You can only perceive the location of a touch when you know where your hands are in space. Locating a touch to the body requires the integration of internal (somatotopic) and external (spatial) reference frames. In order to explore the relative contribution of internal versus external information, this thesis employed a crossed-hands tactile temporal order judgment (TOJ) task. This task requires participants to indicate which of two vibrations, one to each hand, occurred first. The magnitude of the deficit observed when the hands are crossed over the midline provides an index into how internal and external reference frames are integrated. This thesis first showed that the crossed-hands tactile TOJ task is a reliable measure, supporting its use as a measure of reference frame integration. Next, this thesis applied a probabilistic model to theoretically estimate the weights placed on the internal and external reference frames. We showed that a bias towards external information results in a larger external weight and vice versa for internal information. Finally, using the model we showed that the crossed-hands deficit is reduced while lying down, supporting an influence of vestibular information on the external reference frame. Taken together, this thesis highlights that we are able to flexibly adapt the weighting of different spatial representations of touch. / Thesis / Doctor of Science (PhD) / Determining the boundary of our body requires we localize the touches to our body. When the body moves and interacts with the world this determination becomes more difficult. Integrating information from other senses can support the localization of touch, and thus knowledge of our body. For example, to locate a touch to your right hand, you must feel the touch on your right hand, but also determine where your right hand is located in space. This thesis shows that the contributions of each sense to locate a touch is consistent within an individual and remains consistent over time. Interestingly, based on the availability of each sense, we flexibly adapt their contributions to ensure that our ability to locate the touch remains unchanged. What we define as our body is constructed based on the information available in the present moment.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/26330 |
| Date | January 2021 |
| Creators | Unwalla, Kaian |
| Contributors | Shore, David, Psychology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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