Psychology Chapter 7: Sensory Systems

Lecture 7: Other Sensory Systems

• The lecture focuses on auditory and somatosensory systems.
• Required reading is Chapter 7.

Learning Objectives

• Define the three types of sensory cortex.
• Explain hierarchical organization, functional segregation, and parallel processing in the context of sensory system organization.
• Summarize the current model of sensory system organization.

Three Types of Sensory Area of Cortex

• Primary sensory cortex receives input directly from the thalamus.
• Secondary sensory cortex gets input from the primary sensory cortex.
• Association sensory cortex gets input from more than one sensory system.

Features of Sensory System Organization

• Hierarchical organization: Information flows through brain structures in order of increasing complexity. Damage to different levels has specific effects that show this pattern.
• Functional segregation: Different levels of the sensory system (primary, secondary, association) specialize in distinct types of analysis.
• Parallel processing: Information flows simultaneously along multiple pathways between structures.

Former and Current Models of Sensory System Organization

• Older models viewed sensory processing as serial (one pathway) and homogeneous (all parts working together).
• Modern models recognize hierarchical organization but with functional segregation (different areas specialized for different functions) and parallel processing (simultaneous pathways).

Learning Objectives (Auditory System)

• Explain the relationship between physical and perceptual dimensions of sound.
• Describe the parts of the human ear and how sound is processed.
• Detail the pathways from the ear to the primary auditory cortex.
• Describe auditory cortex organization.
• Explain the effects of damage to the auditory system.

Auditory System

• The auditory system detects sound, which is vibrations of air molecules.

Physical and Perceptual Dimensions of Sound

• Amplitude: Related to sound loudness. Higher amplitude = louder sound.
• Frequency: Related to wavelength of sound; perceived as pitch. Higher frequency = higher pitch.
• Complexity: Refers to the mixture of frequencies in a sound; this determines timbre (quality of sound).

Anatomy of the Ear

• Outer ear: The pinna and auditory canal.
• Middle ear: The tympanic membrane (eardrum), ossicles (hammer, anvil, stirrup).
• Inner ear: The oval window, cochlea (fluid-filled structure), hair cells on the basilar membrane, tectorial membrane.

Auditory Receptors

• Hair cells in the cochlea are the receptors for sound.

Pathway from Ear to Primary Auditory Cortex

• Hair cells stimulate auditory nerves.
• Signals project to the metencephalon.
• Then to midbrain structures (inferior colliculi).
• From there to the medial geniculate nucleus (thalamus).
• Finally to the primary auditory cortex.

Organization of the Auditory Cortex

• Receives input from the medial geniculate nucleus (thalamus).
• Primary auditory cortex is surrounded by the belt area (secondary auditory cortex).

Tonotopic Organization

• A way the brain organizes sound frequencies. Areas in the auditory cortex are specialized for different sound frequencies with higher-pitched sounds closer to areas of higher frequency processing in the brain.

Natural sounds optimal for Studying Auditory Cortex

• Using natural sounds is better for studying the auditory cortex because it shows the real complexity of sound.

Organization of the Association Cortex

• Integrates auditory information from prefrontal and posterior parietal cortex.
• Two auditory pathways:
  • Anterior pathway: Identifies sound.
  • Posterior pathway: Locates the source of sound.

Anterior and Posterior Auditory Pathways

• Anterior pathway: In the prefrontal cortex, identifies the sounds
• Posterior pathway: In the posterior parietal cortex, identifies the location of sounds

Auditory-Visual Interactions

• Auditory-visual interactions are important for sensory processing
• Auditory-visual interactions occur in association areas, as well as the primary areas.
• Some neurons in the posterior parietal cortex have receptive fields for both visual and auditory stimuli.

Effects of Damage to the Auditory System

• Auditory cortex damage:
  • Damage to the anterior ("what" pathway) affects sound identification.
  • Damage to the posterior ("where" pathway) affects sound localization.

Deafness in Humans

• Total deafness is rare.
• Conductive deafness: Damage to ossicles.
• Nerve deafness: Damage to the cochlea or nerve, loss of hair cells
• Age-related hearing loss is common- often the hair cells/cochlea are involved.

This quiz covers auditory and somatosensory systems as discussed in Psychology Chapter 7. You'll explore the types of sensory cortex and their roles, as well as principles like hierarchical organization and functional segregation. Prepare to test your understanding of sensory system organization.