DISORDERS OF AUDITORY PROCESSINGDAY 21 – OCT 15, 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.

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REVIEWand some new stuff

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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

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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.

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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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MORE ABOUT AUDITORY PROCESSINGIngram §8

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DORSAL VS. VENTRAL PROCESSING

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Dorsal ~ ventral?

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What's this?

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Dorsal ~ ventral streams in vision

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Hickok & Poeppel's model on the brain

Ventral

Dorsal

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Hickok & Poeppel’s localization of speech

• What/Ventral: sound-meaning interface• maps sound onto meaning• includes superior temporal

sulcus and ultimately the posterior inferior temporal lobe (portions of the middle temporal gyrus and inferior temporal gyrus)

• strongly lateralized to LH

• Where/Dorsal: auditory-motor interface• maps sound onto representations

of speech articulators• deep within the posterior aspect of

Sylvian fissure at the boundary between the parietal and temporal lobes: area Spt (Sylvian – parietal – temporal)

• the Spt projects to Broca's area, the motor face area, and a more dorsal premotor site

• less strongly lateralized to LH

Early speech perception involves auditory-responsive fields in the superior temporal gyrus (STG) bilaterally

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Hickok & Poeppel’s model in boxes

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Hickok & Poeppel’s model, an example

[kæt]

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Recall the TRACE II modelit may be a model of the dorsal stream

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MIRROR NEURONS

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Monkey see monkey do

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Imitation

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Mirror neuronsExample of a F5 mirror neuron selectively discharging …

(A) during observation of a grasping movement done by the experimenter and

(B) during monkey grasping movements.

Arrows denote the onset of the movement.

Six trials are shown for each condition.

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Monkey vs. human brains

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What does this have to do with speech?

• Transcranial magnetic stimulation (TMS) causes neurons in the neocortex under the site of stimulation to depolarize and discharge an action potential.

• If used in the primary motor cortex, it produces muscle activity referred to as a motor evoked potential (MEP) which can be recorded on electromyography.

• Ingram discusses two experiments that suggest that listening to speech activates speech-related motor cortices by enhancing LH MEPs under TMS > Hickok & Poepel's area Spt

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Disturbances in accessing the recognition lexicon

• Read Ingram.

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NEXT TIMEStart Ingram §9.

☞ Go over questions at end of chapter.

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