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Impaired mismatch negativity generation in prodromal subjects and patients with schizophrenia.

BACKGROUND: Mismatch negativity (MMN) specifically the response to tone duration deviants has consistently been shown to be reduced in schizophrenia suggesting dysfunction in auditory sensory memory. As part of a multidimensional approach to the early recognition of psychosis, MMN was investigated as a possible risk factor for later development of psychosis in subjects with a prodromal syndrome. Forty-three prodromal subjects, 31 neuroleptic-free inpatients with schizophrenia and 33 healthy controls were studied. A prodromal state was defined by a cluster 'Cognitive Disturbances' as defined by the 'Bonn Scale for the Assessment of Basic Symptoms' (BSABS), which was found highly predictive of first-episode schizophrenia. To elicit MMN, a three-tone auditory oddball paradigm with 10% 'duration deviants' and 10% 'frequency deviants' was used. RESULTS: MMN amplitudes to tone duration deviants were significantly reduced in the patients with schizophrenia compared to controls. The putatively prodromal subjects also showed a slight, though non-significant reduction of the MMN amplitude that was intermediate between normal controls and patients with schizophrenia, and with a larger within-group variance. CONCLUSION: These results support the view that abnormalities in temporal processing are particularly pronounced in patients with schizophrenia. Prodromal subjects are a heterogeneous group with regard to outcome and time until transition to a first psychotic episode. Follow-up of these putatively prodromal subjects will show whether MMN amplitudes further reduce over time in those developing psychosis and if a reduction is state-dependent.

Acoustic Stimulation↗

Auditory gating in schizophrenia: a pilot study of the precedence effect.

Individuals with schizophrenia are known to exhibit diminished auditory gating, as manifested by prepulse inhibition of the startle response and suppression of the P50 evoked potential. Those observations indicate that schizophrenics have deficits of inhibitory auditory processing. The precedence effect is a phenomenon in which inhibitory processing in the auditory system aids the localization of sound sources and segregation of speech in complex auditory environments. We tested the hypothesis that schizophrenic subjects would exhibit deficits in psychophysical tests of the precedence effect. The performance of 12 male medicated schizophrenic subjects was compared with that of 12 male comparison subjects. Schizophrenics and comparison subjects clearly demonstrated all three aspects of the precedence effect that were evaluated: echo suppression, buildup of echo suppression, and breakdown of echo suppression. In none of these aspects did the performance of schizophrenic subjects differ significantly from that of the comparison subjects. These findings suggest that abnormalities of auditory spatial processing and speech segregation are unlikely to contribute to the clinical pathology of schizophrenia.

Adult↗

Electroencephalographic and perceptual asymmetry differences between responders and nonresponders to an SSRI antidepressant.

BACKGROUND: Recent reports suggest the value of electroencephalographic and dichotic listening measures as predictors of response to antidepressants. This study examines the potential of electroencephalographic alpha asymmetry and dichotic measures of perceptual asymmetry as predictors of clinical response to 12 weeks of treatment with fluoxetine (Prozac). METHODS: Resting electroencephalography (eyes open and eyes closed) and dichotic listening with word or complex tone stimuli were assessed in depressed outpatients during a pretreatment period. RESULTS: Fluoxetine responders (n = 34) differed from nonresponders (n = 19) in favoring left over right hemisphere processing of dichotic stimuli. They also differed in their resting electroencephalographic alpha asymmetry, particularly in the eyes open condition. Nonresponders showed an alpha asymmetry indicative of overall greater activation of the right hemisphere than the left, whereas responders did not. The relationship between hemispheric asymmetry and treatment response interacted with gender, being evident among depressed women but not men. CONCLUSIONS: The results are consistent with the hypothesis that a characteristic tendency toward greater left than right hemisphere activation is associated with favorable response to fluoxetine, whereas the opposite hemispheric asymmetry predicts poor response.

Adolescent↗

Auditory neglect: what and where in auditory space.

A sound that we hear in a natural setting allows us to identify the sound source and to localise it in space. Several lines of evidence indicate that the two aspects are processed in anatomically distinct cortical networks. Auditory areas that are part of the What or Where processing streams have been identified recently in man and in non-human primates. Comparison between anatomical and activation studies suggests that processing within either stream can be modulated by specific attentional factors. Attending to auditory events can be affected in neglect. Bisiach et al. (1984) described systematic directional errors to the ipsilesional space, which was considered a manifestation of hemispatial neglect and interpreted as a disruption of the neural network providing the internal representation of egocentric space. The other manifestation of auditory neglect is contralesional extinction in dichotic listening condition (Heilman and Valenstein, 1972). Recently two types of auditory neglect have been described, one corresponding to a primarily attentional deficit associated with basal ganglia lesions and the other to distortions of auditory space representations associated with parieto-prefrontal lesions (Bellmann et al., 2001). Based on studies of sound detection and sound recognition following hemispheric lesions we argue that the two types of neglect correspond to disturbed processing in either the What or the Where stream.

Attention↗

Information transmission defect identified and localized in language learning impaired children by means of electrophysiology.

Children with language processing deficits have various learning impairments and poor scholastic performance. In 3-10% of all children a specific language processing deficit can be identified by the Sound Connecting Sub-Test of the Illinois Test of Psycholinguistic-Abilities (SC-ITPA). These children among which we drew our index group (AS-Group) suffer from the disability to recognize isolated sounds as parts of words. Following linguistic terminology this is known as an auditory sequential sound processing deficit (ASSPD) Eighteen children (AS-Group) and 21 controls (C-Group) were subjected to mapped P300 evoked potential analyses of cortical response to acoustic stimulation in the oddball paradigm. The data presented here show that there exists significant relation between the P300 amplitude reduction and ASSPD. The P300 amplitude decrease measured in the AS-Group is due to a reduced information transmission in accordance with Johnson's Triarchic Model of the P300 Amplitude. The cerebral structures involved in poor language processing are localized at the left temporo-parietal cortex. This supports the hypothesis that the underlying neuronal defect of ASSPD is localized in the language center and not in the auditory pathway. The P300 amplitude may serve as electrophysiological tool to identify ASSPD and to quantify the degree of improvement in the course of specific therapy.

Auditory Perception↗

Generalized auditory agnosia with spared music recognition in a left-hander. Analysis of a case with a right temporal stroke.

After a right temporoparietal stroke, a left-handed man lost the ability to understand speech and environmental sounds but developed greater appreciation for music. The patient had preserved reading and writing but poor verbal comprehension. Slower speech, single syllable words, and minimal written cues greatly facilitated his verbal comprehension. On identifying environmental sounds, he made predominant acoustic errors. Although he failed to name melodies, he could match, describe, and sing them. The patient had normal hearing except for presbyacusis, right-ear dominance for phonemes, and normal discrimination of basic psychoacoustic features and rhythm. Further testing disclosed difficulty distinguishing tone sequences and discriminating two clicks and short-versus-long tones, particularly in the left ear. Together, these findings suggest impairment in a direct route for temporal analysis and auditory word forms in his right hemisphere to Wernicke's area in his left hemisphere. The findings further suggest a separate and possibly rhythm-based mechanism for music recognition.

Aged↗

Comprehension of prosody in Parkinson's disease.

The evidence for a receptive prosodic loss in Parkinson's disease (PD) has remained inconclusive since the first reports in the early 1980s (Scott, Caird and Williams, 1984). The present study examined three aspects of comprehension in 11 PD patients and a group of age matched controls. Experiment 1 found no evidence of deficits in phonological discrimination or lexical access in the PD patients. Experiment 2 found that one patient (EA) was significantly impaired on a test of lexical stress discrimination. Experiment 3 examined the discrimination, comprehension and identification of utterance prosody. This experiment found that overall the PD patients were significantly impaired at the identification of utterance prosody. Patient TB was significantly worse than controls on the identification and comprehension of utterance prosody. The study has shown that PD patients can exhibit impairments in the comprehension of prosody and lexical stress. The evidence suggests that only some patients are impaired and the pattern of deficits can differ significantly.

Aged↗

Staring in the eye of auditory neglect: comments on 'gaze direction modulates auditory spatial deficits in stroke patients with neglect'.

In the current issue of Cortex, Pavani and colleagues show that directing gaze toward the contralesional hemifield significantly diminishes the auditory deficits associated with unilateral neglect. The authors suggest that this beneficial effect of gaze direction may arise due to the recruitment of crossmodal attentional links between audition and vision. A complementary interpretation of these findings is that directing gaze toward neglected sound sources encourages the recoding of auditory spatial location in a relatively preserved frame of reference, and that it is through this coordinate transformation process that awareness of auditory stimuli may be regained. Rehabilitation strategies aimed at recoding stimuli within relatively preserved reference frames may be a useful step forward in managing unilateral neglect.

Attention↗

Gaze direction modulates auditory spatial deficits in stroke patients with neglect.

We investigated the effects of eye position on auditory spatial deficits in four patients with left neglect and right-hemisphere damage, using three blocked gaze directions (35 degrees to the right, central, or 35 degrees to the left), while preventing any head-movement to ensure that initial auditory inputs remained constant regardless of eye-in-orbit position. The auditory task required speeded discrimination of sound elevation, with patients moving a central lever up or down according to the vertical position of a peripheral target sound, regardless of its side (left or right). Replicating previous auditory research, the patients' vertical discrimination performance was worse for auditory targets on the contralesional (left) versus the ipsilesional side, indicating neglect-related auditory deficits on this task. Critically, while this worse performance for left than right auditory targets was present (for both reaction times and errors) when gaze was directed centrally or rightwards, it was considerably reduced when gaze was directed leftwards. These results demonstrate that lateral gaze-direction can modulate neglect-related auditory spatial deficits, even though eye-position did not alter the initial auditory inputs. This outcome may relate to audio-visual links in spatial orienting and potentially some retinocentric influences on perceived sound location, although the latter alone could not explain all our results. Such findings might involve multisensory brain structures in which responses to sounds are modulated by eye-in-orbit position.

Attention↗

Phonemic discrimination in callosal agenesis.

Children with callosal agenesis have congenital absence of the corpus callosum. Previous analyses of these subjects have shown that they have significant difficulty on rhyming tasks and tasks of explicit sound organisation. This study investigated whether such difficulties were also manifested on simpler tasks requiring the discrimination and repetition of similar sounding linguistic material. None of the acallosal children tested performed at a normal level across tasks. This suggests a possible impairment in the initial registration or analysis of auditory material and possible bases for this deficit are discussed. In cases of callosal agenesis in which impairments in auditory discrimination are more severe there may be a more profound impact upon language development.

Adolescent↗

A case of word deafness with preserved span: implications for the structure and function of short-term memory.

Case IJ shows impaired capacity to repeat individual words despite normal hearing as measured by audiometry and tympanometry. She also has difficulty in identifying other environmental sounds. Her phonological memory span for visually-presented material is normal, and her memory span for spoken digits is only slightly impaired. It is suggested that she has a pre-phonological auditory processing deficit; the implications of this for discussion of the role of phonological short-term memory in language processing are discussed.

Auditory Perceptual Disorders↗

The role of individual difference in determining the nature of comprehension defects in aphasia.

This study was concerned with the relationship between locus of lesion and subtypes of language comprehension defect in aphasia. Previous studies had indicated that performance in sound recognition identified two subtypes of aural comprehension deficit and that performance in pantomime recognition identified two subtypes of reading comprehension defect. Defects in sound recognition and pantomime recognition were found in association with a variety of lesion loci. However, comprehension defective aphasics with normal sound recognition or pantomime recognition had lesions closely similar in location and size to those of aphasics who performed poorly on these tests. Findings suggest that whether an aphasic with a language comprehension defect is impaired in sound recognition or pantomime recognition depends, at least in part, on individually variable predisposing factors. It would appear possible that this phenomenon reflects a separate dimension of hemispheric cerebral dominance.

Adult↗

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.

Adult↗

Audio-spatial deficits in humans: differential effects associated with left versus right hemisphere parietal damage.

In order to study auditory spatial localization in subjects with posterior damage involving the parietal lobe, we investigated their manual pointing performances to linguistic and white noise signals distributed over six sound sources situated in the anterior auditory field at ear level. The results showed: (1) A striking difference between patterns of deficits associated with right and left damage. In subjects with right damage, auditory localization deficits occurred in the horizontal plane, were manifested as restrictions in the peripheral left auditory hemifield and tended to be related to left visual neglect. In subjects with left damage, auditory localization deficits occurred in the entire auditory field in the horizontal as well as vertical planes, and they were particularly strong in the antero-frontal region. (2) One subject with right damage and visual neglect but no left auditory spatial restriction, showed deficits in the right hemifield where sound source location tended to be overestimated. This subject also showed a better discrimination of the origin of a white noise than of a linguistic signal. Results are discussed in terms of hemispheric asymmetries of function.

Acoustic Stimulation↗

Impaired speech perception in aphasic patients: event-related potential and neuropsychological assessment.

The mismatch negativity component (MMN) of auditory event-related potentials (ERP) was recorded in four aphasic patients and in age, gender and education matched controls. The MMN changes elicited by tone, vowel, voicing stop consonant and place-of articulation contrasts were recorded over both hemispheres. The results of MMN amplitude, latency and distribution differences between aphasics and controls were analyzed in detail. An extensive neuropsychological investigation was performed in order to highlight the assumed dissociation and possible interactions between the impaired acoustic/phonetic perception and deficient comprehension in aphasic patients. Our principal finding was that MMN elicited by pitch deviations is not enough sensitive to distinguish between patients and age-matched controls. The MMN elicited by consonant contrasts was found to be the most vulnerable in aphasic patients investigated. The MMN elicited by voicing ([ba:] vs. [pa:]) and place-of-articulation ([ba:] vs. [ga:]) could be characterized by total lack, distorted or very limited distribution and correlated with the patients' performance shown in the behavioral phoneme discrimination task. The magnitude of the deficient phoneme (vowel and consonant contrasts) processing shown by MMN anomalies was proportionally related to the non-word discrimination and did not interact with the word discrimination performance. The impact of deficient speech sound processing on higher level processes may depend on the type of aphasia, while the presence of perceptual deficits in processing acoustic/phonetic contrasts seems to be independent of the type of aphasia.

Adult↗

Deficit of auditory space perception in patients with visuospatial neglect.

There have been many studies of visuospatial neglect, but fewer studies of neglect in relation with other sensory modalities. In the present study we investigate the performance of six right brain damaged (RBD) patients with left visual neglect and six RBD patients without neglect in an auditory spatial task. Previous work on sound localisation in neglect patients adopted measure of sound localisation based on directional motor responses (e.g., pointing to sounds) or judgement of sound position with respect to the body midline (auditory midline task). However, these measures might be influenced by non-auditory biases related with motor and egocentric components. Here we adopted a perceptual measure of sound localisation, consisting in a verbal judgement of the relative position (same or different) of two sequentially presented sounds. This task was performed in a visual and in a blindfolded condition. The results revealed that sound localisation performance of visuospatial neglect patients was severely impaired with respect to that of RBD controls, especially when sounds originated in contralesional hemispace. In such condition, neglect patients were always unable to discriminate the relative position of the two sounds. No difference in performance emerged as a function of the visual condition in either group. These results demonstrate a perceptual deficit of sound localisation in patients with visuospatial neglect, suggesting that the spatial deficits of these patients can arise multimodally for the same portion of external space.

Adult↗

Deficit in automatic sound-change detection may underlie some music perception deficits after acute hemispheric stroke.

Music perception deficits following acute neurological damage are thought to be rare. By a newly devised test battery of music-perception skills, however, we were able to identify among a group of 12 patients with acute hemispheric stroke six patients with music perception deficits (amusia) while six others had no such deficits. In addition we recorded event-related brain potentials (ERPs) in a passive listening task with frequent standard and infrequent pitch deviants designed to elicit the mismatch negativity (MMN). The MMN in the patients with amusia was grossly reduced, while the non-amusic patients and control subjects had MMNs of equal size. These data show that amusia is quite common in unselected stroke patients. The MMN reduction suggests that amusia is related to unspecific automatic stimulus classification deficits in these patients.

Acute Disease↗