Research Methods: Surveys and Observation

Surveys

• Gathering information from a large sample of people using questions
• Goal: Generalize findings from a representative sample to the broader population
• Representative sample: Sample accurately reflects the characteristics of the population
• Random sampling ensures every member of the population has an equal chance of being selected
• Simple random sample: Directly picking a sample from the population using random sampling
• Stratified random sample: Dividing the population into groups and then randomly selecting samples from each group
• Advantages: Affordable, Easy to administer, Can include individuals not typically in research (e.g., homebound, illiterate), Sometimes the only way to gain specific information
• Disadvantages: Accuracy of responses is not guaranteed, Questions can be worded to influence responses, Researcher characteristics can affect outcomes

Naturalistic Observation

• Conducting research in real-world settings
• Researcher must not interfere with the observed behavior
• Advantages: Offers realistic data, Often the only way to gather certain types of information, May lead to unexpected discoveries
• Disadvantages: Similar to surveys with researcher bias, Researcher receives information from both the environment and internal body, Information is analyzed and used to produce behaviors through communication with muscles and glands
• The nervous system creates consciousness and awareness

Neurons

• The basic unit of communication in the nervous system
• Electrochemical communication process
• When a neuron communicates, an action potential (AP) is fired (also known as neural impulse or electrical impulse).
• AP leads to the release of neurotransmitters (NTM), chemicals used for communication between neurons
• Variety of shapes and sizes but similar structures
• Structure:
  • Cell body (soma): Contains the nucleus and DNA, responsible for neuron survival and function
  • Dendrites: Receive messages from other neurons and increase the soma's surface area without taking up much space
  • Axon: Carries the action potential when the neuron fires
  • Axon branches/Axon terminals: Axon branches into multiple terminals
  • Terminal buttons: Small structures at the end of axon branches that release NTMs
  • Myelin sheath: Fatty substance that insulates some axons, speeding up information transmission
  • Synapse: Junction for communication between neurons
  • Synaptic cleft/gap: Tiny space between two neurons at the synapse
  • Presynaptic neuron: Sends out messages
  • Postsynaptic neuron: Receives messages

Glial Cells (Glia)

• Second type of cell in the nervous system
• Billions of them
• Known as "nannies of the neurons" because they:
  • Support neuron development
  • Provide nutrition
  • Insulate neurons
  • Protect neurons
  • Clean waste products
  • Remove dead neurons
• Involved in complex functions like learning, attention, and intelligence
• Linked to brain diseases
• Different types of glia cells perform various functions
  • Oligodendrocytes (CNS) and Schwan cells (outside CNS) produce, lay down, and repair the myelin sheath
  • Microglia: Immune function, play a role in learning and memory, degeneration linked to Alzheimer's disease
  • Astrocytes: Immune function, linked to neurodegenerative diseases

Communication Within a Neuron

• 80% water
• Intracellular fluid: Inside the neuron
• Extracellular fluid: Outside the neuron
• Dissolved chemicals:
  • Na+ Sodium ions
  • Cl- Chloride ions
  • K+ Potassium ions
• These ions are found inside and outside the neuron in different concentrations
• Neuron at rest:
  • Not firing or communicating (no AP)
  • More negative ions inside, making the neuron negatively charged
  • More positive ions outside, making the neuron positively charged
  • -70mV electrical charge (polarized)
• At rest, the neuron receives messages from other neurons:
  • Inhibitory messages:
    • Instruct the neuron not to fire
    • Make the inside of the neuron more negative (hyperpolarized)
    • Neuron less likely to fire
  • Excitatory messages:
    • Instruct the neuron to fire
    • Change ion concentrations
    • Make the inside of the neuron less negative (depolarized)
    • Neuron more likely to fire
• Neuron fires when the electrical charge reaches -50mV (threshold of excitation)
• Detailed ion movements:
  • Inhibitory messages:
    • Chloride (Cl-) channels open
    • Chloride ions move into the neuron (influx)
    • Inside becomes more negative
    • Hyperpolarization
    • Neuron less likely to fire
  • Excitatory messages:
    • Sodium (Na+) channels open
    • Sodium ions move into the neuron (influx)
    • Inside becomes less negative
    • Depolarization
    • Neuron more likely to fire
  • Returning to resting potential:
    • After sodium channels open, potassium (K+) channels open
    • Potassium ions leave the neuron (efflux)
    • Inside becomes less positive
    • Electrical charge reaches -70mV, neuron polarized again (at resting potential)
  • Refractory period:
    • Before reaching resting potential
    • Neuron will not fire if stimulated
    • Membrane hyperpolarized due to excessive potassium leaving the cell
  • Sodium and potassium ion balance:
    • Sodium ions are pumped out, and potassium ions are pumped back in

Communication Between Neurons

• When the presynaptic neuron fires, the action potential travels down the axon to the terminal buttons
• NTMs are released from the terminal buttons and cross the synaptic cleft
• NTMs bind to receptor sites on the postsynaptic neuron, delivering the message
• Each NTM has its own specific receptor site
• Fate of NTMs:
  • Reuptake: NTM detaches from the receptor and is reabsorbed back into the presynaptic neuron for reuse
  • Degradation: NTM detaches and is broken down by enzymes, preventing continued messaging
• Importance of reuptake and degradation:
  • Prevent excessive message relay, ensuring proper nervous system function

Neurotransmitters (NTM)

• Chemicals produced by the brain for communication between neurons
• Some deliver only excitatory messages (e.g., acetylcholine, glutamate)
• Some deliver only inhibitory messages (e.g., GABA)
• Some deliver both excitatory and inhibitory messages (e.g., dopamine, serotonin, norepinephrine, enkephalins/endorphins)
• Maintaining healthy NTM levels is crucial for physical and mental well-being
• Dopamine:
  • Involved in various functions, including:
    • Mood regulation (happiness, good mood)
    • Motivation and goal pursuit
    • Motor function
    • Pleasure derived from life
  • Low dopamine levels are associated with:
    • Depression
    • Lack of motivation
    • Motor problems (Parkinson's disease)
    • Decreased pleasure
  • Dopamine abnormalities are linked to schizophrenia

Drugs and the Brain

• Drugs exert their effects at the synapse
• They interfere with communication between neurons