Neuroscience Sensor-Motor Systems Vision Cerebellum Birds Brain Evolution
Our lab examines the neural basis of sensori-motor behaviours. We have studied all sensory systems, but the emphasis is on vision. The long term objectives of my research program are to provide a comprehensive description of: (a) the neuroanatomical connections in these sensori-motor systems; (b) the response properties of neurons to elucidate where, and which, sensory attributes are encoded; (c) the neurochemicals involved in these pathways to understand how these attributes are processed; and (d) the evolution of these pathways in relation to behaviour.
There are two major themes:
Neurophysiology, Neuroanatomy and Neurochemistry of Visual-Cerebellar Pathways
A major focus of my research concerns the neurophysiological basis of visual processing, in particular those parts of the brain involved in the processing of “optic flow” that results from self-motion. Because the world consists of stationary objects and surfaces, self-motion through the environment induces patterns of motion across the entire retina, known as optic flow. Optic flow provides a rich source of proprioceptive information, and can be used for several behaviors including determination of heading, control of posture and locomotion, perception of self-motion and navigation. Optic flow is analyzed by retinal-recipient nuclei in the brainstem, that project to the cerebellum, which is critical for motor control. Much of my work has shown that these projections form channels that are specialized for processing particular patterns of optic flow that result from either self-rotation or self-translation. These different optic flow neurons are topographically organized into parasagittal “zones”, typical of cerebellar organization. Our current work focuses on the neuroanatomical connections, neurochemistry, and functional response properties of these zones and how they are integrated with information from other sensory systems (vestibular and somatosensory).
Comparative Neuroanatomy and Brain Evolution
Much of this work is in collaboration with Dr. Andrew Iwaniuk, Lethbridge University. We have been fortunate to obtain a wealth of brains from over 160 different species of birds from numerous museums and private collectors. With these data were are analysing the size of various nuclei in the brain and attempting to correlate this with behavioural differences amongst various bird species. Again the focus is on sensory systems, but also brain evolution in relation to complex behaviors such as tool use.
A Specific example: The pretectal nucleis Lentiformis Mesencephali is Hypertrophied in Hummingbirds: I have been studying in the neuroanatomy and neurophysiology of the nucleus lentiformis mesencephali, or LM, for quite some time. We know that the LM is involved in the analysis of optic flow and the generation of the optomotor response to facilitate gaze stabilization. Dr. Iwaniuk and I examined variation within the LM in birds. Of all of the feeding methods known to occur in birds, hovering flight is perhaps the most demanding in terms of gaze stabilization. Hummingbirds and other hovering species (e.g., sunbirds, kingfishers, raptors) need to keep their vision stable in order to successfully feed. After examining the brains of several hummingbird species, we found that LM was significantly enlarged in hummingbirds compared to other birds. Other species that hover, such as the Eastern Spinebill (Acanthorhynchus tenuirostris), American Kestrel (Falco sparverius) and Belted Kingfisher (Ceryle alcyon) also had an enlarged LM, but not to the same extent as the hummingbirds. Thus, we concluded the LM became hypertrophy to meet the demands of hovering flight. This study led directly to work examining motion processing in the hummingbird LM with Dr. Doug Altshuler lab at UBC. We found that the hummingbird has unique response properties among birds.