Using systematic investigations, including neurological and neuropsychological examinations and computed tomography and magnetic resonance imaging analyzed on anatomical maps, we prospectively studied 12 patients (age range, 63+/-19 years) with an isolated anterior thalamic infarct. They had acute, severe, perseverative behavior, which was apparent in thinking, speech, and all memory and executive tasks, combined with increased sensitivity to interference. They also showed superimposition of mental activities normally processed sequentially (e.g., giving biographical information while working on a calculation test), which we called palipsychism (from the Greek palin [again] and the Greek psyche [soul]). In addition, all 12 patients (8 with a left-sided infarct, 4 with a right-sided infarct) had word-finding difficulties, 7 of 12 with impaired naming, 8 of 12 with dysarthria, and 5 of 12 with hypophonia. Comprehension, repetition, written abilities, and reasoning were consistently preserved, but apathy was usual. All patients had anterograde memory impairment, with a delayed recall deficit, primarily verbal in left-sided infarcts and visuospatial in right-sided infarcts. Dysexecutive features such as difficulty in programming motor sequences were always present. Visual neglect or topographic disorientation was found in 3 patients. Magnetic resonance imaging emphasized involvement of the anterior group of thalamic nuclei, the mamillothalamic tract, and the anterior part of the internal medullary lamina, with structural sparing of the dorsomedial and ventrolateral nuclei. Sequential follow-up examinations showed spectacular improvement within a few months, with the only significant persisting abnormalities being memory dysfunction and apathy. The acute behavioral syndrome of anterior thalamic infarction is dominated by palipsychism, which corresponds to an overlap of sequential cognitive processes in two or more domains. Its association with severe perseverative behavior with increased sensitivity to interference, anterograde memory retrieval deficit, intrusions, naming difficulties with dysarthria and hypophonia, and apathy is suggestive of this type of infarct.