• HOME
  • NEWS
  • EXPLORE
    • CAREER
      • Companies
      • Jobs
    • EVENTS
    • iGEM
      • News
      • Team
    • PHOTOS
    • VIDEO
    • WIKI
  • BLOG
  • COMMUNITY
    • FACEBOOK
    • INSTAGRAM
    • TWITTER
Thursday, October 2, 2025
BIOENGINEER.ORG
No Result
View All Result
  • Login
  • HOME
  • NEWS
  • EXPLORE
    • CAREER
      • Companies
      • Jobs
        • Lecturer
        • PhD Studentship
        • Postdoc
        • Research Assistant
    • EVENTS
    • iGEM
      • News
      • Team
    • PHOTOS
    • VIDEO
    • WIKI
  • BLOG
  • COMMUNITY
    • FACEBOOK
    • INSTAGRAM
    • TWITTER
  • HOME
  • NEWS
  • EXPLORE
    • CAREER
      • Companies
      • Jobs
        • Lecturer
        • PhD Studentship
        • Postdoc
        • Research Assistant
    • EVENTS
    • iGEM
      • News
      • Team
    • PHOTOS
    • VIDEO
    • WIKI
  • BLOG
  • COMMUNITY
    • FACEBOOK
    • INSTAGRAM
    • TWITTER
No Result
View All Result
Bioengineer.org
No Result
View All Result
Home NEWS Science News Biology

When Alzheimer’s degrades cells that cross hemispheres, visual memory suffers

Bioengineer by Bioengineer
August 19, 2022
in Biology
Reading Time: 4 mins read
0
Cortices across hemispheres
Share on FacebookShare on TwitterShare on LinkedinShare on RedditShare on Telegram

A new MIT study finds that Alzheimer’s disease disrupts at least one form of visual memory by degrading a newly identified circuit that connects the vision processing centers of each brain hemisphere.

Cortices across hemispheres

Credit: Chinnakkaruppan Adaikkan/MIT PIcower Institute

A new MIT study finds that Alzheimer’s disease disrupts at least one form of visual memory by degrading a newly identified circuit that connects the vision processing centers of each brain hemisphere.

The results of the study, published in Neuron by a research team based at The Picower Institute for Learning and Memory, come from experiments in mice, but provide a physiological and mechanistic basis for prior observations in human patients: the degree of diminished brain rhythm synchrony between counterpart regions in each hemisphere correlates with the clinical severity of dementia.

“We demonstrate that there is a functional circuit that can explain this phenomenon,” said lead author Chinnakkaruppan Adaikkan, a former Picower Institute postdoc who is now an assistant professor in the Centre for Brain Research at the Indian Institute of Science (IISc) in Bangalore. “In a way we uncovered a fundamental biology that was not known before.”

Specifically, Adaikkan’s work identified neurons that connect the primary visual cortex (V1) of each hemisphere and showed that when the cells are disrupted, either by genetic alterations that model Alzheimer’s disease or by direct laboratory perturbations, brain rhythm synchrony becomes reduced and mice become significantly less able to notice when a new pattern appeared on a wall in their enclosures. Such recognition of novelty, which requires visual memory of what was there the prior day, is an ability commonly disrupted in Alzheimer’s.

“This study demonstrates the propagation of gamma rhythm synchrony across the brain hemispheres via the cross hemispheric connectivity,” said study senior author Li-Huei Tsai, Picower Professor and director of The Picower Institute and MIT’s Aging Brain Initiative. “It also demonstrates that the disruption of this circuit in AD mouse models is associated with specific behavioral deficits.”

Cross-hemispheric cells

In the study, Adaikkan, Tsai, Thomas McHugh and co-authors discovered and traced V1 neurons that extended their axons all the way through the corpus callosum, which connects the brain’s hemispheres, to cells in the V1 on the brain’s other side. There, they found, the cross-hemispheric (CH) neurons forged connections, or synapses, with target cells, providing them with “excitatory” stimulation to drive their activity. Adaikkan also found that CH neurons were much more likely to be activated by a novelty discrimination task than V1 neurons in general or neurons in other regions heavily involved in memory such as the hippocampus or the prefrontal cortex.

Curious about how this might differ in Alzheimer’s disease, the team looked at the activity of the cells in two different Alzheimer’s mouse models. The found that CH cell activity was significantly lessened amid the disease. Unsurprisingly, Alzheimer’s mice fared much poorer in novelty discrimination tasks.

The team examined the CH cells closely and found that they gather incoming input from a variety of other cells within their V1 and other regions in their hemisphere that process visual information. When they compared the incoming connections of healthy CH neurons to those in CH cells afflicted with Alzheimer’s, they found that cells in the disease condition had significantly less infrastructure for hosting incoming connections (measured in terms of synapse-hosting spines protruding from the vine-like dendrites that sprawl out of the cell body).

Given the observations correlating reduced brain rhythm synchrony and memory performance in Alzheimer’s, the team wondered if that occurred in the mice, too. To find out, they custom-designed electrodes to measure rhythmic activity simultaneously in all cortical layers of each hemisphere’s V1. They observed that cross-hemispheric synchrony increased notably between the V1s when mice engaged in novelty discrimination but that the synchrony, both at high “gamma” and lower “theta” frequency rhythms, was significantly lower in the Alzheimer’s mice than it was in healthy mice.

Adaikkan’s evidence at that point was strong, but still only suggestive, that CH neurons provided the means by which the V1 regions on each side of the brain could coordinate to enable novelty discrimination, and that this ability became undermined by Alzheimer’s degradation of the CH cells’ connectivity. To more directly determine whether the CH circuit played such a causal, consequential role, the team directly intervened to disrupt them, testing what effect targeted perturbations had.

They found that chemically inhibiting CH cells disrupted rhythm synchrony between V1s, mirroring measures made in Alzheimer’s model mice. Moreover, disrupting CH activity undermined novelty discrimination ability. To further test whether it was the cells’ cross-hemispheric nature that mattered specifically, they engineered CH cells to be controllable with flashes of light (a technology called “optogenetics”). When they shined the light on the connections, they forged in the other hemisphere to inhibit those, they found that doing so again compromised visual discrimination ability.

All together, the study results show that CH cells in V1 connect with neurons in the counterpart area of the opposite hemisphere to synchronize neural activity needed for properly recognizing novelty, but that Alzheimer’s disease damages their ability to do that job.

Adaikkan said he is curious to now look at other potential cross-hemispheric connections and how they may be affected in Alzheimer’s disease, too. He said he also wants to study what happens to synchrony at other rhythm frequencies.

In addition to Adaikkan and Tsai, the study’s other authors are Jun Wang, Karim Abdelall, Steven Middleton, Lorenzo Bozzelli, and Ian Wickersham.

The JPB Foundation, The National Institutes of Health, and the Robert A. and Renee E. Belfer Foundation provided funding for the study.



Journal

Neuron

DOI

10.1016/j.neuron.2022.07.023

Method of Research

Experimental study

Subject of Research

Animals

Article Title

Alterations in a Cross-hemispheric Circuit Associates with Novelty Discrimination Deficits in Mouse Models of Neurodegeneration

Article Publication Date

19-Aug-2022

Share12Tweet8Share2ShareShareShare2

Related Posts

blank

Key Genes for Fish Adaptation: Spotlight on Mechanisms

October 2, 2025
Scientists Say Enhanced Fertility Diagnostics Could Advance Bird Conservation Breeding Programs

Scientists Say Enhanced Fertility Diagnostics Could Advance Bird Conservation Breeding Programs

October 2, 2025

Initiative Aims to Halt Decline of Iconic Butterfly Species

October 1, 2025

Revolutionary Algorithm Enhances Disease Classification Using Omics

October 1, 2025

POPULAR NEWS

  • New Study Reveals the Science Behind Exercise and Weight Loss

    New Study Reveals the Science Behind Exercise and Weight Loss

    90 shares
    Share 36 Tweet 23
  • Physicists Develop Visible Time Crystal for the First Time

    74 shares
    Share 30 Tweet 19
  • New Study Indicates Children’s Risk of Long COVID Could Double Following a Second Infection – The Lancet Infectious Diseases

    71 shares
    Share 28 Tweet 18
  • How Donor Human Milk Storage Impacts Gut Health in Preemies

    64 shares
    Share 26 Tweet 16

About

We bring you the latest biotechnology news from best research centers and universities around the world. Check our website.

Follow us

Recent News

MoS2 Nanosheets Enhance Capacitive Deionization Water Purification

Social Risk Factors Linked to Diabetes Prevalence

Miniature CRISPR–Cas10 Grants Immunity via Inhibition

Subscribe to Blog via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

Join 60 other subscribers
  • Contact Us

Bioengineer.org © Copyright 2023 All Rights Reserved.

Welcome Back!

Login to your account below

Forgotten Password?

Retrieve your password

Please enter your username or email address to reset your password.

Log In
No Result
View All Result
  • Homepages
    • Home Page 1
    • Home Page 2
  • News
  • National
  • Business
  • Health
  • Lifestyle
  • Science

Bioengineer.org © Copyright 2023 All Rights Reserved.