1. How Do We Know How the Brain Works?: 6 Essential Pathways
UW Bio Unit I Lecture 3b
How Do We Know How the Brain Works?:
6 Essential Pathways

2. Processing Information… generally speaking
Input Layer= sensory stimuli coming in
Stimuli received by sensory neurons
Sensory organs eye, ear, skin, taste, touch, pressure, pain, etc.
Hidden Layer= Mid-Brain esp. the Thalamus
Direct sensory stimuli to proper neural circuit
May direct to specific region in brain ex>occipital lobe for visual processing
May direct to motor neurons
Output= expressed as response to incoming stimuli
Motion-voluntary or involuntary
Thought Speech, Memory, etc.

3. Learning Pathway Hippocampus Structures Involved: Function: Pathway:
Hippocampus, thalamus, frontal cortex, senses
Function:
Converting short term memory to long term memory
Short term memory needs the hippocampus to be converted to long term memory
Short term is electrical/ chemical.
Long term is anatomical change.
Long term memory requires >24 hours to form – cramming doesn’t work.
Pathway:
Sensory info thalamus short term memory
Short term memories hippocampus frontal cortex
HM aka Henry Moliason
Hippocampus

4. Sensory Pathway
Each sense organ starts the circuit of sensory information that ends up in the cerebral cortex.
Ear, eyes, taste buds, olfactory bulbs, skin, etc.
Different parts of the cortex receive different information
Sensory cortex processes sensory information
Motor cortex processes conscious, coordinated movement

5. Sensory Pathway Structures Involved: Function: Pathway:
Sensory Organs(Ears, eyes, taste buds, olfactory bulbs, skin, pain receptors), thalamus and the sensory cortex
Function:
Receive and process sensory information (stimuli) and respond appropriately.
Form a visual image
Move hand away from hot object
Pathway:
Sensory organ thalamus appropriate portion of the sensory cortex
Homunculus of
Sensory Cortex

6. Limbic Pathway Structures Involved: Functions: Pathway:
Hypothalamus, Hippocampus, Amygdala, Thalamus, Cerebrum
Functions:
Involved in regulating emotional state and instinctive behavior
Pathway:
Sensory Stimuli Thalamus Cerebral Cortex
Hippocampus & Amygdala direct conversation between the thalamus and cerebral cortex
Phineas Gage

7. Reticular Pathway + - Structures Involved: Function: Pathway:
Reticular Formation (RF) & Reticular Activating System (RAS) - controls arousal and alertness, brainstem, hypothalamus, thalamus, cerebrum
Function:
controlling arousal and alertness
RF also involved in sensory processing, regulating sleepfullness when stimuli present , screening which stimuli are worthy of interrupting sleep
Pathway:
brain stem  hypothalamus and thalamus  cerebrum
Von Economo’s encephalitis:
Lesions in RAS cause only arousal to eat and drink; sleep 20 hrs/day + -

8. Reward Pathway Brain Mechanisms of Pleasure and Addiction

9. Reward Pathway Structures Involved: Midbrain to Cerebrum Function:
VTA , Nucleus Accumbens, prefrontal cortex
Function:
Positive reinforcement for behaviors necessary for survival
Pathway:
Stimuli VTA stimulated NA releases dopamine to prefrontal cortex  repeat behavior
Midbrain to Cerebrum
“mesolimbic area”
Pleasure center. Dopamine released here –Signals “do it again” message to cerebrum
Ventral Tegmental Area= Makes dopamine when stimulated