thinking brain lecture 1 Flashcards
Describe the human cortex
Large surface area
>1 trillion synapses
Most complex neural stucture in brain
Mediates: – Voluntary motor activity – Sensory perception – Learning and memory – Language – Affective disorders
What are the 5 parts of cortex?
Frontal -
Parietal
Temporal
Occipital
Also brainstem, cerebellum Diencephalon
What frontal cortex used for?
Thinking, planning, executive function, motor execution
What is temporal cortex used for?
Language function, auditory perception, long term memory and emotion
What parietal cortex used for?
somatosensory perception,
integration of visual &
somatospatial information
What occipital cortex used for?
visual perception
and processing
brainstem, cerebellum Diencephalon cortex used for?
Basic life support
Motor coordination
Arousal and attention
Describe difference between white greay matter?
White Matter, -> inside brain, cell axons
Grey matter -> on the outside, cell bodies
Describe hemisphere crossover?
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
Describe frontal lobe functions? specifically prefrontal cortex
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
Describe parietal lobe functions?
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
Describe temporal lobe functions?
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
Describe occpital lobe functions?
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
Describe cortex layer structure?
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
Describe vertical columns?
Respond similarly to specific snesory input
Links specific set of inputs to outputs in microcolumn
all species of mammals have these microcolumns
Describe The canonical cortex circuit
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
Describe brain structural asymmetry
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
Describe brain functional asymmetry
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
What happens if you have hemisphere damage? IF THERE CAPITAL M MADE OUT OD Z’S
Right damage, would not see the M just the Zs
Left Damage, would not see the Zs just the big M
How is two hemipsheres connected?
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.
Tell me about Split brain studies?
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
What are some other effects of splitting brain?
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.
Describe Handedness asymmetry?
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
Tell me about rodent whiskers
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
Describe 3 synapse pathway to barrel cortex
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
Describe different been vpm and pom.
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
Tell me about cortical representation of a single whisker?
• 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
Tell me about whiskers sensorimotor loop?
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
/is imitation inportant?
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
What are mirror neurons?
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
Where are these mirror neurons in humans??
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
What can children and apes do?>
• 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
Describe The empathic mirror neuron system
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)
Mirror nuerons and humans?
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
What is MNS organised into?
two main cortical networks
– Ventral premotor cortex and inferior parietal lobule
– Insula and anterior cingulate gyrus
Specific thalamic nuclei
“corticak switchboard”
• Relay specific signals from ascending sensory
pathways (vision, hearing, touch) to specific cortical
areas arranged in sensory maps
– Association thalamic nuclei
• Receives outputs from cortex, limbic nuclei, basal
ganglia and projects to specific cortical areas
– Non-specific thalamic nuclei
• Project widely to cortex and other thalamic nuclei
Premotor association cortex
controls planning of complex
learned motor patterns
• Supplementary motor cortex
controls bilateral motor patterns
requiring dexterity
