Formation of interzonal interaction of cortical fields during verbal-mental activity

Verbal activity as the higher psychic brain function is performed as a result of systemic interactions of many cerebral structures and processes at various levels of organization. It is shown in this work that based on analysis of spatial-temporal relations of EEG waves during performance by adult examinees of such verbal-mnestic tasks as mental count, listening of a rhyme and its recalling, tests for verbal fluency, and search for homonyms there is revealed an enhancement of diagonal connections between activities of posterior parts of the left hemisphere cortex and anterior parts of the right hemisphere cortex. During performance by the examinees of recognition of grammatical or semantic errors in sentences the interhemispheric interactions on the whole are also enhanced statistically significantly, but without domination of diagonal interactions. These data show that during performance by examinees of verbal tasks of analytical character there also are simultaneously actualized intercentral interactions related to the functional system responsible for recognition not only of verbal, but also of any other stimuli. In children with motor alalia and dysarthria, disturbances of distant EEG connections were revealed either in the left or in the right hemisphere with a simultaneous enhancement of ipsilateral interactions in symmetrical parts of the contralateral hemisphere. A special attention is paid to significance of the degree of formation of neurophysiological systems of the general cerebral integration for realization of the verbal function.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 40, No. 5, 2004, pp. 411–422.Original Russian Text Copyright © 2004 by Shepovalnikov, Tsitseroshin.To the 100-Anniversary of N. N. Traugott     

Systemic PCD occurs in TMV-tomato interaction

In hypersensitive response (HR), programmed cell death (PCD) is reported as a powerful defense mechanism in plant immune responses to pathogen. However, little is known about the PCD in systemic acquired resistance (SAR). Using tobacco mosaic virus (TMV) to infect the tomato (Lycopersicon esculentum cv. Jiafen 16) we found that localized TMV-infection could induce cell death in the uninoculated parts of the tomatoes, where the enzyme-linked immunosorbent assay (ELISA) showed no spreading virus. The biological and molecular characterization of this cell death was shown as following: chromatin condensed and formed peripheral conglomeration in nuclei; cell nucleus were TUNEL positive labeled; genomic DNA was fragmented and showed DNA laddering; mitochondria and chloroplast were disrupted; tonoplast and plasma membrane were shrunk and degradated. These results suggested that with an absence of TMV spread, the local TMV-infection on certain tomato leaves could induce systemic PCD in the root-tips, stem-apices and uninoculated leaves. The systemic PCD has various initiation and synchronization in such tissues and is distinct in inducement and exhibition from HR-PCD and SAR.     

Systemic PCD occurs in TMV-tomato interaction

In hypersensitive response (HR), programmed cell death (PCD) is reported as a powerful defense mechanism in plant immune responses to pathogen. However, little is known about the PCD in sys-temic acquired resistance (SAR). Using tobacco mosaic virus (TMV) to infect the tomato (Lycopersicon esculentum cv. Jiafen 16) we found that localized TMV-infection could induce cell death in the uninoculated parts of the tomatoes, where the enzyme-linked immunosorbent assay (ELISA) showed no spreading virus. The biological and molecular characterization of this cell death was shown as fol-lowing: chromatin condensed and formed peripheral conglomeration in nuclei; cell nucleus were TUNEL positive labeled; genomic DNA was fragmented and showed DNA laddering; mitochondria and chloroplast were disrupted; tonoplast and plasma membrane were shrunk and degradated. These re-sults suggested that with an absence of TMV spread, the local TMV-infection on certain tomato leaves could induce systemic PCD in the root-tips, stem-apices and uninoculated leaves. The systemic PCD has various initiation and synchronization in such tissues and is distinct in inducement and exhibition from HR-PCD and SAR.     

Activation of duration-sensitive auditory cortical fields in humans

The influence of stimulus duration on auditory evoked potentials (AEPs) was examined for tones varying randomly in duration, location, and frequency in an auditory selective attention task. Stimulus duration effects were isolated as duration difference waves by subtracting AEPs to short duration tones from AEPs to longer duration tones of identical location, frequency and rise time. This analysis revealed that AEP components generally increased in amplitude and decreased in latency with increments in signal duration, with evidence of longer temporal integration times for lower frequency tones. Different temporal integration functions were seen for different N1 subcomponents. The results suggest that different auditory cortical areas have different temporal integration times, and that these functions vary as a function of tone frequency.     

Receptive fields of auditory cortical neurons in the cat

Receptive fields of auditory cortical neurons were studied by electrical stimulation of nerve fibers in different parts of the cochlea in cats anesthetized with pentobarbital. The dimensions of the receptive fields were shown to depend on the topographic arrangement of the neuron in the auditory cortex. The more caudad the neuron on the cortical projection of the cochlea in the primary auditory cortex, the more extensive its receptive field. The receptive fields were narrowest in the basal turn of the cochlea and were symmetrical with respect to their center. It is suggested that the region of finest discrimination of acoustic stimuli in cats is located in the basal region of the cochlea, i.e., in that part of its receptor system which has the narrowest receptive field and is represented by significantly more (than the middle and apical regions of the cochlea) nerve cells in the primary auditory cortex [1].A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 5, pp. 467–473, September–October, 1981.     

Building better models of visual cortical receptive fields

Scientists usually study the receptive fields of visual cortical neurons by measuring responses to "optimal stimuli." In this issue of Neuron, Rust and colleagues have taken a promising alternative approach: build a receptive field model based on the cell responses to a stimulus subset and then use the model to predict responses to other stimuli.     

Effect of GP120 on glutathione peroxidase activity in cortical cultures and the interaction with steroid hormones

GP120 (the protein component of the HIV viral coat) is neurotoxic and may contribute to the cell loss associated with AIDS-related dementia. Previously, it has been shown in rat cortical mixed cultures that gp120 increased the accumulation of hydrogen peroxide and superoxide, two reactive oxygen species (ROS). We now demonstrate that gp120 increased activity of the key antioxidant glutathione peroxidase (GSPx), presumably as a defensive mechanism against the increased ROS load. Both estrogen and glucocorticoids (GCs), the adrenal steroid released during stress, blunted this gp120 effect on GSPx activity. The similar effects of estrogen and of GCs are superficially surprising, given prior demonstrations that GCs exacerbated and estrogens protected against gp120 neurotoxicity. We find that these similar effects of estrogen and GCs on GSPx regulation arose, in fact, from very different routes, which are commensurate with these prior reports. Specifically, estrogen has demonstrated antioxidant properties that may prevent the ROS increase (therefore acting as a neuroprotective agent) and rendered unnecessary the compensatory GSPx increased activity. To verify this we have added H2O2 to estrogen + gp120-treated cells, and GSPx activity was increased. However, with addition of H2O2 to GCs + gp120-treated cells there was no increase in activity. GCs appeared to decrease enzyme production and or activity and therefore under insult conditions ROS levels rose in the cell resulting in increased neurotoxicity. Overexpression of GSPx enzyme via herpes vector system reversed the GCs-induced loss of enzyme and eliminated the GCs exacerbation of gp120 neurotoxicity.     

Selective disruption of one Cartesian axis of cortical maps and receptive fields by deficiency in ephrin-As and structured activity

The topographic representation of visual space is preserved from retina to thalamus to cortex. We have previously shown that precise mapping of thalamocortical projections requires both molecular cues and structured retinal activity. To probe the interaction between these two mechanisms, we studied mice deficient in both ephrin-As and retinal waves. Functional and anatomical cortical maps in these mice were nearly abolished along the nasotemporal (azimuth) axis of the visual space. Both the structure of single-cell receptive fields and large-scale topography were severely distorted. These results demonstrate that ephrin-As and structured neuronal activity are two distinct pathways that mediate map formation in the visual cortex and together account almost completely for the formation of the azimuth map. Despite the dramatic disruption of azimuthal topography, the dorsoventral (elevation) map was relatively normal, indicating that the two axes of the cortical map are organized by separate mechanisms.     

Reductions in cortical activity during priming

Priming is a nonconscious form of memory in which an encounter with a stimulus influences the subsequent identification, production or classification of the same or a related stimulus. Neuroimaging studies have revealed that behavioral priming is typically accompanied by reduced activity in several cortical regions. We review recent studies that have concerned two key issues. First, specificity effects produced by changes between study and test in either the physical features of stimuli or the behavioral response reveal cortical sensitivity to the perceptual, conceptual and stimulus-to-decision mapping properties of primed items. Second, correlations between behavioral priming and activity reductions are robust across a range of tasks and procedures in prefrontal regions but not in posterior regions. On the basis of these recent studies, we suggest that the reduction in cortical activity during priming involves at least two different mechanisms.     

Coherent electromagnetic fields in the remote intercellular interaction

The distant interactions various organisms and their communities and the effect of coherent electromagnetic radiation on intercellular relations were studied. The ability of fruit crops male gametophyte to control the germination of pollen tube at the field level (nonchemical) was established. The cooperative character of this process is shown. It is stimulated directly or indirectly, by low-intensity coherent radiation through a bioinductor. The conclusion is made that spontaneous chemiluminescence cannot be considered as an information channel of distant intercellular interaction.     

Structural organization of receptive fields of lateral suprasylvian cortical neurons in cats

The substructural organization of receptive fields of lateral suprasylvian cortical neurons, sensitive to movement of visual stimuli, was investigated in cats. The experimental results showed that receptive fields of neurons in this cortical area, judging by responses to movement, consist mainly of cells with qualitatively different characteristics. With the unmasked method of presentation of a moving stimulus, a reduction in the amplitude of movement as a rule evoked a directional response of the cell, whereas with the masked method, and with the same amplitudes of movement, a nondirectional response appeared. The receptive fields of some neurons were particularly sensitive to movement of borders but did not respond to the body of the stimulus like receptive fields of neurons described in other visual structures. Heterogeneity of the substructural organization of receptive fields of lateral suprasylvian cortical neurons can be explained by convergence of inputs on the neuron and it is regarded as the basis of integrative mechanisms in this structure.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 17, No. 3, pp. 293–300, May–June, 1985.     

Electrical and mechanical fields orient cortical microtubules in higher plant tissues

Microtubules are a major component of the plant cytoskeleton. The factors which control the orientation of microtubules in plants are unknown. In this paper we describe preliminary findings that non-injurious electrical fields or mechanical fields, applied to pea roots, can cause a re-orientation of cortical microtubules which then lie in a plane approximately perpendicular to the direction of the applied field, within 6 hours. These results provide the first experimental evidence that physical fields can control the orientation of microtubules in plant tissues.     

Influence of strong static magnetic fields on primary cortical neurons

Intense uniform magnetic fields, such as those used in magnetic resonance imaging (MRI), are thought to exert little influence at the cellular level. Here we report modifications of the signaling cascades in rat cortical neurons cultured for 1 h in magnetic fields of up to 5 Tesla. The activation of c-Jun N-terminal kinase (JNK) increases monotonically with field strength, with a maximal activation of approximately 10% at 5 T, whereas the activation of extra cellular-regulated kinase (ERK) shows a maximum at 0.75 T ( approximately 10%). Since ERK is involved in cellular differentiation, these results indicate a magnetic induction of the signaling events associated with differentiation. However, the cells respond to further increases in field strength by evoking a stress response, since JNK is a stress-activated protein kinase. Three possible mechanisms are discussed and of these, the most plausible is magnetic field induced change in the membrane rest potential, a microscale magnetohydrodynamic effect. This mechanism most likely involves the activation of voltage dependent Ca(2+) channel opening; since intracellular Ca(2+) concentration was also found to be modified by the static magnetic field.     

Systemic effects of the interaction of an organism and microwaves

A study was made of the dynamics of neurophysiological processes, the autonomic nervous system reactions, and the behaviour of cats during long-term electromagnetic field (EMF) exposure (500 mu W/cm2, 2375 MHz). Revealed were the synchronization of the brain bioelectrical activity at 6-10 Hz and 12-16 Hz, different EMF sensitivity of the brain structures, the heart rate decrease, and the increase in the mobility and aggression of the animals. A complex of interrelated changes occurring virtually in all functional systems of the organism should be considered as a specific EMF effect.     

The mapping of cortical interaction in the asthenic neurosis syndrome]

Topographic mapping method was used to study the spatial-temporal organization of neocortical electrical activity at norm and asthenic neurosis. Patients with asthenic syndrome had shown right hemisphere dominance by the number of cortical interconnections in theta-band and interhemispheric discordance by coherence function.     

Rabbit visual cortical neurons with simple and complex receptive fields

Receptive fields of neurons of the rabbit visual cortex selective for stimulus orientation were investigated. These receptive fields were less well differentiated than those of the analogous neurons of the cat visual cortex (large in size and circular in shape). Two mechanisms of selectivity for stimulus orientation were observed: inhibition between on and off zones of the receptive field (sample type) and oriented lateral inhibition within the same zone of the receptive field (complex type). Lateral inhibition within the same zone of the receptive field also took place in unselective neurons; "complex" selective neurons differed from them in the orientation of this inhibition. A combination of both mechanisms was possible in the receptive field of the same neuron. It is suggested that both simple and complex receptive fields are derivatives of unselective receptive fields and that "complex" neurons are not the basis for a higher level of analysis of visual information than in "simple" neurons.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 13–21, January–February, 1978.