Fractality of tics as a quantitative assessment tool for Tourette syndrome

Quantifying tics: Best practices and design considerations for video-based tic coding in research

Tic disorders (TD), including Tourette Syndrome, are characterized by involuntary, repetitive movements and/or vocalizations that can lead to persistent disability and impairment across the lifespan. Existing research demonstrates that video-based behavioral coding (VBBC) methods can be used to reliably quantify tics, enabling a more objective approach to tic measurement above and beyond standardly used TD questionnaires. VBBC is becoming more popular given the ease and ubiquity of obtaining patient videos. However, rigor and reproducibility of this work has been limited by undescribed and unstandardized approaches to using VBBC methods in TD research. The current paper describes "best practices" for VBBC in TD research, which have been tested and refined in our research over the past 15+ years, including considerations for data acquisition, coding implementation, interrater reliability demonstration, and methods reporting. We also address ethical considerations for researchers using this method.

Automated Quantification of Eye Tics Using Computer Vision and Deep Learning Techniques

BACKGROUND

Tourette syndrome (TS) tics are typically quantified using "paper and pencil" rating scales that are susceptible to factors that adversely impact validity. Video-based methods to more objectively quantify tics have been developed but are challenged by reliance on human raters and procedures that are resource intensive. Computer vision approaches that automate detection of atypical movements may be useful to apply to tic quantification.

OBJECTIVE

The current proof-of-concept study applied a computer vision approach to train a supervised deep learning algorithm to detect eye tics in video, the most common tic type in patients with TS.

METHODS

Videos (N = 54) of 11 adolescent patients with TS were rigorously coded by trained human raters to identify 1.5-second clips depicting "eye tic events" (N = 1775) and "non-tic events" (N = 3680). Clips were encoded into three-dimensional facial landmarks. Supervised deep learning was applied to processed data using random split and disjoint split regimens to simulate model validity under different conditions.

RESULTS

Area under receiver operating characteristic curve was 0.89 for the random split regimen, indicating high accuracy in the algorithm's ability to properly classify eye tic vs. non-eye tic movements. Area under receiver operating characteristic curve was 0.74 for the disjoint split regimen, suggesting that algorithm generalizability is more limited when trained on a small patient sample.

CONCLUSIONS

The algorithm was successful in detecting eye tics in unseen validation sets. Automated tic detection from video is a promising approach for tic quantification that may have future utility in TS screening, diagnostics, and treatment outcome measurement. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Fractals in Neuropsychology and Cognitive Neuroscience

The fractal dimension of cognition refers to the idea that the cognitive processes of the human brain exhibit fractal properties. This means that certain patterns of cognitive activity, such as visual perception, memory, language, or problem-solving, can be described using the mathematical concept of fractal dimension.The idea that cognition is fractal has been proposed by some researchers as a way to understand the complex, self-similar nature of the human brain. However, it's a relatively new idea and is still under investigation, so it's not yet clear to what extent cognitive processes exhibit fractal properties or what implications this might have for our understanding of the brain and clinical practice. Indeed, the mission of the "fractal neuroscience" field is to define the characteristics of fractality in human cognition in order to differently characterize the emergence of brain disorders.

Biomarkers of tic severity in children with Tourette syndrome: Motor cortex inhibition measured with transcranial magnetic stimulation

AIM

To compare transcranial magnetic stimulation (TMS)-derived measures of primary motor cortex (M1) physiology between children with and without Tourette syndrome, and to dimensionally analyze TMS measures with Tourette syndrome-related symptom severity.

METHOD

We used a cross-sectional experimental design. Sixty 8- to 12-year-old children participated (30 with Tourette syndrome: three females, mean age 10 years 10 months, standard deviation [SD] 1 year 3 months; 30 typically developing children: seven females, mean age 10 years 7 months, SD 1 year 3 months). In the group with Tourette syndrome, 15 (one female, mean age 10 years 11 months, SD 1 year 3 months) had comorbid attention-deficit/hyperactivity disorder (ADHD), rated with the Conners, Third Edition and the parent-reported ADHD rating scales. Tic severity was rated with the Yale Global Tic Severity Scale and urge severity with the Individualized Premonitory Urge for Tics Scale. M1 short-interval cortical inhibition (SICI) and intracortical facilitation were compared between diagnostic groups and, within the group with Tourette syndrome, correlated with symptom severity using linear mixed-effects models for repeated measures.

RESULTS

Accounting for ADHD, we found no difference in SICI or intracortical facilitation in those with Tourette syndrome versus typically developing children (p > 0.1). In the group with Tourette syndrome, reduced M1 SICI predicted greater total (p = 0.012) and global (p = 0.002) tic severity. There were no associations with urge severity (p > 0.5).

INTERPRETATION

Reduced M1 SICI is robustly associated with increased tic, but not urge, severity.

WHAT THIS PAPER ADDS

Increased tic severity is associated with reduced motor cortex short-interval cortical inhibition (SICI). Children with Tourette syndrome with increased urge severity also show increased tic severity. However, reduced motor cortex SICI is associated with tic, but not urge, severity.

Diagnosis and Management of Functional Tic-Like Phenomena

Over the past 3 years, a global phenomenon has emerged characterized by the sudden onset and frequently rapid escalation of tics and tic-like movements and phonations. These symptoms have occurred not only in youth known to have tics or Tourette syndrome (TS), but also, and more notably, in youth with no prior history of tics. The Tourette Association of America (TAA) convened an international, multidisciplinary working group to better understand this apparent presentation of functional neurological disorder (FND) and its relationship to TS. Here, we review and summarize the literature relevant to distinguish the two, with recommendations to clinicians for diagnosis and management. Finally, we highlight areas for future emphasis and research.