Timing dysfunctions in schizophrenia as measured by a repetitive finger tapping task

Abstract

Schizophrenia may be associated with a fundamental disturbance in the temporal coordination of information processing in the brain, leading to classic symptoms of schizophrenia such as thought disorder and disorganized and contextually inappropriate behavior. Although a variety of behavioral studies have provided strong evidence for perceptual timing deficits in schizophrenia, no study to date has directly examined overt temporal performance in schizophrenia using a task that differentially engages perceptual and motor-based timing processes. The present study aimed to isolate perceptual and motor-based temporal performance in individuals diagnosed with schizophrenia using a repetitive finger-tapping task that has previously been shown to differentially engage brain regions associated with perceptual and motor-related timing behavior. Thirty-two individuals with schizophrenia and 31 non-psychiatric control participants completed the repetitive finger-tapping task, which required participants to first tap in time with computer-generated tones separated by a fixed intertone interval (tone-paced tapping), after which the tones were discontinued and participants were required to continue tapping at the established pace (self-paced tapping). Participants with schizophrenia displayed significantly faster tapping rates for both tone- and self-paced portions of the task compared to the non-psychiatric group. Individuals diagnosed with schizophrenia also displayed greater tapping variability during both tone- and self-paced portions of the task. The application of a mathematical timing model further indicated that group differences were primarily attributable to increased timing--as opposed to task implementation--difficulties in the schizophrenia group, which is noteworthy given the broad range of impairments typically associated with the disorder. These findings support the contention that schizophrenia is associated with a broad range of timing difficulties, including those associated with time perception as well as time production.

Figure 1

Graphical depiction of the Wing-Kristofferson model (adapted from Wing & Kristofferson, 1973a, 1973b). p denotes a clock pulse, and c(1) is the clock interval between p(0) and p(1). r denotes a response, and m(0) and m(1) are motor delays between clock pulses and behavioral responses. ITI(1) represents the inter-tap interval between r(0) and r(1).

Figure 2

Mean (MN), standard deviation (SD), and coefficient of variation (CV) indices of tone-and self-paced tapping for the schizophrenia (SZ) and control groups. (A): For both tone- and self-paced tapping, individuals with schizophrenia produced significantly shorter mean ITIs than control participants under both dominant index and alternating thumb conditions. (B) and (C): For both tone- and self-paced tapping, individuals with schizophrenia showed greater tapping variability (as measured by SD and CV indices) than control participants. All participants demonstrated significantly greater tapping variability during the alternating thumbs compared to the dominant index finger condition.

Figure 3

Mean sequence of inter-tap intervals (ITIs) across a sequence of 30 self-paced taps in the dominant index (top) and alternating thumb (bottom) conditions using a standard interstimulus interval equal to 500 ms. SZ = schizophrenia group.