The Basic Uniformity in Structure of the Neocortex

Röckel, A; Hiorns, R. W.; Powell, T. P. S.

doi:10.1093/brain/103.2.221

Cited by 854 publications

(441 citation statements)

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“…The highest density of neurons in neocortex (number of neurons per degree of visual angle) devoted to representing the visual field is found in V1 (Rockel and Hiorns, 1980;Van Essen and Anderson, 1992). This means that the highest mitochondrial activity can be achieved in the cytochrome oxidase-rich blobs.…”

Section: Retinotopic Organization Mitochondrial Cytochrome Oxidase-rmentioning

confidence: 98%

Visual perception and imagery: A new molecular hypothesis

Bókkon

2009

Biosystems

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Here, we put forward a redox molecular hypothesis about the natural biophysical substrate of visual perception and visual imagery. This hypothesis is based on the redox and bioluminescent processes of neuronal cells in retinotopically organized cytochrome oxidaserich visual areas. Our hypothesis is in line with the functional roles of reactive oxygen and nitrogen species in living cells that are not part of haphazard process, but rather a very strict mechanism used in signaling pathways. We point out that there is a direct relationship between neuronal activity and the biophoton emission process in the brain. Electrical and biochemical processes in the brain represent sensory information from the external world. During encoding or retrieval of information, electrical signals of neurons can be converted into synchronized biophoton signals by bioluminescent radical and non-radical processes. Therefore, information in the brain appears not only as an electrical (chemical) signal but also as a regulated biophoton (weak optical) signal inside neurons.During visual perception, the topological distribution of photon stimuli on the retina is represented by electrical neuronal activity in retinotopically organized visual areas. These retinotopic electrical signals in visual neurons can be converted into synchronized biophoton signals by radical and non-radical processes in retinotopically organized mitochondrial-rich areas. As a result, regulated bioluminescent biophotons can create intrinsic pictures (depictive representation) in retinotopically organized cytochrome oxidase-rich visual areas during visual imagery and visual perception. The long-term visual memory is interpreted as epigenetic information regulated by free radicals and redox processes. This hypothesis does not claim to solve the secret of consciousness, but proposes that the evolution of higher levels of complexity made the intrinsic picture representation of the external visual world possible by regulated redox and bioluminescent reactions in the visual system during visual perception and visual imagery.

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Section: Retinotopic Organization Mitochondrial Cytochrome Oxidase-rmentioning

confidence: 98%

Visual perception and imagery: A new molecular hypothesis

Bókkon

2009

Biosystems

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“…In the mature cerebral cortex, the two populations of neurons can be reliably marked by the presence of the classical neurotransmitters Glu or GABA. The numerical relationship between these two neuronal cell types is very similar in different cortical areas and in various mammalian species (Rockel et al, 1980;Hendt-y et al, 1987;Meinecke and Peters, 1987) with a large preponderance of pyramidal over nonpyramidal neurons, suggesting that their production is regulated by rigidly controlled mechanisms. Any imbalance of excitatory and inhibitory stimuli can seriously alter cortical functions leading to epileptogenesis (Traub et al, 1987) and degeneration of neuronal circuits (Mattson and Kater, 1989).…”

mentioning

confidence: 98%

Lineage analysis reveals neurotransmitter (GABA or glutamate) but not calcium-binding protein homogeneity in clonally related cortical neurons

et al. 1994

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Studies of cell lineage in the rat cerebral cortex have provided new insights into the mechanisms of neuronal and glial determination. They have shown that clonally related cells, marked with retrovirus injection at embryonic day 16 (E16), express the same glial or neuronal phenotype, suggesting that separate progenitors for each of these cell phenotypes exist in the ventricular zone at that stage of corticogenesis. However, it is not known if such committed progenitors are present in the ventricular zone before E16. Another important question concerns which neurochemical features are shared by clonally related cells of the adult cerebral cortex. In this study we have addressed the first question by injecting a retroviral vector expressing beta-galactosidase into the telencephalic ventricles of rat embryos at different stages (E14-E19). In order to classify clonally related neurons in the cerebral cortex of these rats, we have used postembedding immunohistochemistry for the amino acid neurotransmitters glutamate, aspartate, and GABA. Glutamate and GABA immunoreactivity marked nonoverlapping populations of cells that corresponded to the pyramidal and nonpyramidal neuron types of the rat cerebral cortex. Clonally related neurons, marked by retrovirus injection at any day between E14 and E19, homogeneously expressed one or other phenotype and accordingly displayed glutamate or GABA immunoreactivity. This finding indicates that committed progenitor cells for pyramidal and nonpyramidal neurons are present in the ventricular zone before E16. To investigate whether lineage dictates other features in clonally related neurons, we performed an immunohistochemical analysis for the calcium- binding proteins calbindin, parvalbumin, and calretinin in clusters of clonally related nonpyramidal neurons. The same calcium-binding protein was rarely found in members of the same cluster, suggesting that lineage does not control the expression of calcium-binding proteins in cortical nonpyramidal neurons. As a result of examining a large number of clonally related neurons from brains injected at different ages, we observed remarkable differences in number and laminar distribution of pyramidal and nonpyramidal neurons marked with retrovirus. Clusters of nonpyramidal neurons were usually composed of two or three cells, and resided in the cortical layers that were just being generated at the time of injection. Clusters of pyramidal neurons were larger and dispersed in several layers in the earlier injections; their size and laminar distribution were progressively reduced for later injections. These observations suggest the existence of different mechanisms that generate the pyramidal and nonpyramidal neurons of the cerebral cortex.

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“…Each mm 2 of cortical layer IVc tissue will contain afferents from roughly 1200 ganglion cells each having roughly 3000 synaptic connections to cortical cells. Further, from the neuron density of about 105/ram 3 for monkeys (Rockel et al 1980), one can estimate layer IVc to contain about 2.104 cells per mm 2, which then receive 4. 10 6 afferent terminals.…”

Section: Discussionmentioning

confidence: 99%

Emergence of orientation selective simple cells simulated in deterministic and stochastic neural networks

1993

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Abstract. The processing of visual data in area 17 of the mammalian cortex is mainly performed by cells with receptive fields which are tuned to different orientations of input stimuli. The mechanisms underlying the emergence of receptive field properties of orientation selective cells are not well understood up to now. Recently, some models for the prenatal development of the receptive fields of orientation selective simple cells have been proposed, which emerge in neural networks trained by Hebb type unsupervised learning rules. These models, however, use different network architectures and are restricted to the case of identical input neurons. In this work, a biologically motivated neural network model with a general architecture is presented. It is trained with a Hebb type updating rule and with uncorrelated input. The input neurons are identified with retinal ganglion cells and exhibit mature Mexican hat type receptive fields. If the receptive fields of the input neurons have identical properties (deterministic model), a set of parameter domains is found, which characterize different kinds of receptive field maturation behaviour of the network. Results obtained by other authors with similar models are contained in this description as special cases. In addition, the more general and rarely investigated stochastic model, where random variations of the parameters describing the receptive fields of the input neurons occur, is investigated. A high sensitivity of the network against these random variations is obtained. In case of large variations of receptive field parameters of the ganglion cells, a qualitatively new kind of maturation behaviour appears. A significant part of the synaptic connections from ganglion cells to the cortical cell is removed and small simple cell receptive fields with only few lobes emerge. The stochastic model is found to provide a better description of the size, scatter and structure of receptive fields present in biological systems, than the deterministic model.

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The Basic Uniformity in Structure of the Neocortex

Cited by 854 publications

References 0 publications

Visual perception and imagery: A new molecular hypothesis

Visual perception and imagery: A new molecular hypothesis

Lineage analysis reveals neurotransmitter (GABA or glutamate) but not calcium-binding protein homogeneity in clonally related cortical neurons

Emergence of orientation selective simple cells simulated in deterministic and stochastic neural networks

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