disorders of auditory processing 1 day 20 – oct 14, 2013 brain & language ling...

DISORDERS OF AUDITORY PROCESSING 1DAY 20 – OCT 14, 2013

Brain & Language

LING 4110-4890-5110-7960

NSCI 4110-4891-6110

Harry Howard

Tulane University

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Course organization• The syllabus, these slides and my recordings are

available at http://www.tulane.edu/~howard/LING4110/.• If you want to learn more about EEG and neurolinguistics,

you are welcome to participate in my lab. This is also a good way to get started on an honor's thesis.

• The grades are posted to Blackboard.

10/14/13 Brain & Language - Harry Howard - Tulane University

http://www.tulane.edu/~howard/LING4110/

REVIEW

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An alternative: the TRACE II model


DISORDERS OF AUDITORY PROCESSINGIngram §8


Brain & Language - Harry Howard - Tulane University 610/14/13

Reasons for delay in development of models of auditory processing• Neuroanatomical differences between the visual and auditory

systems• the auditory system has a neuroanatomical redundancy built into it: it

transmits information about sound in all parts of space to both hemispheres, rather than to one• result: disorders of auditory processing are quite rare• dichotic listening tasks are less informative than visual-half field presentation

• diagnostic difficulty caused by the close relationship between speech comprehension and auditory processing

• Terminological confusions relating to auditory processing disorders• “verbal processing” can conflated with “auditory processing”

• Technical factors that have made auditory stimuli more difficult to study than visual stimuli

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The central auditory pathwayNote that the subcortical pathway is rather complex.


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Another version


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A1, A2, A3A1 = core

A2 = belt

A3 = parabelt


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A1Tonotopic mapping of organ of Corti (in the cochlea) to area A1


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Temporal lobe


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Linguistic model, Fig. 2.1 p. 37


Discourse model

SyntaxSentence prosody

MorphologyWord prosody

Segmental phonologyperception

Acoustic phonetics Feature extraction

Segmental phonologyproduction

Articulatory phonetics Speech motor control

INPUT

SEMANTICS

Sentence level

Word level


The Broca-Wernicke-Lichtheim model (of the LH)


Disorders of cortical auditory processing

• Cortical deafness• Auditory agnosia• Speech agnosia or pure word deafness• Phonagnosia• Phonological retrieval disorder


Cortical deafness• Wernicke and Friedlander (1883) described a patient who was unable

to hear any sounds, but had no apparent damage to the hearing apparatus and labeled the disorder cortical deafness.

• One review of the literature, reported “only 12 cases of significant deafness due to purely cerebral pathology” (Graham, Greenwood & Lecky, 1980:43)

• Identifying cases of cortical deafness has proved to be difficult for several reasons:• patients rarely suffer bilateral lesions in the critical region of auditory

cortex in the lateral temporal lobes;• some patients believed to suffer from cortical deafness may, in fact,

suffer from auditory inattention or neglect;• cortical deafness is often transient, resolving to a less severe, or more

specific, auditory processing disorder such as pure word deafness or auditory agnosia.

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Agnosia

Vision Audition

Can not recognize objects in general visual agnosia auditory agnosia

Can not recognize linguistic objects

alexia (word blindness)

speech agnosia (pure word deafness)

Can not recognize human objects

prosopagnosia(face blindness) phonagnosia


An impairment in which a patient fails to recognize a stimulus in a sensory modality, although perception in the modality is unimpaired. By “perception”, we mean the subcortical processing of the modality.


Auditory agnosia• It is best defined as an inability to recognize sounds independent of any deficit in processing spoken language.• at times, it has been replaced by a more general definition

referring to a deficit involving any type of auditory stimuli.

• It dates back to Freud (1891), but the first case of ‘pure’ auditory agnosia appears to have been reported only thirty years ago (Spreen et al., 1965). • They presented a patient who was severely impaired at

identifying a variety of sounds such as coughing, whistling and a baby crying, but showed no evidence of impaired speech comprehension.

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Speech agnosiaPure word deafness, auditory-verbal agnosia

• Kussmaul (1877) coined the term “pure word deafness” to refer to an inability to comprehend spoken words despite intact hearing, speech production and reading ability. • One patient complained that speech sounded “like a great noise all the

time . . . like a gramophone, boom, boom, boom, jumbled together like foreign folks speaking in the distance”.

• Another said: “I can hear you talking but I can’t translate it”.• Examiner: What did you eat for breakfast?• Patient: Breakfast, breakfast, it sounds familiar but it doesn’t speak to me.

(Obler & Gjerlow 1999:45)• The experience of speech appears to undergo a qualitative change,

and some word deaf patients cannot judge the length of a word.• However, some patients appear able to extract information about the

speaker from their voice despite being unable to comprehend the spoken message …• i.e., sex, age, region of origin, or affective information.

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Phonagnosia• An impairment in the ability to recognize familiar voices, while being

unimpaired on other auditory abilities. (Van Lancker and Canter 1982)• Subjects were asked to identify which of four names or faces matched a

particular famous voice.• >> Just as prosopagnosia reflects an impairment in the ability to recognize

familiar faces.• Subsequent research produced evidence for a double dissociation

between memory for familiar voices and the ability to discriminate between unfamiliar voices: • One group of patients performed normally on the discrimination task but

was impaired on the memory task, • whereas another group of patients performed normally on the memory

task, but was impaired on the discrimination task.• >> Prosopagnosia has a similar double dissociation.

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SummaryNon-speech

sounds Voices Speech Cause

Cortical deafness ✖ ✖ ✖ bilateral lesions to A1

Auditory agnosia ✖ ✔ ✔ damage to feature

detectors in A2 & A3

Pure word deafness

✔ ✔ ✖damage to phonetic feature detectors or speech motor loop

Phonagnosia ✔ ✖ ✔damage to inferior and lateral parietal regions of the RH

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Optic aphasia• A patient CANNOT name an object presented visually,

• but the patient CAN …• name the object from a verbal description,• describe the function of the object, or• sort pictures of objects into categories,

• so it is not visual agnosia.• Cause: impairment of pathway from visual object

perception to semantic representation• the object’s semantic representation can be activated only

enough for basic tasks, such as sorting, but not enough for naming.

NEXT TIMEFinish Ingram §8.

☞ Go over questions at end of chapter.


disorders of auditory processing 1 day 20 – oct 14, 2013 brain & language ling...

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