Lec 1/ TB Ch 1, 2 Flashcards
1
Q
- Reticulum theory
- Cajal
- silver nitrate method
- 4 main discoveries
- Brainbow method
- The Brain Observatory
- # neurons in brain
- # neurons in cerebral cortex
A
- Reticulum theory: all brain cells are fused together to form a big net or reticulum; this unit works in a holistic way
- Cajal:
- silver nitrate method: stain and drew what he saw from the microscope
- Camillo Golgi invented the silver nitrate method
- silver nitrate method: stain and drew what he saw from the microscope
- Santiago Cajal made 4 main discoveries
- Neurons only connect in a specific place called synapse
- Neurons are connected in principled (based on a set of rules), not randomly
- Electrical signals travel through neurons in only 1 direction; this allows systematic info flow thru circuits
- (#4) neurons are independent units that are not joint together
- Golgi supports the reticulum theory; against Cajal’s
- Brainbow method: derived florescent proteins from glowing jellyfish to label specific neurons
- It has 150+ colors
- Cons: the color labelling is random
- Current rs: try to tag different types of neurons w/ diff ranges of colors
- Ex. red + orange for neuron type 1
- Ex. Yellow + green for neuron type 2
- Ex. Blue + purple for neuron type 3
- Researchers attempt to disseminate results to broad audience
- The Brain Observatory/ The brain’s Hubble telescope
- Constructed the “Concise Digital Atlas of the Human Brain”
- Ppl can inspect stained sections of the brain at various magnifications (ex. birds eye view of all structures, individual neurons)
- The Brain Observatory/ The brain’s Hubble telescope
- Brains has 100 billion neurons, can stretch for 150,000 km
- Cerebral cortex: 30 billion neurons, 1 million billion connections
2
Q
- LABEL THE DIAGRAM
- Neuron fx
- what are the fx of the following parts?
- dendrites
- axon
- myeline sheath
- nodes of ranvier
- terminal buttons
- synapse
- Size of neuron in the retina?
- Length of neuron spinal cord to toes?
- 6 shapes of neurons
- von Economo neurons
- 2 places it is found
- 7 fxs
- Who has impaired von Economo neurons?
- What animals have von Economo neurons?
A
Anatomy
- Neurons’ function: signal transmission
- Nucleus: Central region
- Neurons look like trees: branching roots, long trunk, bushy crown
- Dendrites: (tree in Greek) Branching roots, receive signals
- Axon: (axle in Greek) long trunk, transmit signals
- Myelin sheath: fat that give insulation to protect and accelerate signals
- 1 mm long
- Nodes of Ranvier: small spaces that separate the Myelin Sheath, rejuvenate (restore energy) the signals
- Terminal buttons: the axon splits into segments, and it ends with the buttons, the buttons relay info to downstream neurons
- Synapses: (syn = together; haptein = to clasp) tiny clefts b/w terminal buttons of message sending neurons and dendrites of message receiving neurons
- Neurons vary in size and shape
- Size: Neurons in the middle layer of the retina: 1 mm
- Neurons that extend from spinal cord to toes: 1 m
- Shapes: pyramidal, granular, stellate, chandelier, basket, fork
- Size: Neurons in the middle layer of the retina: 1 mm
- Some neurons are specialized for certain sensory or motor processing
- Ex. von Economo neurons – found in a few brain regions (anterior cingulate, anterior insula); related to emotional processing, self-awareness, and social cog, interoception (can sense one’s internal bodily’s state), affect and communication in relationships
- Those w/ mental disorders that impair mental capacities (ex. autism and schizo) have altered von Economo neurons
- Socially complex mammals have many von Economo neurons (apes, elephants, whales, dolphins)
3
Q
- LABEL THE DIAGRAM
- Process of how e- signals are conducted (3 steps)
- Active conduction
A
Physiology
- Dendrites receives many inputs (in the form of e current) from other neurons
- E current moves to the cell body via passive conduction
* Passive conduction: passive flow for e current from dendrite to cell body
- E current moves to the cell body via passive conduction
- Current reaches the base (aka hillock of Axon hillock); if the total sum of the current exceeds the specific threshold, the neuron fires an action potential via active conduction
* Action potential: aka spike, the neuron experience change in electrical property, this causes the net charge in the axon shift from -ve to +ve
* Active conduction: reoccurring APs/spikes at the nodes of Ranvier, this allows the signal to travel along the axon w/o fading
- Current reaches the base (aka hillock of Axon hillock); if the total sum of the current exceeds the specific threshold, the neuron fires an action potential via active conduction
4
Q
Physiology cont
- LABEL THE DIAGRAM
- RMP?
- Critical Threshold?
- Process of AP: 3 steps
- Fx of hyperpolarization
- Signal speed of myelinated vs unmyelinated neuron
- Fx of Nodes of Ranvier
- Active conduction
- Process to send signal across synapse
- Summation effect
- % of oxygenated blood used by brain
- Size of arteries, arterioles, capillaries
A
- By default, the neuron is more -ve in the inside (RMP: -70 mV)
- When the input is +ve enough to increase the MP to -50 mV (aka critical threshold), this triggers an AP (happens in 1 ms)
- Na+ channels open; Na+ enters cell; cell depolarizes, the cell becomes more +ve than the external env
- Na+ channels close; K+ channels open (slowly K = couch potato); K+ leaves the cell; the cell becomes more -ve
- Since K+ channels close very slowly, the cell becomes hyperpolarized
* Hyperpolarization: prevents another AP happen right away; ensures the signal travels forward, not backwards
- Since K+ channels close very slowly, the cell becomes hyperpolarized
- Myelin Sheath: increase the speed an axon can transmit current
- Unmyelinated: signal travels 1 m/s
- Myelinated: signal travels 10 to 100 m/s
- Nodes of Ranvier: small spaces b/w myeline sheaths; renews the AP perpetually
- Active conduction: the cycle of Na+ influx and K+ outflow happens in each node; active conductions is the sequential (entire chain of) signal rejuvenation
- Process to send signal across synapse
- When signals reach the terminal buttons, the have to cross the synaptic cleft (20 nm)
- Here, NT are released, and bind to specific receptors on the postsynaptic neuron
* NT: chemicals that carry the signals across the synaptic cleft
* If the presynaptic neuron is excitatory, the released NT make the postsynaptic neuron fire
* If presynaptic neuron is inhibitory, the released NT make the postsynaptic neuron less likely to fire
- Here, NT are released, and bind to specific receptors on the postsynaptic neuron
- Whether the target cell fires depend on the sum of numerous inputs
- NOTE: the strength of individual inhibitory or excitatory connection is adjustable
- Neuron activity uses a lot of energy
- The human brain is 2-3% of the total body weight, but uses 20% of the oxygenated blood from the heart
- Oxygenated blood from heart enters blood vessel network: arteries (5 millimetre) -> arterioles (30 micrometres) -> capillaries (10 micrometres; a bit wider than 1 RBC)
- Capillaries
- Have thin walls, oxygen can pass be extracted here
- Veins: deoxygenated blood flows from brain to heart
5
Q
- What does neuron’s firing frequency indicate?
- Why?
- Why are assemblies of neurons arranged in multi-layered hierarchies?
- Visual system
- 2 main stages of processing
- Describe Table detection network
- How can Hierarchical coding networks be bottom-up feedforward?
- How can Hierarchical coding networks have top-down feedback connections?
A
Representation
- IOW, the neuron’s firing frequency indicates whether the preferred stimulus present
- Neurons are tuned to respond to specific stimulus
- Assemblies of neurons are put in multi-layered hierarchies; this arrangement help them capture complex patterns of info
- Ex. Visual system - Object recognition
- There are several stages of processing
- Early stages: process elementary features of shape
- Other stages: process more complex combination of the features
- There are several stages of processing
- Ex. Visual system - Object recognition
- Ex. Table detection network
- Level 1 (bottom): 1 cell code for “vertical edge”; 1 cell code for “horizontal edge”
- Level 2: 1 cell code for length; 1 cell code for “corner”, and this cell receives input from the two cells in lv 1
- Level 3: 1 cell code for legs; 1 cell code for rectangular surface, and it receives input (i.e. corners and lengths) from cells at lv 2
- IOW, the cell can combine feature of corners and lengths to form the more complex “rectangular surface”
- Level 4: 1 cell receives input from two cells in lv 3
- IOW: this cell combines features of rectangular surface and legs to derive the final object representation – table
- The table detection network resembles the hierarchical coding in the cerebral cortex, and other perceptual systems
- Hierarchical coding networks are seen in bottom-up feedforward (use current feedback, and generate solutions for the future) connections
- As a result, sensory signals can be matched w/ knowledge stored in LTM
- Hierarchical coding networks are also seen in top-down feedback connections
- This allows our internal priorities and predictions to guide our perceptual processes
- Top-down connections go from central to peripheral brain regions
- This allows us to reconstruct specific sensorimotor representations w/o external input
- Ex. in our dreams, we conjure (bring forth) diff sights, sounds, and smells in our imagination
6
Q
- LABEL THE DIAGRAM
- Planes
- Sagittal
- Coronal
- Horizontal
- Location of regions
- Rostral (aka ?)
- Caudal (aka ?)
- Dorsal (aka?)
- Ventral (aka ?)
- Lateral
- Medial
A
Navigating the Neural Landscape
- Planes
- Sagittal: section that separates left and right sides of the brain
- Coronal: separate front from the back
- Horizontal (aka axial/transverse): separates top from bottom
- Locations of certain regions
- Rostral/anterior: front of the brain (rostral; rooster; beak is in the front)
- Caudal/posterior: back of the brain
- Dorsal/superior: top of the brain
- Ventral/inferior: bottom of the brain (V points down)
- Lateral: outer left or right side of the brain
- Medial: midline of the brain
7
Q
- LABEL THE DIAGRAM
- Brainstem
- 3 sections of brainstem
- 2 things it maintains
- Damage causes what?
- Cranial nerves: what they do?
- Where do cranial nerves the brain?
- Thalamus
- Where is it?
- 3 fx
- Which perceptual input does not pass through a specific nucleus in the thalamus?
- Which nucleus signals from the retina enter?
- Which nucleus signals from the cochlea?
- 3 things thalamo-cortical loops facilitate?
A
- Brainstem
- has 3 main sections: medulla, pons, and midbrain
- The 3 structures help maintain homeostasis and degree of wakefulness
- Damage to the 3 structures -> coma or death
- The portal (entrance) for cranial nerves
- Cranial nerves receive sensory input from and send motor output to the head + neck
- Thalamus
- The large egg-shape structure on top of the brain stem
- We have 2 thalamus, 1 for each hemisphere
- (#3) It has many separate nuclei that direct the traffic in the brain
- Thalamus is the “gateway to the cortex”,
- it relays info up to the cortex
* All perceptual input (except smell) pass through a specific nucleus in the thalamus, then enters the appropriate cortical region
* Ex. signals from the retina enters the lateral geniculate nucleus, then the primary visual cortex
* Ex. Signals from the cochlea enters the medial geniculate nucleus, then the primary auditory cortex
* Ex. signals from the basal ganglia, cerebellum, and amygdala enters the thalamic nuclei, then reach their cortical targets
- it relays info up to the cortex
- Thalamus receives feedback from the cortex
* Each specific area in the cerebral cortex has bidirectional (2-way) connection w/ a specific part in the thalamus
* These thalamo-cortical loops facilitate attention, STM, coordination of diff brain regions (ex. mental representations)
- Thalamus receives feedback from the cortex
8
Q
- LABEL THE DIAGRAM
- Hippocampus location
- Fornix & Mammillary body fx
- 4 steps Memory consolidation process
- Patient HM
- Which part was removed
- What was the consequence of surgery
- 3 things he can’t remember
- 2 things he can
- Amygdala location
- 3 fx
- Patient SM
- 2 things she can’t do
- 2 other specific fx of amygdala
A
- Hippocampus
- Aka Giant seahorse in Greek - Looks like a seahorse tail
- Located in the temporal lobe
- Fornix (blue box) & mammillary body: crucial to establish LT declarative memory
- LT declarative memory: mem that can be verbally retrieved and reported
- Ex. facts (current president)
- Ex. autobiographical info (personal life info, where you went to HS)
- LT declarative memory: mem that can be verbally retrieved and reported
- Memory consolidation process
- hippocampus receives lots of convergent input from cerebral cortex
- Then it processes the input by registering the spatiotemporal info for related experiences
- Then, hippocampus retains these complex patterns
- After some time (ex. years), the hippocampus transfers this info back to the original cortical areas, which is stored semi-permanently in strongly weighted synaptic connections
- Ex. Patient HM
- Had amnesia after his medial temporal lobes were surgically removed
- The medial temporal lobes were removed as a last resort to alleviate epileptic seizures
- After the surgery, his seizures stopped, but
- he can’t remember anything that happened to him since 16 yo
- can’t remember simple things: who he had for his last meal, where he lived, own age
- can’t learn the meanings of new words
- IOW: this suggests hippocampus is essential for linguistic process
- However, he has STM and can learn new motor skills
- This suggest these abilities rely on other brain mechanisms
- Ex. Patient HM
- Amygdala
- Located at the anterior tip of hippocampus
- means almond in Latin
- 1 Responsible for emo processing
- 2 Helps us assess the significance/ value of the stimuli
- 3 Sensitive to dangerous situations
- Patient SM
- Her amygdala developed abnormally in both hemispheres
- 1 So, she cannot recognize fear expressions in other people’s faces
- 2 She does not feel fear
- Researchers brought her to haunted house
- She reacted to the monsters by laughing, smiling, and talking to them
- She scared the monsters too
- She went through traumatic life events
- She only felt angry and upset, never fearful
- Amygdala helps promote adaptive b in threatening situations, and perceiving emotional prosodic patterns in speech (aka emotion in speech)
9
Q
- LABEL THE DIAGRAM
- Basal Ganglia location
- 4 main structures in Basal Ganglia
- 2 structures in Striatum
- Substantia nigra fx
- How the Basal Ganglia works - 3 steps
- 5 fx of basal ganglia
- Cerebellum location
- % of neurons in the brain in here
- Purkinje neurons
- 3 fx of cerebellum
- If cerebellum is damaged, 3 main cons
A
- Basal Ganglia
- Basal ganglia: contains several integrated nuclei, located near the thalamus
- Basal Ganglia contains the following structures
- Striatum: includes the Caudate nucleus and Putamen
- Globus pallidus or pallidum: has a lateral and medial portion
- Subthalamic nucleus
- Substantia nigra: located in the midbrain, generates dopamine, projected into the striatum
- How the Basal Ganglia works
- Striatum receives signals from the cerebral cortex; Striatum recognizes. The signals from familiar situations (ex. I walk up to the door of my fav restaurant)
- Striatum sends this signal to 2 // routes
* “go” pathway: this pathway implicitly learn what types of actions are adaptive in certain situations (ex. push the door)
* “no-go” pathway: this pathway learns what types of actions are maladaptive in certain situations (ex. don’t pull the door)
- Striatum sends this signal to 2 // routes
- The output from these 2 pathways (i.e. recommendations on what to do or not) are sent to the frontal cortex via thalamus for further consideration
- Basal Ganglia is essential for unconscious acquisition, selection, initiation, and cessation (aka habits OR procedural skills) in motor and cog control
- It influences our motor control (ex. Parkinson’s, Huntington’s)
- It influences our cog control (ex. schizo, OCD)
- IOW: It influences overt b and covert thoughts
- Cerebellum: located behind the medulla and pons
- Aka little brain in Latin
- But, it has more than two thirds of all the neurons in the brain
- Contains Purkinje neurons
- Purkinje neurons have many dendrites, and receive 200k signals from other cells
- Cerebellum regulates muscle tone, balance, and movement control
- Damage to cerebellum: leads to loss of balance, jerking/tremoring from arms and hands, impairs articulatory control causing dysarthria (slurred speech)
- IOW: cerebellum influences movement and cognition
- Cerebellum: located behind the medulla and pons
10
Q
- LABEL THE DIAGRAM
- Cerebral cortex
- Cortex in latin = ?
- Size?
- # of neurons?
- # of connections
- Grey matter - location?
- White matter location?
- 5 major lobes
- 4 visible lobes
- 1 invisible lobe
- Sulci fx
- Central sulcus
- Lateral sulcus/sylvian fissure
- 2 arbitrary lines
A
The Cerebral Cortex
- Most highly evolved part of human brain
- It takes up 3.5 pieces of letter sized paper; which is crumpled up to fit in the skull
- The cortex has 30 billion neurons, each neuron contacts 1000 other cells
- Gray matter: refers to the grey neuron cell bodies in the cortex
- White matter: subcortical tissue is white due to myelinated axons
The Major Lobes–—Visible and Hidden
- There are 5 lobes
- 4 visible lobes on the cerebral cortex
- Frontal
- Parietal
- Temporal
- Occipital
- 1 Invisible lobe: Insula
- Insula = island in Latin
- The borders are defined by sulci
- Central sulcus: separates the frontal and parietal lobes
- Lateral sulcus/sylvian fissure: separates the temporal lobes from the frontal + parietal lobes
- An arbitrary line: separates the occipital lobe from the parietal and temporal lobe
- This line connects the parieto-occipital sulcus (dorsal) with the preoccipital notch (aka dent) (located ventrolateral)
- The other arbitrary line is perpendicular to the line above and extends to the end of the sylvian fissure
- This separates the occipital from temporal lobe
11
Q
- LABEL DIAGRAM
- Gyri
- Sulci
- 2 reasons why gyral-sulcal organization is adaptive
- Axon density in Gyri vs sulci
- How do sulci and gyri form?
- shape and size ulci and gyri: env or genetic?
A
Gyral–Sulcal Organization
- Gyri: bulges
- Sulci: grooves
- This gyral-sulcal organization is adaptive
- It squeezes a lot of surface area into a small space
* Two thirds of the cortex is in the sulci
- It squeezes a lot of surface area into a small space
- It reduces the amount of axonal wiring
* This reduces the distance signals travel
- It reduces the amount of axonal wiring
- In humans and other mammals, axons projecting in the gyri are denser than axons projecting in the sulci
- This suggest the gyral-sulcal patterns are caused by stiff axons constantly pushing harder against some regions on the cortical surface (like condom)
- Since the skull is a physical constraint, the pushed regions protrude outward and form gyri; the other regions bend inward to form sulci
- shape and size of gyri and sulci is mainly genetic
- This is mainly genetically influenced (slightly env influenced)
- Research showed that cortical convolutions are more similar in MZ than DZ twins
- Diagram structures
- Figure 1.17
- 2 structure in the sylvian fissure on the dorsal surface of temporal lobe (aka supratemporal plane)
- HG = Heschl’s gyrus (aka transverse gyrus)
- PT = Planum temporale
- Both are key for language and speech processing
12
Q
- cytoarchitectonic organization
- cortex thickness
- # of horizontal layers?
- Layer I, II, III fx
- Layer IV
- Layer V
- Layer VI
- Define vertical columns
- diameter?
- # of neurons
- Brodmann’s map
- Which area does it map out?
- # of Brodmann areas?
- Areas range?
- Why are some #s omitted?
- 2 cons?
- Which BA area is confirmed?
- Which BA area is challenged?
- How many distinct areas does each bran hemisphere has in reality?
- Is Brodmann map a structural or functional map of the brain?
A
Cytoarchitectonic Organization
- Cytoarchitectonic organization: whether there is packing density, and layers of diff types of cells
- The cortex is 2-4 mm thick
- Has 6 diff layers of cells stacked
- Each layer of cells differs in morphological and connectional properties
- Layers I, II, III: communicate w/ other cortical areas
- Layer IV: receives input from thalamus
- Layer V: sends output to subcortical motor structures
- Layer VI: sends output to the thalamus
- These layers are horizontal
- There are vertical columns
- Vertical columns: perpendicular to horizontal layers; basic functional units of the cortex
- Each column is 0.4 mm in diameter
- There are 100 neurons tuned to respond to similar features from the external or internal env
- Scientists tried to make maps of the cortex
- Brodmann’s map
- the lateral and medial view of a human’s LH
- there are 43 cortical areas OR Brodmann areas (Bas)
- The areas ranged from 1 to 52
- Brodmann omitted 12-16 and 48-51 b/c he used these #s for certain areas in other mammals, but he can’t find them in humans
- In 1980s: BAs are often used w/ gyri and sulci labels to refer to specific cortical regions
- It helped interpret fMRI
- BAs weakness
- No info on the boundaries inside the sulci
- It is based on subjective observations; does not consider individual differences in anatomy
- Modern imaging methods confirmed some BAs
- Ex. BAs 44 and 45 do exist in the FL (BA 44 and 45 are usually collectively referred as the Broca’s area)
- Modern imaging methods challenged some BAs
- Ex. BAs 39 and 40 can be further carved into 7 areas
- Currently, we know that each human brain hemisphere has 150-200 distinct areas
- Main point: we should treat BA as structurally defined regions (rather than functionally)
13
Q
- LABEL DIAGRAM
- Connectional Organization
- What type of axons carry info b/w cortical regions?
- Corpus callosum - what it does?
- What matter type?
- How many axons?
- What do split brain patients help rs study?
- What are Fasciculi?
- Arcuate fasciculi fx
- In which hemisphere?
- which 3 regions does it secure?
- What are the 3 connecting segments?
A
Connectional Organization
- Cortical regions do not work in isolation; they work together to carry out complex mental processes (ex. language)
- The signals are carried by axons that flow through white matter (like highways)
- Corpus Callosum (CC): white matter tract w/ 100 million axons that connects the 2 hemispheres
- The biggest and busiest tract
- split-brain patients allow neuroscientists to examine the behavior from each hemisphere
- Fasciculi: white matter tracts that connect diff cortical areas w/in the same hemisphere
- Arcuate fasciculi: responsible for linguistics
- In LH
- It has 3 separate branches that undergird (secure) 3 regions
- Broca’s territory: posterior part of inferior frontal gyrus (BA 44 + 45) and adj portions of middle part of frontal gyrus and precentral gyri
- Wernicke’s territory: Posterior portions of the superior and middle temporal gyri
- Geschwind’s territory: supramarginal gyrus and angular gyri
- The long direct segment: links Broca’s w/ Wernicke’s territory
- Anterior indirect segment: links Broca w/ Geschwind’s territory
- Posterior indirect segment: links Wernicke w/ Geschwind’s territory
- Arcuate fasciculi: responsible for linguistics
14
Q
Connectional Organization cont
- LABEL THE DIAGRAM
- 3 other language related fasciculi
- Diffusion tractography
- Human connector
A
- Other language related fasciculi
- Inferior fronto-occipital fasciculus: links inferior frontal area w/ occipital area
- Inferior longitudinal fasciculus: link temporal areas w/ occipital areas
- Uncinate fasciculus: link OBF area w/ anterior temporal areas
- Main point: there are many long distance fibre tracts that tie the cortical regions together
- This allows for producing and understand language
- Diffusion tractography: measures passive movement of water along axons in white matter (uses MRI techniques)
- This allows us to reconstruct the directions of fibre tracts (as seen in Fig 1.21, 1.22)
- Human connectome: a project that maps all the connections in our brain
15
Q
- Sensory, Motor, and Higher-Order Systems
- 3 primary sensory regions
- Which cortex does visual info enters?
- BA#?
- Aka?
- Location - which fissure?
- Location - which part of which lobe?
A
Sensory, Motor, and Higher-Order Systems
- Sensory: vision, audition, and somatosensory
- Vision
- Visual info enters the primary visual cortex in the occipital lobe
- Primary visual cortex, aka BA17, V1, Striate cortex
- This cortex is located in the calcarine fissure (Calc F), which is on the medial surface of the occipital lobe
16
Q
- Sensory, Motor, and Higher-Order Systems cont 2
- Retinotopic organization
- 2 separate streams at the anterior edge of occipital lobe
A
- PVC has retinotopic organization
- Retinotopic organization: preserves the spatial arrangement of signals from the retina
- The PVC projects forward to other occipital areas that are specialized to extract info on specific attributes of visual stimuli (ex. form, color, motion, depth)
- At the anterior edge of the occipital lobe, the flow splits into 2 separate streams
- “what” pathway: extend to ventral temporal lobe, it recognizes objects based on shapes, colors, and textures
- “where” path: extend to posterior parietal lobe, represent the locations of objects in relation to each other and in relation to the viewer’s body
* Aka “how” pathway: promotes visuomotor transformations for object-directed actions- Ex. convert the position of a coffee mug based on the eye-centred coordinates into hand-centred coordinates
- “where” path: extend to posterior parietal lobe, represent the locations of objects in relation to each other and in relation to the viewer’s body
As a result, you can reach out and grasp the cup
17
Q
- LABEL THE DIAGRAM
- Sensory, Motor, and Higher-Order Systems cont 3
- Auditory
- Location - gyrus?
- Location - fissure?
- Tonotopic organization
- hemispheric asymmetries
- Where are complex auditory fx done? - 3 parts
- Somatosensory
- postcentral gyrus fx
- BA #s?
- aka?
- Define Somatotopic organization
- large cortical areas means what?
- 3 types of signals it processes
- What info do signals from tendons provide?
- 3 areas that do complex processing of somatosensory info?
- Auditory
A
- Auditory
- Primary auditory cortex is in the Heschl’s gyrus (located in the Sylvain fissure)
- Primary auditory cortex area has a tonotopic organization
- Tonotopic organization: cortical columns next to each other respond specifically to sound frequencies that are next to each other
- PAC has hemispheric asymmetries: left PAC has more input from the right ear and vv
- Complex auditory functions are done in the Planum temporale (PT), superior temporal gyrus, and middle temporal gyrus
- Somatosensory cortex (aka postcentral gyrus)
- postcentral gyrus (i.e. BA 1,2, and 3): Signals for felt shape and texture of objects, temp, pressure, and pain are first processed here
- These BAs have diff fx; but are collectively referred to the primary somatosensory cortex (i.e. S1)
- This region has rich somatotopic organization
- Somatotopic organization: cortical representation that captures the body layout in a vertical way, upside down
- w/ disproportionately large amounts of cortical territory for the most sensitive parts of the body (i.e. hands, feet, lips, tongue, and genitals)
- NOTE: there is some discontinuities
- Ex. face area is not next to the neck area; it is below the hand area
- Ex. Genital area is not next to the upper leg area, but below the food area
- the primary somatosensory cortex processes singals from the skin, muscles and tendons
- Signals from the tendons carry proprioceptive info about the relative positions of one’s body parts in space and about the forces acting on them
- Sophisticated analyses are done by the posterior and inferior parietal lobe, and the insula
22
Q
- Neuropsychology cont 2
- Matzig et al 2009
- Methods
- Results
- Rapp and Caramazza 2002 - In-depth study of patient KSR
- Method
- Results
- 2 explanations
- Groups and indiv
- Group: pros, 3 cons
- Syndrome
- Indiv
- Matzig et al 2009
A
- Matzig et al 2009
- 63 patients w/ noun-verb dissociations
- The diff b/w 2 categories of words = 30%
- Findings suggest that the 2 abilities (i.e. name objects w/ nouns, name actions w/ verbs) depend on at least partially distinct cog mech that can be selectively disrupted
- Note: noun-related and verb-related picture naming deficits can b0 due to problems at several different lv of representation and computation
- Ex visual, conceptual, grammatical, and phonological
- Need more careful investigation
- Rapp and Caramazza 2002
- In-depth study of patient KSR
- There is double dissociation in KSR who has brain damage
- There is an interaction b/w v of grammar category and output modality
- Patient had sig more trouble w/ nouns than verbs in oral production BUT more trouble w/ verbs than nouns in written production
- Method: sentence completion paradigm w/ noun-verb homophones (same word diff meaning)
- Show patient KSR a “carrier sentence” & a pic of the object or action
* Carrier sentence - Ex. Give me the (fish); I want to (fish)
- Show patient KSR a “carrier sentence” & a pic of the object or action
- Results: produced spoken nouns less accurately (40%) than spoken verbs (80%)
- Produced written verbs less accurately (50%) than written nouns (90%)
- 2 possible explanations
- The meanings of nouns and verbs are segregated w/in the semantic system
* Although both types of concepts are still intact for KSR, she has 2 impairments
* 1. Issue with the object concepts/nouns to speech (phonology)
* 2. Issue with action concepts (verbs) to writing (orthography)
- The meanings of nouns and verbs are segregated w/in the semantic system
- The forms of nouns and verbs are separated in the speech and written output. KSR has 2 impairments
* 1. Can’t form nouns in speech
* 2. Can’t form verbs in writing
- The forms of nouns and verbs are separated in the speech and written output. KSR has 2 impairments
- 2 possible explanations
- Main point: detailed neuropsychological studies uncover fine-grained disorders
- NOTE: Single and double dissociations can apply to other domains in language (not just noun-verb tasks)
Groups and Individuals
- Group studies and individual studies each have their own pros and cons
- Group studies
- Pros: allow rs to test hypothesis on correlations b/w disturbances from particular mental abilities and lesions
- If a deficit reliably results from damaging a specific area, we should conduct group studies with
- patients w/ + w/o impairment
- patients w/ + w/o injury
- If a deficit reliably results from damaging a specific area, we should conduct group studies with
- Cons: limited on how carefully behavioural criteria is defined
- Each patient has individual set of symptoms due to idiosyncratic brain damage
- Group studies need to clearly specify the type of impairment that affects the behaviour to sort patients
- Many rs focused on groups of aphasic patients who belong to certain “syndromes”
- Syndrome: collection of symptoms that tend to co-occur statistically
- Ex. Broca’s aphasia is a syndrome
- Some Symptoms:
- Can’t produce complex sentences
- Worse retrieval of verbs than nouns
- Poor articulations
- Some Symptoms:
- Most rs treat patients as similar in their studies
- Caramazza et al think this is invalid
- These patients do not have all the same symptoms
- They think syndromes like Broca’s aphasia lack empirical and theoretical use
- Some think we should sort patients based on presence or absence of particular symptoms
- Issue: symptoms like “worse retrieval of nouns than verbs in picture naming tasks” can have several different causes (see Rapp and Caramazza 2002 abv)
- Pros: allow rs to test hypothesis on correlations b/w disturbances from particular mental abilities and lesions
- Individual studies
- Provide insight on how the mind/brain is organized
- Ex. Patient HM in Ch 1 helped rs develop theories on the role of hippocampus for LTM, and amygdala for emo processing
24
Q
- Neuropsychology cont 4
- Types of brain damage
- Stroke
- Aka
- what happens?
- What is the most common type?
- What happens to it?
- 2 types of ischemia
- differences?
- What happens if it blocks brainstem?
- What happens if it blocks white/cortical matter?
- How to alleviate the deficits?
- What happens if the deficit is not alleviated
- Traumatic brain injury
- Age group this is most common in?
- 2 main types
- When are they likely to happen?
- Gabrielle Giffords
- Neurodegenerative and Infectious Diseases
- How are these diseases different that stroke and TBI?
- their 2 main targets
- the 10 disorders related to language (7 affect language in indirect ways; 3 PPA)
- disorder name
- type
- affected brain region
- PPA?
- voxel-based morphometry (VBM)
- What imaging technique?
- 2 step process
- Stroke
A
Types of Brain Damage
- Stroke (aka cerebrovascular accident – CVA)
- Occurs when blood supply to a particular part of the brain is interrupted
- Common type: ischemia
- Blood vessel in the brain is obstructed by a clot, and this deprives downstream tissue of oxygen
- Thrombotic ischemic stroke: the clot forms w/in the blood vessel eventually gets clogged
- Embolic ischemic stroke: clot originates in a diff part of the circulatory system (ex. heart, large vessels of upper neck and chest)
- This travels up to the brain and get stuck in the capillaries
- If it blocks sectors of the brainstem for basic life functions -> person will lose consciousness and die in minutes
- If it blocks certain cortical and white matter areas that support specific cog capacities, the person lives but the cog capacities are compromised
- Ex. strokes that block the posterior cerebral artery that supplies to occipital areas -> visual impairments
- Ex. Strokes that block the middle cerebral artery that supplies to the perisylvian areas for linguistics -> linguistic impairments
- Deficits can be partially or completely alleviated if blood flow is rapidly restored to the deprived tissue
- If not, the tissue will die and become absorbed
- This leaves a cavity that gets filled w/ CSF
- Traumatic Brain Injury
* The most frequent form of brain damage suffered by ppl under 40
* 2 main types
* 1. Closed head injury
* Occurs when person sustains a sudden blow to the head that damages the brain and leaves the skull intact
* Ex. car accidents, sporting events
* Ex.
* Superficial damage to left perisylvian territory
* Patient had aphasia, but not motor or sensory deficits
* 2. Open head injury
* Both the brain and the skull are penetrated by an object (ex. bullet, shrapnel)
* Ex. Gabrielle Giffords
* Forced to resign from her set in US House of Representatives after being shot in the head on 2011
* Remains seriously disabled- Neurodegenerative and Infectious Diseases
- Brain damage from stroke and TBI have immediate effects
- Neurodegenerative and infectious disease are progressive
- There are many disorders and all involve gradual atrophy (i.e. tissue loss) in specific regions/sets of regions in the brain
- These disorders target particular networks that
- Have a strong functional-anatomical connection
- Are sig correlated to grey matter volume
- 10 disorders have cons for language (table)
- First 7 affect language in indirect ways
- They impair certain aspects of perception, memory, cognition, and motor control that are necessary for efficient production and comprehending words/sentences
- Last 3 are PPA
- PPA = primary progressive aphasia
- PPA target core components of language circuitry
- Distinctive patterns of slowly worsening language deficits
- Distinctive patterns of regionally specific atrophy
- The 3 PPA have nonoverlapping distributions of cortical atrophy
- 3 types
- Nonfluent/agrammatic variant: tissue loss in left inferior frontal cortex
- Semantic variant: anterior temp lobe (bilaterally)
- Logopenic variant: left temperoparietal area
- First 7 affect language in indirect ways
- voxel-based morphometry (VBM)
- A type of MRI
- It divides the brain into thousands of voxels (i.e. tiny cubes)
* Each cube is a volume (similar to pixels)
* 2. determines concentration of grey and white matter in each voxel
* Rs can determine the locations and magnitudes of atrophy in patients w/ neurodegenerative/infectious diseases
* Then compare them to healthy controls
- It divides the brain into thousands of voxels (i.e. tiny cubes)
- Neurodegenerative and Infectious Diseases
- Traumatic Brain Injury
25
Q
- Neuropsychology cont 5
- Tumours
- Definition
- Glioma: definition
- Growth rate
- Kinno et al 2009
- Japanese-speaking patients w/ gliomas affecting Broca’s area
- Method
- Results
- Using behavioral data and lesion data
- 3 steps Lesion Overlap and Subtraction Analysis
- Tranel and Kemmerer 2004 - understand neural basis of impaired knowledge on meanings of location prepositions
- Locative prepositions
- Part 1
- Methods
- 4 tasks
- Results
- Methods
- Part 2
- Method
- Results
- Voxel-Based Lesion–Symptom Mapping (VLSM)
- 3 steps
- Wu et al 2007 - VLSM & locative prepositions
- 3 caveats About Neuropsychological Research on Structure–Function Relationships
- 2 ways where areas are dysfunctional and may not show up on MRI
- Apraxia of Speech (AOS)
- Nina Dronkers 1996
- Method
- Results
- 3 limitations
- Argye Hillis 2004
- Methods
- Results
- What went “wrong” w/ Dronker’s study?
A
- Tumours
- Lesions can be due to tumors
- Tumours: masses of tissue that grow abnormally and serve no physiological purpose
- Several type (classified based on how they dev, and likelihood to recur after surgical removal)
- Glioma
* Come from white matter and expand outward -> destroy or displace neurons
* Variable rate of growth (can be v slow or fast)
* Glioma patient studies are useful
* Kinno et al 2009
* A group of Japanese-speaking patients w/ gliomas affecting Broca’s area had sig worse comprehension for passive sentences than active ones- Ex. Passive – Person A is being pushed by Person B
- Ex. Active – Person A is pushing Person B
- Original stimuli: Japanese sentences paired w/ scenes with 2 ppl
* Another study - Showed these patients’ lesion sites overlapped w/ an area that was engaged sig more by passive than active sentences based on another fMRI study
- They compared them to healthy controls who did the same task
* Since the neuropsychological data and fMRI data aligns, this shows reliable inferences can be drawn from Glioma studies
- Glioma
Relationships Between Behavioral Data and Lesion Data
- -> discuss how groups studies are conducted
- Lesion Overlap and Subtraction Analysis
- Two groups of patients
* Gp A w/ deficit of interest
* Gp B do not have it
- Two groups of patients
- Each groups has separate procedures
* Reconstruct the patients’ lesions on a standard brain template
* Calculate how much overlap for every voxel
- Each groups has separate procedures
- Lesion overlap map for patients w/ deficit minus lesion overlap map for patients w/o deficit -> remaining area = areas of damage that is linked w/ deficit
- Tranel and Kemmerer 2004
- Tried to identify the neural basis of impaired knowledge on meanings of location prepositions
- Locative prepositions:
- Ex. in, on, around, through, above, below
- Methods
- 4 tasks given to 78 brain-damaged patients (from stroke)
- Naming (80 items)
* Ppl are shown objects and are asked to orally name the location of one object relative to another
- Naming (80 items)
- Matching (50 item)
* Ppl are shown 3 spatial arrays of objects w/ a preposition
* Told to choose which array best represent the preposition
- Matching (50 item)
- Odd one out (45 items)
* Ppl are asked to choose which one involves a type of relationship that is different from the other two
- Odd one out (45 items)
- Verification (44 items)
* Ppl are shown a spatial array of abstract shapes together and a preposition
* They need to decide whether the preposition correctly describes the array
* * Results
- Verification (44 items)
- Very variable: some failed none, some failed one task, some failed all 4 tasks
- Those who failed all 4 tasks may have impaired knowledge on the location preposition meanings
- Those who only failed only 1 task had unimpaired knowledge on meanings but may have individual disturbances on certain processes
- Part 2
- Rs created lesion overlap maps for those w/o impairments; and one for those w/ impairments
- Then they subtract the maps from each other
- Result shows defective knowledge on the meanings of location prepositions is associated w/ damage in some areas in LH
- The cortex and underlying white matter in the inferior frontal, inferior parietal, and posterior superior temporal regions (red, orange, yellows)
- The analysis includes patents w/ the deficit of interest and those w/o
- So, the results provide strong evidence that the lesions mentioned are more likely than not to cause the deficit
- Voxel-Based Lesion–Symptom Mapping (VLSM)
- Administer a task to patients w/ various lesions
- Patients’ lesion sites are transferred to a standard brain template
* For each voxel, 2 gps of patients are formed:- Those w/ brain lesions vs those w/o
- Patients’ lesion sites are transferred to a standard brain template
- For each voxel, rs do a t-test to compare the behaviour performances of patients in the lesioned and non-lesioned groups
* The resulting t-values measures the degree on whether decreasing task performance is related to the presence vs absence of certain brain areas being damaged
- For each voxel, rs do a t-test to compare the behaviour performances of patients in the lesioned and non-lesioned groups
- IOW, VLSM allows rs to identify the neural reasons of deficits, quantify brain-behaviour relationships w/o classifying patients based on their impairment
- Wu et al 2007
- Used VLSM to study impaired knowledge of meaning of location prepositions
- 14 patients w/ LH lesions
- They do several tasks the sentence w/ location prepositions w/ 1 of 4 pics
- Results: accuracy range b/w 43% to 100%’ mean = 86%
- The lesioned areas are consistent w/ those from Tranel and Kemmerer (2004 – abv)
- A Few Caveats About Neuropsychological Research on Structure–Function Relationships
- 3 caveats
- To infer a causal relationship b/w an impaired ability and damage to a specific region, need to show that
* Patients w/ deficit have lesions at that site
* Patients w/ lesions at that site tend to have the deficit
- To infer a causal relationship b/w an impaired ability and damage to a specific region, need to show that
- Deficit-lesion correlations for those w/ stroke/TBI in the chronic period can be diff from those in the acute period
* Chronic period: 6+ mo after lesion onset
* Acute period: less than 6 mo after lesion onset
* This is b/c acute patients w/ small lesions recover fast; the intact areas “take over” the affected fx
- Deficit-lesion correlations for those w/ stroke/TBI in the chronic period can be diff from those in the acute period
- Some impairments may be due to areas that are not structurally damaged
* These areas are dysfunctional and may not show up on MRI
* 2 ways
* A. Hypoperfusion: receives enough blood supply to survive but not enough to operate normally
* B. Diaschisis: they depend on axon input from the site of structural damage; but the input is no longer available
- Some impairments may be due to areas that are not structurally damaged
- Apraxia of Speech (AOS): disorder of articulatory programming in Broca’s aphasia
- AOS affect high-level motor aspects of orchestrating speech
- This leads to distorted consonants, vowels, and prosody
- Patients know what they want to say and how it should sound, but cannot coordinate the articulators (i.e. lips, tongue, jaw, and palate) to produce the output
- Nina Dronkers 1996
- Showed 25 chronic stroke patients w/ AOS had 100% lesion overlap in one LH region – superior anterior part of the insula
- 19 chronic stroke patients w/ AOS had that damage
- 3 limitations (related to 3 caveats above)
- Results show that AOS is associated w/ a damaged area of insula; but it doesn’t tell if damage to that area give rise to AOS
* It is possible that AOS may also involve damage in other areas
- Results show that AOS is associated w/ a damaged area of insula; but it doesn’t tell if damage to that area give rise to AOS
- All the patients were chronic; acute patients may show diff deficit-lesion correlation
- The study only focused on structural damage
* Other areas that are intact but are dysfunctional by contribute to AOS
- The study only focused on structural damage
- Argye Hillis 2004
- Addressed the 3 limitations in Dronker’s study
- Methods
- Selected 80 stroke patients based on site of structural damage
* 40: lesion on any part of the left insula
* 40: spared that area
- Selected 80 stroke patients based on site of structural damage
- Patients were eval for AOS when they were acute (24 hr of stroke onset)
- Patients were scanned of tissue damage, and also areas of hypoperfusion (sig reduced blood flow)
- Results
- Abnormalities in region of interest (superior anterior part of left insula) is not sig related to AOS
- 12 out of 29 patients (40%) who had damage or hypoperfusion in that area showed AOS
- 19 out of 51 patients (40%) who did NOT hv damage or hypoperfusion in that area showed AOS
- AOS is actually associated w/ abnormalities in Broca’s area
- 26/30 (90%) who had damage or hypoperfusion in that area showed AOS
- 5/50 (10%) who did NOT hv damage or hypoperfusion in that area showed AOS
- Abnormalities in region of interest (superior anterior part of left insula) is not sig related to AOS
- What went “wrong” w/ Dronker’s study?
- The insula is the most vulnerable to stroke due to anatomy
- Maybe 80% of Dronker’s chronic patients had damage to Broca’s area, while the remaining patients had hypoperfusion in that area
27
Q
Fx neuroimaging cont 2
- fMRI
- What is it sensitive to?
- BOLD
- 12 second hemodynamic response function (4 steps)
- Is BOLD correlated to input or output processing of neurons
- Spatial and temporal resolution
- 3 Pros of fMRI over PET
- 2 Cons
A
- Functional Magnetic Resonance Imaging (fMRI)
- Sensitive to degree of oxygenation of blood in diff parts of brain
- Blood oxygenation level dependent signal (BOLD)
- Endogenous contrast agent: deoxygenated blood reduces the MRI signal; oxygenated blood increases this
- When hemoglobin is not carrying any oxygen, it behaves like a small magnet and disrupts the local magnetic field
- This reduces the signal received by the fMRI machine
- When hemoglobin is carrying oxygen, it is less magnetic
- The fMRI can still detect them as a small increase in resonance signal
- 12 second hemodynamic response function
- When neurons in a specific area increase in activity, they consume the oxygen that is immediately available
- As a result, there is more deoxygenated blood in that area, and the fMRI will pick up a small decrease in BOLD signal for 2s
- In the next 5s, more oxygenated blood is detected in that area, and the fMRI detects this as a gradual increase in the BOLD signal
- For the next 5s, the signal will return to baseline and briefly undershoots
- The BOLD signal maybe more correlated to the input processing of neurons rather than output
- Spatial resolution: 1-3 mm
- Temporal resolution 50-100 ms
- Pros of fMRI over PET
- Cheaper: doesn’t need a medical cyclotron
- Safer: doesn’t use radioactive isotopes
- Better spatial and temporal resolution
- Cons
- It is very noisy
- BOLD signals are distorted near air-filled cavities
* It is tricky it get data from some brain regions, esp the anterior temporal lobes located near the sinuses
* (rs found a way around this)
- BOLD signals are distorted near air-filled cavities
30
Q
Experimental paradigms
- Which study design are experimental paradigms usually used w/?
- Subtraction paradigm
- What study designs can used this paradigm?
- What neuroimaging methods can use this paradigm?
- Methods - how to use
- Narain et al 2003: Aims to disclose brain regions linked w/ auditory processing of intelligible vs unintelligible sentences
- 4 conditions
- Methods
- Final activation map
- Correlation paradigm
- What study designs can used this paradigm?
- How it works
- Mobbs et al 2010 - Looked at the neural activity associated w/ monitoring the threat value of a tarantula
- Methods
- Results
- Davis and Johnsrude 2003 - Used correlation paradigm to further explain the neural underpinnings of intelligible and unintelligible
- Methods
- 5 conditions
- 3 diff degrees of intelligibility
- Results
- Subtraction paradigm
- Correlation paradigm
- Follow up analyses
- Multivariate Pattern Analysis
- How is it different from subtraction and correlation paradigm?
- What it does?
- Mur et al 2009/ Raizada et al 2010
- orthogonal pattern detection
- Abrams et al 2013 -Used MVPA to examine the neural substrates that process intelligible vs unintelligible utterances w/ better precision
- Methods
- Analysis
- subtraction
- MVPA
- Results
A
Some Basic Experimental Paradigms
- Subtraction, correlation, and pattern analysis are mainly used w/ event-related design, but occasionally w/ block design
- Subtraction paradigm
- First paradigm used in fx neuroimaging
- Can be used with blocked and event-related designs
- Used by fMRI and PET rs
- Helps rs isolate neural correlates of specific cog capacities
- Study design: 2 conditions
- Experimental: ability of interest
- Baseline/Control: does not include ability of interest, equivalent in other aspects
- Study design: 2 conditions
- Collect imaging data
- Map of brain activity w/ experimental condition “-“ map of brain activity w/ control condition
* The regions that still show up is sig engaged in the experimental condition; this is treated as uniquely contributing to the ability of interest
- Map of brain activity w/ experimental condition “-“ map of brain activity w/ control condition
- To enhance reliability, we include
- multiple experimental conditions that require the ability of interest (Ex. conditions A and B)
- multiple control conditions that do not (Ex. C and D)
- This allows rs to conduct conjunction analyses that increase the likelihood of pinpointing brain regions responsible for the interested ability
- Ex. If each experimental condition is well-matched w/ a particular control condition
- Ex. A w/ C, B w/ D
- Perform separate subtractions b/w corresponding conditions
- Conjoin outcomes of the independent analyses [(A – C) + (B – D)]
- The resulting brain map is quite restricted, and helps narrow the neural underpinnings of specific cog capacities
- Ex. If each experimental condition is well-matched w/ a particular control condition
- Narain et al 2003
- Aims to disclose brain regions linked w/ auditory processing of intelligible vs unintelligible sentences
- 4 conditions: 2 using intelligible stimuli, 2 using unintelligible stimuli
- Intelligible conditions
- A. Speech (Sp): normal sentences
- B. Vocoded speech (VCo): sentences that are artificially altered to have a rough sound quality but still can be understood
- Unintelligible conditions
- C. Rotated speech (RSp): Sentences that are spectrally rotated (i.e. inverted) so they sound like “alien” language;
- but still have phonetic features (ex. voiceless fricatives – “f”, “th”)
- D. Rotated vocoded speech (RVCo): Sentences that have been vocoded and spectrally rotated (i.e. inverted) so they sound like intermittent fluctuating static
- C. Rotated speech (RSp): Sentences that are spectrally rotated (i.e. inverted) so they sound like “alien” language;
- 11 ppl listened to blocks of stimuli from each condition during fMRI scanning
- All state they can only understand stimuli 2 out of 4 conditions
- Rs identified the brain regions that mediate extracting meaning from intelligible utterances using the “subtraction” method
- [(A – C) + (B – D)]
- [(Sp – RSp) + (VCo – RVCo)]
- Do 2 separate subtractions
* Each involves contrasting the activation evoked by intelligible stimuli against the matched set of unintelligible stimuli
* Intelligible and unintelligible conditions differ only by spectral rotation
- Do 2 separate subtractions
- Conjoin (add) activation maps from the 2 separate subtractions; this identifies the commonality
* This captures brain areas that respond to both intelligible stimuli
* This rule out areas that respond to only one intelligible stimuli and areas that respond to both unintelligible stimuli
- Conjoin (add) activation maps from the 2 separate subtractions; this identifies the commonality
- Final activation map
- Only 3 clusters of voxels are stat sig
- They are in the left lateral temporal lobe
- Some portion overlap with Wernicke’s area,
- Damage to that area disrupts phonological and lexical aspects of spoken language comprehension
- It’s possible lateral temporal region contributes to high-level auditory sentence processing, not low-level acoustic and phonetic info
- Note: analysis was restrictive
- Correlation paradigm (aka parametric paradigm)
- Compatible w/ blocked and event-related design
- The ability of interest here is a continuous variable that can vary; it is not all-or-nothing
- Subjects perform a series of tasks that uses the ability of interest in diff extent
- Rs look for brain regions where the activity level changes correspondingly
- Mobbs et al 2010
- Looked at the neural activity associated w/ monitoring the threat value of a tarantula
- Ppl were placed in fMRI, one foot is in a box w/ 5 compartments
- Ppl think they were seeing a live camera feed where a rs move a large tarantula from one box to another, closer/farther from their foot
* Reality: they are liking at a pre-recorded clip
- Ppl think they were seeing a live camera feed where a rs move a large tarantula from one box to another, closer/farther from their foot
- Results from parametric regression analysis
- As the spider got closer to the foot, brain activity increased in anxiety-related areas
- Dorsal anterior cingulate cortex, midbrain nuclei
- As thee spider got farther from the foot, the brain activity progressively increased in areas that are linked w/ passive coping w/ distant dangers
- Anterior orbitomedial PFC
- As the spider got closer to the foot, brain activity increased in anxiety-related areas
- This reveals the neural circuitry for arachnophobia
- Davis and Johnsrude 2003
- Used correlation paradigm to further explain the neural underpinnings of intelligible and unintelligible
- Intelligibility is on a continuum
- Used fMRI, subjects listened to diff stimuli
* Undistorted condition- A: Speech: normal sentences
* Partially distorted conditions - B: Vocoded speech: sentences altered to sound rough but intelligible (similar to Narain et al 2003)
- C: Segmented speech: sentences altered by dividing the speech stream into separate chunks and replace some parts w/ signal-correlated noise
- These parts retain many original acoustic features but lack recognizable sounds
- D: Speech in noise: sentences are placed in the background of continuous speech spectrum noise?
* Completely distorted condition - E: Signal-correlated noise: sentences altered in the same way in the “segmented speech” condition
- Here, all of the chunks are replaced w/ signal correlated noise -> so the stimuli is completely incomprehensible
- NOTE: in the 3 partially distorted conditions, there are 3 diff degrees of distortion leading to 3 diff degrees of intelligibility
- Here, all of the chunks are replaced w/ signal correlated noise -> so the stimuli is completely incomprehensible
- Based on pilot study
- High intelligibility: 90% of words reported correct
- Medium intelligibility: 70% of words reported correct
- Low intelligibility: 20% of words reported correct
- A: Speech: normal sentences
- Used fMRI, subjects listened to diff stimuli
- The subjects pressed buttons to rate the intelligibility of each stimulus on 4-point scale
- Results of analyses
- Subtraction paradigm: compared distorted condition w/ silence
- Sig bilateral activation in Heschl’s gyrus and surrounding auditory cortices
- Corelation analyses: see which brain regions respond w/ gradual increase in BOLD signals when the intelligibility of the stimuli increases
- The following regions show Neural sensitivity to cont variation in intelligibility of stimuli:
- superior and middle temporal gyri in LH; extends anteriorly to temporal area and posteriorly angular gyrus
- Similar to #1 but distributed more anteriorly in RH
- Small part of Broca’s area
- Subtraction paradigm: compared distorted condition w/ silence
- Follow-up analyses
- There is a single voxel in the left anterior temporal lobe that was sensitive to intelligibility
- Activated strongly to undistorted condition
- Activated weakly in completely distorted condition
- Activated w/ varying intensities across 3 partially distorted conditions depending on the amount of distortion
- (i.e. 90%, 70%, or 20% intelligible)
- IOW: the voxel is not sensitive to the diff ways they are distorted (vocoded, segmented, or embedded in background noise)
- There is a single voxel in the left anterior temporal lobe that was sensitive to intelligibility
- Take away from this study: brain mechanisms for comprehension of intelligible utterances involve the LH areas mentioned in Narain et al 2003’s study
- It also involves the RH
- Here, the correlation paradigm allows rs to discover more brain areas involved
- Gradual changes in the stimuli taps into diff brain regions
- Multivariate Pattern Analysis
- A new paradigm that can decode more fine-grained patterns of brain activity to more precision than the other paradigms
- In the subtraction and correlation paradigms, each voxel is independent, and the analyses shows separate measures of signal strengths
- When we use these paradigms to look at the whole brain, it looks at the mean response of each isolated voxel in each condition
- When we use it to look at the region of interest (ROI), it spatially averages the signals from all the voxels in the region for each condition
- Limitations: this ignores the relationship b/w voxels, and this can’t detect any info that is latent (dormant)
- MVPA can identify these dormant patterns, and relate them to cog abilities/tasks
- Mur et al 2009/ Raizada et al 2010
- MVPA can help explore whether the perception of similar syllables (ex. ra and la) is associated w/ distinct levels or patterns of brain activity in the superior temporal ROI spanning 9 voxels
- If the stimuli triggered orthogonal (right angle) 4-voxel activation patterns in ROI, the conventional analysis would miss this
- Conventional analysis would generate output that shows the same activity for both speech sounds and suggest that ROI cannot discriminate b/w the two
- MVPA can expose this separate pattern, and suggest the ROI contains at least partially non-overlapping neural voxels that represent the 2 syllables
- Point: MVPA is very useful
- Abrams et al 2013
- Used MVPA to examine the neural substrates that process intelligible vs unintelligible utterances w/ better precision
- Present 20 ppl w/ 2 types of stimuli, sequenced in alternating blocks
* A: Speech (Sp): Intelligible excerpts from famous speeches in 20 C
* B: Rotated speech (RSp): same experts but spectrally rotated (inverted) as in Narain’s 2003 study
- Present 20 ppl w/ 2 types of stimuli, sequenced in alternating blocks
- Ppl play close attention to each excerpt and push a button when it ended
- Rs conducted 2 analyses: Subtraction and MVPA
- I. Subtraction paradigm/General Linear model (A – B) -> (Sp – RSp)
- II. MVPA, searchlight version
- For every voxel in the brain, a 3 x 3 x 3 neighbourhood is made, centred in the given voxel
- W/in the 27-voxel space, rs determined is they were diff
- Results
- Red: conducted subtraction/General linear model (GLM) analysis
- Areas include 3 left lateral temporal regions (as seen in Narain et al 2003)
- Most of the bilateral temporal regions (as seen in Davis and Johnsrude 2003)
- Green: MVPA/ searchlight analysis; Also detected by GLM analysis
- There are 2 patches where the multi-voxel patterns of activity were sig diff for the two conditions
- Blue: MVPA/ searchlight analysis; NOT detected by GLM analysis
- Picked out RH areas the can discriminate b/w the two conditions
- Located in temporal, parietal, and FL
- They are associated w/ auditory sensory processing
- Conclusion: results suggest MVPA can resolve inconsistencies in the literature by being more sensitive in data analysis
- Red: conducted subtraction/General linear model (GLM) analysis
34
Q
Major Strengths and Weaknesses of the Different Methods
- Method
- Strength
- Weakness
A
41
Q
Tools of the trade cont 2
- ERP
- Pro, con
- Steinhauer, 2014, Applied Linguistics
- Method
- Results
A
ERP
- Behavioural studies are precursors of imaging studies
- Pros: Excellent for studying fast processing, which is common in language (we need good temporal resolution; helps us track changes over time).
- Cons: Relatively poor spatial resolution (without convergent evidence from other techniques/studies, data alone only tell you roughly which quadrant of the brain the signal came from).
- Don’t know the precise location where the signal is coming from
Example from Steinhauer, 2014, Applied Linguistics
- Method:
- Put on EEG cap
- Listen to sentences
* Ex. John ate broccoli at dinner
* Ex. John ate democracy at dinner
- Listen to sentences
- Results
- Blue vertical line: onset/when the words (i.e. broccoli or democracy) are spoken
- Results: brain signals look similar overall, except at N400 (blue = difference)
- N400: (400ms after onset)
- There’s a difference b/w processing the word that makes sense vs one that doesn’t make sense
- N400 relates to how comprehensible the sentence is
42
Q
Example of Combining Behavioural and Neuroimaging Techniques
- Baart, Armstrong, Martin, Carreiras, and Frost (2017)
- Exp 1
- Methods
- Exp 2
- Methods
- How is it different from Exp 1
- Purpose
- 4 noise conditions
- Results of behavioral exp 1
- Accuracy & RT
- Is having a lot noise as bad as predicted, why?
- Results = ERP Exp 2
- Analysis
- What it suggests
- 4 main insights
A
Example of Combining Behavioural and Neuroimaging Techniques
- From Baart, Armstrong, Martin, Carreiras, and Frost (2017)
- Method[EL1]
- Exp 1: behavioural experiment
- See and hear a Spanish word (ex. Apio)
- Press a button if what they see and hear match
- Participants had to go through 4 conditions
- no noise
- audio noise
- visual noise
- audio and visual noise
- Exp 2: same experiment but measure subject brain activity w/ EEG
- Only difference: there is a 1250 ms b/w read + listen to word and pressing the button
- Purpose: the actual act of pressing the button will activate the motor cortex
- this delay allows researchers to differentiate b/w when the brain is reading + listening to the word vs pressing the button
- Exp 1: behavioural experiment
- Method[EL1]
- Noise conditions
- No noise: white text on black background
- Visual noise: white dots on the “white text and black background”
- Audio noise
- Ex. play a random audio noise -> most ppl don’t know what word it is saying
- When someone told me the word is “actress”
- It seems obvious the word is actress in retrospect
- This suggests that when the audio information is not clear, presenting the word visually can clear up the ambiguity
- A + V noise (have audio and the visual noise presented)
- Results – behavioral exp 1
- Accuracy & RT: Ppl are the most accurate and fastest when there is no noise
- Auditory noise makes ppl slightly less accurate and a bit slower
- If you have more noise (i.e. A + V noise), you are the least accurate and the slowest
- But the effect is not as bad as it seems
- When we look at RT, AV noise is significantly slower compared to no noise
- For accuracy, the drop is not as bad
- But the effect is not as bad as it seems
- Results = ERP Exp 2
- Researchers did a lot of t-tests
- After controlling for this (the orange and blue), we get the results (black)
- The effects happen around N400 (~500 ms)
- This suggests that the integration of audio and visual noise is happening at the understanding/later semantic level (not early perceptual level)
Integrating insights
- Combined data point to cross-modal integration occurring at a relatively late time-point, at the level of lexical/semantic processing
- (combining info from 2 modalities happen later)
- Surprisingly, the constraints from sublexical units (individual letters / sounds) seems relatively weak. (most integration happens at lexical semantic lv)
- Potentially due to language tested (Spanish).
- Transparent orthography: every letter maps onto a particular sound, and vv
- Results may not apply to other languages that do not have transparent orthography (ex. Eng, Hebrew)
- Points to value of Cross-linguistic comparisons another type of study that transcends any particular technique
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[EL1] Understand these experiments well and the significance of their results
