Agonists, Antagonists, SSRIs, Tolerance & Dependence

Drugs: Agonists and Antagonists

• Agonists increase neurotransmitter activity, such as activating postsynaptic receptors.
• Antagonists decrease neurotransmitter activity, for example, by blocking postsynaptic receptors.

SSRIs: Selective Serotonin Reuptake Inhibitors

• SSRIs are antidepressants that elevate serotonin levels in the brain.

Tolerance, Withdrawal, and Dependence

• Tolerance: Repeated exposure to a drug reduces its effect, requiring larger doses for the same effect.
• Withdrawal: Physical pain occurs when a drug is absent.
• Dependence: Compulsive craving or psychological need to use a drug.

Alcohol Use Disorder: Diagnostic Criteria

• A problematic pattern of alcohol use leads to significant impairment/distress, with at least two of the following:
  • Alcohol is taken in larger amounts or for longer than intended.
  • Persistent desire or unsuccessful efforts to reduce or control alcohol use.
  • Significant time is spent obtaining, using, or recovering from alcohol's effects.
  • Recurrent use results in failure to fulfill major obligations at work, school, or home.
  • Recurrent use in physically hazardous situations.
  • Continued use despite knowledge of physical or psychological problems caused or worsened by alcohol.

Reward Pathway: Brain Areas and Neurotransmitter

• The reward pathway signals a rewarding experience, motivating repeated behavior.
• Dopamine is the major neurotransmitter.
• Key brain areas:
  • Ventral tegmental area (VTA): Source of dopamine neurons projecting to the nucleus accumbens.
  • Nucleus accumbens (NAc): Primary target for dopamine release, triggering pleasure and motivation.
• Repeated drug use reduces dopamine receptors in the brain’s reward system.

Drug Classifications and Examples

• Depressants: Reduce neural activity and slow body functions.
  • Alcohol
  • Anxiolytics (Valium, Xanax, Ativan, Klonopin)
  • Sedatives: Reduce anxiety.
  • Hypnotics: Induce sleep (Ambien, Lunesta, Quaaludes)
  • Opiates/Opioids: Depress neural activity, relieve pain, and produce euphoria (opium, morphine, heroin, methadone, codeine, hydrocodone, oxycodone, dilaudid, fentanyl).
• Stimulants: Excite neural activity and speed body functions.
  • Amphetamines/Methamphetamines: Heighten energy/mood, trigger dopamine release, cause severe withdrawal.
  • Cocaine: From coca shrub, causes alertness/energy/agitation/elevated mood.
    • Blocks reuptake of dopamine, norepinephrine, and serotonin.
• Psychedelics: Distort perceptions, alter mood and thinking.
  • LSD, mescaline, DMT, psilocybin.
  • Act on serotonin receptors as an agonist.
  • Does not affect reward pathway.
• Ecstasy/Molly/MDMA: Synthetic stimulant that increases dopamine and quickly elevates serotonin levels.
  • Causes heightened physiological arousal, hallucinations, euphoria, and oxytocin release.

Drug Effects on Neurotransmitters

• Alcohol: GABA agonist and Glutamate Antagonist (indirectly dopamine agonist).
• Anxiolytics/Sedatives/Hypnotics: GABA agonists.
• Opioids: endorphin/dopamine agonist.
• Amphetamines/Methamphetamines: DA/NE agonist.

Overdose Deaths in the USA

• Opioids and Stimulants cause the most overdose deaths.

Brain: Nervous System Divisions

• Sympathetic Nervous System: arousal and stress.
• Parasympathetic Nervous System: return to rest.

Neural Tube

• The neural tube contains neural stem cells and can grow into the hindbrain, midbrain, and forebrain.

Neurogenesis and Synaptogenesis

• Neurogenesis: The creation of new neurons in the brain, vital in embryonic development and continues through life
• Synaptogenesis: The formation of connections between neurons

Pons and Medulla Functions

• Pons: Regulates breathing, swallowing, salivating, coordinates motor balance, and receives sensory input (pain/audio).
• Medulla: Controls heart rate, BP, breathing, and reflexes (vomit/sneeze/cough).

Cerebellum Function

• Coordinates and fine-tunes motor activity.
• Involved in procedural/muscle memory.

Limbic System: Components and Function

• Involved in emotional processing and memory function.
• Adapts and responds to information, includes Thalamus, hypothalamus, hippocampus, amygdala, anterior cingulate cortex

Key Brain Structures and Their Functions

• Thalamus: Central router; receives most sensory info (sends to cortex), attention control, and basic consciousness.
• Hypothalamus: Helps control the endocrine system, regulates hormones including stress hormones, specializes in sleep cycles.
• Pituitary: Helps hypothalamus regulate the endocrine system.
• Hippocampus: Encodes long-term memory, distributes messages (doesn’t store ALL info), helps remember A to B, neurogenesis.
• Amygdala: Processes emotion and motivational states, controls "fight/flight", can be activated without visuals.
• Anterior Cingulate Cortex (ACC): Connects limbic and prefrontal cortex, controls emotions and optimizes behavioral response.

Cerebral Cortex

• The outer surface of the brain consisting of primary cortex and association cortex

Primary vs. Association Cortex

• Primary: Directly receives sensory information and sends motor commands.
• Association: integrates information from various primary sensory areas to perform complex cognitive functions like perception, memory, and planning.

Lobes of the Brain and Their Functions

• Occipital: visual processing.
• Temporal: hearing processing.
• Parietal: touch processing.
• Frontal: planning, reasoning, thinking (IQ).

Primary Motor Cortex

• Located in the posterior region frontal lobe.
• Controls voluntary movement.

Primary Somatosensory Cortex

• Located in the postcentral gyrus of the parietal lobe.
• Processes sensory information from the body (touch, pain, temp).

Contralateral Control

• The left side of the brain controls the right side of the body and vice versa.

Brain Plasticity and Phantom Limb Sensations

• After amputation, the brain areas responsible for the missing limb get taken over by neighboring regions, leading to sensations from a limb that is no longer there.

Retina: Sensory Neuron Layers

• Retina: sensory processing
• The three layers are:
  • Photoreceptors (rods/cones)- receive light,
  • Bipolar cells-transfer to the ganglion cells
  • Ganglion cells-send general info into photoreceptor for further processing

Rods and Cones

• Rods: Located in the periphery, function in dim light, peripheral and twilight vision
• Cones: Located in the center of retina (Fovea), function in bright light, color and clarity

Optic Chiasm

• Where the two optic nerves meet before going to each hemisphere of the brain
• Information is then routed to the thalamus, then sent to the primary visual cortex
• Contralateral processing

Feature Detectors

• Found in the primary visual cortex
• Neurons fire in response to stimuli (shape/angle/movement)

Dorsal and Ventral Visual Streams

• Dorsal: occipital to parietal lobe processes location and motion ("Where")
• Ventral: occipital to temporal lobe processes features and identity ("What")

Facial Recognition

• Controlled by the occipital and fusiform gyrus

Prosopagnosia

• The inability to recognize and distinguish faces

Top-Down Processing

• Processing that is guided by previous experiences, knowledge, expectations and assumptions

Inattentional Blindness

• Paying attention to one thing, therefore blinding the user to other details
• Example of the gorilla hidden in the basketball video

Cochlea

• Coiled, fluid-filled tube in the inner ear lined with sensory neurons

Hair Cells in the Inner Ear

• Transform sound waves into auditory signals

Flavor Perception

• Gustatory system: taste buds transmit taste to gustatory cells
• Layers: bitter, salty, sweet, sour, umami

Synesthesia

• When one sense automatically triggers another
• Seeing colors when listening to music or seeing numbers

Nociceptors

• Nociceptors: pain perception
  • A-delta fibers: fast-acting, myelinated axons transmit sharp, shooting, localized pain sensations
  • C Fibers: slow-acting, unmyelinated transmit long lasting, duller aching pain sensations

Pain Perception in the Brain

• Processed through the thalamus, cerebral cortex, and limbic system
• Nociceptors release chemicals that signal pain to the brain

Empathy for Pain

• Seeing another person in physical pain triggers the same neural circuits involved in experiencing pain firsthand.

Social Pain

• There is a neural overlap between social rejection and physical pain

Key Figures in Learning

• Pavlov: Classical conditioning
• Watson: Classical conditioning
• Skinner: Operant conditioning.

Classical Conditioning

• When we learn that a stimulus predicts another stimulus

Classical Conditioning: Components

• Unconditioned Stimulus (US): triggers automatic, unlearned natural response (bell)
• Unconditioned Response (UR): unlearned, natural response (salivating)
• Conditioned Stimulus (CS): A neutral stimulus paired with an US triggers a specific response.
• Conditioned Response (CR): A learned behavior occurring in response to a neutral stimulus.

Generalization and Extinction

• Generalization: Stimuli similar to the CS elicit similar responses.
• Extinction: When the US isn't paired with the CS, the CR decreases over time.

Little Albert Experiment

• John Watson's experiment applied classical conditioning to humans
• 9-month old boy (little albert) was conditioned to fear rats

Systematic Desensitization

• A behavioral technique that is effective for treating phobias

Operant Conditioning

• When we learn that a behavior leads to a certain outcome

Reinforcement: Positive and Negative

• Positive Reinforcement: Adds a desirable stimulus (receiving a hug/paycheck).
• Negative Reinforcement: Removes an aversive stimulus (fastening a seatbelt to turn off beeping)

Partial Reinforcement Schedules

• Reinforces a response only part of the time
• Results in slower acquisition but greater resistance to extinction.
  • Fixed Ratio: Reinforces a response after a specified number of responses (piecework pay).
  • Variable Ratio: Reinforces a response after an unpredictable number of responses (gambling).
  • Fixed Interval: Reinforces a response only after a specified time has elapsed (biweekly paycheck).
  • Variable Interval: Reinforces a response at unpredicted time intervals (awarding prizes randomly).

Superstitious Behaviors

• Random reinforcement can lead to false associations, thus superstition.
• B.F. Skinner

Shaping

• Reinforcers guide behavior towards the desired target behavior through successive approximations (teaching a dog tricks).

Punishment Types

• A consequence that decreases the likelihood of a behavior occurring again
• Positive Punishment: Administer an aversive stimulus (spanking).
• Negative Punishment: Withdraw a desirable stimulus (time-out from privileges).

Operant Conditioning in Parenting

• By consistently giving praise/rewards for behaviours while also using clear consequences (time-outs, removal of privileges) for undesirable behaviors

Bandura’s Bobo Doll Study

• Children can learn aggressive behaviors through observation and imitation of adult models.

Three-Stage Model of Memory

• Sensory Input > Processed/Working > Long-Term (Encoded)

Automatic Encoding

• Unconscious memorization that requires very little effort
• Time, space, frequency, and the basic meaning of words

Effortful Encoding Rehearsal

• Rehearsal and memorization

Working Memory

• Active processing, new/old info, association, problem-solving.
• Can typically hold up to 7+/- 2 chunks of information

Hermann Ebbinghaus

• Created the concepts repetition, rehearsal, and retention

Retention Curve

• A graphical representation of how much information a person remembers over time
• Ebbinghaus found that more rehearsal on Day 1 makes rehearsal on Day 2 easier

Serial Position Effect

• Remembering the first and last items on a list
• Primary effect (first), recency effect (last)

Spacing Effect vs. Massed Practice

• SE: Rehearsal and distributed overtime-better for long term
• MP: “cramming”-better for short term, worse for long term

Effective Memory Enhancement

• Active encoding; written notes.
• Retrieval and spaced practice
• Find ways to make material meaningful
• Visual encoding/ dual coding

Daniel Tammet

• Memory savant recited a large number of digits of pi.
• Had Asperger's, high attention to detail and synesthesia

Explicit Memory Brain Region

• Explicit memory (semantic vs. episodic)
  • Semantic=facts and knowledge memory
  • Episodic=personally experienced events
• Hippocampus- stored through cortex

Implicit Memory Regions

• Implicit memory location
• Processed by cerebellum and basal ganglia

Implicit and Explicit Memory Examples

• Procedural: complex motor practice via repetition
• Conditioned Associations: Via classical and operant conditioning

Patient H.M.

• Suffered from epileptic seizures
• Had his temporal lobe removed to help with seizure (including hippocampus).
• Can easily remember pre-surgery memories, but suffers from anterograde Amnesia
• Anterograde Amnesia: can’t encode new information

False Memories

• Can be “planted”, by imagining non-existent events
• Imagining uses similar brain parts as memory retrieval

Misinformation Effect

• Adding misleading information into the memory of an event
• Loftus's car crash experiment demonstrates this

Childhood Amnesia

• Inability to remember stuff before 3 years

Eyewitness Memory Accuracy

• Intense emotion can affect memory association