Canada Brain Power

Tag: Memory

  • Better understanding the role of vision in the brain’s representation of space by studying freely moving primates

    Better understanding the role of vision in the brain’s representation of space by studying freely moving primates

    Brain Star Award winner feature: Diego B. Piza, Western University, won this prize based on the excellence of the research and its potential benefits to the health of Canadians. Brain Star Awards are presented by the Canadian Association for Neuroscience (CAN) and the Canadian Institutes of Health’s Institute of Neurosciences, Mental Health and Addiction

    The hippocampus is a structure of the mammalian brain that has been implicated in spatial memory and navigation. Its role has been primarily studied in nocturnal mammals, such as rats, that lack many adaptations for daylight vision. Here, Diego B. Piza, working in the laboratory of Julio Martinez-Trujillo at Western University, demonstrates that during 3D navigation, the common marmoset, a New World primate adapted to daylight, uses different exploration–navigation strategies compared to rats. He further shows that maps of space in the marmoset brain depend on vision-related cues and object relationships used as landmarks for navigation. It is likely that similar encoding mechanisms exist in other diurnal mammals, including humans.

    To explore their environment, marmosets predominantly use rapid head-gaze shifts for visual exploration while remaining stationary. During active movement, marmosets stabilize their head, in contrast to rats, who use low-speed head movements to scan the environment as they locomote. This work suggests that spatial memory in primates may rely on anchoring sequences of views to specific places, providing a unique mechanism for encoding spatial experiences.

    This publication represents a major technical and conceptual achievement in neuroscience.

    Read the full story: https://can-acn.org/brain-star-award-winner-diego-b-piza/

    Article citation

    Piza, D.B., Corrigan, B.W., Gulli, R.A., Do Carmo, S., Cuello, A.C., Muller, L., Martinez-Trujillo, J. Primacy of vision shapes behavioral strategies and neural substrates of spatial navigation in marmoset hippocampus. Nat Commun 15, 4053 (2024). https://doi.org/10.1038/s41467-024-48374-2

    https://doi.org/10.1038/s41467-024-48374-2

  • Better understanding how ensembles of neurons are recruited in memory formation.

    Better understanding how ensembles of neurons are recruited in memory formation.

    Brain Star Award Feature: Andrew Mocle, University of Toronto, won this prize based on the excellence of the research and its potential benefits to the health of Canadians. Brain Star Awards are presented by the Canadian Association for Neuroscience (CAN) and the Canadian Institutes of Health’s Institute of Neurosciences, Mental Health and Addiction

    The hippocampus is a critical brain region for encoding and recall of episodic memories. The physical trace left in the brain by memory formation is called an ‘engram’, and the process by which new engrams are formed is still unclear. In this work, Andrew Mocle, working in the laboratory of Sheena Josselyn, used advanced imaging techniques to track neurons and their patterns of activity before, during, and after memory encoding. The resulting data prompted a new engram formation model, whereby small ensembles of neurons (instead of individual cells) are allocated to an engram depending on their average excitability at the time of learning. The demonstration that highly-excitable ensembles are preferentially allocated to encode newly learned information represents a major conceptual advance in the study of how memories are stored in the brain.

    Read more: https://can-acn.org/brain-star-award-winner-andrew-mocle/

    Featured scientific publication: Mocle, Andrew J., Adam I. Ramsaran, Alexander D. Jacob, Asim J. Rashid, Alessandro Luchetti, Lina M. Tran, Blake A. Richards, Paul W. Frankland, and Sheena A. Josselyn. “Excitability Mediates Allocation of Pre-Configured Ensembles to a Hippocampal Engram Supporting Contextual Conditioned Threat in Mice.” Neuron 112, no. 9 (May 1, 2024): 1487-1497.e6.

    https://doi.org/10.1016/j.neuron.2024.02.007

  • Hormone Therapy Delivery Method May Influence Memory After Menopause, New CAMH Study Finds

    Hormone Therapy Delivery Method May Influence Memory After Menopause, New CAMH Study Finds

    Findings support precision approaches to hormone therapy for women in midlife and beyond

    Source: CAMH News

    Estradiol, the most common form of the estrogens used in hormone therapy, may influence different types of memory during the menopausal transition and beyond depending on how it is delivered – through the skin or orally – according to new research led by Dr. Liisa Galea, senior scientist and womenmind Treliving Family Chair in Women’s Mental Health at the Centre for Addiction and Mental Health (CAMH). Published today in the journal Neurology, the study is the first to show that the same hormone can have distinct cognitive effects depending on delivery method – highlighting the need for more personalized approaches to women’s brain health. 

    “This is the first study to show that estradiol’s effects on memory vary depending on how it is delivered,” said Dr. Galea. “It also reinforces that cognition is multifaceted, and hormone therapy should be tailored to each woman’s health profile and menopause experience.”

    The study analyzed data from 7,251 cognitively healthy postmenopausal participants using data from the Canadian Longitudinal Study on Aging, a national research project following Canadians over 20 years to understand how different factors affect health and aging. Participants completed tests measuring episodic memory (recalling past events), prospective memory (remembering to perform future tasks) and executive function (planning and problem-solving). Among participants, 4 per cent used transdermal estradiol (delivered through the skin via patches, gels, or vaginal applications), 2 per cent used oral estradiol pills, and 94 per cent did not use hormone therapy. 

    The researchers found that the earlier someone experienced menopause, the more it affected cognition across all the areas tested. Transdermal estradiol users demonstrated better episodic memory compared to non-users, while oral estradiol users showed improved prospective memory. This suggests that estradiol’s delivery method impacts different aspects of cognition. Hormone therapy did not appear to affect executive function in either case, and all findings were consistent regardless of the number of children participants had or their genetic risk factors. Notably, estradiol therapy was never associated with poorer cognitive outcomes, reaffirming its potential positive value for women’s brain health in menopause. 

    Dr. Galea added: “There’s clearly a lot more we need to understand about how different estrogens can support the brain health of older women. To truly personalize care, we need a better sense of when, how, and for whom it is optimal to use these hormones to support memory. This will be a key area of future exploration.”

    She also emphasized the lack of investment in women’s brain health research. “Only six to seven per cent of health research grants from Canada’s largest health granting agency address women’s health issues but mostly focused on pregnancy — with just 0.18 per cent across 15 years on menopause,” she said. “Women’s brain health remains understudied, underfunded, and overgeneralized. We urgently need more evidence to support women in midlife and beyond. That is why I am thrilled that, with new funding from Wellcome Leap, we are developing an Alzheimer’s disease prediction tool specifically for women, leveraging machine learning and big data.” 

    About the Centre for Addiction and Mental Health (CAMH) 

    The Centre for Addiction and Mental Health (CAMH) is Canada’s largest mental health and addiction teaching hospital and a world leading research centre in this field. CAMH combines clinical care, research, education, policy development and health promotion to help transform the lives of people affected by mental illness and addiction. CAMH is fully affiliated with the University of Toronto and is a Pan American Health Organization/World Health Organization Collaborating Centre. For more information, please visit camh.ca 
    or follow @CAMHnews on Bluesky and LinkedIn. 

    Media Contact: 
    media@camh.ca 

  • Memory network reorganization in temporal lobe epilepsy

    Memory network reorganization in temporal lobe epilepsy

    Brain Star Award winner profile by the Canadian Association for Neuroscience

    Dr. Jessica Royer, McGill University

    Scientific publication

    Royer, J., Larivière, S., Rodriguez-Cruces, R., Cabalo, D. G., Tavakol, S., Auer, H., Ngo, A., Park, B., Paquola, C., Smallwood, J., Jefferies, E., Caciagli, L., Bernasconi, A., Bernasconi, N., Frauscher, B., & Bernhardt, B. C. (2023). Cortical microstructural gradients capture memory network reorganization in temporal lobe epilepsy. Brain, 146(9), 3923-3937.

    https://academic.oup.com/brain/article/146/9/3923/7134129?login=false

    Temporal lobe epilepsy is a common chronic neurological condition that is typically associated with altered structure and function of paralimbic brain regions. Temporal lobe epilepsy particularly affects episodic memory, which encodes information about past events and experiences. Research by Jessica Royer and colleagues identified memory network reorganization that could underpin these memory defects.

    Memory difficulties significantly challenge quality of life for patients with temporal lobe epilepsy, underscoring the need to understand the neural mechanisms at play. Work by Jessica Royer and colleagues harnessed a novel approach to assess the microstructure of specific brain areas based on high-resolution magnetic resonance imaging (MRI). By comparing the microstructure in the brain of 21 patients and 35 healthy controls, they found alterations in paralimbic brain regions on the same side of the brain as the area where seizures initiated, and observed that the severity of these changes was associated with memory impairment.

    The present work describes a novel view of the complex interplay between brain microarchitecture and memory. The authors used a disease model of memory dysfunction to grant insight into the neuroanatomical mechanisms of episodic memory. These findings highlight the importance of paralimbic microstructure to support functional memory networks and optimal recall performance. This flexible approach furthermore opens the way for investigations of structure-function associations beyond memory systems, and could be generalized to study the microarchitectural basis of diverse ensembles of cognitive abilities in different neurological disorders. In addition to this impact on fundamental research in brain science, this work also contributes to clinical perspectives and patient care in epilepsy.

    Epilepsy is among the most prevalent chronic neurological disorders, affecting approximately 65 million individuals worldwide, and TLE in particular is one of the most common pharmaco-resistant epilepsies. A better understanding of this condition can measurably improve the lives of patients and their families by informing both diagnostics and prognostics.

    Furthermore, this research localized microstructural changes in individual patients, which could lead to more precise identification of targets for curative surgery. Moreover, the distributed microanatomical substrates of episodic memory networks uncovered in this work offer novel investigation pathways to improve predictions of post-surgical outcomes.

    About Dr. Jessica Royer

    Dr. Jessica Royer performed this work as a PhD candidate in the laboratories of Boris Bernhardt and Birgit Frauscher, at McGill University. As a board-certified neuropsychologist, Jessica Royer is particularly interested in clarifying the interplay between brain structure and cognitive function, and how such structure-function relationships maybe be altered in neurological and psychiatric disease. Her work notably leverages focal epilepsy as a disease model to investigate the impact of lesions on large-scale brain function and cognitive abilities. As first author of this publication, Jessica Royer contributed to the study design, data collection, data curation, data processing, statistical analyses, figure conceptualization, manuscript writing and revisions, response to reviewers, and managing proofs for publication of the paper. In keeping with her strong commitment to open neuroscience, Jessica Royer also took charge of openly sharing post-processed patient and healthy control data collected as part of this study.

    Sources of funding

    Funding for this research was provided by the Canadian Institutes of Health Research (CIHR), the Natural Sciences and Engineering Research Council of Canada (NSERC), the SickKids Foundation, the Brain Canada Foundation, Helmholtz International BigBrain Analytics and Learning Laboratory (HIBALL), Fonds de Recherche du Québec—Santé (FRQS) and the Canada Research Chairs program.

  • The cellular secret of how memories are made, and lost

    The cellular secret of how memories are made, and lost

    From: SickKids news

    Scientists use a peptide to strengthen connections between brain cells and restore memory in a pre-clinical model.

    Research led at The Hospital for Sick Children (SickKids) is illuminating the mechanism underlying memory, which could result in future therapeutic targets for conditions such as Alzheimer’s disease and dementia. 

    Alzheimer’s disease is a condition that causes memory loss, characterized by the accumulation of a protein, called A-beta, in the brain that damages neurons and their connections.

    Published in Nature Neuroscience, Drs. Paul Frankland and Sheena Josselyn, Senior Scientists in the Neurosciences & Mental Health program, used a peptide to block adverse effects of the accumulation of A-beta in pre-clinical models – a technique that showed promise in restoring memory.

    (more…)

  • Distinct neural codes underlie long- and short-term memory in different regions of the primate brain.

    Distinct neural codes underlie long- and short-term memory in different regions of the primate brain.

    Human memory can be divided into long and short-term according to the time information can remain stored and have been associated to different brain regions. The hippocampus (HPC) has been associated with the formation of long-term memories stored as changes in the strength of synapses that can last decades. On the other hand, the Lateral Prefrontal Cortex (LPFC) has been associated with short-term memory, like being able to shortly remember a phone number, which is temporarily stored for a matter of seconds. Benjamin Corrigan, PhD student at the University of Western Ontario, identified distinct neural codes, or patterns of neuron firing, in the two brain regions by recording brain activity in primates performing learning tasks in virtual reality settings. These distinct neural codes elucidate some differences in how the neurons in these regions communicate, and how these methods of communication can facilitate the type of memory that each region is involved in. This knowledge can help guide research into memory formation and treatments for diseases like Alzheimer’s, where memory is impaired.

    Benjamin Corrigan was awarded a Brain Star award by CIHR’s Institute of Neuroscience, Mental Health and Addiction and the Canadian Association for Neuroscience for these discoveries.

    In this study, the researchers recorded the responses of neurons in both brain areas (hippocampus and lateral frontal cortex) during different tasks that require long and short term memory. They found that the hippocampus and the prefrontal cortex use different neural codes to represent similar information. Hippocampal neurons fire action potentials in bursts, which can trigger changes in the strength of connections between neurons (synapses) during the formation of long-term memories. On the other hand, lateral prefrontal cortex neurons fire action potentials more sparsely, avoiding the strengthening of synapses but allowing longer trains of action potentials that temporarily encode memories.

    While the propensity for bursting of the hippocampus was well known, little had been done to look at the information available in the bursts. Discovering that there was similar information available between the burst code and spike code for the hippocampus could be an important step towards understanding how memories are formed. While there are informative spikes outside of bursts, further research determining whether these bursts are critical to the formation of memory is an exciting new research path.

    The hippocampus and the prefrontal cortex are both regions that receive highly processed information and are also regions that are affected by neurodevelopmental and neurodegenerative diseases. This paper elucidates some differences in how the neurons in these regions communicate, and how the method of communication, bursting or sparse firing, can facilitate the type of memory that each region is involved in. This knowledge can help guide research into memory formation and treatments for diseases where memory is disrupted.

    About Benjamin Corrigan

    Benjamin Corrigan performed this study as a PhD student in the laboratory of Dr. Julio Martinez-Trujillo at the University of Western Ontario. He performed most experiments, developed approaches to analyze the data, wrote the code for the analyses, and the first draft of the manuscript, and along with his supervisor addressed reviews and edits from fellow authors.

    Funding sources

    CIHR, NSERC, OGS, BrainSCAN and NeuroNex (National Science Foundation).

    Scientific publication

    Corrigan, B. W., Gulli, R. A., Doucet, G., Roussy, M., Luna, R., Pradeepan, K. S., Sachs, A.J., Martinez-Trujillo, J. C. (2022). Distinct neural codes in primate hippocampus and lateral prefrontal cortex during associative learning in virtual environments. Neuron, 110(13), 2155-2169.e4. https://doi.org/10.1016/j.neuron.2022.04.016

    https://www.sciencedirect.com/science/article/abs/pii/S0896627322003610

  • Study first to examine how early memory changes as we age at a cellular level

    Study first to examine how early memory changes as we age at a cellular level

    SickKids researchers discover that a matrix called the perineuronal net may be responsible for why human memories become more specific throughout childhood.

    How do our brains become capable of creating specific memories? In one of the first preclinical studies to examine memory development in youth, a research team at The Hospital for Sick Children (SickKids) may have identified a molecular cause for memory changes in early childhood. (more…)

  • CIHR Faces of Health Research 2022: Dylan Smith

    CIHR Faces of Health Research 2022: Dylan Smith

    All humans require sleep daily to be physically and mentally healthy. Sleep is known to play a role in solidifying new memories and learning. However, researchers do not fully understand the processes in the brain that underlie the consolidation of newly acquired information and skills during sleep.

    With the support of a CIHR Fellowship, Dr. Dylan Smith from University of Ottawa Institute for Mental Health Research is combining electroencephalography (EEG) with functional magnetic resonance imaging (fMRI) to peer inside the brains of healthy volunteers and study these processes at work.

    Study participants are placed inside an MRI brain scanner wherein they are instructed to solve a visual puzzle before falling asleep. Dr. Smith is analyzing the data from these brain scans with a focus on sleep spindles – fast bursts of brain activity linked to sleep and memory – in parts of the brain associated with learning, such as the prefrontal cortex, hippocampus, and striatum. This research is providing new insight into how our brains integrate new learning while we’re sleeping.

    Learn more about the Faces of health research 2022 on the CIHR website.

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