If your hearing deteriorates in old age, the risk of dementia and cognitive decline increases. So far, it hasn’t been clear why. A team of neuroscientists at Ruhr-Universität Bochum (RUB) in Germany examined what happens in the brain when hearing gradually deteriorates: key areas of the brain are reorganized, and this affects memory. The results are published online in the journal Cerebral Cortex and in an article on the University’s website.
Daniela Beckmann, Mirko Feldmann, Olena Shchyglo, and Professor Denise Manahan-Vaughan from the Department of Neurophysiology of the Medical Faculty worked together for the study.
When Sensory Perception Fades
The researchers studied the brain of mice that exhibit hereditary hearing loss, similar to age-related hearing loss in humans. The scientists analyzed the density of neurotransmitter receptors in the brain that are crucial for memory formation. They also researched the extent to which information storage in the brain’s most important memory organ, the hippocampus, was affected.
Adaptability of the Brain Suffers
Memory is enabled by a process called synaptic plasticity. In the hippocampus, synaptic plasticity was chronically impaired by progressive hearing loss. The distribution and density of neurotransmitter receptors in sensory and memory regions of the brain also changed constantly. The stronger the hearing impairment, the poorer were both synaptic plasticity and memory ability.
“Our results provide new insights into the putative cause of the relationship between cognitive decline and age-related hearing loss in humans,” said Manahan-Vaughan. “We believe that the constant changes in neurotransmitter receptor expression caused by progressive hearing loss create shifting sands at the level of sensory information processing that prevent the hippocampus from working effectively,” she adds.
The study was funded by the Collaborative Research Center (SFB) 874 of the German Research Foundation. SFB 874 “Integration and Representation of Sensory Processes” has existed at RUB since 2010. The researchers investigate how sensory signals generate neuronal maps, resulting in complex behaviour and memory formation. Beckmann and Feldmann have also completed the medical students’ program of the SFB 874 and the International Graduate School of Neuroscience.
Original Paper: Beckmann D, Feldmann M, Shchyglo O, Manahan-Vaughan D. Hippocampal synaptic plasticity, spatial memory, and neurotransmitter receptor expression are profoundly altered by gradual loss of hearing ability. Cerebral Cortex. 2020;00:1-16.
Source: RUB, Cerebral Cortex