Auditory agnosia restricted to environmental sounds following cortical deafness and generalized auditory agnosia

We encountered a case of auditory agnosia restricted to environmental sounds, which was associated with the development of bilateral subcortical lesions after suffering a bilateral putaminal hemorrhage. The patient had a history of a putaminal hemorrhage on her left side without any major disability. Three years later, she suffered a putaminal hemorrhage on the other side. The clinical picture started with cortical deafness, then changed to generalized auditory agnosia for verbal and environmental sounds, and finally developed into auditory agnosia confined to the perception of environmental sounds. Her errors in a test of sound recognition were discriminative rather than associative in nature. Neuro-radiological examinations revealed bilateral subcortical lesions involving the fibers from the medial geniculate body to the temporal lobes after bilateral putaminal hemorrhage. This case suggested that the subcortical lesion involving bilateral acoustic radiation could cause either cortical deafness, auditory agnosia of all sounds, or auditory agnosia restricted to environmental sounds.     

Auditory sound agnosia without aphasia following a right temporal lobe lesion

A 55-year-old right-handed man showed inability to recognize the meaning of non-verbal sounds without impairment of language comprehension after a cerebrovascular accident. His auditory acuity was intact and no other sign of agnosia, apraxia or aphasia was detectable. His errors on a test of sound recognition were acoustic rather than semantic. Brain CT scan showed a small lesion in the posterior part of the right temporal lobe. This case suggests that auditory sound agnosia without language disorder can ensure a lesion confined to the right hemisphere, and that the deficit is discriminative rather than associative in nature.     

Dysprosody associated with environmental auditory sound agnosia in right temporal lobe hypoperfusion--a case report]

A 60-year-old right-handed man showed dysprosody and agnosia for environmental sounds. His mother tongue was Japanese, and he could not speak foreign languages. He gradually developed difficulty in speaking from the age of 57 years, speaking non-native Japanese. In addition, he often complained of difficulty in hearing sounds, but audiometry showed no abnormalities. At the age of 60 years, the standard language test of aphasia showed no abnormalities in repetition, verbal comprehension, or reading, suggesting the absence of aphasia. However, in speaking, marked abnormality in rhythm, and occasional lack of postpositional particles and syllable-stumblings were observed. Writing was almost accurate, but a few grammatical errors were observed in speaking were observed. There were no cerebellar symptoms, pyramidal signs, pathologic reflexes, or abnormalities in phonation-related organs. Though the recognition of verbal sounds was maintained, impairment in the recognition of non-verbal sounds was observed. An environmental sound perception test showed correct answers only in 8 of 21 non-verbal sound sources (such as a car starting, glass breaking and so on), suggesting agnosia for environmental sounds. He insisted that the difficulty in perception was due to hearing impairment. However, re-examination with an increase in the sound volume showed similar results. He had no inconvenience in daily life and was not aware of agnosia for environmental sounds. He could recognize and differentiate sounds he heard once. His intelligence was normal, and neither apraxia nor frontal lobe symptoms were observed. MRI of the brain revealed slight atrophy of the right temporal lobe. Cerebral blood flow SPECT showed decreased blood flow from the superior temporal gyrus to the area around the arcuate fasciculi in the right temporal lobe. We considered that the lesion responsible for environmental auditory sound agnosia was present in the area around the secondary auditory area of the right temporal lobe and this patient differed from slowly progressive aphasia characterized by decreased blood flow in the left temporal lobe. Although the pathological process occurring in the area of hypoperfusion remained unclear, early stage of some degenerative disorders was more likely than cerebrovascular disease.     

Auditory agnosia with relative sparing of speech perception

We report a case of auditory agnosia in which the initial clinical picture began with generalized auditory agnosia for verbal and non verbal sounds, but rapidly changed to a selective auditory agnosia confined to the perception of non verbal sounds. CT scanning and MRI did not demonstrate cortical or subcortical damage, except for bilateral ventricular enlargement. The patient was submitted to audiological investigations including physical and psychoacoustic studies. Deficits were revealed during the decay and loudness discrimination test, but no temporal auditory acuity deficit was observed. The results of these studies are discussed in relation to the clinical picture. Also the dissociation between verbal perception and non verbal perception is discussed.     

Non-verbal auditory agnosia with EEG abnormalities and epilepsy; an unusual case of Landau-Kleffner syndrome]

A case of unusual Landau-Kleffner syndrome was reported. She was an 8 year-old girl and showed non-verbal agnosia, diffuse EEG abnormalities and convulsions. Her responses to both verbal and non-verbal sounds remained inconsistent and unstable. When a continuous spike-wave complexes on EEG was detected, she paid no attention to any sound in spite of her fair consciousness. Auditory brainstem response and magnetic resonance imaging of her brain were normal. Auditory agnosia was correlated well with EEG abnormalities, and valproic acid and clonazepam were effective for EEG improvement. After the EEG improvement, clinical responses to sounds recovered well; firstly she could pay attention to sounds and then she could distinguish between verbal and non-verbal sounds. Finally, she could speak a few words after the learning letters.     

Neurologic, audiologic, and electrophysiologic sequelae of bilateral temporal lobe lesions

A 67-year-old woman with demonstrated intact peripheral and brain-stem auditory pathways presented with sudden deafness secondary to sequential bilateral temporal lobe infarcts. Initial examination revealed no behavioral response to sounds and a mild Wernicke's aphasia. Hearing gradually returned but auditory agnosia persists. Changes seen on the computed tomographic scan and the middle latency auditory evoked response over a seven-month period were analyzed and suggest that the peak component of the middle latency response arises from Heschl's gyrus.     

Impaired recognition of meaningful sounds in Alzheimer's disease

We studied recognition of meaningful nonverbal sounds using a sound-picture matching test in 18 patients with senile dementia of the Alzheimer type (SDAT) and 19 age-matched controls. A significant impairment of sound recognition was found in the SDAT group, consistent with auditory sound agnosia. Although sound recognition performance correlated significantly with auditory verbal comprehension scores, a sound recognition defect was also identifiable in the subgroup of patients with SDAT who had normal verbal comprehension. Qualitative analysis of sound recognition errors revealed that nonaphasic patients with SDAT made predominantly acoustic errors, whereas semantic errors were found almost exclusively in aphasic patients. These findings suggest that the auditory sound agnosia of patients with SDAT may be subdivided into perceptual-discriminative and semantic-associative types.     

A case of auditory agnosia with the lesion of bilateral auditory radiation

A 53-year-old man showed central auditory disturbance with recurrent cerebral hemorrhage. At his acute stage he had deafness and auditory anosognosia. Two or three months later, there was no deafness and auditory anosognosia, but he could not comprehend words, environmental sounds and music. Auditory brainstem responses showed no peripheral or brainstem damage, and the lesion of bilateral auditory radiation was detected by MRI. His auditory agnosia did not improve over one and a half year. There is no report like such permanent auditory agnosia with the lesion of bilateral subcortical temporal lobe.     

Functional neuroanatomy of non-verbal semantic sound processing in humans

Summary. Environmental sounds convey specific meanings and the neural circuitry for their recognition may have preceded language. To dissociate semantic mnemonic from sensory perceptual processing of non-verbal sound stimuli we systematically altered the inherent semantic properties of non-verbal sounds from natural and man-made sources while keeping their acoustic characteristics closely matched. We hypothesized that acoustic analysis of complex non-verbal sounds would be right lateralized in auditory cortex regardless of meaning content and that left hemisphere regions would be engaged when meaningful concept could be extracted. Using H₂¹⁵O-PET imaging and SPM data analysis, we demonstrated that activation of the left superior temporal and left parahippocampal gyrus along with left inferior frontal regions was specifically associated with listening to meaningful sounds. In contrast, for both types of sounds, acoustic analysis was associated with activation of right auditory cortices. We conclude that left hemisphere brain regions are engaged when sounds are meaningful or intelligible.     

Right unilateral auditory agnosia following left lenticular hemorrhage

A 33-year old patient who had had left lenticular hemorrhage presented with an inability to understand with the right ear oral language and, in a less dramatic way, nonverbal sounds. This unilateral auditory agnosia was first associated with a right motor underutilization and right motor, sensitive, visual and auditive extinctions. Speech discrimination scores were 100% with the left ear and 15% with the right ear, even less in dichotic conditions. Tonal audiogram, as well as early and late components of the auditory evoked potentials were normal. Cerebral regional perfusion and metabolism were impaired over the left parietotemporal area. There was severe hypoactivation of the left hemisphere with right monaural verbal stimulations. Rehabilitation consisting of non-specific attention tasks and repetitions of words reaching only the right ear was undertaken 15 months after the stroke. The oral language comprehension improved, as did the left hemisphere activation, and the extinction phenomena disappeared, except for the auditory one. The unilaterality of the auditory agnosia could be due, in part, to a peculiar physiological processing in this patient, such as poor performance of his right ipsilateral auditory pathway which could be improved with practice. A striatal lesion could induce a spatial hemi-inattention as reflected by the multimodal extinction in this case. Besides, a lack of selective activation for verbal stimulation of the left hemisphere is suggested.     

The assessment of auditory function in CSWS: Lessons from long-term outcome

In Landau-Kleffner syndrome (LKS), the prominent and often first symptom is auditory verbal agnosia, which may affect nonverbal sounds. It was early suggested that the subsequent decline of speech expression might result from defective auditory analysis of the patient's own speech. Indeed, despite normal hearing levels, the children behave as if they were deaf, and very rapidly speech expression deteriorates and leads to the receptive aphasia typical of LKS. The association of auditory agnosia more or less restricted to speech with severe language decay prompted numerous studies aimed at specifying the defect in auditory processing and its pathophysiology. Long-term follow-up studies have addressed the issue of the outcome of verbal auditory processing and the development of verbal working memory capacities following the deprivation of phonologic input during the critical period of language development. Based on a review of neurophysiologic and neuropsychological studies of auditory and phonologic disorders published these last 20 years, we discuss the association of verbal agnosia and speech production decay, and try to explain the phonologic working memory deficit in the late outcome of LKS within the Hickok and Poeppel dual-stream model of speech processing.     

Pure word deafness after bilateral primary auditory cortex infarcts

In pure word deafness, comprehension and repetition of speech are impaired, but reading, writing, and spontaneous speech are preserved. Pure word deafness is distinguished from generalized auditory agnosia by the preserved ability to recognize environmental sounds. We examined a patient with pure word deafness associated with bilateral infarctions of the primary auditory cortex, who could use auditory affective intonation to enhance comprehension. The primary auditory cortex seems to be essential for comprehending speech, but comprehension of nonverbal sounds and affective prosody may be mediated by other cerebral structures such as the auditory association cortex.     

Auditory agnosia caused by a tectal germinoma

The authors describe a patient with auditory agnosia caused by a tectal germinoma. Despite having normal audiometric tests, the patient failed to recognize words and musical characters. On head MRI, the inferior colliculi were infiltrated by tumor. Neuropsychological tests revealed severe impairment in recognition of environmental sounds and words, defective musical perception, and stop consonant-vowel discrimination. Inferior colliculus may play a role in the analysis of sound properties.     

Audition of laughing and crying leads to right amygdala activation in a low-noise fMRI setting

Adequate behavioral responses to socially relevant stimuli are often impaired after lesions of the amygdala. These impaired behavioral responses in particular concern the recognition of facial, and sometimes vocal, expressions of fear. Using low-noise functional magnetic resonance imaging (fMRI) in combination with controlled sound delivery, we investigated how the amygdala, insula and auditory cortex are involved in the processing of affective non-verbal vocalizations (laughing, crying) in healthy humans. The same samples of male and female laughing and crying were presented in two different experimental conditions: self-induction of the corresponding emotions while listening, and detection of artificial pitch shifts in the same stimuli. Both conditions led to bilateral activation of the amygdala, insula and auditory cortex with a right-hemisphere advantage in the amygdala, and larger activation during laughing than crying in the auditory cortex with a slight right-hemisphere advantage for laughing, both likely due to acoustic stimulus features. The results show that amygdala activation by emotionally meaningful sounds like laughing and crying is independent of the emotional involvement, suggesting the pattern recognition aspect of these sounds is crucial for this activation. This aspect was revealed by a low-noise fMRI protocol which presumably minimized confounding effects of stressful high-noise fMRI.     

Deficits in language-mediated mental operations in patients with schizophrenia.

We found previously that a subgroup of schizophrenic patients who passed screening tests of attentional competence showed memory deficits on word memory tasks, but were comparable with controls on tone memory tasks. To better understand the nature of language-specific memory deficits in this subgroup of patients, the present experiment was designed to bypass early perceptual processing of verbal material and determine if patients continue to show impaired performance on verbal memory tasks.Patients who passed the screening tests ('discriminator' patients; DSz) received four serial position tasks. In two, familiar sounds or line drawings were presented and subjects were required to remember the word associated with each stimulus item. In the other two, subjects received hard-to-label auditory and visual stimuli (birdsongs or snowflakes).DSz patients showed large memory deficits compared with controls when required to remember words associated with the familiar sounds or drawings, providing clear evidence of deficits in verbal memory processes independent of sensory processing of verbal stimuli. The interaction between diagnosis and labeling was highly significant, confirming that these patients have particular difficulty with verbal as opposed to non-verbal memory. This was particularly striking on the auditory tests where two patients out-performed all controls on the birdsong test, but were below all controls on the easy-to-label sounds test. The verbal memory tests were easier than the non-verbal memory tests for controls, thus deconfounding task difficulty and deficit specificity.     

Approaches to therapy of auditory agnosia

In a 41-year-old stroke patient with bitemporal brain damage, we found severe signs of auditory agnosia 6 months after onset. Recognition of environmental sounds was extremely impaired when tested in a multiple choice sound-picture matching task, whereas auditory discrimination between sounds and picture identifications by written names was almost undisturbed. In a therapy experiment, we tried to enhance sound recognition via semantic categorization and association, imitation of sound and analysis of auditory features, respectively. The stimulation of conscious auditory analysis proved to be increasingly effective over a 4-week period of therapy. We were able to show that the patient's improvement was not only a simple effect of practicing, but it was stable and carried over to nontrained items.     

A case of deaf–mutism as an expression of pure word deafness: neuroimaging and electrophysiological data

We report a case of pure word deafness, clinically expressed as deaf–mutism in a 17-year-old girl, who was affected from encephalitis when she was 18 months old and hadn't acquired language skills. Actually, physical examination revealed buccolingual apraxia and absence of spontaneous speech, auditory comprehension, repetition and denomination, whereas perception of non-verbal sounds was preserved. The seven waves of brainstem auditory evoked responses (BAER) were present with normal latencies; middle latency responses (MLR) were also normal. Magnetic resonance imaging (MRI) showed bilateral temporoparietal lesions. This case proves that lesions which may give rise to word deafness, when they occur in prelingual age, can determine a peculiar deafmutism clinical picture.     

Processing of environmental sounds in schizophrenic patients: disordered recognition and lack of semantic specificity

The recognition of environmental sounds is an important feature of higher auditory processing and essential for everyday life. The present study aimed to investigate the potential impairment of this mental function in schizophrenia. This work on immediate sound recognition is complementary to recent studies on auditory linguistic processing. Fifteen schizophrenic patients and 30 control subjects were asked to identify 43 complex environmental sounds from different categories and rate their familiarity when na?ve to the sounds. In consecutive experiments, patients and control subjects rated the sounds according to emotional valence and arousal, as well as imageability. In both groups, correct identification of non-verbal sounds was highly associated with familiarity. Statistical analysis by group demonstrated a significantly higher error rate in identifying sounds in patients suffering from schizophrenia compared to healthy control subjects. In contrast, the affective recognition of the complex sounds was preserved in the schizophrenic patients. These results suggest a disturbance of higher-order, auditory mnemonic processing in schizophrenic patients in the non-linguistic domain. We discuss their abnormal responses in the context of recent theories of auditory physiological and semantic processing deficits in schizophrenia.     

Are auditory-verbal hallucinations associated with auditory affective processing deficits?

We investigated whether the presence of auditory-verbal hallucinations (AVH) was associated with impaired auditory affect perception. Controls, schizophrenia patients with a history of AVH (AVH) or with no history of AVH (NAVH) completed four perceptual auditory affect tasks. The tasks used either non-verbal/non-semantic or verbal/semantic stimuli. AVH patients showed significant impairments on a non-verbal task requiring the recognition of environmental sounds, this was particularly so for the affective stimuli and not the neutral valance stimuli. Thus, confirming auditory affect deficits in AVH patients. AVH patients also showed reduced right ear performance on a dichotic listening task. Conversely, both patient groups showed impairments on auditory affect tasks that used verbal/semantic stimuli; as these tasks require proficient semantic processing we speculated that significant semantic impairments in schizophrenia masked the additional auditory affect deficits present in the AVH group. The overall results support the notion that patients with AVH have increased liability for auditory affect perception deficits.