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Midterm 2- Lecture Notes

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Department
Psychology
Course
Psychology 2015A/B
Professor
Patrick Brown
Semester
Winter

Description
Pysch 2: Lecture 4/ Chapter 11: Sound - Physical stimulus  neural response  sound percept - Physical: Sound is a moving pressure wave in air or any other medium, Amplitude, Wavelength, Frequency, Pure tones and complex tones, Amplitude and energy. Physically, sound consists of waves in the air. To understand what is waving it’s necessary to understand air pressure. - Perceptual: Sound is the experience we have when we hear - Sound consists of waves of changes in air pressure – the change in pressure is moving through space - Air pressure: o The air pressure changes in one location – the sound source o That change is then transmitted through the air o What is moving through the air is the change in pressure o The air molecules themselves move only very small distances – but the pressure wave is translated through space, potentially over vast distances o The minimum pressure detectable by the human ear is .0002 dynes/cm² o For such sound waves, air molecules are displaced on average .0000000001 cm – about one-tenth of the diameter of an average air molecule. - How do loud speakers produce sound: o Condensation: the diaphragm of the speaker moves out, pushing air molecules together. o Rarefaction: the diaphragm also moves in, pulling the air molecules apart - Sound waves: o Waves in water appear to move outward, but the water is actually moving up and down o Amplitude: the difference in pressure between high and low peaks of a wave, physical, loudness o Wavelength – length of one cycle, from any point on the wave to that same point again o Frequency – # of wavelengths in a given time period, is measured in Hertz (Hz) (1 Hz is one cycle per second) o Pure tone – this sine wave is not a mixture of waves. It cannot be decomposed into simpler forms. o Complex tone – composed of a number of pure tones added together o Sound waves can be added together – this shows constructive interference o Sound waves can be added together – this shows destructive interference o If we add the two pure tones A and B, we get the complex tone C - Periodic sounds: o Pure tones are periodic tones – their waveform has a repeating pattern o Some complex tones are also periodic. The fundamental frequency is the repetition rate for the whole waveform and is also called the first harmonic o The complex tone is made up of pure tones called harmonics – which are multiples of the fundamental frequency o We can analyze a complex tone to find the pure tones it is composed of o We can add harmonics to create complex tones, a process called additive synthesis o The sounds being discussed here are periodic sounds, which are the most widely studied type of sounds. Aperiodic sounds, which do have repeating sounds waves, are also widely heard in our environment, but have not been investigated as extensively as periodic sounds. - Amplitude and energy: A sound source – like guitar strings – displaces air molecules. A wave with low energy shows small displacements. A wave with high energy shows large displacements - Measuring sound intensity: o Considering sound as energy, we compare one sound level to another by asking how many powers of ten one level exceeds the other by o Sometimes we ask how two sounds compare in intensity – that is, we want to know about both sounds o Sometimes we want to measure the intensity of one sound – we compare that sound to a “reference level” sound o How many powers of ten one level exceeds the other by is called the bel, after Alexander Graham Bell, inventor of the telephone o If a loud sound has 1 million times as much energy as a quiet sound, we say that it is 6 bels greater (1 million = 10⁶ = sixth power of ten) o Since the bel is a large unit, we usually deal in decibels (one decibel = one-tenth of a bel) - The decibel: o # of dB = 20 log (P/P₀) o P = SPL we want to express in decibels o P₀ is the (standard) reference level o The decibel scale relates the amplitude of the stimulus to the psychological experience of loudness o The average value of the threshold for sound measured in adults at 1000 Hz) p is the sound pressure of the stimulus, and o is the standard sound pressure which is usually set at 20 micropascals. The standard pressure is close to the pressure of a 1,000 Hz tone at threshold in a free field. Note that adding sound pressure level (SPL) to a dB measure indicates that the standard pressure of 20 micropascals was used. - Perception of loudness: o Larger amplitudes are associated with the perception of greater loudness o How is loudness related to physical intensity (measured in dB)? o Recall: physical intensity is determined by amplitude o Loudness of a 1,000 Hz tone as a function of intensity, determined using Stevens’ magnitude estimation procedure o Loudness of a 1000 Hz tone at 40 dB was given a score of 1.0 o Then relative loudness of a 1000 Hz tone at other intensities given scores by listeners - Perception of pitch: o Perception of pitch is related to frequency o Tone height is the increase in pitch with increasing frequency – e.g., piano keys from left to right yield increasing tone height o Higher frequencies are associated with the perception of higher pitches - Perception of timbre: o All perceptual aspects of a sound other than loudness, pitch, and duration o Attack of tones - buildup of sound at the beginning of a tone o Decay of tones - decrease in sound at the end of a tone o Timbre is closely related to the harmonics, attack, and decay of a tone. Attack can dominate perception of which instrument produces a musical note. If decay is too short, listener may have difficulty assigning the note. o Frequency spectra for a guitar, a bassoon, and an alto saxophone playing a tone with a fundamental frequency of 196 Hz. o The position of the lines on the horizontal axis indicates the frequencies of the harmonics and the height of the lines indicates their intensities - Periodicity pitch: o We can create tones with the fundamental frequency missing, but all the harmonics present – such tones have periodicity pitch o Removal of the fundamental frequency yields a sound with same perceived pitch, but different timbre o Effect of missing fundamental frequency o Removal of the fundamental frequency (aka first harmonic) results in a sound with the same perceived pitch, but with a different timbre o The pitch in a tone with a missing fundamental frequency is called periodicity pitch o A frequency spectrum is a display of the harmonics of a complex sound o Removing the fundamental frequency changes the tone’s waveform but not the repetition rate, which is what indicates the frequency of the harmonic o Same pitch but different timbre - Musical scales and frequency: o Letters in the musical scale repeat o Notes with the same letter name have fundamental frequencies that are multiples of each other. These notes have the same tone chroma o We give notes the same letter name because we perceive such notes as similar to one another o A piano keyboard, indicating the frequency associated with each key. Moving up the keyboard to the right increases the frequency and tone height. - Human hearing: o Range of frequencies: Human hearing range - 20 to 20,000 Hz, Elephants can hear below 20 Hz, Dogs can hear above 40,000 Hz; cats above 50,000 Hz; dolphins as high as 150,000 Hz o In order to hear a sound, the intensity varies with the sound’s frequency o Audibility curve: shows the threshold of hearing in relation to frequency, shows that humans are most sensitive to 2,000 to 4,000 Hz o Telephones typically preserve information in this range o Equal loudness curves - determined by using a standard 1,000 Hz tone o Participants match the perceived loudness of other tones to the 1,000 Hz standard o Resulting curves show dB levels at which sounds of different frequencies appeared equal in loudness to the standard o Auditory response area: Falls between the audibility curve and the threshold for feeling, It shows the range of response for human audition. o The audibility curve and the auditory response area. Hearing occurs in the light green area between the audibility curve (the threshold for hearing) and the upper curve (the threshold for feeling). Tones with combinations of dB and frequency that place them in the light red area below the audibility curve cannot be heard. Tones above the threshold of feeling result in pain. The places where the dashed line at 10 dB crosses the audibility function indicate which frequencies can be heard at 10 dB SPL. - The ear: o Outer ear: pinna (helps with sound location) and the Auditory canal (tube-like & 3 cm long), The resonant frequency of the canal amplifies frequencies between 1,000 and 5,000 Hz o Middle ear: Two cubic centimeter cavity separating inner from outer ear, Contains the three little bones called ossicles: Malleus (the Hammer- moves due to the vibration of the tympanic membrane, attached to the inside surface of the eardrum and picks up energy of vibration there), Incus (the Anvil- transmits vibrations of malleus), Stapes (the Stirrups- transmit vibrations of incus to the inner ear via the oval window of the cochlea, attached to the fluid-filled cochlea, and sends the energy of vibration into that fluid)  Problem: outer and inner ear are filled with air but middle ear is filled with a fluid much denser than air, Because pressure changes in air transmit poorly into the denser fluid  Solution: Ossicles amplify the vibration for better transmission to the fluid  New problem: In the presence of high intensity sounds amplification by ossicles could damage inner ear  Solution: The middle ear contains the smallest muscles in the body. In case of very loud sounds, these muscles dampen the ossicles’ vibrations to protect the inner ear o Inner ear: Main structure is the cochlea (fluid-filled snail-like structure (35 mm long) set into vibration by the stapes), Divided into the scala vestibuli and scala tympani by the cochlear partition, Cochlear partition extends from the base (stapes end) to the apex (far end), Organ of Corti found in the cochlear partition, Tectorial membrane (extends over the hair cells – moves side-to-side in response to movement of cochlear partition), Basilar membrane (vibrates in response to sound and supports the organ of Corti), Organ of Corti (contains inner and outer hair cells, which are the receptors for hearing. It moves up and down.) o Movement of hair cilia in one direction opens ion channels in the hair cell, which results in the release of neurotransmitter onto an auditory nerve fiber; Movement in the opposite direction closes the ion channels so there is no ion flow and no transmitter release - There are two ways nerve fibers signal frequency: Place coding – which fibers are responding, Temporal coding – how fibers are responding - Place coding: o Békésy’s Place Theory of Hearing: Frequency of sound is indicated by the place on the Organ of Corti that has the highest firing rate, Hair cells all along the cochlea send signals to nerve fibers that combine to form the auditory nerve o According to place theory, low frequencies cause maximum activity at the apex end of the cochlea, and high frequencies cause maximum activity at the base o Activation of the hair cells and auditory nerve fibers indicated in red would signal that the stimulus is in the middle of the frequency range for hearing o Envelope of the traveling wave indicates the point of maximum displacement of the basilar membrane. Nerve fibers fire most strongly at this location. Each line indicates the position of the basilar membrane at 4 points in time o The envelope of the basilar membrane’s vibration at frequencies ranging from 25 to 1,600 Hz, as measured by Békésy (1960). These envelopes were based on measurements of damaged cochleas. The envelopes are more sharply peaked in healthy cochleas o Tonotopic map: plotting the frequencies o Neural frequency tuning curves: Pure tones are used to determine the threshold for specific frequencies measured at individual neurons. Plotting thresholds for frequencies results in tuning curves. Frequency to which the neuron is most sensitive is the characteristic frequency. Plotting thresholds for frequencies results in tuning curves. Frequency tuning curves of cat auditory nerve fibers. The characteristic frequency of each fiber is indicated by the arrows along the frequency axis. o Results of auditory masking experiments: First, thresholds for a number of frequencies are determined. Then, a single intense masking frequency is presented at the same time that the thresholds for the original frequencies are re-determined. The intensities must be increased to hear these test tones when the masking tone is present. The interference produced by the masking tone is greatest at the frequency of the tone – because the traveling wave of the mask interferes with the traveling wave of the stimulus tone at the point where they both have maximum displacement. Vibration patterns caused by 200- and 800-Hz test tones, and the 400-Hz mask (shaded). Notice that the vibration caused by the masking tone overlaps the 800-Hz vibration more than the 200-Hz vibration - Temporal coding theory: o Temporal coding – Rate or pattern of firing of nerve impulses conveys frequency information o Groups of fibers fire with periods of silent intervals creating a pattern of firing o This allows information about the frequency of the sound to be coded into the firing rate of the auditory nerve fibers o Hair cell activation and auditory nerve fiber firing are synchronized with pressure changes of the stimulus o The auditory nerve fiber fires when the cilia are bent to the right. This occurs at the peak of the sine-wave change in pressure. - Place and temporal coding for pitch: o Place coding is effective for the entire range of hearing o Temporal coding with phase locking is effective up to 4,000 Hz o Thus, both codes work for frequencies below 4,000 Hz o Phase locking: Nerve fibers fire in bursts, Firing bursts happen at or near the peak of the sine-wave stimulus, Thus, they are “locked in phase” with the wave. - Hearing loss: o Conductive hearing loss: Blocking sound from the receptor cells, Presbycusis (Noise-induced hearing loss, Smokers are more vulnerable to this effect) o Sensori-neural hearing loss: Loud noise can severely damage the Organ of Corti, Greatest loss is at high frequencies, Affects males more severely than females. Hearing loss in presbycusis as a function of age. All the curves are plotted relative to the 20-year-old curve, which is taken as the standard. Appears to be caused by exposure to damaging noises or drugs. - Advantages of ear plugs: small and easily carried, convenient to use with other personal protection equipment (can be worn with ear muffs), more comfortable for long-term wear in hot, humid work areas, convenient for use in confined work areas - Disadvantages of ear plugs: requires more time to fit, more difficult to insert and remove - require good hygiene practices, may irritate the ear canal, easily misplaced, more difficult to see and monitor usage - Advantages of ear muffs: less attenuation variability among users, designed so that one size fits most head sizes, easily seen at a distance to assist in the monitoring of their use, not easily misplaced or lost, may be worn with minor ear infections - Disadvantages of ear muffs: less portable and heavier, more inconvenient for use with other personal protective equipment, more uncomfortable in hot, humid work area, more inconvenient for use in confined work areas, may interfere with the wearing of safety or prescription glasses: wearing glasses results in breaking the seal between the ear muff and the skin and results in decreased hearing protection Lecture 5: Chapter 14/15 Cutaneous senses: - Cutaneous senses - perception of touch and pain from stimulation of the skin - Proprioception - ability to sense position of the body and limbs - Kinesthesis - ability to sense movement of body and limbs - The skin: o Largest and heaviest organ in the body o Keeps damaging agents from penetrating the body o Epidermis is the outer layer of the skin, made up of dead skin cells o Dermis contains mechanoreceptors that respond to stimuli such as pressure, stretching, and vibration - Receptor neurons in skin are classified on two dimensions: Pattern of firing, Depth in the skin - Receptor neurons in skin show two basic patterns of firing: continuous response (cell- firing begins with stimulus onset and continues for duration of stimulus), onset/offset response (cell responds to change – when stimulus begins and when it ends – not to continuous stimulation) - Mechanoreceptors respond to mechanical pressure on, or distortion of, the skin o Merkel receptors fire continuously while stimulus is present and are responsible for sensing fine details, close to the surface o Meissner corpuscle: fire only to stimulus onset and offset and responsible for controlling hand-grip, close to the surface o Ruffini cylinder: deeper in the skin, fires continuously to stimulation, associated with perceiving stretching of the skin o Pacinian corpuscle: deeper in the skin, fires only to stimulus onset and offset, associated with sensing rapid vibrations and fine texture - Measuring tactile acuity o Two-point threshold: minimum separation needed between two points to perceive them as two units o Grating acuity: placing a grooved stimulus on the skin and asking the participant to indicate the orientation of the grating o Raised pattern identification: using such patterns to determine the smallest size that can be identified o Merkel receptors are densely packed on the fingertips - similar to cones in the fovea o Correlation between density of Merkel receptors and tactile acuity o Note: lower numbers indicate greater sensitivity on both scales o As space between receptors goes down, acuity increases – smaller differences can be resolved - Cortical mechanisms for tactile acuity: Body areas with high acuity have larger areas of cortical tissue devoted to them. This parallels the “magnification factor” seen in the visual cortex for foveal cones - Homunculus: o Body map (homunculus) on the cortex in S1 and S2 shows more cortical space allocated to parts of the body that are responsible for dealing with detail o The sensory homunculus on the somatosensory cortex. Parts of the body with the highest tactile acuity are represented by larger areas on the cortex. o The size of the body parts on the left indicates (a) amount of sensory cortex dedicated to that part, and (b) the resulting acuity of touch perception there o Two point thresholds  o Areas with higher acuity also have smaller receptive fields on the skin o Receptive fields of monkey cortical neurons that fire when the fingers are stimulated: Stimulation of two nearby points on the finger causes separated activation on the finger area of the cortex o Stimulation of two nearby points on the arm and the hand causes overlapping activation in the arm area of the cortex - Perceiving texture: o Katz (1925) proposed that perception of texture depends on two cues:  Spatial cues: determined by the size, shape, and distribution of surface elements  Temporal cues: determined by the rate of vibration as skin is moved across finely textured surfaces o Hollins and Reisner (2000): support for the role of temporal cues  To detect fine texture differences, people had to move their fingers across the surface  Participants perceived roughness of two fine surfaces to be about the same when felt with stationary fingers different when they were allowed to move their fingers - Pain perception: o Pain is a multimodal phenomenon containing a sensory component and an affective or emotional component o Three types of pain: o Nociceptive: signals impending damage to the skin, respond to heat, chemicals, severe pressure, and cold, Threshold of response must be balanced to warn of damage, but not be affected by normal activity o Inflammatory: caused by damage to tissues and joints or by tumor cells o Neuropathic: Caused by damage to the central nervous system, such as: Stroke, Repetitive movements (e.g., causing carpal tunnel syndrome) - Opiods and pain: Brain tissue releases neurotransmitters called endorphins, Evidence shows that endorphins reduce pain, Stimulating sites in the brain that cause the release of endorphins can reduce the pain by stimulating opiate receptor sites, People whose brains release more endorphins can withstand higher pain levels, Injecting naloxone blocks the receptor sites, causing more pain, Naloxone also decreases the effectiveness of placebos, Naloxone reduces the effect of heroin by occupying a receptor site normally stimulated by heroin - Direct pathway model of pain: o An early model that stated nociceptors are stimulated and send signals to the brain o Problems with this model: pain can occur when no stimulation of the skin occurs, Pain can be affected by a person’s attention, Pain can be affected by a person’s mental state - Gate control model of pain perception: o The “gate” consists of substantia gelatinosa cells in the spinal cord (SG- and SG+) o Input into the gate comes from: Large diameter fibers, Small diameter fibers, Central control o Large diameter (L) fibers - information from tactile stimuli o Small diameter (S) fibers - information from nociceptors o Central control - information about cognitive factors from the cortex o Stimulation into the SG- from central control or from L-fibers into the T-cell closes gate and prevents pain o Pain does occur due to stimulation from the S-fibers into the SG+ cell and into the T-cell o Actual mechanism is more complex than this model suggests - How can we influence pain: o Cognitive & experiential aspects of pain  Expectation - when surgical patients are told what to expect, they request less pain medication and leave the hospital earlier  Placebos can also be effective in reducing pain  Shifting attention - virtual reality technology has been used to keep patients’ attention on other stimuli than the pain-inducing stimulation  deWied and Verbaten (2001): Emotional distraction - participants could keep their hands in cold water longer when shown positive pictures  De Tommaso et al. (2008): Participants given pain stimulus while looking at self-rated beautiful, ugly, or neutral paintings  De Tommaso et al. (2008): Paintings considered beautiful lowered pain ratings, Neutral & ugly paintings had no similar effect o Sensory & affective components of pain - Pain in social situations: o Experiment by Eisenberger et al. (2003): Study of effects of social exclusion during game play (virtual reality game in fMRI scanner), Brain areas responding to social exclusion very similar to those active in response to physical pain o Experiment by Singer et al. (2004): Romantically involved couples participated, The woman’s brain activity was measured by fMRI , Either the woman or her partner received shocks, Affective part of the brain’s pain circuit was activated in both conditions Chemical senses: - The chemical senses identify things that should be consumed for survival - The ch
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