fMRI Methods Research Articles

A robust SSFP technique for fMRI at ultra-high field strengths

A non-balanced (nb) SSFP-based fMRI method based on CE-FAST is presented to alleviate some shortcomings of high spatial-specificity techniques commonly used in high static magnetic fields. The proposed sequence does not suffer from the banding artifacts inherent to balanced (b) SSFP, has low geometrical distortions and SAR compared to spin-echo EPI, and in contrast to previous nbSSFP implementations, is applied at a TR, theoretically prescribed for the optimum contrast. Its non-balanced gradient was chosen to just dephase the unwanted signal component (2π dephasing per TR per voxel). 3D data were acquired from nine healthy subjects, who performed a visual-motor task on a 7 Tesla scanner. For comparison, experiments were accompanied by similar bSSFP and spin-echo acquisitions. Consistent activation was achieved in all subjects with theoretically optimal TR, in contrast to previous nbSSFP techniques. The signal stability as well as relative and absolute functional signal changes, were found to be comparable with bSSFP and spin-echo techniques. The results suggest that with suitable modifications, CE-FAST can be regarded as a robust SSFP-based method for high spatial specificity fMRI techniques.

Assessing the repeatability of absolute CMRO2, OEF and haemodynamic measurements from calibrated fMRI

As energy metabolism in the brain is largely oxidative, the measurement of cerebral metabolic rate of oxygen consumption (CMRO2) is a desirable biomarker for quantifying brain activity and tissue viability. Currently, PET techniques based on oxygen isotopes are the gold standard for obtaining whole brain CMRO2 maps. Among MRI techniques that have been developed as an alternative are dual calibrated fMRI (dcFMRI) methods, which exploit simultaneous measurements of BOLD and ASL signals during a hypercapnic-hyperoxic experiment to modulate brain blood flow and oxygenation.In this study we quantified the repeatability of a dcFMRI approach developed in our lab, evaluating its limits and informing its application in studies aimed at characterising the metabolic state of human brain tissue over time. Our analysis focussed on the estimates of oxygen extraction fraction (OEF), cerebral blood flow (CBF), CBF-related cerebrovascular reactivity (CVR) and CMRO2 based on a forward model that describes analytically the acquired dual echo GRE signal.Indices of within- and between-session repeatability are calculated from two different datasets both at a bulk grey matter and at a voxel-wise resolution and finally compared with similar indices obtained from previous MRI and PET measurements. Within- and between-session values of intra-subject coefficient of variation (CVintra) calculated from bulk grey matter estimates 6.7 ± 6.6% (mean ± std.) and 10.5 ± 9.7% for OEF, 6.9 ± 6% and 5.5 ± 4.7% for CBF, 12 ± 9.7% and 12.3 ± 10% for CMRO2. Coefficient of variation (CV) and intraclass correlation coefficient (ICC) maps showed the spatial distribution of the repeatability metrics, informing on the feasibility limits of the method.In conclusion, results show an overall consistency of the estimated physiological parameters with literature reports and a satisfactory level of repeatability considering the higher spatial sensitivity compared to other MRI methods, with varied performance depending on the specific parameter under analysis, on the spatial resolution considered and on the study design.

Perceived Gaze Direction Modulates Neural Processing of Prosocial Decision Making.

Gaze direction is a common social cue implying potential interpersonal interaction. However, little is known about the neural processing of social decision making influenced by perceived gaze direction. Here, we employed functional magnetic resonance imaging (fMRI) method to investigate 27 females when they were engaging in an economic exchange game task during which photos of direct or averted eye gaze were shown. We found that, when averted but not direct gaze was presented, prosocial vs. selfish choices were associated with stronger activations in the right superior temporal gyrus (STG) as well as larger functional couplings between right STG and the posterior cingulate cortex (PCC). Moreover, stronger activations in right STG was associated with quicker actions for making prosocial choice accompanied with averted gaze. The findings suggest that, when the cue implying social contact is absent, the processing of understanding others’ intention and the relationship between self and others is more involved for making prosocial than selfish decisions. These findings could advance our understanding of the roles of subtle cues in influencing prosocial decision making, as well as shedding lights on deficient social cue processing and functioning among individuals with autism spectrum disorder (ASD).

Optical Properties Influence Visual Cortical Functional Resolution After Cataract Surgery and Both Dissociate From Subjectively Perceived Quality of Vision.

To investigate the relation between optical properties, population receptive fields (pRFs), visual function, and subjectively perceived quality of vision after cataract surgery. The study includes 30 patients who had recently undergone bilateral sequential cataract surgery. We used functional magnetic resonance imaging and pRF modelling methods to assess pRF sizes across visual cortical regions (V1-V3). Subjects also performed a complete ophthalmologic and psychophysical examination and answered a quality of vision questionnaire. Subjects with worse optical properties had, as predicted, larger pRF sizes. In addition, analysis in the primary visual cortex revealed significantly larger mean pRF sizes for operated subjects with worse contrast sensitivity (P = 0.038). In contrast, patients who scored high in the subjective "bothersome" dimension induced by dysphotic symptoms had surprisingly lower pRF size fitting interception (P = 0.012) and pRF size fitting slopes (P = 0.020), suggesting a dissociation between objective quality of vision and subjective appraisal. Optical properties of the eye influence pRF size. In particular, visual aberrations have a negative impact on visual cortical processing. A novel dissociation between subjective reports of quality of vision and pRF sizes was further identified. This suggests that patients with better cortical resolution may have a negative subjective response possibly because of improved perception of dysphotic phenomena. pRF properties represent a valuable quantitative measure to objectively evaluate quality of vision but do not necessarily predict subjective complaints.

Optimization of fMRI methods to determine laterality of cortical activation during ankle movements of children with unilateral cerebral palsy

Measurement of laterality of motor cortical activations may provide valuable information about lower limb control in children with unilateral cerebral palsy (UCP). Evidence from upper limb research suggests that increased contralateral activity may accompany functional gains. However, lower limb areas of activation and associated changes have been underexplored due to challenges with imaging motor cortical leg representations. In this study, methods for a task-based functional magnetic resonance imaging (fMRI) ankle dorsiflexion paradigm were refined with three pilot groups of participants: (i) adults (n = 5); (ii) typically developing (TD) children (n = 5) and; (iii) children with UCP (n = 4). Parameters of experimental design, task resistance, reproducibility, and pre-scan procedures were tested/refined using a staged development approach with additions or changes introduced if image quality did not meet pre-defined standards. When image quality was acceptable for two consecutive participants, the next participant group was recruited to test/refine the next parameter. The final paradigm involved an event-related design of a single dorsiflexion movement against individualized resistance, with two runs per leg. It included a pre-scan session to increase child comfort and determine task resistance. This paradigm produced valid data for laterality index (LI) calculations to determine the ratio of activity in each hemisphere. Ventricle and lesion masks were used in non-linear image registration, and individual thresholds were used for extent-based LI calculations. LI of dominant ankle movements were contralateral (LI ≥ +0.2) for TD children (mean LI = +0.89, std = 0.27) and children with UCP (mean LI = +0.86, std = 0.26). For the affected ankle of children with UCP, LI values indicated ipsilateral and/or contralateral activation (mean LI = +0.02, std = 0.71, range −0.92 to +1.00). This fMRI paradigm will support investigations of cortical activation and mechanisms of skill improvement following lower limb interventions.

Comment on “Using functional Magnetic Resonance Imaging (fMRI) to analyze brain region activity when viewing landscapes”

Modern neuroscience methods, such as functional Magnetic Resonance Imaging (fMRI), offer the unparalleled opportunity to monitor the human brain in vivo − a revolution that has had a tremendous impact on many disciplines (economics, culture, health). Thus, the paper by Tang et al. (2017) is an exciting epistemological step introducing this technology and the possibilities for those studying the health effects of landscapes. Yet, as in similar interdisciplinary efforts there are always risks: questions are very general or results are misinterpreted. The present commentary aims, using examples and a simple but rigorous language, to help the audience of Landscape and Urban Planning understand the basic principles of fMRI and neuroscience methods We end up with a call to landscape researchers and others studying how environments can affect people’s mental health and well-being to boldly be involved in this exciting interdisciplinary effort to help neuroscientists understand how the brain works.

Regression of post-stroke aphasia and associated non-speech syndromes caused by a course of restorative treatment including intensive speech therapy

To analyze clinical and fMRI indicators related with the therapeutic effectiveness of complex restorative treatment including intensive speech therapy in various clinical forms and severity of the aphasia syndrome. The study included 40 right-handed patients with aphasia syndrome after the first hemispheric ischemic stroke. Patients were studied 3 month after disease onset. Patients were examined before and after rehabilitation treatment (4.7 weeks) including intensive speech therapy (15 hours of exercise per week). Evaluation of the effectiveness of treatment was carried out based on the dynamics of the results of neuropsychological, neurological and neuroimaging examinations of patients before and after treatment. The degree of recovery of speech and non-speech cognitive functions (based on the 10-point cognitive assessment, the dynamics of focal neurological deficit (NIHSS) and functional recovery of patients (Barthel index, modified Rankin scale) were assessed. Neuroimaging methods included structural MRI and two fMRI methods: fMRI resting state and fMRI equivalent of the evoked potentials of mismatch negativity (HP), using a sequence of standard and deviant sounds (Russian phonemes) to obtain the equivalent of HP. For statistical calculations, the program in Python version 3.6.0 was used. The maximum efficacy of restorative treatment (≥15% improvement in the scores of 10-point quantifying) was detected in 28 (70%) cases: 18 patients with initially severe and 10 patients with moderate aphasia, regardless of the clinical form of aphasia, and 11 patients with isolated sensory aphasia. Regression of speech and non-speech cognitive impairments in sensory aphasia was accompanied by a pronounced activation of intact speech homologues of the right hemisphere and the appearance of a small temporal and parietal region, which was small in volume and weak in intensity, similar in the localization to the norm. Regardless of the clinical form of aphasia, maximum therapeutic efficacy was accompanied by a reorganization of the speech neuronal rest network, which includes enhancement of both intra- and interhemispheric functional connectivity, with the predominance of amplification of the intra-hemispheric interactions of the posterior speech zones to the left while reducing their interhemispheric connectivity. Significant improvement in motor and sensory functions was detected in 9 (22%) patients with moderate contralateral spastic hemiparesis (p≤0.00) and did not correlate with the degree of regression of speech and non-speech focal cognitive impairments. A slight therapeutic effect was observed in 12 (30%) patients with mild to moderate speech and non-speech cognitive impairment. This effect was not correlated with a specific clinical form of aphasia. The maximum effectiveness of the 4.7 week restorative inpatient treatment, including intensive speech therapy (15 sessions per week), was obtained mainly with severe aphasia, and also with a specific clinical form - isolated sensory aphasia. According to the fMRI data, various compensatory reorganization of the neural speech network was detected, which probably reflects post stroke neuroplasticity associated with both the severity of aphasia and its specific clinical form.

Face processing in a case of high functioning autism with developmental prosopagnosia

The ability to "read" the information about facial identity, expressed emotions, and intentions is crucial for non‑verbal social interaction. Neuroimaging and clinical studies consequently link face perception with fusiform gyrus (FG) and occipital face area (OFA) activity. Here we investigated face processing in an adult, patient PK, diagnosed with both high functioning autism spectrum disorder (ASD) and developmental prosopagnosia (DP). Both disorders have a significant impact on face perception and recognition, thus creating a unique neurodevelopmental condition. We used eye‑tracking and functional magnetic resonance imaging (fMRI) method. Eye‑tracking and fMRI results of PK were compared to results of control subjects. Patient PK showed atypical gaze‑fixation strategy during face perception and typical patterns of brain activations in the FG and OFA. However, a significant difference between PK and control subjects was found in the left anterior superior temporal sulcus/middle temporal gyrus (aSTS/MTG). In PK the left aSTS/MTG was hypo‑activated in comparison to the control subjects. Additionally, functional connectivity analysis revealed decreased inter‑hemispheric connectivity between right and left aSTS/MTG in 'ASD and DP' patient during face recognition performance as compared to the control subjects. The lack of activity in the left aSTS/MTG observed in the case of the clinical subject, combined with the behavioral, eye‑tracking, and neuropsychological results, suggests that impairment of the cognitive mechanism of face recognition involves higher level of processing. It seems to be related to insufficient access to semantic knowledge about the person when prompted by face stimuli.

Disrupted brain network topology in chronic insomnia disorder: A resting-state fMRI study.

This study investigated the topological characteristics of brain functional networks in chronic insomnia disorder (CID) patients. The resting-state functional magnetic resonance imaging and graph theory analysis method were applied to investigate the brain functional connectome patterns among 45 CID patients and 32 healthy controls. The brain functional connectome was constructed by thresholding partial correlation matrices of 90 brain regions from an automated anatomical labeling atlas. The topologic properties of brain functional connectomes at both global and nodal levels were tested. The CID patients had decreased number of module (p = .014) and hierarchy (p = .038), and increased assortativity (p = .035). Furthermore, some brain regions located in the default mode network, dorsal attention network, and sensory-motor network in these patients showed altered nodal centralities. Within these areas, the node betweenness of right central paracentral lobule had positive correlation with the Pittsburgh Sleep Quality Index score (R = 0.319, p = .039). The results imply that functional disruptions of CID patients may be related to disruptions in global and regional topological organization of the brain functional connectome, and provide new and important insights to understand the pathophysiological mechanisms of CID.

Cognitive disorders in ovarian cancer patients (literature review)

The article provides a review of cognitive impairment in oncology patients basing on the example of ovarian cancer women. Consecutive steps in the research for neuropsychological assessment of cancer patient with non-CNS tumors are demonstrated, including currently existing cognitive studies for oncogynecological patients. The suspected reasons for cognitive impairment at different treatment stages are being analyzed with the focus on cognitive dysfunction in the group of ovarian cancer patients. It is being discussed in the article that besides of the neurotoxic influence of chemo treatment, cognitive functions of the ovarian cancer patients can be impaired due to various other factors and that the subjective assessment of cognitive functioning does not correspond to the objective results of the neuropsychological assessment. It is stated in the article that at the moment there is no uniform methodological approach for neuropsychological assessment of ovarian cancer patients and multidisciplinary platform is required including the use of EEG, MRI and fMRI methods for precise evaluation of subtle cognitive impairments.

Functional near-infrared spectroscopy is in moderate accordance with functional MRI in determining lateralisation of frontal language areas.

Purpose Understanding language dominance is crucial in pre-surgical evaluation of patients with epilepsy and in patients having a tumour close to the language area. Functional magnetic resonance imaging (fMRI) studies are well established in evaluating language dominance. Functional near-infrared spectroscopy (fNIRS) is a non-invasive optical imaging modality that offers a convenient and affordable technique to image language-related cortical areas. This study investigates the agreement between results from task-based fMRI and fNIRS in determining language lateralisation. Methods Language laterality indices LIs were calculated from both fMRI and fNIRS measurements of the same individual volunteers by using an identical paradigm. Statistical measures of percentage agreement and kappa value have been calculated for testing agreement and reliability. Results A correlation analysis of the LI values shows a good correlation with r = 0.677 at p < 0.05. Statistical comparison of both fMRI and fNIRS methods for language lateralisation yielded a percentage agreement of 90% and a moderate kappa value of κ = 0.621. Conclusion Our study suggests that fNIRS is in moderate accordance with fMRI in determining lateralisation of the frontal language areas. It implies that the optical imaging technique can provide additional information on functional lateralisation of frontal language areas.

Effects of spatial smoothing on functional brain networks.

Graph‐theoretical methods have rapidly become a standard tool in studies of the structure and function of the human brain. Whereas the structural connectome can be fairly straightforwardly mapped onto a complex network, there are more degrees of freedom in constructing networks that represent functional connections between brain areas. For functional magnetic resonance imaging (fMRI) data, such networks are typically built by aggregating the blood‐oxygen‐level dependent signal time series of voxels into larger entities (such as Regions of Interest in some brain atlas) and determining their connection strengths from some measure of time‐series correlations. Although it is evident that the outcome must be affected by how the voxel‐level time series are treated at the preprocessing stage, there is a lack of systematic studies of the effects of preprocessing on network structure. Here, we focus on the effects of spatial smoothing, a standard preprocessing method for fMRI. We apply various levels of spatial smoothing to resting‐state fMRI data and measure the changes induced in functional networks. We show that the level of spatial smoothing clearly affects the degrees and other centrality measures of functional network nodes; these changes are non‐uniform, systematic, and depend on the geometry of the brain. The composition of the largest connected network component is also affected in a way that artificially increases the similarity of the networks of different subjects. Our conclusion is that wherever possible, spatial smoothing should be avoided when preprocessing fMRI data for network analysis.

Two-Dimensional Temporal Clustering Analysis for Patients with Epilepsy: Detecting Epilepsy-Related Information in EEG-fMRI Concordant, Discordant and Spike-Less Patients.

EEG acquired simultaneously with fMRI (EEG-fMRI) is a multimodal method that has shown promise in mapping the seizure onset zone in patients with focal epilepsy. However, there are many instances when this method is unsuccessful or not applicable, and other data driven fMRI methods may be utilized. One such method is the two-dimensional temporal clustering analysis (2dTCA). In this study we compared the classic EEG-fMRI and 2dTCA performance in mapping regions related to the seizure onset region in 18 focal epilepsy patients (12 presenting interictal epileptiform discharges (IEDs), during EEG-fMRI acquisition) with Engel I or II surgical outcome. Activation maps of both 2dTCA timing outputs (positive and negative histograms) and EEG detected IEDs were computed and compared to the region of epilepsy surgical resection. Patients were evaluated in three categories based on frequency of EEG detected spiking during the MRI. EEG-fMRI maps were concordant to the epilepsy region in 5/12 subjects, four with frequent IEDs on EEG. The 2dTCA was successful in mapping 13/18 patients including 3/6 with no IEDs detected (10/12 with IEDs detected). The epilepsy-related activities were successfully mapped by both methods in only 4/12 patients. This work suggests that the epilepsy-related information detected by each method may be different: while EEG-fMRI is more accurate in patients with high rather than lower numbers of EEG detected IEDs; 2dTCA can be useful in evaluating patients even when no concurrent EEG spikes are detected or EEG-fMRI is not effective. Therefore, our results support that 2dTCA might be an alternative for mapping epilepsy-related BOLD activity in negative EEG-fMRI (6/7 patients) and spike-less patients.

Chapter 37 - Overview of neuroradiology

Neuroradiology with computed tomography (CT) and magnetic resonance imaging (MRI) is essential for the initial evaluation of patients with a clinical suspicion of brain and spine disorders. Morphologic imaging is required to obtain a probable diagnosis to support the treatment decisions in pre- and perinatal disorders, vascular diseases, traumatic injuries, metabolic disorders, epilepsy, infection/inflammation, neurodegenerative disorders, degenerative spinal disease, and tumors of the central nervous system. Different postprocessing tools are increasingly used for three-dimensional visualization and quantification of lesions. Additional information is provided by angiographic methods and physiologic CT and MRI techniques, such as diffusion MRI, perfusion CT/MRI, MR spectroscopy, functional MRI, tractography, and nuclear medicine imaging methods. Positron emission tomography (PET) is now integrated with CT (PET/CT), and PET/MR scanners have recently also been introduced. These hybrid techniques facilitate the co-registration of lesions with different modalities, and give new possibilites for functional imaging. Repeated imaging is increasingly performed for treatment monitoring. The improved imaging techniques together with the neuropathologic diagnosis after biopsy or surgery allow more personalized treatment of the patient. Neuroradiology also includes endovascular treatment of aneurysms and arteriovenous malformations as well as thrombectomy in acute stroke. This catheter-based treatment has replaced invasive neurosurgery in many cases.

Odor selectivity of hyposmia and cognitive impairment in patients with Parkinson's disease.

ObjectiveHyposmia is one of the earliest non-motor features of Parkinson’s disease (PD) and can precede the onset of motor symptoms by years. Most of the current olfactory detection tests are targeted at Western populations. The exact relationship between hyposmia and cognitive impairment is unknown. The purpose of the study was to find bromines that can effectively identify olfactory dysfunction and investigate the relationship between hyposmia and cognitive function in early, non-demented, drug-naïve patients with PD in the People’s Republic of China.MethodsSixty-three early, non-demented, drug-naïve patients with PD and 55 healthy controls were enrolled in the study. The T&T olfactometer and a Chinese version of Montreal Cognitive Assessment (MoCA) were applied to assess subjects’ olfactory and cognitive functions. Patients with PD also completed the Modified Unified Parkinson’s disease-rating scale (UPDRS) and Hoehn and Yahr (H&Y) scale.ResultsPatients with PD had lower scores of visuospatial and executive function (p=0.000), attention (p=0.03), and delayed recall (p=0.001) than controls. β-phenylethyl alcohol (floral smell, smell of rose petals) and isovaleric acid (smell of sweat, stuffy socks) were more sensitive for identifying hyposmia in patients with PD than three other odors. Multivariate logistic regression analysis showed that impaired visuospatial and executive function was associated with hyposmia (p=0.013), but was independent of other PD-associated variables.ConclusionHyposmia was common in early, non-demented, drug-naïve PD patients. β-Phenylethyl alcohol and isovaleric acid were more superior for identifying hyposmia in early non-demented Chinese patients with PD. Hyposmia was associated with impaired visuospatial and executive function in patients with PD. Further prospective studies that apply a series of neuropsychological tests and functional magnetic resonance imaging methods in large samples in multicenter studies are needed to confirm our findings and to investigate the relationship between hyposmia and cognitive function with disease progression in patients with PD.

Alpha band event-related desynchronization underlying social situational context processing during irony comprehension: A magnetoencephalography source localization study

Irony comprehension requires integration of social contextual information. Previous studies have investigated temporal aspects of irony processing and its neural substrates using psychological/electroencephalogram or functional magnetic resonance imaging methods, but have not clarified the temporospatial neural mechanisms of irony comprehension. Therefore, we used magnetoencephalography to investigate the neural generators of alpha-band (8–13Hz) event-related desynchronization (ERD) occurring from 600 to 900ms following the onset of a critical sentence at which social situational contexts activated ironic representation. We found that the right anterior temporal lobe, which is involved in processing social knowledge and evaluating others’ intentions, exhibited stronger alpha ERD following an ironic statement than following a literal statement. We also found that alpha power in the left anterior temporal lobe correlated with the participants’ communication abilities. These results elucidate the temporospatial neural mechanisms of language comprehension in social contexts, including non-literal processing.

P 135 Using a BCI approach to record ERPs for detecting signs of awareness in patients with severe disorders of consciousness

Objective In the clinical setting mainly behavioral methods are used for differentiating between patients with unresponsive wakefulness syndrome (UWS) and minimally consciousness syndrome (MCS). These may result in a high rate of false negative classifications, as some patients cannot produce clear behavioral responses, although they are conscious. To increase diagnostic objectivity additional methods to assess patients” states of consciousness are needed. FMRI methods have proven useful, but are costly and rarely available. Building up on previous ERP (event related potential ) studies in patients with severe disorders of consciousness ( Neumann and Kotchoubey, 2004 ) we tested an ERP measurement system based on brain-computer interface (BCI) technology (mindbeagle, g.tec, Schiedlberg) as patient bedside instrument to detect consciousness under exclusion of behavioral response requirements. Methods Recordings were performed in 13 patients with severe disorders of consciousness(5MCS, 8UWS), as diagnosed by the Coma Recovery Scale revised (CRSr). The BCI testing consisted of two subtests, an auditory and vibro-tactile paradigm. For both subtests patients were instructed to react to a rare target stimulus and to neglect an often occurring non-target stimulus. Accordingly the subtests combine the passive (Oddball structure) and the active (instruction to react to target stimulus) paradigm. In the auditory subtest two distinct pure tones (500 Hz and 1000 Hz) were presented on both ears. In the vibro-tactile subtest vibration via vibro-tactile trajectories was either transported to the patients left (target) or right (non-target) wrist. The accuracy level at which a non-target and target could be differentiated by the system classifier, trained on the patient’s P300 response, was used as an outcome measure. Results With exception of two patients (one in UWS and one in MCS ) all participants showed an accuracy level above chance (12.5%) in at least one of the subtests. In the auditory subtest this was true for two patients with MCS (20%, 30%) and three with UWS (100%, 30%, 80%). In the vibro-tactile subtest for three patients with MCS (40%, 20%, 20%) and four patients with UWS (50%, 20%, 60%, 60%) the target vs. non-target discrimination could be made. Conclusion Although there are still improvements necessary to use the applied system as a diagnostic instrument in the clinical setting (e.g. adaptations to the clinical population, precise manual for standardized testing), we were able to detected signs of awareness in patients that were not accessible by behavioral measurements. Additional research is needed to determine validity and significance of that finding.

Optical properties shape visual cortical population receptive fields after cataract surgery independently from subjective quality of vision

PurposeTo study the impact of changed optical properties on cortical population receptive fields (pRF), psychophysical function and participant reported quality of vision after cataract surgery.MethodsWe studied 30 patients after recent bilateral sequential cataract surgery, using functional magnetic resonance imaging and pRF modelling methods to assess pRF sizes across early visual regions. Ophthalmological and psychophysical evaluation was also performed, and a quality of vision questionnaire was obtained.ResultsWe found that subjects with worse optical properties had larger pRF sizes. pRF sizes in the primary visual cortex were also larger for operated subjects with worse contrast sensitivity (p = 0.038). Surprisingly, patients who were more bothered by dysphotic symptoms showed lower pRF size fitting interception (p = 0.012) and pRF size fitting slopes (p = 0.020), showing that objective and subjective quality of vision may dissociate.ConclusionsOptical properties of the eye influence PRF sizes and both dissociate from subjective quality of vision, suggesting that patients with better cortical resolution may have augmented dysphotic perception, and consequently more visual complaints, in spite of improved optical quality.

The supramarginal and angular gyri underlie orthographic competence in Spanish language

Orthographic competence allows automatic word recognition and reading fluency. To elucidate how the orthographic competence in Spanish-speaking adults might affect the neurofunctional mechanisms of visual word recognition, 32 young adults equally divided in two groups (HSS: High Spelling Skills, and LSS: Low Spelling Skills) were evaluated using fMRI methods, while they performed an orthographic recognition task involving pseudohomophones. HSS achieved significantly more correct responses and lower reaction times than LSS. Interestingly, LSS showed greater activation in the left angular and supramarginal regions with increased bilateral activation pattern in the inferior frontal gyrus, and the anterior temporal and posterior parietal regions. In contrast, HSS showed a more left-lateralized pattern over these regions along with higher activation of the anterior cingulated gyrus for misspelled words. Results suggest that the differences found in cortical activation patterns might be explained by the higher degree of specialization for word recognition in HSS, a group of participants that due to their greater orthographic skills require less engagement of processing resources to succeed in the task.

Ten Key Observations on the Analysis of Resting-state Functional MR Imaging Data Using Independent Component Analysis.

For more than 20 years, the powerful, flexible family of independent component analysis (ICA) techniques has been used to examine spatial, temporal, and subject variation in functional magnetic resonance (fMR) imaging data. This article provides an overview of 10 key principles in the basic and advanced application of ICA to resting-state fMR imaging. ICA's core advantages include robustness to artifact; false-positives and autocorrelation; adaptability to variant study designs; agnosticism to the temporal evolution of fMR imaging signals; and ability to extract, identify, and analyze neural networks. ICA remains in the vanguard of fMRI methods development.