Past events

Understanding how social influence shapes biological processes is a central challenge in contemporary science, essential for achieving progress in a variety of fields ranging from the organization and evolution of coordinated collective action among cells, or animals, to the dynamics of information exchange in human societies. Using an integrated experimental and theoretical approach I will address how, and why, animals exhibit highly-coordinated collective behavior. I will demonstrate new imaging and virtual reality (VR) technology that allows us to reconstruct (automatically) the dynamic, time-varying sensory networks by which social influence propagates in groups. This allows us to identify, for any instant in time, the most socially-influential individuals, to reveal the (counterintuitive) relationship between network structure and social contagion, and to predict the magnitude of complex behavioural cascades within groups before they actually occur. By investigating the coupling between spatial and information dynamics in groups we also demonstrate that emergent problem solving is the predominant mechanism by which mobile groups sense, and respond to complex environmental gradients. Finally I will reveal the critical role uninformed, or unbiased, individuals play in effecting fast, democratic consensus decision-making in collectives, and will test these predictions with experiments involving schooling fish and wild baboons, as well as suggest how such results may relate to decision-making in neural systems.

The introduction of two-photon microscopy for in vivo imaging has opened the door to chronic monitoring of individual neurons in the adult brain and the study of structural plasticity mechanisms at a very fine scale. Perhaps the biggest contribution of this modern anatomical method has been the discovery that even across the stable excitatory dendritic scaffold there is significant capacity for synaptic remodeling, and that synaptic structural rearrangements are a key mechanism mediating neural circuit adaptation and behavioral plasticity in the adult. To monitor the extent and nature of excitatory and inhibitory synapse dynamics on individual L2/3 pyramidal neurons in mouse visual cortex in vivo, we labeled these neurons with a fluorescent cell fill as well as the fluorescently tagged synaptic scaffolding molecules, Teal-Gephyrin to label inhibitory synapses, and mCherry-PSD-95 to label excitatory synapses. We simultaneously tracked the daily dynamics of both synapse types using spectrally resolved two-photon microscopy. We found that aside from the lower magnitude of excitatory synaptic changes in the adult, as compared to inhibitory ones, excitatory synapse dynamics appear to follow a different logic than inhibitory dynamics. While excitatory dynamics seem to follow a sampling strategy to search for and create connections with new presynaptic partners, inhibitory synapse dynamics likely serve to locally modulate gain at specific cellular locales.

Animal ability to effectively locate and navigate towards food sources is central for survival. Here, using C. elegans nematodes, we revealed a previously unknown mechanism underlying efficient navigation in chemical gradients. This mechanism relies on the orchestrated dynamics of two types of chemosensory neurons: one coding gradients via stochastic pulsatile dynamics, and the second coding the gradients deterministically in a graded manner. The pulsatile dynamics obeys a novel principle where the activity adapts to the magnitude of the gradient derivative, allowing animals to take trajectories better oriented towards the target. The robust response of the second neuron to negative derivatives promotes immediate turns, thus alleviating costs of erroneous turns possibly incurred by the first neuron. This mechanism empowers an efficient navigation strategy which outperforms the classical biased-random walk strategy. Importantly, this mechanism is generalizable and other sensory modalities may use similar principles for efficient gradient-based navigation.

The introduction of two-photon microscopy for in vivo imaging has opened the door to chronic monitoring of individual neurons in the adult brain and the study of structural plasticity mechanisms at a very fine scale. Perhaps the biggest contribution of this modern anatomical method has been the discovery that even across the stable excitatory dendritic scaffold there is significant capacity for synaptic remodeling, and that synaptic structural rearrangements are a key mechanism mediating neural circuit adaptation and behavioral plasticity in the adult. To monitor the extent and nature of excitatory and inhibitory synapse dynamics on individual L2/3 pyramidal neurons in mouse visual cortex in vivo, we labeled these neurons with a fluorescent cell fill as well as the fluorescently tagged synaptic scaffolding molecules, Teal-Gephyrin to label inhibitory synapses, and mCherry-PSD-95 to label excitatory synapses. We simultaneously tracked the daily dynamics of both synapse types using spectrally resolved two-photon microscopy. We found that aside from the lower magnitude of excitatory synaptic changes in the adult, as compared to inhibitory ones, excitatory synapse dynamics appear to follow a different logic than inhibitory dynamics. While excitatory dynamics seem to follow a sampling strategy to search for and create connections with new presynaptic partners, inhibitory synapse dynamics likely serve to locally modulate gain at specific cellular locales.

This talk will consider the problem of sensorimotor co-ordination in mammals through the lens of vibrissal touch, and via the methodology of embodied computational neuroscience—using biomimetic robots to synthesize and investigate models of mammalian brain architecture. I will consider five major brain sub-systems from the perspective of their likely role in vibrissal system function—superior colliculus, basal ganglia, somatosensory cortex, cerebellum, and hippocampus. With respect to each of these sub-systems, the talk will illustrate how embodied modelling has helped elucidate their likely function in the brain of awake behaving animals, and will demonstrate how the appropriate co-ordination of these sub-systems, within a model of brain architecture, can give rise to integrated behaviour in life-like whiskered robots.

The lecture will be directly followed by an open meeting for all members of the brain imaging community in Israel where we will discuss access to the 7-Tesla magnet that is at the heart of the national center. If you want to scan at 7T, please attend.