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Transcranial direct-current stimulation (tDCS) of the cerebellum is a promising non-invasive neuromodulatory technique being proposed for the treatment of neurological and neuropsychiatric disorders. However, there is a lack of knowledge about how externally applied currents affect neuronal spiking activity in cerebellar circuits in vivo . We investigated how Cb-tDCS affects the firing rate of Purkinje cells (PC) and non-PC in the mouse cerebellar cortex to understand the underlying mechanisms behind the polarity-dependent modulation of neuronal activity induced by tDCS. Mice (n = 9) were prepared for the chronic recording of LFPs to assess the actual electric field gradient imposed by Cb-tDCS in our experimental design. Single-neuron extracellular recording of PCs in awake (n = 24) and anesthetized (n = 27) mice was combined with juxtacellular recordings and subsequent staining of PC with neurobiotin under anesthesia (n = 8) to correlate their neuronal orientation with their response to Cb-tDCS. Finally, a high-density Neuropixels recording system was used to demonstrate the relevance of neuronal orientation during the application of Cb-tDCS in awake mice (n = 6). In this study, we observe that Cb-tDCS induces a heterogeneous polarity-dependent modulation of the firing rate of Purkinje cells (PC) and non-PC in the mouse cerebellar cortex. We demonstrate that the apparently heterogeneous effects of tDCS on PC activity can be explained by taking into account the somatodendritic orientation relative to the electric field. Our findings highlight the need to consider neuronal orientation and morphology to improve tDCS computational models, enhance stimulation protocol reliability, and optimize effects in both basic and clinical applications., Competing Interests: Declaration of interests: The authors declare no competing financial interests.

Background: Glenohumeral arthropathy after surgery for traumatic shoulder instability is a condition whose etiology and long-term course are still unknown., Purpose: To evaluate the risk factors for the onset of arthropathy and to assess the relationship between the degree of arthropathy and final outcomes., Study Design: Case series; Level of evidence, 4., Methods: We included patients who underwent surgery for a shoulder instability at a single institution between 2000 and 2004. The following variables were studied for relationship with functional outcomes: sex, age, body mass index, smoking at the time of surgery, number of episodes of shoulder dislocation, and time from first dislocation to surgery. The number of anchors used and their position were also evaluated. Functional outcomes were assessed using the Constant-Murley, Western Ontario Shoulder Instability Index, and Rowe scores, and results were compared with the onset of arthropathy according to Buscayret classification. Spearman and Pearson correlations were performed for the association between glenohumeral arthritis (Buscayret grade) and the study variables, the Mann-Whitney U test and Student t test were used to compare outcome scores with the study variables, and the Kruskal-Wallis test was used to compare Buscayret grade and outcome scores., Results: A total of 26 shoulders in 25 patients were analyzed, finding a high rate (54%) of arthropathy at a minimum follow-up of 16 years. Patients with Buscayret grade 4 had the worst functional results ( P = .007). However, 80% of patients with Buscayret grade ≤3 had excellent Constant-Murley scores. A significant relationship was found between degree of arthropathy and patients who were smokers before surgery ( P < .01). No relationship was found between the onset of arthropathy and the other variables analyzed., Conclusion: Postinstability glenohumeral arthropathy was not correlated with functional outcomes except in those patients with advanced arthroplasty (Buscayret grade 4). A direct relationship was found between smoking before surgery and the onset of glenohumeral arthropathy., Competing Interests: The authors have declared that there are no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto., (© The Author(s) 2022.)

Atypical sensory processing is currently included within the diagnostic criteria of autism. The cerebellum is known to integrate sensory inputs of different modalities through its connectivity to the cerebral cortex. Interestingly, cerebellar malformations are among the most replicated features found in postmortem brain of individuals with autism. We studied sensory processing in the cerebellum in a mouse model of autism, knock-out (KO) for the Cntnap2 gene. Cntnap2 is widely expressed in Purkinje cells (PCs) and has been recently reported to regulate their morphology. Further, individuals with CNTNAP2 mutations display cerebellar malformations and CNTNAP2 antibodies are associated with a mild form of cerebellar ataxia. Previous studies in the Cntnap2 mouse model show an altered cerebellar sensory learning. However, a physiological analysis of cerebellar function has not been performed yet. We studied sensory evoked potentials in cerebellar Crus I/II region on electrical stimulation of the whisker pad in alert mice and found striking differences between wild-type and Cntnap2 KO mice. In addition, single-cell recordings identified alterations in both sensory-evoked and spontaneous firing patterns of PCs. These changes were accompanied by altered intrinsic properties and morphologic features of these neurons. Together, these results indicate that the Cntnap2 mouse model could provide novel insight into the pathophysiological mechanisms of autism core sensory deficits., (Copyright © 2021 Fernández et al.)