Past events

Drosophila melanogaster flies show complex behaviors like associative learning. Combining the available genetic tools with behavioral measures allows us to study the specific neuronal circuits of learning and memory. Using olfactory conditioning, I directly compared the neuronal circuit of memories with different punishment paradigms: the widely used electric-shock and the newly established elevated temperature. I identified the neural pathway selectively required for olfactory-temperature conditioning, from the sensory input to the central neurons signaling reinforcement. I found that temperature and electric-shock punishments—despite being perceived by distinct sensors—eventually converge to the same neuronal network: the dopamine pathway. Thus the role of dopamine is general—attaching a motivational value to an environmental stimulus. This finding is especially significant in context of recent findings in mammalian systems, namely that in addition to their well-established role in signaling positive reinforcement, dopaminergic populations in the mammalian brain were also shown to represent aversive reinforcement.

Summary: Gyorgy Buzsaki aims at understanding how neuronal circuitries of the brain support its cognitive capacities, with a primary interest in brain oscillations, synchronization and memory. His major goal is to provide rational, mechanistic explanations of cognitive functions at a descriptive level. Over the past 35 years, Buzsaki has led the way in analyzing the functional properties of cortical neurons acting within their natural networks. He pioneered the experimental exploration of how coordinated, rhythmic neuronal activity serves physiological functions in the cerebral cortex, and in particular, how information is exchanged between the hippocampus and neocortex. For this aim, Buzsaki's lab has established some of the most difficult approaches necessary to solve these problems. His work includes innovative techniques to monitor neural activity and brain oscillation in behaving rodents from the cellular level to whole network activation. In addition to his numerous publications and reviews, Gyorgy Buzsaki is the author of the book "Rhythms of the Brain", which discusses mechanisms and functions of neuronal synchronization. He explains the field of brain oscillations, and how oscillatory timing is the brain’s fundamental organizer of neuronal information. Among many other distinguished awards, he is the recipient of the 2011 European brain prize. http://www.buzsakilab.com/

The etiology of schizophrenia is complex and largely unknown, but consistent findings report a strong genetic component. While several potential schizophrenia-susceptibility genes have been identified, effect sizes are very small and replication is inconsistent, likely because of the complexity of human polymorphisms, genetic and clinical heterogeneity and the potential uncontrollable impact of gene-gene and gene-environment interactions. In this context, mutant mice bearing targeted mutations of schizophrenia-susceptibility genes are unique tools to elucidate the neurobiological basis of this devastating disorder. Using COMT*dysbindin-1 double mutant mice, we investigated the COMT*dysbindin-1 gene-gene interacting effects in the expression of rodents’ correlates of schizophrenia-relevant behavioral abnormalities. A major focus of our work is centered on how to dissect higher order cognitive functions in mice with high translational validity to human studies. In particular, in contrast to single genetic modifications, the combined decreased activity of both COMT and dysbindin-1 produced marked working memory, recency memory and attentional set-shifting deficits, and amphetamine supersensitivity; all abnormalities ascribed as mice’ correlates of schizophrenia-like symptoms. Based on this, we found evidence of the same non-linear genetic interaction in prefrontal cortical function in humans. Finally, to disentangle how COMT*dysbindin-1 interaction might converge in dopaminergic signaling, we measured in these double mutant mice dopamine levels in the PFC and dorsal striatum by in vivo microdialysis. Interestingly, concomitant COMT*dysbindin-1 reduction diminished dopamine levels in PFC and striatum, while amphetamine-evoked dopamine increase was attenuated in the PFC but exacerbated in the striatum. These findings illustrate a clinically relevant experimental animal model based on a predicted epistatic interaction of two schizophrenia-susceptibility genes and unravel interesting genetic mechanisms in the etiology of this mental illness.

I will discuss techniques that allow us to perform cellular and subcellular resolution imaging of neuronal activity in mice navigating in virtual reality environments and recent results from imaging place cells and grid cells. I will describe activity patterns that we have observed in hippocampal place cell dendrites and the implications for how associative Hebbian learning may take place during behavior. I will also describe the functional micro-organization of grid cells in the medial entorhinal cortex and what the organization might tell us about the circuits that generate grid cell firing patterns.

I will discuss techniques that allow us to perform cellular and subcellular resolution imaging of neuronal activity in mice navigating in virtual reality environments and recent results from imaging place cells and grid cells. I will describe activity patterns that we have observed in hippocampal place cell dendrites and the implications for how associative Hebbian learning may take place during behavior. I will also describe the functional micro-organization of grid cells in the medial entorhinal cortex and what the organization might tell us about the circuits that generate grid cell firing patterns.

תקציר: התאבדות היא תופעה אנושית שחוצה תרבויות ותקופות הנחקרת במסגרת דיסציפלינות רבות ומגוונות. למרות המאמץ הרב-תחומי הענף לפענח את התופעה, היא נותרת במובנים רבים חידתית ונטולת הסבר מְספק. העיסוק בתופעת ההתאבדות נפוץ מאוד בעולם היצירה הספרותית, כביטוי נוסף לניסיון הבלתי נלאה לפענח ולמשמע את החריגה המתגלמת בהתאבדות מסדריו הנורמטיביים של הקיום האנושי. אקט ההתאבדות הוא כשלעצמו אתר של עימות בין כוחות סותרים רבי עוצמה, דהיינו דחף החיים אל מול יצר המוות, והוא עשוי להיקרא גם כבעל משמעויות עמוקות בכל הנוגע ליצר החיים המתבטא ביצירה האמנותית בכלל ובכתיבה בפרט. קריאת מעשה ההתאבדות הספרותית עשויה לשפוך אור על אתרים "אפלים" בנפש האדם ועל האופן שבו הספרות עשויה להעניק להם מילים ולפענח אותם. מחקרי מתחקה אחר ייצוגים של התאבדות במבחר יצירות בפרוזה מן הספרות העברית המודרנית תוך הפניית מבט סינכרוני ודיאכרוני אל ייצוגיה של התופעה בהקשרים הפסיכולוגיים, החברתיים והפוליטיים, וכן אל תפקידה התמטי והאסתטי בטקסט הספרותי. מטרתו של המחקר היא לבחון את מעשה ההתאבדות כפי שהוא מיוצג בספרות כנקודת מפגש עוצמתית ומיוחדת במינה בין כוחות מנוגדים חברתיים, פוליטיים ופסיכולוגיים. בהקשר הספציפי של הספרות העברית, שמתוכה נבחר קורפוס המחקר, ושעניינה המתמשך הינו התהליכים ההיסטוריים שעברה תנועת התחייה הלאומית מסוף המאה התשע-עשרה ועד היום, מצטרף דיון זה אל הניסיון המחקרי-תיאורטי הקיים לשרטט את יחסי הגומלין המשתנים בין הקולקטיבי לאינדיווידואלי בתרבות העברית המתחדשת.

Alexander Borst aims at understanding the foundations of information processing at the level of small neural circuits, focusing on the visual course control system in Drosophila. Borst’s lab uses a comprehensive approach , combining electron microscopy-aided anatomical reconstructions of the circuit, physiological characterization by both imaging and whole cell patch recordings, genetic circuit manipulation in behaving flies, computational modeling and last but not least, engineering of fly-inspired robots that implement the theoretical principles and test their functionality. Borst’s outstanding research has yielded a very precise and detailed description of the circuit at the single cell resolution as well as a thorough understanding of the computations it performs. Several of his major scientific contributions include the discovery that the direction of visually perceived motion is calculated following the Reichardt Model (Single & Borst, Science 1998), the separation of visual information in the fly brain into ON- and OFF-channels, similar to bipolar cells in the retina of vertebrate eyes (Jösch, Schnell, Raghu, Reiff & Borst, Nature 2010) and the existence of four types of neurons in each channel, tuned to one of the four cardinal directions (right, left, up, down) that project into four separate neuronal layers based on their preferred direction (Maisak et al, Nature 2013). https://www.neuro.mpg.de/borst