Summary in seconds: schizophrenia is a complex mental disorder with an uncertain cause, but several risk factors are involved. Heredity plays a significant role in its development. Recent research highlights the potential of EEG microstates for early screening and detection of schizophrenia.
Schizophrenia1 is a severe mental disorder marked by abnormal interpretations of reality. It typically emerges between late teens and early 30s, with males experiencing the peak incidence earlier than females. The exact cause of schizophrenia remains unknown, but certain factors have been identified to increase the likelihood of developing the disease. Heredity2 is considered the most significant risk factor associated with schizophrenia. Scientists believe that a combination of common and rare genetic variants3, rather than a single genetic variant, contributes to deviations in the developing brain, leading to the onset of schizophrenia.
Currently, no specific diagnostic test exists for schizophrenia, and the diagnosis4 process often requires months of gathering information about a patient’s history and behavior. To identify potential schizophrenia patients earlier, researchers are exploring measurable internal traits that are present in both individuals with schizophrenia and their family members. These quantifiable traits, known as endophenotypes5, establish a connection between the disorder’s symptoms and the underlying genetic risk factors.
In this study6, scientists utilized resting-state electroencephalography7 (EEG) to examine the brains of individuals with schizophrenia, their unaffected siblings, and healthy individuals without a family history of the disease. The researchers focused on identifying specific patterns of neuronal activity known as “EEG microstates8,” which are fundamental to cognition and emotion. These microstates last between 60 and 120 milliseconds and occur when particular brain areas activate simultaneously.
Previous research had already established that individuals with schizophrenia exhibit abnormal EEG microstates. However, this study is groundbreaking as it demonstrates that unaffected siblings also share the same abnormalities in these brain patterns.
In the present study, researchers discovered that a particular microstate type, referred to as class C, exhibited higher frequency and longer durations in individuals with schizophrenia and their siblings compared to healthy individuals. Conversely, microstate class D, another brain activity pattern, occurred less frequently and for shorter durations in those with schizophrenia and their siblings than in healthy individuals.
Interestingly, individuals who had recently experienced their first episode of psychosis displayed the same abnormal brain activity patterns as those who had been experiencing schizophrenia for an extended period. This indicates that these microstate abnormalities emerge right at the onset of the disease.
Additionally, the recent study uncovered a third type of microstate, known as class B, which displayed higher frequency and longer durations in siblings compared to individuals with schizophrenia. This class B microstate might offer an explanation as to why healthy siblings, despite having the same brain ‘signature’ as those with schizophrenia, do not exhibit schizophrenia-related behaviors.
Researchers speculate that the class B microstate could serve as a protective mechanism, preventing the imbalance in microstates class C and D from causing functional issues. It may play a role in safeguarding against the development of schizophrenia-related symptoms in otherwise unaffected siblings.
These brain ‘signatures,’ characterized by alterations in EEG microstates, hold promise as a component of early screening for schizophrenia. They have the potential to identify individuals who are susceptible to the disorder even before the onset of any clinical symptoms.
1. Schizophrenia: the disease may appear suddenly or after a slow and gradual development over a period of time. Main symptoms are delusional ideations, hallucinations, and disorganized thinking. Other symptoms include social withdrawal, decreased emotional expression, and apathy.
2. Heredity: the incidence of having the disease among the general population is about 0.3% to 0.7%, however, more than 40% of identical twins with schizophrenia also develop it. If one parent is affected, the risk is about 13%, and if both are affected, the risk is close to 50%.
3. Rare genetic variants: scientists think that the disorder stems from many different DNA mutations, duplications, and deletions. In fact, genetic studies identified dozens of genes associated with schizophrenia.
4. Diagnosis of schizophrenia: relied not only on observing patient’s behavior but also on a comprehensive history that includes the person’s reported experiences, and reports of others familiar with the person. To diagnose someone with schizophrenia, patient’s confirmed symptoms and functional impairment must be present for either six months according to (DSM-5) or one month according to (ICD-11).
5. Endophenotype: is a term used in genetic epidemiology to separate behavioral symptoms into stable phenotypes with a clear genetic connection.
6. “EEG microstates are a candidate endophenotype for schizophrenia” by Janir Ramos da Cruz, Ophélie Favrod, Maya Roinishvili, Eka Chkonia, Andreas Brand, Christine Mohr, Patrícia Figueiredo & Michael H. Herzog. Nature Communications. (neurosciencenews.com – July 13, 2020)
7. Electroencephalography: is a non-invasive method to record the electrical activity on the scalp which represent the macroscopic activity of the surface layer of the brain.
8. EEG microstates: are transient, patterned, quasi-stable states or patterns of an electroencephalogram. These tend to last anywhere from milliseconds to seconds and are hypothesized to be the most basic instantiations of human neurological tasks, and are thus nicknamed “the atoms of thought”.