Characterizing the Electroencephalographic Brain Dynamics of Tactile Texture Processing
Examensarbete för masterexamen
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|Type: ||Examensarbete för masterexamen|
|Title: ||Characterizing the Electroencephalographic Brain Dynamics of Tactile Texture Processing|
|Authors: ||Ziegler, Erik|
|Abstract: ||Characterizing the Electroencephalographic Brain Dynamics of Tactile Texture Processing Erik Ziegler Touch produces the most intimate representation of our environment. Through the skin we are perpetually monitoring the outside world and our ﬁngertips in particular provide a highly sensitive interface for exploring the textural aspects of objects in our surroundings. The NanoBioTact project studies these aspects of touch in the pursuit of an improved haptic under- standing and the development of a functional artiﬁcial ﬁngertip. As part of this project, this thesis aims to characterize the complex brain dynamics involved in tactile texture processing. Speciﬁcally, this thesis examines the central processing of both texture and movement through passive tactile exploration by the ﬁngerpad. To this aim, electroencephalography (EEG) was employed to quantify brain activity and a specially-designed robotic stimulation platform was used to produce well-controlled replicable stimuli. Rectangular gratings with spa- tial periods of 1560 and 520 µm were slid across the distal ﬁngerpad with a constant velocity of either 10 or 30 mm/s. The 64-channel EEG response was evaluated using metrics such as the event-related spectral perturbation (ERSP) and intertrial phase coherence (ITC) in order to explore the mod- ulation of texture processing by spatial period and velocity. Additionally, the neural activity was decomposed via independent component analysis (ICA) so that temporally-distinct sources could be considered separately, and group-level analysis was performed by clustering analogous components across subjects. ICA facilitated the identiﬁcation of components from both the contralat- eral primary (S1) and secondary (S2) somatosensory cortices. Partial phase resetting was identiﬁed in contralateral S1 from the high-theta to low-alpha band (5-12 Hz) in response to both the onset and oﬀset of surface move- ment. This stimulus-induced phase-resetting, in combination with theta- band phase-locking from the dorsal cingulate cortex, produces a character- istic P50-N140-P300 event-related potential. It was shown that the two earliest peaks increase in amplitude for both rougher surfaces and faster movement speeds, both P50 and N140 also appear later for slower move- ment, and P50 latency increases with spatial period. This thesis has successfully described the characteristic response dynam- ics produced by texture processing, and additionally, it has identiﬁed as- pects of coordinated oscillatory activity, such as the theta-band correlation between contralateral S1 and the dorsal cingulate, which deserve further investigation.|
|Keywords: ||Biologisk fysik;Neurofysiologi;Biological physics;Neurophysiology|
|Issue Date: ||2010|
|Publisher: ||Chalmers tekniska högskola / Institutionen för teknisk fysik|
Chalmers University of Technology / Department of Applied Physics
|Collection:||Examensarbeten för masterexamen // Master Theses|
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