Topographical Organization of the Pyramidal Fiber System - Diffusion Tensor MRI of the Human and Rhesus Monkey Brain

Hofer, Sabine; Frahm, Jens

doi:10.2174/1874347100903010006

Cited by 2 publications

(1 citation statement)

References 28 publications

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“…The paths axons follow from their cell bodies to their target areas for innervation enable the remarkable precision of circuit connectivity over distances up to ~10 3 cell body diameters during development, and up to ~10 5 cell body diameters in adulthood. In addition to their characteristic overall trajectories, many tracts exhibit internal topography that organizes how individual axons course through the tract in relation to one another, 28 as seen in the olfactory nerve, 20 optic nerve, 21 pyramidal/corticospinal tract, 33 hippocampal projections, 34 and corpus callosum. 12 Here, we investigated the development of topography within the corpus callosum, the largest white matter tract of the mammalian nervous system, and the foundation of interhemispheric cortico-cortical associative and integrative circuit connectivity.…”

Section: Discussionmentioning

confidence: 99%

Symmetry in levels of axon-axon homophilic adhesion establishes topography in the corpus callosum and development of connectivity between brain hemispheres

Poulopoulos,

Davis,

Brandenburg

et al. 2024

Preprint

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Specific and highly diverse connectivity between functionally specialized regions of the nervous system is controlled at multiple scales, from anatomically organized connectivity following macroscopic axon tracts to individual axon target-finding and synapse formation. Identifying mechanisms that enable entire subpopulations of related neurons to project their axons with regional specificity within stereotyped tracts to form appropriate long-range connectivity is key to understanding brain development, organization, and function. Here, we investigate how axons of the cerebral cortex form precise connections between the two cortical hemispheres via the corpus callosum. We identify topographic principles of the developing trans-hemispheric callosal tract that emerge through intrinsic guidance executed by growing axons in the corpus callosum within the first postnatal week in mice. Using micro-transplantation of regionally distinct neurons, subtype- specific growth cone purification, subcellular proteomics, and in utero gene manipulation, we investigate guidance mechanisms of transhemispheric axons. We find that adhesion molecule levels instruct tract topography and target field guidance. We propose a model in which transcallosal axons in the developing brain perform a "handshake" that is guided through co- fasciculation with symmetric contralateral axons, resulting in the stereotyped homotopic connectivity between the brain's hemispheres.

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Section: Discussionmentioning

confidence: 99%

Symmetry in levels of axon-axon homophilic adhesion establishes topography in the corpus callosum and development of connectivity between brain hemispheres

Poulopoulos,

Davis,

Brandenburg

et al. 2024

Preprint

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Motor inhibition during motor imagery: A MEG study with a quadriplegic patient

Rienzo¹,

Guillot²,

Daligault³

et al. 2013

Neurocase

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The neurophysiological substrates underlying motor imagery are now well established. However, the neural processes of motor inhibition while mentally rehearsing an action are poorly understood. This concern has received limited experimental investigations leading to divergent conclusions. Whether motor command suppression is mediated by specific brain structures or by intracortical facilitation/inhibition is a matter of debate. Interestingly, although motor commands are inhibited during motor imagery (MI) in healthy participants, spinal cord injury may result in weakened motor inhibition. Using magentoencephalography, we observed that mental and actual execution of a goal-directed pointing task elicited similar primary motor cortex activation in a C6-C7 quadriplegic patient, thus confirming the hypothesis of weakened motor inhibition during MI. In an age-matched healthy control participant, however, primary motor area activation during MI was significantly reduced compared to physical practice. Brain activation during actual movement resulted in enhanced recruitment of premotor areas in the patient. In the healthy participant, we found functional relationships between the primary motor area and peri-rolandic sites including the primary sensory area and the supplementary motor area during MI. This neural network was not activated when the quadriplegic patient performed MI. We assume that the primary sensory area and the supplementary motor area may be part of a functional network underlying motor inhibition during MI. These data provide insights into brain function changes due to neuroplasticity after spinal cord injury and evidence cortical substrates underlying weakened motor inhibition during MI after deafferentation and deefferentation.

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Topographical Organization of the Pyramidal Fiber System - Diffusion Tensor MRI of the Human and Rhesus Monkey Brain

Cited by 2 publications

References 28 publications

Symmetry in levels of axon-axon homophilic adhesion establishes topography in the corpus callosum and development of connectivity between brain hemispheres

Symmetry in levels of axon-axon homophilic adhesion establishes topography in the corpus callosum and development of connectivity between brain hemispheres

Motor inhibition during motor imagery: A MEG study with a quadriplegic patient

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