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Cognitive & Neuroscience Intro
• Themes
– cognitive psychology has been guided by an
information processing approach to theorizing
– this approach attempts to characterize how
information is processed from its initial input until
its response
– this approach continues to be used
Cognitive & Neuroscience Intro
• Primary measures
– Reaction time (RT)
measure the elapsed time from the onset of a stimulus
until there is a response to the stimulus
general goal of measuring RT is to make inferences
about underlying cognitive processes (which are
assumed to take time)
Cognitive & Neuroscience Intro
• Primary measures
– Accuracy
this measure assesses the accuracy of an individual’s
performance
Note: accuracy can be broadly (or narrowly) defined
e.g., verbatim versus gist recall
Cognitive & Neuroscience Intro
• Analogies
– channel capacity
early uses: attention/Broadbent
more recent uses: controlled processing
– computer analogy
serial sequential processing of information
Atkinson-Shiffrin Model
(Atkinson & Shiffrin, 1968)
Cognitive & Neuroscience Intro
• General early assumptions
– sequential stages of processing
– stages are independent
– stages are non-overlapping
Cognitive & Neuroscience Intro
• New conceptualizations
– parallel processing
e.g., typing
– hierarchical organization
e.g., typing a word
e.g., grasping an object (prepare index finger thumb
apperture as you move arm toward object)
– context effects
semantic priming
Cognitive & Neuroscience Intro
• Cognitive neuroscience intro
– neuron is the basic building block of the brain
cell that is specialized for receiving and transmitting a
neural impulse
Note: there is enormous variability in the structure of
neurons
Cognitive & Neuroscience Intro
• Development of neurons and glial cells
– germinal (or stem) cells of an embryo give rise to
two types of nervous system cells: neuroblasts
and spongioblasts (blast is an immature cell)
– neuroblasts develop into neurons
– spongioblasts develop into glial cells
glial cells provide support to neurons
Cognitive & Neuroscience Intro
• Cognitive neuroscience intro
– Major structures of a neuron
input end: dendrites, which accumulate neural
stimulation into the neuron itself
cell body or soma: regulates the biological activity
of the neuron
axon: a long tube-like structure used to transmit
information
axon terminals or terminal arborizations:output
end of the neuron, where neural impulses end
An illustration of the various structures of
the neuron. The lower diagram illustrates a
sensory-motor reflex arc
Cognitive & Neuroscience Intro
• Basic elements of nervous system
– how a simple reflex works (e.g., jerking hand
away from a hot stove)
receptor cells in hand react to physical stimulus and
that triggers a pattern of firing down a sequence of
sensory neurons
tracts of sensory neurons pass message along into the
spinal cord where it is routed to brain and back into
motor neurons
However, at the synapse the message can route
directly to the motor neurons
Cognitive & Neuroscience Intro
• Basic elements of nervous system
– motor neurons in spinal cord transmit message
back to arm muscles
– these terminate at effector cells, which connect
directly to muscle fibres and cause the muscles
to pull arm away from hot stove
– brain route: message is routed up spinal cord to
brain (CNS)
note: central nervous system = spinal cord + brain
Cognitive & Neuroscience Intro
• Basic elements of nervous system
– synapse: region where the axon terminals of one
neuron and dendrites of another neuron come
together
– synapses are small gaps between neurons
any single neuron synapses on a large number of
other neurons: called divergence (a typical neuron
synapses on from 100-15,000 other neurons)
also any single neuron is the destination of many
neurons (called convergence)
Cognitive & Neuroscience Intro
• Basic elements of nervous system
– information is transmitted across a synapse
chemically by means of a neurotransmitter
– a neurotransmitter is released from small buttons
or sacs in the axon terminals, which then fit into
receptor sites on the dendrites of the next neuron
– two types of neurons: inhibitory and excitatory
– inhibitory neurons decrease the likelihood of the
next neuron from firing; excitatory neurons have
the opposite effect
Cognitive & Neuroscience Intro
• Structure of Nervous System
– Nervous system consists of two major parts:
central nervous system (CNS) and peripheral
nervous system (PNS)
– PNS consists of: skeletal nervous system and
autonomic nervous system
– Skeletal system controls striated (i.e., striped)
muscles, which are under voluntary control, and
play an important role in motor cognition and
simulation
Cognitive & Neuroscience Intro
• Structure of Nervous System
– autonomic nervous system governs smooth
muscles and some glands
– Smooth muscles, found in heart, blood vessels,
stomach lining, and intestines, are not usually
under voluntary control
Cognitive & Neuroscience Intro
• Structure of Nervous System
– autonomic nervous system plays a key role in
emotion and affects memory functioning
– Autonomic nervous system is divided into
sympathetic and parasympathetic nervous
system
Cognitive & Neuroscience Intro
• Structure of Nervous System
– sympathetic nervous system prepares animal to
respond more vigorously in an emergency (flightor-fight response). Some changes:
– Increasing heart rate (and delivering more
oxygen and nutrients to organs)
– Increasing breathing rate (and providing more
oxygen)
– Dilating pupils (increasing sensitivity to light)
– Reducing digestive function
Cognitive & Neuroscience Intro
• Structure of Nervous System
– parasympathetic nervous system counters
sympathetic nervous system and dampens the
organism’s responses
Cognitive & Neuroscience Intro
• Cerebral cortex (Overview)
– Brain should be thought of as a collection of
components that work together
– It consists of two halves, which are called the left
and right cerebral hemispheres
– Hemispheres are connected by a massive
collection of nerve fibres called the corpus
callosum, as well as several smaller connections
Cognitive & Neuroscience Intro
• Cerebral cortex (Overview)
– Beneath the skull is a membrane covering the
brain called the meninges
– Beneath that is a network of blood vessels
clinging to the surface of the brain
– The surface of the brain contains most of the cell
bodies of the neurons, which have a gray colour,
hence the term gray matter
Cognitive & Neuroscience Intro
– Cerebral cortex
cortex: consists of 4-6 layers of cells (or gray matter)
the term cortex (bark) refers to any outer layer of cells
conventionally the terms cortex and neocortex are
used interchangeably
the cortex is wrinkled in order to increase its area
(think of crumpled paper)
Cognitive & Neuroscience Intro
• Cerebral cortex
– Clefts (indentations) in the brain are called
fissures if they extend deeply into brain or sulci if
they are shallower
– A ridge in the cortex is called a gyrus
Gyri and sulci. Lateral (A) and medial
(B) views of the gyri. Lateral (C) and
medial (D) views of the sulci
Cognitive & Neuroscience Intro
• Subcortical structures
– Beneath the cortex are found subcortical
structures and at the centre of the brain are a
series of cavities, called ventricles
– Ventricles are filled with the same fluid that is
found in the spinal cord
Cognitive & Neuroscience Intro
• hemispheres and lobes
– cortex consists of two hemispheres separated by
the medial longitudinal fissure
– each hemisphere is divided into four lobes
frontal lobe (behind forehead)
temporal lobe (underneath temples)
occipital lobe
parietal lobe
The location of the frontal, parietal,
occipital, and temporal lobes of the
brain
Cognitive & Neuroscience Intro
• Lobes
– The cognitive activities are not assigned specifically to
one of the lobes and the lobes are involved in several
cognitive activities
– A rough guide
– occipital lobes
 – processes visual input from eyes and from memory (visual
imagery, some)
 Within the occipital lobe specific different regions process
different aspects of vision (e.g., motion, color, shape)
 if occipital lobes are damaged blindness results
Cognitive & Neuroscience Intro
• Lobes
– temporal lobes
 Involved in several functions
 Retention of visual memory
 Matching visual input to visual memory
 Process input from the ears
 Posterior region of the left temporal lobe (Wernicke’s area is
crucial for comprehending language
 Anterior regions of temporal lobes are crucial for processing new
memories, deriving meaning, and processing emotion
Cognitive & Neuroscience Intro
• Lobes
– Parietal lobes
Involved in several functions
Its most anterior gyrus, the somatosensory cortex
(area S1), represents sensations on different parts of
your body with left S1 representing right side of body
and vice versa for right S1
Parietal lobes are also involved in representing space
and your relationship to it, and in representing tool
knowledge
Cognitive & Neuroscience Intro
• Lobes
– Frontal lobes
 Involved in several functions
 Managing sequences of behaviors or mental activities
 Major role in producing speech—Broca’s area of left hemisphere
 Controlling movements– area M1 (most posterior gyrus of frontal
lobes (also called motor strip); this area is immediately adjacent
to S1
 Left M1 controls movements by right part of body and vice versa
 Frontal lobes also involved in memory retrieval, in planning and
reasoning, and in some emotions
Cognitive & Neuroscience Intro
• Projection maps
– constructed by tracing axons from sensory
systems into the brain, and by tracing axons from
the neocortex into the motor systems of the brain
stem and spinal cord
Cognitive & Neuroscience Intro
• Projection maps
dark areas in figure are primary projection areas.
These areas receive input from the sensory systems
or project to the spinal motor systems
lightly shaded areas receive projections (input) from
the primary projection areas and are called secondary
projection areas
unshaded areas are called higher-order association or
tertiary areas
Cognitive & Neuroscience Intro
• Topography of the neocortex
– primary projection areas
visual system--occipital lobes
auditory system -- temporal lobes
somatosensory system -- parietal lobes
motor system -- frontal lobes
A projection map
Subcortical structures
Cognitive & Neuroscience Intro
• Subcortical areas
thalamus consists of several nuclei; all sensory
systems except for smell have relays here on their way
to cortex; also different cortical regions communicate
with each other via thalamus
Cognitive & Neuroscience Intro
• Thalamus
– consists of two symmetric nuclei at base of cerebral
hemispheres superior to hypothalamus
– each hemisphere contains half of the thalamus
– thalamus receives ascending input (sensory information)
and descending input from cerebral hemispheres,
particularly from those cortical regions to which it projects
– all sensory systems except for smell have relays here on
their way to cortex
Cognitive & Neuroscience Intro
• Thalamus
– can be thought of as a complex relay station for
sensory and motor systems except for olfaction
(smell)
– thalamus is thought to play an important role in
the classification, integration of information,
before sending it to the cortex for further
processing
Cognitive & Neuroscience Intro
• Thalamus
– Thalamus also plays an important role in
selective attention
– Pulvinar nucleus (a nucleus refers to a cluster of
cells) is involved in focusing attention
Cognitive & Neuroscience Intro
– hypothalamus composed of small nuclei; involved in
feeding, sexual behaviour, sleeping, temperature
regulation, blood pressure, heart rate, etc.
– Some of these functions are accomplished by hormones
(chemicals that affect various organs)
– Hippocampus located at the anterior end of the temporal
lobes; it plays a central role in entering new information
into memory although it is not where memories are
stored; it governs processes that allow memories to be
stored
Cognitive & Neuroscience Intro
– Amygdala (named, from Greek, because of its
almond shape) plays an important role in the
appreciation of emotion in others and in the
expression of our own emotion (esp. fear)
– The amygdala can modulate the functioning of
the hippocampus; this helps you store vivid
memories of highly emotional information
– The amygdala and hippocampus along with other
structures are part of the limbic system, which
used to be thought to regulate emotion
Model of the human limbic system
and its major structures
Cognitive & Neuroscience Intro
• Basal ganglia
– collection of nuclei lying beneath the anterior
regions of the neocortex
include the putamen (shell), the globus pallidus (pale
globe), the caudate nucleus (tailed nucleus), and the
amygdala (almond). [Note: striatum = putamen +
caudate; globus pallidus = pallidum]
caudate nucleus receives projections from all parts of
the neocortex and then projects through the putamen
and globus pallidus to the thalamus, and then to the
motor areas of the cortex
Cognitive & Neuroscience Intro
• Basal ganglia
basal ganglia also has reciprocal connections to the
substantia nigra (black area)
this projection provides dopamine to the basal ganglia;
when dopamine is lost a motor disorder called
Parkinson’s disease results
Cognitive & Neuroscience Intro
• Basal ganglia
– functions of basal ganglia
involved in motor function--including postural changes,
sequencing of movements into a smoothly executed
response, and habit learning
Habit learning (e.g., development of routinized
activities such as coming to this lecture hall)
Relation between the basal ganglia and the
cortex. Arrows indicate theoretical
projections of the various areas into basal
ganglia structures
Cognitive & Neuroscience Intro
• Brainstem
– Includes the pons and medulla and reticular
formation
– regulates many movements of animals
– responds to sensory features of the environment
– regulates eating, sleeping, drinking, body
temperature
The three divisions of the brain
Cognitive & Neuroscience Intro
• Topography of the neocortex
– The remaining functional neuroanatomy slides,
about 6, contain additional useful, reference
information
– You will not be tested on this material
Medial view through the center of
the brain showing structures of the
brainstem
Cognitive & Neuroscience Intro
• Topography of the neocortex
– cytoarchitectonic maps
constructed by examining the neurons in the neocortex
to identify regions that have unique organization
the best known of these is called Brodmann’s map
shown in Figure 3.9
Brodmann’s areas of the cortex
Cognitive & Neuroscience Intro
Function
Brodmann area
Vision, primary
17
Vision, secondary
18,19, 20, 21,37
Auditory, primary
41
Auditory, secondary
22, 42
Body senses, primary
1, 2, 3
Body senses, secondary
5, 7
Cognitive & Neuroscience Intro
Function
Brodmann area
Motor, primary
4
Motor, secondary
6
Eye movement
8
Speech
44
The First “Brain Imaging Experiment”
… and probably the cheapest one too!
Angelo Mosso
Italian physiologist
(1846-1910)
E = mc2
???
“[In Mosso’s experiments] the subject to be observed lay on a delicately balanced table which could tip
downward either at the head or at the foot if the weight of either end were increased. The moment
emotional or intellectual activity began in the subject, down went the balance at the head-end, in
consequence of the redistribution of blood in his system.”
-- William James, Principles of Psychology (1890)
Courtesy: J. Culham, Robarts Research Institute
Brain imaging and cognition
• Brain imaging techniques
– early 1970s x-ray computed tomagraphy or x-ray
CT technique developed
– when highly focused x-rays are passed through
the body, the beam is affected in predictable
ways by the relative density of the tissue
– by passing a beam through the body at many
different angles it becomes possible (using
sophisticated math techniques) to re-construct an
image of the body
Brain imaging and cognition
• Brain imaging techniques
– this technique led to the development of Positron
Emission Tomography (PET)
– PET also built on a technique known as
autoradiography
Brain imaging and cognition
• autoradiography
radioactive labeled compound is injected into
organism
experiment is performed
organ is removed and sectioned
individual slices are placed on film which is
sensitive to radioactivity
Brain imaging and cognition
• PET
– PET also uses radioisotopes but does not require
organs to be removed
– PET uses radioisotopes that have positrons that
emit gamma radiation that can be detected by
sensors outside of the head
Brain imaging and cognition
• PET (how it works)
– a PET camera is a set of radiation detectors that
circle the subject’s head
– subject is injected with positron-emitting
radioactive isotope oxygen-15 (half-life about 2
minutes)
– radioactive water accumulates in brain in
proportion to the local blood flow
– the greater the blood flow the more radiation
counts recorded by PET
Brain imaging and cognition
• PET (experimental strategy)
– Paired image subtraction
record image of subject while she is performing an
experimental task
record image of subject while she is performing a
control task
(e.g., dots in motion - stationary dots)
difference tells us what brain regions are
associated with representation of motion
Brain imaging and cognition
• PET (experimental strategy)
– to eliminate noise or random variation, the
differenced images are averaged across subjects
– the slide on the following page illustrates the
strategy
row 1-- experimental - control = difference
row 2 -- individualized difference images
row 3 -- mean difference image
Brain imaging and cognition
• Disadvantages of PET
– Invasive
– Poor temporal resolution
– Expensive
Brain imaging and cognition
• What is MRI and fMRI
– MRI uses strong magnetic fields to create images of
biological tissue
– The strength of the magnetic field created by an MRI
scanner is measured in Tesla
– MRI scanners are typically 1.5 – 3.0 Tesla (earth’s
magnetic field is 0.00005 Tesla
– Refs: Smith and Kosslyn (2007); Huettal, Song, McCarthy
(2008) functional magnetic resonance imaging
Brain imaging and cognition
• What is MRI and fMRI
– To create images the scanner uses a series of changing
magnetic gradients and oscillating electromagnetic fields
known as pulse sequences
– These electromagnetic fields result in energy being
absorbed and then emitted by atomic nuclei in the tissue
being examined
– The amount of emitted energy depends upon the number
and type of nuclei present, thus creating an image of the
tissue being examined
Brain imaging and cognition
• What is MRI and fMRI
– MRI structures brain structure
– Important to study brain structure when it is suspected
there is neurological change to brain (e.g., stroke,
dementia)
– fMRI is designed to reveal short-term physiological
changes associated with the active functioning of the
brain; it can also reveal patterns of brain activation
associated with these changes
MRI vs. fMRI
MRI studies brain anatomy.
Courtesy: J. Culham, Robarts Research Institute
Functional MRI (fMRI)
studies brain function.
fMRI Setup
Courtesy: J. Culham, Robarts Research Institute
Brain imaging and cognition
• MRI (overview)
– many atoms in the presence of a magnetic field
behave like little bar magnets or compasses
– that is, they line up in a particular orientation
– when a radio wave is applied to this aligned
sample, the sample emits detectable radio
signals characteristic of the chemical
environment
Brain imaging and cognition
• fMRI
– functional magnetic resonance imaging
– nuclear magnetic resonance (NMR) image
intensity reflects the concentration of water in the
sample
Brain imaging and cognition
• fMRI
– To map brain function it is necessary to create
images that distinguish between active and
inactive brain regions
– Called functional contrast
– This is done by measuring the metabolic
consequences of neuronal activity
Brain imaging and cognition
• fMRI
– (BOLD) contrast is a sensitive MRI marker of
neuronal activity
– How BOLD works
– Red blood cells contain hemoglobin
– the iron ion in hemoglobin can have oxygen
bound to it or stripped off
Brain imaging and cognition
• fMRI
– How BOLD works
– When brain functions it draws in more red blood
cells than it needs; by detecting extra oxygenated
blood cells BOLD signal detects brain activity
Brain imaging and cognition
• fMRI
– transitions are induced by the application of
radio-frequency energy
– an nuclear magnetic resonance (NMR) signal is
detected
Brain imaging and cognition
• Parameters of neuroimaging data
– Spatial resolution
– Refers to the ability to distinguish between different
locations within an image
– In 2-dimensional pictures, a pixel refers to the smallest
picture element that can be resolved.
– In a satellite photo of a large region a picture element
might represent hundreds of metres, whereas a zoom
picture of a region might represent 1 metre
Brain imaging and cognition
• Parameters of neuroimaging data
– Spatial resolution
– In MR images, 3-dimensional samples of the
brain are obtained and the smallest resolvable 3D element is called a voxel; in MRI, voxels are
often 1 to 2 mm, in each dimension, whereas in
fMRI, voxels are 3 to 5 mm on each side
Brain imaging and cognition
• fMRI
– fMRI contrast is tailored to optimize the signal
dependence on deoxyhemoglobin concentration
– deoxyhemoglobin is used as a contrast agent
– this so called, blood oxygenation level dependent
(BOLD) contrast is a sensitive MRI marker of
neuronal activity
– MRI signal arises from the stimulation of
transitions of hydrogen atoms in water, placed in
a large field
Brain imaging and cognition
• Parameters of neuroimaging data
– Temporal resolution
– Factors affecting temporal resolution include:
– 1. the rate at which an imaging technique obtains
its images (sampling rate)
– 2. the sluggishness of the physiological process
being measured; in fMRI BOLD measures blood
oxygenation, a relatively slow process
Brain imaging and cognition
• fMRI (Experimental strategy)
– acquire MR images while subjects are
presented with blocks of stimulation
(experimental) for about 30 seconds
– have control or baseline activity
– subtract one from the other
Brain imaging and cognition
• fMRI
– echo-planar imaging
this technique is most commonly used to obtain
images
multi-slice EPI is acquired by first exciting an NMR
signal from a thin-slice of the head, using a shaped
RF pulse in the presence of a rapidly switched
magnetic field gradient
this generates a series of echoes of the NMR
signal that can then be used to construct a 2dimensional image of the slice
Brain imaging and cognition
• fMRI
– echo-planar imaging
volume data are built up by repeating the process
of image acquisition at different slice positions (40
slices commonly used to cover the brain)
TR refers to the time between repeated
acquisitions of the same slice
a common set of parameters is 100 ms per slice x
50 slices = 5 seconds (TR = 5 seconds)
a parameter, TE, is defined as the time needed to
generate half of the echoes for a single slice
Brain Imaging: Anatomy
CAT
Photography
PET
MRI
Courtesy: J. Culham, Robarts Research Institute
Source: modified from Posner & Raichle, Images of Mind
Brain imaging and cognition
• Disadvantages of fMRI
– Poor temporal resolution
– Machines are:
– Expensive
– Noisy
– Tube narrow, which some people find upsetting
Brain imaging and cognition
• PET and fMRI are correlational methods
– That is, they correlate areas of brain activation that
accompany information processing when performing a
task
– Correlation does not necessarily imply causation
– Brain regions that are activated may not necessarily play
a functional role in performing the task
– Hence these methods only suggest which brain regions
may process information when performing a task
Brain imaging and cognition
• PET and fMRI are correlational methods
– Data from PET and fMRI can be used to compare 2 (or
more) tasks to determine whether the same or different
brain regions are activated
– If different brain regions are activated, this suggests that
these tasks are carried out by different processes
– If the same brain regions are activated, this provides
evidence to support the claim that similar processes are
involved in performing the 2 tasks
Brain imaging and cognition
• Limitations of neuroimaging methods
– Excitatory and inhibitory activity cannot be distinguished
– More activation does not necessarily mean more processing
– Same functional areas may be located in slightly different brain areas
making averaging across participants difficult
– Brain is always active making it difficult to know what processing is
going on during ‘baseline’ condition (note: neuroimaging methods
usually involve comparison of a treatment to a control condition
– Finding of no activity is difficult to interpret—could mean process is
active in both conditions, inactive in both conditions or activation is
subtle
– Different processes appear to be implemented in the same area (e.g.,
different neurons in area 17 process colour and shape)
Brain imaging and cognition
• Other correlational methods
– Other correlational methods are called electroencephalography
(EEG); event-related potentials (ERP)
– In both of these methods electrodes are placed on the scalp
– EEG records fluctuations in electrical activity over time, at different
“bands” or sets of frequencies (e.g., 8 – 12 cycles per second)
– ERP uses electrodes to observe fluctuations in activity relative to
presentation of a stimulus (e.g., P300 is a positive fluctuation that is
observed 300 milliseconds after a stimulus
– Both ERP and EEG have disadvantages: 1. Both are sensitive to
muscle twitches because muscles produce electrical activity when
they twitch; 2. spatial resolution poor because electrical activity
detected comes from spatially distributed regions
Method
Spatial Res
EEG
Poor (1
inch)
ERP
Poor (1
inch)
PET
Good (about Poor
1cm)
Good (about Poor
.5 cm)
fMRI
Temporal
Res
Excellent
(ms)
Excellent
(ms)
Invasiveness
Low
Low
High
Low
Brain imaging and cognition
• Causal neural methods
– It is also possible to use other methods to establish
causal connections between brain activation and
behavioral performance
– Classic method is the neuropsychological patient study
– Logic is straightforward—if a brain region plays a key role
in carrying out a task, a patient with damage to that
region should be impaired in carrying out that task
Brain imaging and cognition
• Causal neural methods
– Brain damage can occur for a variety of reasons
including:
– Stroke or other medical conditions that result in disruption
of blood flow to the brain (e.g., heart attack)
– Brain surgery (e.g., to remove a tumor)
– Traumatic brain injury (e.g., MVA, assault)
– Brain-damaging toxins (e.g., certain drugs including
alcohol)
– Brain-damaging diseases (e.g., Alzheimers, Parkinsons)
Brain imaging and cognition
• Causal neural methods
– Limitations of neuropsychological studies
– Brain damage usually affects a large area of
neural tissue
– It is possible that brain damage results in a
change in the functioning of the brain as a whole
Brain imaging and cognition
• Causal neural methods
– Lesions indicate necessity of region, but not sufficiency;
i.e., other brain regions may also be necessary for
function
– E.g., think of a radio that won’t play music; examination of
the radio revealed that its speakers were broken;
conclusion that speakers are necessary for music to play
is correct; however, it does not mean that a radio with
undamaged speakers will necessarily play (e.g., think of a
radio with a broken switch)
Brain imaging and cognition
• Causal neural methods
– Note: a given brain region may have more than
one function
Brain imaging and cognition
• Causal neural methods
– Another causal neural method is Transcranial magnetic stimulation
(TMS)
– In this method brain processes of a small, circumscribed area of the
brain are disrupted (1 cubic cm)
– A coil is placed on the participant’s head and a current is run through
the coil, which disrupts the neural areas of the brain beneath the coil
– 2 versions of TMS
– Single pulse TMS delivers a single pulse to specific brain area;
repetitive TMS (rTMS) delivers a series of pulses to specific brain
area before a task is performed
– If enough pulses are delivered, this has the effect of temporarily
disrupting neural processing of specific brain area (like inducing a
specific lesion)
Brain imaging and cognition
• Causal neural methods
– Limitations of rTMS
– Stimulating 1 brain area can affect other areas
making it difficult to infer which area is
responsible for effects
– rTMS can induce seizures if it is not used
according to safety guidelines
– rTMS can be used to investigate only those
regions directly below the skull
Brain imaging and cognition
• Limitations of neuroscience methods
– As this overview shows, each neuroscience
method has strengths and weaknesses
– This is why neuroscientists rely on evidence from
a variety of different methods (converging
evidence) to understand which cognitive
processes and brain regions perform specific
tasks
–