COncise physiological psychology ch 1

Spatial and Temporal Resolution

  • Spatial Resolution

    • Measures where an event occurs.

    • Refers to the detail, small objects, and spatial precision in an image.

  • Temporal Resolution

    • Measures when an event happens.

    • Ability to track rapid changes over time or how often data is collected, providing time-based accuracy.

Microscopic Techniques for Brain Studies

  • Microscopic Methods

    • Utilize techniques such as histological methods to explore structure, organization, and connection of individual cells.

    • Fragility of brain matter necessitates careful treatment during examination.

Tissue Fixation

  1. Fixation Processes

    • Tissues are fixed by freezing, dehydrating, or treating with formaldehyde (liquid containing gas) to harden tissues.

    • Fixed tissues are then embedded in substances like wax, gelatin, or plastic for easier slicing.

  2. Tissue Slicing

    • Slices are made with a microtome, particularly useful for non-frozen tissue.

    • Typical slice thickness for light microscopy is between 10 and 80 µm, while electron microscopy requires slices less than 1 µm.

  3. Staining Techniques

    • Different stains enhance visibility of structures within nerve tissue, which is transparent under microscopy.

    • Examples of Stains:

      • Goji Stain: Used to visualize a small number of single cells.

      • NISSL Stain: Highlights clusters of cell bodies.

      • Myelin Stain: Stains insulating material covering nerve fibers, showing pathways for information transmission.

      • Horseradish Peroxidase: Identifies where a pathway begins when its endpoint is known, travels backward to the cell body.

      • Immunohistochemistry: Combines antibodies to highlight specific proteins in cells, applicable only to deceased samples.

Non-invasive Methods for Studying Living Organisms

  • Techniques to Study Living Organisms Non-invasively:

    • Fluorescent Microscopy: Uses fluorophores, chemicals that emit light when excited.

    • Photoacoustic Microscopy: Listens to light absorption by different tissue components.

    • Optical Microscopy: Observes neural activity patterns in living subjects in real-time tasks (e.g., mouse drinking water).

Peripheral Methods of Emotional and Attention Analysis

  • Non-invasive methods assessing emotion and attention:

    1. Facial Electromyography (fEMG)

    • Monitors facial muscle movements associated with emotional expressions.

    • Electrodes placed near facial muscles distinguish between positive/negative emotions and measure intensity.

    1. Heart Rate Variability (HRV)

    • Reflects balance between sympathetic and parasympathetic nervous systems.

    • Variance in heartbeats correlates with emotional arousal.

    • Reduced HRV indicates stress and dominance of the sympathetic nervous system.

    1. Skin Conductance Response (SCR) (Galvanic Skin Response or GSR)

    • Measures general arousal via sweat gland activity.

    1. Eye Tracking and Pupil Dilation

    • Eye tracking monitors where the eyes focus and for how long.

    • Pupil dilation reflects arousal, with variations in response to emotional stimuli.

Imaging Technologies for Observing Brain Activity

  • Imaging Technologies allow observation of living brain processes.

    • Examples of Imaging Techniques:

    • Computed Tomography (CT)

      • Developed in 1971, produces high-resolution 3D images using X-rays.

      • Provides structural information but not activity levels.

    • Positron Emission Tomography (PET)

      • Observes brain activity using radioactive tracers mixed with different molecules (oxygen, water, neurochemicals).

      • Focuses solely on brain activity, with no structural detail.

    • Single Photon Emission Computed Tomography (SPECT)

      • More cost-effective but provides less detail than PET.

    • Magnetic Resonance Imaging (MRI) (1977)

      • Takes advantage of differing brain tissue components to generate diagnostic images.

      • Differentiates between:

      • Gray matter: Composed mainly of cell bodies, high in proteins and carbohydrates.

      • White matter: Composed mainly of nerve fibers covered in fat.

      • Cerebrospinal fluid: Composed primarily of saltwater.

    • Functional MRI (fMRI) (1990s)

      • Correlates brain activity with stimuli, emotional states, or tasks in real-time.

      • Measures changes in blood flow, linked to oxygen demands of active neurons, exhibiting the BOLD effect (Blood Oxygen Level Dependent).

      • Active neurons demand more oxygen, detected by variations in blood flow.

Advanced Imaging Techniques

  • Diffusion Tensor Imaging (DTI)

    • Though it uses MRI machinery, it maps brain connectivity by tracking water movement in fiber pathways.

    • Can identify relative neural pathway integrity but not directional information flow.

  • Functional Near-Infrared Spectroscopy (fNIRS)

    • An alternative to fMRI, utilizing near-infrared light.

    • Distinguishes oxygen-rich blood from oxygen-poor blood, offers mobility and reduced costs.

  • Neural Recording Techniques

    • Record brain's electrical and magnetic output, highly useful for understanding brain function.

    • Methods include:

    • Electroencephalogram (EEG) (1924)

      • Records electrical activity via scalp electrodes, useful in various consciousness states.

      • Offers excellent temporal resolution but poor spatial resolution, focusing on surface rather than deeper structures.

      • Identifies patterns of brain activity through Event Related Potentials (ERPs), indicating timing of neuron responses to stimuli.

    • Magnetoencephalography (MEG)

      • Records brain magnetic activity, less hindered by skull interference than EEG.

      • Offers fast temporal resolution and can be used silently in sound-responsive studies.

    • Single Cell Recording (SCR)

      • Allows assessment of individual neurons via microelectrodes, useful in identifying specific neuronal responses (e.g., mirror neurons).

Brain Stimulation Techniques

  • Brain Stimulation Methods

    • Involve artificially stimulating brain areas to observe resulting behaviors.

  • Types of Brain Stimulation:

    • Electro Stimulation

    • Conducted during neurosurgery while patients are conscious, with surrounding tissues anesthetized.

    • Used for conditions such as Parkinson’s, depression, and OCD.

    • Repetitive Transcranial Magnetic Stimulation (rTMS)

    • Non-invasive magnetic stimulation applied to the scalp.

    • Affects brain activity depending on the stimulation area and frequency.

    • Transcranial Electrical Stimulation (tES)

    • Sends weak electrical currents through the skull to modify brain activity.

    • Optogenetics

    • Introduces light-sensitive proteins to specific neurons enabling precise modulation using light.

    • Useful in identifying neural circuit activities related to psychological disorders.

Stereotaxic Surgery and Lesion Studies

  • Stereotaxic Surgery

    • Utilizes a stereotaxic atlas for brain structure positioning.

    • Employs instruments for precise location and orientation of devices.

  • Lesion Studies

    • Investigates neural damage by comparing behavior pre- and post-lesion.

    • Can result from trauma, disease, or experimental means.

    • Example: Paul Broca's work with speech impairment due to brain lesions.

  • Ablation Techniques

    • Involves surgical removal of larger brain areas.

    • Can be performed through heat or chemical methods, leading to permanent brain changes.

Behavioral and Genetic Studies

  • Microdialysis

    • Invasive method collecting extracellular fluids for analysis of active neural chemicals.

  • Functional Magnetic Resonance Spectroscopy (FMRS)

    • Non-invasive, identifies changes in chemical activities tied to cognitive tasks.

  • Genetic Studies in Behavior

    • Examine genetic-environmental interactions and their effect on psychological disorders.

    • Twin Studies: Monozygotic vs. dizygotic comparison in behavioral traits.

    • Adoption Studies: Assesses genetic versus environmental influences.

  • Heritability:

    • Refers to the proportion of trait variation in a population attributed to genetics, influenced by environmental factors.

  • Genome Wide Association Studies (GWAS)

    • Large-scale studies to map genes correlated with specific traits or disorders, identifying genetic links to psychiatric conditions.

  • Reverse Genetic Screening

    • Involves observing phenotypic changes by selectively knocking out genes, examining protein roles in behaviors.

Research Ethics and Guidelines

  • Ethical Considerations:

    • Ensure participants are not coerced into research.

    • Benefits should not be excessive or inappropriate.

    • Ensure informed consent, including conditions for withdrawal without penalty.

    • Provide contact information for participant queries.

    • Guarantee confidentiality of participant data.