitectonic patterns were studied in serial histological sections stained for cell bodies of ten human postmortem brains. Borders of the two cortical areas were identified using image analysis and statistical features. The 3D reconstructed areas were transferred to a common reference space, and probabilistic maps were calculated by superimposing the individual maps. A coordinate-based meta-analysis of functional imaging data was subsequently performed using the two probabilistic maps as microstructurally defined seed regions. It revealed that areas SMA and pre-SMA were strongly co-activated with areas in precentral, supramarginal and superior frontal gyri, Rolandic operculum, thalamus, putamen and cerebellum. Both areas were related to motor functions, but area pre-SMA was involved in more complex processes such as learning, cognitive processes and perception. The here described subsequent analyses led to converging evidence supporting the microstructural, and functional segregation of areas SMA and pre-SMA, and maps will be made available to the scientific community to further elucidate the microstructural substrates of motor and cognitive control.

The topic of belief has been neglected in the natural sciences for a long period of time. Recent neuroscience research in non-human primates and humans, however, has shown that beliefs are the neuropsychic product of fundamental brain processes that attribute affective meaning to concrete objects and events, enabling individual goal setting, decision making and maneuvering in the environment. With regard to the involved neural processes they can be categorized as empirical, relational, and conceptual beliefs. Empirical beliefs are about objects and relational beliefs are about events as in tool use and in interactions between subjects that develop below the level of awareness and are up-dated dynamically. Conceptual beliefs are more complex being based on narratives and participation in ritual acts. As neural processes are known to require computational space in the brain, the formation of inceasingly complex beliefs demands extra neural resources. Here, we argue that the evolution of human beliefs is related to the phylogenetic enlargement of the brain including the parietal and medial frontal cortex in humans.