This file was created by the Typo3 extension sevenpack version 0.7.14 --- Timezone: CEST Creation date: 2017-05-23 Creation time: 10-50-56 --- Number of references 7 article WallaceGSRNK2013 Rats maintain an overhead binocular field at the expense of constant fusion Nature 2013 6 498 7452 65–69 Fusing left and right eye images into a single view is dependent on precise ocular alignment, which relies on coordinated eye movements. During movements of the head this alignment is maintained by numerous reflexes. Although rodents share with other mammals the key components of eye movement control, the coordination of eye movements in freely moving rodents is unknown. Here we show that movements of the two eyes in freely moving rats differ fundamentally from the precisely controlled eye movements used by other mammals to maintain continuous binocular fusion. The observed eye movements serve to keep the visual fields of the two eyes continuously overlapping above the animal during free movement, but not continuously aligned. Overhead visual stimuli presented to rats freely exploring an open arena evoke an immediate shelter-seeking behaviour, but are ineffective when presented beside the arena. We suggest that continuously overlapping visual fields overhead would be of evolutionary benefit for predator detection by minimizing blind spots. Research Group Kerr Department Logothetis 10.1038/nature12153 dhwDJWallace davidDSGreenberg jsawJSawinski rullaSRulla gnotaroGNotaro jkerrJNDKerr article 6149 Visually evoked activity in cortical cells imaged in freely moving animals Proceedings of the National Academy of Sciences of the United States of America 2009 11 106 46 19557-19562 We describe a miniaturized head-mounted multiphoton microscope and its use for recording Ca2+ transients from the somata of layer 2/3 neurons in the visual cortex of awake, freely moving rats. Images contained up to 20 neurons and were stable enough to record continuously for >5 min per trial and 20 trials per imaging session, even as the animal was running at velocities of up to 0.6 m/s. Neuronal Ca2+ transients were readily detected, and responses to various static visual stimuli were observed during free movement on a running track. Neuronal activity was sparse and increased when the animal swept its gaze across a visual stimulus. Neurons showing preferential activation by specific stimuli were observed in freely moving animals. These results demonstrate that the multiphoton fiberscope is suitable for functional imaging in awake and freely moving animals. Research Group Kerr Biologische Kybernetik Max-Planck-Gesellschaft en 10.1073/pnas.0903680106 jsawJSawinski dhwDJWallace davidDSGreenberg SGrossmann WDenk jkerrJNDKerr poster RullaNMWSK2015 Two-photon imaging of neuronal populations in the primary visual cortex representation of the overhead visual field 2015 10 18 45 232.10 Rodents have a large binocular field of view that extends from the snout to over the animals head. Recent experiments have shown that rodents have a strong, innate, evasive behavior evoked exclusively by stimuli presented above them. However, little is known about the functional properties of cortical neurons that represent the overhead visual field. Here we describe a method for allowing direct optical recording from populations of neurons representing the overhead visual field. Firstly, the conventional microscope objective has been replaced with a periscope coupled to a miniature objective to facilitate placement of a stimulus monitor above the rat’s head. Secondly, we developed a method for presentation of visual stimuli on the OLED display of a tablet running the Android OS, and a camera-based method for calibrating the position of the stimulus display in relation to the animals head. Using this setup, we recorded in rats the activity of neurons in the representation of the overhead visual field of the primary visual cortex in response to a range of stimuli. Neurons were labeled with the calcium indicator OGB-1 with counterstaining of astrocytes using sulforhodamine 101. Stimuli were either an expanding or contracting looming dot, or a moving dot that moved at constant speed along multiple trajectories to cover all positions within the display. In both stimulus types, differing sets of foreground/background luminance were used. Preliminary results show that 19% of the neurons responded with clear and reproducible transients to the looming dot stimulus, and 30% were responsive to moving dot stimuli. The response profiles of neurons to different stimulus types and parameters were further analyzed in detail and compared between cortical areas and receptive field properties established for this cortical region. Chicago, IL, USA 45th Annual Meeting of the Society for Neuroscience (Neuroscience 2015) rullaSRulla benedictBNg jakobJMacke dhwDWallace jsawJSawinski jkerrJKerr poster SawinskiGWK2012 Combining ocular videography and 2-photon imaging in freely moving rats 2012 10 16 42 569.29 Accurately recording eye movements is essential to understanding how an animal moves its eyes to establish vision. Rodents are a commonly used as a model for the mammalian visual system, but it is not known how they move their eyes during free movement. We describe here a custom-built ocular videography system light enough to be carried_in combination with a head-mount two-photon microscope (Sawinski et al., 2009)on the head of a freely moving rat. Each camera, complete with mounting arm and infrared (IR) illumination weighs 1.8 g, with outer dimensions of the camera about 2.5×1×1 cm³. Rats comfortably carry 2 cameras, one recording the movements of each eye. The off-the-shelf monochrome camera chips (Aptina) are capable of recording 752×480 pixel images at a maximum frame rate of 60 Hz, and have a wide wavelength range which allows IR illumination. Using a 45° IR reflector that is transparent to visible light allows the cameras to be positioned in a way that minimizes disturbance to the animal’s visual field. The optics consist of a plano-convex lens (focal length f=9 mm) and a visible-light reflector. The lens is mounted in reverse orientation favoring a more planar image plane. The image size is 1.3×0.9 cm² at a working distance of about 1 cm. Inbuilt illumination from an IR LED (850nm) provides consistent image quality during normal exploratory behaviors and jumping. Image quality and resolution is good enough to identify the fine detail of the edge of the iris, which can be used for the detection of ocular torsion (rotation of the eye around the optical axis). Cabling is minimal, as the camera chip can be controlled with a two-wire serial interface and is able to transmit image data over a twisted pair using low-voltage differential signaling (LVDS). To reduce rotational stiffness we have built 2 m long custom cables by twisting enameled 50 µm dia. copper wires. While the wire resistance is less critical for LVDS signaling (even though the impedance is lower than required due to small wire separation) the voltage-level-wise sensitive two-wire serial communication required galvanic separation of the ground connection of the mobile cameras power supply and the external signal decoding board. The signals are then decoded on a custom-built decoding board using a standard LVDS deserializer (12bit) and an additional two-wire serial bus buffer. Signals are then transmitted via a USB interface. In combination with the miniature two-photon microscope, the eye-cameras are deployed in combination with a fully optical head-orientation detection system consisting of 6 IR LEDs mounted on the animal’s head with the miniaturized cameras, and a set of 4 external overhead cameras. Research Group Kerr Department Logothetis New Orleans, LA, USA 42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012) jsawJSawinski davidDSGreenberg dhwDJWallace jkerrJKerr poster WallaceSGNRK2012 Eye movements in rats maintain an overhead binocular field at the expense of binocular fusion 2012 10 16 42 569.28 How much does an unrestrained rat move its eyes, and what are the characteristics of these movements? Though many elements of rat vision have been well studied, such as their perception of depth and color, their visual acuity, and the physiology of neurons in the retina, thalamus and visual cortex, this essential element in understanding their visual sense has not been studied to date in unrestrained animals. To study this aspect of rat vision, we recorded eye movements in freely moving rats using a custom-built miniaturized ocular-videography system. A large fraction of the movements were found to be disconjugate and not consistent with the maintenance of a common point of fixation for both eyes, with the line of gaze of the two eyes regularly pointing in substantially different directions. Saccade-like conjugate movements, while forming the majority of movements seen in head-restrained animals, were only a small fraction of the movements observed in unrestrained animals. The asymmetrical movements of the two eyes implies substantial variability in the correspondence of the left and right eye images, and this, together with the lack of a common point of fixation for both eyes, precludes binocular fusion (fusion of left and right eye images into a single visual percept) and stereoscopic binocular vision using the mechanism described for other animals such as cats and primates. Movements of the two eyes were continuous while the animal was moving, but reduced to near stationary when the animal stopped moving its head, reflecting the strong influence of the vestibulo-ocular system in the rat. Horizontal movements of the eyes (movements in the rostral-caudal axis) were strongly related to head pitch, nose up pitch resulting in convergent movements of the two eyes and nose down pitch divergent movements. Vertical movements were strongly related to head roll, with roll to the right resulting in dorsally-directed movement of the right eye and ventrally directed movement of the left. Combined analysis of eye and head movements showed that the eye movements stabilize the animal’s horizon by moving and rotating the eyes in a way that counteracts the perturbations of the orientation of the horizontal axis of the retina caused by movements of the head. In addition, these movements also keep the visual fields of the two eyes strongly overlapping above the animal the vast majority of the time, which may be of substantial evolutionary benefit for a small ground dwelling animal. We suggest that the selective pressure on the rat has led to its visual system being rather more specialized to maximize overhead surveillance at the expense of binocular fusion and stereoscopic vision. Research Group Kerr Department Logothetis New Orleans, LA, USA 42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012) dhwDJWallace jsawJSawinski davidDSGreenberg gnotaroGNotaro rullaSRulla jkerrJNDKerr poster GreenbergWSNRK2012 Optical tracking of head movements, eye movements and ocular torsion incorporated into a miniaturized two-photon microscope 2012 10 16 42 569.27 The miniaturized two photon (2P) microscope or ‘fiberscope’ allows imaging during free movement, requiring continuous tracking of the head and eyes to determine visual input. We developed a 2P-compatible, all-optical system for head and eye tracking in rodents. Head tracking with 6 DOF employed infrared LEDs mounted on the microscope and imaged by multiple overhead cameras, while miniaturized camera systems with specialized, custom-built optics and electronics were used to image the eyes (see accompanying poster for details). Calibration procedures based on the Tsai camera model realistically incorporated radial lens distortion, and for custom-built camera systems decentering and thin-prism distortions as well. To detect eye movements, we directly compared 3D geometric models of the eye and pupil to each observed image, minimizing an objective function over eye rotation angles and pupil dilation radii. We found that this approach, which detected the 2D pupil boundary and 3D eye rotation simultaneously in a single step, was more robust than previous methods with an intermediate stage of 2D feature detection, allowing our system to operate effectively at lower contrast. Since the pupil-iris boundary deviated slightly from a perfect circle, with an uneven, crenellated appearance on a fine spatial scale, we also detected ocular torsion by measuring rotation of this rough boundary through 3D space. The eye tracker was self-calibrating in that animals were not required to fixate a presented target, aiding the use of this system in rodents where such training is impossible. Finally, based on the appearance of the eyeball-eyelid boundary we defined anatomically based coordinate axes and baseline pupil positions that were consistent across animals, even when the location and orientation of eye tracking cameras varied. Together, these tracking systems and analysis methods allowed stimulus presentation monitors and other environmental features to be mapped continuously onto each pupil plane, and gaze vectors for each eye to be projected into the animal’s environment. Research Group Kerr Department Logothetis New Orleans, LA, USA 42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012) davidDSGreenberg dhwDWallace jsawJSawinski gnotaroGNotaro rullaSRulla jkerrJNDKerr poster SawinskiWGGDK2009 Two-photon imaging of neuronal populations in the visual cortex of freely-moving animals 2009 10 39 353.11 While the neuronal basis of certain behaviors and sensory modalities can be studied under anesthesia or head-fixation, the full gamut of neural activity and its functions is accessible only in awake and unrestrained animals. We therefore developed a miniaturized, head mounted 2-photon microscope or “fiberscope” capable of resolving functional action-potential derived fluorescent signals from individual cortical cells. Using the fiberscope, we imaged spontaneous and stimulus-evoked activity from populations of layer 2/3 neurons and astrocytes in the visual cortex in both anesthetized and freely moving rats. The fiberscope weighs 5.5 g, and employs a custom-designed water immersion lens and a non-resonant fiber scanner leveraged by a piezo-element. Excitation light is delivered to the mobile animal through a single-mode optical fiber. Emitted light is collected through a plastic optical fiber before being split into a green channel, for the calcium-indicator Oregon Green BAPTA-1 (OGB1), and a red channel for the specific astrocyte marker sulforhodamin-101. Images acquired through the fiberscope were stable through a range of behaviors, even when the animal is moving vigorously (> 0.6 m/s). Using optical intrinsic imaging to locate the visual cortex binocular region, OGB1 was bulk loaded into cells within this region and remained viable over the course of the four hour experiments. Movement-based artifacts were small and could be successfully corrected offline using custom built software. Fiberscope imaging of neurons under anesthesia revealed robust stimulus responses and orientation selectivity. For imaging in freely-moving animals, the rat was allowed to run in a rectangular arena with one wall made of transparent Perspex behind which static visual stimuli were presented on a CRT monitor. Imaging sessions were run in darkness and recorded using infra-red videography. Transients could be observed in a subgroup of cells in response to activation of the visual stimulus. Further, movements of the animal which resulted in the stimulus sweeping through the animals visual field also evoked transients in a subgroup of the imaged cells. Thus, the miniaturized two-photon fiberscope can record spontaneous and stimulus-evoked Ca2+ transients in freely moving animals. We expect that the fiberscope will facilitate the study of neuronal population activity of during complex behavioral tasks. Research Group Kerr Department Logothetis Chicago, IL, USA 39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009) jsawJSawinski dhwDJWallace davidDSGreenberg SGrossmann WDenk jkerrJNDKerr