Imaging and modulation of neural activity in vivo: from the eye to the brain

33rd Biennial Symposium
August 15-17, 2024
Memorial Art Gallery

Thursday, August 15, 2024

8:30am – 9:20am: Opening Keynote: Jose Alain Sahel, University of Pittsburgh
From photoreceptor neuroprotection to vision restoration : translational challenges

9:20am – 12:30pm: Calcium imaging in the living eye and brain

  • Adriana Di Polo, University of Montreal Hospital Research Center
  • Phil Williams, Washington University in St. Louis
    Homeostatic calcium imaging in the mouse retina with FRET based biosensors
  • Contributed Talk I
  • Coffee break
  • Ben Scholl, University of Colorado Denver
    Synaptic architecture and functional connectivity of ferret visual cortex
    Elucidating the functional connectivity between cortical neurons in the primary visual cortex (V1) remains a pivotal challenge, particularly in understanding how selective visual responses emerge from myriad synaptic inputs. Here we aim to identify the principles of functional connectivity within layer 2/3 of ferret V1, building upon previous work in mouse and classical work in carnivores and primates. Our central hypothesis posits that inter-columnar connections follow the functional similarity principles observed in mouse V1 and are essential for feature selectivity. To test this hypothesis, we used an all-optical interrogation approach to perturb and map excitatory and inhibitory neuronal interactions within and between orientation columns. Specifically, our experiments test hypotheses about the spatial profile of excitatory connectivity, the functional specificity of inhibitory interneurons, and the dynamic recruitment of functional connections. Overall our research aims to uncover novel computational circuit motifs in ferret V1, advancing our understanding of cortical circuits and informing the development of brain-inspired artificial intelligence.
  • Juliette McGregor, University of Rochester
    Adaptive optics calcium imaging in the primate eye: a tool for regenerative therapies
  • Contributed Talk II
  • Panel Discussion

12:30pm - 2:30pm: Lunch Break (offsite) & Meet the Experts Lunch (for participating trainees)

2:30pm – 5:40pm: Optogenetic modulation of activity in the eye and brain in vivo

  • Kuan Hong Wang, University of Rochester
    Cell-type and Projection-specific Optogenetic Tools for Marmosets
    A fundamental challenge in neuroscience is to understand the functional architecture of brain circuits. Selective targeting of neural circuits for optogenetic investigation has been well established in transgenic mice and fueled rapid research progress in mouse brain. However, comparable methods in non-human primates (NHPs) have been limited due to the lack of transgenic lines. While viral approaches in NHPs using AAV’s to deliver opsins reliably produce expression in cerebral cortex, targeting specific cell classes is challenging. Without targeting specificity, optogenetic manipulations in complex neural networks may produce effects that are difficult to interpret or weak. In collaboration with Jude Mitchell’s laboratory, our recent research has shown that there is a unique opportunity in NHP models to achieve greater specificity in optogenetic manipulations by targeting projection pathways. Specifically, we have applied a retrograde intersectional viral labeling method that we previously established in mice to the marmoset monkey. This method relies on an efficient retrograde virus to target specific populations of neurons based on their project patterns, and a two-vector Cre-recombinase-based intersectional strategy to ensure pathway-direction specificity in reciprocally connected circuits. With this approach, we have demonstrated specific labeling in multiple cortico-cortical projection pathways, as well as optogenetic activation and inhibition of labeled neurons in selected pathways. These methods will provide a general tool that can be applied to investigate the functional roles of selected projection pathways between primate brain areas and ultimately contribute towards our understanding of the functional architecture of primate brain.
  • Arash Afraz, National Institute of Mental Health
    Navigating the perceptual space with neural perturbations
  • Contributed Talk I
  • Coffee break
  • Greg Horwitz, University of Washington
    Optogenetic perturbation of saccades
    Accurate saccades require the concerted activity of a variety of neuronal types across a variety of brain structures. Much of what we know about this activity-behavior relationship was obtained through classical experimental perturbations: electrical stimulation and pharmacological inactivation. While powerful, these techniques leave technical gaps that optogenetics may help to fill. Unlike their classical counterparts, optogenetic techniques can be used to achieve fast, reversible inactivation and, at least in some cases, can be targeted to specific neuronal subtypes. In this talk, I will report on experiments in which cell-type specific optogenetics was used to manipulate the saccadic system of rhesus monkeys. The stereotypy of primate saccades and the precision with which eye position can be measured allow important questions to be answered despite small effect sizes. They also provide a sensitive platform for the development of optogenetic approaches for the control of primate behavior more broadly.
  • Farran Briggs, University of Rochester
    Optogenetic manipulations of corticothalamic circuits
    Although much is known about transformations in visual information that occur in feedforward circuits connecting the retina to the visual thalamus (the dorsal lateral geniculate nucleus or LGN) to the primary visual cortex (V1), relatively little is known about the functional contributions of the first feedback circuits in the visual system, corticogeniculate circuits. Corticogeniculate neurons provide an anatomically robust, but physiologically weak or modulatory input onto relay neurons in the LGN. In spite of decades of study, the function of corticogeniculate feedback in visual perception has remained a stubborn puzzle. Our goal is to resolve this puzzle using methods to selectively and reversibly manipulate corticogeniculate neurons in highly visual animal models. We have demonstrated that corticogeniculate neurons in carnivores and primates are physiologically and morphologically distinct and organized into parallel processing streams that match the feedforward parallel streams present in these species. Furthermore, using a virus-mediated gene-delivery strategy and optogenetics, we show that corticogeniculate feedback improves the temporal precision of LGN neuronal responses to visual stimuli, as well as the spatial resolution of some LGN neuronal responses, in carnivores and primates. Improvements in temporal precision are accompanied by reductions in LGN neuronal response variability and increases in the information coding capacity of LGN neurons when corticogeniculate feedback is optogenetically enhanced. Our current work is aimed at further examining corticogeniculate influence on LGN activity during visual behavior and employing novel methods such as functional ultrasound imaging combined with optogenetics to explore the influence of corticogeniculate feedback on population responses in the LGN.
  • Contributed Talk II
  • Panel Discussion

6:00pm – 9:00pm: Reception at the Eastman Museum

Friday, August 16, 2024

8:30am – 12:10pm: Label-free methods to study neural function in the eye and brain
Sponsored by The Del Monte Institute for Neuroscience

  • Omar Mahroo, Moorfields Eye Hospital/University College London
  • Dierck Hillman, Vrije University, Amsterdam
    Holographic Optical Coherence Tomography and its application for functional imaging of the retina
    Holographic Optical Coherence Tomography (OCT) enables three-dimensional imaging of the human retina at unprecedented speed by fully parallelizing the data acquisition. This technology captures both amplitude and phase information without uncorrectable motion artifacts, enabling computational adaptive optics and high-resolution imaging that can resolve individual cones in the living human eye. In addition, the phase information can be used to detect the function of vision-related cells by observing stimulation-induced phase changes of OCT light backscattered from retinal layers. We provide an overview of holographic OCT and its applications for optoretinography, i.e., all-optical label-free functional imaging, especially of the photoreceptors and inner retina, highlighting its unique features and capabilities.
  • Coffee break
  • Stefan Everling, Western University
    Functional Magnetic Resonance Imaging in Marmosets
    The common marmoset (Callithrix jacchus) has recently seen a significant increase in its use in biomedical research worldwide. It is fast emerging as a prominent keystone in biomedical nonhuman primate (NHP) model species. The marmoset stands out for neurophysiological and imaging studies because of its lissencephalic (smooth) cortex. This feature makes it ideal for electrode array implantations, laminar recordings, and optical recordings.

    A pivotal step in promoting marmosets as a viable experimental NHP model for studying human brain functions and dysfunctions is to map the marmoset brain and compare its architecture to that of the human brain. Over the past eight years, my laboratory has employed whole-brain functional magnetic resonance imaging (fMRI) to achieve this mapping. We began with resting-state fMRI experiments on anesthetized animals. Subsequently, we transitioned to awake resting-state fMRI experiments and currently, we conduct task-based fMRI experiments at ultra-high magnetic fields.

    Recently, our research using fMRI has facilitated the mapping of various brain functions in marmosets, including action observation, face processing, theory-of-mind, and vocalization processing. In my talk, I will present new data from movie-driven fMRI (md-fMRI) that has enabled us to identify large-scale networks in marmosets that are putative functional homologues of various human brain networks.
  • Theresa Desrochers, Brown University
    Cognitive Sequences: Parallel Cross-Species Dynamics in Frontal Neocortex
    Sequential tasks are an integral component of the daily lives of humans and other species. These sequences are multifaceted such that they can contain a set of abstract tasks (e.g., when making a meal: cut vegetables, heat the pan) that are independent from the precise motor actions needed to carry them out, and can also include a series of the precise muscle contractions needed to produce a motor sequence (e.g., picking a fruit off a tree). Presumably, processes control at the abstract level and keep track or monitor progress throughout sequences. Despite this presumption, the vast majority of studies that have studied sequences have focused on motor actions (e.g., a series of joystick movements, eye movements, or finger taps) while neglecting the control and sequential monitoring processes that occur simultaneously. We have made progress in understanding the neural bases of nonmotor sequential tasks across human and nonhuman primates. Using fMRI and transcranial magnetic stimulation (TMS) in humans and awake fMRI in nonhuman primates, we show that the lateral prefrontal cortex represents sequential information across sequence types and species. Further, these representations share a common dynamic, increasing activity across individual sequences (“ramping”). New studies are focusing on investigating these dynamics during using fMRI-guided electrophysiological recordings. Together these studies provide a unique view of complex cognitive processes across species, step towards understanding functional homology, and provide insight into sequential processes during health and disorder.
  • Contributed Talk I
  • Contributed Talk II
  • Panel Discussion

12:10pm - 2:00pm: Lunch Break (offsite) & Meet the Experts Lunch (in Parlor for participating trainees)

2:00pm - 2:45pm: Workshop 1: One-on-one mentoring

2:45pm - 5:00pm: Poster session and trade show for exhibitors

6:00pm – 8:30pm: Conference dinner

Saturday, August 17, 2024

8:30am – 12:10pm: New developments: hardware and data analysis

  • Na Ji, University of California Berkeley
    Imaging visual processing at high spatiotemporal resolution
    To understand computation underlying visual processing in the brain, one needs to understand the input-output relationships for neural circuits and the anatomical and functional properties of individual neurons therein. Optical microscopy has emerged as an ideal tool in this quest, as it is capable of recording the activity of neurons distributed over millimeter dimensions with sub-micron spatial resolution. I will describe how we use concepts in astronomy and optics to develop next-generation microscopy methods for imaging visual processing at higher resolution, greater depth, and faster speed. By shaping the wavefront of the light, we have achieved synapse-level spatial resolution through the entire depth of the primary visual cortex, as well as developed video-rate volumetric and kilohertz voltage imaging methods. We apply these methods to understanding visual processing using the mouse brain as our model system.
  • Jacob Robinson, Baylor College of Medicine
  • Contributed Talk I
  • Coffee break
  • Azadeh Yazdan-Shahmorad, University of Washington
    Engineering Plasticity in primate cortex using optogenetics
    The brain shows marked plasticity across a variety of learning and memory tasks as well as during recovery after injury. Many have proposed to leverage this innate plasticity using brain stimulation to treat neural disorders. Implementing such treatments requires advanced engineering tools and a thorough understanding of how stimulation-induced plasticity drives changes in network dynamics and connectivity at a large scale and across multiple brain areas. In this talk, I will present my lab's efforts to investigate targeted stimulation of primate cortex to drive cortical plasticity towards functional recovery. We have developed large-scale interfaces consisting of state-of-the-art electrophysiology and optogenetics to simultaneously record and manipulate activity from about 5 cm2 of cortex in awake behaving macaques. Using this interface, for the first time, we have shown the feasibility of inducing targeted changes in sensorimotor networks using optogenetics. Furthermore, we have incorporated the capability of producing ischemic lesions in the same interface enabling us to stimulate the cortex around the site of injury and monitor functional recovery via changes in blood flow, neurophysiology, and behavior. Currently we are using these technologies towards developing therapeutic interventions for neurological disorders such as stroke.
  • Anne Draelos, University of Michigan
    Real-time machine learning for optimizing neural stimulation
    Neuroscience is now tackling higher-dimensional spaces as we record from larger neural populations, examine richer behavioral repertoires, and place animals in more complex visual environments. Combined with precise stimulation technologies, we can begin to dissect large-scale circuits in vivo, constructing models that causally relate neural activity to behavior. Perturbative testing of hypothesized brain-behavior links, however, requires statistically efficient methods for both estimating and intervening on neural activity in response to visual stimuli in real time. Here I will discuss a few ways in which we can construct and refine models built in real-time, as neural or behavioral data are acquired, and use them to ‘close the loop’ and determine the optimal next stimulus to present or neuronal perturbation to apply. We demonstrate these methods in simulation and in real-time experiments studying the optomotor response in larval zebrafish with calcium fluorescence imaging.
  • Contributed Talk II
  • Panel Discussion
  • Coffee break

12:00pm – 12:45pm: Workshop 2: Diversifying your team

12:45am – 1:50pm: Lunch break (provided) & Meet the Experts Lunch (for participating trainees)

1:50pm – 5:00pm: New developments: viral vectors, promoters, sensors and actuators

  • Boris Zemmelman, University of Texas Austin
  • Ute Hochgeschwender, Central Michigan University
    Sensing, Controlling and Integrating Brain Processes with Biological Light
    Biological light, bioluminescence, is light emitted when a luciferase enzyme oxidizes its small molecule luciferin. Bioluminescence served in a non-invasive approach for imaging cells in living small animals for decades. More recently, engineered split luciferases made light emission dependent on intracellular calcium levels, thus allowing in vivo bioluminescence imaging of the activity state of neurons. Combining light emitting proteins with light sensing elements transformed bioluminescence from a mere imaging tool to a versatile platform for sensing, controlling, and integrating neural activity. Photons generated by the luciferase-luciferin interaction can activate a plethora of photoreceptors, including light sensing ion channels and transcription factors. When the luciferase is tethered to an opsin in a luminescent opsin, or luminopsin (LMO), light emitted from the luciferase leads to a change in the cell’s membrane potential through activation of a channelrhodopsin. LMOs provide a bimodal tool, allowing either chemo- (luciferin) or opto- (LED) -genetic access to the same cell. When a calcium-dependent luciferase is used to control activation of opsins or transcription factors, light emission directly reflects the state of the neuron that in turn can be integrated into changes in membrane potential or transcription. As both light emitter and light sensor are genetically encoded, they can be expressed in different cells. If they are expressed in synaptically connected neurons, this Interluminescence functions as a real-time optical synapse changing the valence of neural communication towards enhancing or dampening endogenous drive. Taken together, biolight enables a versatile tool platform for functional dissection of brain circuits.
  • Contributed Talk I
  • Coffee break
  • Contributed Talk II
  • Shannon Boye, University of Florida
    Development of AAV vectors for selective targeting of retinal cells in non-human primate
    A major focus of my research program is to identify AAV vectors for safe and efficient transduction of the human retina. We focus heavily on macaque as the major hurdles to transduction are only recapitulated in the intact eyes of animals with a fully functioning immune system, and ocular characteristics similar to humans. This talk will summarize efforts to identify AAVs suited for transduction of NHP retina via multiple routes of administration. Intravitreal injection (IVtI) is a promising delivery route for treating fragile retinas that are prone to additional damage upon surgical detachment but requires an AAV capable of ‘penetrating’ through the retina from the vitreous. We developed a method to generate sortable retinal cell populations in macaque which enabled screening of a highly complex AAV2-based capsid library and identification of variants capable of efficient retinal transduction and evasion of neutralizing antibodies following IVtI. Targeting of the outer retina (photoreceptors/RPE) is most effectively achieved via subretinal injection (SRI). However, benchmark AAV vectors only transduce cells within the region of the bleb (the part of the retina that is detached during surgery). We identified novel capsids with the ability to laterally spread beyond the margins of the SRI blebs, thereby enabling 1) safe and efficient transduction of foveal cones without the need to detach this precious retinal region and 2) a wider expanse of therapeutic gene delivery. These novel capsids can be used in both translational/therapeutic settings, or to ask basic science questions about retinal circuitry in a clinically relevant species.
  • Panel Discussion

Note: Trade show and posters remain accessible for every coffee and lunch break.