• 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

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In the world of zebra finches, males sing, and females were thought to just listen. But a new study by Daniela Vallentin at the Max Planck Institute for Biological Intelligence has overturned this assumption. It turns out that female zebra finches play a far more active and crucial role in shaping their sons’ singing abilities than previously thought: They call in response to their son’s vocal exercises, which activates a neuronal circuit in the male brain. In this way, the female feedback directly promotes the accuracy of the learned song and highlights the often-overlooked importance of females shaping complex behaviors.

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As with many bird species, only male zebra finches are able to learn the species-typical song from a tutor, usually the father. Over a period of three months, the young males initially only listen to the tutor. They then begin to practice the song they have heard and eventually develop their own version of it, which they keep for the rest of their lives. Females, on the other hand, do not sing; their calls are innate and primarily used to communicate with their partner. Therefore, research on song learning has mainly focused on males, i.e. the relationship between tutor and apprentice. The potential influence of females and their calls on song development has so far been largely neglected.

Vallentin and her team now discovered that female zebra finches play a far more active and influential role in shaping their sons’ vocal abilities than previously imagined. When young males practice their songs, the females don’t merely listen; they actively respond with specific calls. These calls, the researchers found, trigger a unique neuronal response in the males’ brains, influencing their learning process and enabling them to more accurately mimic their tutor’s song. In essence, females act as vocal coaches, providing real-time feedback that helps males refine their songs. This revelation challenges the traditional, male-centric view of song learning, highlighting the often-overlooked importance of females in shaping complex behaviors. As Linda Bistere, the study’s first author, remarks, the findings were both “exciting and unexpected,” underscoring the value of questioning assumptions and exploring uncharted territories in scientific research.

The findings serve as a reminder that even subtle interactions between the sexes can have a profound impact on the development of complex behaviors like birdsong. It also underscores the importance of looking beyond the obvious when studying the natural world, as hidden influences and unexpected collaborations may be waiting to be discovered.

So, the next time you hear a male zebra finch serenading his mate, remember that his beautiful song is likely the result of a duet of learning, with both the male and the female playing crucial roles.

Linda Bistere, Carlos M. Gomez-Guzman, Yirong Xiong & Daniela Vallentin; Female calls promote song learning in male juvenile zebra finches; Nature Communications, online October 16, 2024 Link

The post Underestimated female tutors: zebra finch mothers coach their sons to sing better first appeared on Max Planck Neuroscience.

For the first time, neuroscientists from Charité – Universitätsmedizin Berlin and the Max Planck Institute for Biological Intelligence (currently in the process of being established) have revealed the precise connections between sensory neurons inside the retina and the superior colliculus, a structure in the midbrain. Neuropixels probes are a relatively recent development, representing the next generation of electrodes. Densely packed with recording points, Neuropixels probes are used to record the activity of nerve cells, and have facilitated these recent insights into neuronal circuits. Writing in Nature Communications, the researchers describe a fundamental principle which is common to the visual systems of mammals and birds.

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Two brain structures are crucial to the processing of visual stimuli: the visual cortex in the primary cerebral cortex and the superior colliculus, a structure in the midbrain. Vision and the processing of visual information involve highly complex processes. In simplified terms, the visual cortex is responsible for general visual perception, whereas the structures of the evolutionarily older midbrain are responsible for visually guided reflexive behaviors. The mechanisms and principles involved in visual processing within the visual cortex are well known. Work conducted by a team of researchers led by Dr. Jens Kremkow has contributed to our knowledge in this field and, in 2017, culminated in the establishment of an Emmy Noether Junior Research Group at Charité’s Neuroscience Research Center (NWFZ). The primary aim of the Research Group, which is funded by the Germany Research Foundation (DFG), is to further improve our understanding of nerve cells involved in the visual system. Many unanswered questions remain, including details of the way in which visual information is processed in the midbrain’s superior colliculi.

Retinal ganglion cells, sensory cells found inside the eye’s retina, respond to external visual stimuli and send the information received to the brain. Direct signaling pathways ensure that visual information received by the retinal nerve cells also reaches the midbrain. “What had remained largely unknown until now is the way in which nerve cells in the retina and nerve cells in the midbrain are linked on a functional level. The dearth of knowledge regarding the way in which neurons in the superior colliculi process synaptic inputs was similarly pronounced,” says study lead Dr. Kremkow. “This information is crucial to understanding the mechanisms involved in midbrain processing.” Until now, it had been impossible to measure the activity of synaptically connected retinal and midbrain neurons in living organisms. For their most recent research, the research team developed a method which was based on measurements obtained with innovative, high-density electrodes known as Neuropixels probes. Precisely speaking, Neuropixels probes are tiny, linear electrode arrays featuring approximately one thousand recording sites along a narrow shank. Comprising 384 electrodes for the simultaneous recording of electric activity of neurons in the brain, these devices have become game-changers within the field of neuroscience.

Researchers working at Charité and the Max Planck Institute for Biological Intelligence have now used this new technology to determine the relevant midbrain structures in mice (superior colliculi) and birds (optic tectum). Both brain structures have a common evolutionary origin and play an important role in the visual processing of retinal input signals in both groups of animals. Their work led the researchers to a surprising discovery: “Usually, this type of electrophysiological recording measures electrical signals from action potentials which originate in the soma, the neuron’s cell body,” explains Dr. Kremkow. “In our recordings, however, we noticed signals whose appearance differed from that of normal action potentials. We went on to investigate the cause of this phenomenon, and found that input signals in the midbrain were caused by action potentials propagated within the ‘axonal arbors’ (branches) of the retinal ganglion cells. Our findings suggest that the new electron array technology can be used to record the electrical signals emanating from axons, the nerve cell projections which transmit neuronal signals. This is a brand-new finding.” In a global first, Dr. Kremkow’s team was able to simultaneously capture the activity of nerve cells in the retina and their synaptically connected target neurons in the midbrain.

Until now, the functional wiring between the eye and midbrain had remained an unknown quantity. The researchers were able to show at the single-cell level that the spatial organization of the inputs from retinal ganglion cells in the midbrain constitutes a very precise representation of the original retinal input. “The structures of the midbrain effectively provide an almost one-to-one copy of the retinal structure,” says Dr. Kremkow. He continues: “Another new finding for us was that the neurons in the midbrain receive a very strong and specific synaptic input from retinal ganglion cells, but only from a small number of these sensory neurons. These neural pathways enable a very structured and functional connection between the eye’s retina and the corresponding regions of the midbrain.” Among other things, this new insight will enhance our understanding of the phenomenon known as blindsight, which can be observed in individuals who have sustained damage to the visual cortex due to trauma or tumor. Incapable of conscious perception, these individuals retain a residual ability to process visual information, which results in an intuitive perception of stimuli, contours, movement and even colors that appears to be linked to the midbrain.

To test whether the principles initially observed in the mouse model could also apply to other vertebrates – and hence whether they could be more general in nature – Dr. Kremkow and his team worked alongside a team from the Max Planck Institute for Biological Intelligence, where a Lise Meitner Research Group led by Dr. Daniele Vallentin focuses on neuronal circuits responsible for the coordination of precise movements in birds. “Using the same types of measurements, we were able to show that, in zebra finches, the spatial organization of the nerve tracts connecting the retina and midbrain follow a similar principle,” says Dr. Vallentin. She adds: “This finding was surprising, given that birds have significantly higher visual acuity and the evolutionary distance between birds and mammals is considerable.” The researchers’ observations suggest that the retinal ganglion cells in both the optical tectum and the superior colliculi show similar spatial organization and functional wiring. Their findings led the researchers to conclude that the principles discovered must be crucial to visual processing in the mammalian midbrain. These principles may even be general in nature, applying to all vertebrate brains, including those of humans.

Regarding the researchers’ future plans, Dr. Kremkow says: “Now that we understand the functional, mosaic-like connections between retinal ganglion cells and neurons within the superior colliculi, we will further explore the way in which sensory signals are processed in the vision system, specifically in the regions of the midbrain, and how they contribute to visually-guided reflexive behavior.” The team also want to establish whether the new method might be used in other structures and whether it could be used to measure axonal activity elsewhere in the brain. Should this prove possible, it would open up a wealth of new opportunities to explore the brain’s underlying mechanisms.

This text corresponds to a press release by Charité – Universitätsmedizin Berlin.

CONTACT:

Dr. Jens Kremkow
Neuroscience Research Center
Charité – Universitätsmedizin Berlin
Email: jens.kremkow@charite.de

Dr. Daniela Vallentin
Lise Meitner Research Group Leader
Max Planck Institute for Biological Intelligence, in foundation
Seewiesen
E-Mail: daniela.vallentin@bi.mpg.de

Jérémie Sibille, Carolin Gehr, Jonathan I. Benichov, Hymavathy Balasubramanian, Kai Lun Teh, Tatiana Lupashina, Daniela Vallentin, Jens Kremkow, High-density electrode recordings reveal strong and specific connections between retinal ganglion cells and midbrain neurons. Nature Communications, online 5 September 2022 Link

The post How visual information travels from the retina to the midbrain first appeared on Max Planck Neuroscience.

SIGNIFICANCE STATEMENT: Most social-living vertebrates produce large numbers of calls per day, and the calls have prominent roles in social interactions. Here, we show neuronal mechanisms that are active during call-based vocal communication of zebra finches, a highly social songbird species. HVC, a forebrain nucleus known for its importance in control of learned vocalizations of songbirds, displays predictive activity that may enable the male to adjust his own calling pattern to produce very fast sequences of male female call exchanges.

Ma S, Ter Maat A, Gahr M. (2020). Neurotelemetry Reveals Putative Predictive Activity in HVC during Call-Based Vocal Communications in Zebra Finches. J Neurosci. 40(32):6219-6227.
Article Link

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