Enhanced Persistency of Resting and Active Periods of Locomotor Activity in Schizophrenia

Abstract

Patients with schizophrenia frequently exhibit behavioral abnormalities associated with its pathological symptoms. Therefore, a quantitative evaluation of behavioral dynamics could contribute to objective diagnoses of schizophrenia. However, such an approach has not been fully established because of the absence of quantitative biobehavioral measures. Recently, we studied the dynamical properties of locomotor activity, specifically how resting and active periods are interwoven in daily life. We discovered universal statistical laws (“behavioral organization”) and their alterations in patients with major depressive disorder. In this study, we evaluated behavioral organization of schizophrenic patients (n = 19) and healthy subjects (n = 11) using locomotor activity data, acquired by actigraphy, to investigate whether the laws could provide objective and quantitative measures for a possible diagnosis and assessment of symptoms. Specifically, we evaluated the cumulative distributions of resting and active periods, defined as the periods with physical activity counts successively below and above a predefined threshold, respectively. Here we report alterations in the laws governing resting and active periods; resting periods obeyed a power-law cumulative distribution with significantly lower parameter values (power-law scaling exponents), whereas active periods followed a stretched exponential distribution with significantly lower parameter values (stretching exponents), in patients. Our findings indicate enhanced persistency of both lower and higher locomotor activity periods in patients with schizophrenia, probably reflecting schizophrenic pathophysiology.

Quantitative Psychomotor Dysfunction in Schizophrenia: A Loss of Drive, Impaired Movement Execution or Both?

“…This association between negative symptomatology and AL has been reported repeatedly in previous studies [3,6,14,15,16]. However, these studies failed to take the multidimensionality of the negative syndrome into account.…”

“…Although associations between negative symptoms and AL have been reported rather consistently [3,6,14,15,16], Walther et al [14] failed to find an association between AL and the motor items of the Positive and Negative Syndrome Scale (PANSS), i.e. excitement, motor retardation and disturbance of volition.…”

Less Structured Movement Patterns Predict Severity of Positive Syndrome, Excitement, and Disorganization

“…5 Indeed, locomotor hyperactivity has widely been used to model positive symptoms of schizophrenia in rodents because of its association with hyperdopaminergic states. 37 Our findings and those of Sano and colleagues 27 call for the exploration of temporal patterns of animal motor behavior, which might become an interesting model for positive symptoms in schizophrenia. For larger scale rest-activity patterns, this has been already attempted.…”

“…The authors reported less variable behavioral movement patterns in schizophrenia patients. 27 This study did not find associations of behavioral patterns with psychopathology, probably due to the small sample size and the inclusion of data collected during sleep. In our study, the pattern of locomotor behavior in 100 schizophrenia spectrum patients was analyzed in 2 60-min periods at very small time scales, ie 2-s intervals.…”

“…5 The disruption of behavioral patterns has been suggested to be valuable for translational research. 5,27 Particularly, the spatial distribution of movement was useful to separate hyperactivity as seen in mania and schizophrenia from exploratory behavior in mania. 5 Indeed, locomotor hyperactivity has widely been used to model positive symptoms of schizophrenia in rodents because of its association with hyperdopaminergic states.…”