Midterm Study Notes - Physiological Psychology

UNIT 3: BODILY MECHANISMS PHYSIOLOGICAL PSYCHOLOGY MIDTERM NOTES

I. Visual Pathways

General Principle of Perception
  • René Descartes (17th Century): Proposed nerves from the eye send a brain pattern resembling the visual object.
    • Reality: Brain encodes information, which does not look like the actual perceived object (e.g., a triangle's representation in brain).
  • Johannes Müller (1883): Introduced the law of specific nerve energies.
    • Specific nerves correspond to distinct sensations (auditory nerve = sound; olfactory nerve = smell).
Properties of Light
  • Stimulus Input:
    • Light behaves as both a particle (photon) and wave (electromagnetic wave).
  • Wavelength:
    • Related to light region; longer wavelengths correspond to red, shorter to violet.
  • Intensity:
    • Amplitude correlates with brightness; higher amplitude = brighter perception.
  • Brightness and Hue:
    • Not independent; perceived hue depends on brightness.
The Eye
  • Cornea:
    • Exterior surface, involved in light refraction to focus images on the retina.
    • Highly innervated with pain receptors; collects oxygen from the environment.
  • Iris:
    • Colored muscle controlling pupil size, regulating light entry.
  • Pupil:
    • Adjustable opening at eye center; its size regulates light intake.
  • Lens:
    • Transparent structure that changes shape for focusing light on the retina (accommodation).
  • Retina:
    • Light passes through neuronal layers to photoreceptors (rods and cones).
  • Rods: Detect light presence, functioning in low illumination; peripheral vision.
  • Cones: Three types (S, M, L); involved in color vision and detailed perception, mostly found in the fovea.
Neural Processing in Retina and LGN
  • Retina-Geniculate-Striate Pathway:
    • Nasal fibers: contralateral; temporal fibers: ipsilateral.
  • Lateral Inhibition:
    • Neuron excitation reduces neighboring neuron activity; enhances contrast perception (e.g., optic illusion).
Types of Neurons in LGN
  • Parvocellular System (Layers 3-6): Responsive to color and detailed patterns.
  • Magnocellular Neurons: Large cells, respond to movement; do not process color.
  • Koniocellular Neurons: Small cells throughout retina; various functions.
Primary visual cortex (V1)
  • Receives input from LGN, significant for visual perception.
  • Blindsight: Ability to respond to visual stimuli without conscious sight due to damage in V1.

II. Auditory Pathways

Sound and Auditory Perception
  • Physical Definition of Sound: Pressure changes in air or another medium.
  • Perceptual Definition: Experience when hearing sound.
  • Wave Properties:
    • Pure tones as sine waves (amplitude: loudness; frequency: pitch).
  • Decibels: Measurement of sound intensity (dB = 20 log(P/P0)).
The Ear
  • Outer Ear: Pinna, auditory canal, eardrum.
  • Middle Ear: Ossicles (malleus, incus, stapes); transmits sound to oval window.
  • Inner Ear: Cochlea (sound transduction via hair cells), vestibular system (balance).
Central Auditory Processing
  • Pathways leading to auditory cortex; involved in sound localization and pitch discrimination.

III. Vestibular Pathways

Location and Function
  • Located in the inner ear, maintains balance and stabilization of vision during head movement.
  • Two types of movement detected: rotation (angular) and linear acceleration.

IV. Gustatory Pathways

Taste Mechanisms
  • Taste stems from stimulation of taste buds; four basic groups: sweet, salty, sour, bitter (umami as the fifth).
  • Taste receptors are modified skin cells, transmitting information to the brain via different nerves.

V. Somatosensory Pathways

Somatosensation
  • Sensations including touch, pressure, temperature, pain, etc.
  • Receptors: Free nerve endings, Merkel discs, Meissner’s corpuscles, Pacinian corpuscles, Ruffini endings.
  • Pathways: Medial lemniscal pathway for touch; spinothalamic pathway for pain/temperature.
  • Different subareas of the somatosensory cortex respond to distinct body areas; damage can impair body perception.

Key Points:

  • Visual and auditory pathways are critical for perception.
  • The eye and ear have complex structures enhancing sensory capabilities.
  • Both gustatory and somatosensory systems involve specialized receptors that transduce stimuli into neural signals.