CBBS Best Paper of The Year 2018

Happy prize winners: Volkmar Leßmann, Susanne Meis, Thomas Munsch, and Johannes Achtzehn from the Wolbers laboratory (center, from left to right) with CBBS speakers Eckart Gundelfinger (left), Daniela Dieterich (right), and Toemme Noesselt (second from right), and rector Jens Strackeljan (second from left). Photo: LIN / Blumenstein

Orientation in Old Age 

Spatial orientation and navigation are among the most complex abilities of the human mind. However, these skills often deteriorate as we grow older, which can severely compromise independence and quality of life. Given that so-called grid cells in entorhinal cortex are a central component of the navigation circuit in the human brain, the current study was the first to investigate potential grid cell changes in old age. With an innovative combination of functional MRI and virtual reality, older participants were found to exhibit a much lower stability of the grid cell system compared to younger adults. In addition, participants with the most severe instability also showed substantial deficits in a behavioural test of spatial navigation. As a consequence, such changes in the grid cell system could be responsible for the decline of navigational abilities that is common among older people. Moreover, neurodegenerative changes in entorhinal cortex and deficits with spatial orientation are a hallmark of Alzheimer’s disease. The methods for studying and analysing grid cell integrity as developed in the current study could hence help to improve assessment and early detection of dementia.

Happiness Hormone in Fear Learning 

Imprinting of threatening experiences in fear memory is an essential strategy to survive. The neurotransmitter Dopamine, formerly only known as mediator of reward and motivation, also plays an essential role in the formation of fear memory. Mice were conditioned to associate a tone with a mild footshock. By means of neuroanatomical and imaging methods, a new group of dopaminergic neurons in the midbrain, the periaqueductal gray (vPAG), was identified, which showed increased activity during fear learning. Increased activity of these dopaminergic neurons caused the release of Dopamine in the amygdala, a central region for emotional learning in mammals, where it facilitated the effective formation of the fear memory trace. Transient inactivation of dopaminergic vPAG neurons during conditioning impeded the storage of the tone in fear memory, whereas stimulation of these neurons caused new learning. The present work identifies a so far unknown, reciprocally connected network of dopaminergic vPAG and amygdala neurons, which is essential for the emotional assessment of aversive environmental stimuli. It enables the brain to filter out environmental stimuli relevant for fear memory formation. A similar neuronal network is involved in pain sensation and memory formation in humans. It seems therefore feasible to speculate about the dysfunction of dopaminergic neurons in mental disorders such as posttraumatic stress disorders (PTSD). Future investigations will show whether Dopamine-related drugs can be used for treatment of PTSD patients.