Sex and stress hormone dysregulation as clinical manifestations of hypothalamic function in migraine disorder: A meta-analysis.

Migraine is a leading cause of disability in young adults. It occurs more frequently in females, often comorbidly with stress disorders, suggesting an association with hypothalamic sex and stress hormonal function and a likely interaction with autonomic nervous system activation. Thus, this study aimed to meta-analyse current literature pertaining to female and male sex hormones (estrogen, progesterone and testosterone concentration), hypothalamic-pituitary-adrenal axis (HPA axis) cortisol responses and heart rate variability (HRV) in migraineurs and controls aged 13-65 years. A systematic search of MEDLINE, Embase, PsycINFO, PubMed, CINAHL and Web of Science databases on 29/08/2022 identified 29 studies for meta-analysis (encompassing 719 migraineur and 592 control participants) that met inclusion and NHLBI risk of bias criteria. Results demonstrated that estrogen concentrations of female migraineurs were reduced (g = -.60, 95% CI [-.91, -.29], p < .001) in the luteal phase of the menstrual cycle, compared to controls. No differences were found in progesterone levels overall in female migraineurs, nor in testosterone levels in male migraineurs compared to controls. Further, early diurnal cortisol concentrations were elevated (g = .32, 95% CI [.00, .63], p = .036) in female and male migraineurs compared to controls, though no differences were found in HRV of female or male migraineurs compared to controls. These findings of dysregulation of estrogen in females and cortisol dysregulation in female and male migraineurs indicate perturbed hypothalamic function and highlight the association of migraine with stress and the need for further rigorous investigation of hypothalamic neuroendocrine functions in migraineurs of both sexes.

Comparison of Tiling Artifact Removal Methods in Secondary Ion Mass Spectrometry Images.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging is used across many fields for the atomic and molecular characterization of surfaces, with both high sensitivity and high spatial resolution. When large analysis areas are required, standard ToF-SIMS instruments allow for the acquisition of adjoining tiles, which are acquired by rastering the primary ion beam. For such large area scans, tiling artifacts are a ubiquitous challenge, manifesting as intensity gradients across each tile and/or sudden changes in intensity between tiles. Such artifacts are thought to be related to a combination of sample charging, local detector sensitivity issues, and misalignment of the primary ion gun, among other instrumental factors. In this work, we investigated six different computational tiling artifact removal methods: tensor decomposition, multiplicative linear correction, linear discriminant analysis, seamless stitching, simple averaging, and simple interpolating. To ensure robustness in the study, we applied these methods to three hyperspectral ToF-SIMS data sets and one OrbiTrapSIMS data set. Our study includes a carefully designed statistical analysis and a quantitative survey that subjectively assessed the quality of the various methods employed. Our results demonstrate that while certain methods are useful and preferred more often, no one particular approach can be considered universally acceptable and that the effectiveness of the artifact removal method is strongly dependent on the particulars of the data set analyzed. As examples, the multiplicative linear correction and seamless stitching methods tended to score more highly on the subjective survey; however, for some data sets, this led to the introduction of new artifacts. In contrast, simple averaging and interpolation methods scored subjectively poorly on the biological data set, but more highly on the microarray data sets. We discuss and explore these findings in depth and present general recommendations given our findings to conclude the work.

Visual Processing During the Interictal Period Between Migraines: A Meta-Analysis.

Migraine is a poorly understood neurological disorder and a leading cause of disability in young adults, particularly women. Migraines are characterized by recurring episodes of severe pulsating unilateral headache and usually visual symptoms. Currently there is some disagreement in the electrophysiological literature regarding the universality of all migraineurs exhibiting physiological visual impairments also during interictal periods (i.e., the symptom free period between migraines). Thus, this meta-analysis investigated the evidence for altered visual function as measured electrophysiologically via pattern-reversal visual evoked potential (VEP) amplitudes and habituation in adult migraineurs with or without visual aura and controls in the interictal period. Twenty-three studies were selected for random effects meta-analysis which demonstrated slightly diminished VEP amplitudes in the early fast conducting P100 component but not in N135, and substantially reduced habituation in the P100 and the N135 in migraineurs with and without visual aura symptoms compared to controls. No statistical differences were found between migraineurs with and without aura, possibly due to inadequate studies. Overall, insufficient published data and substantial heterogeneity between studies was observed for all latency components of pattern-reversal VEP, highlighting the need for further electrophysiological experimentation and more targeted temporal analysis of visual function, in episodic migraineurs.

A Role for Visual Memory in Vocabulary Development: A Systematic Review and Meta-Analysis.

Although attention and early associative learning in preverbal children is predominantly driven by rapid eye-movements in response to moving visual stimuli and sounds/words (e.g., associating the word "bottle" with the object), the literature examining the role of visual attention and memory in ongoing vocabulary development across childhood is limited. Thus, this systematic review and meta-analysis examined the association between visual memory and vocabulary development, including moderators such as age and task selection, in neurotypical children aged 2-to-12 years, from the brain-based perspective of cognitive neuroscience. Visual memory tasks were classified according to the visual characteristics of the stimuli and the neural networks known to preferentially process such information, including consideration of the distinction between the ventral visual stream (processing more static visuo-perceptual details, such as form or colour) and the more dynamic dorsal visual stream (processing spatial temporal action-driven information). Final classifications included spatio-temporal span tasks, visuo-perceptual or spatial concurrent array tasks, and executive judgment tasks. Visuo-perceptual concurrent array tasks, reliant on ventral stream processing, were moderately associated with vocabulary, while tasks measuring spatio-temporal spans, associated with dorsal stream processing, and executive judgment tasks (central executive), showed only weak correlations with vocabulary. These findings have important implications for health professionals and researchers interested in language, as they advocate for the development of more targeted language learning interventions that include specific and relevant aspects of visual processing and memory, such as ventral stream visuo-perceptual details (i.e., shape or colour).

An x-ray microanalytical method for measuring in vivo element and water concentrations, relating to osmoregulation, in cells and tissues of the posterior eye.

Osmoregulation is critical for cell and tissue survival yet there are relatively few methods available to determine osmotic gradients from water and elemental concentration either in single cells or across multiple cellular layers of tissue. X-ray microanalysis of frozen-hydrated preparations in a scanning electron microscope is one such powerful, sensitive, nondestructive technique. Here we use x-ray microanalysis to quantitatively analyse intracellular element concentrations and oxygen concentrations, as a proxy for water concentrations, in selected individual cells of the posterior eye. Using frozen-hydrated preparations of the retinal complex of chicken eyes, it is shown that structural preservation is sufficient to identify cell layers and individual cells. The quantitative analysis of selected areas in the photoreceptor layer, inner nuclear layer and ganglion cell layer, where specific cell types were known to be present, provided measurements of intracellular element concentrations comparable with the analysis of individual cells. It is also shown that in the cells of the retinal pigment epithelium and outer photoreceptor segments elemental analyses were reasonably consistent at the cellular level in different depth levels of the same sample. Comparison of oxygen concentrations, as a proxy for water concentration, at two accelerating voltages (15 and 5 kV) indicated that at 15 kV oxygen concentration was largely derived from intracellular water. Water concentrations could be calculated and concentrations of diffusible elements (Na, K) could be defined in mmol/L. From the latter it is possible to calculate osmotic concentrations of individual cells and osmotic gradients across the tissue. LAY DESCRIPTION: Understanding many cellular processes, in both healthy and diseased states, depends on knowing how the water content of cells and their surrounding fluids is controlled. The transport of water is generally down its concentration gradient or against the osmotic concentration gradient defined by solutes such as sodium, potassium and chloride dissolved in the water. We have refined a microanalytical method, that detects the x-rays emitted from specific elements when they are bombarded by electrons in a scanning electron microscope, to apply it to the analysis of the retina of the eye. The method facilitates the measurement of the elemental composition, water and osmotic concentration gradients of cells and tissues in the eye, that may be involved in the development of myopia, or short sightedness, a condition that afflicts many people including some 80 - 90% of children in Asia.

A priming study on naming real versus pictures of tools.

There is a growing body of literature demonstrating the relationship between the activation of sensorimotor processes in object recognition. It is unclear, however, if these processes are influenced by the differences in how real (3D) tools and two-dimensional (2D) images of tools are processed by the brain. Here, we examined if these differences could influence the naming of tools. Participants were presented with a prime stimulus that was either a picture of a tool, or a real tool, followed by a target stimulus that was always a real tool. They were then required to name each tool as they appeared. The functional use action required by the target tool was either the same (i.e., squeegee-paint roller) or different (i.e. knife-whisk) to the prime. We found that the format in which the prime tool was presented (i.e., a picture or real tool) had no influence on the participants' response times to naming the target tool. Furthermore, participants were faster at naming target tools relative to prime tools when the exact same tool was presented as both the prime and target. There was no difference in response times to naming the target tool relative to the prime when they were different tools, regardless of whether the tools' functional actions were the same or different. We also found more errors in naming target tools relative to the primes when different tools had a different functional action compared to when the same tool was presented as both the prime and the target. Taken together, our results highlight that the functional actions associated with tools do not facilitate or interfere with the recognition of tools for the purposes of naming. The theoretical implications of these results are discussed.

The Interplay Between Multisensory Associative Learning and IQ in Children.

This study assessed the developmental profile of unisensory and multisensory processes, and their contribution to children's intellectual abilities (8- and 11-year olds, N = 38, compared to adults, N = 19) using a simple audiovisual detection task and three incidental associative learning tasks with different sensory signals: visual-verbal with pseudowords, novel audiovisual, and visual-visual. The level of immaturity throughout childhood was dependent on both, the sensory signal type and the task. Associative learning was significantly enhanced with verbal sounds, compared to novel audiovisual and unisensory visual learning. Visual-verbal learning was also the best predictor of children's general intellectual abilities. The results demonstrate a separate developmental trajectory for visual and verbal multisensory processes and independent contributions to the development of cognitive abilities throughout childhood.

Unexpectedly high prevalence of asthenopia in Australian school children identified by the CISS survey tool.

BACKGROUND: To date there have been few systematic attempts to establish the general prevalence of asthenopia in unselected populations of school-aged children. Thus, the aim of this study was to determine whether the incorporation of Borsting et al's 2003 Revised Convergence-Insufficiency Symptom Survey (CISS) into a general school vision screening could aid in the identification of children with visual discomfort and indicate the need for further investigation. METHODS: Vision screening of an unselected middle school population investigated and analysed the incidence of self-reported nearwork-related visual discomfort via the CISS along with distance and near visual acuities plus non-cycloplegic autorefraction using a Shin-Nippon NVision-K 5001. RESULTS: Of the 384 unselected students approached in Grades 6-9, 353 participated (92.2%, mean 13.2 ± 1.4 years). The mean CISS score for the population without amblyopia and/or strabismus (96.0% of all students) was 16.8 ± 0.6, i.e., 45% of students in this cohort had CISS scores greater than one standard deviation above the mean found by Borsting et al. in 2003 during their validation study of the CISS on 9 to 18 year old children without binocular anomalies. Regression analyses indicated significantly higher (p < 0.001) mean CISS scores for the 3.2% who were hyperopes ≥ + 2.00D by non-cycloplegic autorefraction (27.7 ± 14.7) and for those who were amblyopic (24.3 ± 6.6) or strabismic (34.0 ± 9.8). The mean CISS score of 31.6 ± 9.0 for non-amblyopic/strabismic students having near vision poorer than 0.1 LogMAR was significantly higher (p < 0.001) than for those with good acuity. CONCLUSION: The most important finding of this study was the high incidence of asthenopia in an unselected population and that refractive status per se was not a major contributor to CISS scores. The results highlight the usefulness of the CISS questionnaire for assessment of visual discomfort in school vision screenings and the need for future exploration of near binocular vision status as a potential driver of asthenopia in school students, especially given current trends for frequent daily use of computers and handheld devices and necessarily prolonged accommodative-convergence effort at near, both at school and at home.

Prevalence of Migraine in the Elderly: A Narrated Review.

Migraine is one of the most prevalent neurological disorders among all age groups including the elderly, but the incidence and prevalence of migraine tend to decrease with age. The clinical phenotype of migraine also appears to be different in the elderly patient group in comparison to the younger patient group, with elderly migraine appearing to be more often bilateral and associated with what has become known as "late-life migraine accompaniments. Furthermore, difficulty in the differentiation of migraine from vascular insults such as transient ischemic attacks and amyloid angiopathy and other multiple comorbidities, polypharmacy and age-related changes in pharmacodynamics and pharmacokinetics makes treatments for this cohort challenging but necessary, especially given the worldwide increase in life expectancy, and likelihood of migraine continuing to be a major personal and public health problem.

A pantomiming priming study on the grasp and functional use actions of tools.

It has previously been demonstrated that tool recognition is facilitated by the repeated visual presentation of object features affording actions, such as those related to grasping and their functional use. It is unclear, however, if this can also facilitate pantomiming. Participants were presented with an image of a prime followed by a target tool and were required to pantomime the appropriate action for each one. The grasp and functional use attributes of the target tool were either the same or different to the prime. Contrary to expectations, participants were slower at pantomiming the target tool relative to the prime regardless of whether the grasp and function of the tool were the same or different-except when the prime and target tools consisted of identical images of the same exemplar. We also found a decrease in accuracy of performing functional use actions for the target tool relative to the prime when the two differed in functional use but not grasp. We reconcile differences between our findings and those that have performed priming studies on tool recognition with differences in task demands and known differences in how the brain recognises tools and performs actions to make use of them.

A new look at the developmental profile of visual endogenous orienting.

There is a long-standing assumption that covert measurement of orienting, the shifting of the "mind's eye" independent of a saccade to a location in space, is a more "pure" measure of underlying attention than overt measurement of orienting. Testing attention covertly often relies on target detection tasks, which depend on making a decision about when and where a target has appeared and what is the appropriate action, all of which are potential confounds in measuring attention in children. This study cross-sectionally examined developmental profiles at ages 6-12  years of endogenous visual orienting. We used two tasks: one that measured orienting with a traditional covert attention button press response and one that measured orienting with eye tracking to measure overt saccades. The results obtained from the two orienting tasks demonstrate that each task measures distinct underlying processes with clear developmental profiles. Orienting, when measured by overt saccades, may be mature by 6 years of age, whereas the more complex manual response selection skills required in manual reaction time covert attention tasks continue to develop through middle childhood.

Multisensory perception and attention in school-age children.

Although it is well known that attention can modulate multisensory processes in adults and infants, this relationship has not been investigated in school-age children. Attention abilities of 53 children (ages 7-13 years) were assessed using three subscales of the Test of Everyday Attention for Children (TEA-Ch): visuospatial attention (Sky Search [SS]), auditory sustained attention (Score), and audiovisual dual task (SSDT, where the SS and Score tasks are performed simultaneously). Multisensory processes were assessed using the McGurk effect (a verbal illusion where speech perception is altered by vision) and the Stream-Bounce (SB) effect (a nonverbal illusion where visual perception is altered by sound). The likelihood of perceiving both multisensory illusions tended to increase with age. The McGurk effect was significantly more pronounced in children who scored high on the audiovisual dual attention index (SSDT). In contrast, the SB effect was more pronounced in children with higher sustained auditory attention abilities as assessed by the Score index. These relationships between attention and the multisensory illusory percepts could not be explained solely by age or children's intellectual abilities. This study suggests that the interplay between attention and multisensory processing depends on both the nature of the multisensory task and the type of attention needed to effectively merge information across the senses.

Short term optical defocus perturbs normal developmental shifts in retina/RPE protein abundance.

BACKGROUND: Myopia (short-sightedness) affects approximately 1.4 billion people worldwide, and prevalence is increasing. Animal models induced by defocusing lenses show striking similarity with human myopia in terms of morphology and the implicated genetic pathways. Less is known about proteome changes in animals. Thus, the present study aimed to improve understanding of protein pathway responses to lens defocus, with an emphasis on relating expression changes to no lens control development and identifying bidirectional and/or distinct pathways across myopia and hyperopia (long-sightedness) models. RESULTS: Quantitative label-free proteomics and gene set enrichment analysis (GSEA) were used to examine protein pathway expression in the retina/RPE of chicks following 6 h and 48 h of myopia induction with - 10 dioptre (D) lenses, hyperopia induction with +10D lenses, or normal no lens rearing. Seventy-one pathways linked to cell development and neuronal maturation were differentially enriched between 6 and 48 h in no lens chicks. The majority of these normal developmental changes were disrupted by lens-wear (47 of 71 pathways), however, only 11 pathways displayed distinct expression profiles across the lens conditions. Most notably, negative lens-wear induced up-regulation of proteins involved in ATP-driven ion transport, calcium homeostasis, and GABA signalling between 6 and 48 h, while the same proteins were down-regulated over time in normally developing chicks. Glutamate and bicarbonate/chloride transporters were also down-regulated over time in normally developing chicks, and positive lens-wear inhibited this down-regulation. CONCLUSIONS: The chick retina/RPE proteome undergoes extensive pathway expression shifts during normal development. Most of these pathways are further disrupted by lens-wear. The identified expression patterns suggest close interactions between neurotransmission (as exemplified by increased GABA receptor and synaptic protein expression), cellular ion homeostasis, and associated energy resources during myopia induction. We have also provided novel evidence for changes to SLC-mediated transmembrane transport during hyperopia induction, with potential implications for signalling at the photoreceptor-bipolar synapse. These findings reflect a key role for perturbed neurotransmission and ionic homeostasis in optically-induced refractive errors, and are predicted by our Retinal Ion Driven Efflux (RIDE) model.

The retina/RPE proteome in chick myopia and hyperopia models: Commonalities with inherited and age-related ocular pathologies.

Purpose: Microarray and RNA sequencing studies in the chick model of early optically induced refractive error have implicated thousands of genes, many of which have also been linked to ocular pathologies in humans, including age-related macular degeneration (AMD), choroidal neovascularization, glaucoma, and cataract. These findings highlight the potential relevance of the chick model to understanding both refractive error development and the progression to secondary pathological complications. The present study aimed to determine whether proteomic responses to early optical defocus in the chick share similarities with these transcriptome-level changes, particularly in terms of dysregulation of pathology-related molecular processes. Methods: Chicks were assigned to a lens condition (monocular +10 D [diopters] to induce hyperopia, -10 D to induce myopia, or no lens) on post-hatch day 5. Biometric measures were collected following a further 6 h and 48 h of rearing. The retina/RPE was then removed and prepared for liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) on an LTQ-Orbitrap Elite. Raw data were processed using MaxQuant, and differentially abundant proteins were identified using moderated t tests (fold change ≥1.5, Benjamini-Hochberg adjusted p<0.05). These differentially abundant proteins were compared with the genes and proteins implicated in previous exploratory transcriptome and proteomic studies of refractive error, as well as the genes and proteins linked to the ocular pathologies listed above for which myopia or hyperopia are risk factors. Finally, gene set enrichment analysis (GSEA) was used to assess whether gene sets from the Human Phenotype Ontology database were enriched in the lens groups relative to the no lens groups, and at the top or bottom of the protein data ranked by Spearman's correlation with refraction at 6 and 48 h. Results: Refractive errors of -2.63 D ± 0.31 D (mean ± standard error, SE) and 3.90 D ± 0.37 D were evident in the negative and positive lens groups, respectively, at 6 h. By 48 h, refractive compensation to both lens types was almost complete (negative lens -9.70 D ± 0.41 D, positive lens 7.70 D ± 0.44 D). More than 140 differentially abundant proteins were identified in each lens group relative to the no lens controls at both time points. No proteins were differentially abundant between the negative and positive lens groups at 6 h, and 13 were differentially abundant at 48 h. As there was substantial overlap in the proteins implicated across the six comparisons, a total of 390 differentially abundant proteins were identified. Sixty-five of these 390 proteins had previously been implicated in transcriptome studies of refractive error animal models, and 42 had previously been associated with AMD, choroidal neovascularization, glaucoma, and/or cataract in humans. The overlap of differentially abundant proteins with AMD-associated genes and proteins was statistically significant for all conditions (Benjamini-Hochberg adjusted p<0.05), with over-representation analysis implicating ontologies related to oxidative stress, cholesterol homeostasis, and melanin biosynthesis. GSEA identified significant enrichment of genes associated with abnormal electroretinogram, photophobia, and nyctalopia phenotypes in the proteins negatively correlated with ocular refraction across the lens groups at 6 h. The implicated proteins were primarily linked to photoreceptor dystrophies and mitochondrial disorders in humans. Conclusions: Optical defocus in the chicks induces rapid changes in the abundance of many proteins in the retina/RPE that have previously been linked to inherited and age-related ocular pathologies in humans. Similar changes have been identified in a meta-analysis of chick refractive error transcriptome studies, highlighting the chick as a model for the study of optically induced stress with possible relevance to understanding the development of a range of pathological states in humans.

Evidence for the need for vision screening of school children in Turkey.

BACKGROUND: In many countries, access to general health and eye care is related to an individual's socioeconomic status (SES). We aimed to examine the prevalence of oculo-visual disorders in children in Istanbul Turkey, drawn from schools at SES extremes but geographically nearby. METHODS: Three school-based vision screenings (presenting distance visual acuity, cover test, eye assessment history, colour vision, gross stereopsis and non-cycloplegic autorefraction) were conducted on 81% of a potential 1014 primary-school children aged 4-10 years from two private (high SES) schools and a nearby government (low SES) school in central Istanbul. Prevalence of refractive errors and school-based differences were analysed using parametric statistics (ANOVA). The remaining oculo-visual aspects were compared using non-parametric tests. RESULTS: Of the 823 children with mean age 6.7 ± 2.2 years, approximately 10% were referred for a full eye examination (8.2% and 16.3% of private/government schools respectively). Vision had not been previously examined in nearly 22% of private school children and 65% of government school children. Of all children, 94.5% were able to accurately identify the 6/9.5 [LogMAR 0.2] line of letters/shapes with each eye and 86.6% the 6/6 line [LogMAR 0], while 7.9% presented wearing spectacles, 3.8% had impaired colour vision, 1.5% had grossly impaired stereo-vision, 1.5% exhibited strabismus, 1.8% were suspected to have amblyopia and 0.5% had reduced acuity of likely organic origin. Of the 804 without strabismus, amblyopia or organic conditions, 6.0% were myopic ≤ - 0.50DS, 0.6% hyperopic ≥ + 2.00DS, 7.7% astigmatic ≥1.00 DC and 6.2% anisometropic ≥1.00DS. CONCLUSIONS: The results highlight the need for general vision screenings for all children prior to school entry given the varied and different pattern of visual problems associated with lifestyle differences in two populations raised in the same urban locale but drawn from different socioeconomic backgrounds.

An asymmetric outer retinal response to drifting sawtooth gratings.

Electroretinogram (ERG) studies have demonstrated that the retinal response to temporally modulated fast-ON and fast-OFF sawtooth flicker is asymmetric. The response to spatiotemporal sawtooth stimuli has not yet been investigated. Perceptually, such drifting gratings or diamond plaids shaded in a sawtooth pattern appear brighter when movement produces fast-OFF relative to fast-ON luminance profiles. The neural origins of this illusion remain unclear (although a retinal basis has been suggested). Thus we presented toad eyecups with sequential epochs of sawtooth, sine-wave, and square-wave gratings drifting horizontally across the retina at temporal frequencies of 2.5-20 Hz. All ERGs revealed a sustained direct-current (DC) transtissue potential during drift and a peak at drift offset. The amplitudes of both phenomena increased with temporal frequency. Consistent with the human perceptual experience of sawtooth gratings, the sustained DC potential effect was greater for fast-OFF cf. fast-ON sawtooth. Modeling suggested that the dependence of temporal luminance contrast on stimulus device frame rate contributed to the temporal frequency effects but could not explain the divergence in response amplitudes for the two sawtooth profiles. The difference between fast-ON and fast-OFF sawtooth profiles also remained following pharmacological suppression of postreceptoral activity with tetrodotoxin (TTX), 2-amino-4-phosphonobutric acid (APB), and 2,3 cis-piperidine dicarboxylic acid (PDA). Our results indicate that the DC potential difference originates from asymmetries in the photoreceptoral response to fast-ON and fast-OFF sawtooth profiles, thus pointing to an outer retinal origin for the motion-induced drifting sawtooth brightness illusion.

Mathematical impairment associated with high-contrast abnormalities in change detection and magnocellular visual evoked response.

The cause of developmental dyscalculia, a specific deficit in acquisition of arithmetic skills, particularly of enumeration, has never been investigated with respect to the patency of the visual magnocellular system. Here, the question of dysfunction of the afferent magnocellular cortical input and its dorsal stream projections was tested directly using nonlinear analysis of the visual evoked potential (VEP) and through the psychophysical ability to rapidly detect visual change. A group of young adults with self-reported deficiencies of arithmetical ability, showed marked impairment in magnitude estimation and enumeration performance-though not in lexical decision reaction times when compared with an arithmetically capable group controlled for age and handedness. Multifocal nonlinear VEPs were recorded at low (24 %) and high (96 %) contrast. First- and second-order VEP kernels were comparable between groups at low contrast, but not at high contrast. The mathematically impaired group showed an abnormal lack of contrast saturation in the shortest latency first-order peak (N60) and a delayed P100 positivity in the first slice of the second-order kernel. Both features have previously been argued to be physiological markers of magnocellular function. Mathematically impaired participants also performed worse on a gap paradigm change detection for digit task showing increased reaction times for high-contrast stimuli but not for low-contrast stimuli compared with controls. The VEP results give direct evidence of abnormality in the occipital processing of magnocellular information in those with mathematical impairment. The anomalous high visual contrast physiological and psychophysical performance suggests an abnormality in the inhibitory processes that normally result in saturation of contrast gain in the magnocellular system.

Does omega-3 fatty acid supplementation enhance neural efficiency? A review of the literature.

OBJECTIVE: While the cardiovascular, anti-inflammatory and mood benefits of omega-3 supplementation containing long chain fatty acids (LCPUFAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are manifest, there is no scientific consensus regarding their effects on neurocognitive functioning. This review aimed to examine the current literature on LCPUFAs by assessing their effects on cognition, neural functioning and metabolic activity. In order to view these findings together, the principle of neural efficiency as established by Richard Haier ("smart brains work less hard") was extended to apply to the neurocognitive effects of omega-3 supplementation. METHODS: We reviewed multiple databases from 2000 up till 2013 using a systematic approach and focused our search to papers employing both neurophysiological techniques and cognitive measures. RESULTS: Eight studies satisfied the criteria for consideration. We established that studies using brain imaging techniques show consistent changes in neurochemical substances, brain electrical activity, cerebral metabolic activity and brain oxygenation following omega-3 supplementation. CONCLUSIONS: We conclude that, where comparison is available, an increase in EPA intake is more advantageous than DHA in reducing "brain effort" relative to cognitive performance.

Omega-3 supplementation improves cognition and modifies brain activation in young adults.

OBJECTIVE: The current study aimed to investigate the effects of eicosapentaenoic acid (EPA)-rich and docosahexaenoic acid (DHA)-rich supplementations on cognitive performance and functional brain activation. DESIGN: A double-blind, counterbalanced, crossover design, with a 30-day washout period between two supplementation periods (EPA-rich and DHA-rich) was employed. Functional magnetic resonance imaging scans were obtained during performance of Stroop and Spatial Working Memory tasks prior to supplementation and after each 30-day supplementation period. RESULTS: Both supplementations resulted in reduced ratio of arachidonic acid to EPA levels. Following the EPA-rich supplementation, there was a reduction in functional activation in the left anterior cingulate cortex and an increase in activation in the right precentral gyrus coupled with a reduction in reaction times on the colour-word Stroop task. By contrast, the DHA-rich supplementation led to a significant increase in functional activation in the right precentral gyrus during the Stroop and Spatial Working Memory tasks, but there was no change in behavioural performance. CONCLUSIONS: By extending the theory of neural efficiency to the within-subject neurocognitive effects of supplementation, we concluded that following the EPA-rich supplementation, participants' brains worked 'less hard' and achieved a better cognitive performance than prior to supplementation. Conversely, the increase in functional activation and lack of improvement in time or accuracy of cognitive performance following DHA-rich supplementation may indicate that DHA-rich supplementation is less effective than EPA-rich supplementation in enhancing neurocognitive functioning after a 30-day supplementation period in the same group of individuals.

Meta-analyses indicate associations between neuroendocrine activation, deactivation in neurotrophic and neuroimaging markers in depression after stroke.

BACKGROUND: The association between stroke and depression is well established and has been suggested to be bidirectional. Systemic immune activation, hypothalamic-pituitary-adrenal axis hyperactivity, physiologic changes in the perfusion of blood vessels, the downregulation of neurotrophic factors, and apoptosis and necrosis of neuronal, glial, and endothelial cells have been frequently implicated in this relationship. A better understanding of the biology of poststroke depression could be important for enhancing clinical management. We review the currently available biologic markers of stroke-associated depressive illness (i.e., neurophysiologic, neuroendocrine, immunologic, and neuroimaging markers as well as neurotrophic factors). METHODS: Search strategies included the electronic databases PubMed, PsycINFO, EMBASE, CINAHL, the Cochrane Library, and Proquest Dissertations (all records through June 2012), the reference lists of retrieved articles, the reference list of relevant reviews, and direct contact with authors of retrieved articles for any additional unpublished data. RESULTS: Thirty-three papers fulfilled the criteria for inclusion. We detected moderate effects for high postdexamethasone cortisol levels (odds ratio [OR] 3.28; 95% confidence interval [CI] 1.28-8.39; P = .01), lower serum brain-derived neurotrophic factor levels (standardised mean difference [SMD] -0.52; 95% CI -0.84 to -0.21; P = .001), smaller amygdala volumes (SMD -0.45; 95% CI -0.89 to -0.02; P = .04), and a small effect for overall brain perfusion reduction (SMD -0.35; 95% CI -0.64 to -0.06; P = .02), respectively, to poststroke depression. CONCLUSIONS: Cortisol-lowering therapies and those that increase blood flow and neurotrophic factors represent promising novel therapeutics for depression subtypes and may reduce the risk of depression in stroke patients.