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ABSTRACT: Time perception (TP) impairment in schizophrenia has been originally described by clinicians and afterwards addressed in laboratory. Previous studies generally observed that schizophrenia patients overestimate time and that their timing sensitivity is impaired. However, because of the disease cognitive impairments, no study until now allows to draw definitive conclusions about the nature of TP disturbances. The aim of this study is to isolate a genuine TP disorder in schizophrenia, i.e., a disorder that would be related to the functioning of an internal clock. The main hypothesis tested is that patients' internal clock runs faster than that of healthy controls. Twenty-five patients suffering from a first-episode of schizophrenia and twenty-five healthy controls performed an innovative task called method of dynamic stimuli, designed to measure the natural frequency (F(n)) of the internal clock, concomitant with a neuropsychological assessment. We observed no significant difference in F(n) between groups. Compared to controls, there was a marginally higher variability in time reproduction in patients. Patients' pattern of results and significant correlations between TP tasks and memory outcomes suggest that TP impairments are related to memory impairment in schizophrenia. These conclusions are supported by a growing literature showing that cognition is involved in TP in schizophrenia.
Psychiatry Research 08/2012; · 2.52 Impact Factor
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04/2011; , ISBN: 978-953-307-224-1
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ABSTRACT: Brain imaging studies of major depressive disorder have shown alterations in the brain regions typically involved in episodic memory, including the prefrontal cortex and medial temporal areas. Some studies of major depressive disorder have linked episodic memory performance to treatment response. In this study, we sought to identify brain regions whose activity, measured during the encoding of pictures, predicted symptomatic improvement after 8 weeks of citalopram treatment.
We included 20 unmedicated depressed patients. These patients performed an episodic recognition memory task during functional magnetic resonance imaging. During the encoding phase, 150 pictures depicting emotionally positive, negative or neutral content were presented, and the participants were required to classify each picture according to its emotional valence. The same 150 pictures were presented, along with 150 new ones, for a recognition task. We asked participants to distinguish the old pictures from the new ones. We assessed symptom severity by use of the 21-item Hamilton Rating Scale for Depression (HAM-D) at baseline and after 8 weeks of citalopram treatment. We performed subsequent memory effect analyses using SPM2 software. We explored the relation between brain activation during successful encoding of pictures and symptomatic improvement.
Patients showed a mean symptomatic improvement of 54.5% on the HAM-D after 8 weeks. Symptomatic improvement was significantly and positively correlated with picture recognition memory accuracy. We also found that the activity of the ventromedial prefrontal cortex and anterior cingulate cortex during successful encoding was significantly correlated with symptomatic improvement. Finally, we found greater activation in the ventromedial prefrontal cortex during the successful encoding of positive pictures in comparison with neutral pictures.
During the recognition memory task, 5 participants (among the best responders to treatment) were not included in the valence-specific analyses because they had very few errors. A more challenging task would have allowed the inclusion of most patients.
Different types of functional imaging paradigms have been used to explore whether the activity of specific brain regions measured at baseline is predictive of a better response to treatment in major depressive disorder. Among these regions, the medial prefrontal cortex and anterior cingulate cortex usually show the strongest predictive value. According to our results, the medial prefrontal cortex and anterior cingulate cortex could have an effect on treatment response in major depressive disorder by contributing to the successful encoding of positively valenced information.
Journal of psychiatry & neuroscience: JPN 05/2010; 35(3):152-62. · 5.34 Impact Factor
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ABSTRACT: Adaptive behaviours most often require adjustments over time, but many disorders lead to an inability to make such adjustments. This article reviews the fundamental concepts involved in the study of psychological timing and timing mechanisms. This is followed by a description of the research conducted on various time-related disorders in neuropsychology and neuropsychiatry. Following the presentation of timing disorders observed in patients with Parkinson's disease, the ensuing sections deal with the effects of medial temporal lobe lesions in individuals with amnesia and those with epilepsy. Finally, this article summarizes the results of contemporary research on timing disorders in persons who have depression as well as among individuals with schizophrenia. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Canadian Psychology 07/2006; 47(3):170-183. · 1.54 Impact Factor
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ABSTRACT: We investigated how does the structure of empty time intervals influence temporal processing. In experiment 1, the intervals to be discriminated were the silent durations marked by two sensory signals, both lasting 10 or 500 ms; these signals were two identical flashes (intramodal: VV), or one visual flash (V) followed by an auditory tone (A) (intermodal: VA). For the range of duration under investigation (standards = 0.2, 0.6, 1, or 1.4 s), the results indicated that both the marker length and sensory mode influenced discrimination, but no interaction between these variables or between one of these variables and standard duration was significant. In experiment 2, we compared, for each of four marker-type conditions (VV, AA, VA, AV; and standard = 1 s), intervals marked by two 10 ms signals with intervals marked by unequal signal length (markers 1 and 2 lasting 10 and 500 ms, or 500 and 10 ms). As in experiment 1, the results revealed significant marker-mode and marker-length effects, but no significant interaction between these variables. Experiment 3 showed that, for the same conditions as in experiment 2, perceived duration is not influenced by marker length and that the variability of interval reproductions does not depend on the perceived duration of intervals. The results are discussed in the light of a single-clock hypothesis: marker-length and marker-mode effects are presented as being non-temporal sources of variability associated mainly with sensory and memory processes.
Perception 02/2005; 34(1):45-58. · 1.31 Impact Factor
