Unit 7 - The Hearing Brain Flashcards
Where does sound originate from? How does it manifest itself?
Sound originates from the motion or vibration of an object (such as the vocal cords)
It manifests itself in the surrounding medium, usually air, as changes in pressure in which molecules are squeezed together and stretched apart
How is the sensitivity to temporal information for hearing versus seeing? How about the sensitivity to spatial information?
Hearing has better temporal and worse spatial sensitivity than seeing
What are pure tones?
Sounds with a sinusoidal waveform when pressure change is plotted against time
What is pitch? What characteristic of the sound wave is related to the pitch? What is it measured with?
The perceived property of sounds that enables them to be ordered from low to high
Its frequency
Hertz, or, vibrations per second
What is meant by loudness? To what interval of frequencies does the human auditory system respond to? What characteristic of the sound wave is related to loudness>
The perceived intensity of a sound
20 to 20,000 Hz
Its amplitude
What type of features are pitch and loudness, and what types of features are frequency and intensity?
Pitch and loudness are psychological properties
Frequency and intensity are physical properties
What is the fundamental frequency?
The lowest frequency component of a complex that sound that determines the perceived pitch
E.g., 220 Hz in a piano note consisting of sinusoids 220 Hz, 440 Hz, and 660 HZ
What is the Missing Fundamental Phenomenon?
If the fundamental frequency of a complex sound is removed, then the pitch is not perceived to change (the brain reinstates it)
E.g., 440 Hz, 660 Hz, 880 Hz
What is timbre? Is timbre a psychological or physical property?
The perceptual quality of a sound that enables us to distinguish between different musical instruments
Psychological characteristic
What are the three main parts of the ear?
The outer, middle and inner ear
What are some components of the outer ear? What can they do?
The pinnae (ear lobes) and the auditory canal
Amplify certain sounds to locate sound sources
What does the middle ear do?
Convert airborne vibrations to liquid-borne vibrations
What is the cochlea?
Part of the inner ear that converts liquid-borne sound into neural impulses
What is the basilar membrane? How does it create neural signals?
A membrane within the cochlea containing tiny hair cells linked to neural receptors
Sound induces mechanical movement of hair cells, which induce a flow of ions that initiates neural activity (neurotransmitter release)
What do the hairs of the basilar membrane differentiate and what do they not?
Differentiate between different frequencies of sound
Not between different locations of sound source
What is the primary auditory cortex A1? What regions is it surrounded by?
The main cortical area to receive auditory-based thalamic input
Belt and parabelt regions
What is the belt region?
Part of the secondary auditory cortex with many projections from the primary auditory cortex
What is the parabelt region?
Part of the secondary auditory cortex receiving projections from the adjacent belt region
What does damage to the primary auditory cortex lead to? What does it not?
Partial deafness, problems in identifying and locating sounds
Complete deafness
What is tonotopic organisation?
The principle that sounds close to each other in frequency are represented by neurons that are spatially close to each other in the brain
What frequencies do central regions of the primary auditory cortex respond to? How about outer regions?
Central regions respond to lower frequencies
Outer regions to higher frequencies
What is sparse scanning?
In fMRI, a short break in scanning to enable sounds to be presented in relative silence (away from the loud sounds of the fMRI scans)
In sound processing, is there evidence of hierarchical processing of auditory feature information, i.e., earlier cortical regions coding for more simple features while later cortical regions coding more complex information?
How is this evidenced in humans?
Yes
Core regions respond to pure tones while surrounding belt and parabelt regions respond to noise bands and vocalisations, which are characterised by sudden shifts in frequency
What are three aspects of sound according to which different neurons respond / do not respond? Are there neurons which combine these features?
Frequency, loudness, spatial locations
Yes, for instance, there are neurons who respond to sounds with specific loudnesses and spatial locations.
What is the distinction between “what” and “where” in sound?
The content of the sound vs where the sound is coming from
Which region is specialised for “what” and which region is specialised for “where”? What routes could these act as the starting points for?
Anterior belt region for “what”, posterior belt region for “where”
Ventral route through temporal lobes for “what”, dorsal route through parietal lobes for “where”
Which of the routes divides into a “how” route specifying how sounds could be recreated?
The dorsal “where” route
What is an inter-aural difference? What can this be used for?
The difference in timing between a sound arriving in each ear
Localising sounds
What is the interaural intensity difference? What can this be used for?
The difference in loudness between a sound arriving in each ear
Localising sounds
What is the head-related transfer function (HRTF)? What can this be used for?
An internal model of how sounds get distorted by the unique shape of one’s own ear and head
Localising sounds in both left-right and top-down directions
What is the planum temporale? What is its relation to the HRTF?
A part of the auditory cortex that integrates auditory information with non-auditory information, e.g., to enable sounds to be separated in space
Believed to be the part responsible for applying the HRTF to auditory information
Why is auditory memory important?
Since auditory objects tend to not hang around enough to be reinspected
What is auditory stream segregation? What is this hypothesised to be used by?
The division of a complex auditory signal into different sources or auditory objects (such as pitch, melody, instrumentation or location)
Auditory memory systems
What is Mismatch Negativity (MMN)? What is it evidence? Is this component also found for complex auditory differences?
An ERP component that occurs when an auditory stimulus deviates from previously presented auditory stimuli
Auditory stream segregation
Yes, it is, which means that auditory memory must code rather abstract properties of auditory stimuli
What is the cocktail party problem?
The problem of attending to a single auditory stream in the presence of competing streams (with different acoustic and spatial properties)
E.g., attending to one person’s voice in a noisy room of other voices
What is the contribution of the parietal lobes in auditory processing?
Play a general role in attention and binding, e.g., in minimising the cocktail party problem
What type of hemispheric specialisation exists related to auditory processing? Which side is better for which?
Timing (left-hemispheric dominant) versus pitch-related information (right-hemispheric dominant)
What is pitch organisation, and what is temporal organisation?
Pitch organisation includes pitch relations between notes
Temporal organisation includes rhythm (tempo of beats) and metre (repeating accentuated beats)
What is amusia?
An auditory agnosia in which music perception is affected more than the perception of other sounds
What are the two main distinctions made by the basic cognitive model of music processing made by Peretz and Coltheart (2003)? What is the main evidence for this model?
Processes shared between music and speech
vs
Processes that are potentially specific to music
and
Pitch organisation vs temporal organisation
Amusia
What was patient CN’s case? Where was patient CN’s damage?
A non-musician who could identify information from speech (which requires analysis of pitch contours) but could not identify previously familiar tunes
Bilateral temporal lobe
Impairments in what type of memory affect the ability to recognise previously familiar tunes?
Semantic memory
Can there be damage to identifying rhythm independently of identifying pitch? Which two systems are primarily involved in rhythm perception and production?
Yes, there can be.
Auditory and motor systems
What is tone-deafness, or congenital amusia? What can it be caused by?
A developmental difficulty in perceiving pitch relationships, primarily for musical sounds
Right-hemisphere abnormalities in the auditory cortex
What is prosody?
Changes in the stress pattern of speech (e.g., to add emphasis), the rhythm of speech, or the intonation (e.g., rising/falling pitch to indicate questioning or sarcasm)
What are the primary differences in pitch processing in speech vs music?
In speech, pitch is processed on a continuous scale, with relative changes being of great importance
In music, pitch is arranged into discrete notes, and a small change in pitch can be perceived as wrong
What is melody? What is tonal encoding? What is musical syntax?
Patterns of pitch over time
Determining the set of possible notes for a given melody
The rule-like aspect of music which renders some notes more probable at certain points in a memory than others
What have been hypothesised to be the three routes involved in voice processing?
First involved in recognising speaker identity
Second involved in extracting affective information
Third involved in extracting speech content
What area contains regions that respond to vocal sounds more than non-vocal sounds of comparable acoustic complexity?
Bilateral superior temporal sulcus
At what stage of processing does the brain treat speech sounds differently from other kinds of auditory stimuli?
Along the “what“ route of the temporal lobes
What is pure word deafness? Damage to which area causes it?
A type of auditory agnosia in which patients are able to identify environmental sounds and music, but not speech
Damage to the left hemisphere
What is a spectrogram?
Plots the frequency of sound (on the y-axis) over time (on the x-axis) with the intensity of the sound represented by how dark it is
What are phonemes?
Minimal contrastive units of spoken language
What are allophones?
Different spoken/acoustic renditions of the same phoneme
E.g., the “p” phoneme in “pin” vs in “peg”, with a greater expulsion of air during “pin”
What are formants?
Horizontal stripes on the spectrogram produced with a relatively free flow of air (e.g., by vowels)
What is voicing? How is this seen on a spectrogram?
Vibration of the vocal cords that characterises the production of some consonants (e.g., saying “zzzz”)
Series of closely spaced vertical lines
How do vowels and consonants vary in terms of the flow of air?
Vowels are produced with a relatively free flow of air, whilst consonants typically place more constriction on the flow of air
What is categorical perception? How is it used by the brain?
The fact that continuous changes in the input are mapped onto discrete percepts
Used by the brain to deal with variability in the acoustic input
What is coarticulation? What does it aid?
The production of one phoneme is influenced by the preceding and proceeding phonemes
Categorical perception
What is the motor theory of speech perception? What type of neuron strengthens this theory? Do lesions to areas with such neurons harm speech perception?
A theory that the store sounds, the auditory signals are matched onto motor representations for producing one’s own speech
Mirror neurons
No, they do not
When are motor regions most used for speech perception? What are they also important for?
When the auditory signal is uncertain
Perceptual learning
What is the arcuate fasciculus? What is its function?
A white matter bundle that connects the temporoparietal region to the frontal lobes
Connects the parietal and frontal parts of the auditory “how” pathway
What is the function of the “how” pathway? What is it considered the neuroanatomical basis of?
Learning and memory of auditory-verbal material, including both long-term learning and short-term retention
The phonological loop
What types of phrases does the “how” route help repeat?
Verbatim repetition of longer sequences and meaningless material
What is the McGurk illusion? Why is it believed to arise?
An auditory percept derived from a fusion of mismatching heard speech and seen speech
Multisensory perception of speech, or from activating the motor system for speech production