Major Divisions of the Brain

Major Divisions of the Brain

1. Telencephalon

   • -Largest division -Complex functions (purposeful behaviour, language, perception) -Produces and inhibits emotions
   • Cerebral Cortex (Cortical)
     • -Convolutions to +surface area -Longitudinal fissure: separates hemispheres -Corpus callosum: connects hemispheres -Central fissure (horizontal) and Lateral fissure: separate 4 lobes -Gyri: small ridges/protrusions
     • Frontal Lobe
       • -Executive planning -Complex cognition -Motor control -Emotion inhibition
       • Precentral Gyrus (motor strip)
         • -Controls motor movements, speech sounds, etc.
       • Prefrontal Cortical Regions
         • -Complex cognition (planning, evaluating, assessing behav. of others, inhibition of inappropriate behav.) -"Ego" and "Superego" -Damaged by continuous drinking (Korsokoff's syndrome - no inhibition)
     • Occipital Lobe
       • -Vision
       • Visual Cortex
         • -Divided by calcerine sulcus -Very back of brain -Processes visual info
     • Parietal Lobe
       • -Proprioceptive functions (info about position of body relative to environment)
       • Post-Central Gyrus
         • -Analysing sensations from body
     • Temporal Lobe
       • -Emotions (fear and aggression) -Epilepsy
       • Superior Temporal Gyrus
         • -Hearing/auditory perception -Language comprehension
         • Inferior Temporal Gyrus
           • -Complex visual patterns
         • Medial Temporal Gyrus
           • -Encoding certain memories
   • Limbic System (Subcortical)
     • -Motivated behaviours (4 F's)
     • Amygdala
       • -Anterior temporal lobe -Produces emotions (fear & aggression) -Conditioned fear learning & fear expression (damage = inability to express/detect normal fear)
       • Lateral Nuclei
       • Basal Nuclei
       • Central Nuclei
     • Hippocampus
       • -Medial temporal lobe -Transfers short-term memories to declarative & explicit long-term memories (ex/ patient HM not forming new explicit memories after hippocampus removal) -Korsakoff's Syndrome: drinking damages hippocampus and leads to memory problems -Contextual fear learning -Spatial cue memory
     • Fornix
     • Cingulate Cortex
     • Septum
       • -Midline nucleus near cingulate cortex -Fibres connect it to amygdala, hippocampus, & hypothalamus -Aggression, rage, anxiety, stress, Alzheimer's
     • Mammillary Bodies
   • Basal Ganglia (Subcortical)
     • -Modulates motor output -Fine motor control -Planned & purposeful movements -Cognitive functions (Projects to cortical areas)
     • Amygdala
       • -Works with nucleus accumbens to produce motivational behav.
     • Striatum
       • -Caudate + putamen (they appear striped) -Linked to substantia niagra (SN) in a dopamine pathway (deterioration leads to Parkinson's)
       • Putamen
         • -Centre of caudate (connected by fibre bridges)
       • Caudate
         • -C-shaped -includes the putamen
       • Nucleuss Accumbens
         • -Rewarding behaviours (drugs, food, etc) -Receives dopamine input from VTA and amygdala
         • Shell
         • Core
     • Globus Pallidus
       • -Medial to putamen -Pale & circular -Linked to SN in dopamine pathway

2. Mesencephalon

   • Midbrain
   • Tectum
     • -The "roof"
     • Inferior Colliculi
       • -Receives & processes auditory info
     • Superior Colliculi
       • -Processes visual info
   • Tegmentum
     • -Ventral to tectum
     • Periaquiductal Gray (PAG)
       • -Opioid receptors mediate pain -Where morphine binds to; mediates bain via descending pathways -Emotionality & fear expression (circa-strike attacks & aggression, fear-induced defensive freezing)
     • Substantial Niagra (SN)
       • -Important in sensorimotor system -Loss of dopamine-producing neurons leads to Parkinson's
       • Nigro-Striatal Dopamine Pathway
     • Ventral Tegmental Area (VTA)
       • -Projects to cortical & limbic regions -Connects with accumbens to produce rewarding effects & addictive behaviours
       • Mesocortico-limbic Dopamine Pathway
         • -Stress & conditioned stress behavioural responses -Stressor = +dopamine to mPFC = disrupts cognition & planning -Overactive DA pathways may be linked to schizophrenia/paranoid behaviours
     • Reticular Formation (anterior aspects)
     • Red Nucleus
       • -Connects to cerebellum -Descending projections to brain stem & spinal cord -Posture, balance, coordinated movements

3. Myelencephalon (Medulla)

   • -Most posterior division
   • Fibre Tracts
     • -Carry signals btn rest of brain & body
   • Reticular Formation
     • -Comprised of 100 sub-nuclei in core of brainstem -Sleep & attention -Movement -Muscle tone -Reflexes (heartbeat, breathing, etc)

4. Diencephalon

   • Thalamus
     • -Relays sensory info to cortex, limbic system, & basal ganglia (lik a switchboard)
     • Lateral Geniculate Nucleus (LGN)
       • -Relays visual info
     • Medial Geniculate Nucleus (MGN)
       • -Relays auditory info
     • Ventral Posterior Nucleus (VPN)
       • -Relays somatosensory info (touch, pressure, pain, temp)
     • Posterior Intralaminar Nucleus (PIN) and Central Nucleus (CNT)
       • -Relay nociceptive (pain) info to amygdala & parietal cortex
   • Hypothalamus
     • -Regulates motivated behaviours (ex/ brain-stimulation-reward in rats) -Hormone release via pituitary and adrenal glands

5. Metencephalon

   • Brainstem
   • Ascending/Descending Fibre Tracts
   • Pons
     • -Regulates acoustic startle response to loud noises -Heart activity during fear/arousal
   • Cerebellum
     • -Balance & coordination (sensorimotor functions)

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