Left Hemisphere Research Articles

Assessment of white matter microstructure integrity in subacute postconcussive vestibular dysfunction using NODDI

Abstract Vestibular symptoms, such as dizziness and balance impairment, are frequently reported following mild traumatic brain injury (mTBI) and are associated with a protracted recovery, yet the underlying neuroanatomical substrates remain unclear. The present study utilized advanced diffusion MRI (dMRI) techniques including both conventional diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) to investigate microstructural white matter integrity in individuals with postconcussive vestibular dysfunction (PCVD) within the subacute injury period (median of 35 days from injury; IQR of 23). Study participants included 23 individuals with subacute PCVD and 37 healthy control subjects who underwent imaging and comprehensive clinical vestibular testing. Between-group voxelwise analysis of differences in white matter revealed areas of higher intra-neurite volume fraction (VIn) and isotropic volume fraction (VIso) within PCVD subjects compared to controls, which involved overlapping regions within the left hemisphere of the brain. Affected areas of higher VIn and VIso included the superior longitudinal fasciculus (SLF) and superior and posterior corona radiata (SCR and PCR, respectively). We examined the relationship between clinical vestibular measures and diffusion metrics including DTI (fractional anisotropy [FA], mean diffusivity [MD], radial diffusivity [RD] and axial diffusivity [AD]) and NODDI (intraneurite volume fraction [VIn], isotropic volume fraction [VIso], dispersion anisotropy [DA], orientation dispersion indexTotal/Primary/Secondary [ODIT/P/S]) within 32 regions-of-interest. Clinical vestibular measures included self-reported measures, including the Dizziness Handicap Inventory, Visual Vertigo Analog Scale, and Vestibular/Ocular-Motor Screening, as well as objective vestibular testing using the sensory organization test. Significant correlations were found with clinical measures across all diffusion maps (except DA), within various regions of interest (ROIs), including SLF, SCR, and PCR. These results implicate several important association bundles that may potentiate sensory processing dysfunction related to PCVD. Whether these neuroanatomical differences found within the subacute phase of PCVD are in response to injury or represent preexisting structural variations that increase vulnerability to sensory processing dysfunction is unclear and remains an active area of study.

Performance of cognitive tasks and functional brain activity in anxiety disorders

Objective. To improve understanding of psychophysiological underpinnings of anxiety disorders a comprehensive study, that included the analysis of cognitive tasks performance, event-related potentials and psychometric scales, has been conducted.Materials and Methods. Participants were patients with generalized anxiety disorder (GAD group — 12 s.), mixed anxiety and depressive disorder (ADD group — 16 s.) and healthy volunteers (control group — 16 s.). The psychometric techniques included the questionnaires of Spielberger, HADS (Hospital Anxiety and Depression Scale) and Carver-White (BIS/BAS Scale). Psychophysiological methods included antisaccade task (AS) and event-related evoked potentials P300 that were recorded during auditory oddball task.Results. The significantly increased anxiety and depression scales, as well as the decreased BAS Reward Responsiveness scale, was found in patients of both clinical groups compared to control one; the increased BIS scale was revealed only in ADD group. In GAD and ADD groups AS performance was worse in response to stimuli in left hemi-field that are initially processed in right hemisphere; on the contrary, decreased number of target stimuli omissions was found in oddball task in clinical groups. P300 amplitude was larger, and P300 latency was shorter for patients with ADD compared to controls. Analysis of asymmetry demonstrated that P300 amplitudes were greater over the frontal-central right than over the left hemisphere in ADD group.Conclusion. The study demonstrated that anxiety disorders are accompanied by reallocation of attentional resources and changes in functional organization of brain networks involved in attention and executive functions. With the same direction, the shifts were greater in ADD group.

Dichotic listening and interhemispheric integration after callosotomy: A systematic review

The right-ear advantage (REA) for recalling dichotically presented auditory-verbal stimuli has been traditionally linked to the dominance of the left cerebral hemisphere for speech processing. Early studies on patients with callosotomy additionally found that the removal of the corpus callosum leads to a complete extinction of the left ear, and consequently the today widely used models to explain the REA assume a central role of callosal axons for recalling the left-ear stimulus in dichotic listening. However, later dichotic-listening studies on callosotomy patients challenge this interpretation, as many patients appear to be able to recall left-ear stimuli well above chance level, albeit with reduced accuracy. The aim of the present systematic review was to identify possible experimental and patient variables that explain the inconsistences found regarding the effect of split-brain surgery on dichotic listening. For this purpose, a systematic literature search was conducted (databases: Pubmed, Web of Knowledge, EBSChost, and Ovid) to identify all empirical studies on patients with surgical section of the corpus callosum (complete or partial) that used a verbal dichotic-listening paradigm. This search yielded ks = 32 publications reporting patient data either on case or group level, and the data was analysed by comparing the case-level incidence of left-ear suppression, left-ear extinction, and right-ear enhancement narratively or statistically considering possible moderator variables (i.a., extent of the callosal surgery, stimulus material, response format, selective attention). The main finding was an increased incidence of left-ear suppression (odds ratio = 7.47, CI95%: [1.21; 83.49], exact p = .02) and right-ear enhancement (odds ratio = 21.61, CI95%: [4.40; 154.11], p < .01) when rhyming as compared with non-rhyming stimuli were used. Also, an increase in left-ear reports was apparent when a response by the right hemisphere was allowed (i.e., response with the left hand). While the present review is limited by the overall small number of cases and a lack of an appropriate control sample in most of the original studies, the findings nevertheless suggest an adjustment of the classical dichotic-listening models incorporating right-hemispheric processing abilities as well as the perceptual competition of the left- and right-ear stimuli for attention.

Accelerated decline in motor suppression in patients with cerebrovascular disorders: A kinetic analysis using the square-tracing task.

Patients with cerebrovascular disorders (CVDs) tend to exhibit impulsive behaviour without controlling their movements, leading to difficulty in performing activities of daily living and an increased risk of accidents. This hastiness, termed 'pacing impairment', has been studied but is not fully understood. To experimentally examine the kinetic features of pacing impairment by focusing on changes in speed and investigating neuropsychological substrates. We instructed 53 inpatients with CVDs, 20 orthopaedic inpatients, and 20 healthy participants to trace a 200 mm-sided square as slowly as possible for 120 seconds. We measured the tracing length and mean acceleration and examined the relationship between these measurements, neuropsychological symptoms, and lesion sites. Gradual acceleration in drawing, i.e., decline in motor suppression, was observed more frequently in the CVD group than in the control groups. Excessive acceleration was associated with unilateral spatial neglect, frontal lobe signs, and attention disorders but not with motor impersistence. Additionally, the incidence of excessive acceleration did not differ between left and right hemisphere lesion subgroups and was not associated with any specific lesion site. Pacing impairment can manifest as general or holistic deficits in attentional function widely distributed throughout the cerebral hemispheres.

Neurorehabilitation potential of kinesiological activation of the cerebral hemisphere/contralateral limbs axis.

According to the theory of hemispheric asymmetry, the brain has a property that shows the difference in the distribution of neuropsychic functions between its right and left hemispheres. It was established long ago that the left hemisphere is more developed in right-handed people, while the right hemisphere is more developed in the left-handed. Currently, this theory is confirmed by neurophysiological examination methods: EEG, echography, evoked potentials, MRI, and bioelectric activity of the brain surface. This area gained even more popularity after establishing the fact of the interaction of cognitive / creative abilities and left-hand activity. This justification has been noted in the works of scientists, neurophysiologists, and experimenters and continues in our literary review. The relationship is established on the basis of motor acts, learning activities in left-handers, and the speed of mastering a particular skill to perfection. Moreover, another interesting aspect of this field is the study of the effect of neurorehabilitation on the restoration of cognitive functions in patients after suffering an acute cerebrovascular accident. The use of long-term sustainable interventions can help stroke survivors engage in their usual activities. Rehabilitation is aimed at restoring functions and cognitive abilities to the maximum attainable level. An analysis of existing scientific and methodological data indicates that targeted therapy methods that promote the activation of functional connections between the hemisphere of the brain and limbs have significant potential in the rehabilitation of patients after stroke. However, the choice of tactics of rehabilitation measures after a stroke does not sufficiently take into account the functional specialization of the damaged areas of the brain and their relationship with higher nervous activity. The introduction of complex kinesiological programs into therapy using modern technologies and digital systems, including virtual and augmented reality (VR / AR) technologies, can turn out to be effective. In this regard, the literature review provides an analysis of the market of modern digital platforms used in targeted rehabilitation.

Functional lateralization in the medial prefrontal cortex control of contextual conditioned emotional responses in rats

A functional lateralization has been reported in control of emotional responses by the medial prefrontal cortex (mPFC). However, a hemisphere asymmetry in involvement of the mPFC in expression of fear conditioning responses has never been reported. Therefore, we investigated whether control by mPFC of freezing and cardiovascular responses during re-exposure to an aversively conditioned context is lateralized. For this, rats had guide cannulas directed to the mPFC implanted bilaterally or unilaterally in the right or left hemispheres. Vehicle or the non-selective synaptic inhibitor CoCl2 was microinjected into the mPFC 10 min before re-exposure to a chamber where the animals had previously received footshocks. A catheter was implanted into the femoral artery before the fear retrieval test for cardiovascular recordings. We observed that bilateral microinjection of CoCl2 into the mPFC reduced both the freezing behavior (enhancing locomotion and rearing) and arterial pressure and heart rate increases during re-exposure to the aversively conditioned context. Unilateral microinjection of CoCl2 into the right hemisphere of the mPFC also decreased the freezing behavior (enhancing locomotion and rearing), but without affecting the cardiovascular changes. Conversely, unilateral synaptic inhibition in the left mPFC did not affect either behavioral or cardiovascular responses during fear retrieval test. Taken together, these results suggest that the right hemisphere of the mPFC is necessary and sufficient for expression of freezing behavior to contextual fear conditioning. However, the control of cardiovascular responses and freezing behavior during fear retrieval test is somehow dissociated in the mPFC, being the former bilaterally processed.

A historical approach to models of emotional laterality

In this paper I discuss the main models that have tried to explain brain asymmetries for emotions. The first models, based on clinical observations, proposed either a general right hemisphere dominance for emotions (the’right hemisphere’) model or a different specialization of the right hemisphere for negative and of the left hemisphere for positive emotions (the‘valence’ model). In more recent times new models, based on partly modified versions of the previous ones have been proposed. The revised version of the ‘valence’ model, labeled the ‘approach-avoidance’ model maintained that hemispheric asymmetries are not related to the valence of the emotional stimulus but to the motivational (approach vs avoidance) system that is engaged by that stimulus. On the contrary, revised versions of the ‘right hemisphere’ hypothesis proposed graded versions of this model, maintaining that only some kinds or some levels of emotions are clearly right lateralized. One version of these models (the’emotion type hypothesis’) assumed that only elementary basic emotions should be subsumed by the right hemisphere, wheres more complex social emotions should be subtended by the left hemisphere. The other version (the ‘schematic level of emotion hypothesis’) assumed that the right hemisphere should subsume only the basic ‘schematic’ level of emotions, characterized by an automatic and unconscious processing, whereas the more propositional and conscious ‘conceptual’ level could be less lateralized or subsumed by the left hemisphere. This last model is supported by the obsevation that the right hemisphere reveals a modus operandi (i.e. a prevalence of the ‘automatic’ over the ‘intentional’ and of the ‘unconscious’ over the ‘conscious’ functional processing) that is typical of the ‘schematic level of emotions.

Individualised prediction of resilience and vulnerability to sleep loss using EEG features.

It is well established that individuals differ in their response to sleep loss. However, existing methods to predict an individual's sleep-loss phenotype are not scalable or involve effort-dependent neurobehavioural tests. To overcome these limitations, we sought to predict an individual's level of resilience or vulnerability to sleep loss using electroencephalographic (EEG) features obtained from routine night sleep. To this end, we retrospectively analysed five studies in which 96 healthy young adults (41 women) completed a laboratory baseline-sleep phase followed by a sleep-loss challenge. After classifying subjects into sleep-loss phenotypic groups, we extracted two EEG features from the first sleep cycle (median duration: 1.6 h), slow-wave activity (SWA) power and SWA rise rate, from four channels during the baseline nights. Using these data, we developed two sets of logistic regression classifiers (resilient versus not-resilient and vulnerable versus not-vulnerable) to predict the probability of sleep-loss resilience or vulnerability, respectively, and evaluated model performance using test datasets not used in model development. Consistently, the most predictive features came from the left cerebral hemisphere. For the resilient versus not-resilient classifiers, we obtained an average testing performance of 0.68 for the area under the receiver operating characteristic curve, 0.72 for accuracy, 0.50 for sensitivity, 0.84 for specificity, 0.61 for positive predictive value, and 3.59 for likelihood ratio. We obtained similar performance for the vulnerable versus not-vulnerable classifiers. These results indicate that logistic regression classifiers based on SWA power and SWA rise rate from routine night sleep can largely predict an individual's sleep-loss phenotype.

Temporo-Parieto-Occipital Disconnection by Robot-Assisted Magnetic Resonance Imaging–Guided Laser Interstitial Thermal Therapy for Refractory Epilepsy in a Pediatric Patient: Proof-of-Principle Case Report and Surgical Nuances

Magnetic resonance imaging-guided laser interstitial thermal therapy (MRIgLITT) has been proven safe and effective for the treatment of focal epilepsy of different etiologies. It has also been used to disconnect brain tissue in more extensive or diffuse epilepsy, such as corpus callosotomy and hemispherotomy. In this study, we report a case of temporo-parieto-occipital disconnection surgery performed using MRIgLITT assisted by a robotic arm for refractory epilepsy of the posterior quadrant. A highly realistic cadaver simulation was performed before the actual surgery. The patient was a 14-year-old boy whose seizures began at the age of 8. The epilepsy was a result of a left perinatal ischemic event that caused a porencephalic cyst, and despite receiving multiple antiepileptic drugs, the patient continued to experience daily seizures which led to the recommendation of surgery. A Wada test lateralized language in the right hemisphere. Motor and sensory function was confirmed in the left hemisphere through magnetic resonance imaging functional studies and NexStim. The left MRIgLITT temporo-parieto-occipital disconnection disconnection was achieved using 5 laser fibers. The patient followed an excellent postoperative course and was seizure-free, with no additional neurological deficits 24months after the surgery.

Short post-injection seizure duration is associated with reduced power of ictal brain perfusion SPECT to lateralize the seizure onset zone.

The aim of this study was to assess the impact of the post-injection electrical seizure duration on the identification of the seizure onset zone (SOZ) in ictal brain perfusion SPECT in presurgical evaluation of drug-resistant epilepsy. 176 ictal SPECT performed with 99mTc-HMPAO (n = 140) or -ECD (n = 36) were included retrospectively. Visual interpretation of the SPECT images (together with individual MRI and statistical hyperperfusion maps) with respect to lateralization (right, left, none) and localization (temporal, frontal, parietal, occipital) of the SOZ was performed by 3 independent readers. Between-readers agreement was characterized by Fleiss' κ. An ictal SPECT was considered "lateralizing" if all readers agreed on right or left hemisphere. It was considered "localizing" if it was lateralizing and all readers agreed on the same lobe within the same hemisphere. The impact of injection latency and post-injection seizure duration on the proportion of lateralizing/localizing SPECT was tested by ANOVA with dichotomized (by the median) injection latency and post-injection seizure duration as between-subjects factors. Median [interquartile range] (full range) of injection latency and post-injection seizure duration were 30 [24, 40] (3-120) s and 50 [27, 70] (-20-660) s, respectively. Fleiss' κ for lateralization of the SOZ was largest for the combination of early (< 30s) injection and long (> 50s) post-injection seizure duration (κ = 0.894, all other combinations κ = 0.659-0.734). Regarding Fleiss' κ for localization of the SOZ in the 141 (80.1%) lateralizing SPECT, it was largest for early injection and short post-injection seizure duration (κ = 0.575, all other combinations κ = 0.329-0.368). The proportion of lateralizing SPECT was lower with short compared to long post-injection seizure duration (estimated marginal means 74.3% versus 86.3%, p = 0.047). The effect was mainly driven by cases with very short post-injection seizure duration ≤ 10s (53.8% lateralizing). Injection latency in the considered range had no significant impact on the proportion of lateralizing SPECT (p = 0.390). The proportion of localizing SPECT among the lateralizing cases did not depend on injection latency or post-injection seizure duration (p ≥ 0.603). Short post-injection seizure duration is associated with a lower proportion of lateralizing cases in ictal brain perfusion SPECT.

Pragmatic Communication Deficit and Functional Outcome in Patients with Right- and Left-Brain Damage: A Pilot Study.

Pragmatic communication abilities refer to the capacity to use language in a social context. Despite evidence to the contrary, the left cerebral hemisphere of the majority of right handers has been considered exclusively specialized for control of language phonology, syntax and semantics, whereas the right hemisphere has been specialized for the control of language pragmatics. Many studies have shown the non-exclusivity of the left hemisphere for language skills. Communication deficits observed in these studies for patients with right hemisphere damage confirmed the necessity for integrity of the right hemisphere across a number of language components. The aim of this study is to investigate the specific role of the right and left hemispheres across several aspects of communication deficits, with particular attention given to the influence of these deficits on functional outcome. The second aim is to characterize possible correlations between pragmatic and other cognitive deficits. We evaluated 22 patients, 15 with left- and 7 with right-brain ischemic or hemorrhagic damage, using cognitive, pragmatic and language tests. We deployed the Right Hemisphere Language Battery-Santa Lucia and Montreal d'Evaluation de la Communication to assess pragmatic abilities. The results showed no statistically significant differences between patients with left- and right-brain damage, highlighting the importance of integration between the two hemispheres in the communication process. Multiple significant correlations were found between pragmatic abilities and cognitive tests assessing global cognitive functioning, pantomime expression and comprehension. Pragmatic deficits were also shown to correlate with functional cognitive outcome. It is important to assess pragmatic abilities in patients with cognitive deficits after both left and right stroke for tailoring neuropsychological intervention to mitigate pragmatic disabilities in functional outcomes.

Neural signatures of imaginary motivational states: desire for music, movement and social play

The literature has demonstrated the potential for detecting accurate electrical signals that correspond to the will or intention to move, as well as decoding the thoughts of individuals who imagine houses, faces or objects. This investigation examines the presence of precise neural markers of imagined motivational states through the combining of electrophysiological and neuroimaging methods. 20 participants were instructed to vividly imagine the desire to move, listen to music or engage in social activities. Their EEG was recorded from 128 scalp sites and analysed using individual standardized Low-Resolution Brain Electromagnetic Tomographies (LORETAs) in the N400 time window (400–600 ms). The activation of 1056 voxels was examined in relation to the 3 motivational states. The most active dipoles were grouped in eight regions of interest (ROI), including Occipital, Temporal, Fusiform, Premotor, Frontal, OBF/IF, Parietal, and Limbic areas. The statistical analysis revealed that all motivational imaginary states engaged the right hemisphere more than the left hemisphere. Distinct markers were identified for the three motivational states. Specifically, the right temporal area was more relevant for “Social Play”, the orbitofrontal/inferior frontal cortex for listening to music, and the left premotor cortex for the “Movement” desire. This outcome is encouraging in terms of the potential use of neural indicators in the realm of brain-computer interface, for interpreting the thoughts and desires of individuals with locked-in syndrome.

Clinical and neuropsychological correlates of theta-band functional excitation-inhibition ratio in autism: An EEG study

ObjectiveHow abnormal brain signaling impacts cognition in autism spectrum disorder (ASD) remained elusive. This study aimed to investigate the local and global brain signaling in ASD indicated by theta-band functional excitation-inhibition (fE/I) ratio and explored psychophysiological relationships between fE/I, cognitive deficits, and ASD symptomatology. MethodsA total of 83 ASD and typically developing (TD) individuals participated in this study. Participants’ interference control and set-shifting abilities were assessed. Resting-state electroencephalography (EEG) was used for estimating theta-band fE/I ratio. ResultsASD individuals (n = 31 without visual EEG abnormality; n = 22 with visual EEG abnormality) generally performed slower in a cognitive task tapping interference control and set-maintenance abilities, but only ASD individuals with visually abnormal EEG performed significantly slower than their TD counterparts (Bonferroni-corrected ps < .001). Heightened theta-band fE/I ratios at the whole-head level, left and right hemispheres were observed in the ASD subgroup without visual EEG abnormality only (Bonferroni-corrected ps < .001), which remained highly significant when only data from medication-naïve participants were analyzed. In addition, higher left hemispheric fE/I ratios in ASD individuals without visual EEG abnormality were significantly correlated with faster interference control task performance, in turn faster reaction time was significantly associated with less severe restricted, repetitive behavior (Bonferroni-corrected ps ≤ .0017). ConclusionsDifferential theta-band fE/I within the ASD population. Heightened theta-band fE/I in ASD without visual EEG abnormality may be associated with more efficient filtering of distractors and a less severe ASD symptom manifestation. SignificanceBrain signaling, indicated by theta-band fE/I, was different in ASD subgroups. Only ASD with visually-normal EEG showed heightened theta-band fE/I, which was associated with faster processing of visual distractors during a cognitive task. More efficient distractor filtering was associated with less restricted, repetitive behaviors.

Investigating silent pauses in connected speech: integrating linguistic, neuropsychological, and neuroanatomical perspectives across narrative tasks in post-stroke aphasia.

Silent pauses are regarded as integral components of the temporal organization of speech. However, it has also been hypothesized that they serve as markers for internal cognitive processes, including word access, monitoring, planning, and memory functions. Although existing evidence across various pathological populations underscores the importance of investigating silent pauses' characteristics, particularly in terms of frequency and duration, there is a scarcity of data within the domain of post-stroke aphasia. The primary objective of the present study is to scrutinize the frequency and duration of silent pauses in two distinct narrative tasks within a cohort of 32 patients with chronic post-stroke aphasia, in comparison with a control group of healthy speakers. Subsequently, we investigate potential correlation patterns between silent pause measures, i.e., frequency and duration, across the two narrative tasks within the patient group, their performance in neuropsychological assessments, and lesion data. Our findings showed that patients exhibited a higher frequency of longer-duration pauses in both narrative tasks compared to healthy speakers. Furthermore, within-group comparisons revealed that patients tended to pause more frequently and for longer durations in the picture description task, while healthy participants exhibited the opposite trend. With regard to our second research question, a marginally significant interaction emerged between performance in semantic verbal fluency and the narrative task, in relation to the location of silent pauses-whether between or within clauses-predicting the duration of silent pauses in the patient group. However, no significant results were observed for the frequency of silent pauses. Lastly, our study identified that the duration of silent pauses could be predicted by distinct Regions of Interest (ROIs) in spared tissue within the left hemisphere, as a function of the narrative task. Overall, this study follows an integrative approach of linguistic, neuropsychological and neuroanatomical data to define silent pauses in connected speech, and illustrates interrelations between cognitive components, temporal aspects of speech, and anatomical indices, while it further highlights the importance of studying connected speech indices using different narrative tasks.

Gait Function and its Association with Functional Independence, Quality of Life, and Community Reintegration in Stroke Survivors.

Background and Aims: The major outcome of stroke rehabilitation is the recovery of the ability to walk. However, a large proportion of stroke survivors are discharged to the community with gait deficiency which impairs their functional independence, and quality of life increasing the burden of care on caregivers especially their lack of functioning in the community. This study assessed the gait functional performance in community-dwelling stroke survivors and explored its association with functional independence, quality of life, and community reintegration in community-dwelling stroke survivors. Materials and methods: This study involved 115(59 males and 56 females) community-dwelling stroke survivors. Their gait functional performance was assessed using the 10-meter walk test (10MWT) while their functional independence was assessed with the functional independence measure (FIM). Their quality of life (QoL) was assessed using the Stroke-specific QoL scale while community functioning and productivity were assessed using the community integration questionnaire (CIQ). Their scores on the assessments were compared with the normative data of their age and sex-matched healthy individuals. Data was analysed using Spearman’s correlation coefficient and Chi-Square at p&lt;.05. Results: Participants’ ages ranged between 27 to 78 years (mean=60.48±37.84 years). More participants (56.7%) had right hemispheric lesions and 43.3% had lesions in the left hemisphere. Their gait function, functional independence performance, QoL, and community reintegration functions were significantly (p&lt;0.05) lower than their age and sex-matched normative data. There was a significant (p&lt;0.05) association and relationship between their gait functional performance and each of the functional independence performance, QoL, community reintegration, and productivity. Conclusion: Gait functional performance in community-dwelling stroke survivors is significantly lower than in age and sex-matched healthy individuals and it is significantly associated with low functional independence performance, low quality of life, poor community functioning, and lack of productivity in stroke survivors, Abnormal gait pattern is related to poor functional independence, poor quality of life and low productivity.

Roger Sperry, the maverick brain scientist who was haunted by psyche.

This paper describes the scientific figure of Roger Sperry as a maverick researcher, an original thinker who arrived at definitive notions about the working of the brain mostly by distancing himself from the prevalent views of his peers. After solving the riddle of the functions of the corpus callosum, he won a Nobel prize in physiology or medicine for identifying the different cognitive abilities of the disconnected right and left hemispheres of the human brain. He could have won another Nobel prize for his work on the prenatal formation of behavioral neuronal networks and their growth and development after birth. In the last part of his life, he fought a courageous but inconclusive battle for demonstrating that mental and spiritual factors can direct brain activity and behavior without violating the laws of orthodox neurophysiology. Some nodal points in his scientific career and some sources of inspirations for his thinking are identified and discussed within the historical background of the neurosciences of the twentieth century.

Effects of Functional Electrical Stimulation on Attention and Brain Activity in Healthy Participants Using Near-Infrared Spectroscopy: An Interventional Study.

Background Involuntary limb activation using functional electrical stimulation (FES) can improve unilateral spatial neglect. However, the impact of FES on brain activity related to spatial attention remains unclear. Thus, in this study, we aimed to examine the effects of FES on spatial attention. Methodology In this interventional study, 13 healthy right-handed participants were asked to perform the Posner task for six minutes both before and after either FES or sham stimulation during each set, resulting in a total of two sets. FES was applied to the left forearm extensor muscles, with a frequency of 25 Hz, a pulse width of 100 μs, and the intensity adjusted to reach the motor threshold. Both the energization and pause times were set to five seconds. The Posner task was used to measure reaction time to a target appearing on a computer screen. Brain activity, indicated by oxygenated hemoglobin values, was measured using near-infrared spectroscopy with 24 probes according to the International 10-20 system method. Results In the left hemisphere, oxygenated hemoglobin values in the premotor and supplementary motor areas, primary somatosensory cortex, and somatosensory association areas were significantly higher after FES than after sham stimulation. In the right hemisphere, oxygenated hemoglobin values were significantly increased in the premotor, primary, and supplementary motor areas; in the supramarginal gyrus; and in the somatosensory association areas after FES. Reaction times in the Posner task did not differ significantly between the FES and sham conditions. Conclusions Collectively, these results suggest that FES of the upper limbs can activate the ventral pathway of the visual attention network and improve stimulus-driven attention. Activation of stimulus-driven attentional function could potentially contribute to symptom improvement in patients with unilateral spatial neglect.

Reading and Writing Impairment in Persons with Crossed Aphasia: A Comparative Study

Abstract Background Persons with aphasia (PWAs) manifest multifaceted deficits like auditory comprehension, spoken language, reading, and writing to varying degrees. Of these, the most debilitating signs are reading and writing impairment. Of late, PWAs express greater interest to improve their reading and writing skills. The deficits in these skills along with deficits in spoken language limit their participation in the community. Reading and writing may be altered contrarily in various stroke conditions across the left and right hemisphere lesions, just like how linguistic impairments are mutually exclusive. Thus, it must be rational to reconcile the possible role of the right hemisphere to process reading and writing inversely alike spoken abilities. Additionally, investigations on reading and writing deficits in left cerebrovascular atrophy (CVA) aphasics and right CVA aphasics (crossed aphasia) are seldom reported in the literature with relevance to Indian population focusing Indian languages. The study aims to compare reading and writing abilities across PWAs with left CVA and right CVA (crossed aphasia). Methodology The study recruited four native Kannada speaking PWAs (6 months poststroke) aged between 40 and 70 years with impaired linguistic abilities secondary to stroke through convenient sampling. Western Aphasia Battery-Kannada was administered to identify aphasic component, specifically to evaluate the language, reading, and writing aspects in detail and the scores were analyzed based on the scoring. Results Descriptive statistics revealed both left and crossed PWAs performed equipotent on linguistics tasks. However, reading abilities were better in left CVA individuals and writing was better in crossed PWAs on comparing the mean scores. Correlation analysis revealed positive correlation between language and reading-writing abilities of left CVA PWAs. Negative correlation was evinced in crossed PWAs. Hence, reading and writing difficulties in crossed aphasia can be mostly ascribed to impairment in peripheral mechanisms involved in visual and/or kinesthetic information processing as the right hemisphere is most viable to these processes. Conclusion The study highlights the unique pattern of reading and writing abilities in crossed aphasia condition. However, careful examination of dissociations in acquired spoken language and written language abilities across differential neuronal networks through larger samples in the future research is warranted.

Neurodevelopmental trajectories of cerebellar grey matter associated with verbal abilities in males with autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental condition frequently associated with structural cerebellar abnormalities. Whether cerebellar grey matter volumes (GMV) are linked to verbal impairments remains controversial. Here, the association between cerebellar GMV and verbal abilities in ASD was examined across the lifespan. Lobular segmentation of the cerebellum was performed on structural MRI scans from the ABIDE I dataset in male individuals with ASD (N=144, age: 8.5–64.0 years) and neurotypical controls (N=188; age: 8.0–56.2 years). Stepwise linear mixed effects modeling including group (ASD vs. neurotypical controls), lobule-wise GMV, and age was performed to identify cerebellar lobules which best predicted verbal abilities as measured by verbal IQ (VIQ). An age-specific association between VIQ and GMV of bilateral Crus II was found in ASD relative to neurotypical controls. In children with ASD, higher VIQ was associated with larger GMV of left Crus II but smaller GMV of right Crus II. By contrast, in adults with ASD, higher VIQ was associated with smaller GMV of left Crus II and larger GMV of right Crus II. These findings indicate that relative to the contralateral hemisphere, an initial reliance on the language-nonspecific left cerebellar hemisphere is offset by more typical right-lateralization in adulthood.

Secondary cerebro-cerebellar and intra-cerebellar dysfunction in cerebellar mutism syndrome.

Cerebellar mutism syndrome (CMS) is characterized by deficits of speech, movement, and affect that can occur following tumor removal from the posterior fossa. The role of cerebro-cerebellar tract injuries in the etiology of CMS remains unclear, with recent studies suggesting that cerebro-cerebellar dysfunction may be related to chronic, rather than transient, symptomatology. We measured functional connectivity between the cerebellar cortex and functional nodes throughout the brain using fMRI acquired after tumor removal but prior to adjuvant therapy in a cohort of 70 patients diagnosed with medulloblastoma. Surgical lesions were mapped to the infratentorial anatomy, and connectivity with cerebral cortex was tested for statistical dependence on extent of cerebellar outflow pathway injury. CMS diagnosis was associated with an increase in connectivity between the right cerebellar and left cerebral hemisphere, maximally between cerebellum and ventromedial prefrontal cortex (VM-PFC). Connectivity dependence on cerebellar outflow was significant for some speech nodes but not for VM-PFC, suggesting altered input to the cerebellum. Connectivity between posterior regions of cerebellar cortex and ipsilateral dentate nuclei was abnormal in CMS participants, maximally within the right cerebellar hemisphere. The functional abnormalities we identified are notably upstream of where causal surgical injury is thought to occur, indicating a secondary phenomenon. The VM-PFC is involved in several functions that may be relevant to the symptomatology of CMS, including emotional control and motor learning. We hypothesize that these abnormalities may reflect maladaptive learning within the cerebellum consequent to disordered motor and limbic function by the periaqueductal gray and other critical midbrain targets.