Attribution of mental States to others by schizophrenic patients

Setting domain boundaries for convergence of biological and psychological perspectives on cognitive coordination in schizophrenia

The claim that the disorganized subtype of schizophrenia results from glutamate hypofunction is enhanced by consideration of current subtypology of schizophrenia, symptom definition, interdependence of neurotransmitters, and the nature of the data needed to support the hypothesis. Careful specification clarifies the clinical reality of disorganization as a feature of schizophrenia and increases the utility of the subtype.

Schizophrenia: Putting context in context

Although context-processing deficits may be core features of schizophrenia, context remains a poorly defined concept. To test Phillips & Silverstein's model, we need to operationalize context more precisely. We offer several useful ways of framing context and discuss enhancing or facilitating schizophrenic patients' performance under different contextual situations. Furthermore, creativity may be a byproduct of cognitive uncoordination.

Phenomenology, context, and self-experience in schizophrenia

Impairments in cognitive coordination in schizophrenia are supported by phenomenological data that suggest deficits in the processing of visual context. Although the target article is sympathetic to such a phenomenological perspective, we argue that the relevance of phenomenological data for a wider understanding of consciousness in schizophrenia is not sufficiently addressed by the authors.

Guarding against over-inclusive notions of “context”: Psycholinguistic and electrophysiological studies of specific context functions in schizophrenia

Phillips & Silverstein offer an exciting synthesis of ongoing efforts to link the clinical and cognitive manifestations of schizophrenia with cellular accounts of its pathophysiology. We applaud their efforts but wonder whether the highly inclusive notion of “context” adequately captures some important details regarding schizophrenia and NMDA/glutamate function that are suggested by work on language processing and cognitive electrophysiology.

Mechanisms of disrupted language comprehension in schizophrenia

Mechanisms that contribute to perceptual processing dysfunction in schizophrenia were examined by Phillips & Silverstein, and formulated as involving disruptions in both local and higher-level coordination of signals. We agree that dysfunction in the coordination of cognitive functions (disconnection) is also indicated for many of the linguistic processing deficits documented for schizophrenia. We suggest, however, that it may be necessary to add a timing mechanism to the theoretical account.

Cognitive coordination and its neurobiological bases: A new continent to explore

The additional arguments and evidence supplied by the commentaries strengthen the hypothesis that underactivity of NMDA receptors produces impaired cognitive coordination in schizophrenia. This encourages the hope that though the distance from molecules to mind is great, it can nevertheless be traversed. We therefore predict that in this decade or the next molecular psychology will be seen to be as fundamental to our understanding of mind as molecular biology is to our understanding of life.

Context rules

It is proposed that cortical activity is normally coordinated across synaptically connected areas and that this coordination supports cognitive coherence relations. This view is consistent with the NMDA- hypoactivity hypothesis of the target article in regarding disorganization symptoms in schizophrenia as arising from disruption of normal interareal coordination. This disruption may produce abnormal contextual effects in the cortex that lead to anomalous cognitive coherence relations.

The ketamine model for schizophrenia

This commentary compares clinical aspects of ketamine with the amphetamine model of schizophrenia. Hallucinations and loss of insight, associated with amphetamine, seem more schizophrenia-like. Flat affect encountered with ketamine is closer to the clinical presentation in schizophrenia. We argue that flat affect is not a sign of schizophrenia, but rather, arisk factorfor chronic schizophrenia.

Cortical connectivity in high-frequency beta-rhythm in schizophrenics with positive and negative symptoms

In chronic schizophrenic patients with both positive and negative symptoms (see Table 1), interhemispheric connections at the high frequency beta2-rhythm are absent during cognitive tasks, in contrast to normal controls, who have many interhemispheric connections at this frequency in the same situation. Connectivity is a fundamental brain feature, evidently greatly promoted by the NMDA system. It is a more reliable measure of brain function than the spectral power of this rhythm.

Theory of mind in schizophrenia: Damaged module or deficit in cognitive coordination?

Schizophrenics exhibit a deficit in theory of mind (ToM), but an intact theory of biology (ToB). One explanation is that ToM relies on an independent module that is selectively damaged. Phillips & Silverstein's analyses suggest an alternative: ToM requires the type of coordination that is impaired in schizophrenia, whereas ToB is spared because this type of coordination is not involved.

Inductive reasoning and the understanding of intention in schizophrenia

BACKGROUND

The study explored the relationship between the understanding of intention in veiled speech acts and the ability to reason inductively.

METHODS

A total of 39 people with DSM-IV-defined schizophrenia with no behavioural signs and 44 healthy participants performed the Hinting Task, a measure of pragmatic language in which the speaker's intention must be inferred, and a measure of inductive reasoning (Aha! Sentences) in which the meaning of ambiguous nonsocial sentences had to be inferred. The participants also completed measures of general intellectual ability, immediate memory for narrative and social problem-solving ability.

RESULTS

A substantial correlation was found between performance on the inductive reasoning task and the Hinting Task in the sample of people with schizophrenia. The same relationship was not seen in the normal control sample. The robust relationship between these two measures in this sample survived when the roles of immediate memory for narrative and intellectual ability were controlled for. Furthermore, the relationship was distinctly more compelling for the patients who were currently ill compared to those in remission.

CONCLUSION

These data suggest that people with schizophrenia use a different strategy to infer the meaning behind pragmatic language than that used by normally functioning adults. It is suggested that a reliance on different, possibly less specialised, skills in this group to perform this simple social inference task underlies their deficient performance on this and other measures of social inference. The fact that the relationship between the tasks in patients in remission is not as robust implies that the use of specialised skills to perform social inference tasks may be compromised most significantly during acute phases.

Reasoning about physical causality and other's intentions in schizophrenia

INTRODUCTION

Several studies have shown that schizophrenic patients have impaired theory-of-mind skills involving the attribution of false beliefs and intentions to others. Despite the methodological difficulties of false belief protocols, experiments have concluded that the deficit is specific and cannot be explained in terms of a general cognitive impairment. The situation, however, remains unclear as far as the attribution of intentions to others is concerned. We propose the use of nonverbal control tasks based on physical causality to demonstrate the specificity of the impairment of attribution of intentions.

METHODS

We compared the performances of schizophrenic patients and normal subjects on the attribution of intentions and on two control tasks involving physical causality (reasoning about the weight, location, speed, and the physical properties of objects). 25 schizophrenic patients and 25 healthy subjects participated in the study. Each subject was assessed under three conditions using comic strips: attribution of intentions, physical causality with characters, physical causality without characters.

RESULTS

The performances of schizophrenic patients differed significantly from those of healthy subjects only in the attribution of intentions condition. This difference was also found when only subjects having optimal performances in physical logic were considered and when verbal IQ was considered as a co-variable.

CONCLUSIONS

Nonverbal attribution of intentions to others is specifically impaired in schizophrenia. This conclusion is in agreement with recent neuroimaging findings.

Theory of mind and the role of IQ in chronic disorganized schizophrenia

BACKGROUND

Several studies have suggested a theory of mind (ToM) deficit in schizophrenic disorders. However, the role of interfering variables such as IQ, attention, memory, and severity of the disorder has remained ambiguous.

METHODS

A theory of mind picture story comprising a sequencing task, a first and a second order false belief test, and a tactical deception test was given to a group of 23 patients with chronic disorganized schizophrenia and to 12 healthy control persons. In addition, a nonsocial picture story had to be sequenced. Severity of the psychopathology was measured by using the brief psychiatric rating scale (BPRS), IQ was estimated using the 'Mehrfachwahlwortschatztest' (MWT, multiple choice verbal comprehension test).

RESULTS

The schizophrenic group was impaired relative to controls on the theory of mind task, but not on the sequencing task of the nonsocial picture story. However, when controlled for IQ, no such difference was found. These findings were neither related to severity, duration, nor age at onset of the disorder.

CONCLUSIONS

Theory of mind deficits in schizophrenia may be related to domain general impairments, e.g., intelligence and working memory load, rather than reflecting a 'genuine' compromised mental state attribution similar to autistic spectrum disorders. Schizophrenic patients may, however, rather be impaired in how and when to apply strategic social reasoning. Further studies to investigate the nature of social deficiency in schizophrenia are warranted.

Where the rubber meets the road: The importance of implementation

Phillips & Silverstein argue that a range of cognitive disturbances in schizophrenia result from a deficit in cognitive coordination attributable to NMDA receptor dysfunction. We suggest that the viability of this hypothesis would be further supported by explicit implementation in a computational framework that can produce quantitative estimates of the behavior of both healthy individuals and individuals with schizophrenia.

Context, connection, and coordination: The need to switch

Context, connection, and coordination (CCC) describe well where the problems that apply to thought-disordered patients with schizophrenia lie. But they may be part of the experience of those with other symptom constellations. Switching is an important mechanism to allow context to be applied appropriately to changing circumstances. In some cases, NMDA-voltage modulations may be central, but gain and shift are also functions that monoaminergic systems express in CCC.

Synchronous dynamics for cognitive coordination: But how?

Although interesting, the hypotheses proposed by Phillips & Silverstein lack unifying structure both in specific mechanisms and in cited evidence. They provide little to support the notion that low-level sensory processing and high-level cognitive coordination share dynamic grouping by synchrony as a common processing mechanism. We suggest that more realistic large-scale modeling at multiple levels is needed to address these issues.

A wide-spectrum coordination model of schizophrenia

The target article presents a model for schizophrenia extending four levels of abstraction: molecules, cells, cognition, and syndrome. An important notion in the model is that of coordination, applicable to both the level of cells and of cognition. The molecular level provides an “implementation” of the coordination at the cellular level, which in turn underlies the coordination at the cognitive level, giving rise to the clinical symptoms.

Linking brain to mind in normal behavior and schizophrenia

To understand schizophrenia, a linking hypothesis is needed that shows how brain mechanisms lead to behavioral functions in normals, and also how breakdowns in these mechanisms lead to behavioral symptoms of schizophrenia. Such a linking hypothesis is now available that complements the discussion offered by Phillips & Silverstein (P&S).

Spatial integration in perception and cognition: An empirical approach to the pathophysiology of schizophrenia

Evidence for a dysfunction in cognitive coordination in schizophrenia is emerging, but it is not specific enough to prove (or disprove) this long-standing hypothesis. Many aspects of the external world are spatially mapped in the brain. A comprehensive internal representation relies on integration of information across space. Focus on spatial integration in the perceptual and cognitive processes will generate empirical data that shed light on the pathophysiology of schizophrenia.

Inferring contextual field interactions from scalp EEG

This commentary highlights methods for using scalp EEG to make inferences about contextual field interactions, which, in view of the target article, may be specially relevant to the study of schizophrenia. Although scalp EEG has limited spatial resolution, prior knowledge combined with experimental manipulations may be used to strengthen inferences about underlying brain processes. Both spatial and temporal context are discussed within the framework of nonlinear interactions. Finally, results from a visual contour integration EEG pilot study are summarized in view of a hypothesis that relates receptive field and contextual field processing to evoked and induced activity, respectively.

Reconciling schizophrenic deficits in top-down and bottom-up processes: Not yet

This commentary challenges the authors to use their computational modeling techniques to support one of their central claims: that schizophrenic deficits in bottom-up (Gestalt-type tasks) and top-down (cognitive control tasks) context processing tasks arise from the same dysfunction. Further clarification about the limits of cognitive coordination would also strengthen the hypothesis.

Cognitive coordination deficits: A necessary but not sufficient factor in the development of schizophrenia

The Phillips & Silverstein model of NMDA-mediated coordination deficits provides a useful heuristic for the study of schizophrenic cognition. However, the model does not specifically account for the development of schizophrenia-spectrum disorders. The P&S model is compared to Meehl's seminal model of schizotaxia, schizotypy, and schizophrenia, as well as the model of schizophrenic cognitive dysfunction posited by McCarley and colleagues.

NMDA-receptor hypofunction versus excessive synaptic elimination as models of schizophrenia

We propose that the primary cause of schizophrenia is a pathological extension of synaptic pruning involving local connectivity that unfolds ordinarily during adolescence. Computer simulations suggest that this pathology provides reasonable accounts of a range of symptoms in schizophrenia, and is consistent with recent postmortem and genetic studies. NMDA-receptors play a regulatory role in maintaining and/or eliminating cortical synapses, and therefore may play a pathophysiological role.

Is sensory gating a form of cognitive coordination?

Neurophysiological investigations of the past two decades have consistently demonstrated a deficit in sensory gating associated with schizophrenia. Phillips & Silverstein interpret this impairment as being consistent with cognitive coordination dysfunction. However, the physiological mechanisms that underlie sensory gating have not been shown to involve gamma-band oscillations or NMDA-receptors, both of which are critical neural elements in the cognitive coordination model.

Why do schizophrenic patients hallucinate?

Phillips & Silverstein argue that schizophrenia is a result of a deficit of the contextual coordination of neuronal responses. The authors propose that NMDA-receptors control these modulatory effects. However, hallucinations, which are among the principle symptoms of schizophrenia, imply a flaw in the interactions between neurons that is more fundamental than just a general weakness of contextual modulation.

Schizophrenic cognition: Taken out of context?

This commentary addresses: (a) the problems of definition which have been prominent in the use of the term context in schizophrenia research; (b) potentially useful distinctions and links with other theories of schizophrenic cognition; and (c) possible pathways to schizophrenic symptoms. It is suggested that at least two major aspects of the operation of context may be distinguished and that both may be impaired in schizophrenia.

Combating fuzziness with computational modeling

Phillips & Silverstein's ambitious link between receptor abnormalities and the symptoms of schizophrenia involves a certain amount of fuzziness: No detailed mechanism is suggested through which the proposed abnormality would lead to psychological traits. We propose that detailed simulation of brain regions, using model neural networks, can aid in understanding the relation between biological abnormality and psychological dysfunction in schizophrenia.

NMDA synapses can bias competition between object representations and mediate attentional selection

Phillips & Silverstein emphasize the gain-control properties of NMDA synapses in cognitive coordination. We endorse their view and suggest that NMDA synapses play a crucial role in biased attentional competition and (visual) working memory. Our simulations show that NMDA synapses can control the storage rate of visual objects. We discuss specific predictions of our model about cognitive effects of NMDA-antagonists and schizophrenia.

Persecutory delusions: a review and theoretical integration

Persecutory (paranoid) delusions are a frequently observed clinical phenomenon. In recent years, an increasing volume of research has attempted to explain these types of beliefs in terms of psychological mechanisms. Theories have emphasized early experience, perceptual abnormalities, motivational factors, and information-processing deficits. In this article we review relevant findings, including our own studies of the role of causal attributions and theory of mind deficits. We propose a new integrative model that builds on this work. The core of the model is an account of the way that causal attributions influence self-representations, which in turn influence future attributions: the attribution--self-representation cycle. We argue that biases in this cycle cause negative events to be attributed to external agents and hence contribute to the building of a paranoid world view. These abnormalities are amenable to investigation by functional neuroimaging, and recent studies have implicated specific areas of neuroactivation. However, these findings do not necessarily suggest that paranoid delusions are entirely biological in origin, and there is evidence that adverse early experience may play a role in determining the development of a cognitive vulnerability to paranoid thinking.

Can verbalization remedy the theory of mind deficit in schizophrenia?

Several studies provide convincing evidence of a specific deficit in the theory of mind (ToM) in some patients with schizophrenia. This ToM deficit consists of an inability to attribute relevant mental states to others, and studies suggest it has to be regarded as functional and remediable through the use of reinforced context processing. To investigate this, the present study compares the performances of 25 schizophrenics and 25 matched controls in a task exploring ToM before and after the introduction of verbal material into the task, initially conceived as nonverbal. All the controls and half of the schizophrenic subjects who did not initially perform at the best level remediated with verbalization, while 9 of the schizophrenics exhibited no remediation. These poor performers are characterized by a longer duration of illness. The cognitive plasticity and the characteristics of patients who do/do not remediate are discussed in the light of findings obtained with the Wisconsin Card Sorting Test. The clinical implication of these results is important since they suggest that some patients would benefit from cognitive rehabilitation in terms of their ability to attribute relevant mental states to others.

[Deficit of the theory-of-mind in schizophrenia: clinical concept and review of experimental arguments]

OBJECTIVE

This article synthesizes and discusses the clinical and experimental arguments for applying the concept of a theory-of-mind deficit to schizophrenia.

METHOD

The term "theory of mind" is defined. A review of literature on the hypothesis of a theory-of-mind deficit in schizophrenia is then presented. Clinical and experimental arguments are discussed. The article concludes with a summary of the issue.

RESULTS

The hypothesis of a theory-of-mind deficit in schizophrenia is convincing, particularly considering the most recent experimental evidence. This cognitive deficit explains the presence of schizophrenia symptoms such as delusions of influence and reference, problems in social adaptation, and signs of disorganized communication. Consideration is given to the roles played by situational ambiguity, the individual's intellectual level, and type of treatment.

CONCLUSION

The hypothesis of a theory-of-mind deficit has only recently been applied in schizophrenia research; it may have a strong impact on clinical practice. If its role in the onset of symptoms is to be better understood, explanatory models and experimental paradigms must be further refined.

A PET investigation of the attribution of intentions with a nonverbal task

Several authors have demonstrated that theory of mind is associated with a cerebral pattern of activity involving the medial prefrontal cortex. This study was designed to determine the cerebral regions activated during attribution of intention to others, a task which requires theory-of-mind skills. Eight healthy subjects performed three nonverbal tasks using comic strips while PET scanning was performed. One condition required subjects to attribute intentions to the characters of the comic strips. The other two conditions involved only physical logic and knowledge about objects' properties: one condition involved characters, whereas the other only represented objects. The comparison of the attribution of intention condition with the physical logic with characters condition was associated with rCBF increases in the right middle and medial prefrontal cortex including Brodmann's area (BA) 9, the right inferior prefrontal cortex (BA 47), the right inferior temporal gyrus (BA 20), the left superior temporal gyrus (BA 38), the left cerebellum, the bilateral anterior cingulate, and the middle temporal gyri (BA 21). The comparison of the physical logic with characters condition and the physical logic without characters condition showed the activation of the lingual gyri (BA 17, 18, 19), the fusiform gyri (BA 37), the middle (BA 21) and superior (BA 22, 38) temporal gyri on both sides, and the posterior cingulate. These data suggest that attribution of intentions to others is associated with a complex cerebral activity involving the right medial prefrontal cortex when a nonverbal task is used. The laterality of this function is discussed.

Investigating theory of mind in schizophrenia: influence of verbalization in disorganized and non-disorganized patients

The ability to attribute intentions to others was studied in 13 disorganized and 13 non-disorganized schizophrenic patients, 13 depressed and 13 normal controls. Subjects were asked to complete 28 comic strips requiring theory of mind skills by choosing one out of three answer cards. The answer cards were simple pictures in a first condition and short sentences in a second condition. This study, which used the cognitive neuropsychological approach, underlies the existence of a link between disorganization patterns in schizophrenia and a deficit in the attribution of intentions to others, independently of the pictorial or verbal form of the mode of answering. In addition, results show that the non-disorganized schizophrenic group, depressed and normal controls perform similarly in both pictorial/verbal conditions. The influence of the absence/presence of verbal material on a task investigating theory of mind in schizophrenia is discussed.

Gaze discrimination is unimpaired in schizophrenia

Interpersonal communication is largely dependent on interpretation of facial expression and emotion. Difficulties in face processing, and more specifically in gaze discrimination, have been described in schizophrenic patients. According to Baron-Cohen (Mindblindness. M.I.T. Press, Cambridge, MA, 1995), gaze discrimination relies on the functioning of a specific cognitive module, the Eye Direction Detector (EDD). It has been proposed [Rosse et al. (1994) Gaze discrimination in patients with schizophrenia: preliminary report. American Journal of Psychiatry 151, 919-921] that an impairment in gaze discrimination is present in schizophrenia, and plays a fundamental role in inducing the paranoid symptoms reported by many patients. However, in the previous studies, gaze direction detection and interpretation of gaze have never been completely dissociated. The present experiment attempts to test the schizophrenics' skill in a simple gaze direction detection task. A series of photographic portraits of models looking at different directions have been presented to 22 schizophrenic patients and 36 control subjects. For each portrait subjects were asked to determine whether gaze was directed to the right or to the left by pressing a keyboard key. A forced choice paradigm was used. No differences were reported between schizophrenic patients and control subjects. That is, in the present paradigm, schizophrenic patients did not show any specific impairment in detecting the direction of gaze of the portraits. The results are discussed according to the notion that a dissociation is present in schizophrenia between implicit and explicit processes. The present case illustrates how the more automatic elementary functions, such as the detection of gaze direction, may be spared in schizophrenic patients, whereas explicit cognitive functions are likely more affected.