Johannes Gräff

Academic appointments

2013- Tenure Track Assistant Professor, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland, School of Life Sciences, Brain Mind Institute.

2009-2013 Postdoctoral fellow, Massachusetts Institute of Technology (MIT), Cambridge, USA, Picower Institute for Learning and Memory.

2009 Postdoctoral associate, Swiss Federal Institute of Technology (ETHZ), Zürich, Switzerland, Brain Research Institute.

Education

2009 PhD in Neurosciences, Swiss Federal Institute of Technology (ETHZ), Zürich, Switzerland, Department of Biology, Brain Research Institute.

2005 Diploma (M.Sc. equivalent) in Biological Sciences, University of Lausanne, Switzerland, Faculty of Biology and Medicine, Department of Ecology and Evolution.

1998 Matura, Gymnasium Type B, Kantonsschule am Burggraben St. Gallen, Switzerland.

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BIO-480: Neuroscience: from molecular mechanisms to disease

The goal of the course is to guide students through the essential aspects of molecular neuroscience and neurodegenerative diseases. The student will gain the ability to dissect the molecular basis of disease in the nervous system in order to begin to understand and identify therapeutic strategies.

BIO-487: Scientific project design in translational neurosciences

The goal of this course is to instruct the student how fundamental scientific knowledge, acquired through the study of fundamental disciplines, including biochemistry, genetics, pharmacology, physiology, genomics, cell and molecular biology can be applied for drug discovery and development.

BIO-693(10): State of the Art Topics in Neuroscience X

This symposium (Feb 16/17 2023) "What is memory? Molecular, cellular and computational answers" brings together leading experts in the field of learning and memory who will share their latest findings on the eternal question- What are memories made of? A broad range of approaches will be covered.

Epigenetics

In biology, epigenetics is the study of stable changes in cell function (known as marks) that do not involve alterations in the DNA sequence. The Greek prefix epi- (ἐπι- "over, outside of, around")

Memory

Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future ac

Brain

A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as

Face your fears: attenuating remote fear memories by reconsolidation-updating

Johannes Gräff, Bianca Ambrogina Silva

Traumatic events generate some of the most enduring memories, yet little is known about how long-lasting fear memories can be attenuated. In this review, we collect the surprisingly sparse evidence on remote fear memory attenuation from both animal and human research. What is becoming apparent is twofold: although remote fear memories are more resistant to change compared with recent ones, they can nevertheless be attenuated when interventions are targeted toward the period of memory malleability instigated by memory recall, the reconsolidation window. We describe the physiological mechanisms underlying remote reconsolidation-updating approaches and highlight how they can be enhanced through interventions promoting synaptic plasticity. By capitalizing on an intrinsi-cally relevant phase of memory, reconsolidation-updating harbors the potential to permanently alter remote fear memories.

ELSEVIER SCIENCE LONDON2023

Prefrontal engrams of long-term fear memory perpetuate pain perception

Johannes Gräff, Yechao Han, Sheng Liu

A painful episode can lead to a life-long increase in an individual's experience of pain. Fearful anticipation of imminent pain could play a role in this phenomenon, but the neurobiological underpinnings are unclear because fear can both suppress and enhance pain. Here, we show in mice that long-term associative fear memory stored in neuronal engrams in the prefrontal cortex determines whether a painful episode shapes pain experience later in life. Furthermore, under conditions of inflammatory and neuropathic pain, prefrontal fear engrams expand to encompass neurons representing nociception and tactile sensation, leading to pronounced changes in prefrontal connectivity to fear-relevant brain areas. Conversely, silencing prefrontal fear engrams reverses chronically established hyperalgesia and allodynia. These results reveal that a discrete subset of prefrontal cortex neurons can account for the debilitating comorbidity of fear and chronic pain and show that attenuating the fear memory of pain can alleviate chronic pain itself. Can erasing bad memories relieve pain? Stegemann et al. uncover the cellular basis of fear-pain interactions, reporting that fear potentiates pain via memories encoded in prefrontal engrams. Blocking these memory traces reduces chronic pain in mice.

NATURE PORTFOLIO2023

Brain-wide screen of prelimbic cortex inputs reveals a functional shift during early fear memory consolidation

Lucie Pauline Dixsaut, Johannes Gräff

Memory formation and storage rely on multiple interconnected brain areas, the contribution of which varies during memory consolidation. The medial prefrontal cortex, in particular the prelimbic cortex (PL), was traditionally found to be involved in remote memory storage, but recent evidence points toward its implication in early consolidation as well. Nevertheless, the inputs to the PL governing these dynamics remain unknown. Here, we first performed a brain-wide, rabies-based retrograde tracing screen of PL engram cells activated during contextual fear memory formation in male mice to identify relevant PL input regions. Next, we assessed the specific activity pattern of these inputs across different phases of memory consolidation, from fear memory encoding to recent and remote memory recall. Using projection-specific chemogenetic inhibition, we then tested their functional role in memory consolidation, which revealed a hitherto unknown contribution of claustrum to PL inputs at encoding, and of insular cortex to PL inputs at recent memory recall. Both of these inputs further impacted how PL engram cells were reactivated at memory recall, testifying to their relevance for establishing a memory trace in the PL. Collectively, these data identify a spatiotemporal shift in PL inputs important for early memory consolidation, and thereby help to refine the working model of memory formation.

2022