Forebrain Control of Behaviorally Driven Social Orienting in Zebrafish.

Deficits in social engagement are diagnostic of multiple neurodevelopmental disorders, including autism and schizophrenia [1]. Genetically tractable animal models like zebrafish (Danio rerio) could provide valuable insight into developmental factors underlying these social impairments, but this approach is predicated on the ability to accurately and reliably quantify subtle behavioral changes. Similarly, characterizing local molecular and morphological phenotypes requires knowledge of the neuroanatomical correlates of social behavior. We leveraged behavioral and genetic tools in zebrafish to both refine our understanding of social behavior and identify brain regions important for driving it. We characterized visual social interactions between pairs of adult zebrafish and discovered that they perform a stereotyped orienting behavior that reflects social attention [2]. Furthermore, in pairs of fish, the orienting behavior of one individual is the primary factor driving the same behavior in the other individual. We used manual and genetic lesions to investigate the forebrain contribution to this behavior and identified a population of neurons in the ventral telencephalon whose ablation suppresses social interactions, while sparing other locomotor and visual behaviors. These neurons are cholinergic and express the gene encoding the transcription factor Lhx8a, which is required for development of cholinergic neurons in the mouse forebrain [3]. The neuronal population identified in zebrafish lies in a region homologous to mammalian forebrain regions implicated in social behavior such as the lateral septum [4]. Our data suggest that an evolutionarily conserved population of neurons controls social orienting in zebrafish.

Four-corner arthrodesis using a circular plate and distal radius bone grafting: a consecutive case series.

PURPOSE: Four-corner arthrodesis with scaphoid excision has been shown to be an acceptable method for treating wrist degenerative changes. Some recent studies have identified higher complication rates when circular plates are used. This study examined a consecutive case series with defined technique for outcome and complications. METHODS: A retrospective assessment was performed in a consecutive cohort of 28 patients who underwent a standardized 4-corner arthrodesis with a 2nd-generation circular plate and distal radius bone grafting for a diagnosis of scapholunate advanced collapse, scaphoid nonunion advanced collapse, or midcarpal arthrosis. Complete data were obtained for 26 of the patients and partial data for the other 2. Follow-up examination included visual analog scale and activity scores, work status, posteroanterior and lateral radiographs, bone union status, grip strength, range of motion, and complications. RESULTS: Average follow-up was 46 months. Range of motion averaged 45% of the uninjured side (average extension, 35 degrees; average flexion, 26 degrees). Grip strength averaged 82% of the uninjured side. The mean visual analog scale pain and activity scores were 2.3/10 and 2.4/10. Only 1 patient required job modification because of wrist impairment. Radiographs demonstrated union of the primary capitolunate fusion mass in all of the cases. There was 1 case of probable but not certain peritriquetral nonunion and 1 case of asymptomatic loss of radiolunate joint space; in terms of hardware, there was screw back-out (of 1 screw) in 1 case the plate broke in 1 case. Two patients underwent reoperation, one for radial styloid impingement pain and the other for lack of flexion. CONCLUSIONS: Despite recent reports indicating a high nonunion rate with plate fixation, standardized 4-corner arthrodesis using a recessed, dorsal circular plate and distal radius bone grafting produced excellent and reproducible results in this consecutive series. Notably, there was no development of secondary arthritic changes at the radiolunate joint, indicating a reasonable durability to the procedure. Optimal results require exacting technique with quality bone graft.

Glomus tumors.

Glomus tumors are rare vascular tumors that are found most commonly in the hand. Although the tumors are benign, they can cause intense focal pain. Patients often go undiagnosed or misdiagnosed for many years because the tumors are small, usually not palpable, and have varying presentations. A combination of magnetic resonance imaging and clinical examination is used to support the diagnosis. Surgical excision normally provides complete pain relief. An awareness of the diagnosis is critical to preventing an unnecessary delay in treatment.