時(shí)空域的腦電模式研究.pdf

1、Experimental evidence proposes that complex cognitive funcTiO2s and behavioral acts are arranged at global levels in the brain and they come up from synchronized operaTiO2 of localize brain areas.In that sense the estima

2、TiO2 of the spatial-temporal organizaTiO2 of the brain activity is a promising approach for studying the integrative activity of the brain.This dissertaTiO2 focused on the method,developed by Professor Walter Freeman gro

3、up,to study spatial-temporal patterns of brain activity in signals recorded at the cortical surface(ECoG).The main goal was to adapt the methodology,developed for ECoG signal,for it use on signal recorded at the scalp(EE

4、G).It is important because EEG recording is a non-invasive procedure than can be applied repeatedly to patients, normal adults and children with virtually no risk or limitaTiO2 and makes it possible to take advantagebot

5、h of the cognitive and phenomenological awareness of a normal healthy subject. Initially an improved method to study the spatial-temporal patterns in ECoG signal was developed and compared with the classical cone fittin

6、g.The improved method significantly reduces the processing time while the coincidence level in time domain obtained by both methods is kept high.Consequently,it is a promising tool to study ECoG in real time.In addiTiO2

7、AM patterns can be clearly distinguishable using the improved method.Then the improved method was adapted for use on EEG signals and tested in two databases. Due to the well known differences in scale and resoluTiO2 betw

8、een ECoG and EEG, adjustments in the techniques to identify stable frames and estimated frame gradient were necessary. The first database analyzed was a database previously uses to study event related potentials.In this

9、 case the experiments were conducted trial by trial:each trial was l second length after the stimuli presentaTiO2.Stable frames were used as time markers to extract high dimensional feature from the analytic power within

10、 the time samples that stable frames showed up.The mean level of classificaTiO2 for EEG was comparable to that for ECoG.which shows for the first time that.owing to the scale-free properties of brain activity.these techn

11、iques adapted from ECoG can be employed to extract useful informaTiO2 noninvasively from scalp EEG. The second database was continues recording of brain activity during a perceptual-cognitive task.in which the stimulus

12、was a combinaTiO2 of two modalities,auditory and visual stimulaTiO2. The objective was to test the hypothesis that patterns of oscillaTiO2 related to perceptual categories occur in scalp EEG.Global amplitude patterns in

13、the range of 15-22 Hz from all subjects were classified with respect to stimulus combinaTiO2 type significantly above chance levels shortly after the stimulus onset.At the same time the classificaTiO2 rate in the pre-sti

14、mulus period or late post-stimulus period was not statistically different from chance. The results showed that this adapted technique can provide the foundaTiO2 needed to investigate the cerebral dynamics of learning or