Seasonality of suicide behavior in Northwest Alaska: 1990-2009.

OBJECTIVES: Suicide is a leading cause of death worldwide, and disproportionately affects Indigenous populations. Seasonal suicide patterns are variable in the literature, and could offer novel approaches to the timing and focus of prevention efforts if better understood. With a suicide surveillance system in place since 1989, this study offers an unprecedented opportunity to explore seasonal variations in both fatal and non-fatal suicide behavior in an Indigenous Arctic region. STUDY DESIGN: Cross-sectional. METHODS: In this descriptive study, we analyzed data collected from 1990 to 2009 in the rural northwest region of Alaska, both graphically and using the chi-squared test for multinomials. RESULTS: We found a significant monthly variation for suicide attempts, with a peak in suicide behavior observed between April and August (P = 0.0002). Monthly variation was more pronounced among individuals ≤29 years of age, and was present in both males and females, although the seasonal pattern differed by sex. CONCLUSIONS: Our findings of a significant seasonal pattern in suicide behavior, with monthly variation (summer peak) in non-fatal suicide behavior among younger age groups, and among both males and females can assist planners in targeting subpopulations for prevention at different times of the year.

Apolipoprotein E-e4, processing speed, and white matter volume in a genetically enriched sample of midlife adults.

Healthy midlife children of a parent with Alzheimer's disease ([AD] N = 23; 9 male) participated in neuropsychological testing, and magnetic resonance imaging (MRI) of brain volumetrics were obtained. In all, 35% of the sample were apolipoprotein E (ApoE)-e4 positive (n = 8; 5 male). The ApoE-e4 group exhibited significantly slower performances on an executive function and processing speed measure and had less white matter volume than the non-ApoE-e4 group. Lesser white matter volume was significantly correlated with slower processing speed. Processing speed and changes in white matter volume might be indicators of preclinical decline in AD.

Evidence of a novel somatopic map in the human neocerebellum during complex actions.

The human neocerebellum has been hypothesized to contribute to many high-level cognitive processes including attention, language, and working memory. Support for these nonmotor hypotheses comes from evidence demonstrating structural and functional connectivity between the lateral cerebellum and cortical association areas as well as a lack of somatotopy in lobules VI and VII, a hallmark of motor representations in other areas of the cerebellum and cerebral cortex. We set out to test whether somatotopy exists in these lobules by using functional magnetic resonance imaging to measure cerebellar activity while participants produced simple or complex movements, using either fingers or toes. We observed a previously undiscovered somatotopic organization in neocerebellar lobules VI and VIIA that was most prominent when participants executed complex movements. In contrast, activation in the anterior lobe showed a similar somatotopic organization for both simple and complex movements. While the anterior somatotopic representation responded selectively during ipsilateral movements, the new cerebellar map responded during both ipsi- and contralateral movements. The presence of a bilateral, task-dependent somatotopic map in the neocerebellum emphasizes an important role for this region in the control of skilled actions.

Timing of rhythmic movements in patients with cerebellar degeneration.

A distinction in temporal performance has been identified between two classes of rhythmic movements: those requiring explicit timing of salient events marking successive cycles, i.e., event timing, and continuous movements in which timing is hypothesized to be emergent. Converging evidence in support of this distinction is reviewed, including neuropsychological studies showing that individuals with cerebellar damage are selectively impaired on tasks requiring event timing (e.g., tapping). Recent behavioral evidence in neurologically healthy individuals suggests that for continuous movements (e.g., circle drawing), the initial cycle is marked by a transformation from event to emergent timing, allowing the participant to match their movement rate to an externally defined cycle duration. We report a new experiment in which individuals with cerebellar ataxia produced rhythmic tapping or circle drawing movements. Participants were either paced by a metronome or unpaced. Ataxics showed a disproportionate increase in temporal variability during tapping compared to circle drawing, although they were more variable than controls on both tasks. However, two predictions of the transformation hypothesis were not confirmed. First, the ataxics did not show a selective impairment on circle drawing during the initial cycles, a phase when we hypothesized event timing would be required to establish the movement rate. Second, the metronome did not increase variability of the performance of the ataxics. Taken together, these results provide further evidence that the integrity of the cerebellum is especially important for event timing, although our attempt to specify the relationship between event and emergent timing was not successful.

Computer simulations of lung airway structures using data-driven surface modeling techniques.

Knowledge of human lung morphology is a subject critical to many areas of medicine. The visualization of lung structures naturally lends itself to computer graphics modeling due to the large number of airways involved and the complexities of the branching systems. In this study, a method of generating three-dimensional computer simulations of human lung airway networks using data-driven, surface modeling techniques is presented. By simulating the tubular airway structures and realistic bifurcation shapes, anatomically accurate representations of human lungs are obtained. These computer models are designed for use in computational fluid dynamic applications and particle trajectory analyses, and to be complimentary to medical imaging (gamma scintigraphy) protocols.

Temporal precision in tapping and circle drawing movements at preferred rates is not correlated: further evidence against timing as a general-purpose ability.

Recently, researchers have discovered that individuals who are consistent timers in a tapping task are not necessarily consistent timers when they perform a continuous drawing task. In other words, nonsignificant correlations were found among tapping and drawing movements for timing precision (S. D. Robertson et al., 1999). In the present experiment, the authors investigated whether or not consistency in timing for tapping and drawing was correlated when participants (N = 24) were allowed to move at their preferred rate of movement. There were no significant correlations between tapping and drawing in terms of timing precision. That result lends further support to the notion that timing behavior is specific to the nature of the task, and thus further weakens the idea that timing is a generalized ability that can be imposed on a variety of different types of tasks.

Lung models: strengths and limitations.

The most widely used particle dosimetry models are those proposed by the National Council on Radiation Protection, International Commission for Radiological Protection, and the Netherlands National Institute of Public Health and the Environment (the RIVM model). Those models have inherent problems that may be regarded as serious drawbacks: for example, they are not physiologically realistic. They ignore the presence and commensurate effects of naturally occurring structural elements of lungs (eg, cartilaginous rings, carinal ridges), which have been demonstrated to affect the motion of inhaled air. Most importantly, the surface structures have been shown to influence the trajectories of inhaled particles transported by air streams. Thus, the model presented herein by Martonen et al may be perhaps the most appropriate for human lung dosimetry. In its present form, the model's major "strengths" are that it could be used for diverse purposes in medical research and practice, including: to target the delivery of drugs for diseases of the respiratory tract (eg, cystic fibrosis, asthma, bronchogenic carcinoma); to selectively deposit drugs for systemic distribution (eg, insulin); to design clinical studies; to interpret scintigraphy data from human subject exposures; to determine laboratory conditions for animal testing (ie, extrapolation modeling); and to aid in aerosolized drug delivery to children (pediatric medicine). Based on our research, we have found very good agreement between the predictions of our model and the experimental data of Heyder et al, and therefore advocate its use in the clinical arena. In closing, we would note that for the simulations reported herein the data entered into our computer program were the actual conditions of the Heyder et al experiments. However, the deposition model is more versatile and can simulate many aerosol therapy scenarios. For example, the core model has many computer subroutines that can be enlisted to simulate the effects of aerosol polydispersity, aerosol hygroscopicity, patient ventilation, patient lung morphology, patient age, and patient airway disease.

Correlations for timing consistency among tapping and drawing tasks: evidence against a single timing process for motor control.

Three experiments were conducted to examine whether timing processes can be shared by continuous tapping and drawing tasks. In all 3 experiments, temporal precision in tapping was not related to temporal precision in continuous drawing. There were modest correlations among the tapping tasks, and there were significant correlations among the drawing tasks. In Experiment 3, the function relating timing variance to the square of the observed movement duration for tapping was different from that for drawing. The conclusions drawn were that timing is not an ability to be shared by a variety of tasks but instead that the temporal qualities of skilled movement are the result of the specific processes necessary to produce a trajectory. These results are consistent with the idea that timing is an emergent property of movement.

Metals and school learning: a review of investigative techniques.

A growing body of literature suggests a relationship between metals and a threatened health status among children, adolescents, and adults. Recently, several investigators have reported a direct link between exposure to metal and diminished affective, behavioral, and cognitive performance of school children. The purpose of the present study was to review and analyze methods and procedures used to understand the relationship between exposure to metals and cognitive, social, and motor functioning of school children.

Morphine-induced behavioral disruption in rats chronically depleted of brain dopamine.

The ability of rats, chronically depleted of brain dopamine (DA), to develop tolerance to morphine (120 mg/kg, s.c.) given twice daily was studied using a food-reinforced operant procedure (FR-10). DA was depleted via the administration of 6-OHDA (150 ug, ict.) and desmethylimipramine (DMI; 25 mg/kg, ip.) to rats 14 days of age. This procedure resulted in a 61% depletion of brain DA when these rats were 120 days of age, while norepinephrine levels were not significantly affected. The response rates of DA-depleted and vehicle (ict.) + DMI treated controls were equally suppressed by various acute doses of morphine, but the DA-depleted group appeared to develop tolerance to the higher morphine dosage regimen (120 mg/kg, b.i.d) faster than the control group. In addition, DA-depleted rats exhibited a greater suppression of response rates 24 hr after the cessation of morphine treatment.

A comparison of nicotine and structurally related compounds as discriminative stimuli.

1 Of seven nicotine-like compounds tested as discriminative stimuli in the rat, only 3-pyridyl-methylpyrollidine (3-PMP) generalized to the stimulus effects of nicotine. 2 3-PMP caused equivalent nicotine-like responding at a dose (800 microgram/kg) approximately 4 times that used for the original nicotine discrimination (200 microgram/kg). The ED50 for 3-PMP was about 5 times that for nicotine. 3 Testing of the compounds as possible antagonists of the nicotine-elicited cue were negative. 4 The nicotine-like cue produced by an 800 microgram/kg injection of 3-PMP was effectively blocked by mecamylamine but not by hexamethonium or atropine. Thus, 3-PMP appears to produce generalization to the nicotine cue via action on central nicotinic-cholinoceptors as has been previously reported for the nicotine discriminative stimulus. 5 Mecamylamine blocked the stimulus-effects of 3-PMP (800 microgram/kg) and of nicotine (200 microgram/kg) with an ED50 of 0.32 and 0.20 microgram/kg respectively.

The discriminative stimulus properties of cyclazocine: generalization studies involving nalorphine, morphine and LSD.

Rats learned to discriminate cyclazocine (2 mg/kg, i.p.) from saline using a two-lever operant (FR-4) procedure within 10 sessions under each drug condition. The cyclazocine discriminative stimulus (DS) was both dose- and time-related, being antagonized by naloxone at doses approximately 80 times that necessary to block the discriminative stimulus effect of morphine. Cyclazocine also generalized to nalorphine, but not to morphine, pentazocine or LSD. These data suggest that cyclazocine produced DS control of behavior by acting at CNS sites different from those affected by morphine or LSD.

The discriminative stimulus properties of morphine in female rats chronically depleted of dopamine.

Female rats, 14 days of age, were chronically depleted of brain dopamine (DA) by the intracisternal administration of 6-OHDA 30 minutes following (i.p.) administration of desmethylimipramine (DMI). Dopamine depleted (DA) rats and their respective controls were trained to discriminate morphine from saline in a double bar discrimination task. While dopamine depletion did not hinder learning of the task, it markedly reduced morphine's suppressive effects as measured by response rates. Indications of stimulus generalization to methadone and haloperidol were observed in both groups via dose response tests. In addition, chronic morphine injections appeared to cause a repletion of DA in the DA group. Acute morphine-doses or chronic saline treated DA rats exhibited a 64-85% depletion of DA, while DA rats administered morphine chronically displayed a lesser depletion (42-46%).