From Single Ion Channels to Cortical Networks
Prof. Bert Sakmann
DATE: 30th August 2019
TIME: 17:15- 18:30 pm
LOCATION: Rigoni Stern Institute, Asiago
Initially patch pipettes were designed to record elementary current events from muscle and neuron membrane (Sakmann, 1992). Recording configurations designated as whole-cell and cell-attached recording proved to be useful to examine signaling within and between nerve cells embedded in their (almost) natural environment. In this Paton Lecture I will summarize work on electrical signaling within a neuron, involving communication between its dendritic compartments, soma and nerve terminals via forward and backward propagating dendritic action potentials. The newly discovered dendritic excitability endows neurons with the capacity for coincidence detection of spatially separated subthreshold inputs occurring during a time window of tens of milliseconds and the occurrence of coincidences is broadcasted in the cell by the initiation of bursts of action potentials (AP bursts). The occurrence of bursts critically impacts signaling between neurons. It revealed target cell specific transmitter release mechanisms in different terminals of the same neuron and the induction of synaptic plasticity mechanisms when AP bursts occur both presynaptically in terminals and postsynaptically in dendrites, within a short time window.
A fundamental question that arises from these findings is: “What are possible functions of active dendritic excitability with respect to network dynamics in the intact cortex of behaving animals?” For this purpose, I will highlight in this review the anatomical and functional architectures of an averaged cortical column in the vibrissal field of somatosensory cortex (vS1), followed by a summary of the role of layer 5 thick tufted pyramids cells (L5tt) in the functional architecture of these very same cortical columns. Synaptic and unit responses of these major cortical output neurons to a whisker deflection are compared with responses of afferent neurons in primary somatosensory thalamus and of one of their efferent targets, secondary somatosensory thalamus (POm). Coincidence detection mechanisms appear to be implemented in vivo as judged from the occurrence of AP bursts. Three dimensional reconstructions of anatomical inputs that could provide separated dendritic inputs suggest that inputs from several combinations of thalamo-cortical projections and intracolumar connections could generate AP bursts. Finally, recordings from the columns ́ target cells reveal the importance of AP burst patterns for signal transfer to these cells. The observations lead to the hypothesis that in vS1 cortex the sensory afferent rate code is transformed, at least partially, to an interval code that broadcasts sensory stimuli to different targets of L5tt cells. In addition, the occurrence of pre- and postsynaptic AP bursts may, on the long run, alter sensory representation in cortex.
Bert Sakmann (born 12 June 1942) is a German cell physiologist. He shared the Nobel Prize in Physiology or Medicine with Erwin Neher in 1991 for their work on “the function of single ion channels in cells,” and invention of the patch clamp. Bert Sakmann was Professor at Heidelberg University and is an Emeritus Scientific Member of the Max Planck Institute for Medical Research in Heidelberg, Germany. Since 2008 he leads an emeritus research group at the Max Planck Institute of Neurobiology.
Life and career
Sakmann was born in Stuttgart, the son of Annemarie (née Schaefer), a physical therapist, and Bertold Sakmann, a theater director. Sakmann enrolled in Volksschule in Lindau, and completed the Wagenburg gymnasium in Stuttgartin 1961. He studied medicine from 1967 onwards in Tübingen, Freiburg, Berlin, Paris and Munich. After completing his medical exams at Ludwig-Maximilians University in Munich, he became a medical assistant in 1968 at Munich University, while also working as a scientific assistant (Wissenschaftlicher Assistant) at Munich’s Max-Planck-Institut für Psychiatrie, in the Neurophysiology Department under Otto Detlev Creutzfeldt. In 1971 he moved to University College London, where he worked in the Department of Biophysics under Bernard Katz. In 1974, he completed his medical dissertation, under the title Elektrophysiologie der neuralen Helladaptation in der Katzenretina (Electrophysiology of Neural Light Adaption in the Cat Retina) in the Medical Faculty of Göttingen University.
Afterwards (still in 1974), Sakmann returned to the lab of Otto Creutzfeldt, who had meanwhile moved to the Max Planck Institute for Biophysical Chemistry in Göttingen. Sakmann joined the membrane biology group in 1979.
On 2 June 2009, Dr. Peter Gruss, the president of the Max Planck Society, announced that Sakmann would serve as the scientific director of the Max Planck Florida Institute, the organization’s biomedical research facility at Florida Atlantic University in Jupiter, Florida.
Sakmann is the founder of the Bert-Sakmann-Stiftung.
Awards and honors
In 1986, he and Erwin Neher were awarded the Louisa Gross Horwitz Prize from Columbia University. In 1987, he received the Gottfried Wilhelm Leibniz Prize of the Deutsche Forschungsgemeinschaft, which is the highest honour awarded in German research. In 1991, he received the Harvey Prize and the Nobel prize for Physiology or Medicine along with Neher, with whom he had worked in Göttingen. He was elected a Foreign Member of the Royal Society (ForMemRS) in 1994.
Will be provided during the lecture