Exam I Flashcards
Early goal of neuroscience
map the brain by characterizing the effects of damage and disease
Task-based analysis
Can characterize the precise nature of deficits
Limitation: not useful for normal mental activity
Gold standard for understanding critical structures for brain function
Lesioning; causation not correlational
Baddeley & Hitch Model
Phrenology
Gall
by touching skull, you can make assessments on personality
PRESUMPTION –> brain would be bigger/smaller ; (convexities/concavities) depending on the functions you possess
Localization
localization: different aspects of brain function are governed by, and therefore localizable to different centers of the brain
Mass Action
brain function distributed throughout the cortex
Pierre Flourens
critic of phrenology (Gall’s localization)
would lesion animals in localized spots; failed to find evidence of localization (cerebral cortex)
EQUIPOTENTIALITY:
Equipotentiality
Pierre Flourens
any given piece of cortical tissue had potential to support any brain function
overtime, animals with experimental damage recovered without repair to damaged tissue itself, assumed other parts could take over
Evidence for localization
Gall “phrenology”
Paul Broca “tan”
John Hughlings Jackson “jacksonian march”
Evidence for mass action
Pierre Flourens “equipotentiality” animal lesions
Jacksonian March
John Hughlings Jackson
noticed there was a specific sequence of body parts that correlate with seizure activity traveling along motor cortex
Paul Broca
tan
language production
left frontal cortex
Factor that advanced brain studies
aseptic surgery
Method of learning a great deal about neural function
studying morphology from brain tissue under microscope
Camilo Golgi
developed a silver stain that allowed for visualization of individual neurons
BELIEVED brain was a continuous mass of tissue with a common cytoplasm
Synctyium
Santiago Ramon y Cajal
Neural Doctrine: nervous system made up of individual neurons
Neuron Doctrine
Ramon y Cajal
nervous system made up of individual neurons
Fritzch and Hitzig
reported that electrical stimulation in anterior part of dog’s frontal lobe produced movement in opposite side of body
part of body affected varied systematically with positioning of electrode
supported Jackson’s somotropic organization
Describe the process of neuronal communication
electrical-chemical transmission
(1) electrical impulses carry signals along axon
(2) chemical transmitters carry signals between neurons across synapse
Describe neuronal communication
Describe
PSP Summation
postsynaptic potential summation – EPSPs and IPSPs integrate spatially and temporally at the axon hillock
their summation determines signal
IPSP: hyperpolarization, cell further away from threshold, less likely to fire
EPSP: depolarization, generates action potential
Glutamate
EPSP
excitatory neurotransmitter
opening of Na+
GABA
IPSP
inhibitory neurotransmitter
influx of Cl- ions, hyperpolarizing cell /orK+
Acetylcholine
excitatory neurotransmitter
opening of Na+
Acetylcholine: facilitates learning and memory
• affected in Alzheimer’s Disease
Excitatory NTs
glutamate, acetylcholine
Inhibitory NTs
GABA, glycine
Neuromodulators
modulate activity in large regions rather than
strictly exciting/inhibiting specific postsynaptic neurons
dopamine, norepinephrine, serotonin
Neurotransmitters
transmitting signals between neurons
exciting/inhibiting specific postsynaptic neurons
Norepinephrine
Norepinphrine: enhances vigilance & preparation for action
Dopamine
facilitates movement, reinforces behaviors,
helps keep information in short-term (working) memory
• affected in Parkinson’s Disease (low), schizophrenia (high)
Serotonin
inhibits some behaviors; lots of other effects
• affected in Depression
Agonist
fully activates the receptor that it binds to
Antagonist
binds to a receptor but does not activate and can block the activity of other agonists
brain orientations
dorsal: top
ventral: bottom
anterior: front
posterior: back
rostral: front
caudal: back
medial: middle
lateral: side
Electrochemical communication
electrical signal propagated down axon, converted to chemical signal and transmitted across synapse
3 basic neuronal components
soma, dendrites, axon
Evolution of brain morphology
computational power of brain increased over time…more wrinkled and compacted to fit (gyrations)
optimally shaped to minimize connection distance between distant groups of neurons
Gray v. White matter
location in brain
gray matter=border=glial cells (cell bodies)
white matter=majority, middle=axons
Brain slicing
axial: top and bottom
sagittal: side and side
coronal: front and back
gyrus and sulcus
gyrus: top
sulcus: bottom
4 lobes of brain
FPOT
frontal: executive functioning
parietal: perception, making sense of world
occipital: vision
temporal: memory
central sulcus
separates frontal and parietal lobe, deep groove
separates motor and sensory cortex
precentral sulcus
primary motor cortex
postcentral sulcus
somatosensory cortex
sylvian fissure
separates parietal and temporal lobes
insula buried within it
line of Gennari
white
primary visual cortex
Brodmann
cytoarchitectonic
52 layers, based on cell morphology, density, and layering
Cytoarchitect
Brodmann
52 layers, based on cell morphology, density, and layering
Golgi stain
everything on neuron in all of its glory but not all neurons in total
Nissi stain
every cell body in total picture, can estimate how many total total
Cortical layers
six cortical layers
Striate v. motor cortex
STRIATE CORTEX - visual, line of genarri Superficial Upper Middle Deep
MOTOR CORTEX -
superficial
upper
deep
Layers: input v. output
layer 4: main input layer
layer 5: main output layer
Different functional areas show different pattern of layering and cell types
Brain area mapping
heat map = brain activation
DTI = white matter tracts along axons
Human connectome project
aims to provide an unparalleled compilation of neural data, an interface to graphically navigate this data and the opportunity to achieve never before realized conclusions about the living human brain
Brain dictionary
interactive map showing which brain areas respond to hearing different words
- –> just tied to English language?
- -> conceptual or semantic?
Topographic Functional Brain Organization
structure correlates to function
Retinotopic mapping
visual areas organize by retinotopic mapping, forming a 2D representation of the visual image formed on the retina in such a way that neighboring regions of the image are represented by neighboring regions of the visual area
radioactive glucose injected into bloodstream, developed map of retina produced by brain
adjacent neurons of the LGN project to adjacent neurons in primary visual cortex
tonotropy
tones close to each other in terms of frequency are represented in topologically neighbouring regions in the brain
Cortical homunculus
a distorted representation of the human body, based on a neurological “map” of the areas and proportions of the human brain dedicated to processing motor function
discrimination ability –> more neurons coding for adjacent areas
corpus collosum
largest bundle of myelinated axons
carries millions of axons from one hemisphere to the other
foveal vision
center of your gaze
Retinotopic organization
concave shape of retina on back of eyeball means anything perceived below the point of fixation will be projected onto upper retina, and left projected to right
adjacent neurons of the LGN project to adjacent neurons in primary visual cortex
everything in the primary visual cortex is “flipped” with respect to the visual field
Electrophysiology
measures the electrical activity of neurons, and, in particular, action potential activity
Hubel and Weisel - a neuron responded with bursts of action potentials in given angle
orientation selectivity of V1 neurons
rate coding
tuning curve
Retinotopic Receptive Fields
A single neuron in visual cortex is not responsive to all stimuli. Shape, color, orientation, contrast, movement…
Angelo Mosso
discovery that brain blood supply pulsates
brain diverts more blood to that part of brain during mental processing
PET
injected with tracer, pick up on distribution
localization of brain activity
MRI
Structural imaging
uses magnetic field and radio frequency
fMRI
BOLD blood oxygen level dependent
blood level = correlate for brain activity
Hemodynamics
Haemodynamic response (HR) allows the rapid delivery of blood to active neuronal tissues
fMRI imaging technique used to measure the haemodynamic response of the brain in relation to the neural activities
slow compared to direct neural recordings
BOLD versus spikes
SPIKES = electrical, EEG, HIGH temporal
BOLD = hemodynamics, PET/fMRI, HIGH spatial
Lesion options
tissue removal
tissue destruction
reversible lesions
tissue removal
+precise
-non-reversible
tissue destruction
exitocins: chemicals that overstimulate neuron receptor
Why was trauma site not random?
Shaken Jello Mold Inside Skull
Holbourn
Orbitofrontal and Anterior Temporal Contusions
Hemineglect
right temporal parietal damage
Visual Pathways
dorsal = where ventral = what
V1 hypercolumns
- Stereo
- Color
- Line (edge) orientation
Draw nueron
Draw
Electrochemical gradient
The active transport of ions across the cell membrane causes an electrical gradient to build up across this membrane. The number of positively charged ions outside the cell is usually greater than the number of positively charged ions in the cytosol (neg inside)
difference in charges creates voltage; voltage across membrane =membrane potential
there are less positive ions inside the cell, the inside of the cell is negative compared to outside the cell. This resulting membrane potential favors the movement of positively charged ions (cations) into the cell, and the movement of negative ions (anions) out of the cell. So, there are two forces that drive the diffusion of ions across the plasma membrane—a chemical force (the ions’ concentration gradient), and an electrical force (the effect of the membrane potential on the ions’ movement). These two forces working together are called an electrochemical gradient.
Electrochemical gradient
The active transport of ions across the cell membrane causes an electrical gradient to build up across this membrane. The number of positively charged ions outside the cell is usually greater than the number of positively charged ions in the cytosol (neg inside)
difference in charges creates voltage; voltage across membrane =membrane potential
neg inside, pos outside
mem potential favors outflux of positive ions in, and neg ions out
a chemical force (the ions’ concentration gradient), and an electrical force (the effect of the membrane potential on the ions’ movement). These two forces working together are called an electrochemical gradient.
Voltage gated channel
Chemical gated channel
Regenerative spike
opens Na+ and Ca+ voltage gated channels
depolarization
EPSP summation
temporal v. spatial summation
spatial: simultaneous activation by many presynaptic neurons
temporal: high frequency stimulation by one presynaptic neuron
Neurology
Neuroscience
Cognitive psychology
Neurology: Function and pathology of the nervous system
Neuroscience: Mechanisms of the nervous system, includes neuroanatomy, neurochem, neurophysiology
Cognitive psychology: How the mind processes information
fundus
concavity of gyrus/sulcus
Fixation point
the point that directly stimulates the fovea of the retina
rate coding
of action potentials/time
the differences in spiking frequency from different stimuli
measuring the number of these spikes that occur during a set period of time
orientation can be decoded by changes and spike rates (tuning curve)
temporal coding
When precise spike timing or high-frequency firing-rate fluctuations are found to carry information
rate coding
of action potentials/time
the differences in spiking frequency from different stimuli
measuring the number of these spikes that occur during a set period of time
orientation can be decoded by changes and spike rates (tuning curve)
Ways of examining circuitry
brain activation - heat map
myelination
dti - white matter tracts
Movement field
(neurons from primary motor cortex have a preference for the orientation of movements)
broadly tuned, very little specificity
Ways of examining circuitry
brain activation - heat map
myelination
dti - white matter tracts
Receptive field
relationship between visual stimulus and neural firing induces a metabolic demand
tuning curve
orientation can be decoded by changes and spike rates
way to describe the preferences a neuron reacts to
Population coding
summation of input from thousands of units firing
“wisdom of the masses”
Cognitive subtraction
The idea behind cognitive subtraction is that, by comparing the activity of the brain in a task that utilizes a particular cognitive component (e.g. the visual lexicon) to the activity of the brain in a baseline task that does not, it is possible to infer which regions are specialized for this particular cognitive component
fMRI and PET
fMRI designs
blocked - segregate diff cog processes into diff time periods
event-related
action potentials v. postsynaptic activity
local field potential (LFP) : summation of post-synaptic potentials
multi-unit activity (MUA) : action potential spikes
found BOLD signals more correlated to LFP
logothetis
exitocins
chemicals that overstimulate neuron receptor
nerve cells are damaged or killed by excessive stimulation
channel blockers
block action potential conduction. Only type that can affect fibers
inhibitory neurotransmitter
hyperpolarize neurons and drastically reduce probability of firing. Inactivate neuronal cell bodies, where the receptors are located and NOT passing axons
Neurotoxin
Neurotoxins are toxins that are poisonous or destructive to nerve tissue through inhibition
By inhibiting the ability for neurons to perform their expected intracellular functions, or pass a signal to a neighboring cell, neurotoxins can induce systemic nervous system arrest as in the case of botulinum toxin,[13] or even nervous tissue death
contusion
orbitofrontal and anterior temporal
Holbourn
neuropsychology
Neuropsychology is the study of the structure and function of the brain as they relate to specific psychological processes and behaviours
TMS
measure activity and function of specific brain circuits in humans
connection between the primary motor cortex and a muscle to evaluate damage from stroke
coil magnetic field is used to cause electric current to flow in a small region of the brain via electromagnetic induction.
single dissociation
double dissociation
single -manipulation leaves one cognitive function (say, A) intact whilst severing another (say, B). This indicates the functions A and B are at least partially independent.
double-
“establishing a single dissociation between two functions provides limited and potentially misleading information, whereas a double dissociation can better demonstrate that the two functions are localized in different areas of the brain
magnocellular v. parvocellular
Parvocellular: good spatial resolution
The top four are parvocellular layers
receive input from small ganglion cells
Magnocellular: good temporal resolution
LGN cells receive inputs from (large) ganglion cells
bottom 2 layers
Contralateral retina
Ispilateral retina
ipsi=same side
contra=opposite side
Center-surround receptive field
There are two types of retinal ganglion cells: “on-center” and “off-center”
on-center cell is stimulated when the center of its receptive field is exposed to light, and is inhibited when the surround is exposed to light
Off-center/surround cells stimulated when surround is exposed to light, inhibited in center
Simple cell
Complex cell
simple- responds primarily to oriented edges and gratings (bars of particular orientations), tuned to different frequencies and orientations
no center/surround in complex
Hypercolumns
set of columns that are responsive to all lines of all orientations from a particular region in the visual field and viewed by both eyes
ocular dominance columns (LRLR) bringing together alternations creates depth perception
orientation columns (pinwheel like structure)
Quadranopsia
only one quarter of the visual field
Hemianopsia
decreased vision or blindness (anopsia) in half the visual field
Scotoma
a partial loss of vision or a blind spot in an otherwise normal visual field
Binocular Rivalry
phenomenon of visual perception in which perception alternates between different images presented to each eye
Motion selectivity
Direction selectivity
*
PPA
parahippocampal place area (PPA)
encoding and recognition of environmental scenes
inferior temporo-occipital cortex
FFA
Inferior temporal cortex (IT)
codes for faces
Extrastriate cortex
sensitive to motion
loss of visual field: variations
Quadranopsia - 1/4
Hemianopsia - half of visual field
Scotoma - spot
Scientific Reading
for binocular vision,
what neurons are uniquely tied to perception, not merely picking up retinal image
critique of BOLD
logothetis
local field potential (LFP) : summation of post-synaptic potentials
multi-unit activity (MUA) : action potential spikes
found BOLD signals more correlated to LFP
