When you hallucinate an object, you are not in the normal sort of concurrent causal sensory interaction with that object. It's standardly further inferred that the hallucinated object does not actually exist. But the lack of normal concurrent causal sensory interaction does not imply that there does not exist an object that is hallucinated. It might be a past‐perceived object. In this paper, I argue that this claim holds for at least some interesting cases of hallucination. Hallucinations generated by misleading (...) cues (e.g. ‘seeing’ Kanizsa triangles), hallucinations of Charles Bonnet Syndrome patients, and dreams are experiences of past‐perceived objects. (shrink)

In Real Hallucinations, Matthew Ratcliffe offers a philosophical examination of the structure of human experience, its vulnerability to disruption, and how it is shaped by relations with other people. He focuses on the seemingly simple question of how we manage to distinguish among our experiences of perceiving, remembering, imagining, and thinking. To answer this question, he first develops a detailed analysis of auditory verbal hallucinations (usually defined as hearing a voice in the absence of a speaker) and thought insertion (somehow (...) experiencing one's own thoughts as someone else's). He shows how thought insertion and many of those experiences labeled as "hallucinations" consist of disturbances in a person's senseof being in one type of intentional state rather than another. Ratcliffe goes on to argue that such experiences occur against a backdrop of less pronounced but wider-ranging alterations in the structure of intentionality. In so doing, he considers forms of experience associated with trauma, schizophrenia, and profound grief. The overall position arrived at is that experience has an essentially temporal structure, involving patterns of anticipation and fulfillment that are specific to types of intentional states and serve to distinguish them phenomenologically. Disturbances of this structure can lead to various kinds of anomalous experience. Importantly, anticipation-fulfillment patterns are sustained, regulated, and disrupted by interpersonal experience and interaction. It follows that the integrity of human experience, including the most basic sense of self, is inseparable from how we relate to other people and to the social world as a whole. (shrink)

Based on recent insight into the thalamocortical system and its role in perception and conscious experience, a unified pathophysiological framework for hallucinations in neurological and psychiatric conditions is proposed, which integrates previously unrelated neurobiological and psychological findings. Gamma-frequency rhythms of discharge activity from thalamic and cortical neurons are facilitated by cholinergic arousal and resonate in networks of thalamocortical circuits, thereby transiently forming assemblies of coherent gamma oscillations under constraints of afferent sensory input and prefrontal attentional mechanisms. If perception is based (...) on synchronisation of intrinsic gamma activity in the thalamocortical system, then sensory input to specific thalamic nuclei may merely play a constraining role. Hallucinations can be regarded as underconstrained perceptions that arise when the impact of sensory input on activation of thalamocortical circuits and synchronisation of thalamocortical gamma activity is reduced. In conditions that are accompanied by hallucinations, factors such as cortical hyperexcitability, cortical attentional mechanisms, hyperarousal, increased noise in specific thalamic nuclei, and random sensory input to specific thalamic nuclei may, to a varying degree, contribute to underconstrained activation of thalamocortical circuits. The reticular thalamic nucleus plays an important role in suppressing random activity of relay cells in specific thalamic nuclei, and its dysfunction may be implicated in the biological vulnerability to hallucinations in schizophrenia. Combined with general activation during cholinergic arousal, this leads to excessive disinhibition in specific thalamic nuclei, which may allow cortical attentional mechanisms to recruit thalamic relay cells into resonant assemblies of gamma oscillations, regardless of their actual sensory input, thereby producing an underconstrained perceptual experience. Key Words: Charles Bonnet syndrome; gamma oscillations; hallucinations; late paraphrenia; Lewy body dementia; perception; schizophrenia; thalamocortical system. (shrink)

How is it that many schizophrenics identify certain instances of verbal imagery as hallucinatory? Most investigators have assumed that alterations in sensory features of imagery explain this. This approach, however, has not yielded a definitive picture of the nature of verbal hallucinations. An alternative perspective suggests itself if one allows the possibility that the nonself quality of hallucinations is inferred on the basis of the experience of unintendedness that accompanies imagery production. Information-processing models of “intentional” cognitive processes call for abstract (...) planning representations that are linked to goals and beliefs. Unintended actions - and imagery - can reflect planning disruptions whereby cognitive products do not cohere with concurrent goals. A model of schizophrenic speech disorganization is presented that postulates a disturbance of discourse planning. Insofar as verbal imagery can be viewed as inwardly directed speech, a consequence of such planning disturbances could be the production of unintended imagery. This link between the outward disorganization of schizophrenic speech and unintended verbal imagery is statistically supported by comparing the speech behavior of hallucinating and nonhallucinating schizophrenics. Studies of “borderline” hallucinations during normal, “goal-less” relaxation and drowsiness suggest that experiential unintendedness leads to a nonpathological variant of hallucinatory otherness that is correctable upon emerging from such passive cognitive states. This contrasts with the schizophrenic case, where nonconcordance with cognitive goals reinforces the unintendedness of verbal images and sustains the conviction of an external source. This model compares favorably with earlier models of verbal hallucinations and provides further evidence for a language production disorder in many schizophrenics.Short Abstract: How is it that many schizophrenics identify certain instances of verbal imagery as hallucinatory? This paper proposes that the critical feature identifying hallucinations is the experience of unintendedness. This experience is nonpathological during passive conscious states but pathological if occurring during goal-directed cognitive processing. A model of schizophrenic speech disorganization is presented that postulates a disturbance of discourse planning that specifies communicative intentions. These alterations could generate unintended verbal imagery as well. Statistical data are offered to support the model, and relevant empirical studies are reviewed. (shrink)

Relationalism maintains that mind-independent objects are essential constituents of veridical perceptual experiences. According to the argument from hallucination, relationalism is undermined by perfect hallucinations, experiences that are introspectively indistinguishable from veridical perceptual experiences but lack an object. Recently, a new wave of relationalists have responded by questioning whether perfect hallucinations are possible: what seem to be perfect hallucinations may really be something else, such as illusions, veridical experiences of non-obvious objects, or experiences that are not genuinely possible. This paper argues (...) that however well new wave relationalism may handle brains in vats, drug users “seeing” pink elephants, and other extraordinary hallucinations, it struggles to accommodate mundane hallucinations, such as “hearing” your child cry out from the room down the hall when she is actually sound asleep or “feeling” vibrations on your thigh even when your phone isn't in your pocket. Mundane hallucinations are best explained as byproducts of noise in the perceptual system, and noise-induced hallucinations are resistant to the strategies that new wave relationalists deploy to explain away other hallucinations. Mundane hallucinations can thus underpin an especially powerful version of the argument from hallucination. (shrink)

Ordinary language and scientific language enable us to speak about, in a singular way, what we recognize not to exist: fictions, the contents of our hallucinations, abstract objects, and various idealized but nonexistent objects that our scientific theories are often couched in terms of. Indeed, references to such nonexistent items-especially in the case of the application of mathematics to the sciences-are indispensable. We cannot avoid talking about such things. Scientific and ordinary languages thus enable us to say things about Pegasus (...) or about hallucinated objects that are true, such as "Pegasus was believed by the ancient Greeks to be a flying horse," or "That elf I'm now hallucinating over there is wearing blue shoes." Standard contemporary metaphysical views and semantic analyses of singular idioms on offer in contemporary philosophy of language have not successfully accommodated these routine practices of saying true and false things about the nonexistent while simultaneously honoring the insight that such things do not exist in any way at all. That is, philosophers often feel driven to claim that such objects do exist, or they claim that all our talk isn't genuine truth-apt talk, but only pretence. This book reconfigures metaphysics in radical ways that allow the accommodation of our ordinary ways of speaking of what does not exist while retaining the absolutely crucial presupposition that such objects exist in no way at all, have no properties, and so are not the truth-makers for the truths and falsities that are about them. (shrink)

In this paper, I examine the so-called disjunctive views on hallucinations. I argue that neither of the options open to the disjunctivist is capable of accommodating basic phenomenological facts about hallucinatory experiences and the explanatory demands behind the classical argument from hallucination. A positive characterization of the hallucinatory case is not attractive to a disjunctivist once she is disposed to accept certain commonalities with veridical experiences. Negative disjunctivism glosses the hallucinatory disjunct in terms of indiscriminability. I will argue that this (...) move either renounces to characterize phenomenally the hallucinatory experience or does not take seriously questions about why indiscriminability is possible in the phenomenal realm. (shrink)

What we perceive is the product of an intrinsic process and not part of external physical reality. This notion is consistent with the philosophical position of transcendental idealism but also agrees with physiological findings on the thalamocortical system. -Frequency rhythms of discharge activity from thalamic and cortical neurons are facilitated by cholinergic arousal and resonate in thalamocortical networks, thereby transiently forming assemblies of coherent oscillations under constraints of sensory input and prefrontal attentional mechanisms. Perception and conscious experience may be based (...) on such assemblies and sensory input to thalamic nuclei plays merely a constraining role in their formation. In schizophrenia, the ability of sensory input to modulate self-organisation of thalamocortical activity may be generally reduced. If during arousal thalamocortical self-organisation is underconstrained by sensory input, then attentional mechanisms alone may determine the content of perception and hallucinations may arise. (shrink)

Numbers -- Hallucinations -- Fictions -- Scientific languages, ontology, and truth -- Truth conditions and semantics.

Hallucinations are among the most impressive of psychopathological symptoms and may appear in all the sensory modalities. They are the most common symptom in schizophrenia, where patients usually experience auditory hallucinations, often hearing voices which speak to them in direct communication or in the form of running commentary. One of the major research strategies in psychopathology during the last years has become the neuropsychological reconstruction of psychopathological symptoms in order to detect basic “core” deficits of the different symptoms. Given the (...) successful identification of such core deficits, they may then serve as heuristic tools to identify candidate brain regions of putative pathology. These brain sites in turn can be explored with respect to their impact for the pathogenesis of schizophrenia. Among these neuropsychological approaches, one of the most prominent concepts reconstructing schizophrenic symptomatology is the concept of a self-monitoring disturbance, based on the conceptual and empirical work of the group around Christopher Frith. Although this conceptualization is evidence-based and appears plausible, it does not fully explain the high degree of certainty or confidence with which schizophrenic patients usually judge the reality status of their hallucinations and the frequency with which the latter might occur. The concept of self-monitoring disturbance thus provides a necessary but not a sufficient theoretical account of how hallucinations are generated. (shrink)

Hallucinations are among the most impressive of psychopathological symptoms and may appear in all the sensory modalities. They are the most common symptom in schizophrenia, where patients usually experience auditory hallucinations, often hearing voices which speak to them in direct communication or in the form of running commentary. One of the major research strategies in psychopathology during the last years has become the neuropsychological reconstruction of psychopathological symptoms in order to detect basic “core” deficits of the different symptoms. Given the (...) successful identification of such core deficits, they may then serve as heuristic tools to identify candidate brain regions of putative pathology. These brain sites in turn can be explored with respect to their impact for the pathogenesis of schizophrenia. Among these neuropsychological approaches, one of the most prominent concepts reconstructing schizophrenic symptomatology is the concept of a self-monitoring disturbance, based on the conceptual and empirical work of the group around Christopher Frith. Although this conceptualization is evidence-based and appears plausible, it does not fully explain the high degree of certainty or confidence with which schizophrenic patients usually judge the reality status of their hallucinations and the frequency with which the latter might occur. The concept of self-monitoring disturbance thus provides a necessary but not a sufficient theoretical account of how hallucinations are generated. (shrink)

Case Reports Int J Psychoanal -/- . 1989:70 ( Pt 3):461-79. Negative hallucinations, other irretrievable experiences and two functions of consciousness L W Brakel -/- PMID: 2793325 -/- Abstract -/- After providing a psychodynamic exploration of negative hallucinations in four clinical cases, the focus of this paper was broadened in an attempt to understand the mechanism of negative hallucination. To this end, after defining the term 'irretrievable experiences', two other examples--preconscious perceptions and infantile amnesia, both analogues to negative hallucination--were examined. (...) A discussion followed concerning two types of 'consciousness': 'consciousness' as a synonym for 'awareness' and 'consciousness' as a distinct psychological state. Next, the role of different functions of each sort of consciousness in the processes of conferring, fixing and retrieving mental contents within particular categories of experience was taken up. Finally, integrating developmental aspects of these same functions, explanations were offered regarding the mechanisms involved in preconscious perception, infantile amnesia and negative hallucinations. -/- PubMed. (shrink)

This commentary takes a closer look at how “constructive models of subjective perception,” referred to by Collerton et al. (sect. 2), might contribute to the Perception and Attention Deficit (PAD) model. It focuses on the neuronal mechanisms that could mediate hallucinations, or false inference – in particular, the role of cholinergic systems in encoding uncertainty in the context of hierarchical Bayesian models of perceptual inference (Friston 2002b; Yu & Dayan 2002).

Chris Frith has argued that a loss of the sense of agency is central to schizophrenia. This suggests a connection between hallucinations and delusions on the one hand, and the misidentification of the subject’s imaginings as perceptions and beliefs on the other. In particular, understanding the mechanisms that underlie imagination may help us to explain the puzzling phenomena of thought insertion and withdrawal. Frith sometimes states his argument in terms of a loss of metarepresentational capacity in schizophrenia. I argue that (...) this formulation is unhelpful. (shrink)

Waking hallucinations suggest mechanisms of dream initiation and maintenance. Visual association cortex activation, yielding poorly attended-to, visually ambiguous dream environments, suggests conditions favoring hallucinosis. Attentional and visual systems, coactivated during sleep, may generate imagery that is inserted into virtual environments. Internally consistent dreaming may evolve from successive, contextually evoked images. Fluctuating arousal and context-evoked imagery may help explain dream features.

What we perceive is the product of an intrinsic process and not part of external physical reality. This notion is consistent with the philosophical position of transcendental idealism but also agrees with physiological findings on the thalamocortical system. -Frequency rhythms of discharge activity from thalamic and cortical neurons are facilitated by cholinergic arousal and resonate in thalamocortical networks, thereby transiently forming assemblies of coherent oscillations under constraints of sensory input and prefrontal attentional mechanisms. Perception and conscious experience may be based (...) on such assemblies and sensory input to thalamic nuclei plays merely a constraining role in their formation. In schizophrenia, the ability of sensory input to modulate self-organisation of thalamocortical activity may be generally reduced. If during arousal thalamocortical self-organisation is underconstrained by sensory input, then attentional mechanisms alone may determine the content of perception and hallucinations may arise. (shrink)

Chris Frith has argued that a loss of the sense of agency is central to schizophrenia. This suggests a connection between hallucinations and delusions on the one hand, and the misidentification of the subject’s imaginings as perceptions and beliefs on the other. In particular, understanding the mechanisms that underlie imagination may help us to explain the puzzling phenomena of thought insertion and withdrawal. Frith sometimes states his argument in terms of a loss of metarepresentational capacity in schizophrenia. I argue that (...) this formulation is unhelpful. (shrink)

Many take the possibility of hallucinations to imply that a relationalist account, according to which perceptual experiences are constituted by direct relations to ordinary mind-independent objects, is false. The common reaction among relationalists is to adopt a disjunctivist view that denies that hallucinations have the same nature as perceptual experiences. This paper proposes a non-disjunctivist response to the argument from hallucination by arguing that the alleged empirical and a priori evidence in support of the possibility of hallucinations is inconclusive. A (...) corollary upshot of the article is that whether hallucinations are possible or not is still an open empirical question. (shrink)

Behrendt & Young (B&Y) suggest that hallucinations occur as a result of decoupling of neuronal populations from sensory control. I propose that such a decoupling is in fact a constant feature of brain activity, even under nonpathological conditions. This position is justified by evidence from recent neurophysiological recording studies. I suggest that hallucinations arise because of a breakdown in segregation of internally and externally generated activity in a neuronal population.

This paper examines the standard conceptualizations of the notion of hallucination in light of various non-ordinary phenomenological patterns associated with altered states of consciousness induced by psychoactive agents. It is argued that in general, the conceptualizations encountered in the literature do not do justice to the richness and complexity that the psychological phenomenology actually exhibits. A close inspection of this phenomenology reveals some pertinent distinctions which are usually not made in the scientific literature. On the one hand, the discussion is (...) based on first-hand experiences and, on the other hand, it is grounded in empirical and theoretical cognitive investigations of the phenomenology of human consciousness. Theoretically, the discussion is grounded in an approach highlighting the centrality of experience, meaning and action in cognition. (shrink)

REM sleep behaviour disorder is a REM sleep-related parasomnia which may be considered a “dissociated state of wakefulness and sleep”, given that conflicting elements of REM sleep and of wakefulness coexist during the episodes, leading to motor and behavioural manifestations reminiscent of an enacted dream. RBD has been reported in association with α-synucleinopathies: around a third of patients with Parkinson’s disease have full-blown RBD.Recent data indicate that PD patients with RBD are more prone to hallucinations than PD patients without this (...) parasomnia. However it is still not clear why RBD in PD is associated with an increased prevalence of VHs.Data exist which suggest that visual hallucinations in PD may be the result of untimely intrusions of REM visual imagery into wakefulness. RBD, which is characterised by a REM sleep dissociation pattern, might be a condition that particularly favours such intrusions. However, other hypotheses may be advanced. In fact, deficits in attentional, executive, visuoperceptual and visuospatial abilities have been documented in RBD and found to occur far more frequently in PD with RBD than in PD without RBD. Neuropsychological deficits involving visual perception and attentional processes are thought to play an important role in the pathophysiology of VHs. On this basis, RBD in PD could be viewed as a contributory risk factor for VHs. (shrink)

Multidisciplinary studies indicate that auditory hallucinations may arise from speech perception neurocircuitry without disrupted theory of mind capacities. Computer simulations of excessive pruning in speech perception neural networks provide a model for these hallucinations and demonstrate that connectivity reductions just below a “psychotogenic threshold” enhance information processing. These data suggest a process whereby vulnerability to schizophrenia is maintained in the human population despite reproductive disadvantages of this illness.

The target article, in stressing the balance between neurobiological and psychological factors, makes a compelling argument in support of a continuum of perceptual and hallucinatory experience. Nevertheless, two points need to be addressed. First, the authors are probably underestimating the incidence of hallucinations in the normal population. Second, one should consider the role of absorption as a predisposing factor for hallucinations.

Chris Frith has argued that a loss of the sense of agency is central to schizophrenia. This suggests a connection between hallucinations and delusions on the one hand, and the misidentification of the subject’s imaginings as perceptions and beliefs on the other. In particular, understanding the mechanisms that underlie imagination may help us to explain the puzzling phenomena of thought insertion and withdrawal. Frith sometimes states his argument in terms of a loss of metarepresentational capacity in schizophrenia. I argue that (...) this formulation is unhelpful. (shrink)

We tested Collerton et al.'s model of visual hallucinations by re-examining a data set for correlations between visual hallucinations and measures of attentional function in schizophrenia patients. These data did not support their model. We suggest that cortical hyperexcitability plays an important role in hallucinations, and propose an alternative model that links evidence for cortical hyperexcitability with abnormal neural dynamics.

There are strong resemblances between the neurobiological characteristics of hallucinations occurring in the particular case of schizophrenia and the hallucinatory activity observed during the rapid-eye-movement (dreaming) sleep stage: the same prefrontal dorsolateral deactivation; forebrain disconnectivity and disinhibition; sensory deprivation; and acetylcholine, monoamine, and glutamate modifications.

Behrendt & Young's (B&Y's) novel “unifying model” of hallucinations, although comprehensive, fails to incorporate research into the possible role of 5-HT2A receptors in the mode of action of novel “atypical” antipsychotic drugs (which treat hallucinations effectively), and into the role of such receptors, which are located in thalamocortical circuits, in mediating drug-induced hallucinations.

My primary aim in this article is to provide a philosophical account of the unity of hallucinations, which can capture both perceptual hallucinations (which are subjectively indistinguishable from perceptions) and non-perceptual hallucinations (all others). Besides, I also mean to clarify further the division of labour and the nature of the collaboration between philosophy and the cognitive sciences. Assuming that the epistemic conception of hallucinations put forward by M. G. F. Martin and others is largely on the right track, I will (...) focus on two main tasks: (a) to provide a satisfactory phenomenology of the subjective character of perceptions and perceptual hallucinations and (b) to redress the philosophers’ neglect of non-perceptual hallucinations. More specifically, I intend to apply one of the central tenets of the epistemic conception—that hallucinations can and should be positively characterised in terms of their phenomenological connections to perceptions—to non-perceptual hallucinations as well. That is, I will try to show that we can positively specify the class of non-perceptual hallucinations by reference to the distinctive ways in which we first-personally experience them and perceptions in consciousness. The task of saying more about their underlying third-personal nature may then be left to the cognitive sciences. (shrink)

Frédéric Chopin is the epitome of the romantic artist; he had a chronic pulmonary disease that ultimately caused his death at the age of 39. An overlooked neurological condition is discussed in this paper. We consider the possibility of a temporal lobe epilepsy, as throughout his life Chopin had hallucinatory episodes, which can accompany seizure disorders.