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Subjective qualities of memories associated with the picture superiority effect in schizophrenia.

Patients with schizophrenia (n = 24) matched with 24 normal subjects were presented with both words and pictures. On a recognition memory task, they were asked to give remember, know, or guess responses to items that were recognized on the basis of conscious recollection, familiarity, or guessing, respectively. Compared with normal subjects, patients exhibited a lower picture superiority effect selectively related to remember responses. Unlike normal subjects, they did not exhibit any word superiority effect in relation to guess responses; this explains why the overall picture superiority effect appeared to be intact. These results emphasize the need to take into account the subjective states of awareness when analyzing memory impairments in schizophrenia.

Adult↗

Memory and learning in pediatric bipolar disorder.

OBJECTIVE: To test the hypothesis that patients with pediatric bipolar disorder (PBPD) would demonstrate impairment relative to diagnosis-free controls of comparable age, gender, and IQ on measures of memory functioning. METHOD: The authors administered a battery of verbal and visuospatial memory tests to 35 outpatients with PBPD and 20 healthy controls who participated as volunteers in this study. Groups did not differ on age, gender, or IQ. RESULTS: Consistent with findings in adults with BPD, patients with PBPD performed more poorly than controls on measures of verbal learning/memory and delayed facial recognition memory. Impaired memory was particularly evident in patients with comorbid PBPD/attention-deficit/hyperactivity disorder or acute mood symptoms. CONCLUSIONS: These findings suggest that deficits in verbal learning and memory, as well as some aspects of visuospatial memory, characterize patients with narrow phenotype PBPD. Further research is needed, however, to clarify the roles of comorbid attention-deficit/hyperactivity disorder and acute mood state in the emergence of these deficits. Given the apparent continuity in memory dysfunction between adult BPD and narrow phenotype PBPD, research aimed at elucidating underlying neural mechanisms for this set of deficits is warranted.

Bipolar Disorder↗

Decreased activity in inferotemporal cortex during explicit memory: dissociating priming, novelty detection, and recognition.

Studies of non-human primates have shown that activity in inferotemporal (IT) brain regions decrease over repeated stimulus exposure, a phenomenon known as repetition suppression. In the present study, repetition suppression was examined during recognition of personally experienced events (explicit memory). Brain activity was measured while subjects encoded and subsequently recognized scenic pictures. First, two recognition conditions were compared; one that mainly included familiar pictures and one that mainly included novel pictures. Responses derived from this contrast may reflect recognition memory, perceptual priming, or novelty detection. To test specifically for responses associated with recognition memory, subjects encoded a new set of pictures followed by two recognition tests. All test pictures had been presented during the course of the experiment, and the subjects identified pictures that appeared in the second encoding list. Since all pictures were familiar, repetition suppression was specifically associated with recognition memory. In the first contrast, relative change in brain activity was observed in inferotemporal, extra-striate, and hippocampal regions during recognition of familiar versus novel pictures. In the second contrast, decreased activity in IT cortex was found. The location of this region overlapped with that for the region identified in the first contrast, and a conjunction analysis showed that reduced activity in left IT cortex was common to both contrasts. These results suggest that repetition suppression in IT cortex reflects recognition memory, and that such a response is not a simple function of stimulus repetition but can be modulated by top-down processing.

Adult↗

Neuropsychological deficit in early subcortical vascular dementia: comparison to Alzheimer's disease.

To further clarify the cognitive syndrome in subcortical vascular dementia (VaD), we investigated 20 patients with early-stage VaD as compared with 30 patients with Alzheimer's disease (AD) and 22 normal controls using episodic memory, attention/executive function and language tests. The patient groups were closely matched in terms of age, education and severity of dementia. The VaD patients had a significantly better free recall, cued recall and recognition memory than AD patients, the recognition being within normal limits in VaD. In addition, VaD patients had a greater number of perseverative errors during the Modified Card Sorting test, while AD patients exhibited more perseverations of semantic fluency. The results of retrieval deficit syndrome and increased number of perseverations during tasks sensitive to frontal lobe function are in agreement with the studies emphasizing the importance of frontal dysfunction in subcortical VaD. These findings are relevant for the early diagnosis of VaD and might be useful in the differential diagnosis with AD.

Aged↗

Bilateral dorsolateral thalamic lesions disrupts conscious recollection.

In an earlier study we disputed the claim that the mediodorsal thalamic nucleus is critical for familiarity. We reported patient (QX) who showed a severe deficit in conscious recollection, and behavioural problems (disinhibition, emotional lability) with relative sparing of familiarity-aware memory following a left mediodorsal thalamic lesion. More recent MR imaging has revealed that QX's lesions are more extensive than previously reported and involve both dorsolateral thalamic nuclei, and whilst there is evidence of left mediodorsal thalamic damage, it is not the main focus of damage. This paper reports a full analysis of QX's thalamic pathology alongside a more detailed investigation of his recognition memory, using yes/no and forced-choice procedures, and executive function. The results revealed impairments in yes/no recognition and conscious recollection rates of famous, artist and unknown names. In addition to the previously noted behavioural disinhibition and emotional lability, a deficit in spontaneous planning ability was evident on the Zoo Map Test (subtest of the Bahavioural Assessment of the Dysexecutive Syndrome). Forced-choice recognition, familiarity estimates and remote memory showed higher levels of preservation. The findings indicate that the dorsolateral thalamus is part of the extended hippocampal circuit which is causally critical only for recall and conscious recollection of complex associations rather than for the more automatic processes linked with novelty detection.

Brain Injuries↗

Olfactory learning: convergent findings from lesion and brain imaging studies in humans.

The role of temporal lobe structures in olfactory memory was investigated by (i) the examination of odour learning and memory in patients who had undergone resection from a temporal lobe (including primary olfactory regions) for the treatment of intractable epilepsy; and (ii) the examination of brain function during odour memory tasks as assessed via PET imaging of healthy individuals. In order to study different stages of odour memory, recognition of a 'list' of odours was tested after a first exposure, again after four exposures and once more after a 24 h delay interval. Patients with resection from a temporal lobe performed significantly less well than control subjects on all trials, and no significant differences were noted as a function of side of resection, indicating that there is not a strong hemispheric superiority for this task. The PET data yielded different levels of activity in piriform cortex (primary olfactory cortex), in relation to the 'no-odour' baseline scan, depending on the type of processing: no increase in activity noted during odour encoding, a small increase bilaterally during short-term recognition and a larger increase bilaterally during long-term recognition. These findings, together with findings in animal studies, suggest that piriform cortex may have an active role in odour memory processing, not simply in odour perception. Taken together, the findings from the lesion study and functional brain imaging of healthy subjects suggest that olfactory memory requires input from left and right temporal lobe regions for optimal odour recognition, and that, unlike with verbal or non-verbal visual material, there is not a strong functional lateralization for olfactory memory.

Adult↗

An electrophysiological analysis of altered cognitive functions in Huntington disease.

BACKGROUND: Neuropsychological deficits are a main feature of Huntington disease (HD) with previous data suggesting involvement of memory functions and visual processing. OBJECTIVE: To increase the knowledge about cognitive malfunction in HD in the domains of visual processing and memory by the use of modern electrophysiological techniques (event-related potentials [ERPs]). DESIGN: A case-control design was used. Three ERP paradigms were used; a parallel visual search paradigm allowed for the simultaneous processing of a multi-element visual array in search of a target stimulus, while a serial search paradigm with varied numbers of distractor items necessitated a serial one by one scanning of the arrays. The third experiment was a word-recognition memory task. SETTING: The measurements were obtained in a neurophysiological laboratory of a university hospital. PATIENTS AND CONTROLS: Nine patients with HD and 9 control subjects matched for age, sex, and education were studied. MAIN OUTCOME MEASURES: Components of averaged ERPs were quantified by latency and amplitude measures and subjected to statistical analysis. Behavioral measures (search time, hit rate, and recognition accuracy) were assessed as well. RESULTS: The early visual components showed a significant latency shift (delay of about 50 milliseconds) in HD. In the search paradigms the P3 components differentiating target and standard stimuli were virtually absent in HD as was the ERP effect indexing word recognition. This was accompanied by a marked delay in search times and lower hit rates in the search tasks and a grossly reduced recognition accuracy in the memory task. CONCLUSIONS: The results suggest marked impairments of patients with HD in early visual sensory processing (early components). Deficits in visual search might be attributed to an impairment to deploy attentional resources across the visual field and/or an inability to control eye movements. The ERPs in the memory task differed grossly from similar data obtained by others in patients with Alzheimer disease, suggesting a different neural basis for the amnesia in HD.

Adult↗

Dissociable medial temporal lobe contributions to social memory.

Medial temporal lobe structures such as the hippocampus have been shown to play a critical role in mnemonic processes, with additional recruitment of the amygdala when memories contain emotional content. Thus far, studies that have examined the relationship between amygdala activity and memory have typically relied on emotional content of the kind that is rarely encountered in day-to-day interactions. The present event-related functional magnetic resonance imaging study investigates whether amygdala activity supports emotional memory during the more subtle social interactions that punctuate everyday life. Across four training sessions, subjects learned common first names for unfamiliar faces in the presence or absence of additional contextual information that was positive, negative, and neutral in valence (e.g., "Emily helps the homeless," "Bob is a deadbeat dad," "Eric likes carrots"). During scanning, subjects performed a yes/no recognition memory test on studied and novel faces. Results revealed a functional dissociation within the medial temporal lobe. Whereas a region within the right hippocampus responded strongly to all faces that had been paired with a description, regardless of its valence, activity in the right amygdala was uniquely sensitive to faces that had been previously associated with emotional descriptions (negative and positive > neutral). This pattern of activity in the amygdala was preserved even when the emotional contexts associated with faces could not be explicitly retrieved, suggesting a role for the amygdala in providing a nonspecific arousal indicator in response to viewing individuals with emotionally colored pasts.

Adolescent↗

Effects of sophistication and motivation on the detection of malingered memory performance using a computerized forced-choice task.

The present study employed a computerized forced-choice recognition memory task, the Multi-Digit Memory Test (MDMT), to examine the effects of instructional set (i.e., dissimulation information provided subjects) and motivation (i.e., monetary incentive) on simulated malingering behavior in a group of 119 university undergraduate students and 33 patients sustaining varying severity of closed-head injury. For the nonpatient groups, a significant effect of instructional set was revealed. Motivational incentive, however, did not affect forced-choice performance. Overall, significant performance differences emerged between all groups with nonmalingering students performing nearly perfectly, the brain-injured patients performing well above chance levels, sophisticated student malingers performing at chance, and naive student malingers performing well below chance levels. These results suggest the MDMT may offer a clinically useful and convenient addition to a neuropsychological assessment when there is suspicion of feigned memory problems. These data also support the use of naive and sophisticated malingering subjects in further analog studies addressing this topic.

Adult↗

Social memory, social stress, and economic behaviors.

Social memory plays a pivotal role in social behaviors, from mating behaviors to cooperative behaviors based on reciprocal altruism. More specifically, social/person recognition memory is supposed, by behavioral-economic and game-theoretic analysis, to be required for tit-for-tat like cooperative behaviors to evolve under the N-person iterated prisoner's dilemma game condition. Meanwhile, humans are known to show a social stress response during face-to-face social interactions, which might affect economic behaviors. Furthermore, it is known that there are individual differences in a social stress response, which might be reflected in individual differences in various types of economic behaviors, partially via different capacities of social memory. In the present study, we investigated the acute effects of social stress-induced free cortisol (a stress hormone) elevation on hippocampus-dependent social memory by utilizing the Trier social stress test (consisting of a public speech and a mental arithmetic task). We also examine the correlation between an economic behavior-related personality trait (i.e., general trust scale) and social stress-induced cortisol elevations. We found that (1) social stress acutely impairs social memory during social interaction and (2) interpersonal trust reduces social stress response. Together, interpersonal trust may modulate economic behaviors via stress hormone's action on social cognition-related brain regions.

Adult↗

Intact suppression of increased false recognition in schizophrenia.

OBJECTIVE: Recognition memory is impaired in patients with schizophrenia, as they rely largely on item familiarity, rather than conscious recollection, to make mnemonic decisions. False recognition of novel items (foils) is increased in schizophrenia and may relate to this deficit in conscious recollection. By studying pictures of the target word during encoding, healthy adults can suppress false recognition. This study examined the effect of pictorial encoding on subsequent recognition of repeated foils in patients with schizophrenia. METHOD: The study included 40 patients with schizophrenia and 32 healthy comparison subjects. After incidental encoding of 60 words or pictures, subjects were tested for recognition of target items intermixed with 60 new foils. These new foils were subsequently repeated following either a two- or 24-word delay. Subjects were instructed to label these repeated foils as new and not to mistake them for old target words. RESULTS: Schizophrenic patients showed greater overall false recognition of repeated foils. The rate of false recognition of repeated foils was lower after picture encoding than after word encoding. Despite higher levels of false recognition of repeated new items, patients and comparison subjects demonstrated a similar degree of false recognition suppression after picture, as compared to word, encoding. CONCLUSIONS: Patients with schizophrenia displayed greater false recognition of repeated foils than comparison subjects, suggesting both a decrement of item- (or source-) specific recollection and a consequent reliance on familiarity in schizophrenia. Despite these deficits, presenting pictorial information at encoding allowed schizophrenic subjects to suppress false recognition to a similar degree as the comparison group, implying the intact use of a high-level cognitive strategy in this population.

Adult↗

Emotional memories are not all created equal: evidence for selective memory enhancement.

Human brain imaging studies have shown that greater amygdala activation to emotional relative to neutral events leads to enhanced episodic memory. Other studies have shown that fearful faces also elicit greater amygdala activation relative to neutral faces. To the extent that amygdala recruitment is sufficient to enhance recollection, these separate lines of evidence predict that recognition memory should be greater for fearful relative to neutral faces. Experiment 1 demonstrated enhanced memory for emotionally negative relative to neutral scenes; however, fearful faces were not subject to enhanced recognition across a variety of delays (15 min to 2 wk). Experiment 2 demonstrated that enhanced delayed recognition for emotional scenes was associated with increased sympathetic autonomic arousal, indexed by the galvanic skin response, relative to fearful faces. These results suggest that while amygdala activation may be necessary, it alone is insufficient to enhance episodic memory formation. It is proposed that a sufficient level of systemic arousal is required to alter memory consolidation resulting in enhanced recollection of emotional events.

Adolescent↗

Memory for pictures, words, and spatial location in older adults: evidence for pictorial superiority.

In the present study the spatial location of picture and word stimuli was varied across four quadrants of photographic slides. Young and old people received either pictures or words to study and were told to remember either just the item or the item and its location. Recognition memory for items and memory for spatial location were tested. A pictorial superiority effect occurred for both old and young people's item recognition. Additionally, instructions to study position decreased item memory and facilitated position memory in both age groups. Spatial memory was markedly superior for pictures compared with matched words for old and young adults. The results are interpreted within the Hasher and Zacks framework of automatic processing. The implications of the data for designing mnemonic aids for elderly persons are considered.

Adolescent↗

Short- and long-delay intracranial ERP repetition effects dissociate memory systems in the human brain.

Prior exposure to a stimulus can facilitate the performance to subsequent presentations of that stimulus. ERP studies have shown that this facilitation is associated with the modulation of two components (N400 and P600). Investigation of the time course of both behavioral and ERP repetition effects have led to the assumption that it is subserved by the combination of at least two mechanisms operating at different time-points: a short-delay semantic activation and a long-lasting episodic mechanism. The present experiment recorded intracranial ERPs from various structures during a continuous recognition memory task to investigate the respective contribution of the different brain regions to short- and long-delay ERP repetition effects. The results are in good agreement with both the classical neuropsychological literature and the more recent data obtained with functional imagery techniques. They provide electrophysiological evidence of multiple anatomo-functional memory systems in the human brain: a short-term semantic activation system and a long-term episodic memory system, with interface structures that coordinate the functioning of these two systems.

Adolescent↗

Impairment of specific episodic memory processes by sub-psychotic doses of ketamine: the effects of levels of processing at encoding and of the subsequent retrieval task.

RATIONALE: The precise nature of the impact of the N-methyl-D-aspartate antagonist, ketamine, upon human episodic memory, has yet to be elucidated fully. OBJECTIVES: This study sought to assess the effects of ketamine on the sub-processes facilitating memory encoding and retrieval. METHODS: We evaluated the effects of the drug on a series of memory performance measures depending upon whether it was administered at the encoding or retrieval stage and on the nature of the encoding task used. Twelve healthy volunteers participated in a double-blind, placebo-controlled, randomized, within-subjects study. Intravenous infusions of placebo, 50 ng/ml ketamine or 100 ng/ml ketamine were administered. We investigated the effects of ketamine on three key aspects of episodic memory: encoding vs retrieval processes, source memory, and depth of processing. Data were analysed using both multinomial modelling and standard measures of item discrimination and response bias. RESULTS: Deleterious effects of ketamine on episodic memory were primarily attributable to its effects on encoding, rather than retrieval processes. Recognition memory was impaired for items encoded at an intermediate level of processing, but preserved for shallowly and deeply encoded items. Increased source guessing bias was also observed when encoding took place under ketamine. CONCLUSIONS: The effects of ketamine upon episodic memory seem, therefore, to predominate at encoding. Furthermore, our results are also consistent with a specific impairment of encoding processes that result in subsequent recollective, as opposed to familiarity-based, retrieval. The observed effects are compatible with memory deficits seen in schizophrenia and thus provide some support for the ketamine model of the disease.

Adolescent↗

Complementary remedy of aged-related learning and memory deficits via exogenous choline acetyltransferase.

The present study aimed to examine whether the aged mice with naturally occurring cognitive deficits in learning and memory would benefit from supplementation of choline acetyltransferase (ChAT), the biosynthetic enzyme for neurotransmitter acetylcholine. Delivered by protein transduction domain (PTD), ChAT could pass through the blood-brain barrier, enter the neurons, interact with heat shock protein 70kDa, and retain enzyme activity. In behavior tests, PTD-ChAT given to the aged and memory-deficient mice almost completely reversed the behavioral changes, such as impairment of memory retention in the step-through test (an index of long-term memory) and prolonged swimming time in water maze test (an index of spatial recognition memory). The results suggest a novel and potential therapeutic use of PTD-ChAT in the age-related cognitive deficits.

Aging↗

Impulsivity in youth predicts early age-related cognitive deficits in rats.

Impulsivity is a feature of psychiatric disorders such as mania, addictive behaviors or attention deficit-hyperactivity disorder (ADHD), which has recently been related to complaints of forgetfulness in adults. We investigated whether impulsiveness exerts a long-term influence on cognitive function in rats in a longitudinal study. Impulsivity, assessed by the ability to complete a sequence of presses to obtain food (conditioning box), spatial working memory (8-arm radial maze) assessed with varying degree of attentional load and recognition memory (Y-maze) were tested at different ages. Marked individual differences in impulsivity were observed at youth and remained stable at middle-age despite a general decline in the trait. Working memory scores of impulsive and non-impulsive rats did not differ in youth, whereas by middle-age the impulsive group had impaired working memory and was more sensitive to a higher attentional demand. Thus, impulsiveness in youth predicts cognitive performance in middle-age. These findings may help refine the search for early biological substrates of successful aging and for preventive follow-up of subjects at risk of impaired cognitive aging.

Age Factors↗

Variations in lateralized processing among right-handers: effects on patterns of cognitive performance.

Two experiments investigated whether individual differences among right-handers in patterns of lateralized processing were related to level of performance on a variety of cognitive tasks presented under non-tachistoscopic conditions. Subjects were divided into two groups of individuals, those who characteristically have greater than average right-hemisphere involvement in functioning and those who characteristically have greater than average left-hemisphere involvement. In the first experiment we examined whether characteristic individual differences in hemispheric involvement could predict performance on a facial memory task. The group with relatively greater right-hemisphere involvement had better recognition memory than the group with relatively greater left-hemisphere involvement. In the second experiment, we examined whether individual differences in hemispheric involvement could predict performance on a larger set of cognitive tasks. The groups were administered two tasks selected to evaluate left-hemisphere function and two selected to evaluate right-hemisphere function. The results indicated that the groups differed in their profile of cognitive performance. Individuals with greater than average right-hemisphere involvement in processing tended to perform better on tasks indexing right-hemisphere function than on tasks indexing left-hemisphere function, whereas the opposite was true of individuals with greater than average left-hemisphere involvement. Collectively, the results of these two experiments indicate that individual differences in lateralized performance have important implications for individual differences in patterns of cognitive ability.

Adult↗