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About Sickkids
About SickKids

Robert V. Harrison, B.Sc (Hons), PhD, D.Sc.

The Hospital for Sick Children
Director of the Auditory Science Laboratory
Otolaryngology – Head and Neck Surgery

Research Institute
Senior Scientist
Neurosciences & Mental Health

University of Toronto
Professor and Vice-Chair - Research
Department of Otolaryngology - Head and Neck Surgery

Professor
Department of Physiology

Professor
Institute of Medical Science (IMS)

Professor
Institute of Biomaterials & Biomedical Engineering (IBBME)

Member
School of Graduate Studies (SGS)

Member
Faculty of Music

Member
Academic Board of the University of Toronto


Email: rvh@sickkids.ca

For more information, visit:

Auditory Science Lab

Brief Biography

Dr. Bob Harrison has basic training in physiology, with PhD and D.Sc. (Doctor of Science) degrees in auditory neuroscience. He has carried out research with groups in England, Germany, Japan, Sweden, France, the Netherlands and most recently in Canada and the U.S.

Harrison’s early research work was concerned with the peripheral auditory system, including studies on the effects of cochlear haircell damage on the transduction and coding of sound. More recently, he has been exploring the functional and anatomical development of central auditory pathways, particularly the plasticity of auditory cortex. He has employed wide range of research methodologies including electrophysiology, histology, electron microscopy, behavioural psychophysics, and various neuro-imaging techniques.

In addition to laboratory research, Harrison is involved in applied/clinical research including evoked potential and otoacoustic emission studies, and behavioural studies of speech and language development in children with cochlear implants. He has worked on several animal models of deafness including Meniere’s disease, auditory neuropathy, ototoxic drug induced hearing loss, acoustic trauma, age-related hearing loss and cytomegalovirus (CMV) ear infection. His work has been published in over 180 full, peer-reviewed papers and numerous book chapters.

Presently, Harrison is a Senior Scientist and Director of the Auditory Science Laboratory in the Research Institute at SickKids. He is Professor and Vice-Chair – Research, Department of Otolaryngology – Head and Neck Surgery at the University of Toronto and he is also a Professor in the Department of Physiology, the Institute of Medical Science and the Institute of Biomaterials and Biomedical Engineering, and a full member of the School of Graduate Studies.

Research Interests

Normal hearing and auditory brain development: 
In my laboratory we use a wide range of research techniques to investigate the structure and function of the normal auditory system (asking the question: How do we normally hear?) Our studies focus both on the “mature” system, and on early developmental processes that form the auditory brain.

The causes and consequences of hearing loss: 
We examine many different factors that can cause hearing loss, and determine what structural and functional changes occur to the inner ear and the central auditory brain.

My research mission: 
To increase our knowledge of the complex biological mechanisms that allow us to hear the world. With new insights, we work to prevent hearing loss and to promote normal auditory system development. For those with hearing loss, we strive to understand the exact nature of hearing deficits, and use this information towards achieving the best possible strategies for remediation and/or the planning of habilitation.

Research Activities

We investigate the structure and function of the normal auditory system using a wide range of methods. We also study the normal and abnormally developing auditory brain.

STRUCTURE:
To examine the anatomy and/or morphology of the inner ear structures we use techniques such as standard medical imaging (CT scans), scanning electron microscopy, as well as other light microscopy methods. For studies on central auditory brain structure also use various imaging methods including light and electron microscopy. These are most often combined with specialized histological preparation methods, such as corrosion casting (to look at cerebral or inner ear vasculature, neural tracers or immuno-histochemical labeling of active nerve cells (e.g. c-fos staining).

FUNCTION:
To probe the function of the auditory system, we employ numerous methods. With human subjects we use standard behavioural measures of hearing function, such as clinical audiogram measures and basic speech understanding tests.  We also can use a range of objective measures of hearing function such as electrophysiological evoked potentials (e.g. auditory brainstem evoked responses), or functional neuro-imaging based on magnetic signals generated by the auditory brain (MEG show diagram). 

To probe the function of the inner ear and peripheral auditory system, we use otoacoustic emission testing. Otoacoustic emissions (OAEs) can indicate the functional condition of cochlear haircells. We can combine OAEs with acoustic stimulation to probe some aspects of how the ear is controlled from the more central auditory brain. The methods mentioned so far are relatively non-invasive and safe to use on human subjects.

In more basic science investigations (in animal models) we use many of the techniques already outlined above. We can also use more invasive methods, such as microelectrode recordings of single neurons, or small groups of brain cells as they respond to sound stimulation. We routinely observe cells in the auditory midbrain and cortex to examine how individual cells code sound information. By recording cells from a range of positions within auditory areas we can obtain functional maps within the auditory brain.

ANIMAL MODELS OF HEARING LOSS:
We have developed or used animal models of Meniere’s disease, auditory neuropathy spectrum disorder, ototoxic drug induced hearing loss, acoustic trauma, age related hearing loss, cytomegalovirus (CMV) ear infection. We are also to determine how the auditory system fails in various types of hearing loss and deafness and explore what diseases, drugs or other factors (e.g. noise exposure levels) can damage the ears and cause hearing loss. After producing these "animal models" of hearing loss, we can use our functional tools to investigate the functional consequence of cochlear damage.

THE DEVELOPMENT AND PLASTICITY OF THE AUDITORY BRAIN:
We also use our various research tools to follow auditory development. We can compare the function of auditory areas in the neonatal brain with the adult animal to track developmental changes. We have investigated the central auditory effects of a cochlear hearing loss in a young developing subject compared with giving the same cochlear hearing loss to a mature subject. In this way we have been able to probe the plasticity of the auditory brain and particularly how early sensory experience can influence the formation of the auditory brain.

Publications

Some recent important scientific publications of Dr. Harrison’s include:

Harrison RV. (2014) On the biological plausibility of wind turbine syndrome. Int J Environ Health Res. 2014 Oct 8:1-6. [Epub ahead of print]  PMID: 25295915

D’Alessandro L, Harrison RV. (2014) Excitatory and inhibitory tonotopic bands in chinchilla inferior colliculus revealed by c-fos immuno-labeling. Hear Res Oct; 316:122-8. doi: 0.1016/j.heares.2014.07.010. Epub 2014 Aug 23. PMID: 25158304  

Negandhi J, Harrison AL, Allemang C, Harrison RV. (2014) The time course of cochlear injury discharge (excitotoxicity) determined by ABR monitoring of the contralateral cochlear events. Hear Res 26;315C:34-39. doi: 10.1016/j.heares. 2014.06.002.

Konomi U, Harrison RV, Kanotra S, James A. (2014) Age related changes to the dynamics of contralateral DPOAE suppression human subjects. J Otolaryngol Head Neck Surg. 2014 Jun 16;43:15. doi: 10.1186/1916-0216-43-15.

Grande G, Negandhi J, Harrison RV, Wang L-W. (2014). Remodeling at the calyx of Held-MNTB synapse in mice developing with unilateral conductive hearing loss. J Physiol. 2014 Apr 1;592(Pt 7):1581-600. doi: 10.1113/jphysiol. 2013.268839.

Papsin E, Harrison AL, Carraro M, Harrison RV. (2014) Contralateral ear occlusion for improving the reliability of otoacoustic emission screening tests. Int J Otolaryngol. 2014;2014:248187. doi: 10.1155/2014/248187.

Wolter NE, Harrison RV, James AL. (2014). Separating the contributions of olivocochlear and middle ear muscle reflexes in modulation of distortion product otoacoustic emission levels. Audiol Neurootol. 2014;19(1):41-8.

Kus LH, Negandhi J, Sklar MH, Eskander A, Estrada M, Harrison RV, Campisi P, Forte V, PropsT EJ. Corrosion casting of the subglottis following endotracheal tube intubation injury: a pilot study in Yorkshire piglets. Journal of Otolaryngology - Head & Neck Surgery 2013, 42:52  doi:10.1186/1916-0216-42-52

Carraro M, Negandhi J, Kuthubutheen J, Propst EJ, Kus L, Lin VY, Harrison RV. Attenuating cardiac pulsations within the cochlea: structure and function of tortuous vessels feeding stria vascularis. ISRN Otolaryngol. 2013 May 19;2013:941757. doi: 10.1155/2013/941757.

Kus LH, Negandhi J, Sklar MC, EskandeR A, Estrada M, Harrison RV, Campisi P, Forte V, Propst EJ. (2014). Angiogenesis in costal cartilage graft laryngotracheoplasty: A corrosion casting study in piglets. Laryngoscope. 2014 Jan 15. [Epub ahead of print]

Clinkard D, Amoodi H, Kandasamy T, Grewal AS, Chen S, Qian W, Chen JM, Harrison RV, Lin VY. Changes in the cochlear vasculature and vascular endothelial growth factor and its receptors in the aging C57 mouse cochlea.  ISRN Otolaryngol. 2013 Jun 27;2013:430625. doi: 10.1155/2013/430625.

Harrison AL, Negandhi J, Allemang C, D’Alessandro L, Harrison RV.  (2013) Acoustic cross-over between ears in mouse (mus musculus): determination using a novel ABR based bio-assay. Canadian Acoustics 41: 5-10.

Propst EJ, Ngan BY, Mount RJ, Martin-Munoz D, Blaser S, Harrison RV, Cushing SL, Papsin BC. (2013) Ossicular fusion and cholesteatoma in auriculo-condylar syndrome: In vivo evidence of arrest of embryogenesis. Laryngoscope. 2013 123: 528-32.

Harrison RV, Konomi U, Kanotra S, James A. (2013) Postnatal maturation of contralateral DPOAE suppression in a precocious animal model (chinchilla) of the human neonate. Acta Otolaryngol. 2013 133:383-9.

Harrison RV.  (2012) The prevention of noise induced hearing loss in children. Int Journal Pediatrics, 2012 Article ID 473541, pp13 doi: 10.1155/2012/473541

Kandasamy T, Clinkard D, Qian W, Chen S, Chen J, Harrison RV, Lin V. (2012) Changes in expression of VEGF and its receptors in the aging mouse cochlea – Part 1: The normal hearing mouse. J.Otolaryngol Head Neck Surg 41 Suppl 1: S36-42

Harrison RV, Negandhi J. (2012) Resting neural activity patterns in auditory brainstem and midbrain in conductive hearing loss. Acta Otolaryngol. 132: 409-414.

For additional publications please visit Pub Med »»