Clinical features of latent inhibition in schizophrenia (original) (raw)
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Latent inhibition as a model of schizophrenia: from learning to psychopathology
2003
In schizophrenia, attentional processes may be altered and become the basis of another symptomatology such as delirium and hallucinations. One of the experimental approaches to the study of attentional processes employs the phenomenon of latent inhibition. Behaviourally, latent inhibition is expressed as a delay or difficulty in learning the relationship between stimuli due to prior experience of the subject with one of the inconsequential stimuli. This learning phenomenon fulfils an adaptive function that enables the organism to release attention from irrelevant stimuli. Schizophrenics do not show this latent inhibition effect due to attentional alterations, that is, they have selective attention difficulties. Clinical data coincide with results obtained from both animals and normal subjects and with data from psychopharmacological studies. Most of the studies show that the dopaminergic system plays an important role in latent inhibition and therefore would support the dopaminergic hypothesis of schizophrenia. Furthermore, latent inhibition is used as a model to evaluate the mechanisms of antipsychotic drug action, as well as for the study of the aetiology of schizophrenia. Finally, latent inhibition opens a line of research in cognitive inhibition processes in schizotypy and the possibility of studying other psychopathological disorders. The model proposed is based on experimental, neurochemical and clinical premises that make it a promising topic of future for research.
Enhancement of latent inhibition in patients with chronic schizophrenia
Behavioural Brain Research, 2009
Objectives: Latent inhibition (LI) refers to the retarding effects of inconsequential stimulus preexposure on subsequent conditioning to that stimulus, and reflects the organism's capacity to ignore irrelevant stimuli. LI is disrupted in schizophrenia patients, due to faster learning of the association between the conditioned stimulus (CS) and an unconditioned stimulus (US). It was recently proposed that LI has an additional pole of abnormality indicated by LI persistence. Methods: Two experiments were performed to test this hypothesis. Both experiments applied a new within-subject, visual recognition LI procedure in which the association between a cue (CS) and the target (US) is acquired. In Exp 1 the task was applied to healthy volunteers (n = 21). In Exp 2 chronic schizophrenia patients (n = 19) were compared to control subjects (n = 20). Results: In Exp 1 the subjects showed LI in the initial trials of cue-target pairings, and an attenuation of the phenomenon at later trials. In Exp 2 control subjects showed a pattern of response comparable to the subjects of Exp 1, while the patients showed LI only on the later trials of the task. Conclusions: This result suggests that patients with chronic schizophrenia showed LI persistence. The possible advantages of the new LI paradigm are discussed.
The relation between latent inhibition and symptom-types in young schizophrenics
Behavioural Brain Research, 2004
Latent inhibition (LI), retarded conditioning to a stimulus that has been previously repeatedly presented without reinforcement, was examined in young schizophrenics and normal controls using a within-subject visual search task. Healthy controls exhibited the usual LI effect. LI was potentiated in schizophrenics who simultaneously exhibited high levels of negative symptoms and low levels of positive symptoms. Schizophrenic groups with other combinations of positive and negative symptoms did not differ from controls. The pattern of data suggests that past inconsistencies in the LI-schizophrenia literature may be the result of opposing processes that are associated with positive and negative symptoms.
Latent inhibition in schizophrenia
Schizophrenia Research, 1996
Latent inhibition (LI) refers to the retarded acquisition of a conditioned response that occurs if the subject being tested is first preexposed to the to-be-conditioned stimulus (CS) without the paired unconditioned stimulus (UCS). Because the 'irrelevance' of the to-be-conditioned stimulus is established during non-contingent preexposure, the slowed acquisition of the CS-UCS association is thought to reflect the process of overcoming this learned irrelevance. Latent inhibition has been reported to be diminished in acutely hospitalized schizophrenia patients. If acutely hospitalized schizophrenia patients are preexposed to the CS, they learn the association as fast as, and perhaps faster than, patients who are not preexposed to the CS. This finding has been interpreted as reflecting the inability of acute schizophrenia patients to ignore irrelevant stimuli. In this study, the LI paradigm was identical to the one used in previous reports of LI deficits in schizophrenia patients . Latent inhibition was observed in normal control subjects (n=73), including individuals identified as 'psychosis-prone' based on established screening criteria, and in anxiety (n= 19) and mood disorder (n= 13) patients. Learning scores (trials to criterion) in 'acutely' hospitalized as well as 'chronic' hospitalized schizophrenia patients (n=45) were significantly elevated in both preexposed and non-preexposed subjects, compared to controls. Acute schizophrenia patients exhibited intact LI. Separate cohorts of acute and chronic schizophrenia patients (n=23) and normal controls (n=34) exhibited intact LI when tested in a new, easier-to-acquire computerized LI paradigm. These results fail to identify specific LI deficits in schizophrenia patients, and raise the possibility that previously observed LI deficits in schizophrenia patients may reflect, at least in part, performance deficits related to learning acquisition.
Latent inhibition in low and high “psychotic-prone” normal subjects
Personality and Individual Differences, 1992
were performed with adult human subjects which demonstrated latent inhibition, a retardation of learning following preexposure to a subsequently relevant stimulus. The first study, using an auditory procedure, replicated Baruch, Hemsley and Gray's (1988a, Personality and Individual Differences, 9; finding that high "psychotic-prone" normals, as assessed by Eysenck's Psychoticism Scale and Claridge and Broks' STA Scale, exhibit an attenuated latent inhibition effect as compared to low "psychotic-prones". The second study, using a newly developed visual procedure, obtained similar results. The attenuation of latent inhibition in high "psychotic-prone" normals was discussed in relation to attentional dysfunction in schizophrenia and the animal dopamine model of schizophrenia.
Latent inhibition in first episode of schizophrenia
Schizophrenia Research, 2003
Cognitive deficits have been repeatedly reported in schizophrenia. However, auto-questionnaires on the patients' perception about their own cognitive deficits are rarely used. The aim of this study is to verify that the subjective perception of cognitive deficits in schizophrenia patients does not always correspond to the objective measures of their cognitive deficits. 71 patients fulfilling DSM-IV criteria for schizophrenia were evaluated using an objective measure (CANTAB), and a subjective measure (SSTICS), which is a 21-items scale allowing a quantitative approach to the subjective cognitive dimension of schizophrenia (Stip et al 2001,2002). Memory, attention and executive function were evaluated with a series of computerized tests, the Cambridge Neuropsychological Test Automated Battery (CANTAB): Paired Associates Learning (PAL) Test, the Reaction Time Test Socking of Cambridge. The total score on SSTICS was 26.t4 (SD=12.00) matching with total score of 25.94 (SD= 9.72) from our previous study (Mancini, 2002). The reaction time (RT) did not correlate with any of the SSTICS variables. The explicit visuo-spatial memory performance (PAL) was negatively correlated with SSTICS scores: Attention (r=-0.3420), Total (r=-0.3697) and executive Functions (Exf) (r=-0.4487). Planning abilities correlated with most of the SSTICS variables. These results show that indeed there is a conflict between perceived and actual objective deficits, and reflect a dysfunction in the control and monitoring cognitive processes. Patients with schizophrenia seem to have a different representation of their cognitive system.
Personality and Individual Differences, 2009
Latent inhibition (LI) refers to poorer learning for a previously exposed, irrelevant stimulus (PE) than for a non-preexposed, novel stimulus (NPE). According to recent theoretical accounts of this phenomenon, positive schizotypal symptoms should attenuate LI while negative symptoms should produce a persistent LI. To test this prediction, non-clinical participants (N = 115), randomly allocated to either PE or NPE group, performed a visual-search LI task and completed psychometric measures of schizotypy. Overall, fewer correct responses in the PE group than in the NPE group suggested a LI effect. Subsequent regression analyses showed that in the PE group positive schizotypy was associated with attenuated LI whereas negative schizotypy was associated with enhanced LI. To the best of our knowledge, this study provides the first evidence for a bi-directional model of LI modulation in schizotypy.
Schizophrenia Bulletin, 2005
Latent inhibition (LI) is demonstrated when a previously unattended/inconsequential stimulus is less effective in a new learning situation than a novel stimulus. In rats and humans, LI is reduced by dopamine agonists and increased by dopamine antagonists. In addition, LI is attenuated in actively psychotic schizophrenia patients, thus conferring strong predictive validity to the animal LI preparation for schizophrenia. However, the validity of the attentional construct in the LI model of schizophrenia dysfunction depends on confirming two assumptions: that animal and human LI share a common process, and that the process is related to selective attention. Evidence to support both assumptions is presented, followed by a description of a conditioned attention theory that emphasizes the role of initial levels of attention elicited by repeated relevant and irrelevant stimuli, and the differences between these levels in schizophrenia and normal groups.
Latent inhibition and context change in psychometrically defined schizotypy
Personality and Individual Differences, 2004
The disruption of latent inhibition within the schizophrenia spectrum has often been interpreted either as a result of increased attentional distractibility (attentional account) or as a result of deficient interference of past associations (associative account). The aim of the present investigation was to test competing predictions, as derived from the above theoretical accounts. In a visual search paradigm of latent inhibition, accuracy was examined as a function of prior experience with the target, and psychometrically defined schizotypy. In Experiment 1 (N ¼ 60), no context change was introduced. In accord with past evidence, latent inhibition was found to be intact in low-, but disrupted in high-schizotypy scorers, a result predicted both by attentional and associative accounts. In Experiment 2 (N ¼ 60), a context change was introduced. As predicted by past evidence, latent inhibition was disrupted in low-schizotypy scorers. However, latent inhibition was found to be intact in high-schizotypy scorers, a finding accommodated by attentional, but not associative accounts. Theoretical implications and alternative interpretations are also considered.
Latent Inhibition and Overswitching in Schizophrenia
Schizophrenia Bulletin, 2004
Attention disorders in schizophrenia are manifested in two different ways. On the one hand, the schizophrenia patient tends to keep a learned response even after it ceases to be relevant (perseveration). On the other hand, the schizophrenia patient tends to replace an adaptive response without being given a reason to do so (overswitching). In the present study, overswitching was investigated