Biographical Sketch:
Education:
Dr. Eng. - University of Trieste, Trieste, Italy
Ph.D. - University of Trieste, Trieste, Italy
Clin. Eng - University of Trieste, Trieste, Italy
Administrative Responsibilities:
Member, SOFAC
Secondary Appointments:
Scientist, UAB Center for the Development of Functional Imaging
Associate Scientist, Vision Science Research Center
Personal:
With my wife Denise enjoying our shared love of history, literature, art, live theatre, and gardening.
Scholarly Activity:
Teaching:
VS212 "Normal Binocular Vision and Eye Movements".
This is a professional optometry course on the main concepts of binocular vision and on the different types of eye movements and their neural circuitry. Course Master.
Syllabus
VIS753/VIS754 "MRI for Biologists"
Graduate course on anatomical and functional magnetic resonance imaging. Starting for the physics of MRI, the course guides the students through types of sequences, safety issues, design of experiments, and data analysis. The course includes practice sessions on the 4.7 Tesla MRI system of the Center for the Development of Functional Imaging. Course Master.
Syllabus
VIS747 "Central Visual Pathways"
As part of this graduate course, I give seminars (6 hours) covering the neural and functional aspects of the vestibular and optokinetic systems, which purpose is to stabilize the images on the retina during movements of the head and/or the visual scene.
Syllabus
VIS744 "Ocular Anatomy, Physiology, and Biochemistry"
As part of this graduate course, I give seminars (4 hours) on the anatomy and physiology of the extraocular muscles, which drive the movements of the eyes in the orbit.
Syllabus
Research:
NEURAL ORGANIZATION OF EYE MOVEMENTS IN DEPTH
(NEI - NIH 1 R01 EY017283 and VSRC NEI/NIH Core Grant P30 EY-03039)
The horizontal position of the eyes in the head can be divided into two geometrically independent entities. The first is the cyclopean angle, which is the average sum of the horizontal angles of the two eyes with respect to the head. The second is the vergence angle, which is the difference of these two angles, or, in other words, the angle between the two eyes. Any horizontal position of the eyes can be computed as algebraic sum of those two contributions, with the vergence contribution adding to the cyclopean contribution in one eye and subtracting in the other eye. There is extensive evidence that the primate brain has developed separate mechanisms to control the cyclopean angle of the two eyes (conjugate systems) and the vergence angle (vergence system), preferring this solution to the independent control of the two eyes. In this view, known as Hering's law of equal innervation, both eyes receive the same conjugate and vergence commands, with the eyes always acting as a yoked pair. The outcome, from a geometrical point of view, is indistinguishable from each eye rotation being controlled independently. This view was recently challenged by the evidence of neural signals that are more consistent with at least partial monocular control of the two eyes.
The first goal of this project is to re-evaluate what "vergence" means in terms of oculomotor commands and develop more realistic models of the vergence system. How much of what we externally record as "vergence" eye movements, i.e., changes in the angle between the two eyes, is actually driven by the vergence system? How much "vergence" is, instead, the result of monocular asymmetric commands independently driving each eye? Furthermore, conjugate and vergence systems, while usually modeled as separate neural systems, are not independent. Another goal of this project is to precisely quantify these crossed interactions and to locate their neural sites in non-human primates by using standard electrophysiological techniques. Macaque monkeys have oculomotor systems which are almost identical to humans and are the preferred animal model for oculomotor studies. They can be trained to perform reliably quite complex videogames and, while functional magnetic resonance imaging is a non-invasive technique used also with humans, the precise quantification of the neuronal substrate can be achieved only with the direct recording with ultra-fine microelectrodes of the electrical activity at the level of the single neuron. This invasive technique can be used, with the exclusion of during human brain surgeries, only in animal models.
PLASTICITY OF PRIMATE BINOCULAR COORDINATION
(EyeSight Foundation of Alabama and VSRC NEI/NIH Core Grant P30 EY-03039)
Human and non-human primates have frontal eyes with a large visual overlap between the images on the two retinae. The primate brain can recognize when images on the two retinae are from the same object and merges them into a single percept: binocular fusion. Double vision, i.e., the inability to fuse the images from the two retinae of the same object due to abnormal binocular eye alignment is perhaps the most common neurological complain. More than 4% of the US population have abnormal binocular coordination, the most common being strabismus. Binocular coordination is also disrupted in subjects required to wear spectacles with large differences in the magnification factor between the two eyes (anisometropic spectacles) or prisms.
The oculomotor systems, responsible for the movements of the eyes, are highly adaptable, i.e., develop short-term and long-term changes in their responses when needed. Nonetheless, there are several cases where these compensatory mechanisms fail, strabismus being the most evident. This project is a 2-years pilot study seeking to identify where these adaptive limitations are by directly recording with microelectrodes the activity of neurons most likely involved in these compensatory processes. These processes are followed in the short-term (minutes and hours) and long-term (days and weeks) by having the subject wearing anisometropic spectacles, prisms, or by using customized stimuli simulating their optical effects. The experiments are conducted in macaques, which are the standard animal model for binocular coordination, fully developed only in primates.
The clinical importance of a better understanding of the neural mechanisms of binocular control and adaptation, and in particular the origin of their functional limits, is manifold, from a better understanding of the neurological source of a binocular abnormality to a better management of its treatment. Orthoptics is the clinical field where this knowledge would have the most direct impact, where the patients, mostly children, are asked to wear patches and optical devices to help the brain to adaptively correct for an abnormality in their binocular coordination. This approach is often tried as initial alternative to a surgery at the level of the extraoculomotor muscles to mechanically obtain a better eye alignment, or during post-surgical rehabilitation.
FUNCTIONAL MAGNETIC RESONANCE IMAGING OF SUBCORTICAL OCULOMOTOR AREAS IN PRIMATES (UAB Faculty Development Grant Program)
Subcortical (cerebellar, midbrain, and brainstem) anatomical and functional magnetic resonance imaging are much more challenging than cortical imaging. This is due 1) to motion artifacts caused by movements of the mouth, tongue, and temporal and neck muscles even in animals with rigid head posts; 2) the significant pulsating micro-movements of these brain areas caused by the basilar artery and other deep large vessels; and 3) the effects of the large amount of pulsating blood flow in these large vessels on the blood oxygen dependent response (BOLD) itself in the nearby micro-vasculature, physiological basis of functional MRI. The goal of this pilot study is to develop methodologies to reduce these artifacts in subcortical MRI/fMRI imaging in alert behaving non-human primates by: 1) designing customized saturation-based MRI sequences suppressing the MRI signals coming from the areas originating the motion artifacts; 2) evaluating the feasibility of the technique of cardiac gating, i.e., the acquisition of the MRI images in synchrony with the heart cycle; 3) evaluating the use of surface coils, alone or in association with a decoupled TEM head coil. This study is performed in alert macaque monkeys executing standard oculomotor tasks while in the 4.7 Tesla non-human primate 60 cm vertical bore magnet of the UAB Center for the Development of Functional Imaging. These subcortical areas also contain the neural substrates of the mechanisms responsible for the binocular coordination. The long-term goal is to apply the same optimized protocols in human oculomotor fMRI studies and then in clinical fMRI of strabismic patients as pre-surgery functional evaluation.
THE EFFECT OF SEDATION ON EYE MOVEMENTS
(PI: Dr. Michael A Froelich NIH-NCRR K23 RR021874 and GCRC M01RR-00032)
The function of the saccadic eye movements is to redirect as fast as possible the eyes from one element in the visual scene to another. Part of the saccadic circuitry is located in the brainstem and sedation is known to suppress brainstem activity. Not surprisingly, there is preliminary evidence in the literature that the level of sedation, by changing the level of brainstem activity, affects the latency and dynamics of saccades in a dose-dependent relationship. This study, in normal human volunteers, will evaluate the effects of propofol on the saccadic system. The main goal of the project is to determine if there is a clinically relevant correlation between the level of propofol sedation and saccadic responses and see if this methodology can be used as objective quantitative method to determine the level of sedation of the patient as alternative to classical pain level measures. Our laboratory is developing an integrated mobile human oculomotor station for this project and will be responsible for the development of the acquisition and analysis software, the recording of the oculomotor data, and the quantification of the results. Dr. Froelich, Associated Professor and Clinician Scientist of the Department of Anesthesiology of UAB will be responsible of the clinical aspects of the study.
Publications
Additional Information:
Busettini Laboratory