Speech perception in schizophrenia

Functional near-infrared spectroscopy in schizophrenia patients with auditory verbal hallucinations: Preliminary observations

Auditory Signal Detection (ASD) theory postulates that auditory verbal hallucinations (AVH) result from an aberrant association of meaningful connection to abstract noises. In this study, schizophrenia (SZ) patients with persistent AVH (N = 17) and matched controls (N = 25) performed an ASD task with concurrent functional near-infrared spectroscopy recording targetting the left dorsolateral prefrontal cortex (L-DLPFC) and left temporoparietal junction (L-TPJ). During the task, discriminability index had a significant negative correlation, and early deoxyhemoglobin (HbR) latency at L-TPJ positively correlated with AVH scores. Also, patients had significantly lower discriminability, early HbR latency at L-TPJ, and delayed latency at L-DLPFC. This finding suggests the presence of ASD abnormalities and impaired auditory processing in SZ patients with AVH supporting ASD-based pathogenesis.

Schizotypal traits are not related to multisensory integration or audiovisual speech perception

Multisensory integration, the binding of sensory information from different sensory modalities, may contribute to perceptual symptomatology in schizophrenia, including hallucinations and aberrant speech perception. Differences in multisensory integration and temporal processing, an important component of multisensory integration, are consistently found in schizophrenia. Evidence is emerging that these differences extend across the schizophrenia spectrum, including individuals in the general population with higher schizotypal traits. In the current study, we investigated the relationship between schizotypal traits and perceptual functioning, using audiovisual speech-in-noise, McGurk, and ternary synchrony judgment tasks. We measured schizotypal traits using the Schizotypal Personality Questionnaire (SPQ), hypothesizing that higher scores on Unusual Perceptual Experiences and Odd Speech subscales would be associated with decreased multisensory integration, increased susceptibility to distracting auditory speech, and less precise temporal processing. Surprisingly, these measures were not associated with the predicted subscales, suggesting that these perceptual differences may not be present across the schizophrenia spectrum.

Abnormal lateralization in schizophrenia: empirical evidence for an integrated model

Cerebral deficits in schizophrenia have been associated either with left hemisphere dysfunction, or with impairment in interhemispheric transfer. To test the relative efficacy of the two hypotheses, 63 right-handed subjects (24 paranoid schizophrenics, 21 nonparanoid schizophrenics, and 18 normal controls) were given two auditory lateral tasks: identification of dichotically delivered tonal sequences and digit sets. As the data analyses showed, more correct responses were given by the normal controls than by the patients, and by males than by females. Generally, report (especially from the ear reported second) was better from the right than from the left ear. This right ear advantage (which was more consistent in males than in females) was abnormally large for the paranoid schizophrenics who showed on both tests, relative to normal subjects, a slight decrement in right ear report and a significant decrement in left ear report. The data were interpreted as indicating left hemisphere dysfunction and structural callosal damage in paranoid schizophrenics.

Visual hallucinations, thalamocortical physiology and Lewy body disease: A review

One of the core diagnostic criteria for Dementia with Lewy Bodies (DLB) is the presence of visual hallucinations. The presence of hallucinations, along with fluctuations in the level of arousal and sleep disturbance, point to potential pathological mechanisms at the level of the thalamus. However, the potential role of thalamic dysfunction in DLB, particularly as it relates to the presence of formed visual hallucinations is not known. Here, we review the literature on the pathophysiology of DLB with respect to modern theories of thalamocortical function and attempt to derive an understanding of how such hallucinations arise. Based on the available literature, we propose that combined thalamic-thalamic reticular nucleus and thalamocortical pathology may explain the phenomenology of visual hallucinations in DLB. In particular, diminished α7 cholinergic activity in the thalamic reticular nucleus may critically disinhibit thalamocortical activity. Further, concentrated pathological changes within the posterior regions of the thalamus may explain the predilection for the hallucinations to be visual in nature.

Auditory false perception in schizophrenia: Development and validation of auditory signal detection task

Auditory hallucinations constitute an important symptom component in 70-80% of schizophrenia patients. These hallucinations are proposed to occur due to an imbalance between perceptual expectation and external input, resulting in attachment of meaning to abstract noises; signal detection theory has been proposed to explain these phenomena. In this study, we describe the development of an auditory signal detection task using a carefully chosen set of English words that could be tested successfully in schizophrenia patients coming from varying linguistic, cultural and social backgrounds. Schizophrenia patients with significant auditory hallucinations (N=15) and healthy controls (N=15) performed the auditory signal detection task wherein they were instructed to differentiate between a 5-s burst of plain white noise and voiced-noise. The analysis showed that false alarms (p=0.02), discriminability index (p=0.001) and decision bias (p=0.004) were significantly different between the two groups. There was a significant negative correlation between false alarm rate and decision bias. These findings extend further support for impaired perceptual expectation system in schizophrenia patients.

Increased risk of psychosis in patients with hearing impairment: Review and meta-analyses

Several studies suggest hearing impairment as a risk factor for psychosis. Hearing impairment is highly prevalent and potentially reversible, as it can be easily diagnosed and sometimes improved. Insight in the association between hearing impairment and psychosis can therefore contribute to prevention of psychosis. This paper provides meta-analyses of all epidemiologic evidence on the association between hearing impairment and psychosis and summarizes mechanisms that potentially underlie this relationship. Meta-analyses showed an increased risk of hearing impairment on all psychosis outcomes, such as hallucinations (OR 1.40(95%CI 1.18-1.65; n=227,005)), delusions (OR 1.55(95%CI 1.36-1.78; n=250,470)), psychotic symptoms (OR 2.23(95%CI 1.83-2.72; n=229,647) and delirium (OR 2.67(95%CI 2.05-3.48; n=12,432). Early exposure to hearing impairment elevated the risk of later development of schizophrenia (OR 3.15(95%CI 1.25-7.95; n=50,490)). Potential mechanisms underlying this association include loneliness, diminished theory of mind, disturbances of source monitoring and top-down processing and deafferentiation. Early assessment and treatment of hearing impairment in patients with (high risk of) psychosis may be essential in psychosis treatment and prevention.

The DISC1 promoter: characterization and regulation by FOXP2

Disrupted in schizophrenia 1 (DISC1) is a leading candidate susceptibility gene for schizophrenia, bipolar disorder and recurrent major depression, which has been implicated in other psychiatric illnesses of neurodevelopmental origin, including autism. DISC1 was initially identified at the breakpoint of a balanced chromosomal translocation, t(1;11) (q42.1;14.3), in a family with a high incidence of psychiatric illness. Carriers of the translocation show a 50% reduction in DISC1 protein levels, suggesting altered DISC1 expression as a pathogenic mechanism in psychiatric illness. Altered DISC1 expression in the post-mortem brains of individuals with psychiatric illness and the frequent implication of non-coding regions of the gene by association analysis further support this assertion. Here, we provide the first characterization of the DISC1 promoter region. Using dual luciferase assays, we demonstrate that a region -300 to -177 bp relative to the transcription start site (TSS) contributes positively to DISC1 promoter activity, while a region -982 to -301 bp relative to the TSS confers a repressive effect. We further demonstrate inhibition of DISC1 promoter activity and protein expression by forkhead-box P2 (FOXP2), a transcription factor implicated in speech and language function. This inhibition is diminished by two distinct FOXP2 point mutations, R553H and R328X, which were previously found in families affected by developmental verbal dyspraxia. Our work identifies an intriguing mechanistic link between neurodevelopmental disorders that have traditionally been viewed as diagnostically distinct but which do share varying degrees of phenotypic overlap.

Masking of speech in people with first-episode schizophrenia and people with chronic schizophrenia

In "cocktail-party" environments, although listeners feel it difficult to recognize attended speech due to both energetic masking and informational masking, they can use various perceptual/cognitive cues, such as content and voice primes, to facilitate their attention to target speech. In patients with schizophrenia, both speech-perception deficits and increased vulnerability to masking stimuli generally occur. This study investigated whether speech recognition in first-episode patients (FEPs) and chronic patients (CPs) of schizophrenia is more vulnerable to noise masking and/or speech masking than that in demographics-matched-healthy controls, and whether patients with schizophrenia can use primes to unmask speech. In a trial under the priming condition, before the target sentence containing three keywords was co-presented with a noise or speech masker, the prime (early part of the sentence including the first two keywords) was recited in quiet with the target-speaker's voice. The results show that in patients, target-speech recognition was more impaired under speech-masking conditions than noise-masking conditions, and the impairment in CPs (n=22) was larger than that in FEPs (n=12). Although working memory for holding prime-content information in patients, especially CPs, was more vulnerable to masking, especially speech masking, than that in healthy controls, patients were still able to use the prime to unmask the last keyword. Thus, in "cocktail-party" environments, speech recognition in people with schizophrenia is more vulnerable to masking, particularly informational masking, and the speech-recognition impairment augments as the illness progresses. However, people with schizophrenia can use the content/voice prime to reduce energetic masking and informational masking of target speech.

[A case of transient auditory agnosia and schizophrenia]

We report a case of transient functional auditory agnosia and schizophrenia and discuss their relationship. A 30-year-old woman with schizophrenia reporting bilateral hearing loss was found in history taking to be able to hear but could neither understand speech nor discriminate among environmental sounds. Audiometry clarified normal but low speech discrimination. Otoacoustic emission and auditory brainstem response were normal. Magnetic resonance imaging (MRI) elsewhere evidenced no abnormal findings. We assumed that taking care of her grandparents who had been discharged from the hospital had unduly stressed her, and her condition improved shortly after she stopped caring for them, returned home and started taking a minor tranquilizer.

Impaired multisensory processing in schizophrenia: deficits in the visual enhancement of speech comprehension under noisy environmental conditions

BACKGROUND

Viewing a speaker's articulatory movements substantially improves a listener's ability to understand spoken words, especially under noisy environmental conditions. In this study we investigated the ability of patients with schizophrenia to integrate visual and auditory speech. Our objective was to determine to what extent they experience benefit from visual articulation and to detail under what listening conditions they might show the greatest impairments.

METHODS

We assessed the ability to recognize auditory and audiovisual speech in different levels of noise in 18 patients with schizophrenia and compared their performance with that of 18 healthy volunteers. We used a large set of monosyllabic words as our stimuli in order to more closely approximate performance in everyday situations.

RESULTS

Patients with schizophrenia showed deficits in their ability to derive benefit from visual articulatory motion. This impairment was most pronounced at signal-to-noise levels where multisensory gain is known to be maximal in healthy control subjects. A surprising finding was that despite known early auditory sensory processing deficits and reports of impairments in speech processing in schizophrenia, patients' performance in unisensory auditory speech perception remained fully intact.

CONCLUSIONS

Thus, the results showed a specific deficit in multisensory speech processing in the absence of any measurable deficit in unisensory speech processing and suggest that sensory integration dysfunction may be an important and, to date, rather overlooked aspect of schizophrenia.

The relationship between membrane pathology and language disorder in schizophrenia

Receptive language disorder in schizophrenia has been hypothesized to involve a fundamental deficit in the temporal (time-based) dynamics of brain function that includes disruptions to patterns of activation and synchronization. In this paper, candidate mechanisms and pathways that could account for this basic deficit are discussed. Parallels are identified between the patterns of language dysfunction observed for schizophrenia and dyslexia, two separate clinical disorders that may share a common abnormality in cell membrane phospholipids. A heuristic is proposed which details a trajectory involving an interaction of brain fatty acids and second-messenger function that modulates synaptic efficacy, and, in turn, influences language processing in schizophrenia patients. It is additionally hypothesized that a primary deficit of functional excitation originating in the cerebellum, in combination with a compensatory decrease of functional inhibition in the prefrontal cortex, influences receptive language dysfunction in schizophrenia.

Brain event-related potentials (ERPs) in schizophrenia during a word recognition memory task

Impairments of recognition memory for words and attenuation of the ERP 'old-new' effect have been found in patients with left medial temporal lobe damage. If left temporal lobe dysfunction in schizophrenia involves medial structures (e.g. hippocampus), then schizophrenic patients might show similar abnormalities of verbal recognition memory. This study recorded ERPs from 30 electrode sites while subjects were engaged in a continuous word recognition memory task. Results are reported for 24 patients having a diagnosis of schizophrenia (n = 16) or schizoaffective disorder (n = 8) and 19 age-matched healthy controls. Both patients and controls showed the expected 'old-new' effect, with greater late positivity to correctly recognized old words at posterior sites, and there was also no significant difference between groups in P3 amplitude. However, accuracy of word recognition memory was poorer in patients than controls, and patients showed markedly smaller N2 amplitude. Reduced amplitudes of N2 and N2-P3 were associated with poorer performance, with highest correlations over the left inferior parietal (N2) and left medial parietal (N2-P3) region. Moreover, patients failed to show significantly greater left than right hemisphere amplitude of N2-P3 at posterior sites, which was seen for healthy controls. These findings suggest that impaired word recognition in schizophrenia may arise from a left lateralized deficit at an early stage of processing, beginning at 200-300 ms after word onset.

Mental health and acquired hearing impairment: a review

Recent work demonstrates that hearing impairment is much more common than previously suspected. The disability may be unrecognized or denied by the sufferer and may attract social stigma rather than sympathy from others. The effect on mental health is surprisingly neglected. Early studies of psychiatric patients suggested hearing impairment is an important cause of paranoid illness, but more recent studies of wider populations have failed to confirm this association. Hearing impairment is unrelated to intellect when controlled for age, but is an important differential diagnosis of dementia in the elderly. Evidence accumulates to suggest that the hearing impaired are vulnerable to depression, social stress and isolation, but reliable controlled studies of psychiatric sequelae are needed.

Immunoglobulins in schizophrenics and prediction of need for hospital care

The purpose of the study was to determine whether the total number of days spent in hospital during a 5-year follow-up period could be predicted by determining IgA, IgG and IgM concentrations in 62 schizophrenics on initial admission. A high IgA concentration on initial admission indicated less frequent need for hospital care during follow-up. A scattering diagram of this negative correlation showed that the correlation was based on a group of seven patients whose IgA concentrations markedly exceeded normal values. This group with exceedingly high IgA differed from the control group in several areas, which would indicate that these patients suffer from a "different" schizophrenia than the patients in the control group. This finding supports the idea of the heterogeneity of schizophrenia, and raises the possibility of developing biochemical methods to delineate the diagnostic category of schizophrenia.

The effect of context during word perception in schizophrenic patients

Hospitalized chronic and acute schizophrenics were compared with age- and social-status-matched controls on word perception tests to measure the effect of context on recognition thresholds. In Experiment 1 the method of J. Morton (1964, British Journal of Psychology, 55, 165-180) was adopted to see how related and unrelated contexts influenced word recognition thresholds when both context and stimulus word were presented visually. Experiment 2 was an auditory analog of Experiment 1 and in addition the chronic schizophrenics were selected on the basis of a presence or absence of auditory hallucinations. The influence of context on perceptual thresholds was quite normal in all schizophrenics. However, analysis of the incorrect responses elicited showed that some schizophrenic subjects do produce bizarre or irrelevant responses or perseveration to a greater extent than their controls. These results are explained in terms of automatic and strategic modes of information processing. The automatic processes responsible for the adjustment of perceptual thresholds operate normally in schizophrenics but response production which demands strategic selection and editing of responses is prone to malfunction which results in the observed deviations in the normal use of language.

Bilateral auditory acuity of schizophrenic patients: effects of repeated testing, time of day and medication

Higher than normal auditory thresholds were demonstrated in chronic schizophrenic patients. A greater right ear sensitivity than left was exhibited, although right ear superiority diminished with repeated testing over weeks while left ear thresholds remained relatively stable. The results of acoustic impedance measures suggest that these findings are not associated with peripheral outer and middle ear disorders.

Picture perception and abstract thought in schizophrenia

Acute schizophrenics were compared with depressed, normal and brain-damaged subjects on their ability to appreciate a meaningful picture. Their responses were measured for level of abstraction (how well the theme was conveyed), for strategy (whether details were reported before or after a global interpretation) and for appropriateness of content. Schizophrenics were less abstract than normals, more abstract than brain-damaged subjects, but no different from depressives on this measure. Their strategy was different from normals but comparable with that of depressives. The majority of schizophrenics gave inappropriate responses. It is suggested that meaningful picture interpretation might be a useful tool for evaluating the distortion of meaning which characterizes schizophrenia.

Consciousness, information processing and schizophrenia

The symptoms of schizophrenia can be interpreted as the result of a defect in the mechanism that controls and limits the contents of consciousness. This defect can be understood as excessive self-awareness. Normally most of the complex information processing which is continuously required by even simple acts of perception, language and thought goes on below the level of awareness; whereas in schizophrenic patients some of this processing, or the results of this processing, not in themselves abnormal, become conscious. This excessive awareness can account for the typical symptoms of schizophrenia and explains many of the specific cognitive abnormalities found in schizophrenic patients.

"Semantic" and "acoustic" errors of aphasic and schizophrenic patients in a sound-picture matching task

Broca's aphasics, Wernicke's aphasics, brain-damaged patients without aphasia, and chronic schizophrenics were tested on a task to match meaningful sounds to one of four pictures. One of the depicted objects was the natural source of the sound, one was an object belonging to the same semantic category as the correct object, one was an object producing acoustically similar sounds as the correct object, and one was an object not related either semantically or acoustically to the correct object. In one item set the "semantic" distractors produced a sound completely different from the presented one; in another item set the "semantic" distractors made practically no specific sounds at all. Broca's and Wernicke's aphasics were shown to have significantly higher total error scores than brain-damaged patients without aphasia and to make significantly more "semantic" errors only on the first item set and "acoustic" errors on both item sets than the brain-damaged patients without aphasia. However, after correcting for guessing the differences between groups with respect to "semantic" and "acoustic" errors vanished. The aphasics' difficulties in coping with the sound-picture matching task might be difficulties in processing the acoustic dimensions of the items. It is, however, suggested that the impairment is not perceptual but of the cognitive kind repeatedly demonstrated in tasks which require the analytic extraction of features of the stimulus or of the concept represented by the stimulus.

Deafness and psychiatric illness

Review of the literature concerning the relationship between deafness and psychiatric disorder reveals differences in the pattern of illness depending on the severity of deafness and the age of onset. In particular, the prevalence of schizophrenia in the prelingually deaf is similar to that found in the normal population, whereas the hard of hearing are over-represented among samples of patients suffering from paranoid psychoses in later life. Possible modes of action of long-standing hearing loss in the aetiology of paranoid illnesses are considered: the psychological and social consequences of deafness, the possible contribution of sensory deprivation phenomena, and the interference of hearing loss in attention, perception and communication. Finally, possible future lines of research are suggested.