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A unified model for the combined temporal and spatial Broca-Sulzer effect.

A briefly pulsed light is brighter than a pulse of longer duration. For a brief flash of fixed duration and small area, enlarging a target results initially in an increase in brightness. Beyond some critical area, the target dims with further increases in size. These two phenomena are the temporal and the spatial Broca-Sulzer effect respectively. Each effect can be modeled using a generalization of the Hartline-Ratliff equation. The resulting analysis produces a mathematically unified treatment of both effects.

Humans

A model for processing of movement in the visual system.

Processing of spatio-temporal information in the human visual system has been investigated thoroughly during the past decade, but is still far from being properly understood. Moreover, the theory of separation of information by means of sustained and transient channels already at the retinal level is not satisfactory, as experimental results indicate that these two types of channels span a continuum of temporal characteristics. It is however obvious, that the process of pattern recognition and velocity perception calls for their separation at some level of the hierarchy. In this communication, we extend our model of three-dimensional spatio-temporal frequency expansion in the visual system (Gafni and Zeevi, 1977) to show how velocity-information extraction channels, sensitive to direction and velocity exclusively, can be formed by simple summation of signals from well-defined sets of channels representing points in the frequency space. Correspondence of these channels to characteristics of the cortical neurons is discussed.

Depth Perception

Studies on human finger tapping neural networks by phase transition curves.

The human finger tapping was studied psychologically by the phase transition curves. We assumed that some oscillatory neural network controls the tapping. One of our future works on the human finger tapping is to devise a method to change the magnitude of perturbation continuously in phase resetting experiments of a constant tapping interval with a same kind of task. If this is achieved, we can obtain a phase transition surface (i.e. the new phase as a function of the old phase and the magnitude of perturbation). From the shape of a phase transition surface, the intrinsic properties of the oscillatory network which controls the tapping can be studied (Kawato et al., 1978).

Conditioning, Psychological

Sensitivity variations in the visual system, contrast resolution and eye movements.

Attention is drawn to the fact that under normal visual conditions the sensitivity of the receptor units of the visual system are subject to spatial and temporal variations, and that consequently in performing pattern recognition the visual cortex has to discriminate between external luminance structure and internal sensitivity structure. It is suggested that eye movements are the method by which this discrimination is performed. In a simplified model analysis it is shown that eye movements are a suitable mechanism for this discrimination. Implications of this model for detection threshold and stabilized retinal images are discussed. A new interpretation of the adaptation to sine wave grids is given.

Eye Movements

Initial processing of visual information within the retina and the LGN.

The initial stage of information processing by the visual system reduces the information contained in the continuous image on the retina into a discrete set of responses which are carried from the lateral geniculate nucleus (LGN) to the visual cortex. -- 1. The optimal sampling of the light intensity distribution in the visual environment is achieved only if each channel in the visual pathways carries undistorted information corresponding to an image element. The visual system approaches as closely as possible the scheme of optimal spatial sampling, retaining the full information on the low spatial frequency content of the object light intensity. The ideal receptive field of a sustained LGN cell is then of the form J1(Kr)/Kr. -- 2. The experimentally determined receptive fields of sustained LGN cells (and to some extent retinal ganglion cells as well) in cat closely resemble the functional form J1(Kr)/Kr. The centre-surround organization of the receptive fields is therefore understood as a scheme which leads to a maximal information flow through the visual pathways. -- 3. The optimal sampling scheme cannot be realized by the retina alone, because of restrictions on the size of neural networks. It is therefore constructed in two stages, ending at the LGN level. A recombination of ganglion cell signals into optimal receptive fields is a major role of the LGN.

Animals

Form and function of cat retinal ganglion cells.

Recent explorations of the morphology of retinal neurones, combined with neurophysiological recordings have made it possible to link specific anatomical types with particular physiological classes. At the same time, the relatively complete anatomical mapping of the retina has revealed some bias in the sampling of neurones by electrophysiological techniques.

Animals

Models and mechanisms in speech perception. Species comparisons provide further contributions.

Results of recent experiments on the perception of speech-sound categories by nonhuman listeners are reviewed in light of current models of speech perception, and are compared to data obtained in similar experiments on human infants. In general, the data on nonhuman animals parallel those obtained from human infants, suggesting the possibility that certain auditory perceptual predispositions shared by mammals played a role in the selection of sounds for a speech-sound repertoire. The findings are generally relevant to the origins and evolution of speech and language, to theories of speech perception, and to the notion of innate predispositions for the perception of auditory signals that are part of an organism's communicative repertoire.

Animals

The neurobiological origins of psychoanalytic dream theory.

Freud built his model of the mind and his hypotheses about dreaming directly on the structure of his neurobiological model of the brain, which was developed in the "Project for a Scientific Psychology", written in 1895. Among the concepts modeled in this work were ego, somatic drives as motivationally critical, cathexes of psychic energy, wish fulfillment, and primary and secondary process. From the vantage point of more than 80 years later, the authors indicate the areas in which many of Freud's neurobiological assumptions are inacurrate. Revisions are needed in the neurobiologically derived psychoanalytic concepts, especially those of Freud's wish fulfillment-disguise theory of dreams.

Austria

The brain as a dream state generator: an activation-synthesis hypothesis of the dream process.

Recent research in the neurobiology of dreaming sleep provides new evidence for possible structural and functional substrates of formal aspects of the dream process. The data suggest that dreaming sleep is physiologically determined and shaped by a brain stem neuronal mechanism that can be modeled physiologically and mathematically. Formal features of the generator processes with strong implications for dream theory include periodicity and automaticity of forebrain activation, suggesting a preprogrammed neural basis for dream mentation in sleep; intense and sporadic activation of brain stem sensorimotor circuits including reticular, oculomotor, and vestibular neurons, possibly determining spatiotemporal aspects of dream imagery; and shifts in transmitter ratios, possibly accounting for dream amnesia. The authors suggest that the automatically activated forebrain synthesizes the dream by comparing information generated in specific brain stem circuits with information stored in memory.

Animals

[Spatial filtration in the nerve networks].

A simplified neuronal model leads to studies of multiunit nerve nets. Properties of spatial integration and differentiation are exhibited according to the structure of the interconnections. A spatial periodicity of nervous signal appears in nets with backward lateral inhibitions. It is a fundamental property of this structure.

Models, Neurological

A study of the central auditory processes in stutterers using the Synthetic Sentence Identification (SSI) Test battery.

The performance of a group of stutters (N = 14) and a group of nonstutterers (N = 14) was compared on the Synthetic Sentence Identification Test (Speaks and Jerger, 1965). The test is designed to assess central auditory function. It was hypothesized that because of subtle neurologically based differences in perceptual processing, the performance of the two groups would differ significantly on one or more of the subtests. An analysis of variance revealed that the performance of the stuttering group was significantly poorer (0.01 level of confidence) than that of the nonstutteres on the Ipsilateral Competing Message Subtest. The results of the investigation were compatible with other studies that suggest a neurological dysfunction within the central auditory apparatus as at least one of the underlying causes of disfluency. It was concluded that further investigations of the central auditory processes in stutterers are warranted to make a more definitive statement about the etiology of stuttering.

Adolescent

Aspects of carbohydrate metabolism in developing brain.

This review considers carbohydrate metabolism in the developing brain, in particular the proportion of glucose metabolized via the pentose phosphate pathway. Although small in amount, this fraction serves a vital rôle in some aspects of brain function. Evidence is presented that the pentose phosphate pathway subserves different functions as the developing brain progresses through the stages of growth and myelination to full neurological competence. The general aspects considered are the changing patterns of brain enzymes during development; the flux of glucose through the alternative pathways of glucose metabolism in the developing brain; the functional significance of the pentose phosphate pathway; and the regional and functional association of the pentose phosphate pathway activity and the detoxication of biogenic amínes.

Age Factors

Fetal signatures in the 3D genome of iPSC-derived neurons and their implications for disease modeling.

Induced pluripotent stem cells (iPSCs) have revolutionized neuroscience, providing an approach to generate patient-specific neurons for modeling of neurological diseases. However, it remains unclear how closely iPSC-derived neurons replicate the chromatin architecture of authentic brain neurons. Here, we uniformly processed newly generated Hi-C data from iPSC-derived neurons and neurons isolated from the human postmortem brain, together with previously published data sets comprising 228 human and 89 mouse Hi-C and snm3C-seq samples from different cell subtypes. These data were merged into 96 high-coverage contact maps used to examine chromatin features ranging from chromatin compartments and topologically associating domains (TADs) to chromatin loops, Polycomb-mediated contacts, and frequently interacting regions (FIREs). We find that iPSC-derived neurons largely retain the chromatin state of undifferentiated cells and resemble fetal rather than mature neurons. iPSC-derived neurons exhibit unusually strong compartmentalization, an enrichment of developmental genes at TAD borders, and a marked reduction of long-range repressive Polycomb-mediated contacts that typically silence early fetal programs. Although immature, iPSC-derived neurons offer advantages for modeling interactions between disease-associated SNPs and target genes, as many psychiatric disorders have neurodevelopmental origins. Integrating iPSC-derived and postmortem neuronal data sets therefore provides complementary insights into the chromatin landscape underlying disease-associated interactions. Our study offers a valuable Hi-C resource for the community and provides a detailed comparison of chromatin architecture throughout neuronal maturation, underscoring its importance for validating neuronal models and providing a robust framework for future studies.

Journal Article

On the neurology of perception.

The neurological base of biological space and of spatial perception is discussed. The nervous system is viewed as a system controlling behaviour. Movements as elements of behaviour are guided movements: goal-directed, programmed and ordered in space. Perceptual space is derived from directional properties of behaviour. The sense organs are not 'doors of perception', transparent to the alleged properties of the environment. Rather they are used in a centrifugal sense--outward from the organism. They are instrumental in updating a 'map' of the outside world and of the organisms as part of that world. The map is, in essence, a projection of the organism's own behaviour modified by the regularities, constraints and supports encountered in the world. The role of the periphery varies from moment to moment with the organisational level of behaviour. Thus, the sensomotor system is operated for updating the map and also for calibrating movements. At a peripheral level it helps to level out irregularities encountered in the execution of simple movements. All these functions may take place at the same time. Taken together, these considerations serve as an explanation of the fact that we are able to determine the spatial properties of objects although the shape as such is not presented to the sensory surface of the body, nor are the various scanpaths of our exploratory movements a replica of the geometrical properties of the object.

Animals