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Chapter Four Sensation.

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Presentation on theme: "Chapter Four Sensation."— Presentation transcript:

1 Chapter Four Sensation

2 Figure 4.1: Elements of a Sensory System
Make into a chemical signal Ear,nose Copyright © Houghton Mifflin Company. All rights reserved.

3 How are physical properties coded into neural activity?
The Problem of Coding How are physical properties coded into neural activity? Doctrine of Specific Nerve Energies Types of codes Temporal Spatial Copyright © Houghton Mifflin Company. All rights reserved.

4 Linkages: Sensation and Biological Aspects of Psychology
Organized sensory information is called a representation. Shared features of representations of vision, hearing, and skin senses: Information from each sense reaches the cortex via the thalamus. Representation of world is contralateral to the part of the world being sensed. Copyright © Houghton Mifflin Company. All rights reserved.

5 Linkages: Sensation and Biological Aspects of Psychology (cont’d.)
Shared features (cont’d.): The cortex contains topographical representations of each sense. The density of nerve fibers in a sense organ determines how well it is represented in the cortex. Each region of primary sensory cortex is divided into columns of cells that have similar properties. Regions of cortex other than the primary areas do additional processing of sensory information. Copyright © Houghton Mifflin Company. All rights reserved.

6 Sound A repeated fluctuation in the pressure of air, water, or some other substance. Produced by vibrations of an object. Wave: Repeated variation in pressure that spreads out in three dimensions. Copyright © Houghton Mifflin Company. All rights reserved.

7 Physical Characteristics of Sound
A waveform represents a wave in two-dimensions. Characteristics of Waveforms Amplitude Wavelength Frequency Continue Copyright © Houghton Mifflin Company. All rights reserved.

8 Figure 4.2: Sound Waves and Waveforms
Return Copyright © Houghton Mifflin Company. All rights reserved.

9 Psychological Dimensions of Sound
Loudness Intensity of sound sources. Pitch Timbre Continue Copyright © Houghton Mifflin Company. All rights reserved.

10 Table 4.1: Intensity of Sound Sources
Return Copyright © Houghton Mifflin Company. All rights reserved.

11 Figure 4.3: Structures of the Ear
Copyright © Houghton Mifflin Company. All rights reserved.

12 Figure 4.4: The Cochlea Copyright © Houghton Mifflin Company. All rights reserved.

13 The three tiny bones of the middle ear are fused together.
Conduction Deafness The three tiny bones of the middle ear are fused together. Prevents accurate reproduction of vibrations. Surgery can break bones apart or replace them with plastic ones. Hearing aids can also help. Copyright © Houghton Mifflin Company. All rights reserved.

14 Results when the auditory nerve or the hair cells are damaged.
Nerve Deafness Results when the auditory nerve or the hair cells are damaged. Can be caused by extended exposure to loud noise. Cochlear implants can stimulate the auditory nerve. Hair cell regeneration as a possible treatment. Continue Copyright © Houghton Mifflin Company. All rights reserved.

15 Auditory nerve  brainstem  thalamus
Auditory Pathways Auditory nerve  brainstem  thalamus Various aspects of sound processed in different regions of auditory system. Certain parts of auditory cortex process certain types of sounds. Copyright © Houghton Mifflin Company. All rights reserved.

16 Different people may experience the “same” sound as different pitches.
Sensing Pitch Different people may experience the “same” sound as different pitches. Pitch-recognition abilities influenced by genetics. Cultural factors are also partly responsible for the way in which a pitch is sensed. Copyright © Houghton Mifflin Company. All rights reserved.

17 Locating Sounds Determined partly by the very slight difference in when sound arrives at each ear. The brain also uses information about the difference in sound intensity at each ear. Copyright © Houghton Mifflin Company. All rights reserved.

18 Coding Intensity and Frequency
The more intense the sound, the more rapid the firing of a given neuron. Frequency appears to be coded in two ways. Copyright © Houghton Mifflin Company. All rights reserved.

19 Coding Frequency: Place Theory
Sounds produce waves that move down the basilar membrane. Where the wave peaks depends on the frequency of the sound. Hair cells at a particular place on the membrane respond most to a particular frequency. But how are very low frequencies coded? Continue Copyright © Houghton Mifflin Company. All rights reserved.

20 Coding Frequency: Frequency Matching Theory
Firing rate of an auditory nerve matches a sound wave’s frequency. Sometimes called the volley theory of frequency coding. Copyright © Houghton Mifflin Company. All rights reserved.

21 Figure 4.7: Spectrum of Electromagnetic Energy
Copyright © Houghton Mifflin Company. All rights reserved.

22 What Influences Sensations of Light?
Light Intensity: How much energy the light contains. Determines the brightness of light. Light Wavelength: The distance between peaks in light waves. Determines what color we see. Copyright © Houghton Mifflin Company. All rights reserved.

23 Figure 4.8: Major Structures of the Eye
Copyright © Houghton Mifflin Company. All rights reserved.

24 Figure 4.9: The Lens and the Retinal Image
Copyright © Houghton Mifflin Company. All rights reserved.

25 Converting Light into Images
Visual transduction is the conversion of light energy into neural activity. Conversion done by photoreceptors in the retina. Two main types of photoreceptors: Rods and cones. Copyright © Houghton Mifflin Company. All rights reserved.

26 Rods unable to discriminate color.
Rods and Cones Rods unable to discriminate color. But more sensitive to light than cones. Three forms of pigments in cones provide the basis for color vision. Rods and cones differ in their distribution in the eye. Copyright © Houghton Mifflin Company. All rights reserved.

27 Figure 4.10: Cells in the Retina
Copyright © Houghton Mifflin Company. All rights reserved.

28 Figure 4.11: Center-Surround Receptive Fields of Ganglion Cells
Copyright © Houghton Mifflin Company. All rights reserved.

29 Figure 4.12: The Hermann Grid
Copyright © Houghton Mifflin Company. All rights reserved.

30 Figure 4.13: Find Your Blind Spot
Copyright © Houghton Mifflin Company. All rights reserved.

31 Figure 4.14: Pathways from the Ganglion Cells into the Brain
Copyright © Houghton Mifflin Company. All rights reserved.

32 Parallel Processing of Visual Properties
Brain conducts separate kinds of analysis simultaneously on the same information. The “what” system The “where” system How are the parallel streams assembled into a unified conscious experience? Copyright © Houghton Mifflin Company. All rights reserved.

33 Hierarchical Processing of Visual Information
Individual cells in the visual cortex receive input from several LGN neurons. Cortical cells respond to specific features of objects in the visual field. Complex feature detectors can be built up from connections among simple feature detectors. Some of cortical processing occurs in a hierarchical fashion. Continue Copyright © Houghton Mifflin Company. All rights reserved.

34 Figure 4.15: Construction of a Feature Detector
Return Copyright © Houghton Mifflin Company. All rights reserved.

35 Psychological Dimensions of Light
Hue Saturation Brightness Copyright © Houghton Mifflin Company. All rights reserved.

36 Figure 4.16: The Color Circle
Copyright © Houghton Mifflin Company. All rights reserved.

37 Figure 4.17: Matching a Color by Mixing Lights of Pure Wavelengths
Copyright © Houghton Mifflin Company. All rights reserved.

38 Trichromatic or Young-Helmholtz Theory of Color Vision
Any color can be produced by mixing pure lights of blue, green, and red. There are three types of cones, each most sensitive to particular wavelengths. Ratio of the activities of the three types of cones indicates what color is sensed. Copyright © Houghton Mifflin Company. All rights reserved.

39 Figure 4.18: Relative Responses of Three Cone Types to Different Wavelengths of Light
Copyright © Houghton Mifflin Company. All rights reserved.

40 Problem with the Trichromatic Theory
Cannot explain some aspects of color vision, such as afterimage. Example: Stare at the dot on the next slide for thirty seconds. Copyright © Houghton Mifflin Company. All rights reserved.

41 NOTE TO INSTRUCTOR: This slide has a advance transition set for 30 seconds to demonstrate the afterimage effect.

42

43 Opponent-Process Theory of Color Vision
Visual elements sensitive to color are grouped into three pairs. Members of each pair oppose, or inhibit, each other. Three pairs are a red-green element, a blue-yellow element, and a black-white element. Explains color afterimages and the phenomenon of complimentary colors. Copyright © Houghton Mifflin Company. All rights reserved.

44 Synthesis and Update At level of photoreceptors, a slightly revised version of the trichromatic theory is correct. Individual differences in long-wavelength pigments. At the ganglion cell level, the center and surround of the receptive field are color coded. Copyright © Houghton Mifflin Company. All rights reserved.

45 Figure 4.20: Color Coding and Ganglion Cells
Copyright © Houghton Mifflin Company. All rights reserved.

46 Interaction of the Senses
Not uncommon for senses to interact. Synesthesia is a more unusual mixing of senses, or dimensions within senses. Copyright © Houghton Mifflin Company. All rights reserved.

47 Olfaction detects airborne chemicals
The Chemical Senses Olfaction detects airborne chemicals Our sense of smell Gustation detects chemicals in solution that come into contact with receptors inside the mouth Our sense of taste Copyright © Houghton Mifflin Company. All rights reserved.

48 Figure 4.23: The Olfactory System
Copyright © Houghton Mifflin Company. All rights reserved.

49 Employs about 1,000 different types of receptors.
Olfactory System Employs about 1,000 different types of receptors. Only sense that does not send its messages through the thalamus. Processing in several brain regions including frontal lobe and amygdala Strong relationship between olfaction and emotional memory Copyright © Houghton Mifflin Company. All rights reserved.

50 Olfactory System (cont’d.)
Only sense that does not send its messages through the thalamus. Pathways from olfactory bulb sends information on for further processing in several brain regions. Including frontal lobe and amygdala. Strong relationship between olfaction and emotional memory. Copyright © Houghton Mifflin Company. All rights reserved.

51 Role of pheromones in humans not clear
Chemicals released by one animal, and when detected by another, can shape the second animal’s behavior or physiology. Role of pheromones in humans not clear Copyright © Houghton Mifflin Company. All rights reserved.

52 Smell and taste act together to form system known as flavor.
Smell, Taste, and Flavor Smell and taste act together to form system known as flavor. Tastes and odors can prompt strong emotional responses. Nutritional state can affect taste and flavor of food and motivation to eat particular foods. Flavor includes other characteristics of food. Copyright © Houghton Mifflin Company. All rights reserved.

53 Somatic Senses and the Vestibular System
Somatosensory systems are spread throughout the body Somatic senses include: Skin senses of touch, temperature, and pain Kinesthesia Vestibular system tells the brain about the position and movement of the head Copyright © Houghton Mifflin Company. All rights reserved.

54 Energy detected is physical pressure on tissue.
Touch Energy detected is physical pressure on tissue. Many nerve endings in the skin act as touch receptors. Touch is both an active and passive sense. Changes in touch provide most important sensory information. Copyright © Houghton Mifflin Company. All rights reserved.

55 Coding of Touch Information
Intensity of the stimulus is coded by: Firing rate of individual neurons and The number of neurons stimulated. Location is coded by the location of the neurons responding to the touch. Copyright © Houghton Mifflin Company. All rights reserved.

56 Some of the skin’s sensory neurons respond to a change in temperature.
“Warm” and “cold” fibers Sensations of touch and temperature sometimes interact. Stimulation of the touch sense can have psychological and physiological effects. Copyright © Houghton Mifflin Company. All rights reserved.

57 Pain provides information about impact of world on body.
Information-carrying aspect of pain very similar to that of touch and temperature. Two types of nerve fibers carry pain signals from skin to the spinal chord. Pain pathways Cerebral cortex plays role in the experience of pain. Continue Copyright © Houghton Mifflin Company. All rights reserved.

58 Figure 4.25: Pain Pathways Return
Copyright © Houghton Mifflin Company. All rights reserved.

59 Emotional Aspects of Pain
Specific pathways carry an emotional component of the painful stimulus to several areas of the brain. Overall emotional response depends greatly on cognitive factors. Knowing about the pain. Use of pain-reducing cognitive strategies. Copyright © Houghton Mifflin Company. All rights reserved.

60 Modulating Pain Gate Control Theory Natural Analgesics Serotonin
Endorphins Copyright © Houghton Mifflin Company. All rights reserved.

61 Thinking Critically: Does Acupuncture Relieve Pain?
What am I being asked to believe or accept? Twirling a needle in the skin can relieve pain. What evidence is available to support the assertion? MRI studies. Positive results in patients treated by acupuncture for various kinds of pain. Acupuncture associated with release of endorphins. Copyright © Houghton Mifflin Company. All rights reserved.

62 Thinking Critically: Does Acupuncture Relieve Pain? (cont’d.)
Are there alternative ways of interpreting the evidence? Might simply confirm that the body’s painkilling system can be stimulated by external means. What additional evidence would help to evaluate the alternatives? More placebo-controlled studies of acupuncture. What is the general relationship between internal painkilling systems and external methods for stimulating them? Copyright © Houghton Mifflin Company. All rights reserved.

63 Thinking Critically: Does Acupuncture Relieve Pain? (cont’d.)
What conclusions are most reasonable? In some circumstances, acupuncture does relieve pain, but it is not a cure-all. No evidence that acupuncture is better than other painkilling procedures. Quality of future studies of acupuncture will determine whether acupuncture finds a more prominent place in Western medicine. Copyright © Houghton Mifflin Company. All rights reserved.

64 Proprioceptive Senses
Sensory systems that provide information to the brain about: The position of the body. What each of part of the body is doing. Vestibular sense indicates the position of the head in space and its general movements. Sense of balance. Copyright © Houghton Mifflin Company. All rights reserved.

65 Vestibular Sense Organs: Neural connections to: Vestibular sacs
Otoliths Semicircular canals Neural connections to: The cerebellum The autonomic nervous system The eye muscles Copyright © Houghton Mifflin Company. All rights reserved.

66 Kinesthesia Sense that indicates where the parts of the body are with respect to one another. Necessary guide for movement. Kinesthetic information comes primarily from the joints as well as muscles. Copyright © Houghton Mifflin Company. All rights reserved.

67 Focus on Research Methods: The Case of the Mysterious Spells
What was the researcher’s question? Is there a specific brain region that, when activated by a seizure, causes the sensation of orgasm? How did the researcher answer the question? Used the case study method of research. Studied person’s brain activity while she was actually having a spell. Copyright © Houghton Mifflin Company. All rights reserved.

68 Focus on Research Methods: Mysterious Spells (cont’d.)
What did the researcher find? EEG showed seizures in right temporal lobe. MRI revealed small area of abnormal tissue. Seizures stopped after removal of tissue. What do the results mean? Person was having “localization-related epilepsy.” Right temporal lobe may play a special role in creating the sensory experience of orgasm. Copyright © Houghton Mifflin Company. All rights reserved.

69 Focus on Research Methods: Mysterious Spells (cont’d.)
What do we still need to know? How specific is the linkage between activity in this brain region and the sensory experience of orgasm? Did person continue to experience orgasms during sexual activity? Copyright © Houghton Mifflin Company. All rights reserved.

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