Neuroscience seminars

Gravity is a constant in our lives. It provides an internalized reference to which all other perceptions are related. We can experimentally manipulate the relationship between physical gravity with other cues to the direction of “up” using virtual reality - with either HMDs or specially built tilting environments - to explore how gravity contributes to perceptual judgements. The effect of gravity can also be cancelled by running experiments on the International Space Station in low Earth orbit. Changing orientation relative to gravity - or even just perceived orientation – affects your perception of how far away things are (they appear closer when supine or prone). Cancelling gravity altogether has a similar effect. Changing orientation also affects how much visual motion is needed to perceive a particular travel distance (you need less when supine or prone). Adapting to zero gravity has the opposite effect (you need more). These results will be discussed in terms of their practical consequences and the multisensory processes involved, in particular the response to visual-vestibular conflict.

Each spring, billions of Bogong moths escape hot conditions in different regions of southeast Australia by migrating over 1000 km to a limited number of cool caves in the Australian Alps, historically used for aestivating over the summer. At the beginning of autumn the same individuals make a return migration to their breeding grounds to reproduce and die. To steer migration Bogong moths sense the Earth’s magnetic field and correlate its directional information with visual cues. In this presentation, we will show that a critically important visual cue is the distribution of starlight within the austral night sky. By tethering spring and autumn migratory moths in a flight simulator, we found that under natural dorsally-projected night skies, and in a nulled magnetic field (disabling the magnetic sense), moths flew in their seasonally appropriate migratory directions, turning in the opposite direction when the night sky was rotated 180°. Visual interneurons in the moth’s optic lobe and central brain responded vigorously to identical sky rotations. Migrating Bogong moths thus use the starry night sky as a true compass to distinguish geographic cardinal directions, the first invertebrate known to do so. These stellar cues are likely reinforced by the Earth’s magnetic field to create a robust compass mechanism for long-distance nocturnal navigation.

Ultra-low-cost, easily implemented and flexible two-photon scanning microscopy modification offering a several-fold expanded three-dimensional field of view that also maintains single-cell resolution. Application of our system for imaging neuronal activity has been demonstrated on mice, zebrafish and fruit flies. Website: https://github.com/BadenLab/nTCscope

The study of altered states of consciousness has long had the potential to provide important insight into the nature of consciousness. In recent years there has been a resurgence of research and public interest in atypical or altered states of consciousness. These have focused both on conditions in which consciousness is considered to be impaired due to brain trauma or enhanced in some way through mediation practices or ingestion of psychedelics. The talk will begin with a brief overview of recent scientific approaches to understanding these different types of altered consciousness. The remainder of the talk will focus on lab-based experiments conducted by myself and others looking at the effects of serotoninergic hallucinogens (i.e. psilocybin and LSD) on perceptual and cognitive function. Together this body of research provides important new insights for the scientific study of consciousness and an initial understanding of the neuropharmacological mechanisms underlying conscious experience.

In this talk I’ll discuss translation of findings of multisensory facilitation of learning to cognitive training. I’ll first review some early findings of multisensory facilitation of learning and then discuss how we have been translating these basic science approaches into gamified training interventions to improve cognitive functions. I’ll touch on approaches to training vision, hearing and working memory that we are developing at the UCR Brain Game Center for Mental Fitness and Well-being. I look forward to discussing both the basic science but also the complexities of how to translate approaches from basic science into the more complex frameworks often used in interventions.

Obesity and neurodegeneration lead to millions of premature deaths each year and lack broadly effective treatments. Obesity is largely caused by the abnormal function of cell populations in the hypothalamus that regulate appetite. We have developed methods generate human hypothalamic neurons from hPSCs to study how they respond to nutrients and hormones (e.g. leptin) and how disease-associated mutations alter their function. Since human hypothalamic neurons can be produced in large numbers, are functionally responsive, have a human genome that can be readily edited, and are in culture environment that can be readily controlled, there is an unprecedented opportunity to study the genetic and environmental factors underlying obesity. In addition, we are fascinated by the fact that mid-life obesity is a risk factor for dementia later in life, and caloric restriction, exercise, and certain anti-obesity drugs are neuroprotective, suggesting that there are shared mechanisms between obesity and neurodegeneration. Studies of HPSC-derived hypothalamic neurons may help bridge the mechanistic gulf between human genetic data and organismic phenotypes, revealing new therapeutic targets. ​

The idea that behavior results from a dynamic interplay between automatic and controlled processing underlies much of decision science, but has also generated considerable controversy. In this talk, I will highlight behavioral and neural data showing how recently-developed computational models of decision making can be used to shed new light on whether, when, and how decisions result from distinct processes operating at different timescales. Across diverse domains ranging from altruism to risky choice biases and self-regulation, our work suggests that a model of prioritized attentional sampling and evidence accumulation may provide an alternative explanation for many phenomena previously interpreted as supporting dual process models of choice. However, I also show how some features of the model might be taken as support for specific aspects of dual-process models, providing a way to reconcile conflicting accounts and generating new predictions and insights along the way.

The cerebellum contains more than half of the brain’s neurons and it is essential for motor control. Its neural circuits have a distinctive architecture comprised of a large, sparse expansion from the input mossy fibres to the granule cell layer. For years, theories of how cerebellar architectural features relate to cerebellar function have been formulated. It has been shown that some of these features can facilitate pattern separation. However, these theories don’t consider the need for it to learn fast in order to control smooth and accurate movements. Here, we confront this gap. This talk will show that the expansion to the granule cell layer in the cerebellar cortex improves learning speed and performance in the context of motor control by considering a cerebellar-like network learning an internal model of a motor apparatus online. By expressing the general form of the learning rate for such a system, this talk will provide a calculation of how increasing the number of granule cells diminishes the effect of noise and increases the learning speed. The researchers propose that the particular architecture of cerebellar circuits modifies the geometry of the error function in a favourable way for learning faster. Their results illuminate a new link between cerebellar structure and function.

Dr. Rajan and her lab design neural network models based on experimental data, and reverse-engineer them to figure out how brain circuits function in health and disease. They recently developed a powerful framework for tracing neural paths across multiple brain regions— called Current-Based Decomposition (CURBD). This new approach enables the computation of excitatory and inhibitory input currents that drive a given neuron, aiding in the discovery of how entire populations of neurons behave across multiple interacting brain regions. Dr. Rajan’s team has applied this method to studying the neural underpinnings of behavior. As an example, when CURBD was applied to data gathered from an animal model often used to study depression- and anxiety-like behaviors (i.e., learned helplessness) the underlying biology driving adaptive and maladaptive behaviors in the face of stress was revealed. With this framework Dr. Rajan's team probes for mechanisms at work across brain regions that support both healthy and disease states-- as well as identify key divergences from multiple different nervous systems, including zebrafish, mice, non-human primates, and humans.

In this presentation, we will discuss the cellular and molecular properties of the retrotrapezoid nucleus (RTN), an integrative and interoceptive control node for the respiratory motor system. We will present the molecular profiling that has allowed definitive identification of a cluster of tonically active neurons that provide a requisite drive to the respiratory central pattern generator (CPG) and other pre-motor neurons. We will discuss the ionic basis for steady pacemaker-like firing, including by a large subthreshold oscillation; and for neuromodulatory influences on RTN activity, including by arousal state-dependent neurotransmitters and CO2/H+. The CO2/H+-dependent modulation of RTN excitability represents the sensory component of a homeostatic system by which the brain regulates breathing to maintain blood gases and tissue pH; it relies on two intrinsic molecular proton detectors, both a proton-activated G protein-coupled receptor (GPR4) and a proton-inhibited background K+ channel (TASK-2). We will also discuss downstream neurotransmitter signaling to the respiratory CPG, focusing especially on a newly-identified peptidergic modulation of the preBötzinger complex that becomes activated following birth and the initiation of air breathing. Finally, we will suggest how the cellular and molecular properties of RTN neurons identified in rodent models may contribute to understanding human respiratory disorders, such as congenital central hypoventilation syndrome (CCHS) and sudden infant death syndrome (SIDS).