Recognition memory without awareness during transient global amnesia.

A 55-year-old banker was brought to the hospital by his wife because of temporal disorientation and repetitive questioning that had started 2 h before. His past medical history included an episode of TGA 11 years previously. Evaluation took place 3 h after the beginning of the episode. The Mini-Mental State Examination was 22/30, with mistakes on temporal orientation and word recall; the Frontal Assessment Battery was normal with 18/18 [6] . The remainder of the neurological examination was normal. The patient had difficulty recalling events of his personal life from the past 20 years and could not recall current news events. Visuospatial anterograde memory, tested by hiding 3 objects from the patient’s view in the examination room, was abolished. Auditory-verbal anterograde memory was tested using a 5-word list. Immediate recall was 5 both spontaneously and upon categorical cueing. After a distracting task of serial subtractions, delayed recall was nil. Neither categorical cueing nor providing the target word with two distractors induced recognition. However, upon forced choice, the patient correctly selected the target word 4 times out of 5, Dear Sir, Transient global amnesia (TGA) is a fascinating syndrome of unknown etiology where anterograde episodic memory transiently ceases to function, together with a variable degree of retrograde episodic amnesia [1, 2] . Whereas transient retrograde amnesia must be caused by a reversible deficit in memory recall, the pathophysiology of transient anterograde amnesia appears less homogeneous. Patients examined during TGA were shown to display difficulties either in immediate recall of previously presented items, suggesting impairment in the encoding of memories, or in delayed recall together with an inability to recognize target items when presented with distractors, suggesting a deficit of memory storage [3] . Howev er, some TGA patients show better performance in recognition memory than in spontaneous delayed recall, suggesting that some memories can be encoded and stored during TGA, but that their retrieval is impaired [4, 5] . Here, we report a patient examined during TGA who performed significantly above chance in a forced multiple-choice recognition task despite being unaware that he did, suggesting that TGA may include a deficit in the retrieval of stored memories to consciousness. Received: July 28, 2011 Accepted: August 8, 2011 Published online: October 26, 2011