Learning complex texture discrimination.

Higher-order spatial correlations contribute strongly to visual structure and salience, and are common in the natural environment. One method for studying this structure has been through the use of highly controlled texture patterns whose obvious structure is defined entirely by third- and higher-order correlations. Here we examine the effects that longer-term training has on discrimination of 17 such texture types. Training took place in 14 sessions over 42 days. Discrimination performance increased at different rates for different textures. The time required to complete a visit reduced by 25.4% (p=0.0004). Factor analysis was applied to data from the learning and experienced phases of the experiment. This indicated that the gain in speed was accompanied by an increase in the number of mechanisms contributing to discrimination. Learning was not affected by sleep quality but was affected by extreme tiredness (p<0.01). The improved discrimination and speed were retained for 2.5 months. Overall, the effects were consistent with perceptual learning. The observed learning is likely related to the adaptation of innate mechanisms that underlie our ability to identify nonredundant, visually salient structure in natural images. It may involve cortical V2 and appears to involve increased strength, speed, and breadth of connections within our internal representation of this complex perceptual space.

Seizure incidence among neuromyelitis optica spectrum disorder patients.

BACKGROUND: Neuromyelitis optica spectrum disorders (NMOSDs) are a group of neuroinflammatory diseases, which mainly affect the optic nerve and spinal cord. NMOSD is an astrocytic channelopathy involving the aquaporin-4 (AQP4) water channels in the central nervous system. Patients can present with seizure attacks as a first manifestation or relapse. However, compared with multiple sclerosis (MS) or myelin oligodendrocyte glycoprotein encephalomyelitis (MOG-EM), seizure attacks are less frequent in NMOSD. METHODS: In this study, we aimed to find out the incidence of seizure attacks during the disease course of 137 NMOSD patients who were registered in our centre from January 2011 till January 2020. Furthermore, we reviewed the literature for NMOSD cases with seizure attacks during their follow-up, in order to investigate the reason for this low incidence of seizures. RESULTS: Only one of our patients (0.72%) experienced an episode of generalised tonic-clonic seizure during his follow-up. CONCLUSION: Reviewing the literature revealed that although seizures are rare in NMOSD, AQP4 disruption possibly increases the risk of seizure attacks. We therefore concluded that the role of AQP4 in seizures is controversial and needs more investigation.

The higher prevalence of multiple sclerosis among Iranian Georgians; new clues to the role of genetic factors.

BACKGROUND: Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) with varied prevalence rates among populations with different ethnic backgrounds. Therefore, studies done on minorities have shed more light on the risk factors. OBJECTIVE: Comparing MS prevalence in Georgian-based population immigrated to Iran and other Iranians. METHODS: All records of MS patients enrolled in the two biggest registry systems were investigated. All of the patients born in Fereydunshahr and Buin va Miandasht (2 biggest cities with Georgian immigrants) were interviewed and their baseline characteristics were obtained. Patients' ethnic background information were obtained from the Iran National organization for civil registration. RESULTS: Forty-one patients from Fereydunshahr and Buin va Miandasht were identified. The population of the two cities combined and the estimated number of Georgian-based patients in both cities were reported 59817 and 12000, respectively. The estimated ethnicity-adjusted prevalence among the Georgian-based individuals was 2.3 times higher than the non-Georgian ones. Baseline characteristics were also compared. CONCLUSION: There was a higher prevalence of multiple sclerosis among the Georgian minority of Isfahan. Due to the ethnic background of the Georgian minority, genetic risk factors should be considered more as a risk factor.