Experimental psychological study for relasionship between lesion sites and defective states in amnesics.

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1) Ten patients with infarction in anterior thalamus (six patients with left lesion, one with right, three with both, all patients were right handed) were investigated. They show clouding of consciusness in acute phase, repression of spontaneity in chronic phase. All patients have memory disorder, especially anterograde amnesia is distinct. Patients with left lesion shows verbal amnesia, and patients with right lesion shows visual amnesia.2) Ten patients with lesion in left medial anterior and para midline thalamus were researched. None patients but one Korsakoff symdromes showed retrograde amnesia or confabulation, and two pure amnesic patients showed verbal anterograde amnesia. Six patients also showed visual anterograde amnesia, and regression of spontaneity, intelligence, and verbal ability indicated dysfunction of frontal lobe. Because there found not difference of memory disorder between patients with medial anterior lesion and ones with para midline lesion, it was considered tha … More t they had lesions both mamillothalamic tract and internal medullary lamina, As patients with memory disorder showed decrease of blood flow in frontal lobe, and patients without memory disorder did not show it, so it was suggested that decrease of blood flow in frontal lobe by lesion on neural pathway between thalamus and frontal lobe relates memory disorder.3) Patients with circumscribed bilateral fornix lesion showed anterograde amnesia about verbal and visual episodic memory, but not showed retrograde amnesia, and semantic memory and procedural memory were intact.4) Research for patients with lesion in posterior area of Splenium made out that left lesion caused memory disorder and right lesion caused defect of route finding, but this was considered as brought by slight difference of lesion site.5) Patients with viral encephalitis showed pure retrograde amnesia without anterograde amnesia, so it was suggested that there should be different brain mechanisms between memory formation and memory retrieval. Less