Why birds are smart
November 28, 2023, 6 PM, Alte Mensa am Wilhelmsplatz

Great apes like chimpanzees are smart and have a large neocortex. Birds like corvids and parrots have much smaller brains and no neocortex. This should cast a dim prospect on their cognitive abilities. But studies of the last two decades revealed there is not a single cognitive ability of chimpanzees with brain weights of ca. 400g that meanwhile was not also demonstrated in corvids with brains of just 12g. How is that possible? This can only be the case if complex cognition developed independently several times in animals with different brain organizations. In my talk I will take you on a scientific journey that aims to identify which neural features really seems to matter for complex cognition and are shared by apes, corvids, and parrots. Astoundingly, although bird and mammalian brains look so different, we will see that both independently evolved similar neural solutions to become smart. It is likely that evolution does not lack creativity; it is just facing a severe limitation of degrees of freedom when wiring a vertebrate brain for sophisticated cognition. As a result, it re-invents the wheel over and over again.

The Experimental Economics of Labor Markets, Gender Disparities, and Financial Markets
October 26, 2023, 3 PM, Michael-Lankeit-Lecture Hall, German Primate Center

Holger Rau is an Adjunct Professor at the University of Göttingen. He is an applied micro- and behavioral economist who uses laboratory-, field-, and natural experiments in his studies. His research topics focus on human behavior and are centered around the application of economic preferences and financial incentives to predict outcomes in firms and on markets. The purpose of these studies is to conduct research and interventions that are relevant to policy-making on labor- and financial markets. During this presentation, he will provide an overview of his experimental endeavors in the domains of behavioral labor economics, gender disparities in leadership, decision-making under uncertainty, and public economics. These studies delve into the crucial roles played by economic preferences and institutional factors in phenomena such as motivational crowding-out effects, the gender wage gap, ethical conduct, and investment behavior. At present, he explores the impact of an increased representation of female leaders on the collusive behavior of firms, as well as the efficacy of antitrust policies in such scenarios. He is also delving into the influence of artificial intelligence on economic outcomes within labor markets, with a particular focus on its effects on societal trust.

Feature interference: a neuronal population hypothesis about limits on cognition
September 28, 2023, 12.30 PM, Lecture Hall West, German Primate Center; jointly organised with the Leibniz ScienceCampus Primate Cognition

Flexible cognition is a hallmark of human behavior, but it comes with limits. There are costs to paying attention to many things or switching between tasks. These costs become even more problematic in the many disorders of the brain that limit cognitive capacity. However, there is limited direct evidence of a physiological basis for these limitations. Identifying one will be important for efforts to repair or reduce limits on cognition. I will present multiple lines of evidence from monkey electrophysiology, human and monkey behavior, and recurrent network modeling suggesting a neuronal mechanism that inflicts a limit on cognition and a cost of flexibility. In a behavioral paradigm designed to measure and manipulate subjects’ belief about the relevance of each of two perceptual tasks, we found that humans and monkeys make less accurate perceptual decisions under task uncertainty. To generate hypotheses about a neuronal basis for the task switching cost, we compared two recurrent neural networks (RNNs), trained to produce the correct choice or to reproduce the choices of macaque subjects. The ‘correct-choice’ RNN learned to flexibly switch tasks without incurring a task switch cost, while the ‘monkey-choice’ RNN displayed the expected cost of task switching. Comparing the activity of the recurrent layers of the two models revealed that the ‘correct-choice’ model maintained information relevant to the two tasks in separate subspaces of neuronal activity. But when the task was uncertain, the two subspaces in the ‘monkey-choice’ model collapsed together, leading to interference between tasks. We confirmed predictions of the model in further behavioral and physiological experiments. These results provide a neuronal mechanism for flexible decision-making in neurotypical subjects, as well as its dysfunction in common neurological disorders. They support the general, tantalizing hypothesis that limits in cognitive capacity arise from interference between the neural representations of different stimuli, tasks, or memories.

The evolutionary ecology of decision-making
September 14, 2023, 3 PM, Michael-Lankeit Lecture Hall, German Primate Center

Choosing among spatially distributed options is a central challenge for animals, from deciding among alternative potential food sources or refuges to choosing with whom to associate. Despite this, most studies have focused on the outcome of decisions (i.e., which option among alternatives is chosen), as well as the time taken to make decisions, but seldom on the movement of animals throughout the decision-making process. In this talk, I will present some of my past work where we discovered the algorithm used by the brain while choosing among options distributed in space. I will discuss why evolution seems to have found the same solution to decision-making across scales of biological organisation and the consequences this has for our understanding of movement and social influence in animal collectives. Finally, I will end by talking about some ongoing work where I study similar decision-making processes in the wild.

Visual awareness - and how to restore it when the eyes fail
August 17, 2023, 4 PM, Michael-Lankeit-Lecture-Hall, German Primate Center jointly organised with the European Neuroscience Institute

A long-standing dream of scientists is to be able to directly project images from the outside world onto the visual brain, bypassing the eyes. This method could provide a solution for blind and visually impaired patients. It is the only possible solution for patients in whom the connection between eye and brain is lost so that a prosthesis in the eye is not an option. I will first give an overview of the functioning of the visual cortex, which has low level areas for the analysis of simple visual features and higher areas for the analysis for more complex properties such as object category and face recognition. I will then discuss the mechanisms that determine whether a visual stimulus will reach consciousness or not. It is well established that the electrical stimulation of electrodes in the visual brain leads to artificial percepts called "phosphenes". This method also works in patients who have been blind for decades. The goal of our own research is to bring a prosthesis for the visual brain closer. We implanted 1000 electrodes in the visual cortex to generate complex visual patterns. We demonstrated that this stimulation leads to interpretable images, in the same way that pixels form recognizable patterns on a screen. These new neurotechnological developments take important steps in the direction of prostheses that can restore a rudimantary form of vision.

Mothers, molecules and mortality: the imprint of social relationships across teh life course in wild baboons
Jun 8, 2023, 3 PM, Michael Lankeit Lecture Hall, German Primate Center

Field studies of natural primate populations present a powerful opportunity to investigate the social and ecological determinants of health and fitness using fine-grained observations of known individuals across the life course. Here, I will summarize our emerging understanding of this process in the wild baboons of the Amboseli ecosystem in Kenya, emphasizing the insights provided by integrating behavioral and molecular data. I will review the strong evidence that early life adversity, social status, and affiliative ties in adulthood are central to life outcomes. I will then discuss how, by integrating genomic methods with longitudinal behavioral observations, we have been able to identify sex-specific signatures of social interactions and evidence for biological embedding via changes in DNA methylation. Together, our findings connect classical life course perspectives on primate behavior and life history with changes in gene regulation “under the skin.” They thus illustrate the increasing potential to understand our study subjects at both the whole-organism and molecular levels, even under field conditions.

Architectural design principles of neural circuits
Jun 1, 2023, 3 PM, Old lecture Hall, German Primate Center

The map of synaptic connectivity among neurons in the brain shapes the computations that neural circuits may perform. Inferring the design principles of neural connectomes is, therefore, fundamental for understanding brain development and architecture, neural computations, learning, and behavior. We learn probabilistic generative models for the connectomes of the olfactory bulb of zebrafish, part of the mouse visual cortex, and of C. elegans. We show that in all cases, models that rely on a surprisingly small number of simple biological and physical features accurately predict the existence of individual synapses and their strength, distributions of synaptic indegree and outdegree of the neurons, frequency of sub-network motifs, and more. Furthermore, we simulate synthetic circuits generated by our model and show that they replicate the computation that the real circuit performs. Thus, our results reflect surprisingly simple design principles of real connectomes. We then explore the architectural features that may shape the computation that connectomes may carry. We measure the similarity of simulated spiking neural networks of neurons in terms of their response to different stimuli, and learn a functional metric between networks based on their synaptic differences. We show that unlike common graph theory tools, our metric accurately predicts the similarity of novel networks, relying on a sparse set of architectural features. We then identify potential key architectural features that control the computations that particular connectomes may implement.

Neuronal modelling bridges macroscale adaptive signatures across arousal
May 16, 2023, 3 PM, Michael Lankeit Lecture Hall, German Primate Center

The human brain displays a rich repertoire of states that emerge from the microscopic interactions of cortical and subcortical neurons. Unfortunately, difficulties inherent within large-scale simultaneous neuronal recording limit our ability to link biophysical processes at the microscale to emergent macroscopic brain states. Here we introduce a microscale biophysical network model of layer-5 pyramidal neurons that display graded coarse-sampled dynamics matching those observed in macroscale electrophysiological recordings from macaques and humans. We invert our model to identify the neuronal spike and burst dynamics that differentiate unconscious, dreaming, and awake arousal states and provide novel insights into their functional signatures. We further show that neuromodulatory arousal can mediate different modes of neuronal dynamics around a low-dimensional energy landscape, which in turn changes the response of the model to external stimuli. Our results highlight the promise of multiscale modelling to bridge theories of consciousness across spatiotemporal scales.

Active sensing and flexible neural coding during visually guided navigation
March 21, 2023, 3 PM Michael-Lankeit-Hörsaal, German Primate Center

Natural behavior is flexible and supported by abstracted away beliefs. To understand dynamic neural processing underlying natural behaviour, we use continuous-time foraging tasks either in virtual reality or in a freely-moving arena. Although task rules do not require any particular eye movement, we find that where subjects look is an important component of the behavior. For example, during a simple task in which macaques use a joystick to steer and catch flashing fireflies in a virtual environment lacking position cues, we find that subjects physically tracked this latent task variable with their gaze – an instance of embodied cognition. Restraining eye movements worsened task performance suggesting that embodiment plays a computational role. The above findings are well explained by a neural model with tuned bidirectional connections between oculomotor circuits and circuits that integrate sensory input. In contrast to other task optimized models, this model correctly predicted that leading principal components of the monkey posterior parietal cortex activity should encode their position relative to the goal. These results explain the computational significance of motor signals in evidence-integrating circuits and suggest that plasticity between those circuits might enable efficient learning of complex tasks via embodied cognition.