نقص ویژگی در یادآوری حافظه هیجانی در اسکیزوفرنی

The influence of emotion on episodic and autobiographical memory in schizophrenia was investigated. Using an experiential approach, the states of awareness accompanying recollection of pictures from the IAPS and of associated autobiographical memories was recorded. Results show that schizophrenia impairs episodic and autobiographical memories in their critical feature: autonoetic awareness, i.e., the type of awareness experienced when mentally reliving events from one’s past. Schizophrenia was also associated with a reduction of specific autobiographical memories. The impact of stimulus valence on memory performance was moderated by clinical status. Patients with schizophrenia recognized more positive than negative pictures, and recalled more positive than negative autobiographical memories while controls displayed the opposite pattern. A hypothesis in terms of a fundamental executive deficit underlying these impairments is proposed.

Among the large but selective memory deficits encountered in schizophrenia, the impairment of episodic memory is now well established (e.g., Bilder et al., 2000, Danion et al., 1999, Gold et al., 1992, Heinrichs and Zakzanis, 1998, Huron et al., 1995, Palmer et al., 1997 and Saykin et al., 1994). Patients with schizophrenia typically fail in tasks that require explicit and conscious retrieval of information from memory. According to Tulving (1985), the main characteristic of episodic memory is its dependence on autonoetic awareness, i.e., the kind of awareness where people consciously recollect events by reliving them mentally. Noetic awareness, on the other hand, is the knowledge that an event has occurred but in the absence of any conscious recollection. It conveys a more abstract sense of the past, based on feelings of familiarity. The distinction between the different states of awareness can be assessed using an experiential approach in which autonoetic and noetic awareness are operationally defined in terms of the Remember/Know procedure (Gardiner et al., 1996 and Tulving, 1985). In a recognition task, participants are asked to report their subjective state of awareness at the time they recognize each item. They are instructed to give a Remember response if they consciously recollect something they experienced when they learned the item, i.e., if they mentally relive the learning episode. For example, they can remember a thought they had, or an event that occurred, when they learned the item. Participants are instructed to give a Know response if recognition is accompanied by feelings of familiarity in the absence of any specific memories of the learning episode. Using this procedure, a series of studies have demonstrated that, compared to control participants, the recognition performance of patients with schizophrenia is associated with lower levels of Remember, but not of Know responses (e.g., Danion et al., 1999, Huron et al., 1995, Huron and Danion, 2002 and Sonntag et al., 2003). This indicates that schizophrenia selectively impairs autonoetic awareness, but not noetic awareness. More recently, several studies have reported that autobiographical memory (i.e., memory for personal events and facts) is also disturbed in schizophrenia (e.g., Baddeley et al., 1995, Feinstein et al., 1998, Riutort et al., 2003 and Tamlyn et al., 1992). Patients with schizophrenia generate fewer autobiographical memories than normal individuals. This deficit seems to be particularly marked for events that occurred after the onset of the disease (Elvevag et al., 2003a, Feinstein et al., 1998 and Riutort et al., 2003). Further, patients with schizophrenia report overgeneral memories rather than unique episodes that happened at a specific time and place (Harrison and Fowler, 2004, Iqbal et al., 2004 and Riutort et al., 2003). Indeed, when asked to retrieve specific memories (e.g., ‘When my husband and I went to a Chinese restaurant last week’), patients with schizophrenia tend to recall overgeneral events such as events that refer to repeated occasions (e.g., ‘Every time I go shopping’), or events that lasted longer than a day (e.g. ‘A weekend with my husband in Paris’). Schizophrenic patients’ lack of specificity in the retrieval of their own personal past may be related to their difficulties in consciously recollecting past events. According to Conway and Pleydell-Pearce (2000), autobiographical memories are generated from the individuals’ autobiographical knowledge base at different levels of specificity. The ability to specify personal events is linked to autonoetic awareness. Indeed, the recollection of highly specific details, such as the sensory-perceptual details of a particular situation, is necessary for mentally reliving these events. The experience of conscious recollection emerges when specific details are accessed in the autobiographical knowledge base (Conway & Pleydell-Pearce, 2000). In contrast, the subjective feeling of simply knowing that an event has occurred should be sufficient for the recall of more general, abstract memories (Conway & Pleydell-Pearce, 2000). Taking these arguments into account, the difficulties for schizophrenic patients to recollect specific events could be intrinsically related to their autonoetic awareness deficit. This hypothesis has been recently tested in a study (Danion et al., 2005) comparing the performance of 22 patients with schizophrenia and 22 normal controls on an adaptation of the autobiographical memory inquiry (Piolino, Desgranges, Benali, & Eustache, 2002). Participants were asked to recall specific autobiographical memories and to indicate the subjective states of awareness associated with the recall of what happened, when and where. Danion and collaborators (2005) found that patients with schizophrenia retrieved fewer specific memories and provided lower levels of Remember responses than controls, and this was the case across all lifetime periods. More directly relevant to the present study, the proportion of Remember responses was significantly correlated with the level of specificity for both the patients and the control group. When considering the relationship between consciousness and memory in schizophrenia, emotion may play a significant role. Because emotional disturbances are a major aspect of schizophrenia, it is crucial to establish whether patients with schizophrenia exhibit a different pattern of memory performance than control participants when emotional material is used. Many studies conducted on normal participants have shown that memory is strongly influenced by emotion (e.g., Blaney, 1986, Bower, 1981 and Conway and Pleydell-Pearce, 2000). Memory for emotional events is better than memory for neutral events, a phenomenon known as the emotionality effect (e. g., Dutta and Kanungo, 1975, Rubin and Friendly, 1986 and Rusting, 1998). There have been relatively few studies that have addressed the impact of emotion on memory in schizophrenia, and their findings are not consistent. Most of these studies have used emotional words to compare the impact of the emotional valence of to-be-learned words on recall performance in patients with schizophrenia and normal controls. Kayton and Koh (1975) have found that, contrary to normal controls, patients recalled unpleasant words and pleasant words equally well, indicating an emotionally undifferentiated recall. Another experiment has observed a more rapid forgetting of positive than negative words in patients as compared to controls (Calev & Edelist, 1993). Using free recall and recognition tasks, Mathews and Barch (2004) have observed that patients with schizophrenia demonstrate patterns of memory for emotional words similar to normal participants, with better performance for negative than positive words. Other studies have showed an intact emotionality effect and a preservation of the Pollyanna tendency for patients (Danion et al., 2003 and Neumann et al., 2006), which is a better recall of positive than negative events often observed in normal individuals (Boucher and Osgood, 1969 and Bradley and Mathews, 1983). However, other research did not find this Pollyanna tendency in the patient group (Koh, Grinker, Marusarz, & Forman, 1981). Obviously, no conclusions can be drawn from this discrepant pattern of results. One reason for these inconsistencies might be that nearly all of the studies described above have investigated patients’ abilities to recollect emotional events without considering the subjective experience associated with these memories. Because consciousness plays an important role in memory deficits for patients with schizophrenia (Danion et al., 1999), it is crucial to investigate the different states of awareness accompanying the recollection of emotional memories in schizophrenia. Moreover, the series of studies conducted by Ochsner (2000) on normal individuals suggests that the use of the Remember/Know procedure could cast a new light on the relationship between emotion and memory. Indeed, in three consecutive studies, Ochsner has demonstrated that Remember, but not Know responses were more frequent for emotional than for neutral events, underlining the importance of consciously re-experiencing an emotional event during its recall. Relevant to this perspective, two recent experiments yielded preliminary evidence that the influence of emotion on autonoetic awareness is preserved in schizophrenia (Danion et al., 2003 and Neumann et al., 2006). Using a Remember/Know procedure (Gardiner et al., 1996 and Tulving, 1985), those studies have investigated the influence of the emotional valence of words (Danion et al., 2003) and sentences (Neumann et al., 2006) on the subjective states of awareness accompanying recognition performance in schizophrenia. Both of these studies have shown that despite poorer recollection and a global reduction of Remember responses in the patient group compared to normal controls, patients’ autonoetic awareness was moderated by the emotionality of the material in the same way as in controls. Indeed, in both groups, the proportion of Remember responses was higher for positive than for negative material. Danion and collaborators (2003) also observed that the proportion of Remember responses was higher for emotional words than for neutral words. However, the type of material used in these previous studies (i.e., emotional words or sentences) probably induced weak emotional responses, if any. It is thus possible that the influence of emotional words on autonoetic awareness was preserved because the evaluation of the emotional valence of the words was closely related to their semantic processing and did not really require the actual activation of their emotionally arousing features. This raises the question of the impact on episodic memory in schizophrenia for stimuli that elicit stronger emotional responses than words. To investigate this issue in the present study, we used photographs selected from the International Affective Picture System (IAPS, Lang, Greenwald, Bradley, & Hamm, 1993) as stimuli. Indeed these photos have been shown to elicit not only subjective and expressive changes, but also physiological changes involved in emotion, such as increases in heart rate, skin conductance, and muscle activity (Lang et al., 1993). In sum, there is now converging evidence that patients with schizophrenia suffer from impaired episodic and autobiographical memories. However, little is known about their abilities to consciously recollect emotional personal episodes from their lives. Indeed, schizophrenia research concerning the impact of emotion on memory and states of awareness has focused on impersonal episodic memory tasks based on the ability to recall or recognize stimuli previously encoded in an experimental room. Further, the only study (Danion et al., 2005) that has addressed the possible link between conscious recollection and autobiographical memory in schizophrenia did not control for the valence of the memories reported. Thus, despite evidence in healthy individuals that the emotion felt during a situation strongly influences the richness of its retrieval and the associated subjective experience (Conway, Collins, Gathercole, & Anderson, 1996), this phenomenon is still unexplored in schizophrenia. This question, however, seems crucial as emotional autobiographical memories are central for the construction of a sense of self, the deficit of which constitutes the core symptom of schizophrenia. The present study investigated the subjective states of awareness that accompany recognition of emotional episodic and autobiographical memories using the Remember/Know procedure (Gardiner et al., 1996 and Tulving, 1985). In a learning session, pictures from the IAPS (Lang et al., 1993) were presented to patients with schizophrenia and normal controls. Participants were asked to assess the emotional valence of the picture. Twenty-four hours later, in a recognition session, participants had to recognize the target pictures among distractors and to indicate the subjective state of awareness associated with their recognition. On the basis of previous evidence, we predicted that patients with schizophrenia should exhibit poorer recognition performance and should provide fewer Remember responses in picture and valence recognition than control participants. The second aim was to compare the recollection of autobiographical memories, and the associated subjective states of awareness, in patients with schizophrenia and in normal individuals. To achieve this goal, in the first session participants were asked to recall specific personal memories induced by each picture item. During the recognition session, participants were asked to retrieve the autobiographical memories provided during the first session when the picture was shown. In fact, the retrieval of the autobiographical memory generated during the first session was considered as recognition of the picture associated with autonoetic awareness. Indeed, it constitutes direct evidence that participants remembered something that happened during the first session when they saw the pictures. The demonstration of a reduced proportion of specific memories, associated with a low level of Remember responses, would be consistent with the notion of a positive relationship between autonoetic awareness and autobiographical memory specificity in patients with schizophrenia (Danion et al., 2005). In other words, we predicted that, considering their lack of conscious recollection, patients with schizophrenia should recall fewer specific personal memories than controls. With regard to the influence of valence on memory, we predicted that for normal participants, as in the studies of Ochsner (2000), Remember responses would be more frequent for negative than for positive stimuli. In view of the inconsistent findings concerning the impact of emotion on memory in schizophrenia, no prediction was made for the patients group on that specific topic.