Neuroscientists at the University of California, Berkeley, have created interactive maps that can predict where different categories of words activate the brain. Their latest map is focused on what happens in the brain when you read stories.

The findings, to appear Aug. 19 in the Journal of Neuroscience, provide further evidence that different people share similar semantic — or word-meaning — topography, opening yet another door to our inner thoughts and narratives. They also have practical implications for learning and for speech disorders, from dyslexia to aphasia.

“At a time when more people are absorbing information via audiobooks, podcasts and even audio texts, our study shows that, whether they’re listening to or reading the same materials, they are processing semantic information similarly,” said study lead author Fatma Deniz, a postdoctoral researcher in neuroscience in the Gallant Lab at UC Berkeley and former data science fellow with the Berkeley Institute for Data Science.

For the study, people listened to stories from “The Moth Radio Hour,” a popular podcast series, and then read those same stories. Using functional MRI, researchers scanned their brains in both the listening and reading conditions, compared their listening-versus-reading brain activity data, and found the maps they created from both datasets were virtually identical.

The results can be viewed in an interactive, 3D, color-coded map, where words — grouped in such categories as visual, tactile, numeric, locational, violent, mental, emotional and social — are presented like vibrant butterflies on flattened cortices. The cortex is the coiled surface layer of gray matter of the cerebrum that coordinates sensory and motor information.

The interactive 3D brain viewer is scheduled to go online this month.

As for clinical applications, the maps could be used to compare language processing in healthy people and in those with stroke, epilepsy and brain injuries that impair speech. Understanding such differences can aid recovery efforts, Deniz said.

The semantic maps can also inform interventions for dyslexia, a widespread, neurodevelopmental language-processing disorder that impairs reading.

“If, in the future, we find that the dyslexic brain has rich semantic language representation when listening to an audiobook or other recording, that could bring more audio materials into the classroom,” Deniz said.

And the same goes for auditory processing disorders, in which people cannot distinguish the sounds or “phonemes” that make up words. “It would be very helpful to be able to compare the listening and reading semantic maps for people with auditory processing disorder,” she said.

Nine volunteers each spent a couple of hours inside functional MRI scanners, listening and then reading stories from “The Moth Radio Hour” as researchers measured their cerebral blood flow.

Their brain activity data, in both conditions, were then matched against time-coded transcriptions of the stories, the results of which were fed into a computer program that scores words according to their relationship to one another.

Using statistical modeling, researchers arranged thousands of words on maps according to their semantic relationships. Under the animals category, for example, one can find the words “bear,” “cat” and “fish.”

The maps, which covered at least one-third of the cerebral cortex, enabled the researchers to predict with accuracy which words would activate which parts of the brain.

The results of the reading experiment came as a surprise to Deniz, who had anticipated some changes in the way readers versus listeners would process semantic information.

“We knew that a few brain regions were activated similarly when you hear a word and read the same word, but I was not expecting such strong similarities in the meaning representation across a large network of brain regions in both these sensory modalities,” Deniz said.

Her study is a follow-up to a 2016 Gallant Lab study that recorded the brain activity of seven study subjects as they listened to stories from “The Moth Radio Hour.”

Future mapping of semantic information will include experiments with people who speak languages other than English, as well as with people who have language-based learning disorders, Deniz said.

Co-authors of the study are Anwar Nunez-Elizalde, Alexander Huth and Jack Gallant, all from UC Berkeley.

The limitations in exploring regimes of dynamical interaction between fields and matter hinder progress in areas ranging from condensed-matter to high-energy physics. But there is an alternative approach: instead of calculating the dynamics, simulate it. Famously, for planetary systems mechanical models known as orreries have been built long before digital computers were developed. In the quantum realm, in recent years so-called ‘quantum simulators’ have been developed, where the unknown dynamics of one quantum system is emulated using another, more controllable one. As they report today in the journal Nature Physics, Frederik Görg and colleagues in the group of Tilman Esslinger in the Department of Physics of ETH Zurich have now made substantial progress towards quantum simulators that might be employed to tackle general classes of problems where the dynamics of matter and fields are coupled.

Hard-to-gauge outcomes

Görg et al. looked not directly at gravitational or electromagnetic fields, but at so-called gauge fields. These are auxiliary fields that are typically not directly observable in experiments, but all the more powerful as a consistent framework for the mathematical treatment of the interactions between particles and fields. As a central concept in physics, gauge fields offer a unique route to understanding forces — the electromagnetic force as well as those holding together subatomic particles. Consequently, there is substantial interest in quantum simulations of gauge fields, in the hope that they provide fresh insight into situations that currently cannot be explored in calculations or computer simulations.

One of the currently leading platforms for simulating complex quantum systems is based on atoms that are cooled to temperatures close to absolute zero and trapped in lattice structures created by laser light. A major advance in recent years has been the realization that the atoms can be used to mimic the behaviour of electrons in a magnetic field, even if the atoms have no electric charge. The key to achieve this is the use of external control parameters to steer the quantum-tunnelling process by which the atoms move between adjacent sites of the optical lattice. Through suitably tailoring the complex phase that the quantum particles pick up in a tunnelling event — known as the ‘Peierls phase’ — the neutral atoms can be made to behave precisely like charged particles moving in a magnetic field. The engineered dynamics in these synthetic gauge fields can be compared to that of classical orreries, where the model planets move as if they were subjected to a substantial gravitational pull from a central body, emulating the behaviour of real planets.

Shaking up the field

The Esslinger group, and others, have used the ultracold-atom platform before to create artificial gauge fields resulting from complex tunnelling phases. But so far, these engineered fields were intrinsically classical, and did not include backaction from the atoms to the gauge field. Hence the excitement as Görg and his co-workers now present a flexible way to achieve coupling between atoms and gauge fields. They propose — and implemented — a procedure to render the Peierls phase dependent on how the atoms are distributed in the lattice. When the distribution changes as a consequence of the interaction with the gauge field, the gauge field itself is altered. This is as if the orrery would speed up or slow down depending on the planetary constellation (which is not needed to model simple celestial mechanics, as the interaction between planets is neglected). In the case of a quantum simulator for quantum gauge fields, however, the interaction between the particles is an essential ingredient.

In the experiments now reported, the ETH physicists created an optical lattice that consists of ‘dimers’, each made from two neighbouring sites in which fermionic atoms can reside either individually or in pairs (see the figure). The tunnelling between the sites of the dimer is controlled by shaking the lattice at two different frequencies with a piezoelectric actuator. The frequencies and phases of the modulation are chosen such that the Peierls phase between sites depends on whether an atom shares its dimer site with another atom of the opposite spin or not (see the animation).

Generality matters

The step to engineering gauge fields that are coupled to ultracold matter is an important one. Ultracold atoms in optical lattices are already established as a versatile platform for quantum simulations, including emulating complex electronic phenomena occurring in solid-state materials. The current work of Görg et al., together with related recent advances by other groups, promises that in the not-too-distant future also more complex quantum gauge fields can be tackled, in particular those that appear in high-energy physics and challenge current classical simulation approaches.

A distinct strength of the approach by Görg et al. is that it can be used for engineering a variety of different quantized gauge fields, beyond the specific scenario they explored experimentally in the just-published paper, as they show based on theoretical considerations. And as the work also demonstrates exquisite experimental control over a highly tunable atomic many-body system, there is now the clear and intriguing prospect of a modern-day orrery that provides insight not into movements on the sky, but deep into the quantum world.

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Scientists like LaShanda Korley, Distinguished Associate Professor of Materials Science and Engineering and Chemical and Biomolecular Engineering at the University of Delaware, want to recreate these chemistries and build similar structures in synthetic materials. By doing so, they can develop new, improved materials for use in sensors, healthcare applications, and much more. Chemistries like these are ubiquitous in nature. The iron-protein interaction in human blood, for example, can be a determinant of disease.

In a paper published in the July 2019 edition of the European Polymer Journal, Korley, joined by materials science and engineering doctoral student Chase Thompson and post-doctoral associate Sourav Chatterjee, described how they built a network of materials, made of zinc and polymers, that mimicked the mechanical gradient of a bristle worm’s jaw.

This project, the culmination of more than five years of work, was funded by a grant from the National Science Foundation. The goal is to utilize natural material systems to understand how to control the interplay of structural features, especially mechanical properties, by combining dynamic and permanent structures, said Korley.

“The idea is: Can you put together two things that don’t really like each other and utilize this idea of dynamics as a way to control how energy is released in the system, which is related to the mechanical behavior?” she said.

The team mimicked the architecture of the bristle worm’s jaw system by adding a zinc-coordinated supramolecular polymer into a covalently crosslinked polyethylene glycol network. With the right concentrations, they found that they could govern the material’s mechanical properties. “The permanent network that we use to house these dynamic interactions is a good platform for achieving these gradient structures,” said Thompson. Next, he plans to investigate ways to influence shape memory and other properties of these materials.

Korley utilizes inspiration from nature to design a variety of materials. She is the principal investigator of PIRE: Bio-Inspired Materials and Systems, a five-year, $5.5 million grant from the National Science Foundation.

Through this project, Korley and collaborators at Case Western Reserve University, the University of California, San Diego, the University of Chicago, Switzerland’s University of Fribourg and the UK’s University of Strathclyde are studying and developing materials that can change toughness in response to their environment, are safer and more effective biological implants, transmit nerve-like electrical signals, and can respond to the environment to initiate biological processes, all for use in soft robotic applications.

For example, researchers are studying ways to make materials that are strong like spider silk and materials that change their shape in response to humidity, such as pine cones, which open in dry conditions and close in moist ones. They are also utilizing the unique materials properties they uncover to develop new 3D printed materials.

The study of soft materials and polymers, long a strength at UD, is growing, in part thanks to Korley’s expertise. Korley and Thomas H. Epps, III, the Thomas and Kipp Gutshall Senior Career Development Professor in Chemical and Biomolecular Engineering and Materials Science and Engineering, have also formed a new research center, the Center for Research in Soft Matter and Polymers (CRISP). Korley and Epps are collaborating with researchers at Chemours and recently published a review article on structure-property relationships in polymeric surface coatings in the journal ACS Applied Polymer Materials.

Korley’s research enterprise also involves outreach to undergraduate students, who can benefit greatly from research experience that complements their classroom work.

“Research gives you a platform to take that fundamental training from the classroom and be able to apply it to a problem,” she said. “In the lab, students learn to think through problems, display and communicate their work, and be leaders and team players. We have all of those aspects in our courses, but I think that there’s a holistic way that undergraduate research can train students to do that.”

Korley is equally passionate about outreach activities that introduce girls in high school to science and engineering. Students from her lab have been involved in tutoring at Serviam Girls Academy in New Castle, Delaware.

“The biggest thing for me is to make an impact, to be collaborative, to really engage with the broader community,” she said. “That’s important to me.”