A05-Graphical-Abstract

Cognitive flexibility is the ability to adapt our behavior to a changing environment. It crucially depends on the prefrontal cortex. In our project, we are investigating whether and how the extracellular matrix, which surrounds neurons and determines the biophysical properties of the brain, contributes to the regulation of cognitive flexibility in mice and humans.

Principal Investigators & Co-Workers

CRC 1436 member Constanze Seidenbecher

Prof. Dr. Constanze Seidenbecher

SFB 1436 Mitglied Alexander Dityatev

Prof. Dr. Alexander Dityatev

CRC 1436 member Björn Schott

Dr. Dr. Björn Hendrik Schott

CRC 1436 member Stepan Aleshin

Dr. Stepan Aleshin

CRC 1436 member Margarita Darna

Margarita Darna

Platzhalter SFB 1436 Magdeburg Mitglieder kein Foto

Annabell Ernst

CRC 1436 member Shaobo Jia

Shaobo Jia

picture is coming soon

Hadi Mirzapourdelavar

CRC 1436 member Anni Richter

Dr. Anni Richter

What is the extracellular matrix?

The extracellular matrix (ECM) in the brain consists of a three-dimensional meshwork of macromolecules such as proteoglycans, glycoproteins and hyaluronic acid. These molecules are produced by neurons and glial cells and released into the extracellular space, where they form gel-like macrostructures. Especially around inhibitory parvalbumin-positive cells, so-called perineuronal nets are found as a specialization of the ECM, surrounding and isolating the synapses.

The goals of our project

We aim to investigate in rodents and humans the importance of the ECM in the frontal cortex as a neural resource for cognitive flexibility and the potential transfer of this output from one task to another. We are interested in whether changes in cognitive flexibility during aging are accompanied by changes in the matrix. In particular, we focus on the proteoglycans neurocan and brevican and the complex carbohydrate polysialic acid (PSA). Using young and older healthy humans and mice, we will perform attention tasks and virtual reality maze experiments. We want to find out if improvements in a particular test translate to other behavioral tasks.

Is there a correlation between brain activity and ECM composition?

The molecular composition of the neural ECM changes during maturation and aging of the brain as well as during diseases such as tumors, brain trauma, epilepsy, depression, schizophrenia, or neurodegenerative diseases (Ulbrich et al., 2021). ECM is also modulated depending on the activity state of healthy neuronal networks. For example, activation of dopamine receptors in neurons of the cerebral cortex leads to increased cleavage of ECM proteoglycans by extracellular proteases (Mitlöhner et al., 2020). When the neural ECM is experimentally degraded, the plastic properties of the brain change. For example, the cognitive flexibility of gerbils in an acoustic relearning task increases when the ECM in the auditory cortex is degraded prior to relearning (Happel et al., 2014).

Genetic variability in ECM-encoding genes

Throughout the genome, there are numerous polymorphic sites that make up our genetic variability, to which ECM-encoding genes are also subject. In the NCAN gene, which encodes the proteoglycan neurocan, there is a polymorphism that is considered a genome-wide risk factor for neuropsychiatric disorders such as schizophrenia and bipolar disorder. We have shown that this polymorphism correlates with memory performance and hippocampal activation patterns in a learning task and with gray matter density in the prefrontal cortex in healthy adults (Assmann et al., 2021).

Matrix-deficient mice

The molecular composition of the neural ECM changes during maturation and aging of the brain as well as during diseases such as tumors, brain trauma, epilepsy, depression, schizophrenia, or neurodegenerative diseases (Ulbrich et al., 2021). ECM is also modulated depending on the activity state of healthy neuronal networks. For example, activation of dopamine receptors in neurons of the cerebral cortex leads to increased cleavage of ECM proteoglycans by extracellular proteases (Mitlöhner et al., 2020). When the neural ECM is experimentally degraded, the plastic properties of the brain change. For example, the cognitive flexibility of gerbils in an acoustic relearning task increases when the ECM in the auditory cortex is degraded prior to relearning (Happel et al., 2014).

Matrix variability and cognitive flexibility in humans

Throughout the genome, there are numerous polymorphic sites that make up our genetic variability, to which ECM-encoding genes are also subject. In the NCAN gene, which encodes the proteoglycan neurocan, there is a polymorphism that is considered a genome-wide risk factor for neuropsychiatric disorders such as schizophrenia and bipolar disorder. We have shown that this polymorphism correlates with memory performance and hippocampal activation patterns in a learning task and with gray matter density in the prefrontal cortex in healthy adults (Assmann et al., 2021).

Image of a colored synapse

A glimpse into the future

By working in parallel with mice and humans, we aim to dissect the basic mechanisms of how the micro-environment of neurons in the frontal cortex may affect the capacity for cognitive flexibility. Detection of brain ECM components in serum from patients could provide insight into remodeling processes of the neural ECM in disease conditions associated with impaired cognitive flexibility and stimulate the development of pharmacological tools that help control matrix integrity in the brain.

Publications of the project A05