Brain and Behavior Exam Notes

Brain & Behavior

Techniques to Study the Brain: Maguire (2000)

• Aim: To analyze the brains of London taxi drivers and determine if there are significant differences compared to non-taxi drivers, attributing these differences to their extensive navigation experience.
• Procedure:
  • 16 male taxi drivers underwent MRI brain scans. These were compared with scans of 50 non-taxi driver males.
  • Participants were required to have a driver's license for at least 1.5 years.
  • MRI data was analyzed using voxel-based morphometry (VBM) and pixel counting.
• Results:
  • Pixel counting showed that taxi drivers had larger posterior hippocampi and smaller anterior hippocampi compared to non-taxi drivers.
  • VBM analysis revealed a correlation between the volume of the right posterior hippocampus and the amount of time spent as a taxi driver.
• Interpretation:
  • The posterior hippocampus is likely involved in using past spatial knowledge.
  • The anterior hippocampus is likely involved in encoding new environmental layouts and driving routes.

Neuroplasticity

• Definition: The nervous system's ability to modify its activity in response to intrinsic or extrinsic stimuli by restructuring neuronal connections.
• Mechanism: Involves changes in the structure and connections between neurons, leading to the formation of new neural pathways.
• Function: Facilitates the brain's adaptation to new experiences and situations, affecting thought structures.
• Impact: Neuroplasticity can be influenced by both physical and mental experiences.
  • Example: Traumatic brain injury from a car accident or even the trauma without physical injury can trigger neuroplasticity.

Brain Structures and Their Functions

Amygdala

• Function: Crucial for recognizing threats, processing emotions, and forming emotionally charged memories.
• Emotional memories: Forms memories strongly associated with emotions (e.g., fear related to car crashes).
• Example: Patient S.M. with a damaged amygdala showed no emotional response to stress-inducing situations.
• Location: Located in the medial temporal lobe, anterior to the hippocampus.
• Specificity: Different parts of the amygdala respond to different emotions.

Hippocampus

• Function: Converts short-term memories into long-term memories.
• Research on neuroplasticity
• Formation of neural networks.
• Example: Maguire's taxi driver experiment showed that taxi drivers had a larger hippocampus (increased brain matter) compared to non-taxi drivers, indicating neuroplasticity due to spatial memory demands.

Nucleus Accumbens

• Function: Interface between motivation and action.
• Processes: Involved in sexual behavior, reward, stress, and addiction-related behaviors.
• Example: Pavlovian learning illustrates how behaviors adapt based on past experiences, mediated by the nucleus accumbens.

Brain Imaging Techniques

Magnetic Resonance Imaging (MRI)

• Method: A medical imaging technique that visualizes the body's anatomy and physiological processes using radio frequencies and magnetic fields.
• Applications: Used in medical procedures and psychological analysis.

The Role of Agonists

• Definition: A chemical that activates a receptor to produce a biological response.
• Mechanism:
  • Mimics the action of a neurotransmitter by binding to a brain receptor and activating it.
  • Inhibits reuptake by blocking neurotransmitters from re-entering the pre-synaptic axon terminal, increasing their time in the synaptic cleft to act on receptors.
• Examples: Dopamine, endorphins, and fentanyl are examples of receptor agonists.

Setiawan (2013) - Alcohol Use Disorder Study

• Aim: To investigate the role of dopamine and the mesolimbic reward pathway in alcohol use disorders (AUD).
• Participants: 26 healthy young social drinkers aged 18-30 (8 females).
  • Exclusion criteria: Diagnosis of mental illness or drug dependence (except nicotine or caffeine).
  • Included 11 participants with family members with AUD.
• Procedure:
  • Participants completed questionnaires to assess risk based on personality and intoxication levels.
  • Participants underwent two PET scans on separate days, after urine and breathalyzer tests confirmed they were drug-free.
  • 30 minutes before each scan, participants consumed either soda or soda with alcohol.
• Results:
  • Participants at "high risk" for alcoholism showed greater activity in the mesolimbic reward pathway (higher dopamine levels) after alcohol consumption.
  • "Low risk" participants showed lower activity.
• Interpretation: Agonists like dopamine trigger receptors that activate the reward system in individuals consuming alcohol. Higher mesolimbic reward pathway activity results from increased dopamine release.

Neurotransmission and its Effect on Behavior: Antonova (2011)

Inhibitory Neurotransmitters

• Function: Block or inhibit chemical messages from being passed along the synapse of neurons.
• Mechanism: Decrease the likelihood of a postsynaptic action potential.
• Application: Used when preventing an individual from having a natural response based on a condition.
• Examples: GABA (Gamma-aminobutyric acid), acetylcholine.

Antonova (2011) - Acetylcholine and Spatial Memory Study

• Aim: To investigate the role of neurotransmitters (specifically acetylcholine) in behavior.
• Participants: 20 healthy male adults (mean age 28 years old).
• Procedure:
  • Double-blind procedure: participants randomly assigned to receive either scopolamine (an acetylcholine antagonist) or a placebo 70-90 minutes before the experiment.
  • Participants underwent fMRI scans while playing a virtual reality game called the "Arena task."
  • Task: Navigate around an "arena" to reach a pole. After reaching the pole, the screen goes blank for 30 seconds, during which participants rehearse how to get to the pole.
  • After rehearsal, participants start from a new point in the arena. The process was repeated for 6 trials; participants repeated the experiment 3-4 weeks later.
• Results: The Scopolamine group demonstrated a significant reduction in hippocampus activation compared to the placebo group.
• Interpretation: Acetylcholine plays a key role in encoding spatial memories. The study demonstrates how inhibitory neurotransmitters function, as acetylcholine reduces activity within the hippocampus, impairing spatial memory formation.

Synapses: Excitatory vs. Inhibitory

• Excitatory Synapses: Make neurons more likely to fire an action potential, promoting neural activity.
• Inhibitory Synapses: Make neurons less likely to fire an action potential, suppressing or regulating neural activity.