Lecture 7: Other Sensory Systems PDF

Lecture 7: Other Sensory Systems Auditory and Somatosensory Required readings: Chapter 7  Learning Objectives Name and define the three types of sensory cortex. In the context of sensory system organization, explain what is meant by each of the following terms: hierarchical org...

Lecture 7: Other Sensory Systems Auditory and Somatosensory Required readings: Chapter 7  Learning Objectives Name and define the three types of sensory cortex. In the context of sensory system organization, explain what is meant by each of the following terms: hierarchical organization, functional segregation, and parallel processing. Summarize the current model of sensory system organization. Three Types of Sensory Area of Cortex Primary sensory cortex: receives input directly from thalamus Secondary sensory cortex: receives input from the primary sensory cortex Association sensory cortex: receives input from more than one sensory system Features of Sensory System Organization Hierarchical organization Flow through brain structures in order of increasing anatomical complexity Apparent from a comparison of the effects of damage to various levels Features of Sensory System Organization Hierarchical organization Flow through brain structures in order of increasing anatomical complexity Apparent from a comparison of the effects of damage to various levels Functional segregation Each level, primary, secondary, association levels specialize in different kinds of analysis Parallel processing System is organized so that information flows between structures, simultaneously, along multiple pathways  Former and Current Models of Sensory System Organization once thought to be serial and homogeneous Serial - information flows in just one pathway Figure 7.1 functional homogenous -they all acted together to preform the same function  Learning Objectives Explain the relationship between the physical and perceptual dimensions of sound. Describe the components of the human ear and explain how sound is processed within its various structures. Describe the major pathways that lead from the ear to the primary auditory cortex. Describe the organization of auditory cortex. Describe the effects of damage to the auditory system. Auditory System The function of the auditory system is the perception of sound Sounds are vibrations of air molecules that stimulate the auditory system Physical and Perceptual Dimensions of Sound Related to wavelength Figure 7.2 The relation between the physical and perception dimensions of sound. External Ear Anatomy of the Ear Figure 7.4 Anatomy of the Ear Figure 7.4 Anatomy of the Ear Cross-section of cochlea Figure 7.4 Auditory receptors Figure 7.4 Summary of the anatomy of the ear Outer ear Tympanic membrane (ear drum) Middle ear Ossicles (3 small bones: hammer, anvil, stirrup) Inner ear Oval window Organ of Corti Hair cells of basilar membrane Tectorial membrane Pathway from Ear to Primary Auditory Cortex Hair cells synapse on auditory nerves which project to the metencephalon. Then projections to midbrain structures: inferior colliculi From there to the medial geniculate nucleus (thalamus), and finally the primary auditory cortex Organization of the Auditory Cortex Receives input from medial geniculate nucleus (thalamus) Belt surrounds the primary auditory cortex – secondary auditory cortex Figure 7.6 Most auditory cortex is hidden from view in the temporal cortex of the lateral fissure. Pathway from Ear to Primary Auditory Cortex thalamus midbrain Tonotopic organization Higher pitched Lower pitched Natural sounds optimal for studying auditory cortex Organization of the Association Cortex ▪ Integrates information ▪ Auditory signals are processed by two large areas of association cortex: prefrontal cortex and posterior parietal cortex. ▪ Two streams of auditory cortex Anterior auditory pathway: identifies sound Posterior auditory pathway: identifies where sound is Anterior and Posterior Auditory Pathways posterior prefrontal parietal cortex cortex Identity of Location sounds of sounds Figure 7.7 Organization of the Auditory Cortex Auditory-visual interactions Integral part of sensory processing Occurs in association areas but also in primary areas (recent fMRI studies) Some posterior parietal neurons have visual receptive fields and auditory receptive fields Effects of Damage to the Auditory System Auditory cortex damage Damage to the anterior (“what”) pathway: difficulty identifying sounds Damage to the posterior (“where”) pathway: difficulty localizing sounds Effects of Damage to the Auditory System Deafness in humans Total deafness is rare (1% of hearing-impaired individuals) Two types Conductive deafness (damage to ossicles) Nerve deafness (damage to cochlea or nerve), loss of hair cell receptors Age-related hearing loss: part of the cochlea is damaged, results in a deficit in perceiving high frequencies High frequencies helped by hearing aids or cochlear implant  Hair cell damage Link to article Link to article