Subsequent Free Recall Research Articles

On the Move: Correlation of Impaired Mobility with Spatial Navigation Ability in Persons with Multiple Sclerosis.

Spatial navigation ability is essential for independent living, and it relies on complex cognitive and motor processes that are vulnerable to decline in persons with multiple sclerosis (pwMS). The role of mobility in the physical act of navigation has been well documented; however, its association with cognitive processing that supports efficient navigation and recall of the environment is unknown. This study examined the relation between clinical mobility function and spatial navigation ability in pwMS. In a clinical sample of 43 individuals with relapsing-remitting MS (MPDDS = 2; age 25-67 years), we assessed spatial navigation ability in a virtual Morris water maze that allowed for active search by controlling a joystick while seated at a computer, and subsequent free recall of environment details. Individuals with worse mobility (measured by slower forward and backward walking) traveled less efficient virtual navigation routes to the goal location and recalled fewer accurate details of the environment. A stratified analysis by disability revealed moderate-strong correlations for those with a low level of disability, and effects were attenuated in individuals with a high level of disability. Given that the virtual navigation task was performed while seated, evidence of any correlation with mobility suggests differences in navigation ability that cannot be ascribed to general walking impairment, and instead suggests a role for mobility impairment to modify cognitive processing supporting navigation in pwMS.

Read carefully, because this is important! How value-driven strategies impact sentence memory.

Little is understood about how people strategically process and remember important but complex information, such as sentences. In the current study, we asked whether people can effectively prioritize memory for sentences as a function of their relative importance (operationalized as a reward point value) and whether they do so, in part, by changing their sentence processing strategies when value information is available in advance. We adapted the value-directed remembering paradigm (Castel, Psychol Learn Motiv 48:225-270, 2007) for sentences that varied in constraint and predictability. Each sentence was associated with a high or low value for subsequent free recall (whole sentence) and recognition (sentence-final words) tests. Value information appeared after or before each sentence as a between-subject manipulation. Regardless of condition, we observed that high-value sentences were recalled more often than low-value sentences, showing that people can strategically prioritize their encoding of sentences. However, memory patterns differed depending on when value information was available. Recall for high-value sentences that ended unexpectedly (and therefore violated one's predictions) was reduced in the Before compared to the After condition. Before condition participants also showed a greater tendency to false alarm to lures (words that were the predicted - but not obtained - ending) from strongly constraining sentences. These observations suggest that when people try to prioritize sentence-level information that they know is valuable, the reading strategies they employ may paradoxically lead to worse memory.

Learning new words via feedback-Association between feedback-locked ERPs and recall performance-An exploratory study.

Feedback learning is thought to involve the dopamine system and its projection sites in the basal ganglia and anterior cingulate cortex (ACC), regions associated with procedural learning. Under certain conditions, such as when feedback is delayed, feedback-locked activation is pronounced in the medial temporal lobe (MTL), which is associated with declarative learning. In event-related potential research, the feedback-related negativity (FRN) has been linked to immediate feedback processing, while the N170, possibly reflecting MTL activity, has been related to delayed feedback processing. In the current study, we performed an exploratory investigation on the relation between N170 and FRN amplitude and memory performance in a test for declarative memory (free recall), also exploring the role of feedback delay. To this end, we adapted a paradigm in which participants learned associations between non-objects and non-words with either immediate or delayed feedback, and added a subsequent free recall test. We indeed found that N170, but not FRN amplitudes, depended on later free recall performance, with smaller amplitudes for later remembered non-words. In an additional analysis with memory performance as dependent variable, the N170, but not the FRN amplitude predicted free recall, modulated by feedback timing and valence. This finding shows that the N170 reflects an important process during feedback processing, possibly related to expectations and their violation, but is distinct from the process reflected by the FRN.

Hotspot of human verbal memory encoding in the left anterior prefrontal cortex.

SummaryBackgroundTreating memory and cognitive deficits requires knowledge about anatomical sites and neural activities to be targeted with particular therapies. Emerging technologies for local brain stimulation offer attractive therapeutic options but need to be applied to target specific neural activities, at distinct times, and in specific brain regions that are critical for memory formation.MethodsThe areas that are critical for successful encoding of verbal memory as well as the underlying neural activities were determined directly in the human brain with intracranial electrophysiological recordings in epilepsy patients. We recorded a broad range of spectral activities across the cortex of 135 patients as they memorised word lists for subsequent free recall.FindingsThe greatest differences in the spectral power between encoding subsequently recalled and forgotten words were found in low theta frequency (3–5 Hz) activities of the left anterior prefrontal cortex. This subsequent memory effect was proportionally greater in the lower frequency bands and in the more anterior cortical regions. We found the peak of this memory signal in a distinct part of the prefrontal cortex at the junction between the Broca's area and the frontal pole. The memory effect in this confined area was significantly higher (Tukey–Kramer test, p<0.05) than in other anatomically distinct areas.InterpretationOur results suggest a focal hotspot of human verbal memory encoding located in the higher-order processing region of the prefrontal cortex, which presents a prospective target for modulating cognitive functions in the human patients. The memory effect provides an electrophysiological biomarker of low frequency neural activities, at distinct times of memory encoding, and in one hotspot location in the human brain.FundingOpen-access datasets were originally collected as part of a BRAIN Initiative project called Restoring Active Memory (RAM) funded by the Defence Advanced Research Project Agency (DARPA). CT, ML, MTK and this research were supported from the First Team grant of the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund.

The role of implicit motor simulation on action verb memory.

Observation is known to improve memory for action. Previous findings linked such an effect with an easier relation processing of action components following observation compared to mere sentence reading. However, action observation also elicits implicit motor simulation, that is a processing of one's movement through the observer own motor system. We aimed to assess whether encoding of implicit motor simulation can also explain why observation is better than reading for action memory. To prevent influence of item relation processing, two studies about isolated action verbs learning were designed. In Experiment 1, action verbs were encoded with short videos of point-light human movements or with written definitions. Subsequent free recall indicated better memory for the verbs within the video clip condition. Experiment 2 compared two encoding conditions based on point-light human movement videos. Half of the verbs were learned with their normal corresponding movement (biological kinematic). For the other half of the verbs, the velocity of point-light movements was modified to create abnormal nonbiological kinematic actions. We observed better free recall for the verbs learned with biological kinematics. Taken together, those results suggest that action observation is beneficial because it allows the encoding of motor-related information (implicit motor simulation). Semantic resonance between linguistic and motor representations of action could also contribute to memory improvement. Contrary to previous studies, our results cannot be explained by an improvement of items relation processing. However, it suggests that the basic level of action verb memory is sensorimotor perception, such as implicit motor simulation.

Independent dynamics of low, intermediate, and high frequency spectral intracranial EEG activities during human memory formation

A wide spectrum of brain rhythms are engaged throughout the human cortex in cognitive functions. How the rhythms of various frequency ranges are coordinated across the space of the human cortex and time of memory processing is inconclusive. They can either be coordinated together across the frequency spectrum at the same cortical site and time or induced independently in particular bands. We used a large dataset of human intracranial electroencephalography (iEEG) to parse the spatiotemporal dynamics of spectral activities induced during formation of verbal memories. Encoding of words for subsequent free recall activated low frequency theta, intermediate frequency alpha and beta, and high frequency gamma power in a mosaic pattern of discrete cortical sites. A majority of the cortical sites recorded activity in only one of these frequencies, except for the visual cortex where spectral power was induced across multiple bands. Each frequency band showed characteristic dynamics of the induced power specific to cortical area and hemisphere. The power of the low, intermediate, and high frequency activities propagated in independent sequences across the visual, temporal and prefrontal cortical areas throughout subsequent phases of memory encoding. Our results provide a holistic, simplified model of the spectral activities engaged in the formation of human memory, suggesting an anatomically and temporally distributed mosaic of coordinated brain rhythms.

Recall of Reverberant Speech in Quiet and Four-Talker Babble Noise.

Using behavioral evaluation of free recall performance, we investigated whether reverberation and/or noise affected memory performance in normal-hearing adults. Thirty-four participants performed a free-recall task in which they were instructed to repeat the initial word after each sentence and to remember the target words after each list of seven sentences, in a 2 (reverberation) × 2 (noise) factorial design. Pupil dilation responses (baseline and peak pupil dilation) were also recorded sentence-by-sentence while the participants were trying to remember the target words. In noise, speech was presented at an easily audible level using an individualized signal-to-noise ratio (95% speech intelligibility). As expected, recall performance was significantly lower in the noisy environment than in the quiet condition. Regardless of noise interference or reverberation, sentence- baseline values gradually increased with an increase in the number of words to be remembered for a subsequent free-recall task. Long reverberation time had no significant effect on memory retrieval of verbal stimuli or pupillary responses during encoding.

Visual Exploration at Higher Fixation Frequency Increases Subsequent Memory Recall.

Only a small proportion of what we see can later be recalled. Up to date it is unknown how far differences in visual exploration during encoding affect the strength of episodic memories. Here, we identified individual gaze characteristics by analyzing eye tracking data in a picture encoding task performed by 967 healthy subjects during fMRI. We found a positive correlation between fixation frequency during visual exploration and subsequent free recall performance. Brain imaging results showed a positive correlation of fixation frequency with activations in regions related to vision and memory, including the medial temporal lobe. To investigate if higher fixation frequency is causally linked to better memory, we experimentally manipulated visual exploration patterns in an independent population of 64 subjects. Doubling the number of fixations within a given exploration time increased subsequent free recall performance by 19%. Our findings provide evidence for a causal relationship between fixation frequency and episodic memory for visual information.

Neural fatigue influences memory encoding in the human hippocampus

Here we examine the variability underlying successful memory encoding. Successful encoding of successive study items may fatigue encoding resources, thus decreasing the ability to encode subsequent items (Tulving and Rosenbaum, 2006); alternatively, successful encoding may be persistent, leading to more successful encoding (Kahana, Aggarwal, and Phan, 2018). Analyzing intracranial electroencephalographic activity while subjects studied lists of words for subsequent free recall, we examined high-frequency activity (HFA) in hippocampus and dorsolateral prefrontal cortex (DLPFC), as HFA was greater for subsequently recalled than non-recalled items in these regions. We compared non-recalled items with good encoding history (i.e. one of the two preceding items was recalled) with non-recalled items with poor encoding history (i.e. neither prior item was recalled). In the hippocampus, good encoding history led to reduced HFA, whereas in the DLPFC, good encoding history led to enhanced HFA. Hippocampal findings appear consistent with the neural fatigue hypothesis, whereas the DLPFC results appear consistent with persistent encoding states.

Mnemoscape: Supporting Older Adults’ Event Memory Using Wearable Camera Photographs on an Immersive Interface

Background: Wearable camera photographs have been shown to be an effective memory aid in people with and without memory impairment. Most studies using wearable cameras as a memory aid have presented photographs on a computer monitor and used a written diary or no review as a comparison. In this pioneering study, we took a new and innovative approach to wearable camera photograph review that embeds the photographs within a virtual landscape. This approach may enhance these benefits by reinstating the original environmental context to increase participants’ sense of re-experiencing the event. Objective: We compare the traditional computer monitor presentation of wearable camera photographs and actively taken digital photographs with the presentation of wearable camera photographs in a new immersive interface that reinstates the spatiotemporal context. Methods: Healthy older adults wore wearable or took digital photographs during a staged event. The next day and 2 weeks later, they viewed wearable camera photographs on a computer monitor or in context on an immersive interface, or digital photographs. Results: Participants who viewed wearable camera photographs in either format recalled more details during photo viewing and subsequent free recall than participants who viewed digital photographs they had taken themselves. Conclusion: Wearable camera photographs are an effective support for event memory, regardless of whether they are presented in context in an experience-near format.

The BDNF Val66Met Polymorphism Has No Effect on Encoding-Related Hippocampal Response But Influences Recall in Remitted Patients With Bipolar Disorder.

Background: Cognitive impairments in bipolar disorder (BD) such as memory deficits are associated with poor functional outcomes and it has been suggested that the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism contributes to individual variability in memory function in BD. The current study investigated the relationship between the BDNF Val66Met polymorphism, neural activity during a picture-encoding task, and subsequent memory recall.Methods: A total of 70 patients with BD grouped according to genotype [ValVal or Met carriers (MetVal/MetMet)] underwent fMRI while performing a picture-encoding task. Memory for the encoded pictures was tested with a subsequent free recall memory task.Results: There was no difference between the ValVal homozygotes and Met carriers in the involvement of hypothesized memory encoding regions i.e. hippocampus and dorsal prefrontal cortex (dPFC). However, an exploratory whole-brain analysis showed greater encoding-related lateral occipital cortex activity in Met carriers. Behaviorally, Met carriers also showed better free recall of the encoded pictures.Conclusions: We found no effect of the BDNF genotype on encoding-related hippocampal and dPFC activity in BD, although Met carriers showed superior memory performance after the scan, which could be related to more efficient perceptual processing during encoding.

Stimulation of the Posterior Cingulate Cortex Impairs Episodic Memory Encoding.

Neuroimaging experiments implicate the posterior cingulate cortex (PCC) in episodic memory processing, making it a potential target for responsive neuromodulation strategies outside of the hippocampal network. However, causal evidence for the role that PCC plays in memory encoding is lacking. In human female and male participants (N = 17) undergoing seizure mapping, we investigated functional properties of the PCC using deep brain stimulation (DBS) and stereotactic electroencephalography. We used a verbal free recall paradigm in which the PCC was stimulated during presentation of half of the study lists, whereas no stimulation was applied during presentation of the remaining lists. We investigated whether stimulation affected memory and modulated hippocampal activity. Results revealed four main findings. First, stimulation during episodic memory encoding impaired subsequent free recall, predominantly for items presented early in the study lists. Second, PCC stimulation increased hippocampal gamma-band power. Third, stimulation-induced hippocampal gamma power predicted the magnitude of memory impairment. Fourth, functional connectivity between the hippocampus and PCC predicted the strength of the stimulation effect on memory. Our findings offer causal evidence implicating the PCC in episodic memory encoding. Importantly, the results indicate that stimulation targeted outside of the temporal lobe can modulate hippocampal activity and impact behavior. Furthermore, measures of connectivity between brain regions within a functional network can be informative in predicting behavioral effects of stimulation. Our findings have significant implications for developing therapies to treat memory disorders and cognitive impairment using DBS.SIGNIFICANCE STATEMENT Cognitive impairment and memory loss are critical public health challenges. Deep brain stimulation (DBS) is a promising tool for developing strategies to ameliorate memory disorders by targeting brain regions involved in mnemonic processing. Using DBS, our study sheds light on the lesser-known role of the posterior cingulate cortex (PCC) in memory encoding. Stimulating the PCC during encoding impairs subsequent recall memory. The degree of impairment is predicted by stimulation-induced hippocampal gamma oscillations and functional connectivity between PCC and hippocampus. Our findings provide the first causal evidence implicating PCC in memory encoding and highlight the PCC as a favorable target for neuromodulation strategies using a priori connectivity measures to predict stimulation effects. This has significant implications for developing therapies for memory diseases.

Value bias of verbal memory

Abstract A common finding is that items associated with higher reward value are subsequently remembered better than items associated with lower value. A confounding factor is that when a higher value stimuli is presented, this typically signals to participants that it is now a particularly important time to engage in the task. When this was controlled, Madan, Fujiwara, Gerson, and Caplan (2012) still found a large value-bias of memory. Their value-learning procedure, however, explicitly pitted high- against low-value words. Our novel value-learning procedure trained words one at a time, avoiding direct competition between words, but with no difference in words signalling participants to engage in the task. Results converged on null effects of value on subsequent free recall accuracy. Re-analyses attributed Madan et al.’s value-bias to competition between choice items that were paired during learning. Value may not bias memory if it does not signal task importance or induce inter-item competition.

Effects of grasp compatibility on long-term memory for objects

Previous studies have shown action potentiation during conceptual processing of manipulable objects. In four experiments, we investigated whether these motor actions also play a role in long-term memory. Participants categorized objects that afforded either a power grasp or a precision grasp as natural or artifact by grasping cylinders with either a power grasp or a precision grasp. In all experiments, responses were faster when the affordance of the object was compatible with the type of grasp response. However, subsequent free recall and recognition memory tasks revealed no better memory for object pictures and object names for which the grasp affordance was compatible with the grasp response. The present results therefore do not support the hypothesis that motor actions play a role in long-term memory.

The role of episodic context in retrieval practice effects.

The episodic context account of retrieval-based learning proposes that retrieval enhances subsequent retention because people must think back to and reinstate a prior learning context. Three experiments directly tested this central assumption of the context account. Subjects studied word lists and then either restudied the words under intentional learning conditions or made list discrimination judgments by indicating which list each word had occurred in originally. Subjects in both conditions experienced all items for the same amount of time, but subjects in the list discrimination condition were required to retrieve details about the original episodic context in which the words had occurred. Making initial list discrimination judgments consistently enhanced subsequent free recall relative to restudying the words. Analyses of recall organization and retrieval strategies on the final test showed that retrieval practice enhanced temporal organization during final recall. Semantic encoding tasks also enhanced retention relative to restudying but did so by promoting semantic organization and semantically based retrieval strategies during final recall. The results support the episodic context account of retrieval-based learning. (PsycINFO Database Record

P184 Individual transcranial alternating current stimulation (tACS) within the beta range during verbal working memory

Introduction Beta band brain oscillations (13–30 Hz) correlate with cognitive manipulations during language processing ( Weiss and Muller, 2012 ). In particular, they are associated with the active maintenance of stimuli in verbal working memory ( Weiss and Rappelsberger, 2000 ). Therefore, beta oscillations are suited for tACS during verbal memory encoding. Objectives We examined whether 18 Hz tACS stimulation modulates verbal WM performance in a healthy participant. We did this single-case study since most tACS results are based on group studies and we want to test tACS in individual patients with disturbances of verbal WM. Materials & Methods A right-handed female (27 y) had to memorize 600 visually presented concrete words (150 nouns, 150 verbs; randomly presented two times) and do subsequent free recall. tACS in the beta (18 Hz) and alpha (9 Hz) band as well as a sham stimulation was applied in a double-blind multiple treatment design (ABCBCA) on 6 different days with at least 24 h between sessions. tACS-intensity was 350 μA (below individual phosphene and discomfort threshold). 20 min stimulation was applied at left temporo-parietal and right fronto-central sites. Results A significant difference between the stimulation and sham condition (Pearson χ2 = 12.0, p = 0.03, two-tailed) was found which differed for nouns and verbs. During beta stimulation the participant showed a 48% increase of recalled nouns (8% for verbs), during alpha stimulation a 28% (26 % for verbs) and during sham a 20% (36% for verbs) increase. Overall error rate was higher for verbs (Pearson χ2 = 11.73, p = 0.008, two-tailed). The influence of beta vs. alpha stimulation could not be reliably distinguished with the current protocol. Conclusion Although, beta oscillations are important for linking past and present input into a coherent representation of memorized contents ( Weiss and Rappelsberger, 2000 , Kopell and Whittington, 2011 ), no significant difference was found between alpha and beta stimulation. The word category difference is in accordance with previous findings ( Fiori and Cipollari, 2013 ) who revealed better performance for verb versus noun processing when stimulating left frontal in contrast to temporal areas.

Elaborative retrieval: Do semantic mediators improve memory?

The elaborative retrieval account of retrieval-based learning proposes that retrieval enhances retention because the retrieval process produces the generation of semantic mediators that link cues to target information. We tested 2 assumptions that form the basis of this account: that semantic mediators are more likely to be generated during retrieval than during restudy and that the generation of mediators facilitates later recall of targets. Although these assumptions are often discussed in the context of retrieval processes, we noted that there was little prior empirical evidence to support either assumption. We conducted a series of experiments to measure the generation of mediators during retrieval and restudy and to examine the effect of the generation of mediators on later target recall. Across 7 experiments, we found that the generation of mediators was not more likely during retrieval (and may be more likely during restudy), and that the activation of mediators was unrelated to subsequent free recall of targets and was negatively related to cued recall of targets. The results pose challenges for both assumptions of the elaborative retrieval account. (PsycINFO Database Record

Assessment of free and cued recall in Alzheimer's disease and vascular and frontotemporal dementia with 24-item Grober and Buschke test.

Alzheimer's disease (AD), vascular dementia (VaD) and frontotemporal dementia (FTD) are the most common forms of dementia. It is well known that memory deficits in AD are different from those in VaD and FTD, especially with respect to cued recall. The aim of this clinical study was to compare the memory performance in 15 AD, 10 VaD and 9 FTD patients and 20 normal controls by means of a 24-item Grober-Buschke test [8]. The patients' groups were comparable in terms of severity of dementia. We considered free and total recall (free plus cued) both in immediate and delayed recall and computed an Index of Sensitivity to Cueing (ISC) [8] for immediate and delayed trials. We assessed whether cued recall predicted the subsequent free recall across our patients' groups. We found that AD patients recalled fewer items from the beginning and were less sensitive to cueing supporting the hypothesis that memory disorders in AD depend on encoding and storage deficit. In immediate recall VaD and FTD showed a similar memory performance and a stronger sensitivity to cueing than AD, suggesting that memory disorders in these patients are due to a difficulty in spontaneously implementing efficient retrieval strategies. However, we found a lower ISC in the delayed recall compared to the immediate trials in VaD than FTD due to a higher forgetting in VaD.

Order information is used to guide recall of long lists: Further evidence for the item-order account.

Differences in memory for item order have been used to explain the absence of between-subjects (i.e., pure-list) effects in free recall for several encoding techniques, including the production effect, the finding that reading aloud benefits memory compared with reading silently. Notably, however, evidence in support of the item-order account (Nairne, Riegler, & Serra, 1991) has derived primarily from short-list paradigms. We provide novel evidence that the item-order account also applies when recalling long lists. In Experiment 1, participants studied and then free recalled 3 different long lists of words: pure aloud, pure silent, and mixed (half aloud, half silent). A Bayesian analysis supported a null pure-list production effect, and subsequent order analyses were largely consistent with the item-order account. These findings indicate that order information is retained in long-term memory and is useful in guiding subsequent free recall. In Experiment 2, a distractor task was inserted between the study and test phases, ensuring that only long-term memory processes were involved in recall: The pattern of results remained consistent with the item-order account. Order information can be retained in long-term memory for long lists, and is useful in guiding subsequent free recall, extending the domain of the item-order account. (PsycINFO Database Record

Negative evaluation bias for positive self-referential information in borderline personality disorder.

Previous research has suggested that patients meeting criteria for borderline personality disorder (BPD) display altered self-related information processing. However, experimental studies on dysfunctional self-referential information processing in BPD are rare. In this study, BPD patients (N = 30) and healthy control participants (N = 30) judged positive, neutral, and negative words in terms of emotional valence. Referential processing was manipulated by a preceding self-referential pronoun, an other-referential pronoun, or no referential context. Subsequently, patients and participants completed a free recall and recognition task. BPD patients judged positive and neutral words as more negative than healthy control participants when the words had self-reference or no reference. In BPD patients, these biases were significantly correlated with self-reported attributional style, particularly for negative events, but unrelated to measures of depressive mood. However, BPD patients did not differ from healthy control participants in a subsequent free recall task and a recognition task. Our findings point to a negative evaluation bias for positive, self-referential information in BPD. This bias did not affect the storage of information in memory, but may be related to self-attributions of negative events in everyday life in BPD.