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Tremblay Lab

Exploring retinal physiology

The vertebrate retina possesses a well-characterized laminar cellular architecture that 
is ideally suited for field potential studies. The synaptic circuitry underlying its functional integration is comprehensive so the retina is considered an excellent model for studying the neuronal mechanisms underlying elementary information processing of the central nervous system.

Small alterations in cellular activity can yield significant impact on network dynamics and the processed output. Team members in the Tremblay Lab are interested in deciphering how alterations in activity in a limited cell population mimicking known retinal pathologies can modify the integration of the composite field potentials emanating from the whole network (the electroretinographic signal).

We are also dedicating 
our efforts to understand how these circuit alterations modify the binary efferent message the ganglion cells (RGCs) are sending to the more central brain processing.

Electroretinography and multielectrode array technologies

The basic science lab is centered around two technologies to explore the various facets of the retinal physiology:

The first technique, called electroretinography (ERG), is a recording of the retina, collected non-invasively, by placing an electrode on the cornea. Using a series of diffuse flashes of increasing intensity, it is possible to determine the health of photoreceptors, bipolar cells and ganglion cells following various treatments such as exposures to anesthetics, or neuroprotective or neutraceutic agents.

The second technique, called multielectrode array (MEA), allows the simultaneous recording of multiple cells in an ex vivo retinal preparation. This technique is used to:

  • study how cells are communicating between each other to form synaptic circuits
  • understand the relationship between field potentials and action potentials
  • comprehend the efficiency and coherence in the efferent retinal message

Analysis techniques

Analysis techniques such as cross-correlation, transfer entropy, coherence estimation, or dimension reduction and 
population activity time course are available to quantify the efficiency of the neural code in normal and artificially altered conditions.



Visual Electrophysiology Unit at the IWK

In parallel to the basic science approaches, Dr. Tremblay is also responsible for the Visual Electrophysiology Unit at the IWK Health Centre, a diagnostic lab that serves the whole Atlantic Canada population.

Clinical investigations using various forms of evoked potentials and psychophysical approaches allow characterization of human retinal disorders, raising fundamental pathological mechanistic issues that can be deciphered by returning those questions to the basic science bench.

Current research projects

  • Automation by wavelet analysis and cross correlation of a new sweep-VEP technique to assess visual acuity
  • Investigation of how anesthetics influence the organization of the retinal efferent message
  • Cytotoxic effects of clinically relevant drugs (currently the antiepileptic Vigabatrin)
  • Developmental influence of voltage-gated sodium channels isoforms on the organization of the efferent retinal message

Selected basic science publications

Selected clinical publications

  • Kalt W, McDonald JE, Fillmore SAE, Tremblay F (2014) Blueberry effects on dark vision and recovery after photo-bleaching: placebo-controlled cross-over studies. J. Agricultural & Food Chemistry 62(46):11180-11189
  • Parkinson J, Sandusky H, Tremblay F. (2013) Interocular effect during visual acuity measurement with and without amblyopia. Strabismus 21(2): 67-73
  • Parkinson J & Tremblay F. (2009) Misleading Clinical Stereoacuity Levels in Pediatric Maculopathy. J AAPOS 13(5):496-8
  • Tremblay, F & Parkinson J. (2008) Gradient of Deficit in Cone Responses in the Incomplete Form of Congenital Stationary Night Blindness revealed by Multifocal Electroretinography. Doc Ophthalmol, 116:41-47
  • Tremblay F & Parkinson J. (2003) Alteration of electroretinographic recordings performed under sedation or halogenated anesthesia in pediatric population. Doc Ophthalmol. 107:271-279

Past trainees and their projects

2014

Liptay, Henry, USRA Summer student

“Retinal sensitivity during response oscillations”
2014

Clarke, Benjamin, Honours Student

“Local field potentials in MEA”

First prize, Ophthalmology Research Day, April 2014 Heinish IWK Summer Studentship Award.
2013

Akhtar, Isha, MSc elective

“Contribution of retinal ganglion cells in electroretinogram”
2013

Elliott, Courtney, USRA Summer Student

“Light-Induced Retinopathy in a diurnal model: Guinea Pig”
2013

Clarke, Benjamin, USRA Summer Student

“Nav1.6 and entropy in RGCs”
2012

Locke, Jeffrey, M.Sc. Vision Science

“Effect of Ketamine/xylazine on RGC activity”
2012

Armstrong, Vickie, PDF Psychology

“Visual Function in adults and children with Autism Spectrum  Disorders”
2011,12

Dickinson, Sally, USRA Summer Student

“Development of Intrinsic Spiking Behavior in RGCs”
2011

Parkinson, Joan, M.Sc. Vision Sicences

“Algorithm Development for Sweep-VEPs”
2010

Smith, Ben, Ph.D., Biological Sci (Co-Superv.)

“Role of Sodium Voltage-Gated Channel Isoforms (NaV) in the Generation of Composite Retinal Local field Potentials and Their Influence on Retinal Ganglion Cells Entropy; an In Vivo Comparative assay with Ex-Vivo Multi-Electrode Array studies”
2010

King, Jill, Summer Student

“Effects of somatostatins on RGC activity in MEA prep.”
2010

Smith, Kari, M.Sc. Vision Science

“Characterization of inhibitory binocular interactions and clinical implications”
2009

Wong, Aimee, Ph.D. Psychology

Minor project: “Cortical plasticity in aging DBA mice”
2009

Sohail Safi, M.D. Ophthalmology

“Retinal effects of drugs used in the treatment of acanthamoeba ketatitis”
2008

Skeet, Andrea, M.Sc. Vision Science

“An Investigation of Central vs Peripheral Visual Evoked Potentials in Amblyopia”
2008

Wood, Leah, M.Sc. Vision Science

“Regulation of Retinal Activity in an Ex-Vivo Guinea Pig Model by Experimental Conditions and Effects of Isoflurane and Propofol Anesthesia”
2007,08

Jenna Waterhouse; Summer Student

“Neuroprotective effects of blueberry diet in rat LIR”
2007

Dr. Roman Windisch, Research fellow Ophthalmol

“Modelisation of photopic ERG signal”
2006

Jaime McDonald; Summer student

 “Neuroprotective effects of blueberry diet in rat LIR”
2005

Lillian Aladejebi, M.Sc. Vision Science

“Detection of cortical suppression during LET with MFVEP”
2004

Denis Falvey, Ph.D. Interdiciplinary Program

“Wavelet and principal component analysis of ERG in ischemia”
2004

Babak Meleki, MSc Physiology

“Generators of electrodiagnostic signal in a swine model”
2004

Heather Gunn, M.Sc. Vision Science

“Interocular Effect in Amblyopia: The Effect of Occlusion Methods on visual Function Test Results”
2000

Hygiea de la Cruz, B.Sc.-Med student

“Multifocal ERGs in glaucomatous retinopathy:”
2000

Raja Addel-Majid, PDF, Anat/Neuroscience

“Localization of adenylyl cyclase proteins in the rodent retina”
1999

Mélanie Lalonde, M.Sc

“Non invasive assessment of ganglion cell activity:  Axotomy, TTX and isoflurane porcine models”
1996

Neeraj Lapanka, Summer student;

“Rat model of retinal ischemia”
1995

Cindy Chung; Summer student;

“Crossed VEPs pattern in CSNB2”
1992

Dr. Samir Jamal; Research Fellow Ophthalmology;

“Characterization of visual development in CSNB”
1991

Dr. Simon Lam; Research Fellow Ophthalmology;

“Oscillatory Potential generators”.