Prepared by Jeffrey W. Grimm Western Washington University

Name: Prepared by Jeffrey W. Grimm Western Washington University
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Description: Prepared by Jeffrey W. Grimm Western Washington University

Prepared by Jeffrey W. Grimm Western Washington University
PowerPoint Presentation for Biopsychology, 8th Edition by John P.J. Pinel Prepared by Jeffrey W. Grimm Western Washington University This multimedia product and its contents are protected under copyright law. The following are prohibited by law: any public performance or display, including transmission of any image over a network; preparation of any derivative work, including the extraction, in whole or in part, of any images; any rental, lease, or lending of the program. Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved.
Chapter 7: Mechanisms of Perception: Hearing, Touch, Smell, Taste, and Attention How You Know the World Copyright © 2011 Pearson Education, Inc. All rights reserved.

Principles of Sensory System Organization
Primary – input mainly from thalamic relay nuclei For example, striate cortex receives input from the lateral geniculate nucleus Secondary – input mainly from primary and secondary cortex within the sensory system Association – input from more than one sensory system, usually from secondary sensory cortex Copyright © 2011 Pearson Education, Inc. All rights reserved.

Principles of Sensory System Organization Continued
Hierarchical Organization Specificity and complexity increases with each level Sensation – detecting a stimulus Perception – understanding the stimulus Functional Segregation – distinct functional areas within a level Parallel Processing – simultaneous analysis of signals along different pathways Copyright © 2011 Pearson Education, Inc. All rights reserved.

FIGURE 7.2 Two models of sensory system organization: The former model was hierarchical, functionally homogeneous, and serial; the current model, which is more consistent with the evidence, is hierarchical, functionally segregated, and parallel. Copyright © 2011 Pearson Education, Inc. All rights reserved.

Auditory System Natural sounds are complex patterns of vibrations A Fourier analysis breaks natural sounds down into sine waves There is a complex relationship between natural sounds and perceived frequency Copyright © 2011 Pearson Education, Inc. All rights reserved.

The Ear Sound waves enter the auditory canal of the ear and then cause the tympanic membrane (the eardrum) to vibrate This sets in motion the bones of the middle ear, the ossicles, which trigger vibrations of the oval window Copyright © 2011 Pearson Education, Inc. All rights reserved.

The Ear Continued Sound wave > eardrum > ossicles (hammer, anvil, stirrup) > oval window Vibration of the oval window sets in motion the fluid of the cochlea The cochlea’s internal membrane, the organ of Corti, is the auditory receptor organ Copyright © 2011 Pearson Education, Inc. All rights reserved.

The Ear Continued The organ of Corti is composed of two membranes Basilar membrane – auditory receptors, hair cells, are mounted here Tectorial membrane – rests on the hair cells Stimulation of hair cells triggers action potentials in the auditory nerve Copyright © 2011 Pearson Education, Inc. All rights reserved.

The Ear Continued Cochlear coding: Different frequencies produce maximal stimulation of hair cells at different points along the basilar membrane Tonotopic (frequency) organization of the basilar membrane and most other auditory system components Copyright © 2011 Pearson Education, Inc. All rights reserved.

From the Ear to the Primary Auditory Cortex
The axons of each auditory nerve synapse in the ipsilateral cochlear nuclei From there, many projections lead to the superior olives on both sides of the brain stem From there, axons project via the lateral lemniscus to the inferior colliculi Axons then project from the inferior colliculi to the medial geniculate nuclei of the thalamus Thalamic neurons then project to the primary auditory cortex Copyright © 2011 Pearson Education, Inc. All rights reserved.

Subcortical Mechanisms of Sound Localization
The lateral and medial superior olives react to differences in what is heard by the two ears Medial – arrival time differences Lateral – amplitude differences Both project to the superior colliculus The deep layers of the superior colliculus are laid out according to auditory space, allowing location of sound sources in the world; the shallow layers are laid out retinotopically Copyright © 2011 Pearson Education, Inc. All rights reserved.

Auditory Cortex Auditory cortex is located in the temporal lobe Core region: includes primary cortex Belt surrounds the core region A band of secondary cortex Secondary cortex outside the belt referred to as parabelt areas About ten seperate areas of secondary auditory cortex in primates Copyright © 2011 Pearson Education, Inc. All rights reserved.

Organization of Primate Cortex
Functional columns (cells of a column respond to the same frequency) Tonotopic organization Secondary areas do not respond well to pure tones and have not been well-researched Copyright © 2011 Pearson Education, Inc. All rights reserved.

What Sounds Should Be Used to Study Auditory Cortex?
There is a lack of understanding of the dimensions along which auditory cortex evaluates sound All through the cortical levels of the auditory system there are cells that respond to complex sounds Perhaps study with pure tones is limited Copyright © 2011 Pearson Education, Inc. All rights reserved.

Two Streams of Auditory Cortex
Auditory signals are conducted to two areas of association cortex Prefrontal cortex Posterior parietal cortex Anterior auditory pathway may be more involved in identifying sounds (what) Posterior auditory pathway may be more involved in locating sounds (where) Copyright © 2011 Pearson Education, Inc. All rights reserved.

Auditory-Visual Interactions
There is evidence for interactions between the auditory and visual systems e.g. some posterior parietal neurons with both visual and auditory receptive fields Interaction in primary sensory cortices indicate that sensory system interaction is an early and integral part of sensory processing Copyright © 2011 Pearson Education, Inc. All rights reserved.

Where Does the Perception of Pitch Occur?
Most auditory neurons respond to changes in frequency rather than pitch One small area just anterior to primary auditory cortex has neurons that respond to pitch rather than frequency May be where frequencies of sound are converted to perception of pitch Copyright © 2011 Pearson Education, Inc. All rights reserved.

Effects of Damage to the Auditory System
Lesions of auditory cortex in rats results in few permanent hearing deficits Lesions in monkeys and humans hinder sound localization and pitch discrimination Deafness in humans Total deafness is rare, due to multiple pathways Two kinds: conductive deafness (damage to ossicles) and nerve deafness (damage to cochlea) Partial cochlear damage results in loss of hearing at particular frequencies Copyright © 2011 Pearson Education, Inc. All rights reserved.

Somatosensory System: Touch and Pain
` Somatosensory system is three separate and interacting systems: Exteroceptive – external stimuli Proprioceptive – body position Interoceptive – body conditions (e.g., temperature and blood pressure) Copyright © 2011 Pearson Education, Inc. All rights reserved.

Cutaneous Receptors Free nerve endings Temperature and pain Pacinian corpuscles Adapt rapidly, large and deep; onion-like Respond to sudden displacements of the skin Merkel’s disks – gradual skin indentation Ruffini endings – gradual skin stretch Dermatome – the area of the body innervated by the left and right dorsal roots of a given segment of spinal cord Copyright © 2011 Pearson Education, Inc. All rights reserved.

Two Major Somatosensory Pathways
Dorsal-column medial-lemniscus system Mainly touch and proprioception First synapse in the dorsal column nuclei of the medulla Anterolateral system Mainly pain and temperature Synapse upon entering the spinal cord Three tracts – spinothalamic, spinoreticular, spinotectal Copyright © 2011 Pearson Education, Inc. All rights reserved.

Cortical Areas of Somatosensation
Primary somatosensory cortex (SI) Postcentral gyrus Somatotopic organization (somatosensory homunculus) – more sensitive, more cortex Input largely contralateral SII – mainly input from SI Somatotopic; input from both sides of the body Much of the output from SI and SII goes to association cortex in posterior parietal lobe Copyright © 2011 Pearson Education, Inc. All rights reserved.

Effects of Damage to the Primary Somatosensory Cortex
Effects of damage to the primary somatosensory cortex are often mild Likely due to numerous parallel pathways Copyright © 2011 Pearson Education, Inc. All rights reserved.

Somatosensory System and Association Cortex
Highest level of sensory hierarchy are areas of association cortex in prefrontal and posterior parietal cortex Posterior parietal cortex contains bimodal neurons Neurons that respond to activation of two different sensory systems Allow integration of visual and somatosensory input Copyright © 2011 Pearson Education, Inc. All rights reserved.

Somatosensory Agnosias
Astereognosia – inability to recognize objects by touch pure cases are rare – other sensory deficits are usually present Asomatognosia – the failure to recognize parts of one’s own body (the case of the man who fell out of bed) Copyright © 2011 Pearson Education, Inc. All rights reserved.

Perception of Pain Despite its unpleasantness, pain is adaptive and needed No obvious cortical representation of pain (although the anterior cingulate gyrus appears involved in the emotional component of pain) Descending pain control – pain can be suppressed by cognitive and emotional factors Copyright © 2011 Pearson Education, Inc. All rights reserved.

Descending Pain Control
Circuitry identified by the following studies: Electrical stimulation of the periaqueductal gray (PAG) has analgesic effects PAG and other brain areas have opiate receptors Existence of endogenous opiates (natural analgesics) – endorphins Copyright © 2011 Pearson Education, Inc. All rights reserved.

Neuropathic Pain Severe chronic pain in the absence of a recognizable pain stimulus Likely from pathology of nervous system linked to an injury Some evidence for aberrant glial cell signals triggering neural pain pathways Copyright © 2011 Pearson Education, Inc. All rights reserved.

Chemical Senses: Smell and Taste
Olfaction (smell) Detects airborne chemicals Gustation (taste) Responds to chemicals in the mouth Food acts on both systems to produce flavor Copyright © 2011 Pearson Education, Inc. All rights reserved.

Chemical Senses: Smell and Taste
Pheremones are chemicals that influence that behavior of conspecifics (members of the same species) Evidence of human pheromones Changes in olfactory sensitivity across and menstrual cycle Synchronization of menstrual cycles Sex identification by smell (especially by women) Men can identify menstrual stage by smell Copyright © 2011 Pearson Education, Inc. All rights reserved.

Olfactory System Receptor cells embedded in the olfactory mucosa of the nose Many different kinds of receptors Rats and mice have about 1,500 Humans have almost 1,000 Same kinds of receptor cells project to similar areas of the olfactory bulb clusters of neurons near the surface of the olfactory bulbs olfactory glomeruli New receptor cells are created throughout life Copyright © 2011 Pearson Education, Inc. All rights reserved.

Olfactory System Continued
Olfactory tract projects to several structures of the medial temporal lobes including amygdala and piriform cortex does NOT first pass through the thalamus only sensory system that does this Copyright © 2011 Pearson Education, Inc. All rights reserved.

Gustatory System Receptors in tongue and oral cavity in clusters of about 50 called taste buds located around small protuberances called papillae > 4 (sweet, sour, salty, bitter) primary tastes – 5th is umami, meat or savory Many tastes not created by combining primaries Salty and sour don’t have receptors; they merely act on ion channels Copyright © 2011 Pearson Education, Inc. All rights reserved.

Gustatory System Continued
Gustatory afferent neurons leave the mouth as part of the 7th, 9th, and 10th cranial nerves to the solitary nucleus of the medulla Projections then pass to the ventral posterior nucleus of the thalamus From there, neurons project to the primary gustatory cortex and then to the secondary gustatory cortex Copyright © 2011 Pearson Education, Inc. All rights reserved.

Brain Damage and the Chemical Senses
Anosmia – inability to smell Most common cause is a blow to the head that damages olfactory nerves Incomplete deficits seen with a variety of disorders Ageusia – inability to taste Rare due to multiple pathways carrying taste information Copyright © 2011 Pearson Education, Inc. All rights reserved.

Selective Attention Improves perception of what is attended to and interferes with that which is not Internal cognitive processes (endogenous attention) and external events (exogenous attention) focus attention Copyright © 2011 Pearson Education, Inc. All rights reserved.

Change Blindness Change blindness – no memory of that which is not attended to We do not appear to remember parts of a scene that are not the focus of our attention Copyright © 2011 Pearson Education, Inc. All rights reserved.

Neural Mechanisms of Attention
Selective attention is thought to work by strengthening the neural responses to attended-to aspects and by weakening the responses to other For example, spatial attention can shift the location of receptive fields (Wommelsdorf et al. 2006) Copyright © 2011 Pearson Education, Inc. All rights reserved.

Simultanagnosia Simultanagnosia – a difficulty attending to more than one visual object at a time Typical cause: bilateral damage to the dorsal stream (involved with localizing objects in space) Copyright © 2011 Pearson Education, Inc. All rights reserved.

Prepared by Jeffrey W. Grimm Western Washington University

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