Characterizing the Electroencephalographic Brain Dynamics of Tactile Texture Processing
Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Publicerad
2010
Författare
Ziegler, Erik
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
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.
Beskrivning
Ämne/nyckelord
Biologisk fysik , Neurofysiologi , Biological physics , Neurophysiology