A neuroanatomical basis for the frequency of discrete spontaneous activities in schizophrenia

Abstract

Limited behavioural repertoire impacts quality of life in chronic schizophrenia. We have previously shown that the amount of movement exhibited by patients with schizophrenia is positively correlated with the volume of left anterior cingulate cortex and that this quantity of movement can be increased by modafinil. However, increased movement in itself may be of limited clinical significance. Hence, we sought to analyse the 'structure' of spontaneous movement in patients with schizophrenia and to examine whether the chunking of spontaneous activity has a neuroanatomical basis. 'Actiwatches' were used to record spontaneous motor activity over a 20 hour period in sixteen male patients with schizophrenia. Time-series data were analysed for the number of discrete spontaneous activities, which might indicate a degree of structure to ongoing activity. Subjects underwent a whole-brain structural MRI scan. The 'number of discrete movement epochs' correlated with volumes of regions within bilateral rostro-ventral putamen and temporal poles. These data suggest that in people with schizophrenia the volume of bilateral putamen may influence the complexity of their behaviours, as distinct from the overall amount of behaviour. The results are presented in the context of a large body of previous research examining the role of the basal ganglia in motor and cognitive pattern generation.

Fig. (1)

Examples of ‘low’ variability (top) and ‘high’ variability (bottom) actiwatch traces. Data have been normalised to 100% to facilitate direct between-subject comparison. Thus vertical black bars (left hand Y-axis) sum to 100, and yellow line (right hand Y-axis) ascends to 100% for each subject across 2400, thirty-second epochs (i.e. 20 hours).

Fig. (2)

Bilateral rostro-ventral putamen (top row) and middle / superior temporal gyrus (bottom row) volumes positively correlated with number of discrete movement epochs in 16 male patients with schizophrenia. Areas of correlation are overlaid on a study-specific template for accurate anatomical localisation. Co-ordinates in standardised neuroanatomical space [22] are shown in Table 1.