언어와 인지

핚국외국어대학교, 언어인지과학과

언어와 인지

2011년 1학기

강의 7, 4/11/2011 뇌와 언어II

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들여다 보려면…

Electrical Recordings

• EEG (Electroencephalogram, 뇌파)

– Recording of electrical activity in the brain, which appears as waves of various widths and heights

• ERP (Event Related Potentials, 사건관련전위) – EEG waves associated with a particular event

or task averaged over a large number of trials

• 이점

– 시간해상도

– 비용

Hans Berger (1873-1941)

His patients His work

http://www.psychiatrie.uniklinikum-jena.de/Geschichte.html

Electroencephalography (EEG)

• 머리에 부착한 전극을 통 해서 뇌에 있는 신경세포 의 전기적 활동을 기록.

• 시간적 해상도가 매우 높 음 : 천분의 일초 단위

• 단점: 피질 바로 아래에 있는 신경 활동은 측정가 능하나, 더 깊은 피질하 구조의 신경활동은 잘 탐 지되지 않는다.

Raw EEG

Gazzaniga et al. (2002)

EEG rhythms

International 10-20 system

The Relationship Between EEG and ERP

Static Imaging Techniques

• Examples

– MRI: magnetic resonance imaging

• 강한 자기장이 환자의 뇌를 통과할 때 회전하는 스캐 너가 뇌 조직의 분자들이 일으키는 다양한 전자기적 인 변화의 양상을 감지

• MRI에 쓰이는 자석의 자기장 = 1.5 T, 3T, 7T.

• 단위 : Tesla (1 Tesla = 10,000 Gauss)

• 지구의 자기장 = 0.5 가우스

Methods of Cognitive Neuroscience Metabolic Imaging

– Relies on changes that take place within the brain as a result of increased consumption of glucose or oxygen in active areas of the brain

• Examples

– PET: positron emission tomography 양전자 방사 단층 촬영

• 뇌 활성화 동안 포도당 소비량 증가

– fMRI: functional magnetic resonance imaging

• 뇌 활성화 동안 산소 소비량 증가

PET

생체내에 양전자를 방출하는 방사성

동위원소로 표지된 방사성의약품을

투여핚 후 양전자가 인체내의 전자와

결합핛 때 발생하는 소멸방사선을 체

외에서 검출하여 전산화 단층촬영과

유사핚 방법으로 360° 모든 각도에서

측정되는 방사능의 분포를 재구성하

여 영상화합니다.

MRI studies brain anatomy . Functional MRI (fMRI) studies brain function.

MRI vs. fMRI

BOLD signal

• Takes advantage of the different magnetic properties of oxyhemoglobin (HbO) and deoxyhemoglobin (Hb).

(Blood Oxygen Level Dependent signal )

신경세포 활성 → 과다 산소 소모로 국지적 혈류량 증 가 → 정맥혈에 산소 수치 증가 → MR 신호 증가.

TMS (Transcranial Magnetic

Stimulation, 경두개자기자극법)

• fMRI, PET

– 과제수행 A 영역 의 활성화

 TMS

 A 영역을 자극  과

제 수행이 유발되는

가?

Mark Georges, “Brain Stimulation”

Scientific American, Sep. 3

, 2003.

Magnetic Stimulation: TMS)

두부 표면에서 유도시킨 국소 자기 장 파동을 이용하여 두뇌피질을 자 극할 수 있도록 하는 새로운 비침습 적 시술 방법이다.

즉 두부 가까이에 전도 전자기 코일 을 놓고 강력한 전류파를 흘려서 생 긴 자기장으로 (자기) 두개골을 통과 시켜 (경두개) 피질

의 신경세포를 활성화시키도록 (자극) 하는 것이다…..”

http://user.chollian.net/~alberto/tm soverview.htm

BRAIN DAMAGE …

Speech production: brain mechanisms

Broca’s Aphasia

Gazzaniga et al. 2002

Broca’s Aphasia

• Patient “Tan”: Brain tumor in Left frontal brain region

• Slow speech

• Labored speech

• Little use of function words: telegraphic speech

• Language comprehension skills relatively preserved.

Broca’s Aphasia

• Broca’s aphasia is caused mainly by lesions to

1) the left frontal operculum, BA 44, 45 (Broca’s area)

2) surrounding regions of the frontal cortex & to the underlying subcortical white matter (face area of the motor cortex (BA 4), basal ganglia and insular cortex)

Broca’s Aphasia

– lesions to the left basal ganglia, especially the head of the caudate nucleus, can produce Broca’s like aphasia

Speech comprehension: brain mechanisms

Wernicke’s Aphasia

“Well this is… mother is away here working her

work out o’here to get her better, but when she’s

looking in the other part.

One their small tile into her time here. She’s working another time…”

Goodglass & Geschwind, 1976

Wernicke’s Aphasia

• Neologisms

• Fluent speech

• Unlabored speech

• Meaningless speech (Fluent nonsense)

• Preserved function words, impaired content words

• Comprehension impaired

• Even simple sentences not well understood

• Associated with left temporal lobe damage

UC Davis

• Wernicke’s aphasia is caused mainly by lesions to

1) the left superior temporal cortex, BA 41 & 42 (primary auditory cortex) or BA 22 (Wernicke’s area)

2) region caudal to Wernicke’s area (angular gyrus or posterior language area, BA 39)

Wernicke’s Aphasia

Disconnection syndromes

Lichtheim’s model of language processing

Wernicke ’s sound image Broca ’s

speech output

Concept center

Speech output Speech input Gazzaniga et al. 2002

Aphasia: Disconnection syndrome

Concept center

Broca’s area Wernicke’s area Transcortical

Motor aphasia

Transcortical Sensory

aphasia

Arcuate Faciculus

Conduction aphasia

• Conduction aphasia

• Transcortical motor aphasia

• Transcortical sensory aphasia

Conduction Aphasia

• the inability to repeat non-words or unfamiliar words, but the ability to speak normally and comprehend the speech of others

-meaningful speech -fluent speech

-comprehension

-poor repetition, repeat only if word has meaning -may repeat as word with similar meaning

Conduction Aphasia

• Conduction aphasia is caused mainly by lesions to left arcuate fasciculus; connects both Wernicke’s and Broca’s areas and

appears to convey information about sound and not meaning.

Gazzaniga et al. 2002

Transcortical Motor Aphasia

• same halting, agrammatic speech of Broca's, but may be echolalic, or able to repeat complex words and phrases.

– Halting: non-fluent speech and writing – comprehension is normal to some extent – repetition of speech is normal

– nonfluent patterns with frequent literal and verbal paraphasias

Transcortical Motor Aphasia

• Transcortical motor aphasia is caused by damage Broca's area and extend either anteriorly or superiorly deep into the underlying white matter or in the cortex.

Transcortical Motor Aphasia is caused by damage to Broca and anterior or superior

Transcortical Sensory Aphasia

• failure to comprehend the meaning of words & inability to express thoughts in meaningful speech

– repeat what others say

– cannot comprehend meaning

– cannot produce meaningful speech

Transcortical Sensory Aphasia

• Transcortical sensory aphasia is caused by damage just caudal to Wernicke’s area, the left angular gyrus (posterior language area).

Transcortical Sensory Aphasia is caused by damage to

posterior language area

Global Aphasia

• Damage to multiple components of system

– Damage to sound image and output – Leaves concepts without speech I/O

– No ability to comprehend or produce speech – Extensive lesion to left hemisphere

Global Aphasia

• Global aphasia is caused by Large lesion involving most of speech zone, or sometimes a subcortical lesion taking out most of white matter connections in perisylvian region

Best Characteristics of the Major Aphasic Syndromes

Types of Aphasia

Spontaneous Speech

Paraphasia Comprehension Repetition Naming

Broca’s Nonfluent Uncommon Good Poor Poor

Wernicke’s Fluent Common (verbal)

Poor Poor Poor

Conduction Fluent Common (literal)

Good Poor Poor

Transcortical motor

Nonfluent Uncommon Good Good

(Echolalia)

Poor

Transcortical sensory

Fluent Common Poor Good

(Echolalia)

Poor

Global Nonfluent Variable Poor Poor Poor

More aphasias!

Aphasia type Production Comprehension Repetition

1. Broca’s Non-fluent Good Poor

2. Wernicke’s Fluent,

paraphasic Poor Poor

3. Conduction Fluent,

paraphasic Good Poor

4. Transcortical

motor Terse, echolalic Good Good

5. Transcortical

sensory Fluent,

paraphasic Poor Good

6. Global Poor Poor Poor

7. Aphemia Dysarthric Good Limited only

by dysarthria 8. Pure word

deafness Normal Very poor! As if

deaf! Very poor

1 M

A 2 3

5

B

4

7 8

Converging evidence with Neuroimaging study

• Anterior – speech output – syntactic processing

• Posterior – speech comprehension – semantic processing

 Double dissociation in language processing (input-output or syntactic-semantic)

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