Brain Basics

Gross Brain Anatomy

Forebrain

Midbrain

Hindbrain

(Brainstem = Midbrain + Hindbrain - Cerebellum)

Hindbrain

• Medulla• Pons• Cerebellum

Medulla Oblongata• caudal end of brainstem; rostral end (towards the face) of spinal cord

• connects rest of brain to spinal cord (lots of myelinated tracts)

• life support functions (heart rate, respiration) – recall connection to the control of blood pH!

• Autonomic nervous control

Pons

• ventral side of cerebellum

• levels of consciousness, sleep,

• arousal, control of autonomic functions,

• sleep, relay info to cerebellum

Cerebellum• coordination of voluntary

movement

• learning motor behaviors

• involved in cognition

• timing of motor output• http://www.youtube.com/watch?v=TCisaP09yFU

Midbrain• rostral end of brainstem: reticular activating system, superior/inferior

colliculi (involved with eye and ear reflexes)

• arousal, wakefulness

• source cells for some important neurotransmitters

Forebrain

• Cerebral Cortex• Thalamus• Hypothalamus• Basal Ganglia• Limbic System

Thalamus

• relays information from diverse areas to cerebral cortex

• integrates sensory information

• regulates sleep-wakefulness

Hypothalamus• homeostatic control (e.g. body

temperature, sex drive, food and water intake)

• regulates autonomic and endocrine systems (via communication with pituitary gland

• Infundibulum connects hypothalamus to pituitary glands

Basal Ganglia• voluntary movement, posture,

routine behaviours (habits), cognitive-emotional functions

• Dopaminergic nerve tracts are lost in this area in Parkinson’s Disease (leads to involuntary movements

Limbic System

• Medial Forebrain Bundle– collection of various nerves

running upstream through midbrain

– involved in reinforcement

• Hippocampus

• Amygdala

• Nucleus Accumbens

Hippocampus• medial side (towards middle) of temporal lobe

• consolidation of short term memory into more permanent memory (memory “builder” but not a “storehouse”)

• recollection of spatial relationships

• http://www.pbs.org/wgbh/nova/body/how-memory-works.html

Amygdala

• inferior medial temporal lobe

• emotional feelings, fear, behavior, perception

Cerebral Cortex

Frontal lobe

Parietal lobe

Occipital lobe

Temporal lobe

Occipital Lobe

• vision

Parietal Lobe

• body sensation (touch, pain, etc.)

• speech reception

• spatial relationships

Temporal Lobe

• hearing

• memory

• emotion

• vision

Frontal Lobe

• planned motor behavior

• speech production

• higher cognition

• social reasoning

BRAIN ON DRUGS?

Nucleus Accumbens

• very important in reinforcement and addiction

• regulation of movement

• cognitive aspects of motor control

Neurons “communicate” with each other using neurotransmitters

Neurotransmitters convey “messages” across the synapse

Dopamine/Opioids: Brain’s incentive reward systems

Activation of reward center produces a “wanting” and “liking” response

Natural events activate these reward systems

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Di Chiara et al., Neuroscience, 1999.

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Fiorino and Phillips, J. Neuroscience, 1997.

Natural Events Elevate Dopamine Levels

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Some drugs activate your reward systems since they act on the same receptors

Drugs make your brain really happy…..

Normal Brain Brain on Drugs

BUT only when your brain is on drugs.

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Di Chiara and Imperato, PNAS, 1988

Effects of Drugs on Dopamine Release

Repeated use of drugs trigger compensatory processes and saturate the brain’s reward systems

individual can become conditioned/habituated/adapted to the intense level of drug-induced pleasure (develops tolerance or sensitization)

the normal level of natural rewards are no longer experienced as very pleasurable, and

after chronic use, the brain’s reward systems becomes so changed that nothing is pleasurable – not even the drugs!

Brain on drugs after tolerance

Brain on drugs for an extended

period

Chronic drug taking ….reorganizes the liking and wanting systems

… drugs may no longer be pleasurable but you still want them…

Drugs can change your brain so that natural events are no longer pleasurable

Normal

Addicted

The brain now has a disease… it’s a different brain under constant stress

When the “switch” gets flips depends on ….

your brain chemistry….

your drug history….

your drug history….

and other factors

Even 80 days following detox, a methamphetamine user’s dopamine transporter system (right) hasn’t

recovered to normal levels (left)

Normal

Cocaine Abuser (10 da)

Cocaine Abuser (100 da)

Cocaine has long lasting effects

At high enough doses, Ecstasy destroys nerve fibers

Mu receptor distribution5HT1a receptor distribution