Explicit Memory Tasks Research Articles

Effect of Perceptions of Future Time on Implicit and Explicit Memory in Older Adults

ABSTRACT Objectives We examine age-related differences in implicit and explicit memory tasks, and test the impact of future time perspectives on priming and cued recall. Methods We induced time perspective in young (limited-time perspective) and older (extended-time perspective) adults. Implicit and explicit memory tasks were performed by younger and older adults. Results Results showed an age-related effect on priming and cued recall, confirming that implicit and explicit memory are impaired in aging. Nevertheless, manipulation of future time perspective eliminated age differences in priming and cued recall. Discussion These findings support the view that it is not age per se that determines memory performance but rather the perception of the time left to us. Socio-emotional selectivity theory thus seems to be a serious candidate to explain age-related differences in implicit and explicit memory.

Comparative Functional Connectivity of Core Brain Regions between Implicit and Explicit Memory Tasks Underlying Negative Emotion in General Anxiety Disorder.

ObjectiveTo investigate not only differential patterns of functional connectivity of core brain regions between implicit and explicit verbal memory tasks underlying negatively evoked emotional condition, but also correlations of functional connectivity (FC) strength with clinical symptom severity in patients with generalized anxiety disorder (GAD).MethodsThirteen patients with GAD and 13 healthy controls underwent functional magnetic resonance imaging for memory tasks with negative emotion words.ResultsClinical symptom and its severities of GAD were potentially associated with abnormalities of task-based FC with core brain regions and distinct FC patterns between implicit vs. explicit memory processing in GAD were potentially well discriminated. Outstanding FC in implicit memory task includes positive connections of precentral gyus (PrG) to inferior frontal gyrus and inferior parietal gyrus (IPG), respectively, in encoding period; a positive connection of amygdala (Amg) to globus pallidus as well as a negative connection of Amg to cerebellum in retrieval period. Meanwhile, distinct FC in explicit memory included a positive connection of PrG to inferior temporal gyrus (ITG) in encoding period; a positive connection of the anterior cingulate gyrus to superior frontal gyrus in retrieval period. Especially, there were positive correlation between GAD-7 scores and FC of PrG-IPG (r2 = 0.324, p = 0.042) in implicit memory encoding, and FC of PrG-ITG (r2 = 0.378, p = 0.025) in explicit memory encoding.ConclusionThis study clarified differential patterns of brain activation and relevant FC between implicit and explicit verbal memory tasks underlying negative emotional feelings in GAD. These findings will be helpful for an understanding of distinct brain functional mechanisms associated with clinical symptom severities in GAD.

The influence of sociophonetic knowledge on lexical encoding across dialects

The goal of this study was to determine if the strength of lexical encoding differed between regional dialects as a function of the explicit social knowledge listeners held about the dialects or talkers. Participants heard lexical items produced in the Midland, Northern, and Southern dialects of American English in an explicit lexical recognition memory task. Some participants were told the regional backgrounds of the talkers while others were not. It was predicted that encoding would be most robust for tokens produced in the ideologically standard Midland dialect and would be more robust for the socially stereotyped Southern dialect compared with the non-stereotyped Northern dialect. Being told regional information about the talkers was predicted to increase the robustness of encoding. Analysis of response times provided some evidence of a standard dialect benefit across listeners from the three regions, though this effect varied depending on the vowel contained in the stimulus item. Interestingly, being given regional information about the talkers did not increase the robustness with which tokens were encoded; for some listeners, it hindered performance. These results indicate that social knowledge about linguistic varieties can be highly integrated with speech processing, but that it is not facilitative in all situations.

Implicit and Explicit Memory in Youths with High-Functioning Autism Spectrum Disorder: A Case-Control Study

Individuals with autism spectrum disorder (ASD) usually manifest heterogeneous impairments in their higher cognitive functions, including their implicit memory (IM) and explicit memory (EM). However, the findings on IM and EM in youths with ASD remain debated. The aim of this study was to clarify such conflicting results by examining IM and EM using two comparable versions of the Serial Reaction Time Task (SRTT) in the same group of children and adolescents with ASD. Twenty-five youths with high-functioning ASD and 29 age-matched and IQ-matched typically developing youths undertook both tasks. The ability to implicitly learn the temporal sequence of events across the blocks in the SRTT was intact in the youths with ASD. When they were tested for EM, the participants with ASD did not experience a significant reduction in their reaction times during the blocks with the previously learned sequence, suggesting an impairment in EM. Moreover, the participants with ASD were less accurate and made more omissions than the controls in the EM task. The implications of these findings for the establishment of tailored educational programs for children with high-functioning ASD are discussed.

Functional connectivity abnormalities of the long-axis hippocampal subregions in schizophrenia during episodic memory

Past evidence suggests that hippocampal subregions, namely the anterior and posterior parts, may be engaged in distinct networks underlying the memory functions which may be altered in patients with schizophrenia. However, of the very few studies that have investigated the hippocampal longitudinal axis subdivisions functional connectivity in patients with schizophrenia, the majority was based on resting-state data, and yet, none aimed to examine these during an episodic memory task. A total of 41 patients with schizophrenia and 45 healthy controls were recruited for a magnetic resonance imaging protocol in which they performed an explicit memory task. Seed-based functional connectivity analysis was employed to assess connectivity abnormalities between hippocampal subregions and voxel-wise connectivity targets in patients with schizophrenia. We observed a significantly reduced connectivity between the posterior hippocampus and regions from the default mode network, but increased connectivity with the primary visual cortex, in patients with schizophrenia compared to healthy subjects. Increased connectivity between the anterior hippocampus and anterior temporal regions also characterized patients with schizophrenia. In the current study, we provided evidence and support for studying hippocampal subdivisions along the longitudinal axis in schizophrenia. Our results suggest that the abnormalities in hippocampal subregions functional connectivity reflect deficits in episodic memory that may be implicated in the pathophysiology of schizophrenia.

Examining three-way binding as a constraint on statistical learning.

Models of statistical learning do not place constraints on the complexity of the memory structure that is formed during statistical learning, while empirical studies using the statistical learning task have only examined the formation of simple memory structures (e.g., two-way binding). On the contrary, the memory literature, using explicit memory tasks, has shown that people are able to form memory structures of different complexities and that more complex memory structures (e.g., three-way binding) are usually more difficult to form. We examined whether complex memory structures such as three-way bindings can be implicitly formed through statistical learning by utilizing manipulations that have been used in the paired-associate learning paradigm (e.g., AB/ABr condition). Through three experiments, we show that while simple two-way binding structures can be formed implicitly, three-way bindings can only be formed with explicit instructions. The results indicate that explicit attention may be a necessary component in forming three-way memory structures and suggest that existing models should place constraints on the representational structures that can be formed. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The resiliency of image memorability: A predictor of memory separate from attention and priming

Recent work has demonstrated there is a power within images to impact our later memories—an intrinsic stimulus memorability that influences memory behavior consistently across observers. This memorability is computed as explicitly reported memory performance on each image, and is significantly correlated from observer to observer. Interestingly, neuroimaging work has found that memorable versus forgettable images show distinct, early patterns within the brain even when participants are not performing an explicit memory task. Thus, a key question is whether memorability effects reflect a more automatic, bottom-up process, or are the result of top-down attentional processes. Further, how do bottom-up and top-down processes interact with stimulus memorability to influence ultimate memory performance? The current study explores these questions through the lens of four classical psychological phenomena shown to influence memory. First, a directed forgetting task shows that cognitive control is unable to override the effects of stimulus memorability. Second, an experiment manipulating depth of processing reveals a performance boost for memorable images regardless of the depth at which they are encoded. Third, results from a visual search experiment show that memorable images do not trigger automatic attentional capture, or pop-out. Finally, results from a repetition priming task demonstrate that memorability and priming are independent phenomena. In sum, memorability is an isolable phenomenon, occurring automatically, and resilient to top-down influence.

Orexin-1 receptor blockade differentially affects spatial and visual discrimination memory facilitation by intracranial self-stimulation.

Intracranial self-stimulation (ICSS) of the medial forebrain bundle is an effective treatment to facilitate memory. Performance in both explicit and implicit memory tasks has been improved by ICSS, and this treatment has even been capable of recovering loss of memory function due to lesions or old age. Several neurochemical systems have been studied in regard to their role in ICSS effects on memory, however the possible involvement of the orexinergic system in this facilitation has yet to be explored. The present study aims to examine the relationship between the OX1R and the facilitative effects of ICSS on two different types of memory tasks, both carried out in the Morris Water Maze: spatial and visual discrimination. Results show that the OX1R blockade, by intraventricular administration of SB-334867, partially negates the facilitating effect of ICSS on spatial memory, whereas it hinders ICSS facilitation of the discrimination task. However, ICSS treatment was capable of compensating for the severe detrimental effects of OX1R blockade on both memory paradigms. These results suggest different levels of involvement of the orexinergic system in the facilitation of memory by ICSS, depending on the memory task.

Memory for future actions: the effect of prospective memory on an explicit and implicit memory task.

In the field of retrospective memory, an explicit and implicit memory are known to exist. This study analyses the effect of the prospective memory on a recognition task and a lexical decision task. In experiment 1 (n = 78, of which 39 belonged to the experimental group and 39 belonged to the control group), a recognition task was followed by an intentional task, as well as an incidental free recall task. In experiment 2 (n = 74, of which 37 belonged to the experimental group and 37 belonged to the control group), repetition priming was studied during a lexical decision task, followed by an intentional task. The data were analysed using a mixed ANOVA. Experiment 1 showed active monitoring of the prospective memory task accompanied by a recollective search process during the recognition task. The group which carried out the prospective task also showed better scores in the incidental free recall task. Experiment 2 showed active monitoring and repetition priming during the lexical decision task. While the prospective memory affects the performance in both concurrent tasks, it does not affect the recollective search process or repetition priming.

Statistical Language Learning and Vagus Nerve Stimulation: A Pilot Study

Applying transcutaneous stimulation to the auricular branch of the vagus nerve (tVNS) has been shown to enhance associative learning in humans. The main goal of the project is to investigate the effect tVNS has on procedural learning, specifically implicit statistical language learning. The aim of the experiment reported in this paper was to determine which statistical language learning paradigms would be appropriate to use with tVNS. Since we would be looking at within-subject changes between two sessions (one session with, one session without stimulation), we tested the test-retest reliability of two statistical learning paradigms. We also tested the correlation between a explicit phonological memory task and the implicit statistical learning tasks to determine whether phonological memory was involved in the statistical learning tasks. Our results showed a high test-retest reliability for the word segmentation and adjacent dependencies statistical learning task. However, the second statistical learning task dealing with non-adjacent dependencies had low test-retest reliability, meaning it would not be appropriate for future studies incorporating tVNS. There was a high correlation between the phonological memory task and both statistical learning taks, indicating implicit statistical learning may recruit phonological memory.

Explicit and Implicit Memory Loss in Aging

How our memory is affected as we age has been given considerable attention over recent decades as we strive to understand the cognitive processes involved. Memory types have been identified as either explicit (declarative - related to episodes or semantics) or implicit (non-declarative – related to procedures, habits, or earlier priming). Studies have identified likely age-related decline in explicit but not implicit memory though there are opposing results suggested from other studies. It is thought cognitive reserve capacities might explain any non-decline as aging individuals use alternative or additional pathways to ‘remember’. This theory might be supported indirectly if older members remember material accurately but take longer to supply answers. In our current study we re-examined whether age-related differences in accuracy and speed of access in memory are present in both implicit and explicit memory processes and we increased the number of experimental age groups (from 2 to 3) - most previous studies have compared just two groups (young, and old). With three groups (young, middle-old, and older aged groups) we can identify trends across the age range towards deterioration or preservation of memory. We examined sixty-six participants (49 females; 17 males) aged 18 to 86 years (M = 50.27, SD = 21.06) from South-Eastern Queensland and divided these into younger (18 to 46 years of age), middle old (50 to 64) and older aged (65+) cohorts. Participants were administered tasks assessing implicit and explicit memory using computer presentations. Consistent with most prior research, no age differences were identified on accuracy in the implicit memory tasks (verbal and non-verbal, including priming), suggesting that memory for implicit material remains preserved. However, on the explicit memory tasks, older adults performed less accurately than the younger adults, indicative of decline in explicit memory as we age. The finding of a decline in explicit memory but no significant decline in implicit memory confirms most earlier research and is consistent with a view of modular decline rather than overall decline in memory with increasing age. In addition, differences found in speed of response in otherwise accurate implicit memory with older respondents significantly slower, suggests possible support for the cognitive reserve hypothesis.

Sentence Context and Word-Picture Cued-Recall Paired-Associate Learning Procedure Boosts Recall in Normal and Mild Alzheimer's Disease Patients.

Introduction The aim of this study was to employ the word-picture paradigm to examine the effectiveness of combined pictorial illustrations and sentences as strong contextual cues. The experiment details the performance of word recall in healthy older adults (HOA) and mild Alzheimer's disease (AD). The researchers enhanced the words' recall with word-picture condition and when the pair was associated with a sentence contextualizing the two items. Method The sample was composed of 18 HOA and 18 people with mild AD. Participants memorized 15 pairs of words under word-word and word-picture conditions, with and without a sentence context. In the paired-associate test, the first item of the pair was read aloud by participants and used to elicit retrieval of the associated item. Results The findings suggest that both HOA and mild-AD pictures improved item recall compared to word condition such as sentences which further enabled item recall. Additionally, the HOA group performs better than the mild-AD group in all conditions. Conclusions Word-picture and sentence context strengthen the encoding in the explicit memory task, both in HOA and mild AD. These results open a potential window to improve the memory for verbalized instructions and restore sequential abilities in everyday life, such as brushing one's teeth, fastening one's pants, or drying one's hands.

Comparative functional neuroanatomy between implicit and explicit memory tasks under negative emotional condition in schizophrenia

PurposeTo evaluate the brain activation patterns in response to negative emotion during implicit and explicit memory in patients with schizophrenia. Material and methodsFourteen patients with schizophrenia and 14 healthy controls were included in this study. The 3.0T fMRI was obtained while the subjects performed the implicit and explicit retrievals with unpleasant words. ResultsThe different predominant brain activation areas were observed during the implicit retrieval and explicit with unpleasant words. ConclusionThe differential neural mechanisms between implicit and explicit memory tasks associated with negative emotional processing in schizophrenia.

Something always sticks? how emotional language modulates neural processes involved in face encoding and recognition memory

AbstractLanguage can serve to constrain cognitive and emotional representations. Here, we investigate to what extent linguistic emotional information alters processing of faces with neutral expressions. Previous studies have shown that cortical processing of emotional faces differs from that of neutral faces. Electroencephalography (EEG) has revealed emotion effects for early and late event-related potentials (ERPs) such as the N1, the Early Posterior Negativity (EPN) and the Late Positive Potential (LPP). In order to study the effect of language information on face processing, 30 negative and 30 neutral descriptive phrases were presented, each followed by a neutral expression face. Participants were instructed to remember the association. We analyzed the immediate effect of information type on face processing during encoding as well as delayed effects during subsequent recognition. During encoding, faces following negative language information elicited a larger left frontal positivity between 500–700 ms after stimulus onset. During recognition, a left centro-parietal LPP was likewise increased for faces previously associated with a negative description. In addition, the parietal old/new effect was significantly increased for faces with negative information compared to new ones, while no significant effect was observed for faces with neutral information. No information effects on early perceptual ERPs (N1, EPN) were found. Reaction times (RTs) for source memory decisions (negative versus neutral) were significantly shorter for faces with negative versus neutral information. In sum, ERP results indicate that emotional significance can be linguistically induced in faces on a cortical level and, at least in an explicit memory task, this information modulates later stages of face processing and memory. Implications for cognitive effects of public media design are discussed.

Neuroanatomical assessment of the impact of negative emotion on explicit memory in patients with obsessive-compulsive disorder.

The aim of this study was to identify the brain activation patterns associated with emotionally neutral or unpleasant words during explicit memory tasks in patients with obsessive-compulsive disorder (OCD) using a functional MRI. Sixteen patients with OCD (mean age=31.4±10.1 years) and 16 healthy controls (mean age=32.6±5.8 years) who had no history of neurological or psychiatric illness underwent functional MRI examinations on a 3-T Siemens MR Scanner. The stimulation paradigm consisted of five times rest-condition, two times encoding of two-syllable words, and two times explicit retrieval of the previously learned words. Six different words were presented for 3 s each in the encoding and retrieval tasks. In the retrieval task, the same words as those used at the encoding task were presented randomly. Brain activation maps were quantified and analyzed using SPM8 and MRIcron software. During the explicit retrieval tasks with emotionally neutral words, the predominant activation areas observed in patients with OCD included the angular gyrus and the supramarginal gyrus, whereas healthy controls showed significantly higher activity in the postcentral gyrus (P<0.005). During the explicit retrieval tasks with unpleasant words, patients with OCD showed significantly higher activity, compared with healthy controls, in the cerebellum, posterior cingulate gyrus, middle occipital gyrus, middle temporal gyrus, and inferior frontal gyrus (P<0.005); however, no predominant activation areas in healthy controls over patients with OCD were observed. This study showed differential brain activation patterns in response to emotionally neutral and unpleasant words in patients with OCD. This finding will be useful in assessing the neural mechanisms associated with emotional effect on the impairment of memory retrieval in OCD.

Memory Self-Efficacy and Memory Performance in Older Adults

Abstract. The present research examined the role persistence plays in mediating the positive impact of memory self-efficacy (MSE, i.e., one’s confidence in one’s own memory abilities) on older adults’ memory performance. In three studies, 81 to 264 older adults completed an MSE scale and carried out an explicit episodic memory task, during which we recorded their study time as an indicator of task persistence. We found that higher MSE was indirectly related to better memory performance through greater persistence during encoding, as measured by longer study time. Indirect effects were of medium size, with point estimates ranging from 0.64 to 0.85. This mediation effect was independent of factors that could be confounded with study time: chronological age, memory span, prior level of memory performance, episodic memory ability, and use of learning strategies (encoding strategies and self-testing). When confronted with difficult memory tasks, older adults who lack confidence in their memory abilities cease their efforts prematurely, which contributes to a decrease in their performance. Encouraging older adults to persist in the face of difficulties during encoding and retrieval may help alleviate the negative impact of low MSE on memory performance and allow researchers and clinicians to more accurately estimate older adults’ true memory abilities.

Caffeine Enhances Memory Performance in Young Adults during Their Non-optimal Time of Day.

Many college students struggle to perform well on exams in the early morning. Although students drink caffeinated beverages to feel more awake, it is unclear whether these actually improve performance. After consuming coffee (caffeinated or decaffeinated), college-age adults completed implicit and explicit memory tasks in the early morning and late afternoon (Experiment 1). During the morning, participants ingesting caffeine demonstrated a striking improvement in explicit memory, but not implicit memory. Caffeine did not alter memory performance in the afternoon. In Experiment 2, participants engaged in cardiovascular exercise in order to examine whether increases in physiological arousal similarly improved memory. Despite clear increases in physiological arousal, exercise did not improve memory performance compared to a stretching control condition. These results suggest that caffeine has a specific benefit for memory during students’ non-optimal time of day – early morning. These findings have real-world implications for students taking morning exams.

The role of chronic physical exercise and selective attention at encoding on implicit and explicit memory

ABSTRACTDespite the evidence revealing benefits of chronic cardiovascular exercise on executive functions, little research has been conducted on long-term memory. We aimed to investigate the effect of physical exercise on implicit and explicit memory when attention was modulated at encoding in two groups of active and sedentary participants. With this purpose, attention was manipulated in a similar way in the implicit and explicit memory tasks by presenting picture outlines of two familiar objects, one in blue and the other in green, and participants were asked to pay attention only to one of them. Implicit memory was assessed through conceptual priming and explicit memory through a free recall task followed by recognition. The results did not reveal significant differences between groups in conceptual priming or free recall. However, in recognition, while both groups had similar discrimination for attended stimuli, active participants showed lower discrimination between unattended and new stimuli. These results suggested that exercise may have effects on specific cognitive processes, that is, that active participants may suppress non-relevant information better than sedentary participants, making the discrimination between unattended and new items more difficult.

Slow wave and REM sleep deprivation effects on explicit and implicit memory during sleep.

It has been debated whether different stages in the human sleep cycle preferentially mediate the consolidation of explicit and implicit memories, or whether all of the stages in succession are necessary for optimal consolidation. Here we investigated whether the selective deprivation of slow wave sleep (SWS) or rapid eye movement (REM) sleep over an entire night would have a specific effect on consolidation in explicit and implicit memory tasks. Participants completed a set of explicit and implicit memory tasks at night, prior to sleep. They had 1 control night of undisturbed sleep and 2 experimental nights, during which either SWS or REM sleep was selectively deprived across the entire night (sleep conditions counterbalanced across participants). Polysomnography recordings quantified precisely the amount of SWS and REM sleep that occurred during each of the sleep conditions, and spindle counts were recorded. In the morning, participants completed the experimental tasks in the same sequence as the night before. SWS deprivation disrupted the consolidation of explicit memories for visuospatial information (ηp2 = .23), and both SWS (ηp2 = .53) and REM sleep (ηp2 = .52) deprivation adversely affected explicit verbal recall. Neither SWS nor REM sleep deprivation affected aspects of short-term or working memory, and did not affect measures of verbal implicit memory. Spindle counts did not correlate significantly with memory performance. These findings demonstrate the importance of measuring the sleep cycles throughout the entire night, and the contribution of both SWS and REM sleep to memory consolidation. (PsycINFO Database Record

Abnormalities in gray and white matter volumes associated with explicit memory dysfunction in patients with generalized anxiety disorder.

Background The neuroanatomical abnormalities associated with behavioral dysfunction on explicit memory in patients generalized anxiety disorder (GAD) have not yet been clearly identified. Purpose To investigate the regional gray matter (GM) and white matter (WM) volume alterations over the whole brain in patients with GAD, as well as the correlation between the brain structural abnormality and explicit memory dysfunction. Material and Methods Twenty patients with GAD and 20 healthy controls matched for age, sex, and education level underwent high-resolution T1-weighted magnetic resonance imaging (MRI). The participants performed the explicit memory tasks with the neutral and anxiety-inducing words. Results Patients with GAD showed significantly reduced GM volumes in the midbrain (MB), thalamus, hippocampus (Hip), insula, and superior temporal gyrus (STG); and reduced WM volumes in the MB, anterior limb of the internal capsule (ALIC), dorsolateral prefrontal cortex (DLPFC), and precentral gyrus (PrG). It is important to note that the GM volume of the Hip and the WM volume of the DLPFC were positively correlated with the recognition accuracy (%) in the explicit memory tasks with neutral and anxiety-inducing words, respectively. On the other hand, the WM volume of the PrG was negatively correlated with the reaction time in the same memory tasks. Conclusion This study demonstrated the regional volume changes on whole-brain GM and WM and the correlation between the brain structural alteration and explicit memory dysfunction in GAD patients. These findings would be helpful to understand the association between the brain structure abnormality and the functional deficit in the explicit memory in GAD.