Behavioral Neuro Test 2 Flashcards
neuroscience approach behaviour methods
- stereotaxis surgery
- invasive electrophysiology
- immediate early gene (IEG) expression and tract tracing
stereotaxis surgery methods (3)
permanent lesions, electrode impanted in rat brain. and cannulation
bregma and lambda
bregma is an area on top of brain used as reference pooint. it is area on top of skull where two sutres (seams of in skull) intersect. lambda is another one of those reference points
stereotaxtic atlas
map of where a landmark is in brain.
IEG expression and tract tracing (3 types)
- double labelling
- optogenetics
- DREADDS
behavioural approach in methods for neuro
- open field test
- elevated plus maze
- radial arm maze
- morris water maze
- conditioned defensive burying
- conditioned taste aversion
intracellular unit recording
intracellular microelectrode records the membrane potential from a single neuron
extracellular unit recording
tip of microelectrode is in extracellular fluid next to neuron. records electrical disturbance each time a single neuron fires an action potential
multiple unit recording
electrode is larger than microelectrode- so it records the action potential of many nearby neurons; these are summed together
invasive EEG recording
a large implanted elctrode reocrds general changes in electrical brain activity; not specific to action potentials
in FG example, what were CS and US?
conditioned stumulus= light
unconditioned stimulus= food
why do we want to wait when using IEG expression and double labelling
wait 90 minutes because the protein (fos) takes about 90 minutes to be expressed
double labelled cells
cells that label for BOTH fg and fas
why do double labelled cells mater?
they are activated by a behavioural event and anatomically project from one brain region of interest to another.
this allows us to find behaviral functions of anatomical projections
fos vs fg
FG is a retrograde tracer and fos is a natural protein, IEG expression. Fos is present when neurons were fired/active.
direct method of labelling
flouresence
indirect method to label
antibodies. this is often the preferred method because there is more amplication
goat and rabbit antibody example (this is indirect method)
- an antigen is injected into a rabbit.
- the rabbit produces an antibody
- that antibody from the rabbit is injected into a goat
- the goat produces that antibody as well
optogenetics defintion
manipulating neural activity with light. this is done by using light sensitive algae and inserting it into the brain. light can depolarize or hyperpolarize channels.
opsin
a highly light sensitive ion channel. how? put genetic code to making opsin into a virus. virus is modified to tell cells to produce opsin. infuse virus into brain
2 types of opsin
channelrholdopsin and halorhodopsin
channelrholdopsin
opsin type- blue light depolarizes neuron because Na+ enters the cell. blue light causes Na+ to enter the cell
halorhodopsin
stimulated by yellow light. yellow light opens Cl- channels and hyperpolarizes cells
DREADDS
- **Engineered Receptors: **DREADDs are specially designed G protein-coupled receptors (GPCRs). Unlike natural receptors, DREADDs don’t respond to their usual, or endogenous, signaling molecules. For instance, if a DREADD receptor is derived from a receptor for acetylcholine (ACh), it will not be activated by ACh. These are specially engineered proteins that scientists put into certain brain cells.
- Designer Drug Activation: Scientists create a special drug that only activates these designer receptors. DREADDs are activated only by a unique synthetic drug, or designer drug, that’s created specifically for this purpose. This drug doesn’t interact with any other receptors in the body, so it won’t interfere with other brain or bodily functions.
- **Precise Control: **Because this synthetic drug only activates the engineered DREADD receptors, scientists can precisely control the activity of targeted neurons. This enables very specific manipulation of brain signaling without affecting other cells.
- Purpose: By turning specific brain cells on or off, researchers can study what those cells do, which helps in understanding behaviors, emotions, and even brain disorders. DREADDs are valuable in neuroscience research, helping to create precise effects without affecting the whole brain.
optogenetics and DREADDS similarites
both use viral vectors (a modified virus that delivers genetic material into cells) to get proteins expressed in cell membrane of neurons
optogenetics proteins
opsins
DREADS proteins
they make up the designer G=protein coupled receptor
neuro activation or inactivation is control by what (in optogenetics vs DREADDS)
optogenetics- light
DREADS- chemicals/drugs
pros of optogenetics
- can modify neural activity (in ms)
- can time back neuronal exeitation or inhibition to a specific behaviour
cons of optogenetics
- animal has fiber optic cable coming out of head
- limit movement + cause confounders (although you can use control groups to help w this)
pros of DREADDS
- designer drug can be administered peripherally (less invasive)
Pro and con (depending how you look at it) of DREADDS
- stimulate of inhibit neural activity in longer lasting fashion (minutes or hours) – this can be a pro when behaviour task involved ongoing behavior
anxiolytic drug
anxiety reducing drug
Case of Genie
- she was 13 and weighed around 60lbs and couldn’t chew food.
- she had been beaten, starved, etc. since being 20 months old.
- she never truly returned to normal even after special care. she couldn’t chew and had language issues.
why do we want to learn case studies(feral children)
to learn development. things that can result from these studies:
* motor behaviour issues, can’t chew, easily terrified
* inappropriate reactions (i.e silent tantrums)
postnatal brain growth is a result of…
- synaptogenesis
- myelination
- increased dendritic branching
- overproduction of synapses (could be a reason for more plasticity in young brains)
- normal regressive changes
synaptogenesis(+ when and where)
the process of forming connections(synapses) between neurons in the nervous system
* primary visual and auditory corticies- synaptogenesis spurt at 4 months of age. maximum density is at 7-8 months and then it decreases
* profrontal cortex- sunaptogenesis proceeds at relatively steady rate. maximum density occurs at 2 years
myelination (development)
the process where nerve fibers in the central and peripheral nervous system are wrapped in a protective layer called the myelin sheath
* starts in sensory areas (first few months of life) and then motor areas
* myelination of prefrontal cortex continues into young adulthood.
increased dendritic branching
dendritic branching in cortex progresses from deeper to more superficial layers
The more branching a dendrite has, the more connections it can form, allowing for richer and more complex neural networks.
Dendrites branch from deep to superficial to increase their surface area, which allows them to receive inputs from thousands of other cells or the environment.
normal regressive changes in brain development
- synaptic density scales back after maximum is reached
- cortical thinning of gray matter
- dendritic pruning
critical or sensitive learning periods
time period when sensitive to inputes leading to development changes
conrad lorenz + study thing with ducks
- human ‘mother’ to duckings
- developmental recognition of caretaker
- CRITIAL period
critical period
essential for experiences to occur in this window to impact development
sensitive period
experience can have large impact in development on this time period. outside, it can still have weak effects
johnson and newport (1989)
- subjects- 46 native chinese or korean learners of english (in US for at least 3 years). Had different arrival times
- method: grammatical judgement test
- results: accuracy correlated with age for anyone who arrived to US before puberty. those who arrived after puberty was not correlated with accuracy
language development: infants (4 months)
can distinguish all human speech phonemes
language development: 6 months
show preference for native language phonemes
language development: 1 year
no longer respond to phnemes of non-native language
language development: 4-6 years
decline in professiency can occur
language development: 10 years
can learn to speak native language without an accent
visual development critical period- where is V1 primary
- V1 primary visual cortex located in the occipital lobe
visual development critical period- occular dominance collumns
eye preference. like right handed but for eye. activated more by input from one eye or the other
experiment for occular dominance collumns
researchers might temporarily close one eye during an animal’s early development and then observe changes in V1 neurons
Procedure: By sewing one eye shut (or using a temporary blindfold) during a critical period in early life, researchers limit input to the visual cortex from that eye.
Effect on Neurons: Without input from the closed eye, the visual cortex’s response to that eye’s signals weakens over time. Meanwhile, neurons in V1 that receive input from the open eye become more active and start to take over. This happens because the brain cells from the open eye essentially “compete” for space and become stronger in response to the increased activity.
Competitive Reorganization: Over time, the columns in V1 change. The columns related to the open eye grow wider and more robust, while those for the closed eye shrink. This restructuring reorganizes the system, increasing dominance of the open eye in the brain’s visual processing.
monocular deprivation
The practice of covering one eye, which can cause a shift in ocular dominance.
neurons and synapses not activated by experience
they usually do not survive. use it or lose it
humans are uniquely slow in neurodevelopment. why?
allows more time for fine-tuning
early visual deprivation
- When visual input is reduced during critical developmental stages, neurons in V1 form fewer synapses and dendritic spines (the tiny protrusions on dendrites where synapses are formed). With less stimulation, the brain doesn’t develop the usual rich network of connections necessary for processing complex visual information.
- deficits in depth and pattern visions as adults
enriched environment for early visual experience
- thicker cortexes
- greater dendritic development; more dendritic spines
- more synapses per neuron
effect of experience on topographic sensory cortex maps
- Cross-Modal Rewiring: In these experiments, scientists rerouted visual input to the auditory cortex in young animals, such as baby ferrets. This means that instead of only hearing, the auditory cortex received signals that would normally go to the visual cortex.
- Auditory Cortex “Sees”: Remarkably, the rewired auditory cortex adapted to process these visual signals, essentially “seeing” through sound-processing areas. The cortex reorganized itself to respond to visual information, demonstrating that sensory areas aren’t rigidly fixed for one type of input but can adapt based on early experiences.
- **Critical Period: **This plasticity works best in early development, when the brain is especially adaptable. During this time, sensory cortices can reorganize themselves in response to new types of input, showing just how flexible the brain can be in its wiring.