Learning redundant motor tasks with and without overlapping dimensions: facilitation and interference effects.

Prior learning of a motor skill creates motor memories that can facilitate or interfere with learning of new, but related, motor skills. One hypothesis of motor learning posits that for a sensorimotor task with redundant degrees of freedom, the nervous system learns the geometric structure of the task and improves performance by selectively operating within that task space. We tested this hypothesis by examining if transfer of learning between two tasks depends on shared dimensionality between their respective task spaces. Human participants wore a data glove and learned to manipulate a computer cursor by moving their fingers. Separate groups of participants learned two tasks: a prior task that was unique to each group and a criterion task that was common to all groups. We manipulated the mapping between finger motions and cursor positions in the prior task to define task spaces that either shared or did not share the task space dimensions (x-y axes) of the criterion task. We found that if the prior task shared task dimensions with the criterion task, there was an initial facilitation in criterion task performance. However, if the prior task did not share task dimensions with the criterion task, there was prolonged interference in learning the criterion task due to participants finding inefficient task solutions. These results show that the nervous system learns the task space through practice, and that the degree of shared task space dimensionality influences the extent to which prior experience transfers to subsequent learning of related motor skills.

Radiomics Features in Predicting Human Papillomavirus Status in Oropharyngeal Squamous Cell Carcinoma: A Systematic Review, Quality Appraisal, and Meta-Analysis.

We sought to determine the diagnostic accuracy of radiomics features in predicting HPV status in oropharyngeal squamous cell carcinoma (SCC) compared to routine paraclinical measures used in clinical practice. Twenty-six articles were included in the systematic review, and thirteen were used for the meta-analysis. The overall sensitivity of the included studies was 0.78, the overall specificity was 0.76, and the overall area under the ROC curve was 0.84. The diagnostic odds ratio (DOR) equaled 12 (8, 17). Subgroup analysis showed no significant difference between radiomics features extracted from CT or MR images. Overall, the studies were of low quality in regard to radiomics quality score, although most had a low risk of bias based on the QUADAS-2 tool. Radiomics features showed good overall sensitivity and specificity in determining HPV status in OPSCC, though the low quality of the included studies poses problems for generalizability.

Schwannomatosis: the overlooked neurofibromatosis?

OBJECTIVE: Schwannomas are typically benign tumors that occur sporadically, in neurofibromatosis type 2 (NF2), or in an entity called "schwannomatosis." Schwannomatosis patients develop multiple schwannomas without involvement of the vestibular apparatus. Geneticists, neurologists, and pathologists have recognized that schwannomatosis is distinct from NF2, but schwannomatosis remains unfamiliar to many radiologists. This article reviews the current medical literature, highlighting the similarities and differences between the schwannomatosis and NF2 phenotypes, genotypes, clinical manifestations, management considerations, and imaging findings. CONCLUSION: Imaging plays a critical role in diagnosing schwannomatosis, and a basic understanding of this syndrome is of interest to diagnostic radiologists. Moreover, it is imperative that radiologists be able to differentiate schwannomatosis from NF2 on imaging because there are significant differences in the management of these two diseases and clinical outcomes for affected patients.

Strategies to maximize resection of complex, or high surgical risk, low-grade gliomas.

OBJECT: Early and aggressive resection of low-grade gliomas (LGGs) leads to increased overall patient survival, decreased malignant progression, and better seizure control. This case series describes the authors' approach to achieving optimal neurological and surgical outcomes in patients referred by outside neurosurgeons for stereotactic biopsy of tumors believed to be complex or a high surgical risk, due to their diffuse nature on neuroimaging and their obvious infiltration of functional cortex. METHODS: Seven patients underwent individualized neuroimaging evaluation preoperatively, which included routine brain MRI with and without contrast administration for intraoperative neuronavigation, functional MRI with speech and motor mapping, diffusion tensor imaging to delineate white matter tracts, and MR perfusion to identify potential foci of higher grade malignancy within the tumor. Awake craniotomy with intraoperative motor and speech mapping was performed in all patients. Tumor removal was initiated through a transsylvian approach for insular lesions, and through multiple corticotomies in stimulation-confirmed noneloquent areas for all other lesions. Resection was continued until neuronavigation indicated normal brain, cortical or subcortical stimulation revealed functional cortex, or the patient began to experience a minor neurological deficit on intraoperative testing. RESULTS: Gross-total resection was achieved in 1 patient and subtotal resection (> 80%) in 6 patients, as assessed by postoperative MRI. Over the average follow-up duration of 31 months, no patient experienced a progression or recurrence. Long-term seizure control was excellent in 6 patients who achieved Engel Class I outcomes. Neurologically, all 7 patients experienced mild temporary deficits or seizures that completely resolved, and 1 patient continues to have mild expressive aphasia. CONCLUSIONS: Significant resection of diffuse, infiltrating LGGs is possible, even in presumed eloquent cortex. Aggressive resection maximizes seizure control and does not necessarily cause permanent neurological deficits. Individualized preoperative neuroimaging evaluation, including tractography and awake craniotomy with intraoperative speech and motor mapping, is an essential tool in achieving these outcomes.

Remembering forward: neural correlates of memory and prediction in human motor adaptation.

We used functional MR imaging (FMRI), a robotic manipulandum and systems identification techniques to examine neural correlates of predictive compensation for spring-like loads during goal-directed wrist movements in neurologically-intact humans. Although load changed unpredictably from one trial to the next, subjects nevertheless used sensorimotor memories from recent movements to predict and compensate upcoming loads. Prediction enabled subjects to adapt performance so that the task was accomplished with minimum effort. Population analyses of functional images revealed a distributed, bilateral network of cortical and subcortical activity supporting predictive load compensation during visual target capture. Cortical regions--including prefrontal, parietal and hippocampal cortices--exhibited trial-by-trial fluctuations in BOLD signal consistent with the storage and recall of sensorimotor memories or "states" important for spatial working memory. Bilateral activations in associative regions of the striatum demonstrated temporal correlation with the magnitude of kinematic performance error (a signal that could drive reward-optimizing reinforcement learning and the prospective scaling of previously learned motor programs). BOLD signal correlations with load prediction were observed in the cerebellar cortex and red nuclei (consistent with the idea that these structures generate adaptive fusimotor signals facilitating cancelation of expected proprioceptive feedback, as required for conditional feedback adjustments to ongoing motor commands and feedback error learning). Analysis of single subject images revealed that predictive activity was at least as likely to be observed in more than one of these neural systems as in just one. We conclude therefore that motor adaptation is mediated by predictive compensations supported by multiple, distributed, cortical and subcortical structures.

White matter abnormalities associated with disruptive behavior disorder in adolescents with and without attention-deficit/hyperactivity disorder.

Disruptive behavior disorders (DBD) are among the most commonly diagnosed mental disorders in children and adolescents. Some important characteristics of DBD vary based on the presence or absence of comorbid attention-deficit/hyperactivity disorder (ADHD), which may affect the understanding of and treatment decision-making related to the disorders. Thus, identifying neurobiological characteristics of DBD with comorbid ADHD (DBD+ADHD) can provide a basis to establish a better understanding of the condition. This study aimed to assess abnormal white matter microstructural alterations in DBD+ADHD as compared to DBD alone and healthy controls using diffusion tensor imaging (DTI). Thirty-three DBD (19 with comorbid ADHD) and 46 age-matched healthy adolescents were studied using DTI. Fractional anisotropy (FA), and mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AD) were analyzed using tract-based spatial statistics (TBSS). Significantly lower FA and higher MD, RD and AD in many white matter fibers were found in adolescents with DBD+ADHD compared to controls. Moreover, lower FA and higher RD were also found in the DBD+ADHD versus the DBD alone group. Alterations of white matter integrity found in DBD patients were primarily associated with ADHD, suggesting that ADHD comorbidity in DBD is reflected in greater abnormality of microstructural connections.

Automatic assessment of human gastric motility and emptying from dynamic 3D magnetic resonance imaging.

BACKGROUND: Time-sequenced magnetic resonance imaging (MRI) of the stomach is an emerging technique for non-invasive assessment of gastric emptying and motility. However, an automated and systematic image processing pipeline for analyzing dynamic 3D (ie, 4D) gastric MRI data has not been established. This study uses an MRI protocol for imaging the stomach with high spatiotemporal resolution and provides a pipeline for assessing gastric emptying and motility. METHODS: Diet contrast-enhanced MRI images were acquired from seventeen healthy humans after they consumed a naturalistic contrast meal. An automated image processing pipeline was developed to correct for respiratory motion, to segment and compartmentalize the lumen-enhanced stomach, to quantify total gastric and compartmental emptying, and to compute and visualize gastric motility on the luminal surface of the stomach. KEY RESULTS: The gastric segmentation reached an accuracy of 91.10 ± 0.43% with the Type-I error and Type-II error being 0.11 ± 0.01% and 0.22 ± 0.01%, respectively. Gastric volume decreased 34.64 ± 2.8% over 1 h where the emptying followed a linear-exponential pattern. The gastric motility showed peristaltic patterns with a median = 4 wave fronts (range 3-6) and a mean frequency of 3.09 ± 0.07 cycles per minute. Further, the contractile amplitude was stronger in the antrum than in the corpus (antrum vs. corpus: 5.18 ± 0.24 vs. 3.30 ± 0.16 mm; p < 0.001). CONCLUSIONS & INFERENCES: Our analysis pipeline can process dynamic 3D MRI images and produce personalized profiles of gastric motility and emptying. It will facilitate the application of MRI for monitoring gastric dynamics in research and clinical settings.

Regional reproducibility of pulsed arterial spin labeling perfusion imaging at 3T.

Arterial spin labeling (ASL) is a promising non-invasive magnetic resonance imaging (MRI) technique for measuring regional cerebral blood flow (rCBF) or perfusion in vivo. To evaluate the feasibility of ASL as a biomarker for clinical trials, it is important to examine test-retest reproducibility. We investigated both inter- and intra-session reproducibility of perfusion MRI using a pulsed ASL (PASL) sequence PICORE Q2TIPS with an echo-planar imaging (EPI) readout. Structural MRI regions of interest (ROIs) were extracted individually by automated parcellation and segmentation methods using FreeSurfer. These cortical and subcortical ROIs were used to assess regional perfusion stability. Our results indicated regional variability in grey matter rCBF. Although rCBF measurements were characterized by intersubject variation, our results also indicated relatively less within-subject variability estimated as within-subject standard deviation (SD(W)) (intersession SD(W): 2.0 to 8.8; intrasession SD(W): 2.8 to 9.6) and acceptable reliabilities as measured using intraclass correlation coefficient (ICC) (intersession ICC: 0.68 to 0.94; intrasession ICC: 0.66 to 0.95) for regional MRI perfusion measurements using the PICORE Q2TIPS technique. Overall, our findings suggest that PASL is a technique with good within and between session reproducibility. Further reproducibility studies in target populations relevant for specific clinical trials of neurovascular related agents will be important and the present results provide a framework for such assessments.

Controlling instabilities in manipulation requires specific cortical-striatal-cerebellar networks.

Dexterous manipulation requires both strength, the ability to produce fingertip forces of a specific magnitude, and dexterity, the ability to dynamically regulate the magnitude and direction of fingertip force vectors and finger motions. Although cortical activity in fronto-parietal networks has been established for stable grip and pinch forces, the cortical regulation in the dexterous control of unstable objects remains unknown. We used functional magnetic resonance imaging (fMRI) to interrogate cortical networks engaged in the control of four objects with increasing instabilities but requiring constant strength. In addition to expected activity in fronto-parietal networks we find that dexterous manipulation of increasingly unstable objects is associated with a linear increase in the amplitude of the BOLD signal in the basal ganglia (P = 0.007 and P = 0.023 for 2 compression tasks). A computational regression (connectivity) model identified independent subsets of cortical networks whose connection strengths were mutable and associated with object instability (P < 0.001). Our results suggest that in the presence of object instability, the basal ganglia may modulate the activity of premotor areas and subsequent motor output. This work, therefore, provides new evidence for the selectable cortical representation and execution of dynamic multifinger manipulation for grasp stability.

Reorganization of finger coordination patterns during adaptation to rotation and scaling of a newly learned sensorimotor transformation.

We examined how people organize redundant kinematic control variables (finger joint configurations) while learning to make goal-directed movements of a virtual object (a cursor) within a low-dimensional task space (a computer screen). Subjects participated in three experiments performed on separate days. Learning progressed rapidly on day 1, resulting in reduced target capture error and increased cursor trajectory linearity. On days 2 and 3, one group of subjects adapted to a rotation of the nominal map, imposed either stepwise or randomly over trials. Another group experienced a scaling distortion. We report two findings. First, adaptation rates and memory-dependent motor command updating depended on distortion type. Stepwise application and removal of the rotation induced a marked increase in finger motion variability but scaling did not, suggesting that the rotation initiated a more exhaustive search through the space of viable finger motions to resolve the target capture task than did scaling. Indeed, subjects formed new coordination patterns in compensating the rotation but relied on patterns established during baseline practice to compensate the scaling. These findings support the idea that the brain compensates direction and extent errors separately and in computationally distinct ways, but are inconsistent with the idea that once a task is learned, command updating is limited to those degrees of freedom contributing to performance (thereby minimizing energetic or similar costs of control). Second, we report that subjects who learned a scaling while moving to just one target generalized more narrowly across directions than those who learned a rotation. This contrasts with results from whole-arm reaching studies, where a learned scaling generalizes more broadly across direction than rotation. Based on inverse- and forward-dynamics analyses of reaching with the arm, we propose the difference in results derives from extensive exposure in reaching with familiar arm dynamics versus the novelty of the manual task.

The interacting role of media violence exposure and aggressive-disruptive behavior in adolescent brain activation during an emotional Stroop task.

Only recently have investigations of the relationship between media violence exposure (MVE) and aggressive behavior focused on brain functioning. In this study, we examined the relationship between brain activation and history of media violence exposure in adolescents, using functional magnetic resonance imaging (fMRI). Samples of adolescents with no psychiatric diagnosis or with disruptive behavior disorder (DBD) with aggression were compared to investigate whether the association of MVE history and brain activation is moderated by aggressive behavior/personality. Twenty-two adolescents with a history of aggressive behavior and diagnosis of either conduct disorder or oppositional-defiant disorder (DBD sample) and 22 controls completed an emotional Stroop task during fMRI. Primary imaging results indicated that controls with a history of low MVE demonstrated greater activity in the right inferior frontal gyrus and rostral anterior cingulate during the violent word condition. In contrast, in adolescents with DBD, those with high MVE exhibited decreased activation in the right amygdala, compared with those with low MVE. These findings are consistent with research demonstrating the importance of fronto-limbic structures for processing emotional stimuli, and with research suggesting that media violence may affect individuals in different ways depending on the presence of aggressive traits.

Cerebrospinal Fluid Leaks From the Lateral Ventricle: A Case Series.

OBJECTIVES: Describe the diagnosis and management of lateral skull base (LSB) cerebrospinal fluid (CSF) leaks originating from the lateral ventricle. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral academic center. PATIENTS: Patients with CSF leaks with direct communication to the lateral ventricle on preoperative imaging. INTERVENTION: Surgical repair via the middle cranial fossa (MCF) approach. MAIN OUTCOME MEASURES: CSF leak patient characteristics (age, sex, body mass index [BMI]) and postoperative course (complications and CSF leak resolution) were collected. RESULTS: Three patients had CSF leaks from the lateral ventricle and all patients demonstrated encephalomalacia of the temporal lobe on preoperative imaging. Encephalomalacia resulted from trauma in one case (age 5) and neurodegeneration in two cases (age 77 and 84). BMI ranged from 16.3 to 26.6 mg/kg2 and follow-up ranged from 4 to 21 months. Two patients presented with preoperative meningitis and all patients had resolution of CSF leaks after MCF repair. With the exception of the higher rate of meningitis, patient presentations did not differ from other spontaneous CSF leaks through middle fossa defects. There were no minor or major postoperative complications. CONCLUSIONS: CSF leaks from the lateral ventricle represent a rare subset of LSB CSF leaks and can occur in non-obese patients secondary to temporal lobe encephalomalacia. The MCF approach allows for repair of the dura and skull base in this cohort of patients with high-flow CSF leaks and loss of brain parenchyma.

Interrater Reliability of NI-RADS on Posttreatment PET/Contrast-enhanced CT Scans in Head and Neck Squamous Cell Carcinoma.

Purpose To evaluate the interrater reliability among radiologists examining posttreatment head and neck squamous cell carcinoma (HNSCC) fluorodeoxyglucose PET/contrast-enhanced CT (CECT) scans using Neck Imaging Reporting and Data System (NI-RADS). Materials and Methods In this retrospective study, images in 80 patients with HNSCC who underwent posttreatment surveillance PET/CECT and immediate prior comparison CECT or PET/CECT (from June 2014 to July 2016) were uploaded to the American College of Radiology's cloud-based website, Cortex. Eight radiologists from seven institutions with variable NI-RADS experience independently evaluated each case and assigned an appropriate prose description and NI-RADS category for the primary site and the neck site. Five of these individuals were experienced readers (> 5 years of experience), and three were novices (< 5 years of experience). In total, 640 lexicon-based and NI-RADS categories were assigned to lesions among the 80 included patients by the eight radiologists. Light generalization of Cohen κ for interrater reliability was performed. Results Of the 80 included patients (mean age, 63 years ± 10 [standard deviation]), there were 58 men (73%); 60 patients had stage IV HNSCC (75%), and the most common tumor location was oropharynx (n = 32; 40%). Light κ for lexicon was 0.30 (95% CI: 0.23, 0.36) at the primary site and 0.31 (95% CI: 0.24, 0.37) at the neck site. Light κ for NI-RADS category was 0.55 (95% CI: 0.46, 0.63) at the primary site and 0.60 (95% CI: 0.48, 0.69) at the neck site. Percent agreement between lexicon and correlative NI-RADS category was 84.4% (540 of 640) at the primary site and 92.6% (593 of 640) at the neck site. There was no significant difference in interobserver agreement among the experienced versus novice raters. Conclusion Moderate agreement was achieved among eight radiologists using NI-RADS at posttreatment HNSCC surveillance imaging. Keywords: CT, PET/CT, Head/Neck, Neck, Neoplasms-Primary, Observer Performance Supplemental material is available for this article. © RSNA, 2021.

Squamous Cell Carcinoma: PET/CT and PET/MRI of the Pretreatment and Post-Treatment Neck.

The incidence of head and neck cancer continues to rise annually, most commonly squamous cell carcinoma (SCCa). Advances in imaging techniques have improved diagnostic accuracy with important ramifications for initial staging and post-treatment surveillance. FDG-PET/CT and, more recently, FDG-PET/MRI have revolutionized the staging and surveillance of head and neck SCCa. We detail the diagnostic role of FDG-PET/CT and FDG-PET/MRI of SCCa at the different head and neck subsites, highlighting their role in identifying the primary tumor extent, regional nodal metastases, and distant metastatic disease in the pretreatment and post-treatment setting, as well as implications for staging, treatment, and prognosis.

Non-oncologic imaging of the oral cavity and jaws.

The unique and specialized structures of the oral cavity and jaws give rise to a myriad of diverse developmental, inflammatory, and benign lesions or conditions. This article reviews the imaging of common lesions and their variants, and reviews several rare but important lesions. Guidelines and algorithms for approaching the differential diagnosis are provided.

MRI compatibility issues in otology.

PURPOSE OF REVIEW: The increasing magnet strengths used for MRI scanning combined with a greater number and variety of otologic prostheses can lead to possible safety issues. This review examines the specific issues and the conclusions of 33 referenced studies examining those issues. RECENT FINDINGS: Variability of interactions between otologic implants and MRI scanners requires specific considerations for individual prostheses and magnet strengths. Recommendations are proposed in the referenced studies. SUMMARY: When a patient with an otologic prosthesis requires an MRI scan, options exist to help assure patient safety.

Nasopharyngeal carcinoma: recognizing the radiographic features in children.

BACKGROUND AND PURPOSE: Children often present with enlargement of the nasopharyngeal soft tissues, which is usually due to benign hypertrophy of adenoids. The objective of this report is to emphasize that, although rare, nasopharyngeal carcinoma (NPC) does occur in children and can be diagnosed reliably when certain key radiographic features are recognized. METHODS: The presenting scans of 11 patients with biopsy proven NPC were reviewed retrospectively by a CAQ-certified neuroradiologist. The age range was 12-17 years (median 15 years). Fifteen scans were reviewed, including 8 CT scans of the neck with intravenous contrast and 7 MR scans of the nasopharynx without and with gadolinium. RESULTS: All 11 patients had a nasopharyngeal mass. The nasopharyngeal mass had invaded the central skull base in 10 patients (91%). Widening of the petroclival fissure was present in 8 (73%) patients; all except one patient had accompanying skull base invasion. The tumor had extended into the adjacent parapharyngeal space in 6 (55%), the pterygopalatine fossa in 2 (18%), and the masticator space in 2 (18%). Unilateral cervical lymphadenopathy was present in 4 (36%) and bilateral in 7 (64%). Lateral retropharyngeal lymphadenopathy that measured greater than 1 cm in maximal transverse dimension was present in 10 (91%). CONCLUSION: Pediatric NPC is generally not suspected clinically until late into the disease process. Awareness that NPC can occur in children should prompt careful evaluation for distinctive radiographic features. Earlier diagnosis may then direct the patient to timely appropriate therapy when these key radiographic features are present and recognized.

Cortical adaptation following partial glossectomy with primary closure: implications for reconstruction of the oral tongue.

OBJECTIVES: The considerable variability in functional outcomes for speech and swallowing with different reconstruction techniques following partial glossectomy may reflect the ability of patients to adapt to altered tongue structure. The purpose of this study was to determine mechanisms of cortical adaptation in swallowing to partial glossectomy reconstructed with primary closure. METHODS: Four patients treated with partial glossectomy and primary closure underwent functional magnetic resonance imaging at a mean of 6 months after operation, and the data were compared to those from 8 healthy controls. RESULTS: Statistically significant increases in activity occurred predominately in the parietal cortices and the cerebellum. The volume of the resection was most highly correlated with activity in the premotor and parietal cortices and cerebellum. CONCLUSIONS: The adaptive changes in the cortex following partial glossectomy with primary closure reflect adaptation to the biomechanics of tongue movement during swallowing, and not altered sensation in the tongue.

Lesions of the Jaw.

Imaging of lesions within the maxilla and mandible is often fraught with difficulty owing to the similarity in the imaging appearance of a diverse array of pathological processes. Principally, lesions arise from either odontogenic sources or from primary bone lesions. The response of the cancellous and cortical bone to pathologic insult can be expressed either through an osteolytic or an osteoblastic response; thus the majority of lesions within the jaws can be classified as cystic or lytic appearing, sclerotic, or a mixture of the two. This article will review the imaging features of the most common cysts, fibro-osseous lesions, benign and malignant neoplasms, and highlight those features key to the differential diagnosis.