Chapter Seven

Nonvisual Sensation and Perception

CHAPTER 7NONVISUAL SENSATION AND PERCEPTION

Audition

• Sound as a Physical Stimulus– Intensity

• Amplitude of sound wave• Sound waves vary from quiet whisper to rock band• Logarithmic scale of sound intensity

– Frequency• Number of cycles per unit of time, wavelength of a sound stimulus• Pitch determined by the wave having the lowest frequency

(fundamental frequency)• Timbre, or quality, determined by additional waves • Ultrasound: Frequencies above 20,000 Hz• Infrasound: Frequencies less than 20 Hz

Figure 7.2 The Auditory World Differs Across Species

Table 7.1 Sounds Vary Along the Dimensions of Amplitude, Frequency, and Complexity

Table 7.2 Intensity Levels of Common Sounds

Audition

• The Structure and Function of the Auditory System– The Outer Ear – pinna and auditory canal– The Middle Ear – eardrum, ossicles (malleus, incus,

stapes), tympanic membrane, oval window– The Inner Ear – semicircular canal, cochlea

Figure 7.4 The Anatomy of the Ear

Figure 7.5 The Cochlea

Figure 7.6 Sound Frequencies Are Translated by the Basilar Membrane

Figure 7.7 The Movement of the Cilia Regulates Neurotransmitter Release by Hair Cells

Audition

• The Structure and Function of the Auditory System– Central Auditory Pathways

• Dorsal and ventral cochlear nucleus of the medulla• Superior olive• Inferior colliculus• Medial geniculate nucleus (MGN) of the thalamus

– The Auditory Cortex• Primary auditory cortex – columns respond to single frequencies• Secondary auditory cortex – activated by complex stimuli

Figure 7.8 Auditory Pathways from the Cochlea to the Cortex

Figure 7.9 Tonotopic Organization is Maintained by the Auditory Cortex

Audition

• Auditory Perception– Pitch Perception

• Due to frequency, intensity and context of stimulus• Tonotopic organization

– Loudness Perception• Decibel level describes physical qualities of sound stimulus• Loudness is human perception of that stimulus• Equal loudness contours

– Localization of Sound• Comparison of arrival times of sounds at each ear and differences

in intensities important for horizontal plane• Pinna important for localizing sound in vertical plane

Figure 7.10 Equal Loudness Contours

Figure 7.11 We Localize Sound by Comparing Arrival Times at Both Ears

Hearing Disorders

• Age-related hearing loss– Poor circulation to the inner ear– Effects of exposure to loud noise

• Conduction loss• Loss due to damage to inner ear, auditory

pathways, or auditory cortex

The Body Senses

• Vestibular System– Movement Receptors of the inner ear

• Semicircular canals• Otolith organs: Utricle and Saccule

– Central Pathways• Axons originating in otolith organs and semicircular canals • Ventral posterior (VP) nucleus of the thalamus• Primary somatosensory cortex and primary motor cortex

Figure 7.13 The Vestibular Structures of the Inner Ear

The Body Senses

• Touch– Hairy skin and glabrous skin (hairless)– Layers

• Epidermis• Dermis• Subcutaneous tissue

– Touch Receptors – mechanoreceptors – Touch Pathways

Figure 7.14 Mechanoreceptors of the Skin

Table 7.3 Major Features of the Mechanoreceptors

Figure 7.15 Two-Point Discrimination Thresholds

Figure 7.16 The Four Classes of Sensory Axons Differ in Size and Speed

Figure 7.17 Dermatomes Are Areas of Skin Served by the Dorsal Roots of One Spinal

Segment

Figure 7.19 Somatosensory Information Is Sent to the Ventral Posterior and Intralaminar Nuclei

of the Thalamus

The Body Senses

• Touch– Somatosensory Cortex

• Primary somatosensory cortex found in postcentral gyrus of parietal lobe

• Secondary somatosensory cortex found in posterior parietal lobe

– Plasticity of Touch• Somatosensory cortex rearranges itself in response to changes in

the amount of input it receives

– Somatosensory Disorders

Figure 7.20 Somatosensory Cortex

Figure 7.21 Drawings of a Patient with Neglect Syndrome

The Body Senses

• Temperature– Thermoreceptors

• Cold fibers• Warm fibers

– Share pathways with sense of pain

Figure 7.22 Responses by Cold and Warm Fibers

The Body Senses

• Pain– A Purpose for Pain– Receptors for Pain

• Nociceptors• Chemicals that activate nociceptors

– Pain Pathways to the Brain• Ascending pain fibers (A and C) • Substance P• Substantia gelatinosa, spinothalamic pathway, ventral posterior

(VP) nucleus of the thalamus, anterior cingulate cortex, somatosensory cortex

– Managing Pain

Figure 7.23 Ascending Pain Pathways

Figure 7.24 Descending Messages Influence Pain

Figure 7.26 Olfactory Information Travels from the Epithelium to the Brain

The Chemical Senses

• Taste– Taste Receptors

• Found on tongue and other areas of the mouth• Papilla contain taste buds• Taste buds have 50-150 receptor cells

– Taste Pathways• Taste fibers in tongue form parts of cranial nerves VII, IX, and X• Gustatory nucleus of the medulla• Ventral posterior medial (VPM) nucleus of the thalamus• Gustatory cortex in the parietal lobe• Orbitofrontal cortex in the frontal lobe

Figure 7.27 The Taste Receptors

Figure 7.28 Taste Pathways to the Brain