event-related synchronization/desynchronization …kazuo kato (tohoku gakuin university) osamu miura...

Event-related Synchronization/Desynchronization Affected by Spatial Frequencies of Background Visual Pattern during a Cognitive Task

Kazuo Kato (Tohoku Gakuin University)

Osamu Miura (Graduate school of Tohoku Gakuin University)

加藤和夫／東北学院大学

三浦孟／東北学院大学大学院

背景画像の空間周波数特性が認知課題遂行中の

事象関連同期/脱同期に与える影響

Introduction

2

Introduction

Color, Shape,

Movement, Depth

Spatial Frequency,

etc…

Phyco-physiological activity ?

例：安心、快適感 etc…

Spatial Frequency

例：建築デザイン etc…

Visual information

3

Background

4

Spatial Frequency

輝度の空間的変化のパターンを表す指標

Background

Vuilleumier P, Armony JL, Driver J, Dolan RJ: ”Distinct spatial frequency sensitivities for

processing faces and emotional expressions,” Nature Neuroscience. 6(6): 624-631, 2003 5

Background

Real environmental scene

空間周波数スペクトルを

1/f の直線で近似し，その傾きで定義

風景などの実空間画像に対する注視情報と空間周波数特性の傾きには，関連があることを示している Kato K, Shikoda A, Nishida M, Kuroki T, Ishikawa A and Kobayashi T: “Characteristics of image properties inducing eye

movement,” IEEJ Trans. EIS, Vol. 131, pp. 175-181 (2011) (in Japanese)

Neural activity were not addressed in this study 6

Our previous study

the slope () of its power spectral density

Background

(1) the low spatial frequency components may

preferentially participate in the neural activity

associated with the retrieval of arithmetic data

and that the 1/f frequency characteristics may

be optimal for playing important roles in

internal spatial processing of numbers.

(2) the most advantage of this method utilizing

a parameter, compared to the alternative

method using high or low pass filtering for

images, is that which enables to obtain multiple

data by adopting arbitrary and consecutive

values.

Our previous study

We evaluated how the spatial frequency characteristics of a visual stimulus, as

indexed by the slope () of its power spectral density, affected the event-

related potentials (ERPs) observed during a simple cognitive addition task.

Fz

Cz

Pz182 ms

360 msKato K et. al.: “Event-related Potential Affected by Spatial Frequency of

Background Visual Pattern During a Cognitive Task,” IEEJ Trans 2013,

Vol.8, pp. 483-488

What is Event-Related Synchronization

/Desynchronization (ERS/ERD) ?

自発脳波リズム変動(ERS/ERD)について検討を行った

誘発脳波特定の事象に関連して発生する

自発脳波自発的に発生している脳電位

（θ波, α波, β波）

事象関連同期/脱同期(ERS/ERD)：

外的，あるいは内的な事象に関連して生じる脳波リズムの変動

ERS/ERS

Visually

Information

Auditory

Information

8

Objective

人間特性を考慮した空間設計への適用

空間周波数特性が認知課題における自発脳波リズムに与える影響についての検討

The purpose of this study is to characterize the oscillatory changes in neural activity

associated with cognitive processes that are affected by the spatial frequency of a

visual stimulus during simple calculation tasks by using electroencephalography.

Objective

タスクとして

単純な認知課題の一つである計算課題を行う

Goal

空間周波数特性に着目

空間周波数が認知活動に関わる大脳神経活動に与える影響を評価

9

Visual stimuli

White noise ( = 0) 1/f ( = 1)

1/f2 ( = 2) 1/f3 ( = 3)

10

Visual stimuli

White Noise

1/f

1/f2

1/f3

White Noise

1/f

1/f2

1/f3

White Noise

1/f

1/f2

1/f3

White Noise

1/f

1/f2

1/f3

Spatial luminance fluctuations in an image

11

Visual stimuli

White Noise

1/f

1/f2

1/f3

White Noise

1/f

1/f2

1/f3

White Noise

1/f

1/f2

1/f3

White Noise

1/f

1/f2

1/f3

White noise 1/f

1/f2 1/f3

Slope : 0

Slope : 2

Slope : 1

Slope : 3

Slope of the regression curve fitted to the power spectral density

of spatial luminance fluctuations in an image

12

Visual stimuli

noise white

1/f

21/f

Low frequency High frequency

White noise 1/f 1/f2 1/f3

高周波数の影響が大きい低周波数の影響が大きい

13

Po

we

r sp

ect

rum

de

nsi

ty

Frequency [Hz]

31/f

Visual stimuli - Randomly selected number between 0–9 embedded in each stimulus

- 4種類の模擬画像に0～9の数字を挿入した輝度3cd/m2の縦902×横1282

ピクセルの画像

1/f2 1/f3

White noise (1/f0) 1/f

30.5° 1°

1.5°

20°

3 3

3 3

14

Task

(1) Addition task (計算有タスク)

(2) Reference task (参照タスク)

・・・

adding adding

・・・

1 trial ×25 times

2000ms 250ms

- Each 250-ms stimulus was presented 25 times per set and the numbers

were repeated twice for a total of 50 stimulus presentations

7 3

7 3

×2 sets

・・・

7 3

No adding No adding 15

×4 stimulus

Methods

EEG measurement

・ Subjects: 8 males (age, 21-23)

- All participants provided written informed consent

・ 19 electrodes based on the 10-20 system

- Reference electrodes: Linked electrode at both ears

- Impedance < 10kΩ

16

Methods Data analysis

・ Continuous Wavelet Transform

- with the mother function of morlet were conducted for each EEG epoch from 1 to 80 Hz per 0.1 Hz

・ Intertrial Variances - of the wavelet coefficients for each frequency per 0.1 Hz were calculated using

the equation below

where N = 50 at maximum, indicating the total number of trials, xf(i,j) denotes the j-th sample (wavelet coefficients) of the i-th trial, and represents the mean of data at the j-th sample.

・Band Average Variances - in the theta(4–6 Hz), alpha (8–13 Hz), low beta (13–20 Hz), and gamma (40–80

Hz) frequency ranges were also calculated and the 500-ms prestimulus period served as the value for baseline normalization. 17

Flow of analysis

認知活動の比較

• 計算有・無タスク間の分散の比較(time-frequency analysis)

• 特徴帯域毎の分散の時間変化の検討(time course)

• 特徴帯域毎の分散の空間分布の検討(spatial distribution)

空間周波数特性の比較

• 各空間周波数特性刺激に対する分散の変動の比較

Step1: Comparison between addition and reference task

Step2: Comparison among stimuli

18

Flow of analysis









19

Overall mean intertrial variances

20

O2

Pz

(a) Addition task (b) Reference task (c) Addition - Reference

Flow of analysis









21

Time Course of band-averaged variances

22

Theta (4-6 Hz) at O2 Alpha (8-13Hz) at O2

Low Beta (13-20 Hz) at Pz Gamma (40-80 Hz) at Pz

198ms

376ms

1,012ms 490ms 1,742ms

Addition Task Reference Task

Flow of analysis









23

Differential Topographical Map (Addition - Reference Task)

24

20 [%]

-20 1/f 1/f2

(a) Theta band

0 [%]

-20 1/f2 1/f3

(b) Alpha band

: p < 0.05

Differential Topographical Map (Addition - Reference Task)

25

25 [%]

-25 1/f 1/f3

20 [%]

-20 1/f2

(c) Low Beta band

(d) Gamma band

Fz

Cz

Pz

O1 O2

P4 T6 P3 T5

C3 T3 C4 T4

F3 F7 F8 F4

Fp1 Fp2

: p < 0.05

Flow of analysis









26

Results and Discussion

27

No

rmal

ized

var

ian

ce

S.E

. [%

]

No

rmal

ized

var

ian

ce

S.E

. [%

]

White noise 1/f 1/f2 1/f3 White noise 1/f 1/f2 1/f3

Visual stimuli Visual stimuli

120

110

100

90

80

120

110

100

90

80

(a) Theta at F4 (b) Theta at C4

*

*

*

* p < 0.05 * p < 0.05 *

*

*

Theta band (198ms, fronto-central area) - ERS for the 1/f and ERD for the 1/f2 stimulus - A linear change in variance in response to a

frequency change - This phenomenon may suggest the existence of a

neural frequency discrimination function accompanying simple cognitive calculations

Results and Discussion

28

White noise 1/f 1/f2 1/f3 White noise 1/f 1/f2 1/f3

Visual stimuli Visual stimuli

No

rmal

ized

var

ian

ce

S.E

. [%

]

No

rmal

ized

var

ian

ce

S.E

. [%

]

120

110

100

90

80

120

110

100

90

80

(c) Alpha at T5 (d) Alpha at P3

* p < 0.05 * p < 0.05

*

* *

*

Alpha band (376ms, left-temporal area) - In the reference task, the alpha-ERD associated with high spatial frequencies

may suggest the importance of the left hemisphere area over areas associated with early visual processing .

- In the addition task, all frequencies activate neural processes suggest to relate to the retrieval of arithmetic data calculations and the interpretation of operation symbols.

Conclusion

29

- A frequency discrimination function has been suggested to exist at a latency

of 198 ms in the theta band activity recorded in the addition task from the

fronto-central area.

- The alpha ERD in the reference task at the left temporal-parietal area at the

latency of 376 ms also showed a spatial frequency dependency concerned

with perceptual filter.

- The frequency dependence of low Beta and Gamma bands could not be

confirmed from our data set.

Therefore, we suggest that oscillatory changes in the neural activity associated

with cognitive processes affected by spatial frequency occur along with ERP

responses.

event-related synchronization/desynchronization …kazuo kato (tohoku gakuin university) osamu miura...

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