Press releases – October 2019

FRANKFURT. The interconnections and communication between different regions of the human brain influence our behaviour in many ways. This is also true for individual differences in higher cognitive abilities. The brains of more intelligent individuals are characterised by temporally more stable interactions in neural networks. This is the result of a recent study conducted by Dr Kirsten Hilger and Professor Christian Fiebach from the Department of Psychology and Brain Imaging Center of Goethe University Frankfurt in collaboration with Dr Makoto Fukushima and Professor Olaf Sporns from Indiana University Bloomington, USA. The study was published online in the scientific journal 'Human Brain Mapping' on 6th October. 

Intelligence and its neurobiological basis 
Various theories have been proposed to explain the differences in different individuals' cognitive abilities, including neurobiological models. For instance, it has been proposed that more intelligent individuals make stronger use of certain brain areas, that their brains generally operate more efficiently, or that certain brain systems are better wired in smarter people. Only recently have methodological advances made it possible to also investigate the temporal dynamics of human brain networks, using functional magnetic resonance imaging (fMRI). An international team of researchers from Goethe University and Indiana University Bloomington analysed fMRI scans of 281 participants to investigate how dynamic network characteristics of the human brain relate to general intelligence. 

Stability of brain networks as general advantage
The human brain has a modular organisation - it can be subdivided into different networks that serve different functions such as vision, hearing, or the control of voluntary behaviour. In their current study, Kirsten Hilger and colleagues investigated whether this modular organisation of the human brain changes over time, and whether or not these changes relate to individual differences in the scores that study participants achieved in an intelligence test. The results of the study show that the modular brain network organisation of more intelligent persons exhibited less fluctuations during the fMRI measurement session. This increased stability of brain network organisation was primarily found in brain systems that are important for the control of attention. 

Attention plays a key role
“The study of the temporal dynamics of human brain networks using fMRI is a relatively new field of research" says Hilger. She speculates: “The temporally more stable network organisation in more intelligent individuals could be a protective mechanism of the brain against falling into maladaptive network states in which major networks disconnect and communication may be hampered." She also stresses that it remains an open question how exactly these network properties influence cognitive ability: “At present, we do not know whether the temporally more stable brain connections are a source or a consequence of higher intelligence. However, our results suggest that processes of controlled attention – that is, the ability to stay focused and to concentrate on a task – may play an important role for general intelligence." 

Publication: Hilger, K., Fukushima, M., Sporns, O., & Fiebach, C. F. (2019). Temporal Stability of Functional Brain Modules Associated with Human Intelligence. Human Brain Mapping. (DOI: https://doi.org/10.1002/hbm.24807) 

Further information: Dr Kirsten Hilger, Department of Psychology, Theodor-W.-Adorno-Platz 6, D-60323 Frankfurt, Germany. hilger@psych.uni-frankfurt.de, Tel. +49 (0)160-3391686; see also the webpage of the Laboratory for Cognitive Neuroscience at Goethe University: http://fiebachlab.org

FRANKFURT. For his outstanding contributions in the field of astrophysics, Luciano Rezzolla, Professor for Astrophysics at Goethe University, will be appointed Andrews Professor of Astronomy at Trinity College in Dublin. Previously combined with the leadership of the Irish Dunsink Observatory, today the title is a prestigious honorary chair. The appointment of Luciano Rezzolla represents the first time the professorship will be given to a non-Irish person. 

“The Andrews Professor for Astronomy is a tremendous recognition of the excellence achieved in astrophysics research at Goethe University," says Luciano Rezzolla. “It's simultaneously a recognition of a paradigm change that has also taken place in Frankfurt, in which theoretical astrophysics and theoretical physics are being combined more and more in the quest for a deeper understanding of the universe. I am very happy that together with my team and many other colleagues in Frankfurt and Dublin, I have been able to use this potential to continue improving our research. 

“This title is a great honour, both for Luciano Rezzolla and for his team at the Institute for Theoretical Physics", says Simone Fulda, Vice President for Research and Academic Infrastructure at Goethe University. “The award illustrates the high value placed on physics within Goethe University research. We are quite proud of this and extend Luciano Rezzolla our warmest congratulations." 

The Andrews Professor for Astrophysics was established in 1774. The politician and provost of Trinity College, Francis Andrews, bequeathed £3,000 to build a new observatory in Dunsink. The first Andrews Professor was the mathematician and astronomer Henry Ussher, who was appointed in 1783. Between 1791 and 1921 the holder of the chair was also the “Royal Astronomer of Ireland". After remaining vacant between 1921 and 1984, the position was subsequently re-established as an honorary chair. With this appointment, Rezzolla follows in the footsteps of Sir William Rowan Hamilton, who held the position from 1827 to 1865, and after whom Hamiltonian mechanics was named. 

In addition to this honour, Rezzolla gained worldwide media attention in April of this year. As principal investigator of the “Black Hole Cam Project" (BHC Project), he and his colleagues made the observation of the hot plasma ring surrounding the black hole in the centre of the Galaxy M87 visible for the first time. The National Science Foundation, the US government agency for research funding, recognized the first image of black hole with a new prize: in 2019, the Diamond Achievement Award was given to the international team of the Event Horizon Telescope collaboration, of which Professor Rezzolla is also a member. Rezzolla and his team at the Institute for Theoretical Physics were also awarded the Frankfurt Physics Science Prize. 

Publication: https://ipfs.io/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjQkDDP1mXWo6uco/wiki/Andrews_Professorship_of_Astronomy.html

An image can be downloaded here: http://www.uni-frankfurt.de/82568015
Credit: Jürgen Lecher, Goethe University 

Further information: Professor Luciano Rezzolla, Institute for Theoretical Physics, Faculty of Physics, Riedberg Campus, Telephone: +49 69 798 47871, rezzolla@th.physik.uni-frankfurt.de; https://astro.uni-frankfurt.de/rezzolla/

FRANKFURT. Albert Einstein received the Nobel Prize for explaining the photoelectric effect: in its most intuitive form, a single atom is irradiated with light. According to Einstein, light consists of particles (photons) that transfer only quantised energy to the electron of the atom. If the photon's energy is sufficient, it knocks the electrons out of the atom. But what happens to the photon's momentum in this process? Physicists at Goethe University are now able to answer this question. To do so, they developed and constructed and new spectrometer with previously unattainable resolution. 

Doctoral student Alexander Hartung became a father twice during the construction of the apparatus. The device, which is three meters long and 2.5 meters high, contains approximately as many parts as an automobile. It sits in the experiment hall of the Physics building on Riedberg Campus, surrounded by an opaque, black tent inside which is an extremely high performing laser. Its photons collide with individual argon atoms in the apparatus, and thereby remove one electron from each of the atoms. The momentum of these electrons at the time of their appearance is measured with extreme precision in a long tube of the apparatus. 

The device is a further development of the COLTRIMS principle that was invented in Frankfurt and has meanwhile spread across the world: it consists of ionising individual atoms, or breaking up molecules, and then precisely determining the momentum of the particles. However, the transfer of the photon momentum to electrons predicted by theoretic calculations is so tiny that it was previously not possible to measure it. And this is why Hartung built the “super COLTRIMS". 

When numerous photons from a laser pulse bombard an argon atom, they ionise it. Breaking up the atom partially consumes the photon's energy. The remaining energy is transferred to the released electron. The question of which reaction partner (electron or atom nucleus) conserves the momentum of the photon has occupied physicists for over 30 years. “The simplest idea is this: as long as the electron is attached to the nucleus, the momentum is transferred to the heavier particle, i.e., the atom nucleus. As soon as it breaks free, the photon momentum is transferred to the electron," explains Hartung's supervisor, Professor Reinhard Dörner from the Institute for Nuclear Physics. This would be analogous to wind transferring its momentum to the sail of a boat. As long as the sail is firmly attached, the wind's momentum propels the boat forward. The instant the ropes tear, however, the wind's momentum is transferred to the sail alone. 

However, the answer that Alexander Hartung discovered through his experiment is – as is typical for quantum mechanics - more surprising. The electron not only receives the expected momentum, but additionally one third of the photon momentum that actually should have gone to the atom nucleus. The sail of the boat therefore “knows" of the impending accident before the cords tear and steals a bit of the boat's momentum. To explain the result more precisely, 

Hartung uses the concept of light as an electro-magnetic wave: “We know that the electrons tunnel through a small energy barrier. In doing so, they are pulled away from the nucleus by the strong electric field of the laser, while the magnetic field transfers this additional momentum to the electrons." Hartung used a clever measuring setup for the experiment. To ensure that the small additional momentum of the electron was not caused accidentally by an asymmetry in the apparatus, he had the laser pulse hit the gas from two sides: either from the right or the left, and then from both directions simultaneously, which was the biggest challenge for the measuring technique. This new method of precision measurement promises deeper understanding of the previously unexplored role of the magnetic components of laser light in atomic physics.

Images may be downloaded here: http://www.uni-frankfurt.de/82277680
Image 1: Photo of the COLTRIMS reaction microscope built by Alexander Hartung as part of his doctoral research in the experiment hall of the Faculty of Physics. Credit: Alexander Hartung
Image 2:Technical drawing of the newly constructed COLTRIMS reaction microscope. The drawing shows an intersection of the experimental construction. Individual gas atoms, which fly down through the vertical tube in the picture, are ionised by a highly intensive laser. The beam path of the laser is illustrated on the table in the back. The momenta of the electrons and ions that are produced in the reaction are measured with extreme precision by the horizontally depicted bronze-coloured spectrometer in the vacuum chamber. In this way, the effect of the miniscule momentum of the ionised laser light on the electrons can be studied precisely. Credit: Alexander Hartung 

Publication: A. Hartung, S. Eckart, S. Brennecke, J. Rist, D. Trabert, K. Fehre, M. Richter, H. Sann, S. Zeller, K. Henrichs, G. Kastirke, J. Hoehl, A. Kalinin, M. S. Schöffler, T. Jahnke, L. Ph. H. Schmidt, M. Lein, M. Kunitski, R. Dörner: Magnetic fields alter tunneling in strong-field ionization, in: Nature Physics, doi: 10.1038/s41567-019-0653-y. https://www.nature.com/articles/s41567-019-0653-y 

Further information: Professor Reinhard Dörner, Alexander Hartung, Institute for Nuclear Physics, Faculty of Physics, Riedberg Campus, Phone.: +49 69 798-47003 or -47019; Email: doerner[at]atom.uni-frankfurt.de or hartung[at] atom.uni-frankfurt.de.