Assoc Prof Ramesh Rajan - Researcher Profile

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Address

Department of Physiology
Faculty of Medicine, Nursing & Health Sciences, Clayton

Biography

Sensory information and the bionic eye

Associate Professor Ramesh Rajan has extensive experience in studying the cerebral cortex, which has been a great advantage to the Monash Vision Group. He says their project to develop an implant that goes directly into the cerebral cortex has promise for the majority of visually-impaired people. Ramesh is also researching how the brain processes sensory information under different circumstances.

The Monash Vision Group has been innovative in its project to build a device to provide some vision for the blind. This project includes a new type of electrode, designed by Ramesh and his colleagues, that the team is using on its current model. Ramesh says an implant that bypasses the eye and goes directly into the brain has significant advantages over a device that operates through the eyes. 

“An implant at the level of the eyes would stimulate the eyes to send messages to the brain, but in 80 per cent of cases, nerve damage prevents that from happening,” Ramesh says. 

“We’re developing an implant that goes straight into the brain. In many eye degeneration cases, the brain is still functional, so we need to provide a message to the brain. That consists of a range of steps, the first being to test the electrodes for issues such as safety and tissue compatibility.”

Ramesh’s other focus is how the brain processes sensory information to make sense of the world. The ability of children and people with autism spectrum disorders to process information against competing stimuli is the basis for much of this research.

“When you listen to speech, people are often talking in the background. When you look around a messy room, you’re able to identify the one thing you’re interested in. I’m interested in how we pick up what’s of interest and discard what’s not. People with different types of brain disorders, such as autism spectrum disorders or epilepsy, can’t do that for speech. This work has extended to people who are high-functioning autistics, and people with Asperger’s, with Peter Enticott at The Alfred.”

Ramesh is also trying to understand how traumatic brain injury impacts on our ability to process sensory information. 

“In some forms of traumatic brain injury, using CAT scans or MRIs doesn’t identify any visible damage and so it’s hard to find what’s going wrong. Yet these people have cognitive deficits, memory loss, movement disorders, etc. We’ve found a new set of effects in how they process sensory information, which impacts on producing the appropriate response. When we produce a response, we have to take in the information that’s coming, such as catching a ball that’s coming towards you. The parts of the brain that control movement and learning produce the wrong responses - not necessarily because there’s something wrong with them, but because they’re getting the wrong information as to what to do.”

Ramesh is in the early stages of developing a device to test touch sensitivity. He hopes doctors will eventually use his touch test in a similar way to standard eyesight and hearing tests. Ramesh thinks two groups could benefit enormously from such an assessment.

“If people have burns and you want to follow their recovery, you need to know how sensitive their skin is. Has it recovered functionality or is it still hyper-sensitive? You also need to be able to measure touch sensitivity in older people. As people get older, they have difficulty with some tasks. That may be because their fingers have lost their sensitivity.

“We’re trying to develop a tool to measure touch sensitivity, and we hope to make it available as a clinical tool. We want to create something that’s automated and can be manipulated to test any region that the user designates.”

Qualifications

PHYSIOLOGY
Institution: University of Western Australia
Year awarded: 1985

Publications

Books

Harrison, R.V., Kraus, N., Lutkenhoner, B., Rajan, R., Schreiner, C. (eds), 1998, Audiology and Neuro-Otology: Basic Research and Clinical Applications, S Karger Medical and Scientific Publishers, Basal Switzerland.

Book Chapters

Mendelson, J., Rajan, R., 2011, Cortical effects of aging and hearing loss, in The Auditory Cortex, eds Jeffery A. Winer & Christoph E. Schreiner, Springer Science+Business Media, USA, pp. 493-511.

Frisina, R., Rajan, R., 2005, Inferior Colliculus: Aging and Plasticity, in The Inferior Colliculus, eds JA Winer & CE Schreiner, Springer, USA, pp. 559-583.

Journal Articles

Rajan, R., Dubaj, V., Reser, D.H., Rosa, M.G., 2013, Auditory cortex of the marmoset monkey - complex responses to tones and vocalizations under opiate anaesthesia in core and belt areas, European Journal Of Neuroscience [P], vol 37, Wiley-Blackwell Publishing Ltd, UK, pp. 924-941.

Brunton, E.K., Lowery, A., Rajan, R., 2012, A comparison of microelectrodes for a visual cortical prosthesis using finite element analysis, Frontiers in Neuroengineering [E], vol 5, Frontiers Research Foundation, Switzerland, pp. 1-23.

Alwis, D.D.S., Yan, E.B., Morganti-Kossmann, M.C., Rajan, R., 2012, Sensory cortex underpinnings of traumatic brain injury deficits, PLoS ONE [P], vol 7, issue 12 (Art. No.: e52169), Public Library of Science, USA, pp. 1-19.

Canny, B., Mann, C., Lindley, J., Rajan, R., 2011, The influence of language family on academic performance: response to Azer, Medical Education [P], vol 45, issue 6, Wiley-Blackwell, USA, p. 648.

Rajan, R., Irvine, D., 2010, Severe and extensive neonatal hearing loss in cats results in auditory cortex plasticity that differentiates into two regions, European Journal Of Neuroscience [P], vol 31, issue 11, Wiley-Blackwell Publishing Ltd, UK, pp. 1999-2013.

Mann, C.M., Canny, B.J., Lindley, J.M., Rajan, R., 2010, The influence of language family on academic performance in Year 1 and 2 MBBS students, Medical Education [P], vol 44, issue 8, Wiley-Blackwell Publishing Ltd, UK, pp. 786-794.

Rajan, R., Cainer, K.E., 2008, Ageing without hearing loss or cognitive impairment causes a decrease in speech intelligibility only in informational maskers, Neuroscience, vol 154, issue 2, Pergamon, United Kingdom, pp. 784-795.

Burns, O.M., Rajan, R., 2008, Learning in a task of complex auditory streaming and identification, Neurobiology of Learning and Memory, vol 89, issue 4, Academic Press Inc Elsevier Science, San Diego, CA, USA, pp. 448-461.

Cainer, K.E., James, C.S., Rajan, R., 2008, Learning speech-in-noise discrimination in adult humans, Hearing Research, vol 238, Elsevier Science BV, The Netherlands, pp. 155-164.

Rajan, R., 2007, Bandwidth dependency of cochlear centrifugal pathways in modulating hearing desensitization caused by loud sound, Neuroscience, vol 147, issue 4, Pergamon-Elsevier Science Ltd, Oxford England UK, pp. 1103-1113.

Rajan, R., Browning, A.S., Bourke, J.L., 2007, Heterogeneity in the coding in rat barrel cortex of the velocity of protraction of the macrovibrissae, European Journal of Neuroscience, vol 25, issue 8, Blackwell Publishing, Oxford England UK, pp. 2383-2403.

Rajan, R., Bourke, J.L., Cassell, J., 2006, A novel stimulus system for applying tactile stimuli to the macrovibrissae in electrophysiological experiments, Journal of Neuroscience Methods, vol 157, issue 1, Elsevier BV, Amsterdam Netherlands, pp. 103-117.

Rajan, R., 2006, Bandwidth determines modulatory effects of centrifugal pathways on cochlear hearing desensitization caused by loud sound, European Journal of Neuroscience, vol 24, issue 12, Blackwell Publishing, Oxford UK, pp. 3589-3600.

Rajan, R., 2006, Contextual modulation of cochlear hearing desensitization depends on the type of loud sound trauma, Hearing Research, vol 213, issue 1-2, Elsevier, Amsterdam The Netherlands, pp. 58-63.

Rajan, R., 2005, Contextual modulation of olivocochlear pathway effects on loud sound-induced cochlear hearing desensitization, Journal of Neurophysiology, vol 93, issue 4, American Physiological Society, USA, pp. 1977-1988.

Rajan, R., 2003, Crossed and uncrossed olivocochlear pathways exacerbate temporary shifts in hearing sensitivity after narrow band sound trauma in normal ears of animals with unilateral hearing impairment, Audiology and Neuro-Otology, vol 8, issue 5, Karger, Basel Switzerland, pp. 250-262.

Irvine, D.R.F., Rajan, R., Smith, S., 2003, Effects of restricted cochlear lesions in adult cats on the frequency organization of the inferior colliculus, The Journal of Comparative Neurology, vol 467, issue 3, Wiley-Liss, USA, pp. 354-374.

Rajan, R., 2003, Plasticity in auditory cortex after receptor damage: excitatory and inhibitory processes, IETE Journal of Research, vol 49, issue 2 & 3, Institution of Electronics and Telecommunications Engineers, New Delhi India, pp. 157-170.

Rajan, R., 2001, Cochlear outer-hair-cell efferents and complex-sound-induced hearing loss: protective and opposing effects, Journal of Neurophysiology, vol 86, issue 6, American Physiological Society, Bethesda USA, pp. 3073-3076.

Dietrich, V., Nieschalk, M., Stoll, W., Rajan, R., Pantev, C., 2001, Cortical reorganization in patients with high frequency cochlear hearing loss, Hearing Research, vol 158, issue 1-2, Elsevier Science BV, Amsterdam Netherlands, pp. 1-7.

Irvine, D.R.F., Rajan, R., Brown, M., 2001, Injury-and use-related plasticity in adult auditory cortex, Audiology & Neuro-Otology, vol 6, issue 4, Karger, Basel Switzerland, pp. 192-195.

Rajan, R., 2001, Noise priming and the effects of different cochlear centrifugal pathways on loud-sound-induced hearing loss, Journal of Neurophysiology, vol 86, issue 3, The American Physiological Society, Bethesda Maryland USA, pp. 1277-1288.

Rajan, R., 2001, Plasticity of excitation and inhibition in the receptive field of primary auditory cortical neurons after limited receptor organ damage, Cerebral Cortex, vol 11, issue 2, Oxford University Press Inc, Cary North Carolina USA, pp. 171-182.

Rajan, R., 2001, Unilateral hearing losses after loud sound-induced temporary threshold shifts and efferent effects in the normal-hearing ear, Journal of Neurophysiology, vol 85, issue 3, American Physiological Society, Bethesda MD USA, pp. 1257-1269.

Rajan, R., 2000, Centrifugal pathways protect hearing sensitivity at the cochlea in noisy environments that exacerbate the damage induced by loud sound, Journal of Neuroscience, vol 20 issue 17, Society for Neuroscience (USA), Washington DC USA, pp. 6684-6693.

Irvine, D.R.F., Rajan, R., McDermott, H.J., 2000, Injury-induced reorganization in adult auditory cortex and its perceptual consequences, Hearing Research, vol 147, Elsevier Science BV, Amsterdam Netherlands, pp. 188-199.

Rajan, R., Irvine, D.R.F., 1998, Absence of plasticity of the frequency map in dorsal cochlear nucleus of adult cats after unilateral partial cochlear lesions, The Journal of Comparative Neurology, vol 399 (1), Wiley-Liss Inc (Division of John Wiley & Sons Inc), New York NY USA (www.interscience.wiley.com), pp. 35-46.

Rajan, R., Irvine, D.R.F., 1998, Absence of plasticity of the frequency map in dorsal cochlear nucleus of adult cats after unilateral partial cochlear lesions, The Journal of Comparative Neurology, vol 399, Wiley-Liss Inc, New York NY USA, pp. 35-46.

Rajan, R., Irvine, D.R.F., 1998, Neuronal responses across cortical field A1 in plasticity induced by peripheral auditory organ damage, Audiology and Neuro-Otology, vol 3 (2-3), S Karger Medical and Scientific Publishers, Basal Switzerland (www.karger.com), pp. 123-144.

Rajan, R., Irvine, D.R.F., 1998, Neuronal responses across cortical field A1 in plasticity induced by peripheral auditory organ damage, Audiology & Neuro-Otology, vol 3, S Karger AG, Basel SWITZERLAND, pp. 123-144.

Rajan, R., 1998, Receptor organ damage causes loss of cortical surround inhibition without topographic map plasticity, Nature Neuroscience, vol 1 (2), Nature America Inc, New York NY USA (http://neurosci/nature.com), pp. 138-143.

Rajan, R., 1997, Auditory response areas altered by intermodulation distortion products from background tones, Neuroreport, vol 8, Rapid Science Publishers, London UK, pp. 3177-3182.

Irvine, D.R., Rajan, R., 1997, Injury-induced reorganisation of frequency maps in adult auditory cortex: The role of unmasking of normally inhibited inputs, Acta Oto-Laryngologica, vol supplement 532, Scandinavian University Press, Stockholm Sweden, pp. 39-45.

Conference Proceedings

Worland, K., Rajan, R., 1998, Effect of noise masking on neural coding of interaural intensity differences, Proceedings of the Australian Neurosciences Society, Canberra ACT 27-30 January 1998, Australian Neuroscience Society, Melbourne Vic Australia, p. 168.

Nitsos, I., Rajan, R., Walker, D.M., 1997, Characterisation of spinal projecting neurons in the pons which express Fos immunoreactivity during hypoxia in fetal sheep, Proceedings Society for Neuroscience, New Orleans USA,25-30 October, Society for Neuroscience, USA, p. 436.

Irvine, D.R., Rajan, R., 1997, Subcortical contributions to cortical reorganization consequent on restricted cochlear lesions in adult animals, Proceedings of the Australian Neuroscience Society, Newcastle, NSW, 02-05/02/1997, Australian Neuroscience Society, Australia, p. 83.

Postgraduate Research Supervisions

Current Supervision

Program of Study:
(DOCTORATE BY RESEARCH).
Thesis Title:
Examination of new pharmacological therapies in a rat model of diffuseTraumatic Brain injury.
Supervisors:
Rajan, R (Main), Lowery, A (Associate).
Program of Study:
(DOCTORATE BY RESEARCH).
Thesis Title:
Neuroscience.
Supervisors:
Rajan, R (Main).
Program of Study:
(DOCTORATE BY RESEARCH).
Thesis Title:
Optimising electrode geomentry for a cortical visual prosthesis.
Supervisors:
Lowery, A (Joint-co), Rajan, R (Joint).
Program of Study:
(DOCTORATE BY RESEARCH).
Thesis Title:
Pelviureteric peristalsis in health and disease.
Supervisors:
Lang, R (Main), Rajan, R (Associate).
Program of Study:
(MASTER'S BY RESEARCH).
Thesis Title:
Theoretical analysis on the mechanics of a rat brain injury testing model.
Supervisors:
Yan, W (Main), Rajan, R (Associate).
Program of Study:
(DOCTORATE BY RESEARCH).
Thesis Title:
Traumatic brain injury & the barrel cortex; Using a novel sensory system to understand functional changes in the brain..
Supervisors:
Rajan, R (Main), Coleman, H (Associate), Morganti-Kossmann, M (Associate), Yan, E (Associate).

Completed Supervision

Student:
Burns, O.
Program of Study:
Learning to discriminate speech in background noise. (PHD) 2007.
Supervisors:
Rajan, R (Main), Rosa, M (Associate).
Student:
Griffiths, D.
Program of Study:
Neuroscience. 2009.
Supervisors:
Rajan, R (Main).