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

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.

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

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

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

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

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 + -

Reward Pathway Brain Mechanisms of Pleasure and Addiction http://youtu.be/de_b7k9kQp0

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