Memory loss versus memory distortion: The role of encoding and retrieval deficits in Korsakoff patients’ false memories

False Memories in Individuals With Stabilized Schizophrenia

This study aimed to examine the false memories in individuals with stabilized schizophrenia. Using the Deese, Roediger, and McDermott (DRM) task, schizophrenia patients and matched healthy controls had to recall words from each DRM list. Following the presentation of the DRM lists, the participants performed a recognition task. Neuropsychological tests were also administered. Results demonstrated that patients with schizophrenia recalled and recognized significantly fewer studied words than the healthy participants. This failure in retrieval is likely to result from a lack of encoding strategies. Results also showed that a stabilized schizophrenic pathology neither increased nor reduced false memories. Patients and controls showed high levels of false memories. Signal detection analyses revealed that patients discarded the critical word as not having been studied, relying on a lax decision criterion (based on familiarity, best guess or chance). Although false memories fell within the normal range for both groups, in individuals with schizophrenia they probably result from deficient encoding processes. Nevertheless, correlational analyses did not show which cognitive deficits contribute to false memories in schizophrenia.

Retained ability to extract gist in childhood-acquired amnesia: Insights from a single case

This paper presents the performance of a young amnesic person (CJ) in the DRM task. CJ was found to be sensitive to the DRM manipulation at a level comparable to controls in recognition and at a level higher than controls in free recall. Detailed analyses of recall intrusions lent further support to the finding that CJ is able to extract gist on the basis of semantic associations. Results are discussed with reference to relevant theory as well as the potential role of an impaired and immature cognitive system in adopting a semantic gist strategy in the absence of episodic memory.

False memories to emotional stimuli are not equally affected in right- and left-brain-damaged stroke patients

Previous research has attributed to the right hemisphere (RH) a key role in eliciting false memories to visual emotional stimuli. These results have been explained in terms of two right-hemisphere properties: (i) that emotional stimuli are preferentially processed in the RH and (ii) that visual stimuli are represented more coarsely in the RH. According to this account, false emotional memories are preferentially produced in the RH because emotional stimuli are both more strongly and more diffusely activated during encoding, leaving a memory trace that can be erroneously reactivated by similar but unstudied emotional items at test. If this right-hemisphere hypothesis is correct, then RH damage should result in a reduction in false memories to emotional stimuli relative to left-hemisphere lesions. To investigate this possibility, groups of right-brain-damaged (RBD, N=15), left-brain-damaged (LBD, N=15) and healthy (HC, N=30) participants took part in a recognition memory experiment with emotional (negative and positive) and non-emotional pictures. False memories were operationalized as incorrect responses to unstudied pictures that were similar to studied ones. Both RBD and LBD participants showed similar reductions in false memories for negative pictures relative to controls. For positive pictures, however, false memories were reduced only in RBD patients. The results provide only partial support for the right-hemisphere hypothesis and suggest that inter-hemispheric cooperation models may be necessary to fully account for false emotional memories.

Mood and the DRM paradigm: An investigation of the effects of valence and arousal on false memory

Recent studies regarding the effect of mood on the DRM (Deese–Roediger–McDermott) illusion have not been able to clearly establish yet whether valence or arousal is most critical in determining susceptibility to false memories, nor what the underlying processes are. In three experiments, both the valence and the level of arousal of participants' mood were manipulated. Six conditions were used: positive mood with high/low arousal, negative mood with high/low arousal, neutral mood, and a control condition. Memory was tested by means of immediate and delayed recognition and immediate free recall. The mood induction procedure was effective. For recognition memory, there was an effect of arousal on the endorsement of critical lures. Low-arousal moods elicited more false recognition than high-arousal moods, regardless of valence. Based on signal detection analyses, the effect was attributed to more liberal response criteria with low arousal, in combination with a tendency towards improved item-specific memory with high arousal.

The false memory syndrome: experimental studies and comparison to confabulations

False memories, or recollections that are factually incorrect but strongly believed, remain a source of confusion for both psychiatrists and neurologists. We propose model for false memories based on recent experimental investigations, particularly when analyzed in comparison to confabulations, which are the equivalent of false memories from neurological disease. Studies using the Deese/Roedinger-McDermott experimental paradigm indicate that false memories are associated with the need for complete and integrated memories, self-relevancy, imagination and wish fulfillment, familiarity, emotional facilitation, suggestibility, and sexual content. In comparison, confabulations are associated with the same factors except for emotional facilitation, suggestibility, and sexual content. Both false memories and confabulations have an abnormal sense of certainty for their recollections, and neuroanatomical findings implicate decreased activity in the ventromedial frontal lobe in this certainty. In summary, recent studies of false memories in comparison to confabulations support a model of false memories as internally-generated but suggestible and emotionally-facilitated fantasies or impulses, rather than repressed memories of real events. Furthermore, like confabulations, in order for false memories to occur there must be an attenuation of the normal, nonconscious, right frontal "doubt tag" regarding their certainty.

The effect of articulatory suppression on implicit and explicit false memory in the DRM paradigm

Several studies have shown that reliable implicit false memory can be obtained in the DRM paradigm. There has been considerable debate, however, about whether or not conscious activation of critical lures during study is a necessary condition for this. Recent findings have revealed that articulatory suppression prevents subsequent false priming in an anagram task (Lovden & Johansson, 2003). The present experiment sought to replicate and extend these findings to an implicit word stem completion task, and to additionally investigate the effect of articulatory suppression on explicit false memory. Results showed an inhibitory effect of articulatory suppression on veridical memory, as well as on implicit false memory, whereas the level of explicit false memory was heightened. This suggests that articulatory suppression did not merely eliminate conscious lure activation, but had a more general capacity-delimiting effect. The drop in veridical memory can be attributed to diminished encoding of item-specific information. Superficial encoding also limited the spreading of semantic activation during study, which inhibited later false priming. In addition, the lack of item-specific and phenomenological details caused impaired source monitoring at test, resulting in heightened explicit false memory.