Transcript Megans Reviewx - U of L Class Index

Cognitive Neuroscience
NEUR 3860
Review Session
October 19, 2009
Megan Metzler
[email protected]
Outline
• History of neuroscience
• Techniques of cognitive neuroscience
• Vision
History of Neuroscience
TIMELINE
1600s
• Scientific Revolution
• Dualism vs. Monistic Materialism
Late 1700s to early 1800s
• Phrenology vs. Aggregate Field Theory
Late 1800s to early 1900s
• Darwinism
• Lesion studies (Broca & Wernicke)
• Neuron hypothesis
• Cytoarchitectonics
History of Neuroscience
Scientific Revolution
Scholasticism
Empiricism
authority
direct observation (falsifiability, mathematical
measurement, peer review, skepticism, parsimony)
animism
mechanism
Dualism vs. Monism
Cartesian Dualism
Monism
Separation between mechanistic
and conscious processes
Experience= Brain Function=
Consciousness
Forms of same argument persist
today: e.g. predicate dualism,
property dualism
Sutherland’s 2 sides of the
same coin analogy
• Rene Descartes, Galileo
History of Neuroscience
• Phrenology- organization of the brain around
≥ 35 functions
– Franz Joseph Gall & J. C. Spurzheim
– Surface of the skull revealed relative use of the
functional area underneath it; size is usedependent
• Aggregate Field Theory- the whole brain
determines the whole of behaviour
– Marie-Jean-Pierre Flourens found that regardless
of where a bird’s brain was lesioned, it recovered.
History of Neuroscience
Darwinism
• Natural selection- favorable, inheritable traits
spread in a population
• Supports Monism
• Comparative study between humans and
other organisms feasible
• Processes may be adaptive (over geological
time)
• By extension supports Functional Design
– “Mechanism” transforms “target” system to
create a “desired state”
History of Neuroscience
Lesion Studies
• Broca
• Wernicke
Neuron Hypothesis
• Golgi invented the silver stain
• Ramon y Cajal used the stain to
differentiate individual
neurons
History of Neuroscience
Cytoarchitectonics
• Cellular architecture
• Brodmann- organized cortex into 52 regions
based on neuronal differences highlighted by
staining
History of Neuroscience
QUESTIONS
Short Answer:
1. The view that those in authority are the best source
of knowledge is called ____________.
2. Darwin’s theory of evolution assumes that
mechanistic processes are solely responsible for the
development of all species, consequently supporting
___________ while disputing dualism.
3. The view that the whole brain participates in
behaviour is called _____________ theory.
4. Brodmann developed a _______________ map using
the method of _________ ___________.
History of Neuroscience
QUESTIONS
Short Answer:
1. The view that those in authority are the best
source of knowledge is called Scholasticism.
2. Darwin’s theory of evolution assumes that
mechanistic processes are solely responsible for
the development of all species, consequently
supporting Monism while disputing dualism.
3. The view that the whole brain participates in
behaviour is called Aggregate Field theory.
4. Brodmann developed a cytoarchitechtonic map
using the method of tissue staining.
History of Neuroscience
QUESTIONS
Multiple Choice:
5. According to Cartesian dualism
a) The processes that underlie consciousness are
mechanistic.
b) Human consciousness cannot be understood by
mechanistic processes because it is not mechanistic.
c) Spirit-like and mechanistic properties coexist in all
matter.
d) Empirical and authoritative perspectives are
complementary.
History of Neuroscience
QUESTIONS
Multiple Choice:
5. According to Cartesian dualism
a) The processes that underlie consciousness are
mechanistic.
b) Human consciousness cannot be understood by
mechanistic processes because it is not mechanistic.
c) Spirit-like and mechanistic properties coexist in all
matter.
d) Empirical and authoritative perspectives are
complementary.
History of Neuroscience
QUESTIONS
6. The most significant contribution to neurology in
the 19th century was:
a) Phrenology and resultant methods to identify
varying development of specific cognitive
abilities across individuals.
b) Animal research with pigeons which studied
the behavioural effects of localized lesions.
c) Use of the “the black reaction” to differentiate
individual neurons.
d) Detailed anatomical drawings of the human
brain.
History of Neuroscience
QUESTIONS
6. The most significant contribution to neurology in
the 19th century was:
a) Phrenology and resultant methods to identify
varying development of specific cognitive
abilities across individuals.
b) Animal research with pigeons which studied
the behavioural effects of localized lesions.
c) Use of the “the black reaction” to
differentiate individual neurons.
d) Detailed anatomical drawings of the human
brain.
Techniques of Cognitive Neuroscience
Cellular Connectivity
• Tracers
• Diffusion Tensor Imaging
Structural and Functional Imaging
• Magnetic Resonance Imaging
• Functional MRI
• Positron Emission Tomography
Electrophysiology
• Intracranial Cell Recording
• Electroencephalography
• Magnetoencephalography
Lesion studies
Cellular Connectivity
General Principles
• High degree of interconnections in the brain
which is likely responsible for cognition
• Prime example: in the visual system there is
estimated to be 10 descending projections for
each ascending projection  also highlights
the limitations associated with structural
assessment techniques
Cellular Connectivity
Tracers
• Provide clues to connectivity at the cellular level
– Brodmann map reflects function
• Retrograde tracers
– e.g. horseradish peroxidase
• Anterograde tracers
Cellular Connectivity
Diffusion Tensor Imaging
• Uses MRI to trace long
white matter tracts
– Takes advantage of how
water movement is
restricted within axons
– Identifies the movement
of protons between
magnetic pulses and
identifies non-random
patterns
Structural and Functional Imaging
General Principles
• Importance of co-registering structural and
functional images
– Resolution of structural techniques combined with
change detected by functional technique
• Functional images relay information about
electric fields, magnetic fields, oxygenated blood
• Correlation does not determine causation
• Common language of describing location in the
brain
–
–
–
–
Reported as voxels (volumes, slices, pixels)
Talairach Coordinate System
Montreal Neurological Institute (MNI) Template
MNI “Representative” Brain
Structural and Functional Imaging
Magnetic Resonance Imaging
(MRI)
• Uses magnetic energy to
move protons in hydrogen
atoms into alignment with
the magnet. Radio waves
nudge the protons out of
alignment (property called
nuclear magnetic
resonance). When the
radio waves stop, the
protons move back to their
original position, releasing
energy which is measured
• Resolution= 1 mm3
Structural and Functional Imaging
functional MRI
• Blood oxygenation level-dependent (BOLD) effect:
change in the ratio of oxygenated to deoxygenated
hemoglobin
• Resolution= 3mm3
Positron Emission Tomography (PET)
• Inject a radioisotope (usually of oxygen) and monitor
concentration of decaying tracer (gives off gamma rays
in a predictable pattern)
• Resolution of 5-10 mm3
Functional Imaging
Study Design
• Blocked design- alternates between rest and
active conditions
Electrophysiology
General Principle
• Based on the principle that neurons exhibit
graded potentials and action potentials
Intracranial Cell Recording
• Use single or multiple electrodes to measure
action potentials from a single neuron or a
population of neurons.
• Raw data depicted as a “spike train.”
Electrophysiology
Methods
• Intracranial electrodes
• Subdural grid
• Electroencephalography
• Magnetoencephalography
(related but not technically measuring
electrical fields)
(This should look familiar)
Electroencephalography
• The field generated by a patch of cortex can be
modeled as a single equivalent dipolar current source
with some orientation (assumed to be perpendicular
to cortical surface)
(This should look familiar)
Magnetoencephalography
• For any electric current, there
is an associated magnetic field
Electric
Current
• magnetic sensors called
“SQuID”s can measure very
small fields associated with
current flowing through
extracellular space
Magnetic
Field
SQuID
Amplifier
Electrophysiology
Study Design
• Event Related Potential (ERP)
Electrophysiology
Localization
• Few methods that apply to EEG and MEG
– Plot oscillations across sensors as a 2D map, called
an isopotential map
– Brain Electrical Source Analysis
• Identify 3D generator source through modelling neural
activity as one or more equivalent current dipoles
– Beamforming
• Signal processing technique that adjusts the signal
recorded at each sensor to tune the array to a single
voxel at a time
– Possible to coregister with structural image (MRI)
Lesion Studies
Methods- Animals
– Aspiration
– Electrolytic
– Vascular lesions (e.g. endothelin 1- stroke)
– Reversible
– Selective pathways (e.g. MPTP- Parkinsons)
– Transgenic animals (Gene knock-Out, Knock-In)
• Selectively block specific receptors
• ASSUMES that behavioural change after a
lesion reveals function of the damaged area.
– Issue of interconnectivity
Lesion Studies
Methods- Humans
– Ischemic/Hemorrhagic
Stroke
– Trauma
– Surgery
– Reversible Lesion
• Transcranial Magnetic
Stimulation
Lesion Studies
Study Design
• Double Dissociation
– Single dissociation may be due to the different sensitivities
of the two tasks
Speech Output Score
Verbal Comprehension Task
Left inferior frontal lobe
damage (Broca’s)


Controls




Left posterior parietal lobe
damage (Wernicke’s)
– Allows demonstration that the damaged area contributes
to the task in some way (cannot state that the area is
responsible)
Techniques of Cognitive Neuroscience
Techniques of Cognitive Neuroscience
QUESTIONS
Multiple Choice:
1. You plan to write a study proposal for a project that
hypothesizes a positive relationship between
connectivity of the prefrontal lobe and visual cortex
and success in complex spatial tasks. What is the best
technique to apply to your particular research
hypothesis?
a) Diffusion Tensor Imaging and a measure of spatial
ability
b) fMRI and a measure of spatial ability
c) Electroencephalography and a measure of spatial
ability
d) Positron Emission Tomography and a measure of
spatial ability
Techniques of Cognitive Neuroscience
QUESTIONS
Multiple Choice:
1. You plan to write a study proposal for a project that
hypothesizes a positive relationship between
connectivity of the prefrontal lobe and visual cortex
and success in complex spatial tasks. What is the best
technique to apply to your particular research
hypothesis?
a) Diffusion Tensor Imaging and a measure of spatial
ability
b) fMRI and a measure of spatial ability
c) Electroencephalography and a measure of spatial
ability
d) Positron Emission Tomography and a measure of
spatial ability
Techniques of Cognitive Neuroscience
QUESTIONS
2. You plan to write a study proposal for a
project that hypothesizes that premotor areas
respond as part of the “first wave” following a
tactile stimulus. What is the best technique
and study design to apply to your particular
research hypothesis?
a) fMRI with a blocked design
b) fMRI with ERP
c) Electroencephalography with a blocked
design
d) Electroencephalography with ERP
Techniques of Cognitive Neuroscience
QUESTIONS
2. You plan to write a study proposal for a
project that hypothesizes that premotor areas
respond as part of the “first wave” following a
tactile stimulus. What is the best technique
and study design to apply to your particular
research hypothesis?
a) fMRI with a blocked design
b) fMRI with ERP
c) Electroencephalography with a blocked
design
d) Electroencephalography with ERP