Item Memory Task Research Articles

Not so different after all? An event-related potential study on item and source memory for object-scene pairs in German and Chinese young adults.

In recent years, several cross-cultural studies reported that Westerners focus more on central aspects of a scene (e.g., an object) relative to peripheral aspects (e.g., the background), whereas Easterners more evenly allocate attention to central and peripheral aspects. In memory tasks, Easterners exhibit worse recognition for the central object when peripheral aspects are changed, whereas Westerners are less affected by peripheral changes. However, most of these studies rely on hit rates without correcting for response bias, whereas studies accounting for response bias failed to replicate cultural differences in memory tasks. In this event-related potential (ERP) study, we investigated item and source memory for semantically unrelated object-scene pairs in German and Chinese young adults using memory measures corrected for response bias (i.e., the discrimination index Pr). Both groups completed study-test cycles with either item memory tests or source memory tests. In item memory blocks, participants completed an old/new recognition test for the central object. Source memory blocks entailed an associative recognition test for the association between object and background. Item and source memory were better for intact than for recombined pairs. However, as verified with frequentist and Bayesian analyzes, this context effect was not modulated by culture. The ERP results revealed an old/new effect for the item memory task in both groups which was again not modulated by culture. Our findings suggest that cultural differences in young adults do not manifest in intentional memory tasks probing memory for object-scene pairs without semantic relations when using bias-corrected memory measures.

Benefits and Detriments of Social Collaborative Memory in Turn-Taking and Directed Forgetting.

Collaborative recall by groups of people can evoke both memory detriments (e.g., collaborative inhibition) and benefits (e.g., error pruning and post-collaborative memory benefit). Yet, it remains indeterminate whether these effects are due to the emotional valence of stimuli and/or the specific subtypes of episodic memory tested (i.e., item memory and source memory), and whether they are related to the research procedure of directed forgetting (DF). We introduced item-method DF into collaborative memory research using a turn-taking procedure. The to-be-recalled words were studied in different emotional valences and were followed by either an R or F cue, which, respectively, instructed participants to remember or forget the words presented. We conducted two recall sessions (Recall 1 and Recall 2) that included the two subtypes of episodic memory. Recall 1 was performed either individually or collaboratively, while Recall 2 was always performed individually. We observed three major findings: (a) a collaborative memory decrement - collaborative inhibition - was minimally affected in both item memory and source memory tasks by either the emotional valence of the stimuli or the DF cue; (b) a collaborative memory benefit - error pruning of item memory - persisted within both ongoing and post-collaboration, while error pruning of source memory only presented in ongoing collaboration, thus demonstrating the relevance of dual-process models that differentiate automatic familiarity and effortful recollection processes; and (c) there was no post-collaborative memory benefit, indicating the importance of the type of collaborative procedure. We discuss these results in terms of various theories, including the retrieval strategy disruption hypothesis (RSDH) which asserts that memory strategies tend to be disrupted in collaboration but are facilitated within post-collaboration. Also, we describe the implications of these results and directions for exploring other influential factors in future research.

Task-dependent effects of intracranial hippocampal stimulation on human memory

Abstract Background: Despite its potential to revolutionize the treatment of memory dysfunction, the efficacy of direct electrical hippocampal stimulation for memory performance has not yet been well characterized. One of the main challenges to cross-study comparison in this area of research is the diversity of the cognitive tasks used to measure memory performance. Objective: We hypothesized that the tasks that differentially engage the hippocampus may be differentially influenced by hippocampal stimulation and the behavioral effects would be related to the underlying hippocampal activity. Methods: To investigate this issue, we recorded intracranial EEG from and directly applied stimulation to the hippocampus of 10 epilepsy patients while they performed two different verbal memory tasks e a word pair associative memory task and a single item memory task. Results: Hippocampal stimulation modulated memory performance in a task-dependent manner, improving associative memory performance, while impairing item memory performance. In addition, subjects with poorer baseline cognitive function improved much more with stimulation. iEEG recordings from the hippocampus during non-stimulation encoding blocks revealed that the associative memory task elicited stronger theta oscillations than did item memory and that stronger theta power was related to memory performance. Conclusions: We show here for the first time that stimulation-induced associative memory enhancement was linked to increased theta power during retrieval. These results suggest that hippocampal stimulation enhances associative memory but not item memory because it engages more hippocampal theta activity and that, in general, increasing hippocampal theta may provide a neural mechanism for successful memory enhancement. Keywords: Memory enhancement, iEEG, deep brain stimulation, hippocampus

Entorhinal tau is associated with increased hippocampal activation and memory deficits in Alzheimer’s disease

AbstractBackgroundTo date, it remains unclear how the hallmark pathological changes of Alzheimer’s disease (AD), amyloid plaques, and neurofibrillary tangles, affect neuronal activity and, consequently, cognition. In cognitively normal aging, it appears that tau accumulation may drive hippocampal hyperactivity, however, studies investigating this association in AD are sparse.MethodPatients with mild cognitive impairment (MCI) or mild dementia due to AD (n = 15) underwent positron emission tomography with the tracer [18F]‐AV‐1451, which binds to tau accumulation, and performed a visual item memory task during functional magnetic resonance imaging.ResultEntorhinal tau accumulation was highly correlated with memory‐related hippocampal activation. Greater tau accumulation and hippocampal activation were negatively correlated with memory performance. Neural activation in other task‐related structures was not correlated with local or global tau accumulation.ConclusionSimilar to observations in cognitively healthy aging, entorhinal tau accumulation is closely associated with hippocampal hyperactivity and impaired memory performance in MCI and mild dementia. Interestingly, this association is specific for medial temporal lobe structures.

Entorhinal Tau Predicts Hippocampal Activation and Memory Deficits in Alzheimer's Disease.

To date, it remains unclear how amyloid plaques and neurofibrillary tangles are related to neural activation and, consequently, cognition in Alzheimer's disease (AD). Recent findings indicate that tau accumulation may drive hippocampal hyperactivity in cognitively normal aging, but it remains to be elucidated how tau accumulation is related to neural activation in AD. To determine whether the association between tau accumulation and hippocampal hyperactivation persists in mild cognitive impairment (MCI) and mild dementia or if the two measures dissociate with disease progression, we investigated the relationship between local tau deposits and memory-related neural activation in MCI and mild dementia due to AD. Fifteen patients with MCI or mild dementia due to AD underwent a neuropsychological assessment and performed an item memory task during functional magnetic resonance imaging. Cerebral tau accumulation was assessed using positron emission tomography and [18F]-AV-1451. Entorhinal, but not global tau accumulation, was highly correlated with hippocampal activation due to visual item memory encoding and predicted memory loss over time. Neural activation in the posterior cingulate cortex and the fusiform gyrus was not significantly correlated with tau accumulation. These findings extend previous observations in cognitively normal aging, demonstrating that entorhinal tau continues to be closely associated with hippocampal hyperactivity and memory performance in MCI and mild dementia due to AD. Furthermore, data suggest that this association is strongest in medial temporal lobe structures. In summary, our data provide novel insights into the relationship of tau accumulation to neural activation and memory in AD.

Task-dependent effects of intracranial hippocampal stimulation on human memory and hippocampal theta power

BackgroundDespite its potential to revolutionize the treatment of memory dysfunction, the efficacy of direct electrical hippocampal stimulation for memory performance has not yet been well characterized. One of the main challenges to cross-study comparison in this area of research is the diversity of the cognitive tasks used to measure memory performance. ObjectiveWe hypothesized that the tasks that differentially engage the hippocampus may be differentially influenced by hippocampal stimulation and the behavioral effects would be related to the underlying hippocampal activity. MethodsTo investigate this issue, we recorded intracranial EEG from and directly applied stimulation to the hippocampus of 10 epilepsy patients while they performed two different verbal memory tasks – a word pair associative memory task and a single item memory task. ResultsHippocampal stimulation modulated memory performance in a task-dependent manner, improving associative memory performance, while impairing item memory performance. In addition, subjects with poorer baseline cognitive function improved much more with stimulation. iEEG recordings from the hippocampus during non-stimulation encoding blocks revealed that the associative memory task elicited stronger theta oscillations than did item memory and that stronger theta power was related to memory performance. ConclusionsWe show here for the first time that stimulation-induced associative memory enhancement was linked to increased theta power during retrieval. These results suggest that hippocampal stimulation enhances associative memory but not item memory because it engages more hippocampal theta activity and that, in general, increasing hippocampal theta may provide a neural mechanism for successful memory enhancement.

Effects of pointing compared with naming and observing during encoding on item and source memory in young and older adults

ABSTRACTResearch showed that source memory functioning declines with ageing. Evidence suggests that encoding visual stimuli with manual pointing in addition to visual observation can have a positive effect on spatial memory compared with visual observation only. The present study investigated whether pointing at picture locations during encoding would lead to better spatial source memory than naming (Experiment 1) and visual observation only (Experiment 2) in young and older adults. Experiment 3 investigated whether response modality during the test phase would influence spatial source memory performance. Experiments 1 and 2 supported the hypothesis that pointing during encoding led to better source memory for picture locations than naming or observation only. Young adults outperformed older adults on the source memory but not the item memory task in both Experiments 1 and 2. In Experiments 1 and 2, participants manually responded in the test phase. Experiment 3 showed that if participants had to verbally respond in the test phase, the positive effect of pointing compared with naming during encoding disappeared. The results suggest that pointing at picture locations during encoding can enhance spatial source memory in both young and older adults, but only if the response modality is congruent in the test phase.

Genetic variation in the serotonin transporter gene influences ERP old/new effects during recognition memory

Recognition memory is defined as the ability to recognize a previously encountered stimulus and has been associated with spatially and temporally distinct event-related potentials (ERPs). Allelic variations of the serotonin transporter gene (SLC6A4) have recently been shown to impact memory performance. Common variants of the serotonin transporter-linked polymorphic region (5HTTLPR) of the SLC6A4 gene result in long (l) and short (s) allelic variants with carriers of the s allele having lowered transcriptional efficiency. Thus, the current study examines the effects polymorphisms of the SLC6A4 gene have on performance and ERP amplitudes commonly associated with recognition memory. Electroencephalogram (EEG), genetic, and behavioral data were collected from sixty participants as they performed an item and source memory recognition task. In both tasks, participants studied and encoded 200 words, which were then mixed with 200 new words during retrieval. Participants were monitored with EEG during the retrieval portion of each memory task. EEG electrodes were grouped into four ROIs, left anterior superior, right anterior superior, left posterior superior, and right posterior superior. ERP mean amplitudes during hits in the item and source memory task were compared to correctly recognizing new items (correct rejections). Results show that s-carriers have decreased mean hit amplitudes in both the right anterior superior ROI 1000–1500ms post stimulus during the source memory task and the left anterior superior ROI 300–500ms post stimulus during the item memory task. These results suggest that individual differences due to genetic variation of the serotonin transporter gene influences recognition memory.

Central Adiposity Is Negatively Associated with Hippocampal-Dependent Relational Memory among Overweight and Obese Children

To assess associations between adiposity and hippocampal-dependent and hippocampal-independent memory forms among prepubertal children. Prepubertal children (age 7-9 years; n = 126), classified as non-overweight (<85th percentile body mass index [BMI]-for-age [n = 73]) or overweight/obese (≥85th percentile BMI-for-age [n = 53]), completed relational (hippocampal-dependent) and item (hippocampal-independent) memory tasks. Performance was assessed with both direct (behavioral accuracy) and indirect (preferential disproportionate viewing [PDV]) measures. Adiposity (ie, percent whole-body fat mass, subcutaneous abdominal adipose tissue, visceral adipose tissue, and total abdominal adipose tissue) was assessed by dual-energy X-ray absorptiometry. Backward regression identified significant (P < .05) predictive models of memory performance. Covariates included age, sex, pubertal timing, socioeconomic status (SES), IQ, oxygen consumption, and BMI z-score. Among overweight/obese children, total abdominal adipose tissue was a significant negative predictor of relational memory behavioral accuracy, and pubertal timing together with SES jointly predicted the PDV measure of relational memory. In contrast, among non-overweight children, male sex predicted item memory behavioral accuracy, and a model consisting of SES and BMI z-score jointly predicted the PDV measure of relational memory. Regional, but not whole-body, fat deposition was selectively and negatively associated with hippocampal-dependent relational memory among overweight/obese prepubertal children.

Dissociation between source and item memory in Parkinson’s disease

Episodic memory includes information about item memory and source memory. Many researches support the hypothesis that these two memory systems are implemented by different brain structures. The aim of this study was to investigate the characteristics of item memory and source memory processing in patients with Parkinson's disease (PD), and to further verify the hypothesis of dual-process model of source and item memory. We established a neuropsychological battery to measure the performance of item memory and source memory. Totally 35 PD individuals and 35 matched healthy controls (HC) were administrated with the battery. Item memory task consists of the learning and recognition of high-frequency national Chinese characters; source memory task consists of the learning and recognition of three modes (character, picture, and image) of objects. Compared with the controls, the idiopathic PD patients have been impaired source memory (PD vs. HC: 0.65 ± 0.06 vs. 0.72 ± 0.09, P = 0.001), but not impaired in item memory (PD vs. HC: 0.65 ± 0.07 vs. 0.67 ± 0.08, P = 0.240). The present experiment provides evidence for dissociation between item and source memory in PD patients, thereby strengthening the claim that the item or source memory rely on different brain structures. PD patients show poor source memory, in which dopamine plays a critical role.

Neural Correlates of Confidence during Item Recognition and Source Memory Retrieval: Evidence for Both Dual-process and Strength Memory Theories

Although the medial-temporal lobes (MTL), PFC, and parietal cortex are considered primary nodes in the episodic memory network, there is much debate regarding the contributions of MTL, PFC, and parietal subregions to recollection versus familiarity (dual-process theory) and the feasibility of accounts on the basis of a single memory strength process (strength theory). To investigate these issues, the current fMRI study measured activity during retrieval of memories that differed quantitatively in terms of strength (high vs. low-confidence trials) and qualitatively in terms of recollection versus familiarity (source vs. item memory tasks). Support for each theory varied depending on which node of the episodic memory network was considered. Results from MTL best fit a dual-process account, as a dissociation was found between a right hippocampal region showing high-confidence activity during the source memory task and bilateral rhinal regions showing high-confidence activity during the item memory task. Within PFC, several left-lateralized regions showed greater activity for source than item memory, consistent with recollective orienting, whereas a right-lateralized ventrolateral area showed low-confidence activity in both tasks, consistent with monitoring processes. Parietal findings were generally consistent with strength theory, with dorsal areas showing low-confidence activity and ventral areas showing high-confidence activity in both tasks. This dissociation fits with an attentional account of parietal functions during episodic retrieval. The results suggest that both dual-process and strength theories are partly correct, highlighting the need for an integrated model that links to more general cognitive theories to account for observed neural activity during episodic memory retrieval.

A neuroimaging investigation of the association between aerobic fitness, hippocampal volume, and memory performance in preadolescent children

Because children are becoming overweight, unhealthy, and unfit, understanding the neurocognitive benefits of an active lifestyle in childhood has important public health and educational implications. Animal research has indicated that aerobic exercise is related to increased cell proliferation and survival in the hippocampus as well as enhanced hippocampal-dependent learning and memory. Recent evidence extends this relationship to elderly humans by suggesting that high aerobic fitness levels in older adults are associated with increased hippocampal volume and superior memory performance. The present study aimed to further extend the link between fitness, hippocampal volume, and memory to a sample of preadolescent children. To this end, magnetic resonance imaging was employed to investigate whether higher- and lower-fit 9- and 10-year-old children showed differences in hippocampal volume and if the differences were related to performance on an item and relational memory task. Relational but not item memory is primarily supported by the hippocampus. Consistent with predictions, higher-fit children showed greater bilateral hippocampal volumes and superior relational memory task performance compared to lower-fit children. Hippocampal volume was also positively associated with performance on the relational but not the item memory task. Furthermore, bilateral hippocampal volume was found to mediate the relationship between fitness level (VO2 max) and relational memory. No relationship between aerobic fitness, nucleus accumbens volume, and memory was reported, which strengthens the hypothesized specific effect of fitness on the hippocampus. The findings are the first to indicate that aerobic fitness may relate to the structure and function of the preadolescent human brain.

HIV-Associated Episodic Memory Impairment: Evidence of a Possible Differential Deficit in Source Memory for Complex Visual Stimuli

HIV-Associated Episodic Memory Impairment: Evidence of a Possible Differential Deficit in Source Memory for Complex Visual Stimuli

Evidence for Modality-Independent Order Coding in Working Memory

The aim of the present study was to investigate the representation of serial order in working memory, more specifically whether serial order is coded by means of a modality-dependent or a modality-independent order code. This was investigated by means of a series of four experiments based on a dual-task methodology in which one short-term memory task was embedded between the presentation and recall of another short-term memory task. Two aspects were varied in these memory tasks--namely, the modality of the stimulus materials (verbal or visuo-spatial) and the presence of an order component in the task (an order or an item memory task). The results of this study showed impaired primary-task recognition performance when both the primary and the embedded task included an order component, irrespective of the modality of the stimulus materials. If one or both of the tasks did not contain an order component, less interference was found. The results of this study support the existence of a modality-independent order code.

Impairment of source memory in patients with obsessive–compulsive disorder: Equivalent current dipole analysis

We examined memory performance and cortical source localization of old/new effects in a source memory task in obsessive–compulsive disorder (OCD) patients by employing an equivalent current dipole (ECD) model using EEG and a realistic head model. Event-related potentials (ERPs) were recorded while 14 OCD patients and 14 age-, sex-, handedness-, and educational level-matched healthy control subjects performed recognition tasks for spoken words (items) or for the voice of the speaker of spoken words (sources). In the item memory task, both groups showed ERP old/new effects at 300–700 ms. In the source memory task, the controls showed ERP old/new effects at 400–700 ms, whereas the OCD patients did not. Compared with the controls, the OCD patients showed significantly lower source accuracy and prolonged reaction times to the old words with accurate voice judgments. There were no differences between the OCD and control groups with regard to the locations of the ERP generators elicited by source correct and correct rejection conditions. The OCD patients showed significantly altered hemispheric asymmetry of ECD power in the frontal lobe during source memory retrieval, compared with the controls. These results indicate that OCD patients have preserved item memory about content, but impaired source memory about context.

Source and Item Memory for Odors and Objects in Children and Young Adults

Recall and recognition memory for odors are poorer in children than in adolescents. In addition, children perform worse than young adults on source memory tasks using visual and auditory stimuli. However, source memory for odor stimuli has not been examined in children. This study investigated source and item memory for odors and objects in children (7–10 years old) and young adults (18–24 years old). During the study phase, 1 male and 1 female experimenter (sources) randomly presented either 16 odors or 16 objects to the participant. Presentation alternated between sources so that each source presented 8 stimuli. Once the 16 stimuli were presented, the sources exited and a third experimenter began the test phase. To assess item recognition memory, a stimulus from the study phase and a novel stimulus were presented to the participant who was asked to choose the stimulus presented during the study phase. Source memory was assessed with the 8 stimuli from the study phase not used in the item memory task. The experimenter presented a stimulus and asked whether the male or female experimenter had presented the stimulus during the study phase. Results indicate that difference scores between item and source memory for odors were significantly larger for children than for young adults, indicating poorer source memory for children than adults. Difference scores for objects did not distinguish between groups. It has been suggested that the frontal lobes play a critical role in source memory and odor memory—a brain region that continues to develop into adolescence. Poor performance among children on the source memory task for odors may be due in part to immaturity of the frontal lobes.

Language Influences on Verbal Short-Term Memory Performance in Down Syndrome

Down syndrome is associated with severe deficits in language and verbal shortterm memory, but the causal relationship between these deficits is unclear. The current study therefore investigated the influence of language abilities on verbal short-term memory performance in Down syndrome. Twenty-one individuals with Down syndrome and 29 younger typically developing children were tested on memory for words and nonwords using 2 immediate recognition tasks: an order memory task that was a relatively pure measure of verbal short-term memory and an item memory task that was more sensitive to language ability. Despite having superior vocabulary knowledge to the typically developing children, individuals with Down syndrome were impaired on both order and item tasks. This impairment was particularly marked on the item task, where individuals with Down syndrome showed an atypically large lexicality effect. These results are interpreted in terms of an underlying verbal short-term memory deficit in Down syndrome that is compounded by poor phonological discrimination abilities.

Remembering the color of objects: an ERP investigation of source memory.

Subjects studied pictures of common objects outlined in either red or green and were asked to memorize the objects and their associated colors. Event-related potentials (ERPs) were recorded during subsequent inclusion (i.e. item) and exclusion (i.e. source) memory tasks. The main goal of the experiment was to determine if brain signatures for familiarity and recollection, two behavioral processes thought to account for episodic memory performance, would be observed in the pattern of ERP results. For correctly recognized items, early, posterior old/new effects were recorded (approximately 300--600 ms) that did not differ in magnitude or scalp distribution between item and source memory tasks. A subsequent long-duration occipitally focused negativity (approximately 800 ms peak) was evident in the source but not the item memory task. The ERPs associated with 'source errors' in the source memory task also showed robust early old/new effects. However, 'source error' ERPs lacked frontal scalp activity compared to those associated with correct source attribution. The data suggest that a recollective response may require frontal involvement whereas a decision based on familiarity may not.

Order information in working memory: fMRI evidence for parietal and prefrontal mechanisms.

Working memory is thought to include a mechanism that allows for the coding of order information. One question of interest is how order information is coded, and how that code is neurally implemented. Here we report both behavioral and fMRI findings from an experiment involved comparing two tasks, an item-memory task and an order-memory task. In each case, five letters were presented for storage, followed after a brief interval by a set of probe letters. In the case of the item-memory task, the two letters were identical, and the subject responded to the question, "Was this letter one of the items you saw?". In the case of the order-memory task, the letters were different, and subjects responded to the question, "Are these two letters in the order in which you saw them?". Behaviorally, items that were further apart in the sequence that elicited faster reaction times and higher accuracy in the Order task. Areas that were significantly more activated in the Order condition included the parietal and prefrontal cortex. Parietal activations overlapped those involved in number processing, leading to the suggestion that the underlying representation of order and numbers may share a common process, coding for magnitude.

Equivalent spatial location memory deficits in rats with medial septum or hippocampal formation lesions and patients with dementia of the Alzheimer's type

College students, healthy elderly subjects, patients diagnosed with mild or moderate dementia of the Alzheimer's type, as well as rats with small or large lesions of the medial septum (MS), dorsal hippocampal formation (DHF) or nucleus basalis magnocellularis (NBM) were tested on an item memory task for a five- or six-item list of varying spatial locations. Equivalent patterns of item memory deficits as a function of serial order position were observed in rats with small or large MS or DHF lesions and patients with mild or moderate dementia of the Alzheimer's type. No deficits were found for NBM-lesioned rats. The results provide support for the possibility that rats with MS and DHF lesions mimic the mnemonic symptomatology of patients with Alzheimer's disease.