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Lateral Interactions in Cortical Networks
Published in Mark J Rowe, Yoshiaki Iwamura, Somatosensory Processing: From Single Neuron to Brain Imaging, 2001
O.V. Favorov, J.T. Hester, D.G. Kelly, M. Tommerdahl, B.L. Whitsel
A cortical network is a complex system that contains multiple interacting circuits, generating multiple types of lateral interactions among cortical columns. The extent and importance of these lateral interactions is only now beginning to be fully appreciated, spurred by recent major advances in anatomical and physiological experimental techniques. While this area of research is still in its early stages, and a general theory of lateral interactions is yet to emerge, we distinguish — based on our experimental and modeling work — three systems of lateral interactions that take place within a cortical area. They are: (1) the most local, minicolumnar interactions, taking place among cells located within ca. 0.1mm of each other in the plane of cortical surface;(2) intermediate, macrocolumn-range interactions, within ca. 0.5mm cortical columns; and(3) long-range interactions, among more widely separated cortical columns. We will give a brief summary of each of these three systems and then introduce what we believe is a fundamental sensory information-processing task that is carried out by these lateral interactions.
Degeneration of gray and white matter differs between hypometabolic and hypermetabolic brain regions in a patient with ALS-FTD: a longitudinal MRI − PET multimodal study
Published in Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2021
Venkateswaran Rajagopalan, Erik P. Pioro
CT is attributed to the number of cells in a cortical column whereas CSA represents the number of such cortical columns (26). In addition to cell number, CT is also influenced by variations in myelination within GM or WM (27). CSA, which is also influenced by WM myelination (28) will be altered by degeneration of WM or GM. Because CT and CSA are genetically unrelated and behave independently (27), they can change in opposing directions (29), as seen in our study. Although, neuroinflammation and gliosis follow neurodegeneration, they may be primary (preceding) events in certain cases or stages of ALS. Activation of astrocytes and microglia during early stages of inflammation may contribute to cortical thickening as they hypertrophy, proliferate, extend and interdigitate their processes (30). This could explain the cortical thickening and decreased CSA we observed in the superior and middle temporal gyri of the hypometabolic areas. We propose that the stage of underlying neurodegeneration determines the type and extent of structural (CT, CSA) and metabolic changes in frontal and temporal brain regions.
Cortical projection neurons as a therapeutic target in multiple sclerosis
Published in Expert Opinion on Therapeutic Targets, 2020
Tatjana Beutel, Julia Dzimiera, Hannah Kapell, Maren Engelhardt, Achim Gass, Lucas Schirmer
Supragranular layer pyramidal neurons are important players within the organization of functional cortical columns. Their microcircuits have been studied with great detail in particular in the rodent somatosensory system [23]. The consensus is this: in primary sensory cortical areas, thalamic input mainly reaches excitatory spiny stellate and pyramidal cells in layer IV, which then disperse information upward within the cortical column and synapse onto layer II/III pyramidal neurons. These neurons constitute the majority of callosal projections [24]. As a consequence, they contribute significantly to the integration of information from both hemispheres [19,25,26]. Of note, thalamic input also reaches infragranular layer V pyramidal neurons via direct synaptic innervation [27], and can also reach supragranular layers from here. Numerous classes of locally-projecting GABAergic interneurons provide essential control of the excitation states within the network, and the entire system relies on a delicate balance of excitation and inhibition in order to function properly [28].
How the parcellation theory of comparative forebrain specialization emerged from the Division of Neuropsychiatry at the Walter Reed Army Institute of Research
Published in Journal of the History of the Neurosciences, 2021
The SIP of monocular cortical columns appears to be a later evolutionary development, as, with few exceptions, only some primates, including chimpanzees (Tigges and Tigges 1979), have such columns (see Ebbesson 1980c, 1984a). All mammals, however, share ontogenetic stages in which apparently all geniculate neurons and all layer four visual cortical neurons have binocular inputs. The ontogenetic parcellation of ocular dominance columns therefore probably reflects (to an unknown degree) their evolution.