the thinking brain Flashcards
name the major lobes and list their general function
- frontal lobe:
- thinking
- planning
- central executive functions
- motor function - parietal lobes:
- somatosensory perception
- integration of visual + somatospatial information - temporal lobes:
- language function
- auditory perception
- long-term memory
- emotion - occipital lobe:
- visual perception and processing - orbital lobe/insula:
- regulation of motivation
- seeking pleasure
- avoiding pain - diencephalon, cerebellum, brainstem:
- basic life support
- motor coordination
- arousal and attention
list the detailed functions of the frontal lobe
contains pre-frontal cortex:
- contains highly interconnected areas
- executive control i.e. planning, predicting, organising
- olfactory input
contains pre-central gyrus:
- primary motor cortex
- controls motor activity of limbs and speech on contralateral side
- large area for control of hand movements
contains broca’s area:
- controls speech production
pre-motor association complex:
- rostral to primary motor cortex
- planning and coordinating movements
- particular motor patterns for learned movements
supplementary motor cortex:
- control bilateral motor patterns requiring dexterity
list the detailed functions of the parietal lobe
- sensory integration of touch and proprioception
- spatial discrimination
- primary somatosensory area in post-central gyrus maps skin and muscle receptors (sensory homunculus) of contralateral side –> large areas for upper limb and face
- somatosensory association cortex integrates sensory map to produce understanding and recognition of objects
list the detailed functions of the temporal lobe
- long term memory and recall
- primary auditory cortex receives auditory information
- auditory association complex processes sound recognition
- 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
list the detailed functions of the occipital lobe
- 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 the layered structure of the cortex
CONTAINS PARALLEL LAYERS BASED ON CELLULAR STRUCTURES
- molecular layer:
- mostly axons
- few cell bodies - external granular layer:
- many pyramidal shaped cell bodies
- not many axons - external pyramidal layer
- many pyramidal shaped cell bodies
- not many axons - internal granular layer:
- not as many cells
- intense synaptic inputs from other areas incl. thalamus
- “input layer” - external pyramidal layer
- large number of pyramidal cells and axons
- axons making outputs
- “output layer” - multiform layer
- many cell bodies
- not as many pyramidal cells
- larger number of output layers
- “output layer”
CONTAINS VERTICAL LAYERS ORGANISED BY FUNCTION
- arranged into cortical columns, complex processing and distributing units that link inputs to outputs via overlapping internal processing chains
- species-dependent increase in cortical surface area = more columns, not bigger columns
list and describe the 3 separate roles of the thalamus
- specific thalamic nuclei
- 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
describe the “canonical” cortex circuit
“canonical” cortex circuit = similar synaptic connection patterns between layers in column are repeated throughout cortex
- all sensory input to neocortex comes from thalamus
- thalamic inputs to excitatory neurones in layers 2, 3 and 4 are strong
- thalamic inputs to excitatory neurons in layers 5 and 6 are weak
smooth cells (few dendritic spines) contain GABAergic inhibitory interneurons —> always inhibiting excitatory neurones in all layers
- outputs from layers 2/3 project to other cortical areas
- outputs from layers 5/6 project to subcortical areas
*draw diagram
describe the structural asymmetry between the hemispheres
the left and right hemispheres are not exactly mirrored along the longitudinal fissure
- right hemisphere goes further forward
- 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 right
describe the functional asymmetry between the hemispheres
LEFT DOMINANT FOR:
- linguistic processing
- sequential analytic functions
- recognition of local features
- visually devoted to fine details
- “rational side”
RIGHT DOMINANT FOR:
- spatial processing
- facial recognition
- non-verbal sound recognition and processing (music)
- emotional perception and processing
- parallel integrative functions
- recognition of global features
- visually devoted to general surroundings
commissurotomy
describe the effects
- severing the corpus callosum to split the two hemispheres
- used to treat epilepsy
- little sensory or motor deficits
effects include:
- difficulty in facial recognition
- difficulty with solving geometrical problems
- aberrant motor behaviour on right and left sides of the body (rarely, some patients report uncontrolled/competitive behaviour of right and left hands)
- poor coordination in motor tasks involving both hands
- develop simple language ability in right hemisphere
describe the function of facial recognition in patients who have undergone commissurotomy
- face recognition is lateralized to the right hemisphere
- split-brain subjects shown chimeric face pictures
- unable to name the half-face in the right visual field (left hemisphere), but can point to picture
- can name half-face in the left visual field (right hemisphere) with high accuracy
- split-brain patients compensate by isolating some unique feature of the face to associate with the name (recognising small details via left hemisphere)
describe sexual asymmetry of the brain
FEMALES:
• verbal and spatial abilities may be less lateralized
• anatomical asymmetry less
• perform better at linguistic processing (verbal fluency, speed of articulation, grammar)
• perform better at tests of perceptual speed (matching objects rapidly, recognising displaced objects)
• perform better at precision manual tasks
• perform better at mathematical calculation
MALES:
• verbal and spatial abilities may be more lateralized
• anatomical asymmetry greater
• perform better at spatial processing (maze performance, picture assembly, mental rotation, block design, mechanical skills)
• perform better at mathematical reasoning
• perform better at throwing or intercepting projectiles
• perform better at map reading and finding their way through a route
describe the structure and function of the rodent barrel cortex
vibrissa = whisker
PMBSF = pre-motor barrel sub-field = larger vibrissae = actively whisked to explore environment
ALBSF = anterolateral barrel sub-field = smaller vibrissae = passive (respond to environment but not actively whisked)
single column of sensory cortex devoted to processing input from one vibrissa
cortical columns are called “barrels”
info that arises from mechanoreceptors (200/whisker) projects into CNS via trigeminal (V) cranial nerve
trigeminal nucleus (found in brainstem) contains small group of neurones that respond to sensory info from one vibrissa. organised into barrelette
barrelette sends output, corsses over midline to barreloids in the contralateral thalamus, specifically the ventroposterior medial thalamic nucleus (VPm). smaller output goes to posterior medial thalamic nucleus (POm).
VPm output —> cortex
POm output —> areas between barrels in cortex / different layers
contrast the ventroposterior medial thalamic nucleus (VPm) and the posterior medial thalamic nucleus (POm) regarding their functions and connections
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 I and V, in septal areas between barrels
• corticothalamic layer V neurons project back to POm
