Spontaneous activity

Daniel Levenstein discusses spontaneous activity in the hippocampus and cortex, especially during sleep, and its relationship to learning, memory and navigation. He explains how AI models can help investigate these dynamics, alongside questions about model systems, cognitive maps and the relationship between neuroscience experiments and theory.

Introduction: Spontaneous activity in visual cortex is high-dimensional and state-dependent, yet its organizing principles are unclear (Stringer et al. Science 2019; Berkes et al. Science 2011). We combine large-scale imaging, modelling, and theory to ask: 1. Does spontaneous activity share the structure of evoked activity? 2. Is spontaneous activity organized spatially? Methods: We constructed a modified Light Beads Microscope (Demas et al. Nature Methods 2021) to image Ca2+ transients in excitatory neurons from large volumes. We developed an open-source, GPU-accelerated volumetric cell extra

Interacting with the environment to process sensory information, generate perceptions, and shape goal-directed behavior engages neural networks in brain areas with highly varied representations, ranging from unimodal sensory cortices to higher-order association areas. These networks form and undergo considerable and potentially area-specific refinement over development. However, recent work suggests a much greater degree of commonality in the functional organization of networks across such diverse cortical areas during early development. It is currently unknown whether this initially common st

The emergence of spontaneous activity in the form of synchronized bursting events (SBE) is considered to play a crucial role in activity-dependent development of neuronal networks. As inhibition matures, the spatiotemporal structure of activity becomes increasingly influenced by the balance between excitation and inhibition (E/I). Moreover, intricate interactions between excitatory (ENs) and inhibitory (INs) neurons may arise during their activity-dependent structural differentiation. However, how the resulting spatial embedding of INs and ENs in a network impacts on the spatiotemporal structu

Spontaneous activity in young ferrets (p22) is organised into modular, low-dimensional patterns across multiple cortical areas [1]. In the following two weeks (p22-43), these activity patterns undergo a transition similar in all areas, and show a gradual increase in dimensionality in most areas, suggesting an expansion of representational capacity [2]. However, it is unclear what the functional role of having low-dimensional activity patterns at the initial stage of development is, since one would expect the limited dimensionality to restrict representational learning. In this work, we investi

…sensory cortices experience patterned spontaneous activity which is known to refine neural connectivity, preparing the animal to engage in sensorimotor tasks immediately upon ear and eye opening (∼P4 and ∼P15, respectively). In primary visual cortex (V1), spontaneous activity originates from two sources, from the retina relayed by thalamus and intrinsically generated in the cortex. Spontaneous events from these two sources have different spatiotemporal properties:

Spontaneous activity of neuron populations is often characterized by unique network events, ranging from sharp-wave ripples to slow propagating waves. One of the prominent examples of such network events is population bursting (Fig. 1a), robustly emerging in networks of primary neurons in vitro [1]. Population bursting is believed to depend on the genetic, single neuron, and network features. Typically, the events are characterized via several summary statistics and compared between observations [2]. Although changes in the burst morphology are frequently observed, they are much harder to quan

…early genetic programs and neuronal activity. Spontaneous activity emerges early in mammalian cortical development, preceding sensory perception and characterized by synchronized patterns of neuronal activity. The precise nature of the inte

Maternal depression presents risks to both fetal and child development. While treating maternal depression with antidepressants during pregnancy can alleviate the condition, it also has implications for the development of the offspring. Our study aims to explore the impact of maternal depression and/or prenatal antidepressant treatment on offspring neuronal excitability.We implemented an animal model of maternal depression through chronic and unpredictable stress exposure. Mirtazapine served as the chosen antidepressant. Four experimental groups were used: no stress with vehicle, stress with v

…the interplay between evoked and spontaneous population activity and its impact on auditory processing within the primary auditory cortex of freely-moving gerbil

The sensory representation in the brain's primary areas relies on intricate anatomical and functional mapping, particularly evident in rodents where facial somatosensory territories have dedicated cortical maps for precise sensory processing. In the mouse primary somatosensory cortex (S1), mystacial and upper lip whiskers are processed in the postero-medial barrel subfield (PMBSF) and antero-lateral barrel subfield (ALBSF), respectively. PMBSF barrels are known for their size and high-resolution mapping, while ALBSF barrels are smaller and less defined. Traditionally, these differences in whis

…perceptually unrelated external, and spontaneously generated internal activity. Such activity has traditionally been understood as noise. In feed-forward networks, such noise can pose a challenge, because disambiguating stimulus-evoked activity and noise in deeper layers becomes increasingly difficult, for example in pattern classification tasks. On the other hand, the beneficial effects of noise for stochastic regularization and preventing co-adaptation were recognized in deep

In ferret visual cortex, spontaneous activity before eye-opening is organised into large-scale, modular patterns in the absence of long-range projections. This correlated activity reveals endogenous networks that predict aspects of future orientation selectivity. Previous modelling works have shown that the long-range correlations observed in these networks can arise from locally connected neurons through multi-synaptic interactions. Here we seek to map the structure of cortical lateral interactions through localised perturbations in vivo.We first constructed a rectified recurrent neural netwo

Spontaneous activity in peripheral sensory neurons has been associated with pain in people with chronic neuropathic and musculoskeletal conditions. It can also be observed in rodent models of chronic pain, where it has traditionally been studied by making electrophysiology recordings from nerve fibres emerging from the dorsal root ganglion. However, these experiments are technically challenging, low-throughput, and prone to bias, with small diameter fibres being most at risk of being under sampled. More recently, in vivo calcium imaging has been adopted to study sensory neuron activity in rode

…the orientation preference map from spontaneous activity on sim

The spontaneous activity in the primary visual cortex (V1) of higher mammals shows spatially modular events of higher activity, where co-active regions are correlated to the underlying structure - orientation maps [1]. This activity travels in sparse waves, in line with the propagation speed of unmyelinated lateral connections [2]. Currently there is a lack of understanding of how these phenomena interact with each other and with evoked activity – so far, they have been only studied experimentally [1,4] and computationally [5,2] in isolation.We present a single large-scale spiking model of cat

…by distributed patterns of cortical activity. The emergence of these cortical representations over the course of development remains an unresolved question. In this talk, I share results from a series of recent studies combining theory and experiments in the cortex of the ferret, a species with a well-defined columnar organization and modular network of orientation-selective responses in visual cortex. I show that prior to the onset of structured sensory experience, endogenous mechanisms set up a highly organized cortical network str

Modern electrophysiological recordings simultaneously capture single-unit spiking activities of hundreds of neurons. These neurons exhibit highly complex coordination patterns. Where does this complexity stem from? One candidate is the ubiquitous heterogeneity in connectivity of local neural circuits. Studying neural network dynamics in the linearized regime and using tools from statistical field theory of disordered systems, we derive relations between structure and dynamics that are readily applicable to subsampled recordings of neural circuits: Measuring the statistics of pairwise covarianc

Cortical circuits embody remarkably reliable neural representations of sensory stimuli that are critical for perception and action. The fundamental structure of these network representations is thought to arise early in development prior to the onset of sensory experience. However, how these endogenously generated networks respond to the onset of sensory experience, and the extent to which they reorganize with experience remains unclear. Here we examine this ‘nature-nurture transform’ using chronic in vivo calcium imaging to probe the developmental emergence of the representation of orientatio

In ferret visual cortex, spontaneous activity prior to eye-opening is organized into large-scale, modular patterns in the absence of long-range horizontal projections. This correlated activity reveals endogenous networks that predict aspects of future orientation selectivity [1]. Previous modelling works have shown that the long-range correlations observed in these networks can arise from purely locally connected neurons through multi-synaptic interactions [1][2]. Here we seek to explicitly map the structure of cortical lateral interactions through localized perturbations in vivo. We first con

…complex spatiotemporal patterns of spontaneous activity, even before sensory organs mature. For example, before vision onset in the mammalian retina, activity propagates in the form of spatiotemporally st

…internal dynamics of the brain (e.g., spontaneous activity, global dynamics, effective connectivity) and its underlying computational principles may hinder our progress in understanding and modeling brain functions. By reexamining evidence from our previous and ongoing work, we will propose new hypotheses and direction

…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 quantit

Modular (columnar) activity is a fundamental mode of neural activity in the cortex of primates and carnivores. Work in ferret visual cortex has shown that already prior to visual experience, early spontaneous activity is modular, revealing large-scale correlated networks that are predictive of future functional networks representing stimulus orientation. However, the origin of modular activity in the early cortex is unclear at present. Computational models predict a striking ability of developing intracortical circuits to self-organize into modular, coordinated patterns of activity which refle