1985 — 1991 |
Baker, James F |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Role of Cerebellar Nodulus and Uvula in Gaze Reflexes @ Northwestern University
This research program is studying the physiology of the ocular and neck reflexes that control gaze, and the specific role of the cerebellar nodulus and uvula in producing these reflexes. Gaze reflexes are necessary for clear vision because they steady the head and keep the eyes pointed in a constant direction as the head moves. Vision is poor and balance unstable without gaze reflexes. The cerebellum is critical to proper operation of gaze reflexes, but only the lateral vestibulocerebellum, or flocculus, has been extensively studied. The neural inputs and outputs of nodulus and uvula imply a vestibular function in gaze reflex control, yet most studies of cerebellar roles in gaze reflexes have neglected nodulus and uvula. Research during the firest three years of this research program has made important advances in describing properties of the gaze reflexes in which nodulus and uvula participate, documenting deficits in vestibulo-ocular and optokinetic gaze reflexes after nodulus-uvula lesions, and recording neuronal activity in nodulus and uvula. We will extend our findings in three areas and add a fourth area of emphasis. 1) We will continue to explore normal gaze reflexes, expanding our studies to include vestibulo-ocular responses to stimuli that especially excite nodulus-uvula neural activity. 2) We will further characterize simple spike responses of nodulus-uvula Purkinje cells, searching for properites that distinguish these cerebellar responses from other cerebellar response. We will also record nodulus-uvula neural activity during short term vestibular reflex adaptation procedures. 3) We will extend our studies of the effects of nodulus-uvula lesions on gaze reflexes and their adaptive capacity. 4) We will add recording and lesion studies that directly compare nodulus-uvula neural responses or lesions to those of cerebellar flocculus. This will test the hypothesis that nodulus and uvula participate primarily in ongoing gaze reflexes while flocculus functions primarily in adaptive control of gaze reflexes. The results of the proposed experiments will give us further insight into the functions of the cerebellum in motor behavior and the different roles of medial nodulus-uvula cerebellum and lateral cerebellar flocculus. We hope also for further insight into basic reflex functions, adaptation to disturbed sensory inputs, and recovery from neurological disorders caused by brain damage.
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1987 — 2005 |
Baker, James F |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Otolith Vestibulo-Ocular Reflex @ Northwestern University |
1 |
1992 — 2007 |
Baker, James F |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Otolith &Canal Signals in Vestibular-Neck Reflex System @ Northwestern University
The long range goal of the proposed research is to further our understanding of how the brain uses sensory information to guide body movements. To study this problem we have chosen the vestibular-neck reflex, which acts to stabilize the head on the body trunk. This reflex is understandably more complex than the well-understood vestibulo-ocular reflex that controls the eyes, but is a simpler sensory-motor system than the ones involved in general control of the limbs. Our approach is to extend to the vestibular-neck reflex the techniques of analysis of timing (dynamics) and spatial properties (3-dimensional directionality) that have been successfully applied to understanding vestibulo-ocular responses. The proposed experiments are directed toward three specific aims: 1. We will determine the relative contributions to the vestibular-neck reflex of the two vestibular signals relayed from the inner ear, the head rotation velocity signal carried by semicircular canal fibers and the head position or linear acceleration signal carried by the fibers from the otolithic maculae of the utricle and saccule. We expect canal signals to dominate for rapid motions and otolith signals to dominate for slower motions, with both the dynamics and spatial properties to differ for otolith versus canal signals, reflecting the different behavioral problems and mechanical loads faced for slow versus rapid head motions. 2. We will test the spatial properties and dynamics of otolith and canal components of the vestibular-neck reflex for the effects of factors such as a) sensory and motor deficits produced by plugging semicircular canals or selectively disabling major neck muscles, b) changes in head tilt with respect to gravity, and the posture of the head with respect to the body, and c) inactivation of the cerebellum. We expect to see greater adaptability and more pronounced context- specific responses for the vestibular-neck reflex than have been seen for the vestibulo-ocular reflex. 3. We will distinguish otolith and canal signals carried by vestibular- cervical neurons and explore the role of vestibular-cervical neurons in vestibular-neck reflex spatial properties, dynamics, and responses to factors listed above that affect the vestibular-neck reflex. We expect to find neurons that carry purely sensory signals and other neurons that carry adaptable or context-specific responses. We will test neurons for cerebellar input to see whether the cerebellum selectively influences neurons with adaptable and context-specific responses. We hope this research will expand our knowledge of sensory-motor neural systems. The results may ultimately be relevant to treatment of neurological or neuromuscular disease such as torticollis and oculomotor disorders, or neurological injury in general.
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1993 — 1997 |
Baker, James |
P60Activity Code Description: To support a multipurpose unit designed to bring together into a common focus divergent but related facilities within a given community. It may be based in a university or may involve other locally available resources, such as hospitals, computer facilities, regional centers, and primate colonies. It may include specialized centers, program projects and projects as integral components. Regardless of the facilities available to a program, it usually includes the following objectives: to foster biomedical research and development at both the fundamental and clinical levels; to initiate and expand community education, screening, and counseling programs; and to educate medical and allied health professionals concerning the problems of diagnosis and treatment of a specific disease. |
Core--Equipment @ Northwestern University
biomedical facility; biomedical equipment development;
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0.915 |
1997 — 2000 |
Baker, James F |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Otolith Vestibuloocular Reflex @ Northwestern University
The goal of the proposed research is to increase our understanding of the function of the vestibular otoliths in the vestibulo-ocular reflex (VOR). Semicircular canal and otolith signals are processed by vestibulo-ocular neurons and routed to the extraocular muscles to rotate the eyes in the direction opposite to head rotation. The vestibulo-ocular reflex thus maintains a constant direction of eyesight during head movement, as required for acute vision. Neural signals from the otoliths are especially important for gaze stability during vertical head movements. The proposed research will characterize vision-stabilizing eye movements produced by otoliths and explore underlying neuronal mechanisms in four series of experiments in squirrel monkeys, cats, and rats. (l) Vestibulo-Ocular Reflex during slow rotations: Eye movements and single vestibular neuron activity will be recorded during low frequency and constant velocity pitch vertical rotations in upright, on-side, and inverted head posture, to isolate vestibulo-ocular reflex signals related to otoliths. Neuronal and reflex eye movement signals will be classified as due to tilt stimulation or central nervous system estimation of head velocity. Neurons identified as projecting to extraocular muscle motor nuclei will be tested to determine whether. they carry selective components of the vestibulo-ocular reflex signal or overall motor commands. (2) Selective roles of anterior canal and otolith signals: Properties of identified brainstem vestibular nucleus neurons receiving primary input from anterior semicircular canals will be compared to those with posterior canal input, to determine if otolith-based velocity estimation signals are selectively present on anterior canal neurons and otolith-based tilt signals selectively present on posterior canal neurons. (3) Signal gating in vestibulo-ocular reflex neurons: Control of otolith signals participating in vestibular reflexes will be tested by recording vestibulo-ocular reflexes in responses to fore-aft linear motion, in monkeys gazing in different directions. Identified vestibular nucleus neurons will be classified as vestibular stimulus- linked or ocular reflex response-linked, depending on whether their responses are inverted when the ocular reflex direction is reversed with reversal of gaze direction. (4) Modeling tilt, estimator, and canal signals for vestibulo-ocular reflex: Results obtained under aims 1-3 will be incorporated in models of vestibular reflexes in an attempt to develop comprehensive models that accurately mimic vertical VOR responses. The results will add to our knowledge of gaze stability and may give insight into general brain mechanisms of sensory- motor systems.
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1997 — 2001 |
Baker, James F |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Otolith &Canal Signals in Vestibular/Neck Reflex System @ Northwestern University
DESCRIPTION: The goal of the proposed research is to understand the vestibulo-cervical reflex, also called the vestibulo-colic reflex (VCR). The neuronal circuitry of the VCR receives vestibular information from the semicircular canals and otoliths, and coordinates neck muscle contraction in response to vestibular stimuli. When the VCR is disabled the head wobbles rapidly and uncontrollably, demonstrating that one VCR function is to maintain head stability. Head and body righting reflexes are also disrupted by interruption of vestibular signals, suggesting that another VCR function is righting the head to maintain the usual upright posture. The proposed research to be done in squirrel monkeys and cats has two major hypotheses with corresponding experimental aims: 1. The Vestibulo-Cervical Reflex returns the head to the upright position: when the head is upright and intermediate frequencies of head motion are tested, a stabilizing VCR responses is observed. However, when the head is not upright and low frequencies are tested, responses can oppose head stability if such opposition would facilitate righting of the head. Neck muscle electromyographic activity and brainstem VCR neuron activity will be recorded during low-frequency head rotations in a variety of head postures to determine when stabilizing responses occur and when righting responses are elicited by head motion. 2. Vestibulo-Cervical Reflex signals can dominate vestibulo-ocular reflexes: Reflex eye movements will be recorded at the same time as neck muscle electromyographic and VCR neuron activity to determine if ocular reflexes are altered by the transition of VCR response from a stabilizing to righting function. Activity of neurons participating in both reflexes will be recorded to see which reflex dominates.
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