Trait impulsivity and increased pre-attentional sensitivity to intense stimuli in bipolar disorder and controls

Motor dysfunction as research domain across bipolar, obsessive-compulsive and neurodevelopmental disorders

Although genuine motor abnormalities (GMA) are frequently found in schizophrenia, they are also considered as an intrinsic feature of bipolar, obsessive-compulsive, and neurodevelopmental disorders with early onset such as autism, ADHD, and Tourette syndrome. Such transnosological observations strongly suggest a common neural pathophysiology. This systematic review highlights the evidence on GMA and their neuroanatomical substrates in bipolar, obsessive-compulsive, and neurodevelopmental disorders. The data lends support for a common pattern contributing to GMA expression in these diseases that seems to be related to cerebello-thalamo-cortical, fronto-parietal, and cortico-subcortical motor circuit dysfunction. The identified studies provide first evidence for a motor network dysfunction as a correlate of early neurodevelopmental deviance prior to clinical symptom expression. There are also first hints for a developmental risk factor model of these mental disorders. An in-depth analysis of motor networks and related patho-(physiological) mechanisms will not only help promoting Research Domain Criteria (RDoC) Motor System construct, but also facilitate the development of novel psychopharmacological models, as well as the identification of neurobiologically plausible target sites for non-invasive brain stimulation.

Heightened early-attentional stimulus orienting and impulsive action in men with antisocial personality disorder

We tested whether enhanced stimulus orienting operationalized as N1 and P2 auditory evoked potentials to increasing loudness (50-90 dB clicks) could be associated with trait impulsivity (Barratt Impulsiveness Scale, BIS-11), impulsive action (commission error on the Immediate Memory Task), or impulsive choice (immediate responses on temporal discounting tasks). We measured N1 and P2 loudness sensitivity in a passive listening task as linear intensity-sensitivity slopes in 36 men with antisocial personality disorder with a history of conviction for criminal conduct and 16 healthy control men. Across all subjects, regression analyses revealed that a steeper P2 slope predicted higher IMT commission error/correct detection ratio, and lower stimulus discriminability (A-prime). These associations were also found within both groups. These relationships suggest an association between enhanced early stimulus orienting (P2), impulsive action (response inhibition), and impaired signal-noise discriminability (A-prime).

Clinical features, impulsivity, temperament and functioning and their role in suicidality in patients with bipolar disorder

OBJECTIVE

Our aim was to analyse sociodemographic and clinical differences between non-suicidal (NS) bipolar patients (BP), BP reporting only suicidal ideation (SI) and BP suicide attempters according to Columbia-Suicide Severity Rating Scale (C-SRSS) criteria. Secondarily, we also investigated whether the C-SRSS Intensity Scale was associated with emergence of suicidal behaviour (SB).

METHOD

A total of 215 euthymic bipolar out-patients were recruited. Semistructured interviews including the C-SRSS were used to assess sociodemographic and clinical data. Patients were grouped according to C-SRSS criteria: patients who scored ≤1 on the Severity Scale were classified as NS. The remaining patients were grouped into two groups: 'patients with history of SI' and 'patients with history of SI and SB' according to whether they did or did not have a past actual suicide attempt respectively.

RESULTS

Patients from the three groups differed in illness onset, diagnosis, number of episodes and admissions, family history, comorbidities, rapid cycling and medication, as well as level of education, functioning, impulsivity and temperamental profile.

CONCLUSION

Our results suggest that increased impulsivity, higher rates of psychiatric admissions and a reported poor controllability of SI significantly increased the risk for suicidal acts among patients presenting SI.

The Effect of Stimulus Intensity and Carrier Frequency on Auditory Middle- and Long-Latency Evoked Potentials Using a Steady-State-Response Approach

PURPOSE

The purpose of this study was to measure magnitude changes of auditory steady-state responses (ASSRs) and respective transient middle- and long-latency responses as a function of stimulus intensity and carrier frequency. The literature lacks clear consensus, including relationship to loudness.

METHOD

A cohort of 48 adults with normal hearing was examined from a companion study (Tlumak, Durrant, & Delgado, 2015) on effects of aging. ASSRs were elicited by repeated tone-burst stimuli presented at rates of 40 and 0.75 Hz at 3 frequencies and 5 levels of stimulus intensity. The design also permitted scrutiny of any gender bias to the results.

RESULTS

Similar to derived transient response findings, ASSR magnitude (harmonic sum) systematically increased with intensity. Input-output function only at 0.75 Hz approximated a log-log linear function. However, slopes fell well below that of doubling of loudness per 10 dB SPL. Results failed to demonstrate significance as a function of carrier frequency and gender for both repetition rates.

CONCLUSION

Effects of stimulus intensity, carrier frequency, and gender on ASSRs were similar to those of their transient counterparts. Findings remain disappointing for objective loudness estimation. Results suggest only a clear linkage to the long-latency response and the 0.75-Hz magnitude but require careful consideration of limitations/underlying mechanisms when measuring loudness-related effects.