Functional Assessment of Magno, Parvo and Konio-Cellular Pathways; Current State and Future Clinical Applications

The information generated by cone photoreceptors in the retina is compressed and transferred to higher processing centers through three distinct types of ganglion cells known as magno, parvo and konio cells. These ganglion cells, which travel from the retina to the lateral geniculate nucleus (LGN) and then to the primary visual cortex, have different structural and functional characteristics, and are organized in distinct layers in the LGN and the primary visual cortex. Magno cells are large, have thick axons and usually collect input from many retinal cells. Parvo cells are smaller, with fine axons and less myelin than mango cells. Konio cells are diverse small cells with wide fields of input consisting of different cells types. The three cellular pathways also differ in function. Magno cells respond rapidly to changing stimuli, while parvo cells need time to respond. The distinct patterns of structure and function in these cells have provided an opportunity for clinical assessment of their function. Functional assessment of these cells is currently used in the field of ophthalmology where frequency-doubling technology perimetry selectively assesses the function of magno cells. Evidence has accrued that the three pathways show characteristic patterns of malfunctions in multiple sclerosis, schizophrenia, Parkinson’s and Alzheimer’s diseases, and several other disorders. The combination of behavioral assessment with other techniques, such as event related potentials and functional magnetic resonance imaging, seems to bear promising future clinical applications

Neural correlates of boredom in music perception

Introduction: Music can elicit powerful emotional responses, the neural correlates of which have not been properly understood. An important aspect about the quality of any musical piece is its ability to elicit a sense of excitement in the listeners. In this study, we investigated the neural correlates of boredom evoked by music in human subjects. Methods: We used EEG recording in nine subjects while they were listening to total number of 10 short-length (83 sec) musical pieces with various boredom indices. Subjects evaluated boringness of musical pieces while their EEG was recording. Results: Using short time Fourier analysis, we found that beta2 rhythm was (16-20 Hz) significantly lower whenever the subjects rated the music as boring in comparison to nonboring. Discussion: The results demonstrate that the music modulates neural activity of various parts of the brain and can be measured using EEG

Nicotine Dependence Severity and Revised Reinforcement Sensitivity Theory: Assessing the Mediating Role of Risky Decision Making Using Path Analysis

Background: Gray’s revised Reinforcement Sensitivity Theory (r-RST) is a neuropsychologicalexplanation of personality that has been broadly used in substance use disorders. Although theBehavioral Approach System (BAS) is strongly related to nicotine dependence, findings inBehavioral Inhibition System (BIS) are controversial and there is little information about therole of the Fight/Flight/Freeze System (FFFS) in nicotine dependence. The purpose of thepresent study was to evaluate the mediating role of Risky Decision Making (RDM) in thisrelationship to clarify the controversy and fill the gap.Methods: The final sample of this correlation study comprised of 347 university students (age,Mean±SD 23.2±6.7) who completed two self-report measures, including the Fagerstrom TestFor Nicotine Dependence (FTND), Jackson-5 questionnaire of r-RST, and a computerizedIowa Gambling Task (IGT) to measure RDM. Pearson correlation and a path analysisframework were used to determine the simple, direct, and indirect effects of r-RST systems onnicotine dependence severity through RDM.Results: Using Amos, path analyses demonstrated significant direct and indirect effects ofBAS and FFFS/BIS on tobacco use. Also, the relationship between BAS/FFFS/BIS andtobacco use was shown to be mediated by RDM.Conclusion: It was demonstrated that the relationship among BAS /FFFS/BIS and tobaccouse can be partly explained using maladaptive RDM strategies, suggesting that decreasingreliance on decision-making in risky situations, while increasing the use of decision-makingskills educations in risky situations, and increasing the use of alternative sensation and funseeking by smoking and emotion regulation and mindfulness-based therapie

Longitudinal Effects of Bumetanide on Neuro-Cognitive Functioning in Drug-Resistant Epilepsy

Antiepileptic drugs (AEDs) have repeatedly shown inconsistent and almost contradictory effects on the neurocognitive system, from substantial impairments in processing speed to the noticeable improvement in working memory and executive functioning. Previous studies have provided a novel insight into the cognitive improvement by bumetanide as a potential antiepileptic drug. Through the current investigation, we evaluated the longitudinal effects of bumetanide, an NKCC1 co-transporter antagonist, on the brain microstructural organization as a probable underlying component for cognitive performance. Microstructure assessment was completed using SPM for the whole brain assay and Freesurfer/TRACULA for the automatic probabilistic tractography analysis. Primary cognitive operations including selective attention and processing speed, working memory capacity and spatial memory were evaluated in 12 patients with a confirmed diagnosis of refractory epilepsy. Participants treated with bumetanide (2 mg/ day) in two divided doses as an adjuvant therapy to their regular AEDs for 6 months, which followed by the re-assessment of their cognitive functions and microstructural organizations. Seizure frequency reduced in eight patients which accompanied by white matter reconstruction; fractional anisotropy (FA) increased in the cingulum-cingulate gyrus (CCG), anterior thalamic radiation (ATR), and temporal part of the superior longitudinal fasciculus (SLFt) in correlation with the clinical response. The voxel-based analysis in responder patients revealed increased FA in the left hippocampus, right cerebellum, and right medial temporal lobe, while mean diffusivity (MD) values reduced in the right occipital lobe and cerebellum. Microstructural changes in SLFt and ATR accompanied by a reduction in the error rate in the spatial memory test. These primary results have provided preliminary evidence for the effect of bumetanide on cognitive functioning through microstructural changes in patients with drug-resistant epilepsy

A Glance at Psychophysics Software Programs

Visual stimulation with precise control of stimulus has transformed the field of psychophysics since the introduction of personal computers. Luminance and chromatic features of stimulus, timing, and position of the stimulus are the main features that could be defined using programs written specifically for psychophysical experiments. In this manuscript, software used for the psychophysical experiments have been reviewed and evaluated for ease of use, license, popularity, and expandability

Efficiency of Information Coding in Various L/M Retinal Cone Ratios

Previous evidence has shown that the number of L and M cones in retina varies significantly between subjects. However, it is not clear how the variation of L/M ratio changes the behavioral performance of the subject. A model of transformation of data from retina to visual cortex for evaluation of various L/M cones ratios is presented. While L/M cone ratios close to 1 brings the best performance for one of postreceptoral (magnocellular) channels, we showed that the performance in the second channel (parvocells) will improve when the ratio furthers away from 1. Effects of different ratios of S were also explored

Psychophysical evidence for impaired Magno, Parvo, and Konio-cellular pathways in dyslexic children

Purpose: Dyslexia is one of the most common learning disabilities affecting millions of people worldwide. Although exact causes of dyslexia are not well-known, a deficit in the magnocellular pathway may play a role. We examined possible deficiency of magnocellular, as compared to parvocellular and koniocellular pathway function by measuring luminance and color perception. Methods: Visual stimuli consisted of a series of natural images, divided into layers of luminance, red-green and blue-yellow, which probed magnocellular, parvocellular, and koniocellular pathways, respectively. Thirteen children with dyslexia and 13 sex- and age- matched controls performed three psychophysical tasks. In the first task, subjects were instructed to match the contrast of luminance (magno) and red-green (parvo) images to that of the blue-yellow (konio) images. In the second task, subjects detected the isoluminant point of red-green images to probe parvocellular pathway. In the third task, temporal processing was assessed by measuring reaction time and percentage of correct responses in an identification task using four categories of images, activating all three pathways. Results: The dyslexic group had significantly elevated luminance and color contrast thresholds and higher isoluminant point ratio in comparison to the control group. Furthermore, they had significantly less correct responses than the control group for the blue-yellow images. Conclusion: We may suggest that dyslexic subjects might suffer from both magnocellular and parvocellular deficits. Moreover, our results show partial impairment of the koniocellular pathway. Thus, dyslexia might be associated with deficits in all three visual pathways