title: Multiple thalamo-cortical disconnections in anterior thalamic infarction: implications for thalamic mechanisms of memory and language.
abstract: Amnesia and linguistic deficits that are associated with thalamic damage have attracted the attention of researchers interested in identifying the neural networks involved in memory and language. The Papez circuit, which is composed of the hippocampus, mammillary body and anterior thalamic nuclei, was first proposed to be critical for memory. However, subsequently, the roles of the neural circuit consisting of the rhinal/parahippocampal cortices and the mediodorsal thalamic nuclei became evident. The ventral lateral nuclei or its adjacent structures have been found to be involved in semantic processing, but the specific neural circuits dedicated to language functions have not been identified. Anterior thalamic infarcts, which affect very circumscribed regions of the ventral anterior portion of the thalamus, often cause paradoxically prominent memory and language deficits. We conducted tractography analyses in 6 patients with left anterior thalamic infarcts to identify neural connections or circuits in which disruptions are associated with memory and language deficits in this condition. The current study demonstrated that the mammillothalamic tract, which connects the mammillary body with the anterior thalamic nuclei, and the anterior and inferior thalamic peduncles, which contain neural fibers that extend from several thalamic nuclei to the anterior temporal, medial temporal and frontal cortices, are disrupted in anterior thalamic infarction. These extensive thalamo-cortical disconnections appear to be due to the dissection of the neural fibers that penetrate the ventral anterior nucleus of the thalamus. Our results suggest the following: (1) amnesia that is associated with anterior thalamic infarction is best interpreted in the context of dual/multiple-system theories of memory/amnesia that posit that multiple neural circuits connecting the anterior and mediodorsal thalamic nuclei with the hippocampus and rhinal/parahippocampal cortices work in concert to support memory function; and (2) the semantic deficits observed in this syndrome may be associated with thalamo-anterior temporal and thalamo-lateral frontal disconnections.
authors: Department of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai Japan. Electronic address: nishiou@med.tohoku.ac.jp.
authors: Yoshiyuki
authors: Y
authors: Nishio
authors: Department of Psychiatry and Neuropathology, Faculty of Medical and Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan.
authors: Mamoru
authors: M
authors: Hashimoto
authors: Department of Radiology, Kinki University School of Medicine, Sayama, Japan.
authors: Kazunari
authors: K
authors: Ishii
authors: Department of Diagnostic Radiology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors: Daisuke
authors: D
authors: Ito
authors: Department of Diagnostic Radiology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors: Shunji
authors: S
authors: Mugikura
authors: Department of Diagnostic Radiology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors: Shoki
authors: S
authors: Takahashi
authors: Department of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai Japan.
authors: Etsuro
authors: E
authors: Mori
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000473:pathology; D020520:Brain Infarction / Q000473:pathology*; D002540:Cerebral Cortex / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D007806:Language Disorders / Q000473:pathology*; D008297:Male; D008326:Mammillary Bodies / Q000473:pathology; D008569:Memory Disorders / Q000473:pathology*; D009434:Neural Pathways / Q000473:pathology; D009483:Neuropsychological Tests; D013786:Thalamic Diseases / Q000473:pathology*; D013788:Thalamus / Q000098:blood supply / Q000473:pathology*
keywords: AN; IML; Language; MD; MTT; Medial temporal lobe; Memory; Semantic; Thalamus; VA; VAmc; VLa; VLp; Vim; anterior thalamic nuclei; internal medullary lamina; magnocellular ventral anterior nucleus; mammillothalamic tract; mediodorsal nuclei; ventral anterior nucleus; ventral intermediate nucleus; ventral lateral anterior nucleus; ventral lateral posterior nucleus