Inhibitory deficits in Klinefelter syndrome are secondary to deficits in the auditory and motor domain

Deficits in several cognitive domains are prevalent in men with Klinefelter Syndrome (KS). Verbal deficits are among the most characteristic cognitive impairments of KS, yet other cognitive domains also exhibit deficits. Executive functions, especially working memory capacity and inhibitory control, are frequently affected as well. A common limitation of previous studies addressing potential deficits in inhibitory control is their potential conflation with language-related capabilities, as for example is the case with the Stroop task. Importantly, none of the prior studies utilized the best-accepted approach to study inhibition, namely the Stop Signal Task (SST). This study therefore tested for deficits in inhibitory control in individuals with KS and controls (HC) using a version of the SST with non-semantic auditory stimuli. In addition to the classic behavioral performance measures (e.g., the go reaction time, stopping accuracy, or stop signal reaction time), we also derived parameters of inhibition and attention from electromyography (EMG), electroencephalography (EEG), and Bayesian modeling. Men with KS exhibited prolonged stopping latencies (i.e., stop signal reaction times) and reduced stopping accuracies. Yet, whereas these model-based indices were indicative of attenuated inhibitory control, neither event-related brain potentials nor an EMG-measure of the stopping latency confirmed such deficits. Behavioral and EEG indices, however, provided evidence for deficits in motor response preparation and generation, as well as the early processing of auditory stimuli. In sum, the overall pattern of results does not support the existence of inhibitory deficits in KS per se, but rather suggests that behavioral indices of impaired inhibition may result from early low-level deficits in the auditory and motor domains, as well as a differential weighting in the processing of different aspects of the task.