Behavioral Neuroscience

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Behavioral Neuroscience Neurology

• Lesion studies
• Animals
• Patient case studies
• Phineas Gage
• H.M.
• Single cell recordings
• Behavioral studies
• TMS (Transcranial Magnetic Stimulation)
• Creating artificial temporary lesions in the
  brain

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Transcranial Magnetic Stimulation (TMS)

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Cognitive Neuroscience

• STRUCTURAL Neuroimaging
• CT (Computerized Tomography)
• MRI (Magnetic resonance imaging)
• 3-D combine x-ray or MRI slices
• FUNCTIONAL Neuroimaging
• EEG (Topography) 1929
• MEG (Magnetoencephalogram)
• PET (Positron Emission Tomography 1970s)
• cerebral glucose levels
• high spatial resolution but low temporal and
  invasive
• fMRI (functional MRI) 1990s

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functional Magnetic Resonance Imaging (fMRI)

• Measures cerebral hemodynamic response (BOLD
  signal)
• Blood flow in brain levels of oxygen in
  (deoxy)hemoglobin recruited by firing neurons
• Structure AND function in single scan
• High spatial resolution with modest temporal
  resolution
• Problem loud scanner noises, machine artifacts

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MRI physics
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Conventional MRI
white matter
gray matter

• MRI is sensitive to myelin

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HIGH Spatial Resolution of MRI
Histology
MRI
Layer IV
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MRI vs. fMRI
MRI - shows difference between different types of
tissues (difference in space, e.g. white vs.
gray matter)

• fMRI
• shows difference between stimulated and
  non-stimulated tissue (difference in time)

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What is functional MRI (fMRI)?
Stimulus Off (Condition 1)
T2 (tissue at rest)
MR signal
time
fMRI detects subtractive difference in signal
(?S Cond. 2-Cond.1) fMRI is indirect
(hemodynamic) method of cellular communication
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Structural MRI Functional MRI
Anatomical MRI (T1-weighted)
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Spatio - temporal scales
MEG / EEG
Spatial Resolution (mm)
PET
fMRI
Single / Multi Unit Recording
1 msec 1 sec 1 min
10 min 1 hour
Temporal Resolution (sec)

• Why fMRI?
• non-invasive gt can be used in humans
• measures population neural activity
• can study whole brain at once

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MRI scanner

• Magnetic field
• is VERY STRONG ( 3T 30,000 times the earths
  magnetic field)
• is ALWAYS ON

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Image Artifacts and Subject Safety
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Typical fMRI experiment
Stimulus
Stimulus
Stimulus
Stimulus
Off
Off
On
On
(30 s)
(30 s)
(30 s)
(30 s)
.

.

.

• Stimulus (e.g. music) is presented to subject
  repeatedly every 30 sec.
• Images are acquired 2 sec.

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Scanner Noise

• Scanner noise sources
• scanner cooling system (ongoing)
• gradient coils (every image acquisition)
• Noise is a PROBLEM
• want response to stimulus, get response to
  stimulusscanner noise
• scanner noise reduces dynamic range of response
• scanner noise masks stimulus
• Solutions
• blocking noise transmission to the subject
  (earplugs, earmuffs)
• modifying scanner
• modifying experiment

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Subcortical Activation
MGB
IC
SOC
CN
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Inferior Colliculus
(sound intensity varied)
75 dB SL
55 dB SL
35 dB SL
Inferior Colliculi
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Auditory Cortex
auditory cortex
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Millisecond changes in electrophysiology (ERPs)
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Functional Neuroimaging Resolution
Spatial Temporal
EEG/MEG 1-3 cm2 1 ms
PET 3 mm3 20 s ( 3-8 s lag)
fMRI 1 mm3 2 s ( lag of 3-8 s)
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Dis/Advantages of each technique
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Mind vs Brain
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• VHS 1518.25 Dr Phil- Cognitive Neuroscience