Neuropsychological evidence for "word-meaning deafness" in a Spanish-speaking patient

Auditory agnosia

Auditory agnosia refers to impairments in sound perception and identification despite intact hearing, cognitive functioning, and language abilities (reading, writing, and speaking). Auditory agnosia can be general, affecting all types of sound perception, or can be (relatively) specific to a particular domain. Verbal auditory agnosia (also known as (pure) word deafness) refers to deficits specific to speech processing, environmental sound agnosia refers to difficulties confined to non-speech environmental sounds, and amusia refers to deficits confined to music. These deficits can be apperceptive, affecting basic perceptual processes, or associative, affecting the relation of a perceived auditory object to its meaning. This chapter discusses what is known about the behavioral symptoms and lesion correlates of these different types of auditory agnosia (focusing especially on verbal auditory agnosia), evidence for the role of a rapid temporal processing deficit in some aspects of auditory agnosia, and the few attempts to treat the perceptual deficits associated with auditory agnosia. A clear picture of auditory agnosia has been slow to emerge, hampered by the considerable heterogeneity in behavioral deficits, associated brain damage, and variable assessments across cases. Despite this lack of clarity, these striking deficits in complex sound processing continue to inform our understanding of auditory perception and cognition.

Rehabilitation of word deafness due to auditory analysis disorder

BACKGROUND

Word deafness refers to an inability to understand spoken words despite intact hearing. In a cognitive approach, word deafness could be explained by a deficiency at the lower perceptive level of the auditory process. The impairment of the auditory analysis system would explain a disorder of identification of speech sounds. Only few studies addressed rehabilitation of central auditory processing and have described therapy focused on phoneme discrimination.

OBJECTIVE

To determine whether a specific auditory analysis rehabilitation addressing phoneme discrimination and phoneme recognition may improve oral comprehension and communication.

METHOD

A single-case experimental design was used in a 65 year-old woman, with word deafness consecutive to a cerebral infarction which occurred 10 months before. Verbal naming, written expression and written comprehension were normal. Verbal comprehension, repetition and phoneme discrimination and recognition were impaired. In terms of cognitive model of auditory processing, the patient showed impairment of the auditory analysis system affecting verbal comprehension. A computerized rehabilitation of auditory analysis system was carried out in two consecutive tasks: phoneme discrimination and phoneme recognition. Errorless learning therapy was used, with a difficulty hierarchy practised from the easier to the most difficult phoneme and systematic visual cues which were progressively delayed and suppressed. This study tested the efficacy and the specificity of this therapy on the addressed tasks (phoneme discrimination and recognition), related tasks (oral comprehension and repetition), independent tasks (recognition of environmental sounds) and daily life (questionnaire).

RESULTS

The phoneme discrimination and recognition impairment was stable over 4 months before therapy. After therapy, phoneme discrimination (p < 0.001) and phoneme recognition (p < 0.0001) were improved. The improvement was specific to verbal sounds recognition, while non-verbal sounds recognition was unchanged. An improvement occurred for repetition (p < 0.05) and oral comprehension (p < 0.01). The communication disability decreased (p < 0.05).

CONCLUSION

In a case of word deafness, this study demonstrates not only the efficacy of a specific phoneme processing therapy but also its efficacy in the improvement of higher level of cognitive treatment such as oral comprehension and its transfer in daily life. The role of errorless therapy using systematic visual cues and difficulty hierarchy must be underlined.