Breaking News
May 3, 2019 - Vaping and Smoking May Signal Greater Motivation to Quit
May 3, 2019 - Dementia looks different in brains of Hispanics
May 3, 2019 - Short-Staffed Nursing Homes See Drop In Medicare Ratings
May 3, 2019 - Study of teens with eating disorders explores how substance users differ from non-substance users
May 3, 2019 - Scientists develop new video game that may help in the study of Alzheimer’s
May 3, 2019 - Arc Bio introduces Galileo Pathogen Solution product line at ASM Clinical Virology Symposium
May 3, 2019 - Cornell University study uncovers relationship between starch digestion gene and gut bacteria
May 3, 2019 - How to Safely Use Glucose Meters and Test Strips for Diabetes
May 3, 2019 - Anti-inflammatory drugs ineffective for prevention of Alzheimer’s disease
May 3, 2019 - Study tracks Pennsylvania’s oil and gas waste-disposal practices
May 3, 2019 - Creating a better radiation diagnostic test for astronauts
May 3, 2019 - Vegans are often deficient in these four nutrients
May 3, 2019 - PPDC announces seed grants to develop medical devices for children
May 3, 2019 - Study maps out the frequency and impact of water polo head injuries
May 3, 2019 - Research on Reddit identifies risks associated with unproven treatments for opioid addiction
May 3, 2019 - Good smells may help ease tobacco cravings
May 3, 2019 - Medical financial hardship found to be very common among people in the United States
May 3, 2019 - Researchers develop multimodal system for personalized post-stroke rehabilitation
May 3, 2019 - Study shows significant mortality benefit with CABG over percutaneous coronary intervention
May 3, 2019 - Will gene-editing of human embryos ever be justifiable?
May 3, 2019 - FDA Approves Dengvaxia (dengue vaccine) for the Prevention of Dengue Disease in Endemic Regions
May 3, 2019 - Why Tonsillitis Keeps Coming Back
May 3, 2019 - Fighting the opioid epidemic with data
May 3, 2019 - Maggot sausages may soon be a reality
May 3, 2019 - Deletion of ATDC gene prevents development of pancreatic cancer in mice
May 2, 2019 - Targeted Therapy Promising for Rare Hematologic Cancer
May 2, 2019 - Alzheimer’s disease is a ‘double-prion disorder,’ study shows
May 2, 2019 - Reservoir bugs: How one bacterial menace makes its home in the human stomach
May 2, 2019 - Clinical, Admin Staff From Cardiology Get Sneak Peek at Epic
May 2, 2019 - Depression increases hospital use and mortality in children
May 2, 2019 - Vicon and NOC support CURE International to create first gait lab in Ethiopia
May 2, 2019 - Researchers use 3D printer to make paper organs
May 2, 2019 - Viral infection in utero associated with behavioral abnormalities in offspring
May 2, 2019 - U.S. Teen Opioid Deaths Soaring
May 2, 2019 - Opioid distribution data should be public
May 2, 2019 - In the Spotlight: “I’m learning every single day”
May 2, 2019 - 2019 Schaefer Scholars Announced
May 2, 2019 - Podcast: KHN’s ‘What The Health?’ Bye-Bye, ACA, And Hello ‘Medicare-For-All’?
May 2, 2019 - Study describes new viral molecular evasion mechanism used by cytomegalovirus
May 2, 2019 - SLU study suggests a more equitable way for Medicare reimbursement
May 2, 2019 - Scientists discover first gene involved in lower urinary tract obstruction
May 2, 2019 - Researchers identify 34 genes associated with increased risk of ovarian cancer
May 2, 2019 - Many low-income infants receive formula in the first few days of life, finds study
May 2, 2019 - Global study finds high success rate for hip and knee replacements
May 2, 2019 - Taking depression seriously: What is it?
May 2, 2019 - With Head Injuries Mounting, Will Cities Put Their Feet Down On E-Scooters?
May 2, 2019 - Scientists develop small fluorophores for tracking metabolites in living cells
May 2, 2019 - Study casts new light into how mothers’ and babies’ genes influence birth weight
May 2, 2019 - Researchers uncover new brain mechanisms regulating body weight
May 2, 2019 - Organ-on-chip systems offered to Asia-Pacific regions by Sydney’s AXT
May 2, 2019 - Adoption of new rules drops readmission penalties against safety net hospitals
May 2, 2019 - Kids and teens who consume zero-calorie sweetened beverages do not save calories
May 2, 2019 - Improved procedure for cancer-related erectile dysfunction
May 2, 2019 - Hormone may improve social behavior in autism
May 2, 2019 - Alzheimer’s disease may be caused by infectious proteins called prions
May 2, 2019 - Even Doctors Can’t Navigate Our ‘Broken Health Care System’
May 2, 2019 - Study looks at the impact on criminal persistence of head injuries
May 2, 2019 - Honey ‘as high in sugars as table sugar’
May 2, 2019 - Innovations to U.S. food system could help consumers in choosing healthy foods
May 2, 2019 - FDA Approves Mavyret (glecaprevir and pibrentasvir) as First Treatment for All Genotypes of Hepatitis C in Pediatric Patients
May 2, 2019 - Women underreport prevalence and intensity of their own snoring
May 2, 2019 - Concussion summit focuses on science behind brain injury
May 2, 2019 - Booker’s Argument For Environmental Justice Stays Within The Lines
May 2, 2019 - Cornell research explains increased metastatic cancer risk in diabetics
May 2, 2019 - Mount Sinai study provides fresh insights into cellular pathways that cause cancer
May 2, 2019 - Researchers to study link between prenatal pesticide exposures and childhood ADHD
May 2, 2019 - CoGEN Congress 2019: Speakers’ overviews
May 2, 2019 - A new strategy for managing diabetic macular edema in people with good vision
May 2, 2019 - Sagent Pharmaceuticals Issues Voluntary Nationwide Recall of Ketorolac Tromethamine Injection, USP, 60mg/2mL (30mg per mL) Due to Lack of Sterility Assurance
May 2, 2019 - Screen time associated with behavioral problems in preschoolers
May 2, 2019 - Hormone reduces social impairment in kids with autism | News Center
May 2, 2019 - Researchers synthesize peroxidase-mimicking nanozyme with low cost and superior catalytic activity
May 2, 2019 - Study results of a potential drug to treat Type 2 diabetes in children announced
May 2, 2019 - Multigene test helps doctors to make effective treatment decisions for breast cancer patients
May 2, 2019 - UNC School of Medicine initiative providing unique care to dementia patients
May 2, 2019 - Nestlé Health Science and VHP join forces to launch innovative COPES program for cancer patients
May 2, 2019 - Study examines how our brain generates consciousness and loses it during anesthesia
May 2, 2019 - Transition Support Program May Aid Young Adults With Type 1 Diabetes
May 2, 2019 - Study shows how neutrophils exacerbate atherosclerosis by inducing smooth muscle-cell death
May 2, 2019 - Research reveals complexity of how we make decisions
Recalling memories in context

Recalling memories in context

Participants first encoded scene-object pairs, followed by retrieval or restudy of one of the 2 objects associated with each scene. Retrieval targets (cat) and restudy targets (clock) were contrasted to assess the testing effect, whereas retrieval nontargets (avocado) and restudy nontargets (tie) were contrasted to assess RIFA. In experiment 1, participants memorized each object either once or thrice. In experiment 2, practice memorization was performed thrice. Adapted from: PNAS, doi: 10.1073/pnas.1800006115

Information recall goes beyond memory access to powerfully allow long-term memory enhancement. Using human brain imaging, researchers in the UK and US have observed that an attempt to remember a specific event, accompanied the re-activation of additional information from the same event. In a recent study conducted by Tanya R. Jonker and co-workers at the Department of Psychology, memories of the past were shown to be organized as integrated events. The study showed that even the act of recalling a minor aspect of an event will engage brain networks with powerful effects, to retain information from the entire event. The outcomes of the study were published in the Proceedings of the National Academy of Sciences (PNAS).

Memory and recall are complex processes involving contextual and specific information. Although the act of remembering can enhance long-term retention of the retrieved information, neural and cognitive mechanisms behind such memory enhancements are not yet understood. One possibility is that the process of remembering can reactivate a broader episodic context.

In the study, the researchers found that multiple attempts at memory retrieval enhanced long-term retention of the recovered object and a non-target object, in the shared scene context. Using functional magnetic resonance imaging (fMRI) data in a second experiment, the researchers found that memory retrieval resulted in greater neural reactivation of both target objects and contextually linked objects. Reactivation occurred in a network of medial and lateral parietal lobe regions linked to recollection of episodes. Retrieving memories enhanced information retention, linked broader context of the event in the hippocampus and in the posterior medial network of parietal cortical areas (termed the default mode network). During memory retrieval, the regions played complementary roles to support reactivation of episodically linked information.

Human memory is assumed to form during encoding, and a retrieval process is useful to access the stored representation, previously detailed in retrieval-induced facilitation (RIFA). Although extensive research efforts are focused on memory retrieval; little is known about the driving mechanisms. Two main explanations assume that:

  1. Continuous experiences are segmented into discrete events and organized into memory. Retrieval of an item could reactivate the spatiotemporal event in which the item was encountered. The benefits of retrieval practice (testing effect) can spread to other items from the same context (RIFA). The retrieval practice may also reactivate representations in the hippocampus, binding the item and contextual information. Further retrieval can result in reactivating the lateral and medial parietal regions known as the posterior medial (PM) or default mode network.
  2. The second explanation assumes that participants encode item-to-item associations and retrieval of a single item could directly reactivate and strengthen features associated with the item.

The key difference between the two hypotheses is that in the episodic reactivation hypothesis, RIFA is driven by contextual information reactivation. Whereas during semantic hypothesis, RIFA is driven by reactivating semantic features of associated items. The behavioral evidence of RIFA was only observed in studies that used semantically organized materials.

At present, there is little evidence to suggest that the recovery of spatiotemporal context from a past event can enhance retention of the retrieved and contextually linked information from the same event. To address the question, the scientists conducted two experiments aiming to shed light on the cognitive and neural mechanisms underlying retrieval-based memory enhancement. The focus was on the recovery of target information and on contextually related, non-retrieved information.

In the study, experiment 1 established a method to investigate how retrieval of an object impacted later memory to retrieve a contextually linked object. In experiment 2, the researchers conducted fMRI and representational similarity analysis (RSA) to identify reactivation of target and non-target information during the retrieval process.

Method to analyze representation similarity. To assess reactivation, patterns of activity during retrieval or restudy were compared with patterns for the encoding trial in each of our regions of interest (ROI). Adapted from: PNAS, doi: 10.1073/pnas.1800006115

In the first experiment, participants were divided into two groups to understand how repeated retrieval affected episodic memory representation. One group performed retrieval or restudy on each target object once, a second group performed the practice thrice. A cued recall test administered the next day revealed that retention enhanced tested objects in the retrieval practice condition relative to the restudy condition for both groups. Retrieval-induced facilitation (RIFA) was, however, only present after three practice cycles, demonstrating that repeated retrieval played an important role in facilitating memory for nontarget information. The findings suggested that retrieval processes may qualitatively change across the course of repeated retrieval; this was explored in the second experiment.

In the second experiment, the researchers examined reactivation during retrieval to determine the type(s) of information that participants accessed during memory search. The findings focused on the hippocampus and on two cortical networks shown to play a key role in memory encoding and retrieval. The hippocampus was examined since single-unit recording studies in rats had shown the hippocampus replayed recent experiences during sleep and wakeful rest to stabilize new memories. Evidence suggested that retrieval may be analogous to replay due to target item retention. To examine reactivation in these networks in the brain, the researchers used RSA and fMRI data. They examined the degree of similarity between patterns of neural activity across different trials based on the assumption that cognitively similar events should result in similar neural pattern profiles. For instance, if the retrieval of an image of a kitten accompanied the contextually linked image of an avocado, the patterns of neural activity encoding the avocado and retrieval of the kitten must be high.

The study examined two major networks that interfaced with the hippocampus during memory processing. The PM network – which includes the precuneus, posterior cingulate (PCC), retrosplenial cortex (RSC), angular gyrus and the parahippocampal cortex (PHC). The PM network was found to play a key role in event detail recollection and event model processing. In contrast, the AT network comprising the lateral orbifrontal cortex was implicated in processing unitized items and semantic information.

Experiments 1 and 2 showed that multiple retrieval attempts enhanced long-term memory retention of retrieved and non-target objects that shared the same context. Experiment 2 showed that relative to restudy, retrieval enhanced neural reactivation representation of target objects and contextually linked objects. The findings collectively indicated that during recall of a particular object, information reactivation from the broader episode enhanced retention of the recalled and episodically linked information. The findings were consistent with previous observations. By retrieving a single object, people reactivated an entire episode to facilitate the integration of retrieval targets and linked items.

Based on the outcomes, the scientists assumed the possibility of a medial subnetwork involving the PHC and RSC, maintaining a specific sensory contextual representation that was updated with each retrieval attempt. In comparison, the parietal subnetwork maintained a schematic representation of the event. The predictions also aligned with recently published neuroimaging findings.

Recent research has consistently deconstructed the practice of retrieval to strongly enhance long-term retention, albeit poor understanding of neural and cognitive mechanisms driving the enhancement. The study showed that reactivation in the parietal regions of the PM network retrieved target information, alongside information linked within the same episodic content. The findings highlighted the importance of spatiotemporal context in organizing information in episodic memory.

In reality, information experienced within an event is highly structured and ingrained, more so than that seen with the experimental stimuli used in the study. The results captured a fundamental aspect of the daily human experience with memory. Remembering a single detail from the past can have far-reaching effects on retaining an entire event. The findings can be used to devise methods to improve learning, to enhance memory in patients with amnesia disorders and in general for improved cognition.


Explore further:
New insights into the way the brain combines memories to solve problems

More information:
Tanya R. Jonker et al. Neural reactivation in parietal cortex enhances memory for episodically linked information, Proceedings of the National Academy of Sciences (2018). DOI: 10.1073/pnas.1800006115

Charan Ranganath et al. Two cortical systems for memory-guided behaviour, Nature Reviews Neuroscience (2012). DOI: 10.1038/nrn3338

Journal reference:
Proceedings of the National Academy of Sciences

Nature Reviews Neuroscience

About author

Related Articles