Nav: Home

Schizophrenia: When the thalamus misleads the ear

May 26, 2020

There is an extremely high probability that individuals with 22q11.2 micro deletion syndrome - a rare genetic disorder - will develop schizophrenia together with one of its most common symptoms, auditory hallucinations. Scientists at the University of Geneva (UNIGE) and the Synapsy National Centre of Competence in Research (NCCR) have been studying this category of patients. They have succeeded in linking the onset of this hallucinatory phenomenon with the abnormal development of certain substructures of a region deep in the brain called the thalamus. These thalamic nuclei have been identified using a combination of functional and structural magnetic resonance imaging. They are involved in processing memory and hearing among other things. The authors suggest that there might be an explanation for these auditory hallucinations that is almost "mechanical": the immaturity of the axon connections that bind the thalamic nuclei to the cortex areas responsible for hearing. The results, published in the journal Biological Psychiatry: CNNI, pave the way for a new understanding of the pathophysiology and treatment of schizophrenia.

Several studies in recent years have demonstrated a link between schizophrenia and abnormalities in the development of the thalamus, a deep brain region that processes a number of cognitive functions, including working memory and hearing. More specifically, the volume of the thalamus is smaller on average in schizophrenic patients. Accordingly, it has been possible to link the onset of auditory hallucinations with an overly-intense neuronal connectivity between the thalamus and auditory cortex. An auditory hallucination is defined as the perception of sound in the absence of an external sound source. It is one of the most characteristic symptoms of schizophrenia, a psychotic disorder that affects approximately 1% of the population.

"We used a cohort of patients that is unique in the world in an attempt to analyse the mechanism behind this hallucinatory phenomenon in more detail," begins Stephan Eliez, a professor in the Department of Psychiatry in UNIGE's Faculty of Medicine. "For the last 19 years, a program backed by the University of Geneva has helped us enlist and monitor individuals suffering from a rare neurogenetic syndrome: 22q11.2 micro deletion syndrome, which is caused by the absence of a small piece of DNA in chromosome 22. These patients are often prone to auditory hallucinations among other things. More importantly, 30 to 35% of them develop schizophrenia during their lifetime. This is the category with the highest risk of falling victim to the psychotic disorder."

Monitoring from childhood to adulthood

This cohort, made up of over 200 patients living in Switzerland, France, Belgium, Luxembourg and England, represents a unique opportunity to follow individuals from childhood to adulthood and submitting them to a regular battery of tests (medical imaging, genetic analyses, etc. ). It offers the chance to understand the neuro-developmental processes involved in the onset of schizophrenia and possibly to determine potential treatments that could delay, slow down or even halt the progression of psychotic symptoms.

The study focused on 230 people aged 8 to 35 years: 120 from the cohort and 110 healthy individuals who served as controls. Participants underwent a brain scan every three years using functional and structural magnetic resonance imaging. They were not given any task to complete: the machine simply recorded the brain activity generated by floating thoughts activating the major neural networks by turns. The scientists focused in particular on the various sub-structures of the thalamus that each has its own functions.

Unparalleled precision

"We discovered that the thalamic nuclei involved in auditory and visual sensory processing and working memory are smaller in people with deletion syndrome than in others," explains Valentina Mancini, a researcher in UNIGE's Department of Psychiatry and the article's first author. "And among people with deletion syndrome, the volume of the medial geniculate nucleus (the MGN, one of the sub-parts of the thalamus involved in the auditory pathways) and that of the other nuclei used in memory are smaller in the group with auditory hallucinations relative to the group that doesn't experience any. The size of the MGN differs between the two groups from childhood with a divergent developmental trajectory".

The scientists made a further observation: in the patients suffering from auditory hallucinations, they noticed a hyper-connectivity between the thalamic nuclei and cortical areas devoted to the primary processing of hearing and Wernicke's area, which is highly significant for understanding language. This type of thalamo-cortical hyper-connection is normal during childhood, when the neural networks are being formed. The fact that it persists during adolescence and then into adulthood is the sign that the connections have never reached maturity.

"This characteristic could provide an almost mechanical explanation for the hallucinatory phenomenon in these patients," notes Stephan Eliez. "Our results also open up new perspectives for the more general understanding of the pathophysiology of schizophrenia. Identifying the markers that foreshadow the development of the disease in such detail gives us many new targets for action using specific neuroprotective drugs, for example, to prevent symptoms as much as possible."
-end-


Université de Genève

Related Schizophrenia Articles:

Schizophrenia: When the thalamus misleads the ear
Scientists at the University of Geneva (UNIGE) and the Synapsy National Centre of Competence in Research (NCCR) have succeeded in linking the onset of auditory hallucinations - one of the most common symptoms of schizophrenia - with the abnormal development of certain substructures of a region deep in the brain called the thalamus.
Unlocking schizophrenia
New research, led by Prof. LIU Bing and Prof. JIANG Tianzi from the Institute of Automation of the Chinese Academy of Sciences and their collaborators have recently developed a novel imaging marker that may help in the personalized medicine of psychiatric disorders.
Researchers discover second type of schizophrenia
In a study of more than 300 patients from three continents, over one third had brains that looked similar to healthy people.
New clues into the genetic origins of schizophrenia
The first genetic analysis of schizophrenia in an ancestral African population, the South African Xhosa, appears in the Jan.
Dietary supplement may help with schizophrenia
A dietary supplement, sarcosine, may help with schizophrenia as part of a holistic approach complementing antipsychotic medication, according to a UCL researcher.
Schizophrenia: Adolescence is the game-changer
Schizophrenia may be related to the deletion syndrome. However, not everyone who has the syndrome necessarily develops psychotic symptoms.
Study suggests overdiagnosis of schizophrenia
In a small study of patients referred to the Johns Hopkins Early Psychosis Intervention Clinic (EPIC), Johns Hopkins Medicine researchers report that about half the people referred to the clinic with a schizophrenia diagnosis didn't actually have schizophrenia.
The ways of wisdom in schizophrenia
Researchers at UC San Diego School of Medicine report that persons with schizophrenia scored lower on a wisdom assessment than non-psychiatric comparison participants, but that there was considerable variability in levels of wisdom, and those with higher scores displayed fewer psychotic symptoms.
Recognizing the uniqueness of different individuals with schizophrenia
Individuals diagnosed with schizophrenia differ greatly from one another. Researchers from Radboud university medical center, along with colleagues from England and Norway, have demonstrated that very few identical brain differences are shared amongst different patients.
Resynchronizing neurons to erase schizophrenia
Today, a decisive step in understanding schizophrenia has been taken.
More Schizophrenia News and Schizophrenia Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: IRL Online
Original broadcast date: March 20, 2020. Our online lives are now entirely interwoven with our real lives. But the laws that govern real life don't apply online. This hour, TED speakers explore rules to navigate this vast virtual space.
Now Playing: Science for the People

#574 State of the Heart
This week we focus on heart disease, heart failure, what blood pressure is and why it's bad when it's high. Host Rachelle Saunders talks with physician, clinical researcher, and writer Haider Warraich about his book "State of the Heart: Exploring the History, Science, and Future of Cardiac Disease" and the ails of our hearts.
Now Playing: Radiolab

Falling
There are so many ways to fall–in love, asleep, even flat on your face. This hour, Radiolab dives into stories of great falls.  We jump into a black hole, take a trip over Niagara Falls, upend some myths about falling cats, and plunge into our favorite songs about falling. Support Radiolab by becoming a member today at Radiolab.org/donate.