Periodic Reporting for period 1 - InsulaBodyLoop (The Insula-Body Loop for Neural Control of Gut Physiology)
Reporting period: 2022-03-01 to 2024-08-31
The brain and body are in a continuous dialog. Our brains constantly receive sensory information from within our body, as well as from the external environment, and then use it to regulate bodily function. Brain-body communication is essential for our physical and mental health, yet little is known about how it is achieved at the neurobiological level. A large corpus of work implicates the insular cortex as a central node in the brain’s interoceptive network. Current models suggest that insular cortex integrates internal and external sensory information to regulate bodily physiology. Yet direct experimental evidence has been scarce. Our research program focuses on the insular cortex as part of a dynamic loop with the gastrointestinal system, which regulates peripheral metabolic function and feeding behaviour. Two fundamental questions form the core of this project: (1) How do the sight, smell, and taste of a savoury dish, or a sweet dessert, enable our brains to predict the post-ingestive nutrients they will supply? (2) How are these predictions relayed to our body to preemptively prepare it for consumption, e.g. by inducing salivation and insulin release? To answer these questions, we need to understand both cortical predictive computations, as well as peripheral physiology. We are building on our expertise to use an interdisciplinary approach, combining cutting-edge neuroscience and computational methods with recordings and optogenetic control of peripheral physiology. This will reveal: (1) how insular cortex represents internal sensations, (2) how insular cortex forms associations between internal and external sensory information, and (3) how these associations are relayed to the body to maintain homeostasis. This study will provide a conceptual and methodological foundation for future elucidation of how different internal sensory modalities act together within the brain-body loop to maintain our physical and emotional health.
During the first reporting period we have established most of the new experimental systems outlined in the proposal, and they are all now being routinely used in our lab. First, we have established of a behavioural assay to evaluate taste-independent post-ingestive reinforcing effects of nutrients. Second, we have developed novel assays for non-invasive artificial stimulation of specific gut signals using optogenetics. Third, we examined the role of insular cortex activity in anticipatory physiological regulation. Fourth, we established two-photon holography for optogenetic activation of precise insular cortex activity patterns via a microprism.
In addition to these achievements, we sought to create a comprehensive analytical pipeline for detailed analyses of neuronal population activity patterns in insular cortex. To do so, we leveraged recent advances in unsupervised machine learning to study insular cortex population activity patterns (a.k.a. neuronal manifold) in mice performing goal-directed behaviours aimed to fulfil physiological needs. We found that the insular cortex activity manifold is remarkably consistent across different animals and under different physiological need states. Activity dynamics within the neuronal manifold were highly stereotyped during food or water rewards, enabling robust prediction of single-trial outcomes across different mice, and across various natural and artificial physiological needs. Comparing goal-directed behaviour with self-paced free consumption, we found that the stereotyped activity patterns reflect task-dependent goal-directed reward anticipation, and not licking, taste, or positive valence. These findings revealed a core computation in insular cortex that could explain its involvement in pathologies involving aberrant motivations. This work was recently published (Talpir and Livneh, Cell Reports, 2024).
In addition to these achievements, we sought to create a comprehensive analytical pipeline for detailed analyses of neuronal population activity patterns in insular cortex. To do so, we leveraged recent advances in unsupervised machine learning to study insular cortex population activity patterns (a.k.a. neuronal manifold) in mice performing goal-directed behaviours aimed to fulfil physiological needs. We found that the insular cortex activity manifold is remarkably consistent across different animals and under different physiological need states. Activity dynamics within the neuronal manifold were highly stereotyped during food or water rewards, enabling robust prediction of single-trial outcomes across different mice, and across various natural and artificial physiological needs. Comparing goal-directed behaviour with self-paced free consumption, we found that the stereotyped activity patterns reflect task-dependent goal-directed reward anticipation, and not licking, taste, or positive valence. These findings revealed a core computation in insular cortex that could explain its involvement in pathologies involving aberrant motivations. This work was recently published (Talpir and Livneh, Cell Reports, 2024).
Our achieving non-invasive optogenetic manipulation of gut signaling is beyond the current state-of-the-art. The current state-of-the-art is either using invasive optic fibres, or using less specific and long-acting chemogenetics. The non-invasive optogenetic capability allows us to have genetic and temporal precision of the manipulation.
Another way in which this achievement goes beyond the current state-of-the-art, is that we have been able to combine these systems with two-photon imaging of insular cortex activity, as well as fibre-photometry, in behaving mice. This required additional hardware and software developments. The current state-of-the-art is only to use genetic gut manipulations only with behaviour. Thus, our achievements open the opportunity to investigate neural representations of these internal stimuli and how they change with learning.
Another advancement beyond the state-of-the-art is establishing the ability to artificially activate precise activity patterns in insular cortex using two-photon holography and optogenetics via a microprism. Most work on insular cortex uses bulk manipulations like chemogenetics and optogenetics that lack spatial and temporal resolution. Our new advancement goes substantially beyond this by adding spatially and temporally precise manipulations to insular cortex activity. We are currently testing the network and behavioural effects of such precise manipulations.
Another way in which this achievement goes beyond the current state-of-the-art, is that we have been able to combine these systems with two-photon imaging of insular cortex activity, as well as fibre-photometry, in behaving mice. This required additional hardware and software developments. The current state-of-the-art is only to use genetic gut manipulations only with behaviour. Thus, our achievements open the opportunity to investigate neural representations of these internal stimuli and how they change with learning.
Another advancement beyond the state-of-the-art is establishing the ability to artificially activate precise activity patterns in insular cortex using two-photon holography and optogenetics via a microprism. Most work on insular cortex uses bulk manipulations like chemogenetics and optogenetics that lack spatial and temporal resolution. Our new advancement goes substantially beyond this by adding spatially and temporally precise manipulations to insular cortex activity. We are currently testing the network and behavioural effects of such precise manipulations.