Three rhesus monkeys (Macaca mulatta) performed a simultaneous chaining task in which stimuli had to be sorted according to their visual properties. Each stimulus could vary independently along two dimensions (luminosity and radius), and a cue indicating which dimension to sort by was random trial to trial. These rapid and unpredictable changes constitute a task-switching paradigm, in which subjects must encode task demands and shift to whichever task-set is presently activated. In contrast to the widely reported task-switching delay observed in human studies, our subjects show no appreciable reduction in reaction times following a switch in the task requirements. Also, in contrast to the results of studies on human subjects, monkeys experienced enduring interference from trial-irrelevant stimulus features, even after exhaustive training. These results are consistent with a small but growing body of evidence that task-switching in rhesus macaques differs in basic ways from the pattern of behavior reported in studies of human cognition. Given the importance of task-switching paradigms in cognitive and clinical assessment, and the frequency with which corresponding animal models rely on non-human primates, understanding these differences in behavior is essential to the comparative study of cognitive impairment.

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A 53-year-old woman presented with a 1-month history of decreased vision and progressive left periorbital fullness. Exam and radiography confirmed a left lacrimal gland mass causing mass effect on the globe and a compressive optic neuropathy. Orbitotomy with excisional biopsy confirmed carcinoma ex pleomorphic adenoma with epithelial and myoepithelial differentiation. Following a negative systemic workup, the patient underwent radiation therapy and remains free of clinical or radiographic disease 24 months following surgery. Herein the presentation, radiography, histopathology, and treatment outcome of a rare case of lacrimal gland epithelial-myoepithelial carcinoma ex pleomorphic adenoma is described.

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