Study investigates coding of memories:Serotonin-receptor drives learning in the hippocampus

Neuroscientists explore memory at cellular level

Neuroscientists at the Ruhr University Bochum are investigating the cellular processes involved in memory and learning. In the journal “Hippocampus” they now report on a special serotonin-receptor in the hippocampus, which influences memory encoding and storage.

Serotonin-receptor: marker for learning and memory

When information is processed in the brain, networks of neurons communicate with their synapses – in most cases through biochemical signals. Chemical messengers, so-called neurotransmitters, are sent from one synapse to the next, where they find a fitting receptor – like a matching lock for a key. One of the most important neurotransmitters in the brain is serotonin. Its matching lock, the serotonin-receptor 5-HT4, is of particular interest for neuroscientists, because it is an important marker for learning and memory. If this receptor is supressed in a healthy person, memory performance decreases. Strikingly, patients suffering from Alzheimer’s disease undergo a substantial loss of 5-HT4-receptors. With her team, Prof. Dr. Denise Manahan-Vaughan, head of the department of neurophysiology at the RUB’s medical faculty, has investigated the mechanisms with which the serotonin-receptor regulates learning and memory in the hippocampus.

Receptor influences coding and content of memory

“Our research shows that these particular serotonin-receptors play a pivotal role in shaping the encoding of information in the hippocampus,” explains Prof. Dr. Manahan-Vaughan. The neuroscientist and her team discovered that the receptor favours encoding via long-term potentiation (LTP). During this process, synapse connections in certain areas of the hippocampus are strengthened. In other hippocampal areas the receptor inhibits long-term depression (LTD), which describes the weakening of synaptic connections. “We believe that LTP and LTD are responsible for the encoding of different aspects of a memory. By favouring LTP, the 5-HT4-receptor may influence the content of our memories. If we were to promote or inhibit its activity, we may be able to weaken the consolidation or retrieval of ‘undesirable’ memories,” Prof. Dr. Manahan-Vaughan describes the implications of her findings.