Goldfish's visual information processing patterns in food-reinforced discrimination learning between compound visual stimuli

Summary To examine how goldfish process and store information on compound visual stimuli, goldfish were trained with visual discriminative stimuli composed of varied colors and patterns using a Y-maze instrumental conditioning technique. The fish showed some very different types of information processing patterns depending upon the degree of discrimination difficulty of each constituent aspect (color and pattern). Those trained with compound stimuli with both a more easily discriminated aspect and a more difficult aspect learned the former selectively but did not learn the latter at all in spite of a high rate of training. Contrary to this, the fish trained with compound stimuli composed of two aspects with similar degrees of discrimination difficulty learned both aspects. In this case, only when fish were trained with compound stimuli composed of relatively more difficult aspects did they learn to discriminate between the stimuli more rapidly than the fish in each group trained with the constituent colored or patterned stimuli. These results were discussed in relation to visual processing patterns reported in other species and the mechanism of aspect selection.Abbreviations CP compound stimuli composed of VR and HB (7-mm ISBBs) - Cp compound stimuli composed of VR and HB (14-mm ISBBs) - cP compound stimuli composed of VG and HB (7-mm ISBBs) - cp compound stimuli composed of VG and HB (14-mm ISBBs) - HB horizontal patterns on blue background - HGra horizontal patterns on gray background - ISBBs interval spaces between bars - VG vertical patterns on green background - VGra vertical patterns on gray background - VR vertical patterns on red background     

Effect of noise in processing of visual information

Background

Information transmission and processing in the nervous system has stochastic nature. Multiple factors contribute to neuronal trial-to-trial variability. Noise and variations are introduced by the processes at the molecular and cellular level (thermal noise, channel current noise, membrane potential variations, biochemical and diffusion noise at synapses etc). The stochastic processes are affected by different physical (temperature, electromagnetic field) and chemical (drugs) factors. The aim of this study was experimental investigation of hypotheses that increase in the noise level in the brain affects processing of visual information. Change in the noise level was introduced by an external factor producing excess noise in the brain.

Methods

An exposure to 450 MHz low-frequency modulated microwave radiation was applied to generate excess noise. Such exposure has been shown to increase diffusion, alter membrane resting potential, gating variables and intracellular Calcium efflux. Nine healthy volunteers passed the experimental protocol at the lower (without microwave) and the higher (with microwave) noise level. Two photos (visual stimuli) of unfamiliar, young male faces were presented to the subjects, one picture after another. The task was to identify later the photos from a group of six photos and to decide in which order they were presented. Each subject had a total of eight sessions at the lower and eight at the higher noise level. Each session consisted of 50 trials; altogether a subject made 800 trials, 400 at the lower and 400 at the higher noise level. Student t-test was applied for statistical evaluation of the results.

Results

Correct recognition of both stimuli in the right order was better at the lower noise level. All the subjects under investigation showed higher numbers of right answers in trials at the lower noise level. Average number of correct answers from n=400 trials with microwave exposure was 50.3, without exposure 54.4, difference 7.5%, p<0.002. No difference between results at the lower and the higher noise level was revealed in the case of only partly correct or incorrect answers.

Conclusions

Our experimental results showed that introduced excess noise reduced significantly ability of the nervous system in correct processing of visual information.

     

Three processing characteristics of visual texture segmentation

Three mechanisms are outlined which are sufficient to determine texture segmentation or discrimination. They are: (1) convolution of detector profiles with the input image; (2) impletion, where the perceptual 'filling in' of the input surface occurs via a nonlinear filtering operation on each detector's output (3) grouping, where areas are segregated according to their differences in detector responses after impletion occurs. These mechanisms are compared with those proposed to occur in human visual texture discrimination.     

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.     

EEG correlates of the change in information processing strategy in visual imagery

Cnanger of the spatial organization of biopotentials (spatial synchronization and disorder, spectral power and coherence) were analyzed during mental creating of visual images from two simple elements: the angle the oblique line. With the transition from the first to the fourth task, the total number of used elements increased from the number suitable for simultaneous presentation and conscious processing (less than 7 +/- 2) to a much higher number. Changes in the characteristics of the spatial organization of biopotentials associated with the increase in the number of the elements can be explained by a change in the information processing strategy, transformation of information processing strategy, i.e. the transition from the left-hemispheric successive (conscious) analyses to the right-hemispheric simultaneous (unconscious) processing. It was shown that this change in the information processing strategy was accompanied by an increase in the index of spatial disorder sensitive to complicated nonlinear processes. Subjects were divided in two groups with different forms of the reorganization of interhemispheric and fronto-occipital relationships of biopotentials. These data are interpreted in terms of different involvement of the unconscious intellectual processes of different layers (subconsciousness and superconsciousness) in the change in information processing strategy.     

Bacterial chemotaxis: information processing,thermodynamics, and behavior

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Age-related specificity of the processing of visual information in the system of working memory

In adults and seven- to eight-year-old children, event-related potentials (ERPs) were analyzed during quiet observation and detailed paired comparison of visual stimuli. In both age groups, we showed the differences in the initial stages (component N1) of sensory analysis in these situations. In adults, an increase in the negativity during the initial stages of analysis was observed in the caudal and central areas of the cortex during presentation of standard and test stimuli. In the frontal areas of the cortex, an increase in the negative potential was observed only in ERPs induced by the test stimulus. In children, an increase in the negativity at the initial phases of analysis of stimuli in the situation of working memory, as compared to quiet observation, was confined to the caudal areas of the cortex. Differential curves that characterize analysis of standard and test stimuli showed age-related differences in the initial and late phases of information processing under the conditions of working memory. In adults, the differential curves that characterize analysis of the standard stimulus were represented by negative phases, and the curves related to the test stimulus, by positive phases. In children, late phases of analysis of the standard and test stimuli had smaller differences as compared to adults: the late positive wave was predominant in the responses to both standard and test stimulus in the caudal areas of the cortex. In the frontal areas, there was no considerable increase in the amplitude of the late positive wave in response to the test stimulus. This fact, together with the absence of enhancement of initial negativity in the frontal areas, which reflects analysis of the test stimulus, indicates that the prefrontal cortex plays a smaller role in the comparison of the memory trace with the current information in seven- to eight-year-old children. The data obtained suggest that the central executive of working memory is not sufficiently mature in children aged seven to eight years.     

A contribution of synaptic plasticity in the basal ganglia to processing of visual information

The mechanism of involvement of the basal ganglia in processing of visual information on the basis of dopamine-dependent modulation of efficacy of synaptic transmission in interconnected parallel associative and limbic loops (cortex--basal ganglia--thalamus--cortex) is proposed. Each loop consists of one of the visual or prefrontal cortical areas connected with the thalamic nucleus and corresponding loci in different nuclei of the basal ganglia. Circulation of activity in such a loop provides reentrance of information into the thalamus and neocortex. Dopamine releasing in response to a visual stimulus oppositely modulates the efficacy of "strong" and "weak" corticostriatal inputs. Subsequent reorganization of activity in the loop leads to a disinhibition (inhibition) of activity of those cortical neurons that were "strongly" ("weakly)" excited by the visual stimulus simultaneously with activation of dopaminergic cells. A selected neuronal pattern in each cortical area represents a property of the visual stimulus processed by this area. Excitation of dopaminergic cells by the visual stimulus via the superior colliculi requires parallel activation of a disinhibitory input to the superior colliculi via the thalamus and a "direct" pathway through the basal ganglia. The prefrontal cortex excited by the visual stimulus via the mediodorsal thalamic nucleus performs a top-down control over the dopaminergic cell activity, supervising simultaneous dopamine release in different striatal loci and thus promotes the interconnected selection of neuronal representations of individual properties of the visual stimulus and their binding in an integrated image.     

Focus, newness and their combination: processing of information structure in discourse

The relationship between focus and new information has been unclear despite being the subject of several information structure studies. Here, we report an eye-tracking experiment that explored the relationship between them in on-line discourse processing in Chinese reading. Focus was marked by the Chinese focus-particle "shi", which is equivalent to the cleft structure "it was… who…" in English. New information was defined as the target word that was not present in previous contexts. Our results show that, in the target region, focused information was processed more quickly than non-focused information, while new information was processed more slowly than given information. These results reveal differences in processing patterns between focus and newness, and suggest that they are different concepts that relate to different aspects of cognitive processing. In addition, the effect of new/given information occurred in the post-target region for the focus condition, but not for the non-focus condition, suggesting a complex relationship between focus and newness in the discourse integration stage.     

Relation between the process of information processing during learning and the level of motivation

Adaptive behaviour of 58 male mice of BALB/c line was studied (10 experimental sessions) in a multialternative maze (180 positive decisions) at various levels of alimentary excitation, after 0--12--24--36 hours of starvation. It has been found that such characteristics of the brain integrative activity as power, speed and rate of the development of motor information processing (estimated by dynamics of formation of correct decisions) are in direct dependency on the level of alimentary excitation. The suggestion is discussed that the level of concrete physiological neens represents both an "energiator" of the brain activity and its directing and organizing determinant.     

Facilitation, competition, and vegetation patchiness: from scale free distribution to patterns

A new technique for the modeling of perennial vegetation patchiness in the arid/semiarid climatic zone is suggested. Incorporating the stochasticity that affects life history of seedlings and the deterministic dynamics of soil moisture and biomass, this model is flexible enough to yield qualitatively different forms of spatial organization. In the facilitation-dominated regime, scale free distribution of patch sizes is observed, in correspondence with recent field studies. In the competition controlled case, on the other hand, power-law statistics is valid up to a cutoff, and an intrinsic length scale appears.