Psychopathic traits in Finnish homicide offenders with schizophrenia.

There is a paucity of studies examining psychopathy in comparable samples of violent individuals with and without psychotic illness. The main goal of the study was to assess the prevalence and nature of psychopathic traits as measured by PCL-R among Finnish homicide offenders with schizophrenia. Further, the impact of co-morbid psychopathy on the homicidal incidents, as well as the associations of psychopathy and offender background factors, among offenders with schizophrenia was investigated. A retrospective study was performed using extensive forensic psychiatric evaluation reports and crime reports as sources of information. The sample consisted of 72 homicide offenders with schizophrenia and 72 controls without psychotic illness. Psychopathic features were prevalent among Finnish homicide offenders with schizophrenia, although for the most parts to a lesser extent compared to other homicide offenders. Like non-mentally ill psychopathic offenders, offenders with schizophrenia and many psychopathic traits are likely to present early starting problems in many areas of life and they also commit homicides that resemble other psychopathic offenders' in their choice of victims, intoxication and post-offense behavior. The observed prevalence of psychopathic traits highlights the importance of psychopathy assessment among violence-prone individuals with schizophrenia. In most respects, offenders with schizophrenia and high levels of psychopathic traits seem to be similar to psychopathic offenders without psychotic illness, which has implications for early intervention and management.

Homicides with mutilation of the victim's body.

Information on homicide offenders guilty of mutilation is sparse. The current study estimates the rate of mutilation of the victim's body in Finnish homicides and compares sociodemographic characteristics, crime history, life course development, psychopathy, and psychopathology of these and other homicide offenders. Crime reports and forensic examination reports of all offenders subjected to forensic examination and convicted for a homicide in 1995-2004 (n = 676) were retrospectively analyzed for offense and offender variables and scored with the Psychopathy Check List Revised. Thirteen homicides (2.2%) involved mutilation. Educational and mental health problems in childhood, inpatient mental health contacts, self-destructiveness, and schizophrenia were significantly more frequent in offenders guilty of mutilation. Mutilation bore no significant association with psychopathy or substance abuse. The higher than usual prevalence of developmental difficulties and mental disorder of this subsample of offenders needs to be recognized.

Finnish sexual homicides: offence and offender characteristics.

Information on sexual homicide offenders is limited. The current study estimates the rate of sexual homicides in Finland and analyses sociodemographic characteristics, crime history, life course development, psychopathy, and psychopathology in sexual homicide and nonsexual homicide offenders. Crime reports and forensic examination reports of all offenders subjected to forensic examination and convicted for homicide in 1995-2004 (n=676) were retrospectively analyzed for offence and offender variables and scored with the Psychopathy Checklist-Revised. Eighteen sexual homicides (2.8%) were identified. Co-offending, strangulation and disposal of the body were more frequent crime scene variables in sexual than nonsexual homicides. Mental health problems and sexual abuse in childhood and sexual crime history were significantly more frequent in sexual than nonsexual homicide offenders. Over half of the sexual homicide offenders were psychopathic: compared to nonsexual homicide offenders they scored significantly higher on interpersonal and affective features of psychopathy.

Reproducibility of cortex-muscle coherence.

Cortex-muscle coherence is a frequency-analysis technique that has been increasingly applied in the investigation of movement disorders. To study the intra- and inter-session stability of the cortex-muscle coherence, we recorded from 12 healthy subjects magnetoencephalographic (MEG) and surface electromyographic (EMG) signals during unilateral isometric contractions of the left- and right-hand muscles. Two identical measurements were performed during one session, and the session was repeated once after about 1 year. In one experienced subject, the recordings were repeated seven times within 20 months. The MEG-EMG coherence exceeded the noise level in 10 out of 12 subjects. Both the frequency (correlation coefficient r = 0.77-0.93, P < 0.01) and strength (r = 0.78-0.91, P < 0.01) of coherence were well reproducible within each session for both left- and right-sided contractions. The inter-session reproducibility was high for the mean of cumulative coherence frequency (r = 0.90-0.95, P < 0.01), but relatively low for coherence strength (r = 0.43-0.59, P > 0.05). The results for one subject participating in 8 repeated sessions strongly supported the results of the whole group. Thus, intra-session reproducibility of both strength and frequency of the cortex-muscle coherence is good and studies comparing different conditions at the group level within one session are feasible. However, caution is needed when interpreting absolute levels or changes in the strength of coherence in single subjects between the sessions.

Short-term (approximately 600 ms) prediction of perturbation dynamics for 10- and 20-Hz MEG rhythms in human primary sensorimotor hand cortices.

The pericentral primary sensorimotor cortices generate the "mu rhythm" with a distinct spectral signature exhibiting two peaks, generated predominantly anterior (20 Hz) or posterior (10 Hz) to the central sulcus; it defines a "background" network state upon which somatosensory inputs will impinge. We used the high spatiotemporal resolution of magnetoencephalography to analyze the perturbation dynamics of these cortical rhythms in response to a series of paired electric median nerve stimuli: single trials were sorted off-line according to increasing power of the 10- or 20-Hz rebounds which occurred 300-600 ms after the first stimulus; using subaverages formed from the upper and lower 20% of this distribution, we analyzed somatosensory evoked fields (SEF) and power modifications caused by the second stimulus in the pair. We report three key findings: (1) the power level of rhythm rebounds triggered by the first stimulus predicted the rebound strength after the second stimulus applied 600 ms later; yet, it was uncorrelated across the 2.4-s interval separating subsequent stimulus pairs. (2) Conventional averaging camouflages substantial trial-to-trial variations of rhythm dynamics including, for example, even non-occurrences of rhythm rebounds. (3) For six of the seven subjects, the background rhythm power did not affect any SEF component; for the subject with the strongest rhythms only intracortically generated deflections (peaking after the thalamocortical input component N20m) varied as function of pre-stimulus 10- or 20-Hz power. Thus, the perturbation dynamics of the pericentral mu rhythm exhibits a significant intertrial variance, which becomes effective mainly at a time scale larger than 600 ms.

Synchronous cortical oscillatory activity during motor action.

Oscillations of the motor cortex interact with similar activity of the spinal motoneuron pool in the 15-30 Hertz frequency range. Recent observations have demonstrated how this interaction affects the firing of single corticospinal neurons. The interaction, reflected as corticomuscular coherence, occurs for both distal and proximal muscles and it constitutes one connection in a larger web of oscillatory interactions, including several other motor areas in the cortex, thalamus, and cerebellum. New results cast light on the possible functional significance of this interaction. The rhythmic interaction may reveal interesting information in several motor disorders, including essential tremor, Parkinson's disease, myoclonus epilepsy, and mirror movements.

Modulation of cortex-muscle oscillatory interaction by ischaemia-induced deafferentation.

We studied the effect of sensory feedback on the oscillatory interaction between activity of the motor cortex and the spinal motoneuron pool during isometric contraction. After inducing ischaemic sensory deafferentation in the upper limb in six subjects, we calculated coherences between simultaneously recorded whole-scalp magnetoencephalographic (MEG) signals and electromyographic (EMG) signals from the first dorsal interosseus muscles. We expected that the dominant frequency of coherence would change if there were interaction through a sensory feedback loop. However, the MEG-EMG coherence frequency did not change significantly during ischaemia. The strength of the coherence was reduced during ischaemia, but returned to the pre-ischaemic level after ischaemia had ended. Reduction of sensory feedback may thus indirectly reduce the amount of corticomuscular coherence, but the lack of change in the dominant coherent frequency suggests that a sensory feedback loop is not essential for the generation of this coherence.

Cortico-muscular coupling in a human subject with mirror movements--a magnetoencephalographic study.

We studied cortico-muscular coupling in a 15-year-old male suffering from congenital mirror movements (MMs) of hands. Cortex-muscle coherence was analyzed between magnetoencephalographic signals and the electromyograms (EMGs) recorded from both hands and feet during uni- and bilateral isometric contractions. Regardless of the side of the intended contraction, the motor cortex contralateral to the contraction was coupled to the muscles of both hands at 20-25 Hz. No coupling was found from the other, ipsilateral hemisphere. EMGs of the two hands were coupled during both intended uni- and bilateral contractions, but only during unilateral contractions could the coupling solely be explained by cortical activation. We suggest that our subject's MMs result from activation of an ipsilateral corticospinal projection, with involvement of additional synchronizing mechanisms at the subcortical, brainstem, or spinal level during bilateral contraction.

Defective cortical drive to muscle in Parkinson's disease and its improvement with levodopa.

We recorded whole-scalp magnetoencephalographic (MEG) signals simultaneously with surface electromyographic (EMG) activity from eight patients with Parkinson's disease after withdrawal and reinstatement of treatment with levodopa. Variations were seen in the coherence between the forearm extensor EMG and the MEG signal originating near or in the hand region of the primary motor cortex. As a group, the parkinsonian patients withdrawn from levodopa showed a reduction in the coherence at 15-30 Hz and 35-60 Hz, and a further three untreated patients had abnormally strong MEG-EMG coherence at 5-12 Hz compared with when medicated or with eight healthy age-matched control subjects. We conclude that the basal ganglia have a specific effect on the temporal organization of motor cortical activity during voluntary tonic contraction. Abnormalities in this aspect of basal ganglia function may directly contribute to bradykinesia and weakness in Parkinson's disease.