Quantifying over-activity in bipolar and schizophrenia patients in a human open field paradigm

It has been suggested that a cardinal symptom of mania is over-activity and exaggerated goal-directed behavior. Nevertheless, few attempts have been made to quantify this behavior objectively in a laboratory environment. Having a methodology to assess over-activity reliably might be useful in distinguishing manic bipolar disorder (BD) from schizophrenia (SCZ) during highly activated states. In the current study, quantifiable measures of object interaction were assessed using a multivariate approach. Additionally, symptom correlates of over-activity were assessed. Patients admitted to an acute care psychiatric hospital for either BD with mania or SCZ (paranoid and non-paranoid subtypes) as well as non-patient comparison (NC) participants were assessed in an open field setting referred to as the human Behavioral Pattern Monitor (hBPM). Activity and interactions with novel and engaging objects were recorded for 15 min via a concealed video camera and rated for exploratory behavior. Both BD and SCZ patients spent more time near the objects and exhibited more overall walking compared to NC. In contrast, BD patients exhibited greater physical contact with objects (number of object interactions and time spent with objects) relative to SCZ patients or NC participants, as well as more perseverative and socially disinhibited behaviors, indicating a unique pattern of over-activity and goal-directed behavior. Further analyses revealed a distinction between SCZ patients according to their subtype. The current study extends our methodology for quantifying exploration and over-activity in a controlled laboratory setting and aids in assessing the overlap and distinguishing characteristics of BD and SCZ.