Functional Organization Of Neurons Research Articles

Ion dynamics at the energy-deprived tripartite synapse.

The anatomical and functional organization of neurons and astrocytes at 'tripartite synapses' is essential for reliable neurotransmission, which critically depends on ATP. In low energy conditions, synaptic transmission fails, accompanied by a breakdown of ion gradients, changes in membrane potentials and cell swelling. The resulting cellular damage and cell death are causal to the often devastating consequences of an ischemic stroke. The severity of ischemic damage depends on the age and the brain region in which a stroke occurs, but the reasons for this differential vulnerability are far from understood. In the present study, we address this question by developing a comprehensive biophysical model of a glutamatergic synapse to identify key determinants of synaptic failure during energy deprivation. Our model is based on fundamental biophysical principles, includes dynamics of the most relevant ions, i.e., Na+, K+, Ca2+, Cl- and glutamate, and is calibrated with experimental data. It confirms the critical role of the Na+/K+-ATPase in maintaining ion gradients, membrane potentials and cell volumes. Our simulations demonstrate that the system exhibits two stable states, one physiological and one pathological. During energy deprivation, the physiological state may disappear, forcing a transit to the pathological state, which can be reverted when blocking voltage-gated Na+ and K+ channels. Our model predicts that the transition to the pathological state is favoured if the extracellular space fraction is small. A reduction in the extracellular space volume fraction, as, e.g. observed with ageing, will thus promote the brain's susceptibility to ischemic damage. Our work provides new insights into the brain's ability to recover from energy deprivation, with translational relevance for diagnosis and treatment of ischemic strokes.

THE NEUROMORPHOLOGICAL CORRELATION OF RADIATION DOSE RATE

Relevance. Liquidators of consequences of the radiation accidents demonstrate increased rates of psychoneurological diseases after radiation exposure. However, the functional reorganization of brain neurons versus radiation exposure is insufficiently studied, thus precluding assessment of the pathogenesis of these diseases.Intention. To study neuromorphological correlates of low-dose radiation effects on brain neurons in radiobiological experiments.Methodology. In this GLP study, white outbred male rats (150 animals) at the age of 4 months were exposed to 0,5 Gy 60Co γ-rays at 0.5, 1.0, 2.5, 6.6 Gy/h. Age control group included animals with false exposure. Brain samples were taken 1 day, 6, 12, 18, 24 months after exposure. After conventional histologic processing, tinctorial properties, morphometric parameters, total protein and nucleic acids were assessed in neurons with subsequent mathematical modeling.Results and analysis. Normochromic neurons decreased linearly and their destructive forms increased over the observation period with increase in the irradiation dose. Among reversible changes, neurons in a state of inhibition and decreased functional activity predominated. The nerve cell index decreased over time, therefore some neurons died. Neuronal morphometry fluctuated, as well as their main structures, protein, cytoplasm and nucleolus RNA, nucleus DNA. With increasing dose rate, the changes became more expressed, and differed from the control group. These changes could be a basis for pathological processes in the brain.Conclusion. The ionizing radiation of studied range doesn’t cause significant organic changes of the brain neurons. However, under increasing radiation exposure the number of dysfunctional neurons linearly increases, as well as altered neurons. Almost all the neuromorphological parameters change, thus resulting in instability of structural – functional organization of neurons, with potential CNS disorders.

Learning Invariant Features in Modulatory Networks through Conflict and Ambiguity.

This work lays the foundation for a framework of cortical learning based on the idea of a competitive column, which is inspired by the functional organization of neurons in the cortex. A column describes a prototypical organization for neurons that gives rise to an ability to learn scale, rotation, and translation-invariant features. This is empowered by a recently developed learning rule, conflict learning, which enables the network to learn over both driving and modulatory feedforward, feedback, and lateral inputs. The framework is further supported by introducing both a notion of neural ambiguity and an adaptive threshold scheme. Ambiguity, which captures the idea that too many decisions lead to indecision, gives the network a dynamic way to resolve locally ambiguous decisions. The adaptive threshold operates over multiple timescales to regulate neural activity under the varied arrival timings of input in a highly interconnected multilayer network with feedforward and feedback. The competitive column architecture is demonstrated on a large-scale (54,000 neurons and 18 million synapses), invariant model of border ownership. The model is trained on four simple, fixed-scale shapes: two squares, one rectangle, and one symmetric L-shape. Tested on 1899 synthetic shapes of varying scale and complexity, the model correctly assigned border ownership with 74% accuracy. The model's abilities were also illustrated on contours of objects taken from natural images. Combined with conflict learning, the competitive column and ambiguity give a better intuitive understanding of how feedback, modulation, and inhibition may interact in the brain to influence activation and learning.

The neuromorphological correlates of prolonged radiation exposure

Relevance.Liquidators of the consequences of radiation accidents have an increase in neuropsychiatric diseases. However, the structural and functional rearrangement of brain neurons under prolonged low radiation exposure remains virtually unexplored, which makes it difficult to assess the pathogenesis of these diseases.Intention.To study morphological correlates of prolonged low radiation effects on brain neurons in the model of radiobiological experiment.Method.270 white outbred male rats aged 4 months were exposed to radiation-quanta of 60Co in equal portions in total doses of 10; 20; 50 and 100 cGy with a dose rate of 0.5 Gy/h over 5 days. Age control consisted of animals exposed to false radiation. Animal studies complied with GLP standards. Brain fragments were taken after 1 day, 6, 12, 18 and 24 months after irradiation. After a standard histological treatment, changes in the tinctorial properties of neurons, their morphometric parameters, total protein and nucleic acids were evaluated.Results and their analysis. At the end of the observation period, the number of normochromic neurons decreased and the number of hyper and hypochromic cells increased, as well as their destructive forms. The neuro-cellular index decreased over time suggesting the death of some neurons, but without a statistically significant decrease in their number per area. In the post-irradiation period there were observed phase changes in the size of the cytoplasm, nucleus and nucleolus of neurons, as well as the content of protein and nucleic acids (RNA in the cytoplasm and nucleoli, DNA in the nuclei), more pronounced in irradiated animals and sometimes different from those observed in age control animals. As a result, a number of neuromorphological parameters in some periods of observation were not consistent with those in control animals, with a certain instability in the structural and functional organization of neurons.Conclusion.Prolonged low-dose ionizing radiation does not cause significant organic changes in the brain. However, increased radiation exposure or other concomitant adverse factors can be associated with further instability of the structural and functional organization of neurons and serve as a material substrate for a number of deviations in the central nervous system.

Aberrant long-range functional connectivity density in generalized tonic-clonic seizures.

Studies in generalized tonic-clonic seizures (GTCS) have reported both structural and functional alterations in the brain. However, changes in spontaneous neuronal functional organization in GTCS remain largely unknown.In this study, 70 patients with idiopathic generalized epilepsy characterized by tonic-clonic seizures and 70 age- and sex-matched healthy controls were recruited. Here, functional connectivity density (FCD) mapping, an ultrafast data-driven method based on functional magnetic resonance imaging (fMRI), was applied for the first time to investigate the changes of spontaneous functional brain activity caused by epilepsy.The results showed significantly decreased long-range FCD in the middle and inferior temporal, prefrontal, and inferior parietal cortices as well as increased long-range FCD in the cerebellum anterior lobe and sensorimotor areas. Negative correlation between duration of disease and reduced long-range FCD was found. In addition, most regions with reduced long-range FCD showed decreased resting-state functional connectivity (rsFC) within default mode network.Negative correlation between duration of disease and long-range FCD may reflect an adverse consequence eventually from original. Furthermore, the observed FCD and rsFC alterations have been speculated to be associated with the social-cognitive impairments as well as motor control. Our study provided novel evidences to look into neuro-pathophysiological mechanisms underlying GTCS.

Experience-dependent plasticity of neurovascularization.

Experience powerfully shapes structural and functional organization of neurons during development and in adulthood. Recent experiments in the mouse primary somatosensory cortex now suggest that experience is also a critical factor in shaping neurovasculature and promoting angiogenesis. These results support the universality of brain plasticity and show that all structural cellular components in the brain, from neuron and glia to epithelia, are shaped by experience.

Neuron Activity before Behavioral Reactions and before Missed Reactions in a Defensive Dominant

The network relationships of neocortical neurons in rabbits with a defensive dominant in the CNS were studied in conditions of calm waking and during the intervals between presentations of light stimuli testing the dominant. Statistical analysis of spike trains extracted from multineuron traces allowed detection of differences in the functional organization of neurons in the excitation focus (sensorimotor cortex) and the representation area of the stimulus testing it (visual cortex) in calm waking before triggering of effector reactions and before missed reactions. These experiments yielded data on the different roles of sensorimotor cortex cells responding and not responding to light stimuli in the network activity of the areas of cortex studied.

Creating modern neuroscience: the revolutionary 1950s

Preface 1. Introduction: Why Study History? Why the 1940s and the 1950s? 2. Genes: Starting with DNA 3. Signaling Molecules: The First Growth Factor 4. The First Neurotransmitters in the Brain 5. Cell Biology and the Synapse 6. Physiology: The Action Potential 7. Phsyiology: Synaptic Potentials and Receptor Potentials 8. Functional Organization of Neurons and Dendrites 9. Neural Circuits: Spinal Cord, Retina, Invertebrate Systems 10. Neural Circuits: Cortical Columns and Cortical Processing 11. Neural Systems: The Neural Basis of Behavior 12. Learning and Memory: Donald Hebb, Brenda Milner, and HM 13. Neurology: Foundations of Brain Imaging 14. Neurosurgery: From Cushing to Penfield 15. Neuropsychiatry: The Breakthrough in Psychopharmacology 16. Theoretical Neuroscience: The Brain as a Computer and the Computer as a Brain References Links Notes Index

Revealing neuronal functional organization through the relation between multi-scale oscillatory extracellular signals

The spatial organization of neuronal elements and their connectivity make up the substrate underlying the information processing carried out in the networks they form. Conventionally, anatomical findings make the initial structure which later combines with superimposed neurophysiological information to create a functional organization map. The most common neurophysiological measure is the single neuron spike train extracted from an extracellular recording. This single neuron firing pattern provides valuable clues on information processing in a given brain area; however, it only gives a sparse and focal view of this process. Even with the increase in number of simultaneously recorded neurons, inference on their large-scale functional organization remains problematic. We propose a method of utilizing additional information derived from the same extracellular recording to generate a more comprehensive picture of neuronal functional organization. This analysis is based on the relationship between the oscillatory activity of single neurons and their neighboring neuronal populations. Two signals that reflect the multiple scales of neuronal populations are used to complement the single neuron spike train: (1) the high-frequency background unit activity representing the spiking activity of small localized sub-populations and (2) the low-frequency local field potential that represents the synaptic input to a larger global population. The three coherences calculated between pairs of these three signals arising from a single source of extracellular recording are then used to infer mosaic representations of the functional neuronal organization. We demonstrate this methodology on experimental data and on simulated leaky integrate-and-fire neurons.

Clustered Organization of Neurons with Similar Extra-Receptive Field Properties in the Primary Visual Cortex

The primary visual cortex is organized into clusters of cells having similar classical receptive field (CRF) properties. Nonclassical, extra-receptive fields (ERFs) can either inhibit or facilitate the response elicited by stimulation within the CRF. Here, we report that in the primary visual cortex of cat, neurons with similar inhibitory or facilitatory ERF properties are also grouped into clusters. These clusters are randomly distributed in all cortical layers, with no detectable relationship with orientation and ocular dominance columns. This functional organization of neurons with respect to ERF properties may allow an efficient processing of global visual information.

Responses of pigeon vestibulocerebellar neurons to optokinetic stimulation. I. Functional organization of neurons discriminating between translational and rotational visual flow.

1. Extracellular recordings were made from 235 neurons in the vestibulocerebellum (VbC), including the flocculus (lateral VbC), nodulus (folium X), and ventral uvula (ventral folium IXc,d), of the anesthetized pigeon, in response to an optokinetic stimulus. 2. The optokinetic stimuli consisted of two black and white random-dot patterns that were back-projected onto two large tangent screens. The screens were oriented parallel to each other and placed on either side of the bird's head. The resultant stimulus covered the central 100 degrees x 100 degrees of each hemifield. The directional tuning characteristics of each unit were assessed by moving the largefield stimulus in 12 different directions, 30 degrees apart. The directional tuning curves were performed monocularly or binocularly. The binocular directional tuning curves were performed with the direction of motion the same in both eyes (in-phase; e.g., ipsi = upward, contra = upward) or with the direction of motion opposite in either eye (antiphase; e.g., ipsi = upward, contra = downward). 3. Mossy fiber units (n = 17) found throughout folia IXa,b and IXc,d had monocular receptive fields and exhibited direction selectivity in response to stimulation of either the ipsilateral (n = 12) or contralateral (n = 5) eye. None had binocular receptive fields. 4. The complex spike (CS) activity of 218 Purkinje cells in folia IXc,d and X exhibited direction selectivity in response to the large-field visual stimulus moving in one or both visual fields. Ninety-one percent of the cells had binocular receptive fields that could be classified into four groups: descent neurons (n = 112) preferred upward motion in both eyes; ascent neurons (n = 14) preferred downward motion in both eyes; roll neurons (n = 33) preferred upward and downward motion in the ipsilateral and contralateral eyes, respectively; and yaw neurons (n = 40) preferred forward and backward motion in the ipsilateral and contralateral eyes, respectively. Within all groups, most neurons (70%) showed an ipsilateral dominance. 5. For most binocular neurons (91%), the maximum depth of modulation occurred with simultaneous stimulation of both eyes, compared with monocular stimulation of the dominant eye alone. For the translation neurons (descent and ascent), binocular inphase stimulation produced the maximum depth of modulation, whereas for the rotation neurons (roll and yaw), binocular antiphase stimulation produced the maximum depth of modulation. 6. There was a clear functional segregation of the translation and rotation neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Response properties and functional organization of neurons in midline region of medullary reticular formation of cats.

Extracellular single-unit recordings were made in the anesthetized cat from neurons within the medullary raphe nuclei and nearby reticular formation. The descending axons from some of these neurons were characterized in terms of length, conduction velocity, and location within the white matter of the spinal cord. The sensory properties were characterized following somatic, baroreceptor, visual, and auditory stimuli. The mean conduction velocities of the descending axons from neurons in the medullary raphe nuclei and in the magnocellular tegmental field (26 m/s) were significantly slower than the mean conduction velocities of units in the regions immediately dorsal to them (50 m/s). Action potentials in neurons in the medullary raphe nuclei and in the magnocellular tegmental field were evoked by anti-dromic stimulation from the dorsolateral portion of the spinal cord (30 of 43, 70%), whereas neurons located in more dorsal regions along the midline and in the reticular formation projected into the ventral columns (18 of 25, 72%). Neurons were most easily activated by a tap stimulus to the body surface. This stimulus activated 84% of the neurons tested. The receptive fields were large, often including the four limbs, back, and head. Tap-sensitive neurons were found throughout the regions investigated. Stimulation of hair receptors activated 37% of neurons tested, whereas 19% responded to a high-intensity cutaneous stimulus (pinch), 35% responded to baroreceptor stimuli, 32% responded to visual stimuli, and 33% responded to auditory stimuli. Neurons responsive to pinch were likely to respond to baroreceptor stimuli and unlikely to respond to visual stimuli. Neurons responsive to visual stimuli were likely to respond to auditory stimuli.

Functional organization of neurons in cat striate cortex: variations in preferred orientation and orientation selectivity with receptive-field type, ocular dominance, and location in visual-field map.

ArticlesFunctional organization of neurons in cat striate cortex: variations in preferred orientation and orientation selectivity with receptive-field type, ocular dominance, and location in visual-field mapB. R. Payne, and N. BermanB. R. Payne, and N. BermanPublished Online:01 Apr 1983https://doi.org/10.1152/jn.1983.49.4.1051MoreSectionsPDF (3 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Download PDF FiguresReferencesRelatedInformation Cited ByOrientation anisotropies in human primary visual cortex depend on contrastNeuroImage, Vol. 119Phase sensitivities, excitatory summation fields, and silent suppressive receptive fields of single neurons in the parastriate cortex of the catPhillip A. Romo, Chun Wang, Natalie Zeater, Samuel G. Solomon, and Bogdan Dreher1 October 2011 | Journal of Neurophysiology, Vol. 106, No. 4Visual experience promotes the isotropic representation of orientation preference3 May 2004 | Visual Neuroscience, Vol. 21, No. 01Representation of Cardinal Contour Overlaps Less With Representation of Nearby Angles in Cat Visual CortexGang Wang, Shan Ding, and Kazutomo Yunokuchi1 December 2003 | Journal of Neurophysiology, Vol. 90, No. 6Oblique Effect: A Neural Basis in the Visual CortexBaowang Li, Matthew R. Peterson, and Ralph D. Freeman1 July 2003 | Journal of Neurophysiology, Vol. 90, No. 1Difference in the representation of cardinal and oblique contours in cat visual cortexNeuroscience Letters, Vol. 338, No. 1Three-dimensional form and a simple, interrupted flat map of a single layer in the lateral geniculate nucleus of the catBrain Research, Vol. 525, No. 1Neural mapping and space-variant image processingNeural Networks, Vol. 3, No. 3Consequences of visual deprivation in the absence of binocular competitive mechanisms in Siamese cat area 17Developmental Brain Research, Vol. 50, No. 1Directional and orientational tuning of feline striate cortical neurones: Correlation with neuronal classVision Research, Vol. 29, No. 6Neural motion after-effects in the cat's striate cortex: Orientation selectivityVision Research, Vol. 29, No. 12Modular organization of on and off responses in the cat lateral geniculate nucleusNeuroscience, Vol. 32, No. 3Cat spatial visionTrends in Neurosciences, Vol. 11, No. 2Point images, receptive fields, and retinotopic mappingTrends in Neurosciences, Vol. 10, No. 8The effect of practice on the oblique effect in line orientation judgmentsVision Research, Vol. 25, No. 11Orientation selectivity in cats and humans assessed by maskingVision Research, Vol. 25, No. 10Deafferentation and axotomy of neurons in cat striate cortex: Time course of changes in binocularity following corpus callosum transectionBrain Research, Vol. 307, No. 1-2Spatiotemporal conditions which elicit or abolish the oblique effect in man: Direct measurement with swept evoked potentialVision Research, Vol. 24, No. 6 More from this issue > Volume 49Issue 4April 1983Pages 1051-1072 Copyright & PermissionsCopyright © 1983 the American Physiological Societyhttps://doi.org/10.1152/jn.1983.49.4.1051PubMed6854357History Published online 1 April 1983 Published in print 1 April 1983 Metrics

Functional organization of neurons in cat striate cortex: variations in ocular dominance and receptive-field type with cortical laminae and location in visual field.

1. Binocularity and receptive-field type of cortical neurons were assessed relative to the cortical layer in which the neurons were recorded and to receptive-field position in the visual field. 2. Receptive fields were observed up to 2 degrees into the ipsilateral half of the visual field. In the region up to 2 degrees on either side of the vertical meridian, the relative contribution of the ipsilateral eye was reduced. This progression in ocular dominance from ipsilateral to contralateral visual field agrees well with the distribution of X-cells about the nasotemporal division. 3. The region of maximum binocularity in each hemifield was found to be a 12 degree wide vertical strip extending from the vertical meridian to 12 degrees contralateral. In the representation of the central 12 degree strip, most units in all cortical layers were binocular. 4. Low levels of binocularity were observed at a considerable distance before the monocular portion of the visual field was reached. 5. The decrease in binocularity for simple cells occurred closer to the vertical meridian than for complex cells. 6. The proportions of cells classified as simple or complex did not change with position in the visual field. 7. At all locations in the visual field, complex cells showed a higher percentage of binocularity than simple cells. 8. The proportions of two types of simple cells, I and II, and complex cells were variable between cortical layers. Layer IV contained predominantly simple II cells, whereas layer V contained predominantly complex cells. 9. The results are discussed in terms of visual perception and the dynamic pattern of visual stimulation around a moving animal, the optic flow field.

Functional organization of neurons.

Functional organization of neurons.