Chacron lectures 1-5 Flashcards
what brain areas are for motivation?
amygdala and hypothalamus
what is the basal ganglia involved in?
motor action
what brain area is for 3D coordination?
posterior parietal cortex
what is rostral vs caudal
rostral is towards the nose, caudal is towards the back of the brain
what is the brainstem made of?
midbrain, pons, medulla
name the major division of the central nervous system from dorsal to ventral
cerebral cortex
diencephalon
brainstem (midbrain, pons, medulla)
cerebellum (caudal to brainstem)
spinal cord
name the primary brain vesicles from most rostral to caudal.
prosencephalon (forebrain), mesencephalon (midbrain), rhombencephalon (hindbrain)
name the secondary brain vesicles of the forebrain
paired telencephalic vesicles, diencephalon, paired optic vesicles
in what secondary brain vesicle do the thalamus and hypothalamus evolve from?
diencephalon
what secondary brain vesicle do the olfactory bulbs emerge from?
telencephalon (telencephalic vesiles / cerebral hemispheres)
what “holes” are encapsulated in the telencephalon and diencephalon respectively?
lateral ventricles and the third ventricle
name 3 white matter structures found in the developed forebrain
corpus callosum, cortical white matter, internal capsule
what structures are found in the developed mesencephalon?
tectum and the tegmentum that contains the cerebral aqueduct
what is another name for the medulla?
myelecephalon
what is another name for the pons and cerebellum? what primary brain vesicle are they located in?
metencephalon, located in the rhombencephalon
name the structures in the hindbrain
metencephalon (pons and cerebellum), myelencephalon (medulla), encapsulate the fourth ventricle
what are the 3 steps of the neural tube development?
- 3 vesicles
- 5 vesicles
- 3 flexures
what are the 3 flexures of the neural tube? from rostral to caudal
cephalic, pontine, cervical flexure
Name 3 signaling molecules(morphogens).
what do they affect?
Shh (sonic hedgehog), BMP (Bone morphogenic proteins), Wnt (protein family).
They affect transcription factors
where are Wnt signaling vs inhibitors found? what genes do they control?
Wnt inhibitors are more rostral, Wnt signaling are more caudal
They control Otx2 and Gbx2 genes
Where are Otx2 vs Gbx2 genes found?
Otx2 rostrally (forebrain and midbrain), Gbx2 caudally (anterior hindbrain)
what are similarity and differences between a rat vs a human brain?
similarity: same overall structure
differences:
- rats don’t have sulcus or gyrus
- they have bigger olfactory bulbs
- no arc in their cerebral hemispheres
- different brainstem orientation
name the cerebral hemispheres
frontal, parietal, temporal, occipital
what is called the gyrus surrounding the corpus callosum?
cingulate gyrus
name the 3 sulci of the brain
central, lateral, cingulate
what does golgi stain for?
grey matter (cell bodies)
what does Weigert stain for?
white matter (axons)
name the 6 layers of the neocortex
1: molecular layer
2: external granule layer
3: external pyramidal layer
4: internal granule layer
5: internal pyramidal layer
6: multiform layer
what layer is largest in the primary visual cortex? why?
layer IV (4) because it receives input from thalamus
what layer of the PVC do feedback projections to the thalamus come from?
layer VI (6)
in the PVC, what are layer IV inputs and projections?
- monocular inputs from thalamus (dLGN)
- binocular projections to layers III and IVb of the visual cortex
where do layers II, III, and IVb in the PVC project to?
to other layers and areas of the visual cortex
in the PVC, where does layer V project to and what does it control?
project to pons and superior colliculus to control visually guided voluntary movements(subcortical areas)
in the PVC, where does layer VI project to?
it projects BACK to dLGN of the thalamus
what layer is largest in the primary motor cortex?
layer V (5) because it sends output info to subcortical structures including basal ganglia
as a general rule in the neocortex, where do ascending vs descending projections originate from / project to?
- ascending originate in layers II and III and project to layer IV
- descending projection originate in deep layers V, VI and project back to layers I, II, VI
what are chandelier cells?
inhibitory interneurons that terminate on axons of layer II and III pyramidal cells (prevents AP transmission)
what are basket cells?
inhibitory interneurons that terminate on cell bodies (soma) of pyramidal cells (prevents AP firing)
what are neurogliaform cells? what layer do they act in?
inhibitory interneurons that create axosomatic synapses on spiny non-pyramidal neurons of layer IV
describe ascending projection in visual cortex
V1 layer II & III -> V2/V3 layer IV
describe descending projection in visual cortex
V2/V3 layer V, VI -> V1 layers I, II, III
name the 3 main structures in the cerebral cortex
- Basal Ganglia
- Hippocampus
- Amygdala
how are structures in cerebral cortex (ex BG, hippocampus, amygdala) organized?
in nuclei instead of in layers
describe fast-spiking vs regular spiking neurons. give example for each.
fast spiking = short AP, high discharge rate (putative interneurons)
regular spiking = large AP (pyramidal neurons)
where do skin sensory receptor neurons relay information to?
to the dorsal column via the dorsal horn
where does the thalamus project to?
primary sensory cortical areas
name 3 thalamus nuclei and the system they are involved in?
lateral geniculate nucleus (visual)
medial geniculate nucleus (auditory)
ventral posterior lateral (vestibular)
name a thalamic subnuclei involved in motor control
ventrolateral nuclei
what do thalamic 2nd order sensory areas do?
change how primary nuclei respond to peripheral info (ex pulvinar nuclei)
how do peripheral vs central sensory neurons respond to stimulus?
peripheral: respond to most stimuli differently (dense code)
central: respond to specific stimuli (sparse code)
describe dense vs sparse code
Dense: all the neurons respond differentially
Sparse: only a small fraction of neurons respond respond to any given stimulus (metabolically more efficient)
what does information processing depend a LOT on?
context! and internal brain state
projection neurons respond to most stimuli, but is it in a random way?
not random, they all respond in different ways
what kind of activity can projection/peripheral neurons (like PN1 neurons in the example) show?
spontaneous activity
what is special about olfactory sensory pathway?
it goes straight from the olfactory bulb neurons to the anterior piriform cortex; doesn’t go through the thalamus
how do neurons in mouse anterior piriform cortex APC fire?
sparse coding: they fire to specific cells only (look at slide 12)
definition of feature invariance. explain
Neural representations become invariant to identity preserving transformations of behaviorally relevant stimulus features (neurons respond to object no matter the size, position, color)
give an example of how neurons can have selectivity (as opposed to invariance). what coding do they use?where can we find selective neurons?
they will only respond to a specific model of car of a specific color. they apply the “AND” operation. they are sparse coding.
- found in V4
what is the mcgurk effect?
auditory-visual illusion that illustrates how perceivers merge information for speech sounds across the senses (how brain integrates different stimuli)
the McGurk effect is the perfect example of what brain area working?
Multimodal cortex putting together multimodal information
where do the thalamus subnuclei project to?
to different unimodal (primary) cortex areas for each sense
explain the general sequence of cortical processing for the somatosensory system after the thalamus
- primary somatosensory (unimodal) cortex
- unimodal association cortices
- multimodal association cortices
simply describe the pathway for voluntary motor control?
corticospinal pathway: layer 5 (V) motor cortex neurons synapse on interneurons in the VENTRAL horn of the spinal cord. hose neurons cross the spinal cord at the medulla-spinal cordjunction
what other brain areas other than motor cortex send descending information for voluntary movement? (6)
thalamus, midbrain, red nucleus, pons, cerebellum, amygdala
what brain areas are involved in ascending pathways of voluntary control?
cerebellum, deep cerebellar nuclei, red nucleus, midbrain, thalamus ventrolateral nucleus, basal ganglia,
where is the extrapersonal space map located in the brain?
posterior parietal cortex
what is caused by lesions in posterior parietal cortex (extrapersonal map) (4)
visual neglect, personal neglect in reference to body, representational neglect, optic ataxia
what is optic ataxia?
difficulties reaching/grabbing objects in extrapersonal space
what regions did they identify to be involved in planning and control of voluntary movement via single unit (neurophysiological) recording?
parietal cortex regions MIP, VIP, LIP, DP (SPATIAL INFORMATION PROCESSING)
describe dorsal vs ventral stream
dorsal /parietal stream: for spatial information (where); projects to frontal association areas
ventral/temporal stream: for emotional significance (what); projects to ventral frontal cortex
- both go from back to front
what are frontal association areas involved in?
controlling motor functions that require spatial information
what are ventral regions of frontal cortex involved in?
identifying and assigning emotional significance to objects
what is object centered visual neglect?
only the side of the object opposit to the side of the lesion is neglected
someone with a unilateral lesion to the right posterior parietal cortex will be able to draw which side of an image properly?
he can draw the right side
visual neglect for objects due to a lesion is linked to the dorsal or ventral visual pathway?
dorsal visual pathway
what did damage to the right posterior parietal cortex cause related to landmarks?
patient could only recall landmarks to their right (not the landmarks on the opposite side of lesion)
what is personal neglect caused by right posterior parietal cortex lesions?
patient can only draw a self portrait of the right side of their face (can’t draw the side opposite to lesion)
more specifically what region of the parietal cortex is affect in people with optic ataxia?
posterior (in ex, it was dorsomedial) parietal cortex, where extrapersonal space is represented
what did lesions of parietal cortex in monkeys cause?
spatial motor and spatial perceptual deficits comparable to those in human, and difficulty directing eye movements towards objects in opposite hemispace
what are VIP, MIP, LIP, AIP regions of parietal cortex involved in?
transforming sensory inputs to motor outputs
single unit recordings of LIP neuron showed what?
Retinal Centered Coding of Visual Target, but attention specific
what is declarative/explicit memory? what brain areas are involved?
facts/events
hippocampus-medial, temporal lobe, diencephalon
what are the 4 types of nondeclarative/implicit memory? what brains areas are involved?
- skills/habits: Striatum (BG), motorcortex, cerebellum
- priming: neocortex
- basic associative learning: emotional response (amygdala) and skeletal musculature (cerebellum)
- nonassociative learning: reflex pathways
what is associative vs non-associative learning?
basic associative learning:
- emotional response: amygdala
- skeletal musculature: cerebellum
non-associative learning: reflex pathways
what surrounds the hippocampus?
perirhinal cortex, entorhinal cortex, parahippocampal cortex
what are the regions of the hippocampus and what links them? what cell types do they have?
dentate gyrus (granule cells) - mossy fiber connections -> Ca3 (pyramidal) - Schaffer collaterals -> CA1 (pyramidal) -> subiculum
what do lesions of the right vs left hippocampus affect?
right = spatial memory
left = words, objects people
what is special about taxi driver’s brain?
they have a bigger posterior hippocampus and a smaller anterior hippocampus than average
what process in the hippocampus is thought to underly the formation of new memories?
neurogenesis
what 3 things are necessary for spatial learning
internal compass, external landmarks, neural representation of our environment
how did different hippocampal lesions affect rat’s memory of where the platform is in a water maze? (similar to humans)
CA3 lesion decreases the spatial accuracy (could still find platform but took longer)
complete hippo lesion: no spatial accuracy (can’t find platform)
what different about rodent’s hippocampus?
it is banana shaped lol
how is labeled line code applied to CA1 pyramidal cells?
their firing is location dependent
do CA1 place field neurons have directional selectivity?
no
did they find topographic organization in place field neurons?
no: no relationship between CA1 neurons proximity and their place field position
why is it important for place fields to be stable over time?
important for memory retention of an environment
what feature of Ca1 pyramidal cell ensures coding of place or location?
omnidirectionality (allowscoding of place/location independently of head direction)
what were the results from the experiment of rotating rat’s environment with vs without the animal’s knowledge?
- rotation of place field did occur when the animal was not aware of the rotation
- rotation of place field did NOT occur when the animal WAS aware or the rotation
what did they conclude from the rotation rat’s environment experience?
place fields are determined by EXTERNAL landmarks when they don’t contradict the internal cues.
When there is contradiction, internal cues dominate.
does remapping of place field happen when the environment is “translated”
no
does isotropic scaling change of environment cause place field remapping?
no; place fields are largely insensitive
Are place fields sensitive to novelties in the environment?
yes but only when the novelty or removal happens inside the place field
can you predict the effect of changing a complex environment (moving distal and proximal cues) on place fields? what happens to the place fields?
no;
some place fields follow distal cues
some place field follow proximal cues
some place fields completely remapped
what happened to the place field of a rat’s neurons after a few laps in a unidimensional environment?
the place field becomes wider in the direction that the rat is coming from
what explains the widening of the place field in rats doing unidimensional laps?
because the neurons receive stronger synaptic input which strengthen the synaptic connection as the rat gets used to the environment
what did they use in epilepsy patients to locate the seizure focus?
single neuron recordings and intracranial electrodes
what did they find in epileptic patients who played the taxi driver game?
place sensitive neurons
name 3 characteristics of the place sensitive neurons found in humans
- they cover most of the environment
- they are not directionally selective
- there are fewer than in rats
place cells make up what % of the hippocampus in humans vs rats?
24% in humans vs 80% in rats
what is the caveat of testing place cells in humans that make the results less accurate?
the patient were immobile and used virtual reality
what type of cells for location were found in non-human primates?
GAZE cells in hippocampus with a 3D place field
what is a limitation of using rodents compared to humans?
they use olfaction so much more than vision
what is Hebb’s postulate?
cells that fire together, wire together
what underlies associative (Hebbian) plasticity?
correlation between pre- and post- synaptic activity
what is the protocol for inducing plasticity that they used?
stimulating a Schaffer collateral with tetanus of specific frequencies
what Hz of tetanus induces LTD vs LTP?
1 Hz induces LTD,
50 Hz induces LTP
what happens to post-synaptic neurons receiving 10 Hz tetanus?
EPSP goes back to normal
what ion usually blocks NMDA receptors at resting membrane potential?
Mg2+
how can MG2+ be removed to stop blocking NMDA receptors?
by strong postsynaptic depolarization causing GLUTAMATE to bind NMDAr
what happens when Mg2+ stops blocking NMDAr?
Na+ and Ca2+ enter the post-synaptic cell, and K+ exits the cell via NMDA
what kind of receptors and ions can cause associative plasticity?
NMDA receptors and calcium ions
at what levels of NMDA and Ca2+ do we see LTD or LTP?
- low/moderate NMDA activation and Ca2+ flow = LTD
- high NMDA activation and Ca2+ flow = LTP
why are LTD and LTP opposing mechanisms?
one makes the synapse stronger, the other makes the synapse weaker
What is APV?
substance that blocks NMDAr
what is EGTA?
a calcium chelator (calcium buffer)
what happens to LTP when they give moderate vs high APV to neurons?
moderate APV changes LTP to LTD.
high APV completely cancels the effect of the tetanus.
the effect of APV on LTP show that it affects NMDArs in what way?
APV deactivate NMDAr which usually contribute to LTP
what happens to LTP when they give moderate vs high EGTA to neurons?
moderate EGTA: LTP -> LTD
high EGTA: no effects of tetanus
what does the effect of EGTA on LTP show?
calcium is required for LTP
the APV and EGTA experiment show what?
plasticity required calcium entry via NMDAr
why does moderate CA2+ cause LTD
moderate CA2+ in synaptic cleft moderately activates NMDAr and interact with protein phosphatases in the post-syaptic cell that have high affinity for calcium
how does high Ca2+ cause LTP?
high Ca2+ strongly activates NMDAr and saturates protein phosphatases. It interacts with Protein kinase C and calmodulin kinase II, ausing LTP
remember _____ tetanus freq causes LTP, ____ tetanus freq causes LTD
high
low
what characteristic of protein phosphatase causes LTD?
high affinity to Ca2+ (binds Ca2+ at low conc)
what happens to rat in the water maze who were given APV?
they couldn’t remember where the platform was (no more spatial memory)
what are AMPA receptors permeable to?
NA+ & K-
KO of LTP causes what?
no retention of place fields (but they can still form place fields)
explain STDP spike timing dependent plasticity
- if pre-synaptic cell fire before post = strengthening of the synapse
- if post- before pre- = weakening of the synapse
STDP can predict the _______ of place fields
shifting (?)
intracellular recordings from mammalian
hippocampus showed similar properties what kind of neurons?
motorneurons
in what kind of animals is implicit memory most easily studied? why?
invertebrates; it requires simple behavior, well understood anatomy
what is special characteristic about aplysia californica?
Gill withdrawal reflex
what is aplysia californica?
slow moving gastropod mollusk
how many neurons in aplysia vs average person?
~20000 in aplysia,
~10^11 neurons in humans
aplysia can habituate to what kind of stimulus?
to harmless repeated stimuli (siphon touch)
what stimulus causes dishabituation to siphon touch?
harmful stimuli (tail shock)
name the 5 ganglions found in Aplysia
buccal, cerebral, pleural, pedal, abdominal
aplysia neurons are big. what does this allow?
to identify the same individual pyramidal cells in different aplysia
explain the simplified anatomy of aplysia nervous system
sensory neuron LE -> excitatory / inhibitory interneurons -> L7 motor neuron in gill
what causes the SHORT TERM habituation (decrease post-synaptic response in motor neurons to siphon touch)
the decrease of releasable pool of vesicles at that active zone
what causes the LONG TERM habituation?
decreased number of synaptic connections
what happens to sensory vs motor neuron EPSPs during habituation?
sensory neuron EPSP stay the same;
motor neuron EPSP disappears
what kind of interneuron is involved in in the facilitation of the gill withdrawal by tail shock?
modulatory interneuron
where does the modulatory interneuron from the tail synapse?
it synapses on PRESYNAPTIC TERMINAL of regular interneuron and of gill motor neuron
how can short vs long term SENSITIZATION be achieved?
more tail shocks = longer sensitization (the longer aplysia responds to siphon touch)
- few tail shocks = short-term
- many tail shocks = long term
what mechanism mediated by what neurotransmitter governs sensitization in aplysia?
synaptic facilitation mediated by serotonin 5HT
what neuron releases serotonin? onto what neuron?
the faciliatory interneuron releases serotonin on the presynaptic terminal of the sensory neuron
explain the cascade of event in a synapse for short-term facilitation by serotonin
serotonin in released from interneuron -> binds serotonin R -> G-protein bind adenylyl cyclase -> cAMP -> PKA
2 options:
1. PKA catalytic subunits close K+ channel, open Na2+ channel to increase depolarization
2. PKA regulatory subunits
BOTH work to increase glutamate release onto the motor neuron
how does long term facilitation work in aplysia?
the signal from the facilitatory interneuron goes to the nucleus of the sensory neuron where Ub hydrolase causes formation of new vesicles and new synaptic connection
when does long term facilitation happens?
when LTP is maintained for a long time
name the 3 basics that are common to aplysia and humans?
- plasticity requires calcium
- cell signaling i modulated by neuromodulator (serotonin vs dopamine)
- long term plasticity requires signaling to the nucleus
plasticity in what region of the hippocampus requires NMDAR and Ca2+?
in CA1
what are the pre and post-synaptic mechanisms of plasticity that are similar across species
- Pre: increase/decrease in vesicle pool
- Post: insertion/deletion of AMPAR, number of synaptic boutons
Exposure to what? early in development is critical for vocal learning
vocalizations
does language develop spontaneously?
yes!
what is a spectrograph?
graph of time varying frequency spectrum. we can see human speech with it
what are the 3 phrases of a songbird song?
whistle, trill, buzz
how long is songbird’s listening and practice phase (before crystallization)?
90 days
what are the 3 phases of song learning?
listening, practice, crystallization
in humans and songbirds, what does a loss of feedback cause?
gradual deterioration of speech
do birds have accents?
yes they have region specific song motifs
in songbirds, what is required for the normal song?
social interaction and auditory feedback
during the first 10 months of life, what kind of speech do humans produced?
universal speech, no matter the language
during the first 8 months of life, what kind of speech do humans percieve?
universal speech
birds are born with ______-_________ predispositions
species-specific
isolated WCS can sing spontaneously, but their song is ____ ________
not attractive
how is song learning “creative”?
if a bird is tutored 2 different songs model, it will mix both to create its own song
what happens if a WCS is thought the song backwards? (inversed syllable order)
WCS can sing the sequence backwards
explain the 3 steps of the error-driven model for learning and maintaining song
- storage of a model/template (syllable and sequence) of the song
- bird sings and tries to reproduce
- song feedback/comparison
name the 3 brain areas involved in song production
HVC -> RA -> nXIIts
what is bird’s vocal organ?
Syrinx
name the 3 brain areas involved in song production?
LMAN, Area X, DLM
what are the effects of area x lesions in juveniles vs in adults?
juvenile = disrupt song learning
adults = no effect
what brain areas were paired in the LTP experiment in songbirds
HVC + LMAN -> Area X
what does it mean that the plasticity in the LTP experiment is synapse specific and activity dependent?
giving tetanus to LMAN axon will potentiate the LMAN -> AreaX synpase, but not the HVC -> AreaX synapse
how did the prof’s experiment indicate that LTP induction at these synapses may be described by the Hebbian rule (cells that fire together, wire together)
High-frequency tetanus alone or depolarization alone failed to induce LTP; LTP requires both pre- and postsynaptic activity
what can we conclude if LTP induction after pairing in area X is blocked by APV and BAPTA?
Similar to the classic LTP in hippocampus, the LTP induction in area X is dependent on Ca2+ and NMDAr
is the % change of EPSC high in adult or juvenile birds? why?
higher in juvenile birds because they have more LTP because they are song learning
what is the definition of sensory reafference?
how to distinguish self-generated vs external sensory input
what is a reafferent stimulus?
stimulus from your brain
what is an exafferent stimulus?
externally generated stimulus
how do we distinguish exafferance vs reafference stimulus?
the system compares the actual afference to the copy element
movements can lead to what type of stimulus?
sensory reafference
what 2 stimulus are combined to give rise to a perceived stimulus?
efference copy + reafferent stimulus
in the mechanical tickling experiment, what was the motor command, the reafference stimulus, and the perceived stimulus?
motor command = arm movement
reafference stimulus = tactile stimulus
perceived stimulus = tickling sensation
what is the sensory discrepancy in the mechanical tickling experiment?
feeling caused by time delay between the efference copy and the actual sensory feedback
what is the efference copy
predicted sensory feedback
what is caused by a sensory discrepancy?
tickle
what kind of information does the efference copy contain?
temporal and spatial information about the reafferent stimulus
what did they train the bunny to do with the tone and air puff?
to start closing its eyes when it hears the tone, that always played before the air puff
what happens to bunny with cerebellar lesion?
it can only blinks when air puff, not during the tone
(it forgets the association of air puff and tone)
what is the cerebellum involved in?
balance, coordinating movement, timing of movement, timing of discontinuous movements, motor learning
what is the most anatomically conserved structures throughout evolution?
cerebellum
name the cerebellar layers from outer to inner and what is in them
- molecular layer: parallel fibers
- purkinje cell layer: purinje cells
- granule cell layer: granule cell, climbing fibers, mossy fibers
- white matter
what happens if you co-activate parallel fibers and climbing fibers at the same time in the cerebellum?
LTD
against what theory does the co-activation of parallel and climbing fibers causing LTD goes? why?
hebb’s postulate!
Hebb’s postulate says that this should give LTP, but in the cerebellum it gives LTD
what happens to a patient wearing prism lenses that has impaired adaptation capacities? (inferior olive hypertrophy)
they can not get used to wearing the lenses and will keep throwing off target
does sensorimotor coordination and adaptation to novel conditions required cerebellar function?
- Sensorimotor coordination does not require the cerebellum.
- Adaptation to novel conditions does require cerebellar function
what kind of process is adaptation?
error driven process
cerebellar LTD help achieve what?
cancellation of expected stimuli
what is the weakly electric fish?
Electric fish that emits electric field through an electric organ in their tail
what is special about the cerebellum of electric fish?
it is very developed (but has the same similar anatomy conserved across vertebrates)
how do electric fish interact with their environment?
use perturbations of their self-generated electric field (electric organ discharge)
what are electric fish;s reafferent stimulus with their EOD?
activation of their own electrosensory system via their EOD
what are electric fish’s cerebellar layers?
granule layer, molecular layer, principal cell layer, sensory input layer
what happens to a cerebellar neuron of electric fish when there is only the EOD?
it fires normally (moderate)
what happens to a cerebellar neuron of electric fish when it is paired with an excitatory stimulus?
neuron fires a lot in response to the increase sensory input
what happens to a cerebellar neuron of electric fish once you stop the excitatory stimulus?
activity goes does lower than before
what happens to a cerebellar neuron of electric fish when the EOD is paired with an inhibitory stimulus?
opposite than excitatory stimulus
do changes in the reafferent stimulus cause changes in the efference copy?
yes
what underlies the adaptive cancellation of reafferent input?
anti-hebbian STDP
what is anti-hebian STDP?
pre-synaptic EPSP followed by post-synaptic EPSP causes depression instead of activation
where is anti-hebbian STDP found (what cells) vs hebbian STDP?
anti-hebbian = cerebellum (granule cell -< parallel fiber)
hebbian STDP = hippocampus
maybe go over the last part of lecture with the graphs
