Cognitive Neuroscience Flashcards
cognitive neuroscience
study of nervous system to understand cognition
difference between psychology and neuroscience studies
different tools and methodologies
3 possible connections between mind and brain
- mind and brain are separate
- mind is a by-product of the brain (epiphenomenon)
- mind and brain are 2 aspects of the same thing
dualism
mind and brain are separate
parallelism
mind and brain are 2 aspects of same thing
localization of function
specific functions take place in specific brain areas
lateralization
specific functions are located in one hemisphere of the brain
contralateral control
brain controls opposite side of body (ie. motor control)
hemispheric specialization
hemispheres do specific things
is language restricted to one hemisphere?
no, both hemispheres have language capabilities
Mcgilchrist
looked at anatomical differences between left and right hemispheres
difference in attention between 2 hemispheres
right = sustain broad alertness left = sharply focused attention
anatomical difference between 2 hemispheres
broader at back on left
broader at front on right
what does the combination of both hemispheres allow for?
empathy
plasticity
ability of brain to change as result of experience
neuronal plasticity
neurons are plastic (eg: synapse regeneration)
brain plasticity
new pathways and connections in the brain
structural plasticity
ability of brain to create new pathways
functional plasticity
ability of brain to move functions from one part of the brain to another
most important age for plasticity
childhood and adolescence
is plasticity just neurons
no, glial and vascular cells as well
amount of neurons in the brain
10-100 billion
amount of glia cells
1-50X as many as neurons
number of synapses
0.15 quadrillion
layers of cortex
6
dendrites
receive info and bring to cell body
soma
contains nucleus
nodes of Ranvier
where action potential happens and propagates
what does myelin do to the electrical signal
speeds it up
CT scan
computer axial tomography
tomographic image
a 3D image made from 2D sections
what is a CT scan a form of?
an X-ray
what type of X-ray is used in a CT scan
a moveble x-ray
3 important parts of CT scan
- moveable x-ray source
- x-ray center (opposite side)
- computer
advantage of CT
see inside a living thing without cutting it
disadvantage of CT
receive x-ray radiation
good use for CT
finding a tumor or a lesion
PET scan
positron emission tomography
is PET invasive or non-invasive
slightly invasive, less than a CT scan though
how does a PET scan work?
radioactive glucose consumed and shows where blood flow is
subtraction technique
give people one task, and the task you’re interested in. Subtract PET scan of the 2 to find area of interest
MRI
magnetic resonance imaging
how does an MRI work
brief, powerful magnets cause oxygen atoms to aline
fMRI
moving images show active neurons consuming oxyhemoglobin
how does the spatial resolution of MRI compare to CT scans
better
is MRI invasive
no
what is the downside to MRI?
expensive
EEG
ElectroEncephaloGram
is EEG invasive?
completely non-invasive
how does an EEG work?
electrical activity recorded at the scalp
downside of EEG
a column of brain tissue is recorded and a 2D image is produced. can’t look deep into the brain
ERP
event related potential
how does ERP work
averages EEG patterns to find characteristic peaks and valleys after stimulus onset
what is ERP useful for
defining brain activity at the immediate point of a stimulus
advantage
cheaper than MRI or PET
2 pieces of info from ERP
lag time (in ms) and if the potential is positive or negative
MEG
MagnetoEncephaloGraphy
what does MEG do
direct measure of neural activity using magnetic fields at the scalp
how does MEG spatial resolution compare to MRI
just as good
how does MEG temporal resolution compare to fMRI
10X faster
downsides to MEG
study only surface tissue and very expensive
DTI
diffusion tensor imaging
what is DTI a form of?
MRI
what does DTI show
axonal organization
organization of connections in the brain
does DTI measure neuronal activity
no it measures motion water molecules through diffusion in axons
advantage of DTI over MRI
shows what parts of the brain are connected
PDP
parallel distributed processing
3 principles of PDP
- all representations are distributed (not local)
- storage is between units (not in units)
- learning happens gradually
storage is between units
memories and knowledge are stored in connections between units
all representations are distributed
information in the brain is distributed everywhere
learning happens gradually
after repeated exposures of a presentation, the system changes and a memory is formed
what are nodes and connections represented as in neural networks?
nodes = circles lines = connections
what shape is a neural network
N by N matrix
how is information altered in neural networks
repeated flow through of information
mental states in neural networks
N-dimensional vectors
transcranial magnetic stimulation
2T current causes neurons to fire, inhibiting or creating behavior
how strong is the TMS current
twice the strength of the earth’s magnetic field
single dissociation
lesion in structure A impairs function X but not function Y
double dissociation
lesion in structure A impairs function X but not function Y, lesion in structure B impairs function Y but not function X
Capgras delusion
person believes someone close is an imposter
how many Capgras people have head trauma
1/3
Freudian explanation of capgras
Oedipus complex surfaces after blow to the head. Rationalizes this by claiming his parents are imposters
Ramachandran explanation of capgras
temporal lobe allows person to recognize family. but lesions to amygdala connection prevent an emotional connection
further evidence in David case study of Capgras
recognized his parents on the phone. connection from auditory cortex to amygdala wasn’t severed
2 main ideas of representation
- localized representation
2. distributed representation
specificity encoding
2 different experiences happen in 2 different neurons
temporal coding
neurons don’t differentiate experiences, speed of APs do
population coding
combination of neurons that fire determines experience
sparse coding
each item encoded by smaller amount of neurons, with stronger activation
temporal sparse coding
time period of small number of neurons
types of localized representation
- specific (ie. individual neurons)
2. broad (ie. hemispheres)
grandmother cell
one cell per perception
feature detectors
different types of neurons detect different orientations at different intensities
who came up with the cognitive model of modularity
Fodor
domain specific modularity
distinct modules in the brain have different functions
fusiform face area
right side of brain in temporal lobe
recognizes objects and faces
parahippocampal place area
creates a map of visual scenes
extrastriate body area
recognizes body and body parts
Broca’s area
frontal lobe, left hemisphere
speech production
Wernicke’s area
left auditory cortex
understanding written and spoken language
distributed representation
one experience has many features and can’t be localized
brain weight
1.4 kg (2% of body)
brain energy use
25% of body
brain surface area
2000 cm squared
cortex thickness
2-5 mm
amount of Canadians with brain disease
10 million (1 in 3)
percent of brain that is water
75%
3 brains
- hindbrain
- midbrain
- forbrain
4 lobes
occipital, parietal, temporal, frontal
3 fissures
longitudinal, central, lateral
longitudinal fissure
between 2 hemispheres
central fissure
separates frontal and parietal lobes
lateral fissure
separates temporal lobe from rest of brain
how much brain do you need?
150 g
Bayesian probability
model to predict human movement
2 sources of information to make beliefs
- sensory input
2. prior knowledge
