Transcript Figure 1

뇌 생체신호의 특성과 측정법
이경민
서울대학교 의과대학 신경과
대학원 인지과학 협동과정
기능적 신경해부 (대뇌피질)
• 대뇌피질의 기능적, 계층적 구분
– primary sensory & motor cortex
– unimodal association cortex
– heteromodal association cortex
– paralimbic cortex
– limbic areas
• 사람의 대뇌피질의 특징
– 전두엽의 상대적 발달
– 연합영역의 발달
대뇌피질의 구조
- Topologically a two-dimensional sheet
- Cytoarchitectonically differentiated six layers
- Functional unit = vertical columns = columnar organization
뇌기능 연구 방법 – cognitive neuroscience
• 뇌활동양상 관찰
– 신경활동기록
• 신경단위기록 (neural recording)
• 뇌파 (EEG)
• 뇌자도 (MEG)
– Functional neuroimaging
• PET
• Functional MRI
• 뇌병변에 의한 행동변화 관찰
– 병변 연구
• 동물: 인위적 병변 조작
• 사람: 신경심리검사
– TMS (transcranial magnetic
stimulation)
후두엽 병변에 의한 임상 증상
• 후두엽 소재 기능
– 시각
• 후두엽 손상 시 관찰되는 증상들
– 시야결손(visual field defect) : homonymous hemianopia
• 망막부터 일차시각피질에 이르는 시각 경로의 손상
– 피질맹(cortical blindness)
– 시각인지장애 (visual agnosia): V1보다 상위 시각 영역
• prosopagnosia, object agnosia, alexia
• achromatopsia, akinematopsia
– 환시 / 착시 (visual hallucination / delusion)
1 = central scotoma secondary to optic neuritis (does not respect the vertical meridian)
2 = Total blindness of the right eye from a complete lesion of the optic nerve
3 = Bitemporal hemianopia from a complete lesion of the optic chiasm
4 = Right nasal hemianopia from a perichiasmal lesion
5 = Right homonymous hemianopia from a complete left optic tract lesion
6 = Right homonymous superior quadrantopia caused by partial involvement of the optic radiation in the left temporal lobe (Meyer's loop)
7 = Right homonymous inferior quadrantopia caused by partial involvement of the optic radiation in the left parietal lobe
8 = Right homonymous hemianopia from a complete lesion of the left optic radiation
9 = Right homonymous hemianopia (with macular sparing) from a posterior cerebral artery occlusion causing ischemia of the calcarine cortex
Differential impairments of visual function by ventral vs dorsal lesions
Ventral lesion: dysfunction in object identification and perceptual awareness
Dorsal lesion: dysfunction in spatial tasks and visuo-motor coordination
Line cancellation test
Object-based neglect
빨강 노랑 파랑 노랑 빨강 파랑 파랑 노랑 빨강 노랑
빨강 파랑 노랑 빨강 파랑 빨강 노랑 노랑 파랑 파랑
빨강 파랑 노랑 파랑 빨강 노랑 빨강 파랑 노랑 빨강
빨강 노랑 파랑 빨강 노랑 빨강 파랑 노랑 빨강 노랑
노랑 빨강 파랑 노랑 파랑 노랑 빨강 파랑 파랑 빨강
빨강 노랑 파랑 노랑 빨강 노랑 파랑 빨강 파랑 노랑
빨강 노랑 파랑 노랑 빨강 파랑 파랑 노랑 빨강 노랑
빨강 파랑 노랑 빨강 파랑 빨강 노랑 노랑 파랑 파랑
빨강 파랑 노랑 파랑 빨강 노랑 빨강 파랑 노랑 빨강
빨강 노랑 파랑 빨강 노랑 빨강 파랑 노랑 빨강 노랑
노랑 빨강 파랑 노랑 파랑 노랑 빨강 파랑 파랑 빨강
빨강 노랑 파랑 노랑 빨강 노랑 파랑 빨강 파랑 노랑
Neural signals
-Spiking activitiy
-Local field potential
Optical imaging wavelengths and corresponding pointspreads.
Sirotin Y B et al. PNAS 2009;106:18390-18395
©2009 by National Academy of Sciences
Spectral decomposition of imaging signal shows no increase in HbR during the initial dip
period as defined for the oximetric signal.
Sirotin Y B et al. PNAS 2009;106:18390-18395
©2009 by National Academy of Sciences
Figure 1 | Specificity of GE-EPI and SE-EPI.
a, b, Two slices of GE-EPI demonstrating the high functional signal-to-noise ratio (SNR) of the images,
but also the strong contribution of macrovessels.
c, Anatomical scan, SE-EPI, 250x188 mm2, 2mm slice, with time to echo (TE) and repetition time (TR)
70 and 3,000 ms respectively.
d, e, Two slices of SE-EPI showing the reduction of vascular contribution at the pial side of the cortex.
In-plane resolution 250x175 mm2, slice thickness 2 mm.
f, The anatomical scan is the SE-EPI used for obtaining the functional scans (TE/TR=48/2,000 ms)
clear visualization of the Gennari line (red arrow), the characteristic striation of the primary visual
cortex.
Functional NeuroImaging
 Functional Neurovascular imaging



PET (Positron Emission Tomography)
SPECT (Single Photon Emission
Computerized Tomography)
fMRI (Functional Magnetic Resonance
Imaging)
Functional MRI

특징(장점)
1. 방사선 조사의 위험이 없다.
2. 공간 및 시간적 해상력이 비교적 좋다.
3. 고도의 인지기능에 대한 연구가 가능하다.

1.
2.
단점
It measures surrogate signal whose spatial specificity and
temporal response are subject to both physical and
biological constraints.
This surrogate signal reflects neuronal mass activity.
fMRI의 활용분야
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1. 언어영역
2. 시지각 신경영역
3. 기억
4. 정서 및 동기
5. 뇌의 가소성과 신경망 재조직 연구
6. 뇌기능 훈련 및 치료 효과에 대한 연구
Principles of fMRI
Neural activity를 측정
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Neural activity
- local CBV
- local CBF
- local oxygenation
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1.
2.
3.
4.
5.
Intrinsic paramagnetic agent :
magnetic field inhomogeneity
유발하여 국소적인 MR signal 감소
BOLD : blood-oxygen level-dependant
말초혈관과 정맥혈 내의 deoxyHb 수치의 변화를 이용
Neural activity↑
oxyHb  deoxyHb↑
CBF excess : relatively low CMRO2
PvO2↑
T2-HSI
What do activation maps represent?
• Brain structure : information processing
input
/ local-processing capacity / output
perception / cognition
/ action
 실제는 이렇게 단순하지 않다.
• Research shows
1. subcortical input to cortex is weak; the feedback is
massive
2. Local connectivity reveals strong excitatory and
inhibitory recurrence
3. Output : changes in the balance between excitation
and inhibition
 EIN (excitation-inhibition networks)
Cortical activity
Figure 2 | Principles of excitation–inhibition circuits.
a, Model of a canonical cerebral microcircuit : three neuronal populations (supragranular-granular,
infragranular glutamatergic spiny neurons, GABAergic cells) The circuit is characterized by the presence
of weak thalamic input and strong recurrence.
b, Potential proportional and opposite-direction changes of cortical excitation (E) and inhibition (I).
Responses to large sustained input changes may occur while maintaining a well balanced excitationinhibition (up and down)
The commonly assumed net excitation or inhibition might occur when the afferents drive the overall
excitation-inhibition balance in opposite directions
Neurophysiological correlates of the
BOLD signal
• Extracellular field potential
- single unit activity
- multiple unit activity
- local field potential (LFP): perisynaptic activity of a neural population
within 0.5-3mm of the electrode tip
• BOLD responses reflect input and intracortical
processing rather than pyramidal cell output activity
• LFPs are better predictors of the BOLD response than
multiple unit or single unit spiking
• Dissociation between spikes and CBF
• Presynaptic activity increases metabolism even if the
output is inhibited
Motor-related cortical areas
Effect of change in number of alternatives (NA) on
visual activity of a visual cell in the FEF
NA effect on
pre-saccadic activity
of a motor cell in FEF
Functional difference between premotor area and SMA
Neuronal activity related to
visually-cued movement and internally-cued movement
Readiness potentials
Imagination and actual performance of movement
Timing of Activation: Single-event design
Direction
Cue (R/L)
Go
Prep.
Execution
Rest
T2* MRI signal
Scan number
Time(seconds)
TR = 2 seconds
1
2
3
6
4
5
2
6
7
8
8
MRI signal changes related to
motor preparation and execution
% signal change
101.0
100.5
100.0
99.5
1
3
5
7
Scan number
9
Areas related to motor preparation and execution
Left convexity
Medial surfaces
Right convexity
Left-hand motor Right-hand motor
Early preparation
Late preparation
Execution
Practice-induced changes in motor activation
- Long-term intensive training by string players
- Combined TMS & fMRI
Vector Shift:
Centers of gravity of TMS motor maps
Kim et al. Human Brain Mapping 2004
뇌기능 연구 방법 – cognitive neuroscience
• 뇌활동양상 관찰
– 신경활동기록
• 신경단위기록 (neural recording)
• 뇌파 (EEG)
• 뇌자도 (MEG)
– Functional neuroimaging
• PET
• Functional MRI
• 뇌병변에 의한 행동변화 관찰
– 병변 연구
• 동물: 인위적 병변 조작
• 사람: 신경심리검사
– TMS (transcranial magnetic
stimulation)