Unilateral Resection of Both Cortical Visual Pathways Alters Action but not Perception

The human cortical visual system consists of two major pathways, a ventral pathway that subserves perception and a dorsal pathway that subserves visuomotor control. These pathways follow dissociable developmental trajectories, and, accordingly, might be differentially susceptible to neurodevelopmental disorders or injuries. Previous studies have found that children with cortical resections of the ventral visual pathway retain largely normal visuoperceptual abilities. Whether visually guided actions, supported by computations carried out by the dorsal pathway, follow a similar pattern remains unknown. To address this question, we examined visuoperceptual and visuomotor behaviors in a pediatric patient, TC, who underwent a cortical resection that included portions of the left ventral and dorsal pathways. We collected data when TC used her right and left hands to perceptually estimate the width blocks that varied in width and length, and, separately, to grasp the same blocks. Her perceptual estimation performance was comparable to that of controls, independent of the hand used. In contrast, relative to controls, she showed reduced visuomotor sensitivity to object shape and this was more evident when she grasped the objects with her contralesional right hand. These results provide evidence for a striking difference in the reorganization profiles of the two visual pathways. This difference supports the notion that the two pathways exhibit differential susceptibility to neurodevelopmental disorders.

Bump attractor dynamics underlying stimulus integration in perceptual estimation tasks

Perceptual decision and continuous stimulus estimation tasks involve making judgments based on accumulated sensory evidence. Network models of evidence integration usually rely on competition between neural populations each encoding a discrete categorical choice. By design, these models do not maintain information of the integrated stimulus (e.g. the average stimulus direction in degrees) that is necessary for a continuous perceptual judgement. Here, we show that the continuous ring attractor network can integrate a stimulus feature such as orientation and track the stimulus average in the phase of its activity bump. We reduced the network dynamics of the ring model to a two-dimensional equation for the amplitude and the phase of the bump. Interestingly, these reduced equations are nearly identical to an optimal integration process for computing the running average of the stimulus orientation. They differ only in the intrinsic dynamics of the amplitude, which affects the temporal weighting of the sensory evidence. Whether the network shows early (primacy), uniform or late (recency) weighting depends on the relative strength of sensory stimuli compared to the amplitude of the bump and on the initial state of the network. The specific relation between the internal network dynamics and the sensory inputs can be modulated by changing a single parameter of the model, the global excitatory drive. We show that this can account for the heterogeneity of temporal weighting profiles observed in humans integrating a stream of oriented stimulus frames. Our findings point to continuous attractor dynamics as a plausible mechanism underlying stimulus integration in perceptual estimation tasks.

Perceptual Estimation of Diffuse White Level in HDR Images

Diffuse white is an important concept in all color appearance models. However, there is a lack of research directly about the perceived diffuse white in HDR images. Three experiments were conducted to explore the perceptual estimation of diffuse white in real HDR images when presented on displays. The first experiment showed that the perceptual estimation of diffuse white relied more on the image content than the clipped peak luminance levels. Experiment II used images with different neutral density filters rather than clipping. The normalized luminance levels of the perceptual estimation were similar, depending on image content but not on image absolute luminance levels. Moreover, in both experiments, no significant difference can be found between expert and naive observers. The variance across images agreed with each other between experiment I and II. However, both results demonstrated that the absolute luminance level of observers' estimation is higher than the calibrated diffuse white level. Experiment III focused on exploring the impact of measurement methodologies on the absolute luminance level of the estimated diffuse white. Results of experiment III verified that the absolute luminance level of the perceptual estimation can be manipulated by the measurement methodology but the variance across image content is stable.

Statistical Method of Processing the Results of Experimental Research of Polycode-Polymodal Text Influence on Audience (Using the Example of Regional Televigion Sports Coverage)

This article analyzes the description of the procedure of statistical processing of the obtained experimental data of polycode-polymodal texts influence on audience. As examples of such complicated texts were taken sports coverages aired on television covering the Republic of Bashkortostan. Sports coverages are polycode-polymodal texts as they combine components belonging to different sign systems in one text and this information is percepted by audience with the help of two channels: visual and audial. In our research the audience was represented by the first-year and secondyear students of Ufa State Aviation Technical University. Their task was to estimate 100 television sport coverages using the scale offered. Because of technical reasons 10 sports coverages were analyzed with the usage of STATISTICA Version 6, Statsoft program. We received the following results. The audial perceptual channel is suggested to be leading as audience’s total perceptual estimation was influenced by reporter’s speech quality (presence or absence speech defects) the most.

Distributed neural replay of decision confidence mediates informational conformity

We occasionally receive conflicting views from others. To maximize accuracy, we should exercise informational conformity by changing our mind proportional to our confidence about our initial view. This account predicts that neural correlates of confidence in the private decision should be replayed as the private and social information are integrated. In a perceptual estimation task (N=120), influence from others was proportional to private confidence. Human fMRI (N=20) showed that consistent with the replay hypothesis, confidence covaried with temporally distributed activity during private estimate (Precuneus and dorsal anterior cingulate cortex, dACC), social change of mind (dACC) and social outcome (dorsolateral prefrontal cortex and dACC). During social change of mind and only when paired with alleged human (but not with computer) partners, left temproparietal junction carried information about participants’ social use of confidence. Our study reveals the neuronal substrates of the role of confidence in computational implementation of informational conformity.

An Improved Logistic Function for Mapping Raw Scores of Perceptual Evaluation of Speech Quality (PESQ)

Voice service being the major offering of telecommunication networks, its level of Quality of Service (QoS) largely determines the performance of these networks. This work evaluated the state-of-the-art Perceptual Evaluation of Speech Quality (PESQ) objective model for perceptual estimation of the quality of transmitted speech signals. Perceptual estimation of the quality of speech is predominantly done by subjective techniques and the results presented as Mean Opinion Scores (MOS), which has a scale from 1 for poor quality to 5 for excellent quality. Despite constraints of the subjective approach to perceptual speech quality estimation, its scores serves as the basis for correlating quality scores from objective techniques for speech quality estimation. Original or reference speeches were recorded using professional studio equipment and software, and guided by provisions of ITU-T P.830. The speeches were transmitted over three mobile wireless networks. A speech database consisting of 64 original (32 male and 32 female) and 192 transmitted speeches was developed. Reference speeches and their corresponding transmitted (network-degraded) speeches were tested on the PESQ model to estimate their quality scores. The raw PESQ quality scores are within the scale range of -0.5 and 4.5. They were mapped to the MOS scale for linear comparison of the scales. Study of PESQ model showed several shortcomings, some of which have been improved upon by previous researchers. Evaluating PESQ mapping function (in ITU-T Rec P.862.1) showed the need for better coverage of the MOS scale. Analysis of solution for the logistic growth function was done and parameters were optimised which resulted in the development of a new robust logistic mapping function. The raw PESQ quality scores were mapped using the developed mapping function as well as two known standard mapping functions, namely: ITU-T P.862.1 and Morfitt and Cotanis mapping functions. The mapped scores known as PESQ MOS-listening quality objective (PESQ MOS-LQO) obtained with the three functions were tested using ANOVA at a significant figure of . The developed logistic mapping function offered a quality score coverage of 98.6% of the MOS scale. This was evaluated against the two known standard mapping functions and the developed function offered improvement of 11.8 and 4.9% over and above their 86.8 and 93.7% coverage of the MOS scale respectively. At the significance level of , an F-value of 60.6042, a critical-F of 3.04, and a p-value of 4.61721E-21 were obtained. With p < 0.05, the Null Hypothesis was rejected, and the critical-F value being less than the F-statistic value confirmed the rejection. Therefore, the data distribution of at least one of the functions has a different mean and belongs to a separate population of performance.