Spatial hearing loss
Encyclopedia
Spatial hearing loss, also known as spatial processing deficit, refers to a form of deafness that is an inability to use spatial cues, i.e. where a sound originates from in space, to understand speech in the presence of background noise. (Cameron & Dillon, 2007)/
arriving from other directions. Spatial hearing loss is not caused by peripheral hearing loss and is thought to occur in the auditory pathways of the brain. Research has shown spatial hearing loss to be a leading cause of central auditory processing disorder (CAPD) in children (Cameron & Dillon, 2008). Children with spatial hearing loss commonly present with difficulties understanding speech
in the classroom
. Spatial hearing loss is found in most people over 60 years of age, and is independent of other types of age related hearing loss.
Those with no spatial hearing loss are able to use the signals arriving at the two ears so that noise seems to originate from a different location to the speech being listened to. The central auditory processing of normal listeners is able to squelch out the noise and hear the speech through the use of signal phase and level differences. Those with spatial hearing loss are unable to make use of the phase and level cues, and era therefore unable to squelch out the noise.
The corpus collosum (CC) is the major route of communication between the two hemispheres. At maturity it is a large mass of white matter and consists of bundles of fibres linking the white matter of the two cerebral hemispheres. Its caudal portion and splenium contain fibres that originate from the primary and second auditory cortices, and from other auditory responsive areas. Transcallosal interhemispheric transfer of auditory information plays a significant role in spatial hearing functions that depend on binaural cues. Various studies have shown that despite normal audiograms, children with known auditory interhemispheric transfer deficits have difficulty localizing sound and understanding speech in noise.
The CC is relatively slow to mature with its size continuing to increase until the third decade of life. From this point it then slowly begins to shrink. LiSN-S SRT scores (see below) show that the ability to understand speech in noisy environments develops with age, is beginning to be adult like by 14 years and starts to decline by 40 years of age.
. The LiSN-S allows audiologists to measure how well a person uses spatial and pitch information to understand speech in noise. Inability to use spatial information has been found to be a leading cause of CAPD in children and is referred to as Spatial Hearing Loss or spatial processing disorder. (Cameron & Dillon, 2008)/
Test participants repeat a series of target sentences which are presented simultaneously with competing speech. The listener's speech reception threshold (SRT) for target sentences is calculated using an adaptive procedure. The targets are perceived as coming from in front of the listener whereas the distracters vary according to where they are perceived spatially (either directly in front or either side of the listener). The vocal identity of the distracters also varies (either the same as, or different to, the speaker of the target sentences) (Cameron & Dillon, 2007).
Performance on the LISN-S is evaluated by comparing listeners' performances across four listening conditions, generating two SRT measures and three "advantage" measures. The advantage measures represent the benefit in dB gained when either talker, spatial, or both talker and spatial cues are available to the listener. The use of advantage measures minimizes the influence of higher order skills on test performance (Cameron & Dillon, 2008). This serves to control for the inevitable differences that exist between individuals in functions such as language
or memory
.
Dichotic listening tests can be used to measure the interhemispheric transfer of auditory information. Dichotic listening performance increases with the development of the CC, peaking before the third decade. During middle age and older the CC reduces in size and dichotic listening becomes worse, primarily in the left ear. Dichotic listening tests typically involve two different auditory stimuli (usually speech) presented simultaneously, one to each ear, using a set of headphones. Participants are asked to attend to one or (in a divided-attention test) both of the messages.
. Mr Irving to work with a team led by Professor Charles Liberman at the Eaton Peabody Lab at MIT/Harvard university. This will follow up work done in 2006, by scientists working in the Oxford Auditory Neuroscience Group, at Oxford
in the UK.
The research will compare the performance of ferret
s which have had their OCB surgically removed with normal ferrets in the "ring of sound" noise device. Their theory is that the OCB, the Olivocochlear Bundle, which is a part of the brain that we know is a centre of feedback information being transmitted from the brain back to the ear is the part of the brain that is malfunctioning in some patients.
Simple amplification can also improves audibility and sonic localization. .
Overview
People with spatial hearing loss have difficulty processing speech that arrives from one direction while simultaneously filtering out noiseNoise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
arriving from other directions. Spatial hearing loss is not caused by peripheral hearing loss and is thought to occur in the auditory pathways of the brain. Research has shown spatial hearing loss to be a leading cause of central auditory processing disorder (CAPD) in children (Cameron & Dillon, 2008). Children with spatial hearing loss commonly present with difficulties understanding speech
Speech
Speech is the human faculty of speaking.It may also refer to:* Public speaking, the process of speaking to a group of people* Manner of articulation, how the body parts involved in making speech are manipulated...
in the classroom
Classroom
A classroom is a room in which teaching or learning activities can take place. Classrooms are found in educational institutions of all kinds, including public and private schools, corporations, and religious and humanitarian organizations...
. Spatial hearing loss is found in most people over 60 years of age, and is independent of other types of age related hearing loss.
Those with no spatial hearing loss are able to use the signals arriving at the two ears so that noise seems to originate from a different location to the speech being listened to. The central auditory processing of normal listeners is able to squelch out the noise and hear the speech through the use of signal phase and level differences. Those with spatial hearing loss are unable to make use of the phase and level cues, and era therefore unable to squelch out the noise.
Role of the corpus callosum
Many neuroscience studies have facilitated the development and refinement of a speech processing model. This model shows cooperation between the two hemispheres of the brain, with asymmetric inter-hemispheric and intrahemispheric connectivity consistent with the left hemisphere specialization for phonological processing.The corpus collosum (CC) is the major route of communication between the two hemispheres. At maturity it is a large mass of white matter and consists of bundles of fibres linking the white matter of the two cerebral hemispheres. Its caudal portion and splenium contain fibres that originate from the primary and second auditory cortices, and from other auditory responsive areas. Transcallosal interhemispheric transfer of auditory information plays a significant role in spatial hearing functions that depend on binaural cues. Various studies have shown that despite normal audiograms, children with known auditory interhemispheric transfer deficits have difficulty localizing sound and understanding speech in noise.
The CC is relatively slow to mature with its size continuing to increase until the third decade of life. From this point it then slowly begins to shrink. LiSN-S SRT scores (see below) show that the ability to understand speech in noisy environments develops with age, is beginning to be adult like by 14 years and starts to decline by 40 years of age.
Diagnosis
Spatial hearing loss can be diagnosed using the Listening in Spatialized Noise – Sentences test (LiSN-S), which was designed to assess the ability of children with central auditory processing disorder (CAPD) to understand speech in background noiseBackground noise
In acoustics and specifically in acoustical engineering, background noise or ambient noise is any sound other than the sound being monitored. Background noise is a form of noise pollution or interference. Background noise is an important concept in setting noise regulations...
. The LiSN-S allows audiologists to measure how well a person uses spatial and pitch information to understand speech in noise. Inability to use spatial information has been found to be a leading cause of CAPD in children and is referred to as Spatial Hearing Loss or spatial processing disorder. (Cameron & Dillon, 2008)/
Test participants repeat a series of target sentences which are presented simultaneously with competing speech. The listener's speech reception threshold (SRT) for target sentences is calculated using an adaptive procedure. The targets are perceived as coming from in front of the listener whereas the distracters vary according to where they are perceived spatially (either directly in front or either side of the listener). The vocal identity of the distracters also varies (either the same as, or different to, the speaker of the target sentences) (Cameron & Dillon, 2007).
Performance on the LISN-S is evaluated by comparing listeners' performances across four listening conditions, generating two SRT measures and three "advantage" measures. The advantage measures represent the benefit in dB gained when either talker, spatial, or both talker and spatial cues are available to the listener. The use of advantage measures minimizes the influence of higher order skills on test performance (Cameron & Dillon, 2008). This serves to control for the inevitable differences that exist between individuals in functions such as language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...
or memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....
.
Dichotic listening tests can be used to measure the interhemispheric transfer of auditory information. Dichotic listening performance increases with the development of the CC, peaking before the third decade. During middle age and older the CC reduces in size and dichotic listening becomes worse, primarily in the left ear. Dichotic listening tests typically involve two different auditory stimuli (usually speech) presented simultaneously, one to each ear, using a set of headphones. Participants are asked to attend to one or (in a divided-attention test) both of the messages.
Research
Deafness Research UK, awarded annual the 2007 Pauline Ashley Prize to UK researcher Sam Irving, of the MRC Institute for Hearing Research in NottinghamNottingham
Nottingham is a city and unitary authority in the East Midlands of England. It is located in the ceremonial county of Nottinghamshire and represents one of eight members of the English Core Cities Group...
. Mr Irving to work with a team led by Professor Charles Liberman at the Eaton Peabody Lab at MIT/Harvard university. This will follow up work done in 2006, by scientists working in the Oxford Auditory Neuroscience Group, at Oxford
Oxford
The city of Oxford is the county town of Oxfordshire, England. The city, made prominent by its medieval university, has a population of just under 165,000, with 153,900 living within the district boundary. It lies about 50 miles north-west of London. The rivers Cherwell and Thames run through...
in the UK.
The research will compare the performance of ferret
Ferret
The ferret is a domesticated mammal of the type Mustela putorius furo. Ferrets are sexually dimorphic predators with males being substantially larger than females. They typically have brown, black, white, or mixed fur...
s which have had their OCB surgically removed with normal ferrets in the "ring of sound" noise device. Their theory is that the OCB, the Olivocochlear Bundle, which is a part of the brain that we know is a centre of feedback information being transmitted from the brain back to the ear is the part of the brain that is malfunctioning in some patients.
Hearing aids
A spatial hearing aid can provide a direction of sound detection source for victims of spatial hearing loss.Simple amplification can also improves audibility and sonic localization. .
See also
- AudismAudismAudism is a term typically used to describe discrimination against deaf or hard of hearing people, although it could also be expanded to include anyone with a difference in hearing ability. This discrimination can occur in a number of forms in a range that includes both physical, cultural, and...
, discrimination against Deaf and hard-of-hearing people - Cocktail party effectCocktail party effectThe cocktail party effect describes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations. The effect enables most people to talk in a noisy place...
- Deafblind
- Hearing aidHearing aidA hearing aid is an electroacoustic device which typically fits in or behind the wearer's ear, and is designed to amplify and modulate sound for the wearer. Earlier devices, known as "ear trumpets" or "ear horns", were passive funnel-like amplification cones designed to gather sound energy and...
- National Association for the Deaf (NAD)
External links
- http://www.kcdhh.ky.gov/bulletin/SymposiumRegistration.pdf
- http://www.oticonusa.com/eprise/main/SiteGen/Uploads/Public/Downloads_Oticon/The_Hearing_Review/Hearing_Review_November_08.pdf
- http://www.enotes.com/topic/Spatial_hearing_loss
- http://www.4hearingloss.com/archives/2005/04/spatial_hearing.html
- http://books.google.co.uk/books?hl=en&lr=&id=wBiEKPhw7r0C&oi=fnd&pg=PA1&dq=Spatial+hearing+loss&ots=4Ilc2RcZ9g&sig=BUu2pow2wCGqL348iPgI-s_ug2k#v=onepage&q=Spatial%20hearing%20loss&f=false
- http://www.rxpgnews.com/hearingimpairment/UK_researcher_identifies_brain_region_responsible__5036_5036.shtml
- http://www.nal.gov.au