J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.66.2.148 on 1 February 1999. Downloaded from 148 J Neurol Neurosurg Psychiatry 1999;66:148–154 Episodic memory in transient global amnesia: encoding, storage, or retrieval deficit? Francis Eustache, Béatrice Desgranges, Peggy Laville, Bérengère Guillery, Catherine Lalevée, Stéphane SchaeVer, Vincent de la Sayette, Serge Iglesias, Jean-Claude Baron, Fausto Viader Abstract evertheless this division into processing stages Objectives—To assess episodic memory continues to be useful in helping understand (especially anterograde amnesia) during the working of memory systems”. These three the acute phase of transient global amne- stages may be defined in the following way: (1) sia to diVerentiate an encoding, a storage, encoding, during which perceptive information or a retrieval deficit. is transformed into more or less stable mental Methods—In three patients, whose am- representations; (2) storage (or consolidation), nestic episode fulfilled all current criteria during which mnemonic information is associ- for transient global amnesia, a neuro- ated with other representations and maintained psychological protocol was administered in long term memory; (3) retrieval, during which included a word learning task which the subject can momentarily reactivate derived from the Grober and Buschke’s mnemonic representations. These definitions procedure. will be used in the present study. Results—In one patient, the results sug- Regarding the retrograde amnesia of TGA, it gested an encoding deficit, and in two oth- should depend on a problem of retrieval of ers, a storage deficit. information from episodic memory,3 as sug- Conclusions—The encoding/storage im- gested by (1) the sudden nature of the episode pairment concerning anterograde amne- (which excludes, for example, a progressive sia documented in our patients stands in anterograde amnesia); (2) the fact that amnesia clear contrast with the impairment in can aVect very distant events (even if retrieval which must underly the retro- patchy11 12); and (3) its transient nature—that grade amnesia that also characterises is, the prior memories becoming available transient global amnesia. This dissocia- again after the attack (with the exception of a tion in turn favours the idea of a func- “blank” covering the acute phase and possibly tional independence among the cognitive the few preceding hours). mechanisms that subserve episodic Contrary to retrograde amnesia, however, the memory. mechanisms responsible for the anterograde (J Neurol Neurosurg Psychiatry 1999;66:148–154) amnesia have not been elucidated. Although some have suggested that they may diVer from Keywords: encoding; storage; retrieval; anterograde http://jnnp.bmj.com/ amnesia; retrograde amnesia; episodic memory those involved in retrograde amnesia and have considered a consolidation disorder, experi- INSERM U320 and mental support was not provided.3101516Other Services de Transient global amnesia (TGA)12is a neuro- authors argued that the memory disturbance Neurologie, CHU Côte 4 de Nane, 14033 Caen logical syndrome the operational definition of was the result of a deficit either in encoding or Cedex, France which is purely clinical: a massive amnesia with in retrieval.17 A systematic study of these F Eustache an abrupt onset, without accompanying neuro- processes should aVord a better understanding B Desgranges logical deficit, which lasts a few hours. The of the clinical characteristics of this syndrome. P Laville Furthermore, to quote Ca ara ,16 TGA on September 30, 2021 by guest. Protected copyright. B Guillery patients, aged around 50 or over, remain alert V et al C Lalevée and communicative with no loss of personal represents an “interesting ‘experimentum natu- S SchaeVer identity. Neuropsychological examinations rae’ on the mechanisms of memory”, both at V de la Sayette made during the acute phase have shown that the cognitive and at the neurobiological level.18 S Iglesias TGA is a selective disorder of episodic memory Transient global amnesia oVers a unique F Viader with no impairment of general cognitive opportunity to study dysfunctioning human functions,3 or of other components of memory, memory in the absence of the reorganisation INSERM U320, Centre 34 Cycéron, Boulevard such as short term memory, semantic phenomena which take place in permanent Becquerel, BP 5229, memory,5 procedural memory,6–9 and amnesic syndromes. In addition, the patient can 14074 Caen, France priming.8–10 This selective impairment of epi- act as his own control, a feature of particular J-C Baron sodic memory manifests itself as both interest in an area such as memory, which is 11–13 5 Correspondence to: retrograde and anterograde amnesia. How- characterised, even in the normal subject, by a Professor Francis Eustache, ever, the exact nature of the impairment within large intersubject variability. INSERM U 320, Services de episodic memory processes—encoding, stor- The principal objective of this work was to Neurologie, CHU Côte de age, and retrieval—remains unknown. As study anterograde amnesia in several patients Nacre, 14033 Caen Cedex, 14 France. pointed out by Baddeley, “any system for with TGA during the attack, with the aid of a storing information...will need (1) to be able to prospectively designed protocol aimed at dif- Received 30 December 1997 encode...information; (2) to store it; and ferentiating between selective disorders of and in final form 14 July 1998 subsequently (3) to retrieve that information. encoding, storage, and retrieval of information Accepted 3 August 1998 While these three stages are closely linked...n- in episodic memory. More specifically, our J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.66.2.148 on 1 February 1999. Downloaded from Episodic memory in transient global amnesia 149 protocol should allow us to test the hypothesis nouns of 5 to 8 letters, with a lexical frequency that anterograde and retrograde amnesia result ranging from 100 to 10 000, selected from the from distinct cognitive mechanisms, an oppor- Brulex lexical data bank.25 Our paradigm is tunity otherwise diYcult to test in permanent derived from Grober and Buschke’s amnesia. procedure26 and uses the encoding depth prin- ciple of Tulving and Thompson,27 according to Methods which the greater the depth of the processing of SUBJECTS information the better it is recalled (generally Control subjects semantic processing would be involved). To The control group consisted of 40 subjects control the level of processing, the subject is aged between 45 and 75 (mean 57.7 (SD 9.1) first asked to process each word in depth by years). To allow subsequent matching to generating a sentence containing the word. prospectively recruited TGA patients, this Then, to ensure the actual carrying out of deep control group was further subdivided into four encoding, a task of immediate cued recall is subgroups of 10 subjects each according to age given by providing the appropriate semantic (two age ranges: 45–60 and 61–75 years) and category. This task is carried out every two educational level (for the young group: above words, the time elapsed between the presenta- or below 10 years of education; for the old tion of the target word and the cued recall task group: above or below 8 years of education; the thus remaining within the limits of working class boundary being diVerent to lessen cohort memory (appendix). Therefore, after process- eVects). ing for example, the first two words of the list (turnip, museum), the subject must recall each Patients one of them in response to the presentation of Over a period of 1 year, we had the opportunity their respective semantic cues (vegetable and of examining eight patients suspected of having public place respectively). This procedure is an episode of idiopathic TGA in the emergency repeated throughout the whole list providing department of the University Hospital of Caen. the score of immediate cued recall. If the sub- Six of them satisfied the operational criteria ject fails in the immediate recall task, he or she established by Caplan19 and modified by is reminded of the word, again requested to Hodges and Warlow,20 but three had already make a sentence containing the target, and to entered the recovery stage when the neuro- recall it in response to its categorical cue. This psychological tests were carried out. The procedure therefore ensures that even if the protocol could be completed in its entirety instruction to memorise is forgotten during the during the acute phase by three patients. Their test, the items have been processed and there- results are the basis of this study. There were fore should leave a memory trace, if encoding is two women (patient A and patient B), aged preserved. Immediately after the processing of respectively 71 and 68 years, both with a good the 16 words, retrieval is assessed according to educational level and a man of 54 years, patient both free recall and recognition. In the free C, with a low educational level. recall procedure, the subject has to engage in a strategic search process which is not necessary NEUROPSYCHOLOGICAL PROTOCOL in the recognition task because each target item The neuropsychological protocol was specially is provided for him or her together with three designed for this study. It is modular and can distractors from the same semantic category http://jnnp.bmj.com/ be applied in the form of short sequences the position of which was randomised. interleaved with medical examinations. ANALYSIS OF THE SCORE PROFILES General cognitive assessment The battery produces three scores—namely, The general cognitive assessment included the immediate cued recall, free recall, and recogni- following subtests: orientation in time and tion scores. The analysis of the score profiles space,21 problem solving, and copying of makes it possible to infer the nature of the dis- on September 30, 2021 by guest. Protected copyright. geometric figures (taken from the cognitive turbance responsible for the anterograde am- assessment battery22), short term memory, nesia.