[Modulation of the functional activity of the acoustic and visual analyzers under conditions of listening to one's own EEG acoustic image of the temporal and occipital cortex areas]

Investigation into the functional activity of the acoustic and visual analyzer has been carried out before and after procedures of listening to one's own EEG of the temporal and occipital cortex areas. It has been shown, that there is a dependence of the dynamics of latent periods of sensomotor response to modality of stimuli and localization of source of the EEG acoustic image. After listening to acoustic image of the temporal EEG, a reduction of sensomotor reaction latency in the acoustic test has been observed. After listening to acoustic image of the occipital EEC, a reduction of sensomotor reaction latency in the visual test has been observed. In the control session after listening to A. Vivaldi's music, no significant shifts of sensomotor reaction latency have been observed. A conclusion has been made that, under conditions of local EEG-acoustic feedback, there is a selective elevation of functional activity of the brain areas used as the EEG-source for acoustic image forming.

How does our brain constitute defense mechanisms? First-person neuroscience and psychoanalysis

Current progress in the cognitive and affective neurosciences is constantly influencing the development of psychoanalytic theory and practice. However, despite the emerging dialogue between neuroscience and psychoanalysis, the neuronal processes underlying psychoanalytic constructs such as defense mechanisms remain unclear. One of the main problems in investigating the psychodynamic-neuronal relationship consists in systematically linking the individual contents of first-person subjective experience to third-person observation of neuronal states. We therefore introduced an appropriate methodological strategy, 'first-person neuroscience', which aims at developing methods for systematically linking first- and third-person data. The utility of first-person neuroscience can be demonstrated by the example of the defense mechanism of sensorimotor regression as paradigmatically observed in catatonia. Combined psychodynamic and imaging studies suggest that sensorimotor regression might be associated with dysfunction in the neural network including the orbitofrontal, the medial prefrontal and the premotor cortices. In general sensorimotor regression and other defense mechanisms are psychoanalytic constructs that are hypothesized to be complex emotional-cognitive constellations. In this paper we suggest that specific functional mechanisms which integrate neuronal activity across several brain regions (i.e. neuronal integration) are the physiological substrates of defense mechanisms. We conclude that first-person neuroscience could be an appropriate methodological strategy for opening the door to a better understanding of the neuronal processes of defense mechanisms and their modulation in psychoanalytic psychotherapy.

Insular cortex and neuropsychiatric disorders: A review of recent literature

The insular cortex is located in the centre of the cerebral hemisphere, having connections with the primary and secondary somatosensory areas, anterior cingulate cortex, amygdaloid body, prefrontal cortex, superior temporal gyrus, temporal pole, orbitofrontal cortex, frontal and parietal opercula, primary and association auditory cortices, visual association cortex, olfactory bulb, hippocampus, entorhinal cortex, and motor cortex. Accordingly, dense connections exist among insular cortex neurons. The insular cortex is involved in the processing of visceral sensory, visceral motor, vestibular, attention, pain, emotion, verbal, motor information, inputs related to music and eating, in addition to gustatory, olfactory, visual, auditory, and tactile data. In this article, the literature on the relationship between the insular cortex and neuropsychiatric disorders was summarized following a computer search of the Pub-Med database. Recent neuroimaging data, including voxel based morphometry, PET and fMRI, revealed that the insular cortex was involved in various neuropsychiatric diseases such as mood disorders, panic disorders, PTSD, obsessive-compulsive disorders, eating disorders, and schizophrenia. Investigations of functions and connections of the insular cortex suggest that sensory information including gustatory, olfactory, visual, auditory, and tactile inputs converge on the insular cortex, and that these multimodal sensory information may be integrated there.

A new model of sensorimotor coupling in the development of speech

We present a computational model that learns a coupling between motor parameters and their sensory consequences in vocal production during a babbling phase. Based on the coupling, preferred motor parameters and prototypically perceived sounds develop concurrently. Exposure to an ambient language modifies perception to coincide with the sounds from the language. The model develops motor mirror neurons that are active when an external sound is perceived. An extension to visual mirror neurons for oral gestures is suggested.

The processing of verbs and nouns in neural networks: insights from synthetic brain imaging

The paper presents a computational model of language in which linguistic abilities evolve in organisms that interact with an environment. Each individual's behavior is controlled by a neural network and we study the consequences in the network's internal functional organization of learning to process different classes of words. Agents are selected for reproduction according to their ability to manipulate objects and to understand nouns (objects' names) and verbs (manipulation tasks). The weights of the agents' neural networks are evolved using a genetic algorithm. Synthetic brain imaging techniques are then used to examine the functional organization of the neural networks. Results show that nouns produce more integrated neural activity in the sensory-processing hidden layer, while verbs produce more integrated synaptic activity in the layer where sensory information is integrated with proprioceptive input. Such findings are qualitatively compared with human brain imaging data that indicate that nouns activate more the posterior areas of the brain related to sensory and associative processing, while verbs activate more the anterior motor areas.

Spiking Phineas Gage: a neurocomputational theory of cognitive-affective integration in decision making

The authors present a neurological theory of how cognitive information and emotional information are integrated in the nucleus accumbens during effective decision making. They describe how the nucleus accumbens acts as a gateway to integrate cognitive information from the ventromedial prefrontal cortex and the hippocampus with emotional information from the amygdala. The authors have modeled this integration by a network of spiking artificial neurons organized into separate areas and used this computational model to simulate 2 kinds of cognitive-affective integration. The model simulates successful performance by people with normal cognitive-affective integration. The model also simulates the historical case of Phineas Gage as well as subsequent patients whose ability to make decisions became impeded by damage to the ventromedial prefrontal cortex.

Spontaneous eye movements in goldfish: oculomotor integrator performance, plasticity, and dependence on visual feedback

To quantify performance of the goldfish oculomotor neural integrator and determine its dependence on visual feedback, we measured the relationship between eye drift-velocity and position during spontaneous gaze fixations in the light and in the dark. In the light, drift-velocities were typically less than 1 deg/s, similar to those observed in humans. During brief periods in darkness, drift-velocities were only slightly larger, but showed greater variance. One hour in darkness degraded fixation-holding performance. These findings suggest that while visual feedback is not essential for online fixation stability, it may be used to tune the mechanism of persistent neural activity in the oculomotor integrator.

[Taurine effects on background impulse activity of the internal geniculate body neurons and mesencephalic inferior tubers of white rats]

Microelectrophysiological and computer techniques were used in the study of background impulse activity (BIA) of the internal geniculate body (IGB) neurons and mesencephalic inferior tubers (MIT) of white rats. Definite differences were found in BIA by regularity, dynamic types and modality of interimpulse histograms. Mean frequency of MIT neuron discharges was 16-17 Hz and was about 3 times higher than in neurons of the IGB. Intraperitoneal injection of taurin noticeably suppressed neuronal activity in both nuclei. The drug reduced mean frequency of background impulse discharges both in MIT and IGB. Thus, taurin produces primarily suppressing modulating effect on neuronal activity of IGB and MIT.

Representation of concurrent acoustic objects in primary auditory cortex

Auditory scene analysis involves the simultaneous grouping and parsing of acoustic data into separate mental representations (i.e., objects). Over two experiments, we examined the sequence of neural processes underlying concurrent sound segregation by means of recording of human middle latency auditory evoked responses. Participants were presented with complex sounds comprising several harmonics, one of which could be mistuned such that it was not an integer multiple of the fundamental frequency. In both experiments, Na (approximately 22 ms) and Pa (approximately 32 ms) waves were reliably generated for all classes of stimuli. For stimuli with a fundamental frequency of 200 Hz, the mean Pa amplitude was significantly larger when the third harmonic was mistuned by 16% of its original value, relative to when it was tuned. The enhanced Pa amplitude was related to an increased likelihood in reporting the presence of concurrent auditory objects. Our results are consistent with a low-level stage of auditory scene analysis in which acoustic properties such as mistuning act as preattentive segregation cues that can subsequently lead to the perception of multiple auditory objects.

The emergence of a shared action ontology: Building blocks for a theory

To have an ontology is to interpret a world. In this paper we argue that the brain, viewed as a representational system aimed at interpreting our world, possesses an ontology too. It creates primitives and makes existence assumptions. It decomposes target space in a way that exhibits a certain invariance, which in turn is functionally significant. We will investigate which are the functional regularities guiding this decomposition process, by answering to the following questions: What are the explicit and implicit assumptions about the structure of reality, which at the same time shape the causal profile of the brain's motor output and its representational deep structure, in particular of the conscious mind arising from it (its "phenomenal output")? How do they constrain high-level phenomena like conscious experience, the emergence of a first-person perspective, or social cognition? By reviewing a series of neuroscientific results and integrating them with a wider philosophical perspective, we will emphasize the contribution the motor system makes to this process. As it will be shown, the motor system constructs goals, actions, and intending selves as basic constituents of the world it interprets. It does so by assigning a single, unified causal role to them. Empirical evidence demonstrates that the brain models movements and action goals in terms of multimodal representations of organism-object-relations. Under a representationalist analysis, this process can be conceived of as an internal, dynamic representation of the intentionality-relation itself. We will show how such a complex form of representational content, once it is in place, can later function as a functional building block for social cognition and for a more complex, consciously experienced representation of the first-person perspective as well.

[Follow-up results of surgical correction of ocular ischemic syndrome]

The influence of surgeries in the carotid arteries produced on the visual functions and ocular blood circulation was studied in patients with ocular ischemic syndrome (OIS) during the remote postoperative period. A total of 180 patients with OIS (including 104 patients with an acute OIS clinical course and 76 patients with primary chronic clinical course) and with a pronounced stenosis of the carotid arteries were examined preoperatively and postoperatively within 1 or 2 years. A reliably improved visual acuity (preoperatively -0.37 +/- 0.05; and postoperatively -0.52 +/- 0.07; p < 0.01), positive dynamics in the electric sensitivity threshold and in a lability of the optic nerve were observed in patients with the acute OIS clinical course after reconstructive surgeries in the carotid arteries. An increase in contrast sensitivity of the visual analyzer was detected in 28.8% of patients with the acute clinical course and in 10.5% of patients with the chronic OIS clinical course. An improved blood circulation through the ocular artery was stated in patients of both groups. Reconstructive surgeries in the carotid arteries are most effective in correcting the acute OIS clinical variation.

Single trial fMRI reveals significant contralateral bias in responses to laser pain within thalamus and somatosensory cortices

Pain is processed in multiple brain areas, indicating the complexity of pain perception. The ability to locate pain plays a pivotal role in immediate defense and withdrawal behavior. However, how the brain localizes nociceptive information without additional information from somatotopically organized mechano-receptive pathways is not well understood. We used single-trial functional magnetic resonance imaging (fMRI) to assess hemodynamic responses to right and left painful stimulation. Thulium-YAG-(yttrium-aluminium-granate)-laser-evoked pain stimuli, without concomitant tactile component, were applied to either hand in a randomized order. A contralateral bias of the BOLD response was investigated to determine areas involved in the coding of the side of stimulation, which we observed in primary (SI) and secondary (SII) somatosensory cortex, insula, and the thalamus. This suggests that these structures provide spatial information of selective nociceptive stimuli. More importantly, this contralateral bias of activation allowed functionally segregated activations within the SII complex, the insula, and the thalamus. Only distinct subregions of the SII complex, the posterior insula and the lateral thalamus, but not the remaining SII complex, the anterior insula and the medial thalamus, showed a contralaterally biased representation of painful stimuli. This result supports the hypothesis that sensory-discriminative attributes of painful stimuli, such as those related to body side, are topospecifically represented within the forebrain projections of the nociceptive system and highlights the concept of functional segregation and specialization within these structures.

[Psychophysiological components of electrostimulation of the visual analyzer and their use to choose adequate parameters of therapeutic current]

The paper deals with search for signs or controllers of the adequacy of chosen visual analyzer electrostimulation (ES) parameters accessible for an outpatient physician. The subjective characteristics of phosphene-elementary visual sensation under the influence of electric current on the visual tract are identified; changes in the properties of phosphene in response to those of ES parameters were traced. The subjective characteristics of phosphene indirectly evaluates the degree of visual tract lesion and may serve as a controller of adequacy of ES parameters. The resultant algorithm of management of the properties of each identified characteristics of phoshene significantly enhances the efficiency of therapeutical ES.

[New possibilities of the use of space technologies in the treatment of children with injuries of the central nervous system]

The computerized stabilography was used to study the role of the visual analyzer (VA) in vertical posture acquisition and specifics of posture implementation by patients with craniocerebral injury (CCI) wearing suit Adele for dynamic proprioception correction (SDPC). Results of the investigation revealed a decreased vertical stability (VS) of CCI patients and a greater reliance on VA, which may be a compensatory instrument. Following the SDPC course, vertical stability was improved and the VA role in posture acquisition normalized suggesting alteration of the interanalyzer interaction in CCI patients owing to the treatment of proprioception impulsation.

[An historical-physiological analysis of the discussion between I. P. Pavlov and V. M. Bekhterev on the problems of localizing functions in the cerebral cortex]

This article is the first of the domestic publications on physiology and medical history, which highlights the discussion between I. P. Pavlov and V. M. Bekhterev on the issue of localization of functions in human cerebral cortex: it provides information of the visit by I. P. Pavlov to the clinic of V. M. Bekhterev; it discusses the role of V. M. Bekhrerev's students who described the cortex zones of tonotopics, gustation, regulation of salivation and stomach secretion, which I. P. Pavlov denied. Unlike articles on factography and history of physiology, which in various ways praise the scientists, this article is based of the modern approaches of medical history and scientific knowledge, in particular, it provides a retrospective of the major facts of the discussion.

[The methodology of the theory of self-organization in the development of concepts on the physiological mechanisms of vestibular reactions]

Sources of modern vestibulology's crisis status are determined. New methodological questions of object exploration of vestibular function and vestibular reactions are marked. New theoretical views are developed, some results of these theoretical views's practical realization are presented, perspective possibilities of new approach are defined.

[A comparative study of sun-protective glasses for locomotive team workers]

Solar flashes of 1500 to 9000 kd/m2 have been ascertained to have an adverse impact on the functional status of a visual analyzer. Comparing Russian and foreign sun-proof filters has indicated that a HC-9 neutral light-proof filter and a NIIOOIK film have the optimum light-protective properties, which may be recommended for use in the sun-proof glasses for locomotive workers.

Assessing the performance of neural encoding models in the presence of noise

An analytical method is introduced for evaluating the performance of neural encoding models. The method addresses a critical question that arises during the course of the development and validation of encoding models: is a given model near optimal in terms of its accuracy in predicting the stimulus-elicited responses of a neural system, or can the predictive accuracy be improved significantly by further model development? The evaluation method is based on a derivation of the minimum mean-square error between actual responses and modeled responses. It is formulated as a comparison between the mean-square error of the candidate model and the theoretical minimum mean-square error attainable through an optimal model for the system. However, no a priori information about the nature of the optimal model is required. The theoretically minimum error is determined solely from the coherence function between pairs of system responses to repeated presentations of the same dynamic stimulus. Thus, the performance of the candidate model is judged against the performance of an optimal model rather than against that of an arbitrarily assumed model. Using this method. we evaluated a linear model for neural encoding by mechanosensory cells in the cricket cercal system. At low stimulus intensities, the best-fit linear model of encoding by single cells was found to be nearly optimal, even though the coherence between stimulus-response pairs (a commonly used measure of system linearity) was low. In this low-stimulus-intensity regime, the mean square error of the linear model was on the order of the power of the cell responses. In contrast, at higher stimulus intensities the linear model was not an accurate representation of neural encoding. even though the stimulus-response coherence was substantially higher than in the low-intensity regime.

Brain viability and function analyzer: multiparametric real-time monitoring in neurosurgical patients

We have developed the Brain Viability (BVA) and Brain Function (BFA) Analyzers for monitoring the following parameters from the human cerebral cortex cerebral blood flow: (CBF), NADH redox state, Electro corticography (ECoG), brain temperature, extracellular K+, DC potential and intracranial pressure (ICP). The BVA monitors the first 4 parameters only. The Brain viability probe (BVP) and Brain function multiprobe (BFM) were used during 11 operations and in 18 ICU patients, respectively. Preliminary results from the OR showed that 5 patients exhibited a typical increase in CBF in response to changes in end-tidal CO2 without a significant change in the NADH redox state. In 4 other patients no changes in CBF and NADH were observed. Two patients exhibited a "steeling response", i.e., a decrease in CBF and an increase in NADH. In 18 comatose patients monitored in the ICU, the ICP, CBF and ECoG were measured correctly in most patients, whereas NADH and K+ were more problematic. One patient exhibited a typical response, may be due to repeated cortical spreading depression cycles and an ischemic depolarization event. Continuous realtime multiparametric monitoring in neurosurgical patients is feasible and practical in the OR and the ICU. The information provided could be used as a diagnostic tool to guide the procedures or treatment given to the patients.

[An electrophysiological evaluation of the role of the olfactory analyzer in brain integrative activity]

Summary electrical activity of olfactory bulb and amygdala of unrested rats with reversible anosmia during conditioning with application of light and odor as conditioned stimuli was studied. It was shown, that recovery of capacity for reception of odor wasn't connected with appearance in electrical activity of investigated structures of high-frequency high-amplitude components. Additional investigations of neuronal isolation of olfactory bulb and discovery of correlative changes of power of high-frequency components in dependency on level of common excitation give the possibility to consider this rhythm as one of the mechanisms of nonsensory modulator influences of olfactory analyser.

[Alternating signal speech audiometry in the diagnosis of central lesions of the acoustic analyzer]

Diagnostic sensitivity was compared for two binaural methods of "sensitized" speech audiometry--alternating speech audiometry (ASA) and Dichotic. A total of 35 patients were examined having neurosensory hypoacusis resultant from cerebrovascular atherosclerosis and chronic insufficiency of cerebral circulation. ASA indicated defects of the central parts of the acoustic analyzer in 80% of the examinees. The results of the two methods were similar in 85.7% of the patients. The diotic and dichotic alternating speech tests can be used separately and in combination in diagnosis of central acoustic disturbances, of vascular genesis, in particular.

Computation of inertial motion: neural strategies to resolve ambiguous otolith information

According to Einstein's equivalence principle, inertial accelerations during translational motion are physically indistinguishable from gravitational accelerations experienced during tilting movements. Nevertheless, despite ambiguous sensory representation of motion in primary otolith afferents, primate oculomotor responses are appropriately compensatory for the correct translational component of the head movement. The neural computational strategies used by the brain to discriminate the two and to reliably detect translational motion were investigated in the primate vestibulo-ocular system. The experimental protocols consisted of either lateral translations, roll tilts, or combined translation-tilt paradigms. Results using both steady-state sinusoidal and transient motion profiles in darkness or near target viewing demonstrated that semicircular canal signals are necessary sensory cues for the discrimination between different sources of linear acceleration. When the semicircular canals were inactivated, horizontal eye movements (appropriate for translational motion) could no longer be correlated with head translation. Instead, translational eye movements totally reflected the erroneous primary otolith afferent signals and were correlated with the resultant acceleration, regardless of whether it resulted from translation or tilt. Therefore, at least for frequencies in which the vestibulo-ocular reflex is important for gaze stabilization (>0.1 Hz), the oculomotor system discriminates between head translation and tilt primarily by sensory integration mechanisms rather than frequency segregation of otolith afferent information. Nonlinear neural computational schemes are proposed in which not only linear acceleration information from the otolith receptors but also angular velocity signals from the semicircular canals are simultaneously used by the brain to correctly estimate the source of linear acceleration and to elicit appropriate oculomotor responses.

Intensity coding of auditory stimuli: an fMRI study

The effect of stimulus intensity (sound pressure level, SPL) of auditory stimuli on the BOLD response in the auditory cortex was investigated in 14 young and healthy subjects, with no hearing abnormalities, using echo-planar, functional magnetic resonance imaging (fMRI) during a verbal and a non-verbal auditory discrimination task. The stimuli were presented block-wise at three different intensities: 95, 85 and 75 dB (SPL). All subjects showed fMRI signal increases in superior temporal gyrus (STG) covering primary and secondary auditory cortex. Most importantly, the spatial extent of the fMRI response in STG increased with increasing stimulus intensity. It is hypothesized that spreading of excitation is associated with the encoding of increasing stimulus intensity levels. In addition, we found bifrontal activation supposedly evoked by the auditory-articulary loop of working memory. The results presented here should assist in the design of optimal activation strategies for studying the auditory cortex with fMRI paradigms and may help in understanding intensity coding of auditory stimuli.

Intensity discrimination and auditory brainstem responses in cochlear implant and normal-hearing listeners

Intensity-discrimination limens (IDLs) and auditory brainstem responses (ABRs) were measured as a function of stimulus intensity in 6 cochlear implant (CI) and 8 normal-hearing (NH) listeners. Pulse-train stimuli were delivered electrically to the auditory nerve in CI listeners and acoustically in NH listeners. In CI listeners, the IDLs expressed as Weber fractions decreased monotonically with increasing intensity. In NH listeners, a nonmonotonic IDL function showing a peak a midintensities was observed. ABR wave amplitudes increased regularly with intensity only in CI listeners. Results support the notion that the slight decrease in Weber's fractions with increasing sound intensity--generally referred to as "the near-miss to Weber's law"--is subtended by retrocochlear processes, whereas the increase in Weber's fractions at midlevels--known as "the severe departure from Weber's law"--originates in cochlear mechanisms.

Contributions of the hippocampus, amygdala, and dorsal striatum to the response elicited by reward reduction

Rats were trained to run down a runway for either 1 or 10 food pellets. After training, those receiving 10 pellets were shifted to 1 pellet. Such shifts typically elicit a temporary decrease in running speed. Groups of normal rats and rats with bilateral lesions of the fimbria-fornix, lateral-basolateral complex of the amygdala, or dorsal striatum were tested with the shifted and unshifted procedures. Separate experiments, identical except for the intertrial intervals (ITIs; 3 min vs. 30 s), were carried out. The data are consistent with the view that an integrated action of multiple neural systems is required to observe the typical response to reward reduction in unlesioned rats. One system that includes the dorsal striatum promotes a reinforced approach response to the goal box. A neural system that includes fimbria-fornix is required to retain information about reduced reward over the 3-min ITI. A system that includes the amygdala may acquire a conditioned aversive response to the goal box after the shift is detected, leading to reduced speeds over testing.

Cue control and head direction cells

Previous research has shown that head direction (HD) cells in both the anterior dorsal thalamus (ADN) and the postsubiculum (PoS) in rats discharge in relation to familiar, visual landmarks in the environment. This study assessed whether PoS and ADN HD cells would be similarly responsive to nonvisual or unfamiliar environmental cues. After visual input was eliminated by blindfolding the rats, HD cells maintained direction-specific discharge, but their preferred firing directions became less stable. In addition, rotations of the behavioral apparatus indicated that some nonvisual cues (presumably tactile, olfactory, or both) exerted above chance stimulus control over a cell's preferred firing direction. However, a prominent auditory cue was not effective in exerting stimulus control over a cell's preferred direction. HD cell activity also was assessed after rotation of a novel visual cue exposed to the rat for 1, 3, or 8 min. An 8-min exposure was enough time for a novel visual cue to gain control over a cell's preferred direction, whereas an exposure of 1 or 3 min led to control in only about half the sessions. These latter results indicate that HD cells rely on a rapid learning mechanism to develop associations with landmark cues.

Taste responses in the greater superficial petrosal nerve: substantial sodium salt and amiloride sensitivities demonstrated in two rat strains

A great quantity of research has focused on neural responses of the chorda tympani nerve (CT) to taste stimuli. This report examined salt and sugar sensitivity of the greater superficial petrosal nerve (GSP) and the effect of amiloride on these neural responses. In addition to Sprague-Dawley (SD) rats that have CT responses typical of most rat strains, we included Fischer 344 (F344) rats whose CT responses to sodium chloride (NaCl) are higher than those of other strains. After a stimulation series in which water served as the rinse, a series of stimuli was presented in 100 microM amiloride. The GSP was highly responsive to NaCl, sodium acetate (NaAc), ammonium chloride, and sucrose; NaCl and NaAc responses were strongly suppressed by amiloride. Relative responses to NaCl were significantly higher in F344 than in SD rats. In summary, the GSP is highly sensitive to salt and sugar stimulation, and palatal taste receptors have a considerable degree of amiloride sensitivity.

Visual hemifield mapping using transcranial magnetic stimulation coregistered with cortical surfaces derived from magnetic resonance images

The perception of a visual stimulus can be inhibited by occipital transcranial magnetic stimulation. This visual suppression effect has been attributed to disruption in the cortical gray matter of primary visual cortex or in the fiber tracts leading to V1 from the thalamus. However, others have suggested that the visual suppression effect is caused by disruption in secondary visual cortex. Here the authors used a figure-eight coil, which produces a focal magnetic field, and a Quadropulse stimulator to produce visual suppression contralateral to the stimulated hemisphere in five normal volunteer subjects. The authors coregistered the stimulation sites with magnetic resonance images in these same subjects using optical digitization. The stimulation sites were mapped onto the surface of the occipital lobes in three-dimensional reconstructions of the cortical surface to show the distribution of the visual suppression effect. The results were consistent with disruption of secondary visual cortical areas.

Color selection and location selection in ERPs: differences, similarities and 'neural specificity'

It was hypothesized that color selection consists of two stages. The first stage represents a feature specific selection in neural populations specialized in processing color. The second stage constitutes feature non-specific selections, related to executive attentional processes and/or motor processes. This hypothesis was tested by investigating the effects of selectively attending to a specific color, location, or conjunction of location and color on the ERPs elicited by briefly flashed gratings. The gratings differed on three dimensions: color (red or blue), location in the visual field (4.4 degrees to the left or right of fixation) and form (target or non-target). Subjects had to respond to the presentation of target gratings in the attended category. Color selection was reflected in an enhanced parietal positivity in the 150-190 ms interval. Source analyses suggested that this color selection positivity might be generated in the basal occipital cortex, possibly human V4, an area of the brain specialized in color processing. The effect was separated from the P1 spatial attention effect both in topography and sources. Color selection was also reflected in a contralateral occipitotemporal negativity, which resembled the N1 spatial attention effect both in timing and topography. And finally, color selection was reflected in an N2b component. This N2b was similar in timing, topography and sources to the N2b's elicited by location selection and conjunction selection. We suggested that the N2b reflects feature non-specific selection processes, elicited by a range of attended stimuli, and possibly reflects activity in the anterior cingulate cortex. The NP80 was unaffected by attention to color and/or location and localized in striate cortex.

Comparison of ventral subicular and hippocampal neuron spatial firing patterns in complex and simplified environments

Activity from ventral subicular and hippocampal CA1 neurons was recorded in rats exploring a 4-arm radial maze in which the local and distal cues could be manipulated. Cells from both regions exhibited place fields, although ventral subicular neurons had larger fields than hippocampal cells. Rotation of the local and distal cues in opposite directions produced movement of the place fields in either direction or a complete change in firing pattern. Simplifying the environment also produced changes in place field location. Despite similarities between regions, subiculum fields decreased in size whereas hippocampal fields increased in the simple environment. These findings suggest that subicular cells may receive converging input from several hippocampal neurons and code more complex configurations of the cues.

[Contrast sensitivity in amblyopia, abiotrophy and optic nerve atrophy in children]

The threshold spatial contrast sensitivity was assessed in children with amblyopia, tapetoretinal abiotrophy, and partial atrophy of the optic nerve of different origin. The measurements were carried out at spatial frequencies of 0.5-22 cycle/grad. Tests with white, red, green, and blue arrays against a black background realized in the Zebra software for IBM computers with VGA or SVGA displays were carried out. Classification of curves representing the contrast sensitivity for the above conditions is proposed. Characteristics of the groups with the above diseases are described, based on the height, shape, and mutual position of the curves.

[The electrophysiological indices of the state of the different sections of the auditory analyzer in persons with a normal voice and with functional voice disorders]

Individuals with normal voice and patients with voice functional impairments undergone electrophysiological investigation of various parts of the hearing system, using tone audiometry, including the extended frequency band (10, 12, 14 and 16 kHz), as well as short- and long-latency acoustic evoked potentials (SLAEP and LLAEP). It was found out, that individuals with voice functional impairments had all of their hearing system's parts impaired to various extent, with more marked impairments in the central, rather than in the peripheral part of the hearing system. It was shown, that hearing at 4-8 kHz, as well as with the extended frequency band, especially at 14-16 kHz, time patterns of acoustic evoked potentials (latencies of waves III and V of SLAEP, the interpeak interval I-V, as well as the latency periods of the LLAEP components P2 and N2) could be useful in professional selection of individuals of voice and speech professions and for solving labor expertise matters. Of those individuals with normal voice but systematic vocal stress, 17.5% had impaired hearing at 14 and 16 kHz, as well as significant latency prolongation of the LLAEP wave N2 with tone stimulation at 1 and 4 kHz. Apparently, individuals of voice and speech professions should be referred to as the "risk" group. It may well be, that extended band audiometry and acoustic evoked potentials time patterns could be useful in determining the thresholds between the normality and pathology in voice dysfunctions.

[Objective assessment of the olfactory analyzer function based on recording of olfacto-vegetative and olfacto-vestibular reactions]

To register objectively olfactory defects and to assess them qualitatively and quantitatively, the authors propose to use olfactometric techniques reflecting olfactovegetative and olfactovestibular manifestations. Automatic pupillographic complex APK-OI provides speed, time and amplitude parameters of the pupillary and nyctating reflexes. 600 pupillograms and records of the nictation reflex proved high diagnostic significance of these methods. 104 stabilographic examinations (ST-02 unit) illustrated the changes in 12 vestibular parameters prior to and after olfactory impact. The results give grounds for application of olfactovestibular reactions registration as an objective olfactometric test.

Functional streams in occipito-frontal connections in the monkey

It is known that the prestriate cortical regions that project to area LIP in parietal cortex and to areas TEO and TE in temporal cortex are mostly separated. Two separate streams of information transfer from occipital cortex can this be distinguished. We wished to determine whether the parietal and temporal streams remain segregated in their projections to frontal cortex. Paired injections of retrograde fluorescent tracers were placed in parietal and temporal cortex, or in the lateral and medial parts of the frontal eye field (FEF). The cortical regions containing retrogradely labeled cells were reconstructed in two-dimensional maps. The results show that temporal cortex mainly projects to lateral FEF (area 45). Parietal cortex sends projections to medial FEF (area 8a) and to lateral FEF, as well as to area 46. Thus, the parietal and temporal streams converge in lateral FEF. Most of the occipital regions projecting to medial FEF are the same as those projecting to parietal cortex, whereas lateral FEF receives afferents from the same occipital regions as those sending projections to temporal cortex. Thus, one can distinguish two interconnected networks. One is associated with the inferotemporal cortex and includes areas of the ventral bank and fundus of the superior temporal sulcus (STS), lateral FEF and ventral prestriate cortex. This network emphasizes central vision, small accades and form recognition. The other network is linked to cortex of the intraparietal sulcus. It consists of areas of the upper bank and fundus of STS, medial FEF and dorsal prestriate cortex. These areas encode peripheral visual field and are active during large saccades.

On the specificity of neurons and visual areas

The dominant view during the past 40 years has been that the visual system analyzes the visual scene by breaking it down into basic attributes such as color, form, motion, depth and texture. Individual dedicated neurons and specific visual areas were believed to be devoted to the analysis of each of these attributes. Current research has challenged these views by emphasizing that neurons, especially in the cortex, have multifunctional properties and therefore serve as general-purpose analyzers rather than feature detectors. Consequently, it appears that most extrastriate visual areas, rather than each being devoted to the analysis of a specific basic visual attribute, perform several different tasks and thereby engage in more advanced and complex analyses than had been realized.

Cortical mechanisms for visual perception of object motion and position in space

The present review is aimed at analyzing and discussing some of the cortical mechanisms possibly involved in the perception of object motion and object localization in the visual field. A comprehensive approach to these topics would be beyond the scope of this work. The highest priority, therefore, will be given to the cortical machinery involved in these processes, while very little (or nothing at all) will be said on the possible role played by subcortical structures such as the lateral geniculate nucleus and the superior colliculus which, albeit not directly involved in perception, might contribute to it.

[A model for the study of the ototoxic effects of drugs in an experiment]

The authors compared sensitivity of the acoustic analyzer elements to ototoxic drugs in cat experiments. The model proposed assesses primary responses of the brain cortical acoustic zone (BCAZ) to sound stimulation. The drugs effect on the analyzer's periphery was determined from changes in bioelectric responses of the cochlea to sound stimulation (microphone potential, potential of the acoustic nerve action). The arguments are presented for feasibility of using primary BCAZ responses evoked by electric stimulation of thalamocortical radiation fibers coming from the medial geniculate body for examination of the drug effects on the analyzer's cortex. Parallel registration of the above bioelectrical reactions in the same animal for a long time makes it possible to compare sensitivity of different elements of the acoustic analyzer to ototoxic medication.

[The epiphysis in the visual analyzer system]

The brain gland epiphysis, participated in the regulation of the endocrine functions of mammals, is rudimentary third eye of lower vertebrates. In the process of evolution the gland has lost it own photoreceptor functions, but saved very close contacts with visual system. By means of it biologically active combinations and, first of all, melatonin hormone, the epiphysis support control over transmission of visual information and participate in realization of biological effects of light on organism.