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Exam 3 Study Guide

by: Fiaza Ahmed

Exam 3 Study Guide EXP 4204

Fiaza Ahmed
GPA 3.7

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Visual Attention The Auditory System The Auditory Brain and Sound Localization
Sensation and Perception
Timothy Allen
Study Guide
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This 11 page Study Guide was uploaded by Fiaza Ahmed on Tuesday April 12, 2016. The Study Guide belongs to EXP 4204 at Florida International University taught by Timothy Allen in Spring 2016. Since its upload, it has received 93 views. For similar materials see Sensation and Perception in Psychlogy at Florida International University.


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Date Created: 04/12/16
Visual Attention: Attention: A set of processes that allow us to select or focus on some stimuli. Selective Attention: Covert Attention Selective Attention:  Selective Attention: The process of attention that allow us to focus on one source when many are present. We direct our perceptual resources to one stimulus. o Primates achieve selective attention through foveal fixation o Foveal fixation: directing the center of gaze at the object of interest o Saccades: rapid movements of the eyes that changes fixation from one object of location to another o Smooth Pursuit: eye movement in the eyes move smoothly to follow a moving object o Vergence = eye movements in which the two eyes move in opposite directions (divergence and convergence) Covert attention: attention occurring without fixation (mental attention)  Enhance our mental focus on something  Pay attention to something not directly on our fixation point  Focus on things, at the expense of other things (William James)  Divided Attention: process of attending to multiple sources of information Ex: Driving, radio, cell phone Attention and the direction of gaze in space  Typically we attend to a particular location in space by directing our gaze to that location  If attention shifts, so does our gaze  Stimulus onset asynchrony: refers to the difference in time between the occurrence of one stimuli and the occurrence of another. Features of Attention:  Stimulus Salience: some objects in the environment attract our attention  Attentional capture: The process whereby a salient stimulus causes us to shift attention to that stimulus.  Change blindness: The difficulty we experience in detecting differences between two stimuli that are identical except for or more changes to the image. Even when we have engaged our attention and are directing our visual search in a very conscious manner, we may still fail to see the changes in an image.  Inattentional blindness: refers to a phenomenon in which people fail to perceive an object or event that is visible but not attended to. This refers to situations in which a well-above threshold event or object is not seen because the person’s attention is direction elsewhere. Visual Search  One of the most important tasks in vision  Feature search: The search for a target in which the target is specified by a single feature  Conjunction Search: The search for a target in which the target is specified by a combination of features.  Feature integration Theory: Some features can be processed in parallel and quickly prior to using attentional resources, whereas other visual characteristics require us to use attention and are done serially and therefore less quickly. *Conjunction searches take longer than non-conjunction searches. Attentional Blink and Rapid serial Visual Presentation The Anatomy and Physiology of Attention:  The orienting attention network: Allows us to engage in visual search and direct our visual attention to different locations in visual space o Damage to this causes unilateral neglect  The Executive Attention Network: A system that focuses on attention as the inhibition of habitual responses and the top- down control of attention; found in the front lobe o Allows us to inhibit auditory stimuli so that we can concentrate on visual stimuli, or it can allow us to inhibit visual stimuli so that we can concentrate on auditory stimuli. o In Models of memory the executive attention network is called central executive. The Neuropsychology of Attention:  When there is damage caused to the right posterior parietal lobe, a condition called hemifield neglect or unilateral visual neglect may arise. This condition almost always occurs when the right parietal lobe is affected, leading to a deficit in the left visual world.  Hemifield neglect (unilateral visual neglect): a condition in which a person fails to attend stimuli on one side of the visual world (usually left) as a consequence of neurological damage to the posterior parietal lobe. o This is a attentional problem and not a visual one  Balint’s syndrome: a rare condition in which function in both the left and right posterior parietal lobes has been compromised o Patients with this have difficulty locating things in space, which results in difficulty of grasping objects. o As a consequence, these patients suffer from simultagnosia, which is a deficit in perceiving more than one object at a time. o Ignore both left and right visual world  Synchrony Hypothesis : neurons from different part of the cortex that fire together are processing information about the same object  Time scale for the synchrony is milliseconds… not seconds!  Attention is thought to increase synchrony between neurons processing the same object  Sometimes this is talked about as reducing spike-timing “jitter” Developmental Aspects of Visual Attention:  Attention in very young infants is determined by how long they can maintain a gaze at an interesting stimulus o Attention is studied in infants by procedure known as oddball procedure o Infants are better at selective attention than their older family members Bistability: Phenomena in which a static visual image leads to alternating perceptions Blindsight:  Blindsight refers to the residual ability to make visual responses when a patient is subjectively blind in certain regions of his or her visual field. The Auditory System Sound as a Stimulus  The sound stimulus is the periodic variations in air pressure travelling out from the source of the variations.  Water transmits sounds faster than air does  Sound Waves: are the waves of pressure changes that occur in the air as a function of the vibration of a source. Alternating high- and low-pressure regions in neighboring regions of air molecules (air pressure changes).  Air does not travel, but sound waves permeate through the air.  A wave is an oscillation that travels through a medium by transferring one particle or point to another without causing any permanent displacement of the medium.  Sound can be measured by the wave’s wavelength and frequency  The time between two consecutive high peaks is the cycle of a sound wave  Energy of a sound wave weakens across time and space The Physical Stimulus:  Sound travels as in a pattern of sine waves.  A pure tone is the simplest form of sound that is composed of a uniform sine wave pattern of oscillations (virtually nonexistent in nature)  A pure tone can be described by amplitude and frequency.  Amplitude: size of pressure change * Frequency and wavelength are inverse to one another. Frequency is the number of cycles per second, and wavelength is the time course on one cycle Frequency and Pitch  Frequency: in a sound stimulus, the number of cycles that occur in a second  Pitch: The subjective experience of sound that is most closely associated with the frequency of a sound stimulus; related to the experience of whether the sound is high or low, such as the two ends of the keyboard of a piano. Children and young adults hear over a range from about 20 to 20,000 Hz Young adults: we lose much of our hearing in the highest range 40 years: it is unlikely that frequencies above 14,000 Hz are heard. 50 years old, upper limit may be down to 12,000 Hz. Tone Chroma  Moving up the piano keys increases the tone height (perceptual term).  Notes on chromatic scale: A, A# or Bb, B, C, C# or Db, D, D# or Eb, E, F, F#, G, G#  The chromatic scale has 12 divisions between octaves, which is a different frequency with the same tone chroma, like middle C and High C.  Different cultures can have a different number of divisions between octaves, resulting in different scales  Harmonics: higher frequencies present in a complex sound that are integer multiples of the fundamental frequency.  Almost all sounds are complex sounds: which consist of multiple frequencies. These frequencies combine to form a complex waveform. A complex waveform can be broken down into its composite frequencies through a mathematical formula known as Fourier analysis.  Fundamental frequency: lowest frequency present in the complex sound and one that determines the perceived pitch of that sound.  The fundamental frequency determines the pitch of a sound but the harmonics provide the timbre that differentiates the sounds between different instruments.  Timbre: the perceived sound differences between sounds with the same pitch but possessing different higher harmonics.  Phase: the position in one cycle of a wave; there are 360 degrees in a single cycle of a wave. Refer to figure 10.10 Anatomy of the Ear: The ear funnels sound waves towards specialized hair cells in the inner ear that transduce the sound from the physical sound energy into a neural impulse which then travels to the auditory regions of the brain The Outer Ear:  Pinna: the structure that collects sound and funnels it into the auditory canal. (helps in sound localization)  External Auditory canal: the channel that conducts sound from the pinna to the tympanic membrane. About 25 mm long (the length helps to amplify frequencies and helps to protect the tympanic membrane)  Tympanic Membrane: Thin elastic sheet that vibrates in response to sounds coming through the external auditory canal; commonly known as the eardrum (damaging this can result in hearing loss) The Middle Ear: Consists of three small bones that transmit sound into the inner ear  Ossicles: The small bones in the middle ear. When the tympanic membrane vibrates, it causes motion in these three small bones which then conduct the sounds mechanically.  Malleus: The first ossicle in the middle ear; receives vibrations from the tympanic membrane and transmits them to the incus  Incus: an ossicle in the middle ear; receives vibrations from malleus and transmits them to the stapes Important functions of the middle ear:  The Eustachian tube: a thin tube that connects the middle ear with the pharynx and serves to equalize air pressure on either side of the eardrum o Normally it is closed but it briefly opens when we swallow or yawn (pooping ears phenomenon) o The ossicles also serve a role in attenuating loud sounds. There is a muscle that is attached to the malleus called the tenortympani and a second muscle attached to the stapes called the stapedius. Their job is to tense in the presence of very loud noises, restricting the movements of the ossicles and avoiding damage to the inner ear (acoustic reflex) The Inner Ear: The inner ear contains the parts of the ear that transduce sound into a neural signal. The hair cells situated along the organ of Corti in the cochlea act by taking vibrations and converting them into a neural signal  Cochlea: snail-shaped structure of the inner ear that houses the hair cells that transduce sound into a neural signal. The cochlea has three liquid filled chambers o Tympanic canal: one of three chambers in the cochlea; separated from the middle canal by the basilar membrane o Middle canal: separated from the tympanic canal by the basiliar membrane; contains the organ of corti o Vestibular canal: separated from the middle canal by Reissner’s membrane o Round window: A soft tissue substance at the base of the tympanic canal whose function is an “escape” valve for excess pressure from loud sounds that arrive in the cochlea. The Basilar Membrane of the Cochlea  Reissner’s membrane: the membrane that separates the vestibular and middle canals  Basilar membrane: fibers that separate the tympanic canal from the middle canal; the organ of corti lies on the basilar membrane  Organ of corti: a structure on the basilar membrane that houses the hair cells that transduce sound into a neural signal  Perilymph: the fluid that fills the tympanic canal and the vestibular canal  Characteristic frequency: each location along the basilar membrane responds to this. The Organ of Corti  This organ is the structure along the basilar membrane that contains the hair cells that transduce sound into a neural signal  Contains dendrites of the auditory nerve that brings the neural signal to the brain  Hair cells have hair like filaments called stereocilia  Stereocilia bend in response to the movement of basilar membrane  There are layers of hair cells that follow basilar membrane 1. Outer hair cells (three times as many inner hair cells) These cells refine and amplify the neural responses of the inner hair cells 2. Inner hair cells (3,500 inner hair cells) these cells are responsible for transducing neural signal  Tectorial membrane: A membrane that rests above the hair cells within the organ of Corti George Von Bekesy  Won the Nobel Prize in 1928  Place Theory of Hearing: The frequency of a sound is indicated by the place along the Organ of Corti at which the nerve firing is highest.  Developed a unique method for dissecting the cochlear in the human cadaver and observe vibrations of the basilar membrane *Temporal code theory is the alternative to place theory  Tonotopic map is a the mapping of frequency onto space.  Place theory in cochlea confirmed with electrophysiolgical recordings The Cochlea:  Fourier analysis is a technique to mathematically break down complex sounds into their constituent parts  The cochlear does this mechanically by the vibratory activity and corresponding hair cell activity at different points along its axis The Auditory Brain and Sound Localization Brain Anatomy and the Pathway of Hearing Auditory Nerve Fibers:  Inner hair cells in the cochlea form synapses with auditory nerve fibers.  Auditory nerve fibers form the eighth cranial nerve, which then makes it way to the brain  The auditory tract goes through cochlear nucleus: a structure in the brain stem that receives input from the inner hair cells  Attached to the cochlear nucleus is the trapezoid body: a structure in the brain stem that plays a role in determining the direction of sounds  From the cochlear nucleus and the trapezoid body, the sound signal goes to the superior olive in the brain stem. It is a structure in the brain stem that receives input from both ears.  The next synapse in ascending pathway of auditory information is the inferior colliculus, which then projects information to the medial geniculate nucleus.  Auditory nerve fibers from each ear go to each side of the temporal lobe. Auditory Cortex: A large multifaceted area located in the temporal lobe. The areas in the temporal cortex that process auditory stimuli. Auditory core region 1. Primary auditory cortex: the first area in the auditory cortex which receives input from the medial geniculate nucleus. o Cells in this region show tonotopic organization: the organization of neurons within a region in the brain according to the different frequencies to which they respond. 2. Rostal core 3. Rostaltemporal core  “What” system: starts in the core region and then moves to more anterior parts of the temporal lobe. o Identifying sounds o Music and language perception  “Where” system: begins in the core region of the auditory cortex and then moves to posterior regions of the temporal cortex as well as the parietal lobe. o Responsible for localizing sound in space Localizing Sound In the auditory system, cochlea is organized tonotopically and spatial localization is done by a number of indirect mechanisms.  We must be able to localize sound in three dimensional space  Azimuth: the left-right or side to side aspect of sound localization  Elevation: the up down dimensions of sound localization  Distance: refers to how far a sound is from the listener and whether it is in front of or behind the listener. People are best at located sounds in front of their head, compared to the side and back Interaural Time Difference: The time interval between when a sound enters one ear and when it enters the other ear.  It takes sound longer to reach one ear versus the other ear in most locations  ITD detectors are neurons early in the auditory processing stream that are sensitive to specific ITDs  These neurons provide information for topographic maps: mapping auditory space onto brain space Interaural Level Differences  The sound level reaching each ear is different, largely because of your head (acoustic shadow: the area on the side of the head opposite from the source of a sound in which the loudness of sound is less because of blocked sound waves.)  This information contribute to sound localization along the azimuth  ILD is more effective at high frequencies compared to low frequencies Cone of Confusion Region of positions in space in which sounds create the same Interaural time and Interaural level differences Elevation Perception: Our auditory system detects elevation through a series of changes in sound frequency created by the folds in our outer ears.  Spectral shape cue: change in a sound’s frequency envelope created by the pinnae. Auditory Scene Analysis: The process of identifying specific sound producing objects from a complex set of sounds from different objects at varying and overlapping frequencies  Auditory system uses a number of heuristic rules to determine which frequencies go with other frequencies A. Temporal Segregation: the process whereby sounds that are linked in time are grouped together, whereas sounds that are not correlated with one another are not grouped together. B. Spatial Segregation: The process whereby sounds that are coming from the same location are grouped together, whereas sounds that are coming from different locations are not grouped together C. Spectral Segregation: The process whereby sounds that overlap in harmonic structure are grouped together, whereas sounds that do not overlap in harmonic structure are not grouped together a. Harmonic coherence: when frequencies present in the environment resemble the possible pattern of a fundamental frequency and higher harmonics.


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