thinking brain lecture 1

Question 1

Describe the human cortex

Answer 1

Large surface area
>1 trillion synapses
Most complex neural stucture in brain

Mediates:
– Voluntary motor
activity
– Sensory perception
– Learning and memory
– Language
– Affective disorders

Question 2

What are the 5 parts of cortex?

Answer 2

Frontal -
Parietal
Temporal
Occipital

Also brainstem, cerebellum Diencephalon

Question 3

What frontal cortex used for?

Answer 3

Thinking, planning, executive function, motor execution

Question 4

What is temporal cortex used for?

Answer 4

Language function, auditory perception, long term memory and emotion

Question 5

What parietal cortex used for?

Answer 5

somatosensory perception,
integration of visual &
somatospatial information

Question 6

What occipital cortex used for?

Answer 6

visual perception

and processing

Question 7

brainstem, cerebellum Diencephalon cortex used for?

Answer 7

Basic life support
Motor coordination
Arousal and attention

Question 8

Describe difference between white greay matter?

Answer 8

White Matter, -> inside brain, cell axons

Grey matter -> on the outside, cell bodies

Question 9

Describe hemisphere crossover?

Answer 9

touching and sensing from one side of body is processed by other side in brain

Each hemisphere sends
motor commands to the
contralateral body side via
descending cross over of
axons in brainstem
– Output is via corticospinal tract
• Each hemisphere receives
sensory information from the
contralateral body side via
ascending cross over of
axons in brainstem
– Input is via thalamus

Question 10

Describe frontal lobe functions? specifically prefrontal cortex

Answer 10

Prefrontal cortex areas involved in
“executive” control of anticipation,
planning, prediction, working
memory, olfactory input
• Primary motor cortex area in
precentral gyrus controls motor
activity of limbs and speech (motor
homunculus) on contralateral side

• Broca’s area for speech production

Question 11

Describe parietal lobe functions?

Answer 11

Primary somatosensory
cortex area in postcentral
gyrus maps skin and
muscle receptors of body
(sensory homunculus) of
contralateral side

Somatosensory
association cortex
integrates sensory map to
produce understanding of
recognition of objects1

Question 12

Describe temporal lobe functions?

Answer 12

Auditory and language functions,
long term memory storage and recall
Primary auditory cortex receives
auditory information
• Auditory association cortex
processes sound recognition
• Language areas (Wernicke’s
area) process language/speech
recognition, integrating with
vision for reading
• Medial temporal lobe is
input/output for hippocampus and site of storage of long term memory – damage causes retrograde amnesia of varying severity
• Olfactory processing

Question 13

Describe occpital lobe functions?

Answer 13

Visual processing and recognition. 
Primary visual cortex (at
back tip of cortex)
receives visual inputs and
forms retinal map
• Visual association area
surrounds primary visual
cortex and interprets
visual input for recognition
and location of visual
objects

Question 14

Describe cortex layer structure?

Answer 14

6 layers, arranged
parallel to surface

Layer based on cellular
types and structures
present, synaptic inputs
and outputs
• Some layers are missing
or more complex in
different cortical areas
>Layes based on cellular tyoes n strcture, and synaptic inputs or outputs

> Some layers missingor more complex in different cortical areas

1) Molevulr layer: mainly axons, input
2) External granular layer
3) Eternal pyramnindal layer
4) Internal granular input as well
5) Internal pyramidal main output cells
6) Multiform -> main output cells

Question 15

Describe vertical columns?

Answer 15

Respond similarly to specific snesory input
Links specific set of inputs to outputs in microcolumn
all species of mammals have these microcolumns

Question 16

Describe The canonical cortex circuit

Answer 16

Processing circuit repeated within columns, similar connections between layers

Sensory input comes from thalamus to excitatory cells in layers 2 3 4
Thalamic inputs to excitatory
neurons in layers 5 and 6 are weak
• Smooth cells are GABAergic s are inhibitory, and project back to layers,

Theres lots of feedbacks

Outputs from 2/3 -> other cortical areas

5/6 to subcortical areas

Question 17

Describe brain structural asymmetry

Answer 17

Right hemisphere goes further
forward
• Left hemisphere goes further back
• Left hemisphere sylvian fissure is
longer and less sloped than right
• Wernicke’
s area in left temporal lobe
adjacent to sylvian fissure is larger
• Neurones in Broca’
s area in left
frontal lobe show more synaptic
connections than in right frontal lobe
• Angular gyrus is larger on left
• Parietal area is larger on righ

Question 18

Describe brain functional asymmetry

Answer 18

Left: linguistic processing,, analytical functions, local features i.e trees
rational language, thoughts, seeing the trees- individual specific features

Right: spatial, facial, music, emotions, whole forest, put it all togethe

Question 19

What happens if you have hemisphere damage? IF THERE CAPITAL M MADE OUT OD Z’S

Answer 19

Right damage, would not see the M just the Zs

Left Damage, would not see the Zs just the big M

Question 20

How is two hemipsheres connected?

Answer 20

Its connected through corpus callosum,
Commissurotomy involves cutting the corpus
callosum and effectively splits the cerebral
hemispheres apart. This operation has been used to
treat epilepsy. Patients show surprisingly little
evidence of perceptual or motor disabilities and have
a relatively normal everyday life.

Question 21

Tell me about Split brain studies?

Answer 21

LANGUAGE PROCESSED IN LEFT HEMISPHERE, CANT NAME A THING THEY SEE ON RIGHT RETINA BUT CAN POINT ON IT IF RIGHT HEM

If you present objects, on right visual field (left hemisphere) it can be recognize and named.

On left retina right hem- cant name

]But can still recognize it.

Suggests left hemisphere is ‘interpreter’ e.g rationalizes

Face recignition, can name half face to left field with high accuracy- PRESENTED to right hemisphere, can see face

But can point

Question 22

What are some other effects of splitting brain?

Answer 22

Difficulty in learning to associate names and faces, eventually
learned by isolating some unique feature of the face to associate
with the name.
• Difficulty with solving geometrical problems. Split-brain patients
show a marked right hemisphere superiority in matching two- and
three-dimensional patterns.
• Aberrant motor behaviour on right and left sides of the body. Rarely,
some patients report uncontrolled or competitive behaviour of right
and left hands.
• Evidence of simple language ability of the right hemisphere. Simple
words presented visually can be associated with pictures.
• Motor tasks that involve coordination of two hands may be poorly
done.

Question 23

Describe Handedness asymmetry?

Answer 23

Left-handed people do not usually have functional
cerebral lateralization which is the “mirror” image of right
handed people
• 70% of left-handers show the same lateralization as right
handers
• 15% do show reversal of usual lateralization pattern
• 15% show bilateral distribution of language and spatial
functions that are usually lateralized

Question 24

Tell me about rodent whiskers

Answer 24

Rats and mice have long
whiskers (vibrissae) arranged in
parallel rows along muzzle
• Large vibrissae are actively
moved (whisking) as animal
explores environment
• Whisking can discriminate object
position with 0.25 mm difference
• Single column of sensory cortex
devoted to processing input from
one vibrissa
• Cortical columns are called
whisker “barrels” due to their
shape in layer IV of sensory
cortex

Question 25

Describe 3 synapse pathway to barrel cortex

Answer 25

``` Each vibrissal follicle innervated by 1-200 sensory mechanoreceptors As it bends, these receptors get triggered, Sensory afferent cell bodies in trigeminal ganglion (in brain stem) and project centrally via trigeminal (Vth) cranial nerve single virissa goies to single barrelette • Barrelette in trigeminal nucleus receives inputs from single vibrissa crosses over • Barrelette output goes to barreloids in contralateral thalamus – main output to ventroposterior medial thalamic nucleus (VPm) – smaller output to posterior medial thalamic nucleus (POm) Output from VPm goes to barrels in cortex layer 4, output from POm goes to septal areas between barrels in cortex, layer 5 and 1 ```

Question 26

Describe different been vpm and pom.

Answer 26

Vpm very narrow and has loop, Pom broad receptive field, strongly regulated by animals, needs to be awake, state, also has loop VPm • Signal information related to narrow receptive field (deflection of a single vibrissa) • Axons terminate in single barrel in layer IV • Minor axon termination in upper layer VI • Corticothalamic layer VI neurons project back to VPm POm • Signal information from broad receptive fields • Activity strongly regulated by state-dependent control from cortex and other areas • Axons terminate in layers 1 and Va, in septal areas between barrels • Corticothalamic layer V neurons project back to Pom

Question 27

Tell me about cortical representation of a single whisker?

Answer 27

``` • Microelectrode recording and intrinsic optical signalling shows that single whisker deflection causes firing and activity localised to single cortical barrel • Voltage-sensitive dye imaging shows that subthreshold activity starts in single barrel but rapidly spreads across barrel cortex ```

Question 28

Tell me about whiskers sensorimotor loop?

Answer 28

``` Rodents rapidly move vibrissae (whisking) to explore objects, sensing object position, shape, texture • Barrel cortex responses to active whisker contact during whisking are much stronger than for passive whisker contact • Whisking occurs at frequencies which enhance synchronous discharge of thalamocortical neurons ``` During whisking response is much stronger, amplification from sensory info from thalamic output. ``` Sensorimotor activation may amplify cortical response to vibrissal contact Trigeminal sensory neurons fire most strongly when vibrissa contacts object B. Voltage-sensitive dye shows barrel activity follows vibrassa contact and spreads rapidly beyond barrel C. Low-level sensorimotor loop between trigeminal nuclei neurons and facial motoneurons may cause acceleration of vibrissa after object contact, amplifying sensory response to higher order areas ```

Question 29

/is imitation inportant?

Answer 29

Yes, especially for infantsm Imitation is important Monkey to monkey Monkey to human • Infant monkeys learn social gestures (lipsmacking) by imitating mother’s gestures • Infant monkeys can also imitate others species (human) facial gestures

Question 30

What are mirror neurons?

Answer 30

Individual cortical neurons active under 2 circumstances , someone performs action – someone observes someone else perform similar action These systems may underlie the capacity to – recognise actions and intentions of others – empathise with or imitate others – may be associated with evolution of language • Disorders of mirror neuron system have been suggested to underlie autistic spectrum disorders

Question 31

Where are these mirror neurons in humans??

Answer 31

``` Recordings of single mirror neuron activity in human brain have now been reported • Functional imaging studies (fMRI and PET) and transcranial magnetic stimulation (TMS) are consistent with mirror neuron system in same functional areas of ventral prefrontal cortex and inferior parietal cortex • Single neurons with activity changes during both action observation and execution were recorded in – medial frontal cortex (supplementary motor area, anterior cingulate cortex) – medial temporal lobe (amygdala, hippocampus, parahippocampal gyrus, entorhinal cortex) • Neuron activity change varied – Increase for both observation and execution – Decrease for both observation and execution – Increase for execution, decrease for observation ```

Question 32

What can children and apes do?>

Answer 32

• Young children and apes can – selectively attend to faces, bodies and actions – understand basic mental states such as goals and perceptions – understand interactions between two objects • They cannot – distinguish between the object of a mental state and the content of a mental state (theory of mind) – Understand interactions between three objects • Humans older than a year develop these abilities

Question 33

Describe The empathic mirror neuron system

Answer 33

``` MNS connected to limbic system via insula • MNS, insula and amygdala are activated in observing or imitating emotional expressions of others • Empathic subjects have – higher levels of activity in MNS areas when viewing motions or hearing sounds – better imitation of emotional expression of others • Subjects experiencing pain or observing situation in which pain was putatively applied to loved one show increased activity in anterior cingulate cortex and anterior insula • Similar activation seen in subjects who are congenitally insensitive to pain (CIP) ```

Question 34

Mirror nuerons and humans?

Answer 34

Actions have to map to motor reportoire of the animal/person, like biting but not narlomg Language->Capacity of MNS for movement imitation, even without obvious purpose (intransitive) ® communicative ability • Anatomical overlap between MNS and language areas suggests that MNS ® language evolution from communicative gestures • Hand and mouth gestures highly linked in humans, both ® activity in left motor cortex hand area • Listening to verbal material (language) vs. non-verbal (pseudowords) increases left motor cortex activity and tongue muscle excitability without speech occurring

Question 35

What is MNS organised into?

Answer 35

two main cortical networks – Ventral premotor cortex and inferior parietal lobule – Insula and anterior cingulate gyrus

Question 36

Specific thalamic nuclei

Answer 36

"corticak switchboard" • Relay specific signals from ascending sensory pathways (vision, hearing, touch) to specific cortical areas arranged in sensory maps

Question 37

– Association thalamic nuclei

Answer 37

• Receives outputs from cortex, limbic nuclei, basal | ganglia and projects to specific cortical areas

Question 38

– Non-specific thalamic nuclei

Answer 38

• Project widely to cortex and other thalamic nuclei

Question 39

Premotor association cortex

Answer 39

controls planning of complex | learned motor patterns

Question 40

• Supplementary motor cortex

Answer 40

controls bilateral motor patterns | requiring dexterity