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

Auditory Agnosia for Environmental Sounds in Alzheimer's Disease: Not Hearing and Not Listening?

Auditory agnosia for environmental sounds (AES) is an example of central auditory dysfunction. It is presumed to be independent of language deficits and in presence of normal hearing. We undertook a detailed neuropsychological assessment including environmental sound naming and recognition in 34 clinically mild Alzheimer's disease (AD) patients and 29 age-matched healthy control subjects. In patients with AD, audiometry was performed to assess the impact on test performance, and in normal controls the Hearing Handicap Inventory for the Elderly - Screening Version to exclude more than mild hearing loss. We adapted a validated environmental sound battery and found near perfect scores in controls. We found that environmental sound agnosia is common in mild AD. We found a statistically significant difference in mean pure tone audiometry in the best ear between patients with and those patients without naming deficits of 11.3 dB (p = 0.010) and of 14.7 dB (p = 0.000) between those with and without recognition deficits. Statistical significance remained after correcting for age, aphasia, Mini-Mental State Examination score, and working memory. Slight and moderate peripheral hearing loss increases the odds ratio of recognition deficits by 13.75 (confidence interval 2.3-81.5) compared to normal hearing patients. We did not find evidence for different forms of AES. This work suggests that an interaction between peripheral hearing loss and AD pathology produces problems with environmental sound recognition. It confirms that the relationship between hearing and dementia is complex but also suggests that interventions to prevent and treat hearing loss could have an effect on AD in its clinical expression.

The Deficit of Multimodal Perception of Congruent and Non-Congruent Fearful Expressions in Patients with Schizophrenia: The ERP Study

Emotional dysfunction, including flat affect and emotional perception deficits, is a specific symptom of schizophrenia disorder. We used a modified multimodal odd-ball paradigm with fearful facial expressions accompanied by congruent and non-congruent emotional vocalizations (sounds of women screaming and laughing) to investigate the impairment of emotional perception and reactions to other people's emotions in schizophrenia. We compared subjective ratings of emotional state and event-related potentials (EPPs) in response to congruent and non-congruent stimuli in patients with schizophrenia and healthy controls. The results showed the altered multimodal perception of fearful stimuli in patients with schizophrenia. The amplitude of N50 was significantly higher for non-congruent stimuli than congruent ones in the control group and did not differ in patients. The P100 and N200 amplitudes were higher in response to non-congruent stimuli in patients than in controls, implying impaired sensory gating in schizophrenia. The observed decrease of P3a and P3b amplitudes in patients could be associated with less attention, less emotional arousal, or incorrect interpretation of emotional valence, as patients differed from healthy controls in the emotion scores of non-congruent stimuli. The difficulties in identifying the incoherence of facial and audial components of emotional expression could be significant in understanding the psychopathology of schizophrenia.

Mismatch negativity impairment is associated with deficits in identifying real-world environmental sounds in schizophrenia

BACKGROUND

Patients with schizophrenia (SZ) have impairments in processing auditory information that have been linked to deficits in cognitive and psychosocial functioning. Dysfunction in auditory sensory processing in SZ has been indexed by mismatch negativity (MMN), an event-related potential evoked by a rare, deviant stimulus embedded within a sequence of identical standard stimuli. Although MMN deficits in SZ have been studied extensively, relatively little is known about how these deficits relate to accurately identifying real-world, ecologically-salient sounds.

METHODS

MMN was assessed in SZ patients (n=21) and non-psychiatric comparison subjects (NCS; n=16). Participants were also assessed in their ability to identify common environmental sounds using a subset of 80 sound clips from the International Affective Digitized Sounds 2nd Ed collection.

RESULTS

SZ patients made significantly more errors in environmental sound identification (p<0.001, d=0.86) and showed significantly reduced MMN amplitude deficits in MMN compared to NCS (p<0.01, d=0.97). In SZ patients, MMN deficits were associated with significantly greater environmental sound identification errors (r=0.61, p<0.01).

CONCLUSIONS

Impairments in early auditory information processing in schizophrenia account for significant proportions of variance in the ability to identify real-world, functionally relevant environmental sounds. This study supports the view that interventions targeting deficits in low-level auditory sensory processing may also impact more complex cognitive brain processes relevant to psychosocial disability.

On the correlation between perceptual inundation caused by realistic immersive environmental auditory scenes and the sensory gating inventory in schizophrenia

BACKGROUND

In schizophrenia, perceptual inundation related to sensory gating deficit can be evaluated "off-line" with the sensory gating inventory (SGI) and "on-line" during listening tests. However, no study investigated the relation between "off-line evaluation" and "on-line evaluation". The present study investigates this relationship.

METHODS

A sound corpus of 36 realistic environmental auditory scenes was obtained from a 3D immersive synthesizer. Twenty schizophrenic patients and twenty healthy subjects completed the SGI and evaluated the feeling of "inundation" from 1 ("null") to 5 ("maximum") for each auditory scene. Sensory gating deficit was evaluated in half of each population group with P50 suppression electrophysiological measure.

RESULTS

Evaluation of inundation during sound listening was significantly higher in schizophrenia (3.25) compared to the control group (2.40, P<.001). The evaluation of inundation during the listening test correlated significantly with the perceptual modulation (n=20, rho=.52, P=.029) and the over-inclusion dimensions (n=20, rho=.59, P=.01) of the SGI in schizophrenic patients and with the P50 suppression for the entire group of controls and patients who performed ERP recordings (n=20, rho=-.49, P=.027).

CONCLUSION

An evaluation of the external validity of the SGI was obtained through listening tests. The ability to control acoustic parameters of each of the realistic immersive environmental auditory scenes might in future research make it possible to identify acoustic triggers related to perceptual inundation in schizophrenia.

MK-801 Impairs Cognitive Coordination on a Rotating Arena (Carousel) and Contextual Specificity of Hippocampal Immediate-Early Gene Expression in a Rat Model of Psychosis

Flexible behavior in dynamic, real-world environments requires more than static spatial learning and memory. Discordant and unstable cues must be organized in coherent subsets to give rise to meaningful spatial representations. We model this form of cognitive coordination on a rotating arena - Carousel where arena- and room-bound spatial cues are dissociated. Hippocampal neuronal ensemble activity can repeatedly switch between multiple representations of such an environment. Injection of tetrodotoxin into one hippocampus prevents cognitive coordination during avoidance of a stationary room-defined place on the Carousel and increases coactivity of previously unrelated neurons in the uninjected hippocampus. Place avoidance on the Carousel is impaired after systemic administration of non-competitive NMDAr blockers (MK-801) used to model schizophrenia in animals and people. We tested if this effect is due to cognitive disorganization or other effect of NMDAr antagonism such as hyperlocomotion, spatial memory impairment, or general learning deficit. We also examined if the same dose of MK-801 alters patterns of immediate-early gene (IEG) expression in the hippocampus. IEG expression is triggered in neuronal nuclei in a context-specific manner after behavioral exploration and it is used to map activity in neuronal populations. IEG expression is critical for maintenance of synaptic plasticity and memory consolidation. We show that the same dose of MK-801 that impairs spatial coordination of rats on the Carousel also eliminates contextual specificity of IEG expression in hippocampal CA1 ensembles. This effect is due to increased similarity between ensembles activated in different environments, consistent with the idea that it is caused by increased coactivity between neurons, which did not previously fire together. Our data support the proposition of the Hypersynchrony theory that cognitive disorganization in psychosis is due to increased coactivity between unrelated neurons.

Modulation of affective face processing deficits in Schizophrenia by congruent emotional sounds

Schizophrenia is a psychiatric disorder resulting in prominent impairments in social functioning. Thus, clinical research has focused on underlying deficits of emotion processing and their linkage to specific symptoms and neurobiological dysfunctions. Although there is substantial research investigating impairments in unimodal affect recognition, studies in schizophrenia exploring crossmodal emotion processing are rare. Therefore, event-related potentials were measured in 15 patients with schizophrenia and 15 healthy controls while rating the expression of happy, fearful and neutral faces and concurrently being distracted by emotional or neutral sounds. Compared with controls, patients with schizophrenia revealed significantly decreased P1 and increased P2 amplitudes in response to all faces, independent of emotion or concurrent sound. Analyzing these effects with regard to audiovisual (in)congruence revealed that P1 amplitudes in patients were only reduced in response to emotionally incongruent stimulus pairs, whereas similar amplitudes between groups could be observed for congruent conditions. Correlation analyses revealed a significant negative correlation between general symptom severity (Brief Psychiatric Rating Scale-V4) and P1 amplitudes in response to congruent audiovisual stimulus pairs. These results indicate that early visual processing deficits in schizophrenia are apparent during emotion processing but, depending on symptom severity, these deficits can be restored by presenting concurrent emotionally congruent sounds.

The cognitive neuropsychology of auditory hallucinations: a parallel auditory pathways framework

Auditory hallucinations are generally defined as false perceptions. Recent developments in auditory neuroscience have rapidly increased our understanding of normal auditory perception revealing (partially) separate pathways for the identification ("what") and localization ("where") of auditory objects. The current review offers a reexamination of the nature of auditory hallucinations in schizophrenia using this object-based framework. First, the structural and functional organization of auditory what and where pathways is briefly described. Then, using recent functional neuroimaging data from healthy subjects and patients with schizophrenia, key phenomenological features of hallucinations are linked to abnormal processing both within and between these pathways. Finally, current cognitive explanations of hallucinations, based on intrusive cognitions and impaired source memory, are briefly outlined and set within this framework to provide an integrated cognitive neuropsychological model of auditory hallucinations.

Aspects of Piaget's cognitive developmental psychology and neurobiology of psychotic disorders - an integrative model

Psychological, neurobiological and neurodevelopmental approaches have frequently been used to provide pathogenic concepts on psychotic disorders. However, aspects of cognitive developmental psychology have hardly been considered in current models. Using a hypothesis-generating approach an integration of these concepts was conducted. According to Piaget (1896-1980), assimilation and accommodation as forms of maintenance and modification of cognitive schemata represent fundamental processes of the brain. In general, based on the perceived input stimuli, cognitive schemata are developed resulting in a conception of the world, the realistic validity and the actuality of which is still being controlled and modified by cognitive adjustment processes. In psychotic disorders, however, a disproportion of environmental demands and the ability to activate required neuronal adaptation processes occurs. We therefore hypothesize a failure of the adjustment of real and requested output patterns. As a consequence autonomous cognitive schemata are generated, which fail to adjust with reality resulting in psychotic symptomatology. Neurobiological, especially neuromodulatory and neuroplastic processes play a central role in these perceptive and cognitive processes. In conclusion, integration of cognitive developmental psychology into the existing pathogenic concepts of psychotic disorders leads to interesting insights into basic disease mechanisms and also guides future research in the cognitive neuroscience of such disorders.

Functional neuroanatomy of non-verbal semantic sound processing in humans

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 H(2) (15)O-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.