structures of the brain and cortex, research methods

• Parts of brain

  • Hindbrain: medulla, pons, cerebellum
  • midbrain: colliculi, tegmentum
  • forebrain; limbic system- hippocampus, amygdala
  • cortex; frontal, temporal, central, parietal, occipital

  
• hemispheres

  • cortex (and most of rest of brain) is symmetrical
  • left and right hemispheres
  • most cortical structures exist in both
  • connected by corpus callosum (and other smaller structures)
  • many functions are lateralized
• Hindbrain

  • Medulla oblongata
  • top of spinal cord; thicker
  • contains cranial nerves
  • pons
  • 'bridge'
  • crossover of axons between hemispheres
  • cerebellum
  • contains more neurons than rest of brain
  • control of movement (including shifting attention)

  
• Hypothalamus (blue)

  • regulates hormonal release
  • mostly from pituitary
  • involved in motivation, metabolism, hunger, sleep

  
• Limbic system

  • Hippocampus:
  • involved in memory formation and relating different pieces of information to each other
  • amygdala
  • involved in emotion regulation, memory, strength, decision making, attention
  • cingulate gyrus
  • involved in motivation, learning
  • connects the other parts of the limbic system

  
• The cortex

  • 'folded' part
  • cortex is larger % of brain in mammals
  • divided into hemispheres
  • each side of the body is controlled by the opposite (contralateral) side of brain
  • 'all' the information crosses over

  
• Layers and columns

  • Neurons in the cortex are organized
  • vertically (dorso-vertically) into layers (laminae)
  • different layers have different cell types
  • diff layers have diff connections
  • in most regions there are 6 layers
  • horizontally (fronto-parietally) into columns
  • cells have the same column react to the same stimuli
  • sometimes nearby columns react to similar things (tonotopic arrangement)
• Major subdivisions


  4 lobes:

  • frontal
  • parietal
  • occipital
  • temporal
  • medial temporal lobe

  
• Localized functions

  • somatosensory and motor cortices are adjacent
  • each contains a map of the (contralateral) body
  • primary touch areas are overrepresented
  • slight differences between motor and sensory
  • different strengths of stimulation are represented separately (4 copies)

  
• Plasticity in Cortex

  • the 'maps' are not fixed
  • can recover in case of injury
  • can change as a result of learning
• Parietal lobe

  • somatosensory cortex
  • involved in perception
  • the sense of where the parts of our body are
  • involved in locating and identifying objects
  • involved in the binding of stimuli
  • how do we know that a visual image and a sound are parts of the same object in the world?= binding problem
  • when this goes wrong= senses bleed into each other; synaethesia
• Temporal lobe

  • involved in auditory processing
  • involved in memory and learning
  • involved in language
  • the left temporal lobe (for right-hand people)
• Occipital lobe

  • involved in vision
• Frontal lobe

  • involved in many complex cognitive tasks
  • involved in working memory
  • prefrontal cortex:
  • involved in 'executive function'
  • tying tg info from all over the brain
  • inhibits much of the rest of the brain
  • releases reactions
• General research methods

  • To show B is caused by A
  • show that B follows (correlates with) A
  • correlation does not equal causation
  • compare an experimental group to a control group
  • identical in everything except the feature under study
• Behaviour

  • if the brain creates behaviour then changes in behaviour might relate to changes in the brain
  • lose a hand-> can't play piano
• Taxi drivers' brains

  • compared the hippocampus of taxi drivers with those of 'normal' ppl
  • taxi drivers have a larger posterior hippocampi and smaller anterior hippocampi
  • problems?
  • learning the map-> bigger hippocampus
  • bigger hippocampus-> better cabbie!!!
  • drivers with more experience show a larger effect
• Getting the right control

  • Larger hippocampi could be caused by
  • learning the map of London
  • driving all day
  • being nice to tourists
  • having to deal with other drivers
  • compare taxi drivers with bus drivers
  • also drive all day
  • on a fixed route; no need to plan new routes
  • taxi drivers have bigger posterior hippocampi than bus drivers
• brain damage

  • if the brain creates behaviour, damage to the brain should 'damage' behaviour
  • in humans:
  • damage is usually accidental
  • damage is diff in each case
  • damage is messy, not limited to one brain region
  • people with epilepsy sometimes have intentional damage
  • HM
  • split-brain patients
  • prefrontal lobotomies; also done on criminals
  • intentional, focused, damage can be down in animal
• Split brain patients

  • have corpus callosum cut
  • two hemispheres cannot communicate
  • each half of body functions independently
  • show an image to each visual field, contralateral hand responds
  • can only talk abt images seen in right visual field bc language is on left
• Other methods

  • deactivating the brain; TMS
  • recording from the brain
  • MRI, CAT; structure
  • fMRI, EEG, MEG; function
• Imaging the brain

  • fMRI has
  • excellent spatial resolution (1mm)
  • can be improved with more powerful magnets
  • weak temporal resolutions (2 sec)
  • images take time to acquire
  • blood-flow takes time to change
  • needs control:
  • compare activity before and during task
  • subtract activations form each other
• Thalamus (red)

  • Most sensory info going to the cortex
  • each sensory modality has a dedicated thalamic nucleus
  • functions like "switchboard"
  • involved in combining info from different senses
  • involved in attention regulation
  • cortex sends some signals back
  • some stimuli are processed more