Intact attentional control of working memory encoding in schizophrenia.

This study reports evidence that individuals with schizophrenia (SC) demonstrate intact attentional selection for visual working memory (WM) storage. A group of 62 participants with SC and 55 control participants without SC were studied in a series of 5 experiments that examined the ability to use top-down and bottom-up cues to guide WM encoding, as well as the ability to spontaneously select a subset of representations for storage. Participants with SC exhibited a consistent and robust ability to use selective attention in the control of WM in all 5 experiments, demonstrating a remarkable island of preserved functioning given the broad spectrum of impairments of attention and WM that have been widely reported in those with SC. These findings indicate that attention is not globally impaired in SC and make it possible to delineate more precisely the nature of the specific impairment of attention in this disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The impact of monetary reward on memory in schizophrenia spectrum disorder.

The impact of monetary reward on verbal working memory (vWM) and verbal long-term memory (vLTM) was evaluated in 50 patients with schizophrenia spectrum disorders and 52 matched healthy participants. This research was motivated by the observations that negative symptoms in schizophrenia are associated with reduced drive and that patients with these symptoms exhibit greater mnemonic impairments. Reward-related gains were evaluated across two levels of vWM load on the n-back task and across three aspects of vLTM derived from the California Verbal Learning Test-II (i.e., learning, total immediate recall, and retention). Although healthy individuals benefited from reward at a high vWM load level, schizophrenia patients exhibited no reward-related improvements in vWM. In contrast, improvement in vLTM retention was induced by reward for both patients and controls. Finally, symptomatic and pharmacology treatment factors were associated with reward-related gains in persons with schizophrenia. In conclusion, contingent monetary rewards delivered during vWM and vLTM enhanced specific aspects of memory. The influence was relatively small and dependent on the specific neurocognitive operation examined, the mental health status of the participants, and for patients, their particular symptoms and pharmacological treatments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired visual working memory consolidation in schizophrenia.

This study investigated working memory (WM) consolidation, that is, the time required to create durable WM representations, at different levels of WM load in schizophrenia. Twenty-three schizophrenia spectrum patients and 16 control subjects participated in a change-detection task in which a sample array of 1-3 squares appeared followed by a delay and a test array. An array of pattern masks was inserted into the delay interval--covering the locations of the sample-array squares--100-800 ms after the offset of the sample array. If a durable WM representation is formed prior to mask onset, the mask should not impair performance. The degree of masking at an interval reflects the degree of WM consolidation at that time. Neither group showed masking at set size 1. Unlike controls, patients demonstrated robust masking effects at set size 2. Both groups showed masking at set size 3, but masking effects were larger and longer lasting in patients. These data demonstrate abnormally prolonged WM consolidation in schizophrenia. This impairment may slow the formation of stable representations of the visual environment, impacting everyday visually guided behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Episodic memory and episodic future thinking in adults with autism.

The ability to remember past experiences (episodic memory) is thought to be related to the ability to imagine possible future experiences (episodic future thinking). Although previous research has established that individuals with autism spectrum disorder (ASD) have diminished episodic memory, episodic future thinking has not previously been investigated within this population. In the present study, high-functioning adults with ASD were compared to closely matched typical adults on a task requiring participants to report a series of events that happened to them in the past and a series of events that might happen to them in the future. For each event described, participants completed two modified Memory Characteristics Questionnaire items to assess self-reported phenomenal qualities associated with remembering and imagining, including self-perspective and degree of autonoetic awareness. Participants also completed letter, category, and ideational fluency tasks. Results indicated that participants with ASD recalled/imagined significantly fewer specific events than did comparison participants and that participants with ASD demonstrated impaired episodic memory and episodic future thinking. In line with this finding, participants with ASD were less likely than comparison participants to report taking a field (first-person) perspective and were more likely to report taking an observer (third-person) perspective during retrieval of past events (but not during simulation of future events), highlighting that they were less likely to mentally reexperience past events from their own point of view. There were no group differences in self-reported levels of autonoetic awareness or fluency task performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parallel memory retrieval in dual-task situations: II. Episodic memory.

Three experiments asked whether subjects could retrieve information from a 2nd stimulus while they retrieved information from a 1st stimulus. Ss performed recognition judgments on each of 2 words that followed each other by 0, 250, and 1,000 msec (Experiment 1) or 0 and 300 msec (Experiments 2 and 3). In each experiment, reaction time to both stimuli was faster when the 2 stimuli were both targets (on the study list) or both lures (not on the study list) than when 1 was a target and the other was a lure. Each experiment found priming from the 2nd stimulus to the lst when both stimuli were targets. Reaction time to the 1st stimulus was faster when the 2 targets came from the same memory structure at study (columns in Experiment l; pairs in Experiment 2; sentences in Experiment 3) than when they came from different structures. This priming is inconsistent with discrete serial retrieval and consistent with parallel retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Episodic, generalized, and semantic memory tests: Switching and strength effects.

We continue the process of investigating the probabilistic paired associate paradigm in an effort to understand the memory access control processes involved and to determine whether the memory structure produced is in transition between episodic and semantic memory. In this paradigm two targets are probabilistically paired with a cue across a large number of short lists. Participants can recall the target paired with the cue in the most recent list (list specific test), produce the first of the two targets that have been paired with that cue to come to mind (generalised test), and produce a free association response (semantic test). Switching between a generalised test and a list specific test did not produce a switching cost indicating a general similarity in the control processes involved. In addition, there was evidence for a dissociation between two different strength manipulations (amount of study time and number of cue-target pairings) such that number of pairings influenced the list specific, generalised and the semantic test but amount of study time only influenced the list specific and generalised test. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Destination memory impairment in older people.

Older adults are assumed to have poor destination memory—knowing to whom they tell particular information—and anecdotes about them repeating stories to the same people are cited as informal evidence for this claim. Experiment 1 assessed young and older adults' destination memory by having participants tell facts (e.g., “A dime has 118 ridges around its edge”) to pictures of famous people (e.g., Oprah Winfrey). Surprise recognition memory tests, which also assessed confidence, revealed that older adults, compared to young adults, were disproportionately impaired on destination memory relative to spared memory for the individual components (i.e., facts, faces) of the episode. Older adults also were more confident that they had not told a fact to a particular person when they actually had (i.e., a miss); this presumably causes them to repeat information more often than young adults. When the direction of information transfer was reversed in Experiment 2, such that the famous people shared information with the participants (i.e., a source memory experiment), age-related memory differences disappeared. In contrast to the destination memory experiment, older adults in the source memory experiment were more confident than young adults that someone had shared a fact with them when a different person actually had shared the fact (i.e., a false alarm). Overall, accuracy and confidence jointly influence age-related changes to destination memory, a fundamental component of successful communication. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anhedonia and the experience of emotion in individuals with schizophrenia.

Research shows that individuals with schizophrenia report symptoms of anhedonia when assessed by interview or questionnaire. However, when presented with emotional stimuli, they report emotional experiences that are similar to those of control participants. The authors hypothesized that deficits in working memory and episodic memory contribute to such discrepancies. They administered measures of working and episodic memory, self-report anhedonia questionnaires, and several types of emotional stimuli to 49 individuals with schizophrenia and 47 control participants. All participants reported experiencing similar amounts of pleasant-unpleasant emotion (valence) in response to stimuli, but individuals with schizophrenia reported experiencing less arousal for negative stimuli. Individuals with schizophrenia also reported greater social and physical anhedonia on a traditional anhedonia questionnaire. Disturbances in working memory moderated the relationship between physical anhedonia and participants' emotional experience of positive stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of aging on the neural correlates of successful item and source memory encoding.

To investigate the neural basis of age-related source memory (SM) deficits, young and older adults were scanned with fMRI while encoding faces, scenes, and face-scene pairs. Successful encoding activity was identified by comparing encoding activity for subsequently remembered versus forgotten items or pairs. Age deficits in successful encoding activity in hippocampal and prefrontal regions were more pronounced for SM (pairs) as compared with item memory (faces and scenes). Age-related reductions were also found in regions specialized in processing faces (fusiform face area) and scenes (parahippocampal place area), but these reductions were similar for item and SM. Functional connectivity between the hippocampus and the rest of the brain was also affected by aging; whereas connections with posterior cortices were weaker in older adults, connections with anterior cortices, including prefrontal regions, were stronger in older adults. Taken together, the results provide a link between SM deficits in older adults and reduced recruitment of hippocampal and prefrontal regions during encoding. The functional connectivity findings are consistent with a posterior-anterior shift with aging previously reported in several cognitive domains and linked to functional compensation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual–spatial episodic memory in schizophrenia: A multiple systems framework.

Objective: Enhanced understanding of cognitive deficits, and the neurobiological abnormalities that mediate them, can be achieved through translational research that employs comparable experimental approaches across species. This study employed a multiple-systems framework derived from the rodent literature to investigate visual–spatial memory abilities associated with schizophrenia. Method: Using the bin task, a human analog of rodent maze tasks, everyday objects were hidden in visually identical bins. Following a 1-min filled delay, participants with schizophrenia-spectrum disorders (n = 30) and healthy community controls (n = 30) were asked to identify both the object hidden and bin used on the basis of its spatial location. Three dimensions of visual–spatial memory were contrasted: (a) memory for spatial locations versus memory for objects, (b) allocentric (viewpoint independent) versus egocentric (body-centered) spatial representations, and (c) event (working) memory versus reference memory. Results: Most pronounced was a differential deficit in memory for spatial locations under allocentric (p = .005, d = ?0.77) but not egocentric viewing conditions (p = .298, d = ?0.28) in the schizophrenia group relative to healthy controls. Similarly, schizophrenia-related spatial memory deficits were pronounced under demands for event memory (p = .004, d = ?0.77) but not reference memory (p = .171, d = ?0.33). Conclusions: These results support a heuristic of preferential deficits in hippocampal-mediated forms of memory in schizophrenia. Moreover, the task provides a useful paradigm for translational research and the pattern of deficits suggests that persons with schizophrenia may benefit from mnemonic approaches favoring egocentric representations and consistency when interacting with our visual–spatial world. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of environmental context on recognition memory and claims of remembering.

Recognition memory for words was tested in same or different contexts using the remember/know response procedure. Context was manipulated by presenting words in different screen colors and locations and by presenting words against real-world photographs. Overall hit and false-alarm rates were higher for tests presented in an old context compared to a new context. This concordant effect was seen in both remember responses and estimates of familiarity. Similar results were found for rearranged pairings of old study contexts and targets, for study contexts that were unique or were repeated with different words, and for new picture contexts that were physically similar to old contexts. Similar results were also found when subjects focused attention on the study words, but a different pattern of results was obtained when subjects explicitly associated the study words with their picture context. The results show that subjective feelings of recollection play a role in the effects of environmental context but are likely based more on a sense of familiarity that is evoked by the context than on explicit associations between targets and their study context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Automatic hypermnesia and impaired recollection in schizophrenia.

Evidence from studies of nonmnemonic automatic cognitive processes provides reason to expect that schizophrenia is associated with exaggerated automatic memory (implicit memory), or automatic hypermnesia. Participants with schizophrenia (n?=?22) and control participants (n?=?26) were compared on word stem completion (WSC) and list discrimination (LD) tasks administered using the process dissociation procedure. Unadjusted, extended measurement model and dual-process signal-detection methods were used to estimate recollection and automatic memory indices. Schizophrenia was associated with automatic hypermnesia on the WSC task and impaired recollection on both tasks. Thought disorder was associated with even greater automatic hypermnesia. The absence of automatic hypermnesia on the LD task was interpreted with reference to the neuropsychological bases of context and content memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Patterns of prospective and retrospective memory impairment in preclinical Alzheimer's disease.

Forty-six preclinical Alzheimer's disease (AD) participants and 188 nondemented control persons from the Kungsholmen Project (L. B?ckman et al., 2004) were compared on prospective memory (ProM) and retrospective memory (RetM) tasks 3 years before dementia diagnosis. The preclinical AD participants showed deficits in both ProM and RetM. Most interestingly, logistic regression analyses revealed that ProM made an independent contribution to the prediction of AD over and above that of RetM. This finding suggests that ProM and RetM tap partly different cognitive operations. Furthermore, within the ProM task, both the retrospective and prospective components were similarly impaired in preclinical AD. Within RetM, the preclinical AD participants were impaired on indices of encoding, storage (forgetting), and retrieval of information. Hence, the findings indicate a rather global episodic memory impairment in preclinical AD that cuts across type of memory assessed (ProM and RetM) as well as across different components of both the ProM and RetM tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amount of postcue encoding predicts amount of directed forgetting.

In list-method directed forgetting, participants are cued to intentionally forget a previously studied list (List 1) before encoding a subsequently presented list (List 2). Compared with remember-cued participants, forget-cued participants typically show impaired recall of List 1 and improved recall of List 2, referred to as List 1 forgetting and List 2 enhancement. In 3 experiments, we examined how amount of postcue encoding influences directed forgetting. Two results emerged dissociating List 1 forgetting from List 2 enhancement. First, an increase in amount of postcue encoding led to an increase in List 1 forgetting but did not affect List 2 enhancement. Second, the forget cue influenced all List 1 items but affected only early List 2 items. A 2-mechanism account of directed forgetting is suggested, according to which List 1 forgetting reflects reduced accessibility of List 1 items, and List 2 enhancement arises from a reset of encoding processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recollection- and familiarity-based memory in healthy aging and amnestic mild cognitive impairment.

Little is known about the cognitive mechanisms of the memory impairment associated with amnestic mild cognitive impairment (aMCI). We explored recollection and familiarity in 27 healthy young adults, 45 healthy older adults, and 17 individuals with aMCI. Relative to the younger adults, recollection was reduced in the older adults, especially among those with aMCI. Familiarity did not differ among groups. In the healthy younger and older adults, better performance on a set of clinical memory measures that are sensitive to medial temporal lobe functioning was associated with greater recollection. In addition, among the healthy older adults better executive functioning was also associated with greater recollection. These results are consistent with the notion that recollection is a product of strategic processes mediated by the prefrontal cortex that suppport the retrieval of context-dependent memories from the hippocampus. Hippocampal atrophy associated with aMCI may disrupt this brain network, and thereby interfere with recollection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of memory activation in creating false memories of encoding context.

Using 3 experiments, I examined false memory for encoding context by presenting Deese–Roediger–McDermott themes (Deese, 1959; Roediger & McDermott, 1995) in usual-looking fonts and by testing related, but unstudied, lure items in a font that was shown during encoding. In 2 of the experiments, testing lure items in the font used to study their associated themes increased false recognition relative to testing lure items in a font that was used to study a different lure’s theme. Further, studying a larger number of associates exacerbated the influence of testing lure items in a font used to study their associated themes. Finally, testing lures in a font that was encoded many times, but was not used to present the lures’ studied associates, increased lure errors more than testing lures in a font that was encoded relatively fewer times. These results favor the explanation of false recognition offered by global-matching models of recognition memory over the explanations of activation-monitoring theory and fuzzy-trace theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging effects on memory encoding in the frontal lobes.

Functional magnetic resonance imaging (fMRI) was used to compare frontal-lobe activation in younger and older adults during encoding of words into memory. Participants made semantic or nonsemantic judgements about words. Younger adults exhibited greater activation for semantic relative to nonsemantic judgements in several regions, with the largest activation in the left inferior frontal gyrus. Older adults exhibited greater activation for semantic judgments in the same regions, but the extent of activation was reduced in left prefrontal regions. In older adults, there was a significant association between behavioral tests of declarative and working memory and extent of frontal activation. These results suggest that age-associated decreases in memory ability may be due to decreased frontal-lobe contributions to the initial encoding of experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)