Hyperaktivität im Hirn

With age, the ability to orient in spatial environments tends to decline. Researchers at the DZNE in Magdeburg see a possible cause for this phenomenon in an overactivity of the hippocampus - this brain region is generally regarded as the control center of memory. They report on this in the „Journal of Neuroscience“.

Image shows a screenshot of the virtual environment of the study. — The image shows the pointing task participants had to perform after touring a photo-realistic virtual town in multiple learning blocks. They had to estimate the position of certain target landmarks in the town by moving the crosshair, while neural activity was measured, using fMRI. Source: DZNE / Nadine Diersch

For their study, the researchers directed young and older adults through an unknown virtual environment - a computer-generated representation of a typical German city center - while monitoring brain activity using functional magnetic resonance imaging (fMRI). The study group comprised more than 50 women and men between the ages of 20 and 75.

“With age, the ability to learn the spatial layout of new environments deteriorates. This everyday experience has been documented by previous studies and we also see this in our data. On average, young people did better than older individuals in the orientation testing. However, there were also older study participants who performed quite well and learned as quickly as the younger adults. Actually, there was a wide range in the performance of the older participants,” said Dr. Nadine Diersch, first author of the current publication.

Differences in Brain Activity

So far, however, little is known about why orientation ability declines with age, the neuroscientist explained. “In our study, we have now found activity differences in regions of the brain’s navigation network, such as the hippocampus, between young and older participants. In the older participants, activity in the hippocampus tended to be higher than in the young volunteers during crucial phases of the experiment. We see this hyperactivity as a possible cause for the differences in orientation ability. The young brain seems to process information differently than the old brain in this situation.”

Neuronal Orchestra

In future studies, the researchers aim to investigate what triggers this increased activity. They already have a hypothesis, Diersch explained: “In the brain, there are various players who interact in a complex way. It’s similar to a large orchestra. On the one hand, there is the interaction between different brain regions. On the other hand, there are neuronal circuits at the cellular level that amplify neural activity and others that attenuate this activity. Our current results indicate that the so-called inhibitory, that is attenuating circuits of the hippocampus are impaired due to ageing. Hence, hyperactivity occurs. Thus, our study is one of the first to link age-related differences in orientation skills to specific physiological changes.”

Original publication

Increased hippocampal excitability and altered learning dynamics mediate cognitive mapping deficits in human aging.
Nadine Diersch et al.
The Journal of Neuroscience (2021).
DOI: 10.1523/JNEUROSCI.0528-20.2021

March 2021