Brain energy metabolism assessed by genetically encoded sensors for metabolites
Johannes Hirrlinger, Carl-Ludwig-Institute for Physiology, Leipzig, Germany
To provide proper maintenance of brain function appropriate supply of energy is essential. Deficiency of energy delivery as e.g. during stroke or other injuries in the central nervous system will very quickly severely impair brain activity. Also during normal brain function, brain energy metabolism involves complex interactions of different types of brain cells. This metabolic cooperation between different types of brain cells has been a major topic of research in brain energy metabolism for many years focussing mainly on astrocytes and neurons for a long time and only recently also oligodendrocytes have entered the stage. To address the dynamics of metabolites within cells at an appropriate high spatial and temporal resolution we employed genetically encoded fluorescent sensors for metabolites like ATP, glucose, lactate as well as the NAD^+ /NADH-redox stateto follow the concentration of these metabolic parameters in real time in specific cell types both in vitro as well in tissue preparations. For example,using a novel transgenic mouse line expressing a sensor for ATP in neurons and an experimental setup allowing electrophysiology and confocal imaging of excised optic nerves simultaneously, we obtained novel insight into physiological but also pathophysiological axon-glia interactions in this well myelinated fiber tract. Furthermore, we now investigate the dynamics of several parameters of astrocyte metabolism. In summary, genetically encoded sensors for metabolites are powerful tools for an in depth analysis of metabolism and its regulation
Vendredi 31 mars 2017 à 11h30, Salle de conférence.
Cognitive characteristics and neural basis of conscious perception in healthy adults, and clinical applications to non-communicating patients
My goal is to understand the psychological characteristics and the neural mechanisms of conscious perception. My project exploits two dynamic properties that I have contributed to reveal. First, the existence of a discontinuous jump in global cerebral activity during conscious access. Second, the discovery of the « retroperception » phenomenon, which shows that conscious access is flexible in time and is triggered by the reactivation of sensory areas by higher level areas. My project builds upon these discoveries in order to deepen our understanding of the mechanisms of conscious access in healthy adult volunteers, using experimental psychology, fMRI, MEG, EEG and intracranial recordings. The results of this fundamental research will also be the basis for constructing EEG tools for the diagnosis of consciousness in patients in a vegetative of minimally conscious state
Vendredi 31 mars 2017 à 14h30, Salle de réunion LPP.
A green chemistry approach
Estelle Metay, Laboratoire CAtalyse SYnthèse ENvironnement, ICBMS/UMR5246, Villeurbanne, France
Jeudi 20 avril 2017 à 11h, Salle de conférence.
Rescuing deficits in neuronal plasticity after mild TBI
Barclay Morrison III, Columbia University, USA
Traumatic brain injury (TBI) continues to be a major socio-economic problem with about 2 million head injuries in the US annually, the majority being mild in severity.To understand better the mechanisms of TBI, we have developed in vitro models using organotypic brain slice cultures that afford precise control over injury biomechanics.With these models, we have previously developed tolerance criteria to determine safe levels of exposure that could be used to engineer better safety systems to prevent TBI.More recently, we have focused on how different mechanical stimuli (injury) may alter neuronal activity and electrophysiological function within hippocampal neuronal networks and explored therapeutic strategies to reverse pathological changes.Our recent findings suggest that after mild TBI, a disruption of dendritic organization may underlie deficits in long-term potentiation, i.e. the cellular correlates of learning and memory.We have identified therapeutic interventions that rescue LTP with therapeutic windows as long as 6 hours after injury.The long-term goal of our research is to reduce the socio-economic costs of TBI by developing novel treatments and by helping others engineer better protection systems.
Vendredi 28 avril 2017 à 11h30, Salle de conférence.
Probing neural circuits with shaped light
Na Ji (Janelia Research Campus, USA)
To understand computation in the brain, one needs to understand the input-output relationships for neural circuits and the anatomical and functional relationships between individual neurons therein. Optical microscopy has emerged as an ideal tool in this quest, as it is capable of recording the activity of neurons distributed over millimeter dimensions with sub-micron spatial resolution. I will describe how we use concepts in astronomy and optics to develop next-generation microscopy methods for imaging neural circuits at higher resolution, greater depth, and faster speed. By shaping the wavefront of the light, we have achieved synapse-level spatial resolution through the entire depth of primary visual cortex, optimized microendoscopes for imaging deeply buried nuclei, and developed a video-rate (30 Hz) volumetric imaging method. We apply these methods to understanding neural circuits, using the mouse primary visual cortex as our model system.
Vendredi 19 mai 2017 à 11h30, Salle de conférence.