Information processing in the cerebral cortex involves interactions among distributed areas. Anatomical connectivity suggests that certain areas form local hierarchical relations such as within the visual system. Other connectivity patterns, particularly among association areas, suggest the presence of large-scale circuits without clear hierarchical relations. In this study the organization of networks in the human cerebrum was explored using resting-state functional connectivity MRI. Data from 1,000 subjects were registered using surface-based alignment. A clustering approach was employed to identify and replicate networks of functionally coupled regions across the cerebral cortex. The results revealed local networks confined to sensory and motor cortices as well as distributed networks of association regions. Within the sensory and motor cortices, functional connectivity followed topographic representations across adjacent areas. In association cortex, the connectivity patterns often showed abrupt transitions between network boundaries. Focused analyses were performed to better understand properties of network connectivity. A canonical sensory-motor pathway involving primary visual area, putative middle temporal area complex (MT+), lateral intraparietal area, and frontal eye field was analyzed to explore how interactions might arise within and between networks. Results showed that adjacent regions of the MT+ complex demonstrate differential connectivity consistent with a hierarchical pathway that spans networks. The functional connectivity of parietal and prefrontal association cortices was next explored. Distinct connectivity profiles of neighboring regions suggest they participate in distributed networks that, while showing evidence for interactions, are embedded within largely parallel, interdigitated circuits. We conclude by discussing the organization of these large-scale cerebral networks in relation to monkey anatomy and their potential evolutionary expansion in humans to support cognition.

The organization of the human cerebral cortex estimated by intrinsic functional connectivity

https://www.cell.com/neuron/pdf/S0896-6273(13)00996-3.pdf

The Cerebellum and Cognitive Function: 25 Years of Insight from Anatomy and Neuroimaging

The cerebellum and neural control

The evolution of distributed association networks in the human brain.

The cerebellum has long been regarded as essential only for the coordination of voluntary motor activity and motor learning. Anatomical, clinical and neuroimaging studies have led to a paradigm shift in the understanding of the cerebellar role in nervous system function, demonstrating that the cerebellum appears integral also to the modulation of cognition and emotion. The search to understand the cerebellar contribution to cognitive processing has increased interest in exploring the role of the cerebellum in neurodegenerative and neuropsychiatric disorders. Principal among these is Alzheimer's disease. Here we review an already sizeable existing literature on the neuropathological, structural and functional neuroimaging studies of the cerebellum in Alzheimer's disease. We consider these observations in the light of the cognitive deficits that characterize Alzheimer's disease and in so doing we introduce a new perspective on its pathophysiology and manifestations. We propose an integrative hypothesis that there is a cerebellar contribution to the cognitive and neuropsychiatric deficits in Alzheimer's disease. We draw on the dysmetria of thought theory to suggest that this cerebellar component manifests as deficits in modulation of the neurobehavioural deficits. We provide suggestions for future studies to investigate this hypothesis and, ultimately, to establish a comprehensive, causal clinicopathological disease model.

/pdf/the-cerebellum-in-alzheimer-s-disease-evaluating-its-role-in-2zrzli80g0.pdf

The cerebellum in Alzheimer's disease: evaluating its role in cognitive decline.

The mystery of the human cerebellum is this: Why did it enlarge so dramatically in the last million years of human evolution, concomitantly with the greater enlargement of the cerebral cortex? A solution to this mystery was proposed in the 20th century as a result of research by several groups of scientists who investigated the contributions of the cerebellum to the cerebral cortex. In contrast to the 19th century investigations, which were focused on the motor functions of the cerebellum, the focus of the subsequent investigations was expanded to include some mental functions because evidence was produced that the cerebellum contributes to cognition. It was proposed that the combination in the cerebellum of motor and mental capabilities enables the cerebellum to confer on humans some adaptive advantages of great value, and this ability would explain why the human cerebellum has continued to enlarge so dramatically. A valuable adaptive advantage that is included in the proposal is the possibility that the cerebellum couples the motor function of articulating speech to the mental function that selects the language to be spoken, thus helping to produce fluent human speech and language. The validity of this proposal about linguistic processing has not yet been verified. Therefore the mystery of cerebellar enlargement in humans is not yet solved and requires further research.

Henrietta C. Leiner

Papers

Solving the Mystery of the Human Cerebellum