"Strengthening memory formation for retrieval despite amnesia"

Prof. Dr. rer. soc. Katharine Henke, Professor of Experimental Psychology and Neuropsychology at the Institute of Psychology, University of Bern and Delegate of the Psychology group of the Neuroscience Cluster of the TIC sitem has been awarded SNSF Advanced Grant funding of CHF 1.5 Mio over 5 years.

Due to the demographic change, the prevalence of amnesia associated with old age rises. Amnesia is a deficit of episodic memory, which is believed to result from a loss of episodic learning. Yet, research in mice suggests that new episodic memories continue to be formed in amnesia because physical memory traces of newly formed memories were discovered. These memories harboured the complete information content, although they were not retrievable. The physical memory traces were reactivated optogenetically to the point where the memories became consciously retrievable despite amnesia. Hence, learning had survived in residual intact hippocampal-neocortical tissue besides pathology in amnesic mice. No one has tracked conscious and unconscious episodic memories over time in healthy and amnesic humans because the necessary techniques were missing and because traditional memory theories claim that episodic memories are bound to be consciously accessible or are inexistent. Tracking newly formed individual episodic memory traces with high-resolution functional magnetic resonance imaging in healthy individuals and amnesic patients is now feasible in Bern with the advent of ultra high-field magnetic resonance imaging. I will use ultra high-field functional magnetic resonance imaging to track memory traces underlying individual episodic memories in healthy and amnesic humans. We will track the dynamic transitions of newly formed memories and their underlying physical memory traces as these memories change their representational status und the geometric configuration of their traces over the 24 hours following episodic learning. During this consolidation time, some memories are expected to shift from being consciously accessible to being only unconsciously accessible and to being inaccessible (forgotten). We will demonstrate that the access to stored episodic memories can vary dynamically during the memories’ lifetime in healthy and amnesic individuals. Using electrical brain-stimulation we will reinforce the physical memory traces of newly formed memories in healthy and amnesic individuals to bring unconscious memories to conscious access. To uncover the mechanism of this strengthening of memory traces, we will use ultra high-field magnetic resonance spectroscopy. We expect brain stimulation-induced local glutamatergic increases to result from an enhanced long-term potentiation that results from electrical brain stimulation.

"Metabolic imaging of the brain at ultra high field MRI: feasibility study of spectroscopic methods for exploration of brain metabolism without ionizing radiation"

Principle Investigator: Prof. Johannes Slotboom of the SCAN/TIC, Neuroradiology

University Hospital Bern Switzerland

The aim of this Swiss National Science Foundation project is to study the metabolism in the aging brain. Glucose is the main source of energy if the human brain, and tight regulation of its metabolism is critical for brain physiology. Positron Emission Tomography (PET), which requires an injection of a radioactive substance, is the method most commonly used to study the uptake of glucose in the brain. Deuterium metabolic imaging (DMI) is a novel radiation-free magnetic resonance spectroscopic imaging approach to measure not only the glucose uptake in the brain, but also its metabolic products glutamate and lactate. Beyond glucose, important neurotransmitters (GABA and glutamate) will be studied using a novel approach based on proton magnetic resonance spectroscopic imaging recently developed by our group.

The research will be performed in collaboration of the Support Centre for Advanced Neuroimaging (SCAN), Institute for Diagnostic and Interventional Neuroradiology, Inselspital, Bern; Translational Imaging Center of the Sitem-insel AG; the Department of Diabetes, Endocrinology, Nutritional Medicine and Metabolism, Inselspital, Bern; University Hospital of Old Age Psychiatry and Psychotherapy, University of Bern, and the Department of Radiology, University of Miami School of Medicine, Miami, Florida, U.S.A. and the Radiology & Biomedical Imaging Group of the Yale School of Medicine, New Haven, U.S.A.