brain-structure

Brain Strucutre

• Related
  • nervous-system
  • lateralization

Brain Matter

• We have the largest Brain-Body Ratio!
  • 2% of total body weight
  • Consumes 25% of the oxygen
  • Consumes 70% of the glucose
  • Consumes 25% of the nutrients
• 100% of brain is used!

• White matter
  • Gives structure
  • Delivers nutrients
  • Provides communication
• Grey matter
  • Computations happen here
  • The fissures exist to fit as much as grey matter into the skull (increase surface area)

• Neurons
• Synaptic - excitatory/inhibitory signal

• Feelings are processed distributed, e.g. pain
• Neural network is very tolerant to noise, as long as there are enough neurons sending activation signals.

Subcortical Regions

AKA “reptilian brain”, we share this structure with reptiles.

• Medulla - heart rate and blood pressure, basic house keeping
• Pons - regulates sleep cycle and alertness
• Midbrain - sex and aggression

• Cerebellum - regulates the smooth movement

• Corpus callosum - major connection between the two spheres
• Amygdala - our “spider sense”, constantly looks for danger, the brain structure that flips the “switch” for fight or flight response
• Hippocampus - episodic memory, also memorizes what just happen right before the danger

Occipital Lobe

• LGN = lateral geniculate nucleus, a hub that prioritizes the sensory signals
• Primary Visual Cortex
  • Taking in the raw input of vision
  • Scotoma is caused if damaged = seeing black spots
• Association Visual Cortex - recognizing the objects and interpretation
• Vision Agnosia - failed to interpret the vision information “The Man Who Mistook His Wife for a Hat”

Temporal Lobe

• laterality = left vs. right

• Left brain - “analytical”
  • Broca area → related to speech. This area is connected to motor strip
  • Wernicke area → related to comprehension of speech
• Right brain - “creative”
  • Tonal structure, pitch pattern, pitch interval, and timbre

Parietal Lobe

• Motor cortex - movement
• Somatosensory cortex - somatic sensation
• ==Contralateral Wiring== - Left part of body processed in the right hemisphere, and vice versa
• “Cortical Homunculus” created by Dr. Wilder Penfield (picture above)

• The area on the brain ⇒ the importance of the body part, not the volume. e.g. no feeling on elbow
• Proprioception - the feeling of our body parts from inside - associated with left brain - “whose leg is this!”
• Unilateral Visual Neglect - when left brain damaged, failed to notice the right, and vice versa.
• Sensory Deprivation experiment - Our brain is hungry for sensory input, if you don’t feed it, it creates its own. (could this be related to meditation?)

Frontal Lobe

• Makes half of the brain, and is the latest part. The shape of skull changed to fit this part.
• The motor strip defines where the frontal lobe starts
• Frontal lobotomy = severing the frontal lobe from the motor strip to suppress aggression (used to be used to treat schizophrenia, bipolar, and epilepsy)
  • Slow thoughts, loss of spontaneity
  • Perseveration Errors = don’t shift the strategy when things change
  • Loss of self-awareness, flat affect, lack of emotion, loss of empathy
  • Deficiency of planning
  • Tendency to confabulate = lying but not deceiving, producing stories (confabulation in hypnosis?)