The lateralization and distalization index is more reliable than angular radiographic measurements in reverse shoulder arthroplasty.

BACKGROUND: The lateralization shoulder angle (LSA) and distalization shoulder angle (DSA) are used to reproducibly measure lateralization and distalization after reverse shoulder arthroplasty (RSA). However, LSA and DSA may not offer a precise measurement of humeral lateralization and distalization and this relationship has not been explored. The aim of this study was to evaluate the validity of these measurements and to propose new measurement methods to estimate implant lateralization and distalization. METHODS: 3D models were constructed from computed tomography (CT) scans of 30 patients using a software platform. For each patient 24 different RSA modifications were created, resulting in 720 different RSA configurations. For each configuration LSA and DSA angles as well as lateralization and distalization distances were measured. Moreover, for each configuration two new measurements were done: the lateralization index (LI) and distalization index (DI). Correlations of the lateralization and distalization parameters were evaluated between measurements. RESULTS: Weak correlations were founded between LSA and lateralization (r = 0.36, p < 0.01), whereas moderate correlations were observed between LI and lateralization (r = 0.72, p < 0.01). No significant correlations were found between DSA and distalization (r = 0.17, p = 0.113). In contrast, moderate correlations were identified between DI and distalization (r = 0.69, p < 0.01). CONCLUSION: LI and DI are more reliable methods to estimate implant lateralization and distalization compared to angular radiographic measurements. However, the prognostic significance in predicting clinical outcomes after RSA remains unknown.

Tapping for love: courtship, mating, and behavioral asymmetry in two aphid parasitoids, Aphidius ervi and Aphidius matricariae (Hymenoptera: Braconidae: Aphidinae).

Understanding the biology and ecology of parasitoids can have direct implications for their evaluation as biological control agents, as well as for the development and implementation of mass-rearing techniques. Nonetheless, our current knowledge of the possible influence of lateralized displays (i.e., the asymmetric expression of cognitive functions) on their reproductive behavior is scarce. Herein, we characterized the behavioral elements involved in courtship, and quantified the durations of 2 important aphid parasitoids, Aphidius ervi Haliday and Aphidius matricariae Haliday (Hymenoptera: Braconidae: Aphidiinae). We quantified the main indicators of copulation and examined the occurrence of lateralized traits at population level. Results indicated that A. matricariae exhibited longer durations of wing fanning, antennal tapping, pre-copula and copula phases compared to A. ervi. Postcopulatory behavior was observed only in A. matricariae. Unlike other parasitoid species, the duration of wing fanning, chasing, and antennal tapping did not affect the success of the mating of male A. ervi and A. matricariae. Both species exhibited a right-biased female kicking behavior at the population level during the pre-copula. Our study provides insights into the fundamental biology of aphidiine parasitoids and reports the presence of population-level lateralized mating displays, which can serve as useful benchmarks to evaluate the quality of mass-rearing systems.

A meta-analytical account of the functional lateralization of the reading network.

The observation that the neural correlates of reading are left-lateralized is ubiquitous in the cognitive neuroscience and neuropsychological literature. Still, reading is served by a constellation of neural units, and the extent to which these units are consistently left-lateralized is unclear. In this regard, the functional lateralization of the fusiform gyrus is of particular interest, by virtue of its hypothesized role as a "visual word form area". A quantitative Activation Likelihood Estimation meta-analysis was conducted on activation foci from 35 experiments investigating silent reading, and both a whole-brain and a bayesian ROI-based approach were used to assess the lateralization of the data submitted to meta-analysis. Perirolandic areas showed the highest level of left-lateralization, the fusiform cortex and the parietal cortex exhibited only a moderate pattern of left-lateralization, while in the occipital, insular cortices and in the cerebellum the lateralization turned out to be the lowest observed. The relatively limited functional lateralization of the fusiform gyrus was further explored in a regression analysis on the lateralization profile of each study. The functional lateralization of the fusiform gyrus during reading was positively associated with the lateralization of the precentral and inferior occipital gyri and negatively associated with the lateralization of the triangular portion of the inferior frontal gyrus and of the temporal pole. Overall, the present data highlight how lateralization patterns differ within the reading network. Furthermore, the present data highlight how the functional lateralization of the fusiform gyrus during reading is related to the degree of functional lateralization of other language brain areas.

Dual Representation of the Auditory Space.

Auditory spatial cues contribute to two distinct functions, of which one leads to explicit localization of sound sources and the other provides a location-linked representation of sound objects. Behavioral and imaging studies demonstrated right-hemispheric dominance for explicit sound localization. An early clinical case study documented the dissociation between the explicit sound localizations, which was heavily impaired, and fully preserved use of spatial cues for sound object segregation. The latter involves location-linked encoding of sound objects. We review here evidence pertaining to brain regions involved in location-linked representation of sound objects. Auditory evoked potential (AEP) and functional magnetic resonance imaging (fMRI) studies investigated this aspect by comparing encoding of individual sound objects, which changed their locations or remained stationary. Systematic search identified 1 AEP and 12 fMRI studies. Together with studies of anatomical correlates of impaired of spatial-cue-based sound object segregation after focal brain lesions, the present evidence indicates that the location-linked representation of sound objects involves strongly the left hemisphere and to a lesser degree the right hemisphere. Location-linked encoding of sound objects is present in several early-stage auditory areas and in the specialized temporal voice area. In these regions, emotional valence benefits from location-linked encoding as well.

Atypical lateralization of visuospatial attention can be associated with better or worse performance on line bisection.

The causal and statistical hypotheses diverge in determining whether the lateralization of language function in one cerebral hemisphere entails the lateralization of visuospatial function in the opposite hemisphere. Additionally, it remains unclear if the atypical segregation of these functions could influence cognitive performance. This study addresses these questions by examining the hemispheric lateralization of visuospatial attention during a line bisection judgement (landmark) task in three groups of healthy non-right-handed individuals with different language production segregations: left (typical), ambilateral (atypical), and right (atypical). Consistent with the causal hypothesis, results indicate that the groups with left and right language lateralization primarily utilize the opposite hemisphere for visuospatial attention. The ambilateral group, however, displays a pattern compatible with an independent segregation, supporting the statistical hypothesis. Behavioral analyses reveal that atypical lateralization of visuospatial attention (non-right) can lead to either better or worse performance during the landmark task, depending on the specific pattern. Bilateral organization is associated with reduced overall accuracy, whereas the left segregation results in improved performance during the most challenging trials. These findings suggest the existence of diverse pathways to lateralization, akin to either the causal or statistical hypothesis, which can result in cognitive advantages or disadvantages.

Compensation or Preservation? Different Roles of Functional Lateralization in Speech Perception of Older Non-musicians and Musicians.

Musical training can counteract age-related decline in speech perception in noisy environments. However, it remains unclear whether older non-musicians and musicians rely on functional compensation or functional preservation to counteract the adverse effects of aging. This study utilized resting-state functional connectivity (FC) to investigate functional lateralization, a fundamental organization feature, in older musicians (OM), older non-musicians (ONM), and young non-musicians (YNM). Results showed that OM outperformed ONM and achieved comparable performance to YNM in speech-in-noise and speech-in-speech tasks. ONM exhibited reduced lateralization than YNM in lateralization index (LI) of intrahemispheric FC (LI_intra) in the cingulo-opercular network (CON) and LI of interhemispheric heterotopic FC (LI_he) in the language network (LAN). Conversely, OM showed higher neural alignment to YNM (i.e., a more similar lateralization pattern) compared to ONM in CON, LAN, frontoparietal network (FPN), dorsal attention network (DAN), and default mode network (DMN), indicating preservation of youth-like lateralization patterns due to musical experience. Furthermore, in ONM, stronger left-lateralized and lower alignment-to-young of LI_intra in the somatomotor network (SMN) and DAN and LI_he in DMN correlated with better speech performance, indicating a functional compensation mechanism. In contrast, stronger right-lateralized LI_intra in FPN and DAN and higher alignment-to-young of LI_he in LAN correlated with better performance in OM, suggesting a functional preservation mechanism. These findings highlight the differential roles of functional preservation and compensation of lateralization in speech perception in noise among elderly individuals with and without musical expertise, offering insights into successful aging theories from the lens of functional lateralization and speech perception.

Neuro-cardiac-guided transcranial magnetic stimulation: Unveiling the modulatory effects of low-frequency and high-frequency stimulation on heart rate.

Transcranial magnetic stimulation (TMS) is pivotal in the field of major depressive disorder treatment. Due to its unsatisfied response rate, an increasing number of researchers have turned their attention towards optimizing TMS site localization. Since the influence of TMS in reducing heart rate (HR) offers insights into its regulatory impact on the autonomic nervous system, a novel approach, called neurocardiac-guided TMS (NCG-TMS), has been proposed to pinpoint the brain region eliciting the maximal individual reduction in HR as a personalized optimal stimulation target. The present study intends to systematically explore the effects of stimulation frequency, left and right hemispheres, stimulation positions, and individual differences on HR modulation using the NCG-TMS method. In experiment 1, low-frequency TMS was administered to 30 subjects, and it was found that low-frequency NCG-TMS significantly downregulated HR, with more significant effects in the right hemisphere than in the left hemisphere and the prefrontal cortex than in other brain areas. In experiment 2, high-frequency NCG-TMS stimulation was administered to 30 subjects, showing that high-frequency NCG-TMS also downregulated HR and had the greatest modulatory effect in the right prefrontal region. Simultaneously, both experiments revealed sizeable individual variability in the optimal stimulation site, which in turn validated the feasibility of the NCG-TMS method. In conclusion, the present experiments independently replicated the effect of NCG-TMS, provided an effect of high-/low-frequency TMS stimulation to downregulate HR, and identified a right lateralization of the HR modulation effect.

Nasal axis lateralization suture technique in crooked nose.

PURPOSE: The aim of the present study was to objectively and subjectively compare the preoperative and postoperative aesthetic and functional outcomes of the correction of crooked noses using a suture technique we call "nasal axis lateralization suture (NALS)". METHOD: A total of 36 patients who had preoperative and postoperative photographs taken and who completed the Rhinoplasty Outcome Evaluation (ROE) questionnaire were included in the study. RESULTS: Crooked noses were divided into two groups: C-shaped (17 patients) and I-shaped (19 patients). The preoperative and postoperative nasal axis angles were 145.3 ± 11.9 and 178.5 ± 3.3, respectively, in C-shaped nasal deviation. In I-shaped nasal deviation, on the other hand, the preoperative nasal axis angle was 8.8 ± 2.8, while the postoperative nasal axis angle was 1.4 ± 2.4. In terms of the ideal axis percentage before and after surgery, a significant difference was found between the C-shaped and I-shaped nasal deviation patient groups (p < 0.05). While there was a significant improvement in both groups in the evaluation based on the ROE questionnaire, satisfaction was much higher in the C-shaped nasal deviation group. In both groups, the ROE values of functional and aesthetic outcomes were significantly different compared to the preoperative values of both groups (p < 0.005). CONCLUSION: NALS can be used as an alternative technique to correct both I-shaped and C-shaped nasal axis deviations.

A new approach to quantify asymmetry in human movement.

In this perspective paper, we propose a new approach to quantify the asymmetries in human movement. Before describing this approach, we delve into the asymmetry in human movement, often defined as the opposite of symmetry, and its implications for studying human movement. We critically examine the various methods available to quantify and describe bilateral differences, from arbitrary thresholds (such as the commonly employed 10-15% difference) to the measure of the smallest meaningful changes, and we stress the need for consideration of interindividual variability in the analysis. Our proposal centers on a straightforward metric, the probability of agreement, and a corresponding plot summarizing the agreement between measures from two limbs. Critically, the agreement between two limbs depends on the value of the clinically acceptable difference. The agreement will increase with larger values of clinically acceptable difference and decrease with smaller values of clinically acceptable difference. Data from various movements and conditions in athletes' sports training and rehabilitation are used to illustrate this approach. Our perspective provides valuable insights into the nature of asymmetry in human movement, considering that a rational understanding of asymmetry in human movement requires a thoughtful approach encompassing both statistical and clinical significance. The data and codes employed in our research are openly accessible in the supplementary materials, enabling others in the field to replicate and build upon our findings.

Bayesian modelling disentangles language versus executive control disruption in stroke.

Stroke is the leading cause of long-term disability worldwide. Incurred brain damage can disrupt cognition, often with persisting deficits in language and executive capacities. Yet, despite their clinical relevance, the commonalities and differences between language versus executive control impairments remain under-specified. To fill this gap, we tailored a Bayesian hierarchical modelling solution in a largest-of-its-kind cohort (1080 patients with stroke) to deconvolve language and executive control with respect to the stroke topology. Cognitive function was assessed with a rich neuropsychological test battery including global cognitive function (tested with the Mini-Mental State Exam), language (assessed with a picture naming task), executive speech function (tested with verbal fluency tasks), executive control functions (Trail Making Test and Digit Symbol Coding Task), visuospatial functioning (Rey Complex Figure), as well as verbal learning and memory function (Soul Verbal Learning). Bayesian modelling predicted interindividual differences in eight cognitive outcome scores three months after stroke based on specific tissue lesion topologies. A multivariate factor analysis extracted four distinct cognitive factors that distinguish left- and right-hemispheric contributions to ischaemic tissue lesions. These factors were labelled according to the neuropsychological tests that had the strongest factor loadings: One factor delineated language and general cognitive performance and was mainly associated with damage to left-hemispheric brain regions in the frontal and temporal cortex. A factor for executive control summarized mental flexibility, task switching and visual-constructional abilities. This factor was strongly related to right-hemispheric brain damage of posterior regions in the occipital cortex. The interplay of language and executive control was reflected in two distinct factors that were labelled as executive speech functions and verbal memory. Impairments on both factors were mainly linked to left-hemispheric lesions. These findings shed light onto the causal implications of hemispheric specialization for cognition; and make steps towards subgroup-specific treatment protocols after stroke.

Precision fMRI reveals that the language network exhibits adult-like left-hemispheric lateralization by 4 years of age.

Left hemisphere damage in adulthood often leads to linguistic deficits, but many cases of early damage leave linguistic processing preserved, and a functional language system can develop in the right hemisphere. To explain this early apparent equipotentiality of the two hemispheres for language, some have proposed that the language system is bilateral during early development and only becomes left-lateralized with age. We examined language lateralization using functional magnetic resonance imaging with two large pediatric cohorts (total n=273 children ages 4-16; n=107 adults). Strong, adult-level left-hemispheric lateralization (in activation volume and response magnitude) was evident by age 4. Thus, although the right hemisphere can take over language function in some cases of early brain damage, and although some features of the language system do show protracted development (magnitude of language response and strength of inter-regional correlations in the language network), the left-hemisphere bias for language is robustly present by 4 years of age. These results call for alternative accounts of early equipotentiality of the two hemispheres for language.

Emergence of a left-right symmetric body plan in vertebrate embryos.

External bilateral symmetry is a prevalent feature in vertebrates, which emerges during early embryonic development. To begin with, vertebrate embryos are largely radially symmetric before transitioning to bilaterally symmetry, after which, morphogenesis of various bilateral tissues (e.g somites, otic vesicle, limb bud), and structures (e.g palate, jaw) ensue. While a significant amount of work has probed the mechanisms behind symmetry breaking in the left-right axis leading to asymmetric positioning of internal organs, little is known about how bilateral tissues emerge at the same time with the same shape and size and at the same position on the two sides of the embryo. By discussing emergence of symmetry in many bilateral tissues and structures across vertebrate model systems, we highlight that understanding symmetry establishment is largely an open field, which will provide deep insights into fundamental problems in developmental biology for decades to come.

Asymmetry of max grip force and max rate of grip force development among adolescents with and without intellectual disability.

The human body seems symmetrical but functional asymmetry can be observed for many tasks. One of the tasks observed the functional asymmetry is grip force and rate of grip force development (RGFD). To efficiently accomplish many tasks, it is important to measure those parameters in different ages and special groups. Thus, the purpose of the study was to test asymmetry of max grip force and max RGFD among adolescents with and without intellectual disability. 41 adolescents with (IQ between 50 and 70) and 41 adolescents without intellectual disability voluntarily participated to the study. Max grip force and max RGFD was measured using a force transducer with custom-made software. The statistical analysis displayed that adolescents without intellectual disability had higher max grip force and max RGFD with their both hands compared to adolescent with intellectual disability. Interestingly, whereas adolescent without intellectual disability displayed an asymmetry between the hands both for max grip force and max RGFD, adolescents with intellectual disability had asymmetry only for max grip force but not for max RGFD. Thus, adolescents with intellectual disability may have symmetrical neurological pathways. Individuals with intellectual disability should be provided with more physical activity and/or exercise opportunities including the bimanual movements with fast and ballistic actions.

Rates of subacromial notching are low following reverse shoulder arthroplasty with a 135° inlay humeral component and a lateralized glenoid.

Background: Lateralization in reverse shoulder arthroplasty (RSA) decreases bony impingement and improves rotational range of motion, but has been theorized to increase the risk of subacromial notching (SaN). The purpose of this study was to evaluate the presence of SaN following RSA and its relationship with lateralization with a 135° inlay humeral component. The secondary purpose was to assess the association of SaN with functional outcomes. Methods: A retrospective review was performed from a multicenter prospectively collected database on patients who underwent primary RSA from 2015 to 2021. All RSAs were performed with a 135° inlay humeral component. SaN was defined as bony erosion with sclerotic margins on the undersurface of the acromion on final follow-up radiographs not present preoperatively. Postoperative implant positioning (inclination, distalization, and lateralization) were evaluated on minimum 1-year postoperative radiographs. Regression analyses were performed on implant and clinical variables to assess for risk factors. A separate analysis was performed to determine the association of SaN with clinical outcomes. Results: SaN was identified in 13 out of 442 shoulders (2.9%). Age, sex, body mass index, smoking status, diabetes mellitus, arm dominance had no relationship with SaN. Neither glenoid sided lateralization nor humeral offset were associated with SaN risk. Other implant characteristics such as distalization, glenosphere size, and postoperative inclination did not influence SaN risk. The presence of SaN did not affect patient-reported outcomes (American Shoulder and Elbow Surgeons: P = .357, Visual Analog Scale: P = .210) or range of motion. Conclusion: The rate of SaN is low and not associated with glenoid or humeral prosthetic lateralization when using a 135° inlay humeral component. When SaN occurs, it is not associated with functional outcomes or range of motion at short-term follow-up.

Assessing Lateralization Index of Adrenal Venous Sampling for Surgical Indication in Primary Aldosteronism.

BACKGROUND: Clinical practice guidelines recommend the Lateralization Index (LI) as the standard for determining surgical eligibility in primary aldosteronism (PA). Our goal was to identify the optimal LI cut-offs in adrenal venous sampling (AVS) for diagnosing PA that is amenable to surgical cure. METHODS: We conducted a retrospective international cohort study across 16 institutions in 11 countries, including 1,550 patients with PA who underwent AVS, with and/or without ACTH stimulation. The establishment of optimal cut-offs was informed by a survey of 82 PA patients in Japan, aimed at determining the LI cut-off aligned with patient expectations for a surgical cure rate. RESULTS: The survey revealed that a median cure rate expectation of 80% would motivate PA patients towards undergoing adrenalectomy. The optimal LI cut-offs achieving an adjusted positive predictive value (PPV) of 80% were identified as 3.8 for unstimulated AVS and 3.4 for ACTH-stimulated AVS. Furthermore, a contralateral ratio of less than 0.4 and the detection of an adrenal nodule on CT imaging were identified as independent predictors of surgically curable PA. Incorporating these factors with the optimal LI cut-offs, the adjusted PPV increased to 96.6% for unstimulated AVS and 89.6% for ACTH-stimulated AVS. No clear differences in predictive ability between unstimulated and ACTH-stimulated LI were found. CONCLUSIONS AND RELEVANCE: The present study clarified the optimal LI cut-offs for without and with ACTH stimulation. The presence of contralateral suppression and adrenal nodule on CT imaging seems to provide additional available information besides LI for surgical indication.

The Effect of Lateralization and Distalization After Grammont-Style Reverse Total Shoulder Arthroplasty.

BACKGROUND: The purpose of this study is to evaluate the relationship between multiple radiographic measures of lateralization and distalization and clinical outcome scores after reverse total shoulder arthroplasty (RTSA). METHODS: We retrospectively evaluated all RTSAs performed by the senior author between January 1, 2007, and November 1, 2017. We then evaluated the visual analog scale for pain (VAS pain), Simple Shoulder Test (SST), and American Shoulder and Elbow Surgeons (ASES) scores and complication and reoperation rates at a minimum of 2-year follow-up. We measured preoperative and postoperative (2-week) radiographs for the lateralization shoulder angle (LSA), the distalization shoulder angle (DSA), lateral humeral offset (LHO), and distance from glenoid to lateral aspect of the greater tuberosity (GLAGT). A multivariable analysis was performed evaluating the effect of the postoperative radiographic measurements on final patient reported outcomes (ASES scores, SST, VAS pain). RESULTS: The cohort included 216 shoulders from unique patients who had patient reported outcome scores available at a minimum of 2-year follow-up (average, 4.0±1.9 years) for a total follow-up rate of 70%. In the multivariable models, more lateralization (LSA) was associated with worse final ASES scores -0.52 (95% CI: -0.88 to -0.17; p=0.004), and more distalization (DSA) was associated with better final ASES scores 0.40 (95% CI: 0.11, 0.69; p=0.007). More lateralization (LSA) was associated with worse final SST scores -0.06 (95% CI: -0.11, -0.003; p=0.039). Finally, greater distalization (DSA) was associated with lower final VAS pain scores, Ratio = 0.98 (95% CI: 0.96, 1.00; p=0.021). CONCLUSION: Greater distalization and less lateralization are associated with better function and less pain after Grammont-style RTSA. If utilizing a Grammont-style implant, remaining consistent with Grammont's principles of implant placement will afford better final clinical outcomes.

Lateralization of the Humerus in Reverse Total Shoulder Arthroplasty: Can Preoperative Planning Software Predict Postoperative Lateralization and Does Lateralization Influence Outcomes?

INTRODUCTION: Reverse total shoulder arthroplasty (RTSA) can result in varying amounts of humeral medialization or lateralization. The amount of medial or lateral change-in-arm-position can be predicted using 3D CT planning software. It is not clear if the preoperatively-predicted change-in-arm-position correlates with the actual, radiographically-measured change-in-arm-position or if predicted or actual change-in-arm-position correlates with patient-reported outcomes or complications. METHODS: Patients undergoing RTSA underwent preoperative 3D CT planning to predict the postoperative medial-to-lateral change-in-arm-position (PCAP). Preoperative and postoperative radiographs were used to calculate the actual medial-to-lateral change-in-arm-position using the measurement of the lateral edge of the greater tuberosity to the lateral edge of the acromion (RCAP-LHO). The Western Ontario Osteoarthritis Score (WOOS), American Shoulder and Elbow Surgeons score (ASES) and Single Assessment Numeric Evaluation (SANE) were recorded at baseline, 1-year, and 2-years. Rates of complications were recorded. RESULTS: Two-hundred-and-fifty patients were eligible for this study including 189 patients reaching the one-year clinical follow-up point and 144 patients reaching the two-year clinical follow-up point. One-year and two-year follow-up rates were 89 percent and 91 percent, respectively. The mean PCAP was 3+5 mm and RCAP-LHO was 1+8 mm. There was moderate correlation between PCAP and RCAP-LHO. There was weak correlation between increased PCAP lateralization and higher WOOS and ASES at two years and improvement from baseline to 2 years in WOOS. There was very weak correlation between increased PCAP lateralization and improvement compared to baseline in 1 year SANE and improvement compared to baseline in 2 year SANE. There was weak correlation between lateralized RCAP-LHO and 2 year postoperative SANE. There was superior 2-year WOOS, ASES, and SANE, and improvement in SANE at 1-year compared to baseline in patients with a lateralized PCAP compared to a medialized or neutral PCAP. There was superior 2-year WOOS, improvement in WOOS from baseline to 2-year follow-up, and SANE at 2-years in patients with a lateralized RCAP-LHO compared to a medialized or neutral RCAP-LHO. Overall complication rates were similar between groups although the dislocation rate in shoulders with a lateralized change-in-arm-position was significantly less compared to shoulders with a medial or neutral change-in-arm-position. CONCLUSIONS: PCAP correlated with actual RCAP-LHO. Correlations exist with increased humeral lateralization and improved patient-determined outcomes. Patient-determined outcomes were the same or better in patients with a lateralized change-in-arm-position compared to those that were medialized or remained neutral. A lateralized change-in-arm-position did not result in increased overall complications and was protective against postoperative instability.

Interhemispheric functional connectivity: an fMRI study in callosotomized patients.

Introduction: Functional connectivity (FC) is defined in terms of temporal correlations between physiological signals, which mainly depend upon structural (axonal) connectivity; it is commonly studied using functional magnetic resonance imaging (fMRI). Interhemispheric FC appears mostly supported by the corpus callosum (CC), although several studies investigating this aspect have not provided conclusive evidence. In this context, patients in whom the CC was resected for therapeutic reasons (split-brain patients) provide a unique opportunity for research into this issue. The present study was aimed at investigating with resting-state fMRI the interhemispheric FC in six epileptic patients who have undergone surgical resection of the CC. Methods: The analysis was performed using fMRI of the Brain Software Library; the evaluation of interhemispheric FC and the recognition of the resting-state networks (RSNs) were performed using probabilistic independent component analysis. Results: Generally, bilateral brain activation was often observed in primary sensory RSNs, while in the associative areas, such as those composing the default mode and fronto-parietal networks, the activation was often unilateral. Discussion: These results suggest that even in the absence of the CC, some interhemispheric communication is still present. This residual FC might be supported through extra-callosal pathways that are likely subcortical, making it possible for some interhemispheric integration. Further studies are needed to confirm these conclusions.