Saturday, June 17, 2006

Human Brain Mapping Convention 2006, Florence Italy.

I have just returned from the 2006 OHBM convention in Florence, Italy. It was my first OHBM convention, and also my first time in Italy. I really enjoyed this convention and presenting my results there (see:, or you can view my abstract in an earlier entry of this weblog).

Saturday, June 10, 2006

What is the Tongue Display Unit (TDU)?

The TDU is a device that can help transmit visual information via the tongue using electro-tactile signals. The dream of beiong able to restore certain functions of vision via tactile senses is actually a very old one, but one we are only beginning to approach today thanks, in part, to a better understanding of how the brain functions, and also to recent technological adavancements like the miniaturisation of computers and capture devices like web-cams.
The first visual-tactile interface system was developed by Dr. Paul Bach-y-Rita in the 1970's. The original tactile visual sensory substitution device (TVSS) was very large (due in part to the large volume of computers and cameras then) and it stimulated the tactile surface of the back to transmit visual information.
This system was later adapted by scientist (Kurt Kaczmarek, and Paul Bach-y-Rita) at the University of Wisconsin to use the tactile sense of the tongue to transmit the visual information to the brain. For more information please see:

This system was given to the Maurice Ptito laboratory in vision research in 2005 to help develop the system and our understanding of brain plasticity and sensory Substitution. Basically the system that we have is a webacm that is connected to a laptop. The laptop communicates with the tongue device through a wireless bluetooth connection that sends the image that is being capted by the camera in real time to the tongue stimulator aray. This aray consists of a grid of electrodes that can recreate the image with electricity on the tongue. I had the honour of meeting Dr. Paul Bach-y-Rita on the inauguration of the Harland Sanders Chair in visual science. We had very interesting conversations on the nature of sensory substitution and the philosophical implications of brain plasticity. My goal as a reasearcher is to find out if it is possible to use this device for navigation and also what cortical regions will be elicited in this task.

Volumetric analysis of the hippocampus in early blind subjects

D-R. Chebat1, J-K. Chen2, A. Ptito2, R. Kupers3, F. Schneider1,4 and M. Ptito1,4.

1Chaire de recherche Harland Sanders, Ecole d’Optométrie, Université de Montréal, Qc, Canada; 2Neuropsychology, Montreal Neurological Institute, McGill University, Qc, Canada; 3Pet center, Riggs Hospital, Copenhagen, Denmark; 4Danish Research Centre for MR, Copenhagen University Hospital, Hvidovre, Copenhagen, Denmark.
There is a relation between the hippocampus and coding of allocentric space(Crane & Milner, 2005). Since navigation is a highly visual task, what structural changes could be associated with non-visual navigation? This study compares hippocampal volumes of 10 early blind, and 10 sighted controls. Structural MRIs were obtained with a 1.5 T Siemens and hippocampi were manually segmented in three parts: anterior, body and posterior. Mapping was done by two independent experimenters blind to the conditions. MR scans and hippocampal mappings were also normalized into stereotaxic space (MNI). Hippocampal delimitations were binarized and the reccurence of each voxel as belonging or not to the hippocampus was compared between groups (Chi2). No differences in total hippocampal volumes were found and there was no within group differences for left versus right hippocampal volumes. Early blind subjects had significantly smaller posterior hippocampi compared to controls (ANOVA, p<0.05).

Supported by the Harland Sanders Chair in Visual Sciences and the Danish Medical research Council.

Welcome to my blog!

Dear internet-navigators,
It is a great pleasure for me to welcome you to my blog. I began this blog because i was being asked many questions about my Ph.D. research concerning navigation in the blind, brain plasticity and sensory substitution. The object of my Ph.D. research using the tongue display unit (TDU), a device capable of transmitting visual information via the tongue, is to test the limits of this device in navigation, and also to identify what brain regions will be recruited in such a task.
This blog will keep you informed on the ground breaking research being conducted at Unversity of Montreal, school of Optometry in the laboratory of world reknown neurologist Dr. Maurice Ptito, my Ph.D supervisor. I will also keep you posted on all new developments of my research and preliminary results.
On this blog you will find updates of my research, abstracts, and past publications. I will also post messages and short communications (in french and in english) on the theoretical aspects of my research. You will find several links to other interesting research being conducted on brain plasticity, sensory substitution and navigation in the blind in general.
The show "découverte" on radio-canada made a segment reviewing the wqork that has been conducted in Dr. Maurice Ptito's laboratory concerning sensory substitution and brain plasticity:, i suggest you check it out.
Daniel-Robert Chebat
p.s. Please feel free to send me any comment sor questions you may have and i will gladly answer you in a reasonable amount of time. Hope to talk to you soon!

D-R. Chebat, D. Boire, M. Ptito (2006) Development of the commissure of the superior colliculus in the hamster. J Comp Neurol. Feb 20;494(6):887-902

D-R. Chebat, J-K. Chen, A. Ptito, R. Kupers, F. Schneider, M. Ptito (2006) Volumetric analysis of the hippocampus in early blind subjects Human Brain Mapping, Florence Italy

Wednesday, June 07, 2006

La négociation d’obstacle par des aveugles de naissance à l’aide de stimulation linguale électro-tactile

D-R. Chebat, C. Rainville, M. Ptito.

Nous étudions les capacités de personnes aveugles nés , de cécité tardive, et voyante dans la perception et la négociation d'obstacles dans des tâches de navigation et d’orientation dans l’espace a l’aide de l’appareil de stimulation linguale (Tongue Display Unit- TDU). Une étude de cas démontre décris les perceptions d’un sujet utilisant le TVSS pour identifier et localiser certains objets (Guarniero, 1974). Ces études et les avancées technologique permettent de croire qu’il serait possible pour un sujet aveugle de naissance d’apprendre à décoder l’information capté par ces appareils pour se déplacer et éviter des obstacles dans un environnement qui lui est inconnu. Aucune étude n’a étudié les capacités des aveugles de s’orienter dans un parcours à obstacle utilisant un appareil de substitution sensorielle, tel le Tongue Display Unit (TDU).