PUBLIC
Lecture Series
Stefano Fusi, PhD: Disentangled and flexible representations in the prefrontal cortex and the hippocampus
The curse of dimensionality plagues models of reinforcement learning and decision-making. The process of abstraction solves this by constructing variables describing features shared by different instances, reducing dimensionality, and enabling generalization in novel situations. Stefano Fusi’s team characterized neural representations in monkeys and humans performing a task described by different hidden and explicit variables. Abstraction was defined operationally using the generalization performance of neural decoders across task conditions not used for training, which requires a particular geometry of neural representations. Neural ensembles in prefrontal cortex, hippocampus, and simulated neural networks simultaneously represented multiple variables in a geometry reflecting abstraction but that still allowed a linear classifier to decode a large number of other variables (high shattering dimensionality). Furthermore, this geometry changed in relation to task events and performance. These findings elucidate how the brain and artificial systems represent variables in an abstract format while preserving the flexibility conferred by high shattering dimensionality.
Timothy Buschman, PhD: Neural Dynamics of Cognitive Control
Cognitive control guides behavior by controlling what, where, and how information is represented in the brain. Several mechanisms have been proposed to support cognitive control, such as gain modulation or synchronizing neural activity. In this talk, Timothy Buschman will present evidence for a new mechanism of cognitive control: by dynamically transforming neural representations into and out of different ‘subspaces’, cognitive control can route information through the brain.
Jessica Cardin, PhD: State-dependent patterns of neuromodulatory signaling in the cortex
Spontaneous and sensory-evoked cortical activity is highly state-dependent, promoting the functional flexibility of cortical circuits underlying perception and cognition. Using neural recordings in combination with behavioral state monitoring, Jessica Cardin’s team finds that arousal and motor activity have complementary roles in regulating local cortical operations, providing dynamic control of sensory encoding. They recently developed an approach for dual mesoscopic imaging of acetylcholine release and neural activity across the entire cortical mantle in behaving mice. They find spatiotemporally heterogeneous patterns of cholinergic signaling across the cortex. These findings suggest dynamic state-dependent regulation of cortical network operations at the levels of both local and large-scale circuits.
Nicholas A. Steinmetz, PhD: Large-scale electrophysiology with Neuropixels: Reproducibility and Distributed Coding
In this talk, Nicholas Steinmetz will describe the use of Neuropixels technology to make large-scale electrophysiological recordings from the brains of awake mammals. In particular, he will focus on the efforts of the International Brain Laboratory to establish the reproducibility of measurements made with Neuropixels across experimenters and across laboratories. Moreover, the results of experiments using Neuropixels to study distributed coding of vision and action across the mouse brain will be described.
Marie Carlén, PhD: Towards functional maps of the mouse prefrontal cortex
The structure and function of the prefrontal cortex (PFC) across species remain unresolved. Taking advantage of the technological toolbox available to studies in rodents, our studies aim to outline the mouse PFC through integration of structural, molecular and functional characteristics. Whole-brain tracing of connectivity and spatial transcriptomics give a novel and unbiased view of structure of the mouse PFC. The connectivity outlines the mouse PFC as a module with dense intraconnectivity, questioning independent processing in discrete prefrontal subregions. In line with this, higher cognitive functions are considered to be integrative rather than localized. Marie Carlén in her talk presents her lab’s finding on how the PFC can be annotated based on neuronal activity and what the neuronal activities reveal about hierarchy and local and non-local functions in prefrontal subterritories.
Ofer Yizhar, PhD: Optogenetic dissection of local and long-range connections in prefrontal circuits
The PFC plays a part in multiple brain-wide networks regulating behavior, and its long-range connections to different cortical and subcortical targets are thought to be involved in distinct behavioral functions. Ofer Yizhar’s team is interested in understanding how PFC microcircuits process behavioral information, and how distinct PFC output neuron populations regulate learning, decision-making and social behavior. First, he will describe a set of experiments aimed at understanding the structure of synaptic connectivity among amygdala-projecting neurons in the mPFC. Using single-neuron two-photon optogenetic stimulation and imaging, he demonstrates that these neurons show unique layer-specific connectivity features compared with randomly sampled mPFC neurons. To efficiently suppress synaptic transmission, they engineered a new set of bistable rhodopsins that selectively couple to the Gi/o signaling pathway and can be used to suppress synaptic release in vitro and in vivo, in a spatially and temporally-precise manner.
Christine Constantinople, PhD: Neural mechanisms of inference
Julijana Gjorgjieva, PhD: Emerge of organization and computation in neural circuits
Generating brain circuits that are both flexible and stable requires the coordination of powerful developmental mechanisms acting at different scales, including activity-dependent synaptic plasticity and changes in single neuron properties. The brain prepares to efficiently compute information and reliably generate behavior during early development without any prior sensory experience but through patterned spontaneous activity. After the onset of sensory experience, ongoing activity continues to modify sensory circuits, and plays an important functional role in the mature brain. Using quantitative data analysis, experiment-driven theory and computational modeling, Julijana Gjorgjieva will present a framework for how neural circuits are built and organized during early postnatal development into functional units, and how they are modified by intact and perturbed sensory-evoked activity.
Prof. Dr. Sonja Grün: Spatio-temporal spike patterns in monkey and model
It has been postulated that information processing in the brain is based on precise temporal correlation of neural activity across populations of neurons. In a recent study, we found spatio-temporal spike patterns (STPs) in experimental recordings (10×10 Utah array) from monkey motor cortex using the SPADE method, while the animals were performing a reach-to-grasp task. These patterns were not clustered in cortical space, but distributed. Particularly surprising was, that individual neurons participate in different STPs occurring in different behavioral epochs. This also means that neurons are part in different cell assemblies. In a further study, we were wondering if those STPs could be explained by a synfire chain (SFC) like model. An SFC is composed of groups of neurons connected in feed-forward manner from one group to the next with high convergence and divergence.
Prof. Dr. Peter Uhlhaas: Neural Oscillations, Sensory Dysfunctions and Schizophrenia: A Translational and Developmental Perspective
Prof. Dr. Martin Vinck: The role of rhythms and spiking sequences in predictive processing
Dr. Claudia Böhm: Time, space and memory in prefrontal cortex
during flexible behavior
Christoph Kellendonk, PhD: Adolescent thalamic inhibition leads to long-lasting
impairments in prefrontal cortex function
Prof. Dr. Earl K. Miller: Cognition is Rhythm
