The Ernst Strüngmann Institute Systems Neuroscience Conference (ESI SyNC) 2022 could finally take place on site again. On September 8 and 9, nearly 100 on-site participants approached the topic of The ever changing brain: through development and evolution. Eleven speakers presented their research on the development, organization, and evolution of the brain - from anatomy to function, from microcircuitry to whole-brain networks, from the origins of cognition in single-celled organisms to complex social behavior in primates.

For those unable to attend or those who would like to recall one or two of the talks, a selection of the presentations can be found and rewatched here.

Daniel Yasumasa Takahashi: Developmental dynamics of vocal communication in marmoset monkeys

Investigating nonhuman primate vocal communication is often with the intention of elucidating their similarities with human speech and thus reconstructing the evolutionary history of this important behavior. However, putative parallels between primate and human vocal behaviors have, in some respects, remained elusive.

Here, we discuss new lines of research in marmoset monkeys on vocal development that could bridge our understanding of the relationship between primate vocalizations and human speech. We describe not only how infant marmoset vocalizations undergo dramatic acoustic changes during development that are not wholly explained by physical growth, but also how, as in humans, contingent vocal responses from parents influence the rate of vocal development. We argue that the similarities in the vocal systems of marmoset monkeys and humans may be due to their shared cooperative breeding strategy, prosociality, and brain development.

Ileana Hanganu-Opatz: Non-linear development of prefrontal function

Marcus Kaiser: Changing connectomes: How brain networks change during evolution

The complete set of connections in the brain is called our connectome. Over the last 20 years we have found out more about how this network is organised and how this organisation is linked to brain function. I will outline how characteristic network features arise during evolution, how they are linked to brain function, and how they originate during individual brain development.

For example, small-world features enable the brain to rapidly integrate and bind information while the modular architecture, present at different hierarchical levels, allows separate processing of various kinds of information while preventing wide-scale spreading of activation. Hubs play critical roles in information processing and are involved in many brain diseases. Recent results show how spatial and temporal factors shape the development of these network features. Temporal factors, in terms of the birth time of neurons and their formation of connections, as well as spatial factors, in terms of the distance between neurons, influence the extent of bidirectional or long-distance connections, network modules, and network hubs. Finally, as brain networks show distinct changes for neurodevelopmental disorders, it will be crucial to understand mechanisms of the connectome development for deciding on personalized treatment options.

Onur Güntürkün: Why birds are smart

For about a century, bird brains were seen as small, non-cortically organized systems that cast a dim prospect on the cognitive abilities of their beholders. Within the last two decades, this view has changed dramatically. My talk will concentrate on discoveries of about the last decade that demonstrate that birds have a prefrontal-like area with identical functional, electrophysiological, neurochemical, and connectional features as the mammalian prefrontal cortex.

Similarly, the avian pallium, although topographically and topologically different from the mammalian one, harbors a connectome akin to those of mammals. In addition, avian neuron numbers are not only much higher than expected by brain size, but also mostly allocated to associative areas in corvids. In parallel, birds developed the ability to cut down the metabolic demands of their neurons by a factor of three. This not only makes a brain with so many neurons affordable but may also provide cellular computational properties that are out of reach for mammals. Lastly, birds even developed a sophisticated cortex within their sensory pallial areas – possibly independent from mammals. Thus, avian and mammalian forebrains converged within 315 million years to an astounding degree. Most importantly, these changes happened very likely in convergent manners without relying on common ancestry. Possibly, evolution does not lack creativity but is just facing a severe limitation of degrees of freedom when wiring a vertebrate brain for sophisticated cognition.

Pamela Lyon: Evolutionary building blocks for a brain

Long before brains and nervous systems evolved, organisms of all kinds had to acquire, value, and otherwise process information about existentially salient features of their environment and parameters of their internal functioning. The integrated product of these signaling pathways generated action, including strictly physiological as well as externally observable change. In Principles of Neural Design Sterling and Laughlin (2015) provide the canonical sketch of the chemical basis of cellular information processing in signaling systems found today in unicellular prokaryotes and eukaryotes. Such signaling, internal and external (between and among cells), induces and regulates a wide variety of behavior in single-celled organisms, from solitary and collective motility to nutrient foraging and switching, formation of structured communities (biofilms), and collective, network-based interactions at local and population levels; genomic enhancement via horizontal gene transfer, taking up environmental DNA, and a form of sex; and complex staged developmental sequences (sporulation ) leading to radical change in cell types for long-term survival.

Sporulation involves the aggregation of large numbers of cells (tens of thousands plus), but only a proportion survive to germinate another day. Programmed cell death (‘altruistic suicide’) and cellular transformation into specialized support structures claim a substantial proportion of the viable participants. The boldfaced text above reflects known features of brain development and activity. Add to this 1) various types of cell-cell communication, including via secreted signals (packaged in vesicles in some phyla,) and action potentials generated by ion channels (including calcium ion channels); 2) oscillatory activity within single cells as well as in cell collectives; 3) cell migration following chemical gradients (chemotaxis); and 4) large, densely clustered arrays of signaling proteins (several thousands of proteins) capable of detecting and integrating multiple types of stimuli—a highly conserved form of sensorimotor architecture in prokaryotes that has been compared to a ‘nano brain’. In short, the first animals to develop nervous systems and brains already had an information-processing toolkit bristling with options. How these mechanisms are employed to ensure survival, growth, and reproduction in non-neural organisms may hold clues to their recruitment in the origin and evolution of nervous systems and help neuroscientists to better understand brains.

Rebecca Saxe: Human infants’ brains are specialized for social functions

Human infants have distinct social representations and motivations. Infants’ learning about, and representations of, other people are not just a downstream consequence of generic processes that promote learning in the nonsocial environment, nor are they built by gradual, bottom-up adjustment to the statistics of visual experience. On the contrary, infants’ attention to people depends on specific inferences about their social relevance; and is related to activity in distinctively social brain regions.

Rosa Cossart: Development of internal cognitive maps in the hippocampus

The hippocampus supports navigation in the real world and across events of our lives (episodic memory). This is supported by cognitive maps relying on two forms of representation, one that is map-based or allocentric and anchored in the external world (external representation) and the other that is self-referenced or egocentric (internal representation), and requires body movement. Work from our lab and others indicates that the circuits contributing to the balance between external and internal representations in the hippocampus would be partly shaped by developmental programs. In contrast to the adult situation, the developing hippocampus during the perinatal period (in both rodents and humans), like many developing cortical structures, is mainly driven by bottom-up external environmental and body-derived signals. Using a combination of two-photon calcium imaging of neuronal activity in non-anesthetized pups, viral tracing, and chemogenetics, we have followed the daily evolution of CA1 dynamics and underlying circuits during early postnatal mouse development.

I will show that the basic building blocks of internal CA1 representations emerge following the disengagement of hippocampal dynamics from self-motion, an abrupt shift relying on the sudden reorganization of GABAergic circuits. We propose that this recently uncovered shift from body-driven to internal dynamics occurs during the early postnatal period (corresponding to the third trimester of gestation in humans), where the hippocampus learns the statistics of the body, and which terminates with the rise of a recurrent inhibitory network is a key step for the emergence of an internal, self-referenced cognitive map onto which exploration of the external world can be grafted. An imbalance between internal and environmental hippocampal representations due to a miswiring of local somatic inhibition could be the basis of several neurodevelopmental disorders.