• Fixed calls, flexible replies: Zebra finch contact calls are vocal abilities the birds are born with and cannot change – but the timing of their replies is flexible. New research shows it is shaped by social context: They respond faster, more often, and with more consistent timing to calls from a familiar bird.
• Neural signature of familiarity: More than two thirds of neurons observed in a key brain region for vocal timing responded to calls, with inhibitory interneurons firing more strongly for familiar callers.
• Broader significance: Even behaviors birds are born with are influenced by social context, raising new questions about how the brain controls vocal exchanges across species.

Conversations with friends have an ease that is hard to replicate with someone you have just met – often replies come more naturally and timing just seems to click. A strikingly similar pattern plays out in zebra finches, very sociable songbirds whose back-and-forth chatter with familiar individuals can take a noticeably different rhythm to exchanges with strangers. Now, researchers at the Max Planck Institute for Biological Intelligence have uncovered how this communication pattern is reflected in the brain, showing that social context influences the activity of neurons involved in vocal communication.

Innate flexibility

Zebra finches are one of the most widely studied songbirds in neuroscience, partly because they are one of the few animal species that, like humans, learn to vocalize by listening to others. Much of this research has focused on their songs, which males learn by copying adults. However, zebra finches also produce short contact calls in the form of simpler sounds that, unlike songs, the birds are born knowing how to make.

Previous studies have shown that when using these calls in social exchanges, the birds tend to contact call more often and more consistently with individuals they are familiar with. But what happens in the brain when a bird hears a familiar call, and how that might shape its reply, remained unclear. A team led by senior researchers Daniela Vallentin and Jonathan Benichov set out to find answers.

The team played zebra finches recordings from familiar and unfamiliar birds, and the birds replied more often, faster, and more consistently to familiar calls. When the team then studied what was happening in the brain, they found a clear neural counterpart.

“We have found that when zebra finches hear a familiar call, their brains respond differently to one from an unfamiliar bird,” says Carlos Gomez-Guzman, doctoral researcher and first author of the study, published in PLOS Computational Biology. “One of the things that surprised us was the sheer scale of the neuronal response: more than 70% of neurons in HVC, a region involved in controlling vocal timing, responded when birds heard a call — showing this region is not just involved in song, but is actively processing social calls too. Within that broad response, neurons called inhibitory interneurons, which help regulate whether and when a bird calls back, fired more strongly and for longer when the caller was familiar. It is not that calls from familiar birds sound particularly different, but when they recognise the call of an acquaintance the social bond between the birds is reflected in how the brain responds.”

How the brain tunes in

Zebra finches make for a fascinating window into vocal exchanges: like human speech, replies between birds typically follow in less than half a second. However, unlike us each bird’s contact call is something it’s born with and cannot reshape – what varies is when and how quickly it calls back.

To find out what was happening in the brain, the team recorded neuronal activity while birds listened to familiar and unfamiliar calls. HVC contains two key types of neurons – excitatory projection neurons, which send signals to other brain regions involved in song and vocal production, and inhibitory interneurons, which act locally, and can influence whether and when a bird initiates a call. Both types of neurons responded upon hearing any call, however interneurons showed a much higher sensitivity to familiarity, firing more intensely and for longer when the caller was known. This neural activity persisted into the window when a bird would normally reply, suggesting it could influence when the bird calls back.

“The strength of this neural activity closely matched how quickly and reliably the birds replied, and using machine learning to study the data we could even distinguish familiar from unfamiliar callers based on interneuron activity alone,” says Gomez-Guzman. “The study shows it is not just learned song that can be flexibly adjusted in communication – behaviors like contact calling, which birds such as zebra finches are born with, can be too”. That opens up fascinating questions: is this precise social timing itself something birds learn? How do these neurons interplay with those in other, evolutionarily older brain regions? Understanding how zebra finches manage this could shed light on why some species are so much better at vocal exchanges than others, and even give insights into the cognitive demands of holding a conversation – something we take for granted, but which requires the brain to listen, decide, and respond in a split second.

Social familiarity strengthens neural and vocal responses to conspecific calls in zebra finches Carlos M. Gomez-Guzman, Daniela Vallentin* & Jonathan I. Benichov*. PLOS Computational Biology, online 11 March 2026 Link

* co-senior authors

The post A familiar voice shapes how zebra finches hear and respond first appeared on Max Planck Neuroscience.

The human brain continuously processes sensory impulses that compete for our attention. Our ability to select enables us to process specific information and ignore irrelevant stimuli. In this way, we can recognize a familiar face in a large crowd of people. But how is this made possible? Max Planck researcher Pascal Fries explains this through electrophysiological mechanisms between nerve cells at different processing layers in the brain, which synchronize through a characteristic key signal.

The brain consists of millions and millions of closely networked nerve cells that exchange electrical signals within a few milliseconds. Fries was able to show that neurons in different brain areas form a unit for processing visual information by synchronizing and firing rhythmically in a characteristic frequency band. This explains why elements such as the shape of a human face and hair color result in specific frequency patterns and signal characteristics that enable the brain to recognize a person.

In time with the brain waves

Fries presented this hypothesis in 2005 in the journal Trends in Cognitive Sciences as a process of communication between nerve cells in different areas of the brain by producing synchronized excitation waves (Communication-Through-Coherence Theory). This explains how our brain is able to direct and maintain attention to very specific elements of our environment despite the various visual stimuli we are constantly confronted with.

Fries used laboratory experiments to show that among the numerous signals that reach the next higher processing level of vision in the brain from our retina in the eye, certain impulses prevail over others. For example, he found synchronous electrical excitation of the gamma frequency band between nerve cells at different levels of visual processing when a visual stimulus was paid attention to. At the same time, he found that neuronal beta rhythms also mediated between neurons.

Fries concluded from subsequent experiments that there must be two opposing information processes during the processing of visual sensory stimuli between nerve cells of the lower and higher hierarchical levels of the brain: According to this, fast gamma waves lead to feedforward impulses between neurons and mediate from lower to higher processing levels of the brain when our eye perceives something new or unexpected. At the same time, feedback connections in the beta frequency band bring predictions about already known information from higher brain regions to the lower processing levels. Fries suggests that feedback communication helps to maintain a state of information.

Disturbances in communication

In the event of pathological changes in the brain, this rhythmic synchronization between neurons can get out of sync. The scientist assumes that his theory is not only applicable to vision and visual information processing in the brain, but also to disorders of the motor cortex in people with Parkinson’s disease.

This area of the brain works together with the spinal cord and muscles. Gamma waves mediate when a movement is to be initiated. Beta waves take over the task of maintaining a state. The ratio of signal strengths between gamma and beta waves in turn regulates the speed of movement.

In Parkinson’s patients, cell degeneration in the brain stem leads to a lack of dopamine and often to an amplification of the beta waves. As a result, a resting signal remains predominant, which makes it difficult for those affected to start a movement from a standstill – a typical symptom of the disease.

From basic research to application

At the Max Planck Institute for Biological Cybernetics, Fries is now investigating how the findings of his previous research can be applied to human cognitive and emotional processes. In particular, he is focusing on the decision between approach and avoidance behavior, a mechanism that is crucial for the search for reward in the context of both positive and negative experiences.

Together with his research group, he proposes the idea that these processes are also controlled by synchronization in different frequency ranges of the brain. If this is confirmed, it could open up new possibilities for therapeutic applications, especially for people with anxiety disorders and depression, where malfunctions in approach and avoidance behavior play a central role.

Scientific contact:

Dr. Pascal Fries
Max Planck Research Group Leader
E-Mail: pascal.fries@tuebingen.mpg.de
Phone: +49 7071 601-606
Max Planck Institute for Biological Cybernetics
Max Planck Ring 8-14
72076 Tübingen
Germany

The post Brain waves in harmony first appeared on Max Planck Neuroscience.

Humans are famously social animals. But they are not alone in their tendency to team up with other individuals of the same species (conspecifics) to reach their goals. In fact, herds of mammals, flocks of birds, or shoals of fish are abundantly observed in nature. How does an animal’s brain recognize other animals of its own kind? Scientists at the Max Planck Institute for Biological Intelligence, in foundation, study this process in young zebrafish. They now discovered a neuronal circuit that mediates social attraction. This specialized pathway, which runs from the retina deep into the brain, enables zebrafish to detect and approach nearby conspecifics.

***

Humans and many other animals live in societies. At a fundamental level, social interactions require individuals to identify others as belonging to their own kind. This usually happens in fractions of a second, often instinctively. Unveiling the neuronal circuits that underly this behavior, however, is anything but trivial.

“There’s an inbuilt challenge in studying social interactions: For us as observers, actions and reactions are intermingled, both in animal behavior and at the neuronal level,” explains Johannes Larsch, project leader in Herwig Baier’s department. “This is because individuals taking part in these interactions influence each other. Both are, at the same time, senders and receivers of social signals. It has been particularly hard to investigate the role of the visual system and its associated brain areas.”

Johannes Larsch’s team nevertheless found a way to elucidate the importance of the visual system in social interactions. The scientists developed an experimental virtual reality setup for zebrafish larvae that simulates conspecifics. All that is needed is a projected dot on a screen, which – and this is important – moves across the display with a jerky movement pattern that is stereotypical of swimming zebrafish. The animals cannot resist this cue: They follow it around for hours, apparently confusing the moving dot with a real conspecific. The researchers had thus discovered a defined visual stimulus that triggers shoaling behavior.

The team could now investigate the neuronal processing of the stimulus. To do so, they extended their virtual-reality setup enabling them to simultaneously measure activity in the fish brain. The experiments revealed that a moving dot activates a specific set of neurons in a brain region known as the thalamus. The same area of the thalamus gets activated when another zebrafish larva swims nearby.

“The thalamus is a sensory control center of the brain that integrates and relays sensory inputs,” explains Johannes Larsch. Sensory information is processed on its route to the thalamus, first in the retina and then in the tectum, a major visual center of the vertebrate brain. By the time the information arrives in the thalamus, it has already been filtered for social cues, such as the jerky movements of a potential conspecific.

The nerve cells identified by the researchers in this region connect the visual system of the zebrafish with other brain regions that are active during social behavior. “We already knew that these other brain regions play a role in controlling social behavior. However, the visual stimuli that activate them were unknown. Our work has filled this knowledge gap and has revealed the neuronal pathways that transmit the signals,” says Larsch.

The importance of the newly identified neurons was confirmed when the researchers specifically blocked the function of these cells. Zebrafish larvae lost their interest in conspecifics as well as moving dots and hardly followed them around anymore.

“The neurons we discovered thus regulate social approach and affiliation in zebrafish,” says Johannes Kappel, graduate student and lead author of the study. “Humans possess a thalamus, too, and many neuronal processes have been conserved during evolution. We also have brain regions that are active when we perceive facial movements or body motion, but the significance of these regions for social behavior has not been explored.”

The study by Kappel, Larsch, Baier and their collaborators has shed light on a part of the brain whose activation provides the elementary “glue” for the bonding of two zebrafish. Collectively, such small-scale interactions create shoals of fish. Social behavior is driven by networks of brains, which are themselves networks of neurons. Concludes Baier: “Neurobiological findings, such as ours, can perhaps inspire and enrich the thinking about the self-organization of animal societies in general, which is currently the domain of other scientific disciplines.”

Johannes M. Kappel, Dominique Förster, Katja Slangewal, Inbal Shainer, Fabian Svara, Joseph C. Donovan, Shachar Sherman, Michal Januszewski, Herwig Baier, Johannes Larsch. Visual recognition of social signals by a tectothalamic neural circuit. Nature, published online 13 July 2022. Link

CONTACT:

Prof. Dr. Herwig Baier
Director
Max Planck Institute for Biological Intelligence, in foundation
Martinsried
E-Mail: herwig.baier@bi.mpg.de

Dr. Johannes Larsch
Project leader
Max Planck Institute for Biological Intelligence, in foundation
Martinsried
E-Mail: johannes.larsch@bi.mpg.de

The post A brain network for social attraction first appeared on Max Planck Neuroscience.

Alison Barker and Vanessa Stempel joined the Max Planck Institute for Brain Research as new research group leaders in 2021. Alison Barker brings a new model organism to the institute: her group will work on the neural mechanisms underlying social communication in naked mole rats. Vanessa Stempel’s group studies the neural circuits underlying adaptive instinctive behaviours, working at the interface of neuroethology and -physiology.

Social Systems and Circuits

In December 2021, Alison Barker started her research group ”Social Systems and Circuits” at the MPI for Brain Research (MPIBR). Her group will focus on the neural mechanisms underlying social communication. Barker’s research adopts a broad evolutionary perspective, studying vocal communication in the naked mole-rat (Heterocephalus glaber). Naked mole-rats are highly social rodents which live in large multi-generational colonies under the rule of a single breeding female, queen.

Our ability to communicate shapes our interactions with our environment and with members of our social groups. This is especially true for the naked mole-rat with colonies of up to 300 individuals in the wild. Individual members within the group must coordinate numerous tasks including foraging, colony defense and care of pups. Naked mole-rats use more than 25 distinct vocalizations which have been shown to support many aspects of their social behavior. Barker’s group will investigate how information related to these cooperative behaviors is encoded in vocalizations and subsequently decoded by specialized neural circuits. By adapting traditional tools for neural circuit dissection along with developing new computational tools and machine learning frameworks, Barker aims to investigate how social information is transmitted within social units and ultimately drives cooperation.

Barker: “I can imagine no better home for the naked mole-rats than the MPIBR, where pioneering neuroscience research is driven by creativity, cutting edge technological innovations and, of course, the study of many other fascinating ‘non-traditional’ model organisms. I’m excited to hear what the naked mole-rats continue to teach us as we begin to delve into their remarkable social behavior on a neural level.”

Alison Barker studied Biochemistry at Brown University. During her doctoral work she studied size selectivity in the visual system of larval zebrafish working with Herwig Baier in San Francisco and in Martinsried at the Max Planck Institute of Neurobiology. In 2015, she received her PhD in Neuroscience from the University of California, San Francisco (UCSF). In her postdoctoral work with Gary Lewin at the Max Delbrück Center for Molecular Medicine she first began working with naked mole-rats where she demonstrated that naked mole-rats use distinct vocal dialects to transmit information about social membership, and that these vocal cues can be learned early in life.

Instinctive Behaviour Circuits

Vanessa Stempel joined the MPI for Brain Research as a new Max Planck Research Group Leader in April 2021.

Instinctive behaviours, such as hunting, escape and mating, are an animal’s survival kit of actions that they acquire with little to no experience. In vertebrates, they are generated by remarkably conserved brain circuits, and it has become increasingly clear in recent years that instinctive behaviours are not just stereotyped action patterns but that they can be flexible in regard to both action selection and execution.

Her group is using a multidisciplinary approach, combining in vivo neural activity recordings and manipulation experiments in ethologically-relevant behavioural tasks with molecular, cellular and circuit-level analyses in vitro.

Stempel: “I feel incredibly lucky to have started my lab here at the MPI for Brain Research, surrounded by amazing colleagues. My group will have a strong neuroethological focus and study the neural mechanisms underlying instinctive behaviours. We have just started to do our first experiments, so it’s truly exciting times!”

Vanessa Stempel studied Biology in Germany, Poland and the UK. She received her PhD from the Free University Berlin, where she worked on neuronal plasticity mechanisms in the group of Dietmar Schmitz. For her postdoc, Vanessa joined the group of Tiago Branco, first at the MRC Laboratory of Molecular Biology, Cambridge and then at UCL, London to investigate the neural basis of escape in mice. In particular, she studied how neural circuits in the brainstem integrate information about threats and initiate escape.

The post Two new research groups at the Max Planck Institute for Brain Research first appeared on Max Planck Neuroscience.

Eph receptors and their partner proteins, the ephrins, are vital for intercellular communication. In the developing brain, they guide young neurons to the right partner cells by repulsion. They also play important roles in cell migration, regeneration, neurodegenerative diseases and the development of cancer. Until recently, scientists assumed that ephrin/Eph signal transmission could only occur through direct cell-cell contact. However, Rüdiger Klein and his team at the Max Planck Institute of Neurobiology have now shown that cells can also pack and release active ephrins and Eph receptors through extracellular vesicles. Not only does this discovery improve our understanding of this communication system, it may also pave the way for new therapeutic strategies.

The human body contains up to 100 billion cells. As they grow, migrate, replicate and move, these cells come into contact with countless other cells and exchange information with them. One way this communication happens is through the ephrin/Eph-receptor system, which is able to guide cell migration and the growth of neuronal extensions. In addition, the ephrin-Eph system also plays a role in plastic processes, such as learning and regeneration, as well as in tumour growth and neurodegenerative diseases.

Eph receptors and their binding partners, the ephrins, are found on the surface of almost all cell types. When an ephrin meets the Eph receptor of another cell, they join to form an ephrin-Eph complex. This triggers processes in one or both cells that generally lead to internalization of the complex and repulsion of one cell away from the other. The repelled cell then moves or grows in another direction. In the nervous system, many such interactions guide the extensions of young neurons to their right destinations.

“This is why it’s so fundamentally important to understand how cells use this system to communicate”, says Rüdiger Klein, whose Department at the Max Planck Institute of Neurobiology is studying ephrins and Eph receptors. It had always seemed clear that ephrins and Ephs could only trigger a signaling process by direct contact between two cells. Recently, however, ephrins and Eph receptors have also been found in extracellular vesicles/exosomes – small droplets of fat released by cells, used as transport vehicles, signal transmitters or for eliminating cell components. “This has thrown up the interesting question of what business Ephs and ephrins have in exosomes”, says Klein.

Intrigued, the Martinsried-based team set up an elaborate experimental study to purify the exosomes from different cell types, including neurons, and analyse their contents. They revealed that many of these exosomes contained ephrins and Ephs, and decoded the cellular mechanism by which they were packed into the exosomes. Interestingly, further analysis showed that the Eph receptors had not been dumped as waste products, but remained active on the exosomes. Eph receptors on the exosomes were able to bind to ephrin molecules on the surface of growing neurons and repel the neuronal extensions. This proves, for the first time, that cells can send ephrins and Ephs out to transmit signals over a distance. “It opens up a whole range of new possibilities”, says Rüdiger Klein. Ephrins and Eph receptors have also been found in the exosomes of cancer cells. “This might mean that strategies to control exosome release could be used to interrupt the ephrin-Eph signaling pathway and thereby disrupt tumour growth”, he surmises.

Original Publication:
Jingyi Gong, Roman Körner, Louise Gaitanos, Rüdiger Klein
Exosomes mediate cell contact-independent ephrin-Eph signaling during axon guidance.
Published June 27, 2016 // JCB vol. 214 no. 1 35-44 The Rockefeller University Press, doi: 10.1083/jcb.201601085

The post Cells send out stop signs first appeared on Max Planck Neuroscience.

Not only humans learn how to communicate via the manual modality. Gestures are also important in the communication of great apes. Mothers of chimpanzees, for example, communicate with their infants mainly by tactile, later by visual gestures. Infants also rely on vocalizations and actions, especially older ones. This is what researchers of the Max Planck Institute for Ornithology and colleagues have observed in two chimpanzee species and communities of wild chimpanzees in Uganda and the Ivory Coast over two years and they found many parallels in the communication culture between the groups.

Across cultures and languages, human children enter language hands first. Comparative research into language origins has therefore, beside vocalisations and multi-modal combinations, been focusing on gestural complexity and underlying cognitive mechanisms in our closest living relatives, the great apes. Recent studies showed that gestures are used as intentionally produced, elaborate and flexible communicative strategies and play an important role in great ape societies.

However, researchers have so far mainly focused on captive groups or single communities in the wild. Now for the first time, Marlen Fröhlich and Simone Pika of the Humboldt Research Group at the Max Planck Institute for Ornithology in Seewiesen in collaboration with colleagues of the Max Planck Institute for Evolutionary Anthropology in Leipzig carried out a systematic comparative study of gestural signalling. In two consecutive years, they studied two chimpanzee species and communities in Kibale National Park, Uganda and Taï National Park, Ivory Coast. “One of the most intriguing questions was, whether individuals living under active selection pressures and in different communities show the same ‘culture’ of communication”, says Marlen Fröhlich, first author of the study and PhD student at the Max Planck Institute for Ornithology in Seewiesen.

The researchers focused on interactions between mother-infant dyads to initiate joint travel. The results showed that chimpanzee mothers preferentially used gestures to initiate joint travel, while infants also relied on vocalizations and actions. Especially in older infants (older than two years) vocalisations were frequently combined with visual gestures. In young chimpanzees, a developmental shift from actions to gestures and from tactile to visual gestures was found. The study also showed that chimpanzee mothers seemed to have an understanding of the communicative ability of their infants. “I was really intrigued to see how patient and tolerant chimpanzee mothers can be when prompting their infants into leaving a location and traveling together to a new one”, says Marlen Fröhlich.

In both communities, mothers were the main initiators of joint travel and each mother seemed to use her own individual communicative tool-set. “We thus think that it is time to reconsider current theories on gesture acquisition and postulate a revised theory of gestural acquisition— ‘social negotiation’”, says Simone Pika, head of the study and the research group in Seewiesen. This theory suggests that individuals ‘socially negotiate’ whether a given behaviour can also be used communicatively and learn that social constellation and context assigns different meaning/s. For instance the same gesture of the mother, an outstretched arm, might function as a play invitation in a relaxed setting but signals urgency when accompanied by her fear grin and an aggressive male approaching. However, further observations are necessary to test this theory in detail and to clarify whether gestural acquisition indeed involves shared understanding and mutual construction in real time by both interactants.

Original Publication:
Marlen Fröhlich, Roman M. Wittig and Simone Pika
‘Should I stay or should I go?’ Initiation of joint travel in mother–infant dyads of two chimpanzee communities in the wild.
Animal Cognition, 2016 (DOI: 10.1007/s10071-015-0948-z)
http://link.springer.com/article/10.1007%2Fs10071-015-0948-z

The post Mother-infant communication in chimpanzees first appeared on Max Planck Neuroscience.