Behavioral Neuroscience

Behavioral Neuroscience Notes

Chapter 3: Essential Questions

  • How does my brain work?

Connection Between Brain and Body

  • Central Nervous System (CNS)

    • Composed of the brain and spinal cord.

    • Responsible for processing information and coordinating responses.

  • Peripheral Nervous System (PNS)

    • Carries messages to and from the CNS.

    • Divided into two main components:

    • Autonomic Nervous System: Controls involuntary body functions (e.g., heart rate, digestion).

    • Somatic Nervous System: Controls voluntary muscles and transmits sensory information to the CNS.

  • Autonomic Nervous System

    • Sympathetic Nervous System: Arouses the body to expend energy (fight or flight response).

    • Parasympathetic Nervous System: Calms the body to conserve and maintain energy (rest and digest).

Brain Anatomy and Function

  • How does my brain keep me alive?

    • Divided into three primary regions:

    • Forebrain

      • Contains structures such as the hypothalamus.

    • Midbrain

      • Includes the reticular formation for arousal and consciousness.

    • Hindbrain

      • Houses the medulla which connects to the spinal cord and regulates vital functions.

Sensory Processing

  • How does my brain sense the world around me?

    • Frontal Lobe: Involved in reasoning, planning, and problem-solving.

    • Parietal Lobe: Processes sensory input and spatial orientation.

    • Occipital Lobe: Responsible for visual processing.

    • Temporal Lobe: Information processing related to hearing and memory.

    • Thalamus: Acts as a relay station for sensory information to the cerebral cortex.

    • Primary Somatosensory Cortex: Processes touch and pain sensations.

    • Primary Auditory Cortex: Processes sound information.

    • Primary Visual Cortex: Processes visual data.

Motor Control

  • How does my brain move my body?

    • Cerebellum: Coordinates voluntary movements and maintains posture.

    • Spinal Cord: Conducts signals between the brain and the body.

    • Pons: Connects different parts of the brain and helps regulate sleep and arousal.

    • Substantia Nigra: Critical for movement control; degeneration leads to Parkinson's disease.

Emotion and Memory

  • How does my brain process feelings and memories?

    • Prefrontal Cortex: Critical for decision-making and social behavior.

    • Amygdala: Involved in emotion regulation and fear responses.

    • Hippocampus: Essential for memory formation.

Notable Case Studies

  • Case of H.M.:

    • Underwent bilateral medial temporal lobectomy in 1953 as a treatment for childhood epilepsy.

    • Resulted in severe anterograde amnesia, affecting the ability to form new memories.

  • Case of Phineas Gage:

    • Survived a railroad construction accident in 1848 where an iron rod penetrated his skull.

    • Illustrates the effects of damage to the prefrontal lobe of the cerebral cortex, leading to significant personality changes.

Understanding Brain Function

  • Localization of Function:

    • Observed through cases of amnesia and aphasia which result in behavioral dysfunction.

  • Aphasia: Language impairment categorized into:

    • Broca's Area: Responsible for speech production.

    • Damage leads to non-fluent aphasia.

    • Wernicke's Area: Responsible for language comprehension.

    • Damage leads to fluent but nonsensical speech.

  • Lateralization of Function:

    • Explored via split-brain operations which cut the corpus callosum and studied the effects on cognitive functions.

Neuroanatomy

Structures and Their Functions

  • Neurons: Fundamental units of the brain responsible for processing and transmitting information.

    • Structure:

    • Dendrites: Receive signals from other neurons.

    • Cell Body (Soma): Contains the nucleus.

    • Axon: Transmits signals away from the cell body.

    • Myelin Sheath: Insulates the axon to speed up signal transmission.

    • Axon Terminals: Release neurotransmitters to communicate with other neurons.

Neural Communication

  • Resting Potential: Electric charge inside a neuron at rest is approximately -70 mV due to the distribution of ions (Na+, K+, Cl-, A-).

  • Action Potential: A rapid rise and fall in charge that occurs when a neuron fires, propagating down the axon, characterized by the all-or-none principle.

  • Synaptic Transmission: The process of communication between neurons across the synapse, involving:

    • Synaptic Gap: The space between the presynaptic and postsynaptic neurons.

    • Vesicles: Store neurotransmitters which are released into the synaptic gap.

    • Receptors: Receive neurotransmitters on the postsynaptic neuron and generate postsynaptic potentials.

    • Reuptake: The process of neurotransmitters being taken back into the presynaptic neuron after signaling.

Neurotransmitters and Their Roles

  • Acetylcholine:

    • Functions: Muscle action, attention, learning, memory, sleeping, dreaming.

    • Malfunctions: Found in Alzheimer’s disease—deterioration of acetylcholine producing neurons.

  • Dopamine:

    • Functions: Movement, motivation, pleasure, arousal.

    • Malfunctions: High levels lead to schizophrenia; low levels are linked to Parkinson’s disease.

  • Glutamate:

    • Function: Major excitatory neurotransmitter.

    • Malfunctions: Oversupply can overstimulate the brain, leading to seizures.

  • GABA (Gamma-Aminobutyric Acid):

    • Function: Major inhibitory neurotransmitter.

    • Malfunctions: Undersupply is associated with seizures, anxiety, insomnia.

  • Norepinephrine:

    • Function: Helps control mood and arousal.

    • Malfunctions: Undersupply can lead to mood disorders.

  • Serotonin:

    • Function: Regulates hunger, sleep, arousal, aggressive behavior.

    • Malfunctions: Low levels are linked to depression.

  • Endorphins:

    • Function: Act within pain pathways and emotion centers.

    • Malfunctions: Lack of endorphins lowers the pain threshold and affects the ability to self-soothe.

Effects of Drugs on the Brain

  • Psychoactive Drugs:

    • Increase or decrease neurotransmitter activity:

    • Increase the production of neurotransmitters (e.g., L-DOPA).

    • Block production of neurotransmitters (e.g., AMPT).

    • Deplete neurotransmitters in vesicles (e.g., Reserpine).

    • Block reuptake of neurotransmitters (e.g., Prozac - an SSRI, cocaine).

  • Drug Mechanisms:

    • Bind to postsynaptic receptors and block neurotransmitter binding (e.g., Propranolol, Haldol).

    • Bind to postsynaptic receptors and activate them or increase neurotransmitter effects (e.g., Nicotine).

Common Drugs of Abuse

Stimulants

  • Cocaine:

    • Behavioral Effects: Increases energy and alertness; produces euphoria.

    • Mechanisms of Action: Dopamine reuptake blocker.

  • Amphetamines:

    • Behavioral Effects: Increases energy and alertness; produces euphoria.

    • Mechanisms of Action: Dopamine releaser and reuptake blockers.

  • Nicotine:

    • Behavioral Effects: Increases energy and alertness.

    • Mechanisms of Action: Acetylcholine receptor agonist.

  • Caffeine:

    • Behavioral Effects: Increases energy and alertness.

    • Mechanisms of Action: Adenosine receptor antagonist.

CNS Depressants

  • Alcohol:

    • Behavioral Effects: Produces relaxation; decreases inhibitions; impairs motor function, judgment, and memory.

    • Mechanisms of Action: Increases GABA activity and decreases glutamate activity.

  • Anti-anxiety drugs (Benzodiazepines like Valium and Xanax):

    • Behavioral Effects: Produce relaxation; decreases anxiety; increases sleepiness.

    • Mechanisms of Action: Increase GABA activity.

Opioids

  • OxyContin, Vicodin, morphine, heroin, fentanyl, methadone:

    • Behavioral Effects: Reduce physical and emotional pain; produce feelings of pleasure.

    • Mechanisms of Action: Opioid receptor agonists.

Hallucinogens

  • LSD:

    • Behavioral Effects: Induces sensory distortions and hallucinations.

    • Mechanisms of Action: Serotonin receptor agonist.

  • MDMA (Ecstasy/Molly):

    • Behavioral Effects: Low doses increase arousal; higher doses induce hallucinations.

    • Mechanisms of Action: Dopamine releaser and serotonin releaser at higher doses.

  • Cannabinoids (Marijuana):

    • Behavioral Effects: Alters perception; induces relaxation; affects coordination.

    • Mechanisms of Action: Cannabinoid receptor agonist.

Helpful Links and Videos

  • The Chemistry of Addiction

  • Mouse Party

  • Your Brain on Coffee

  • Crash Course Nervous System