Methylphenidate reduces orienting bias in healthy individuals.

BACKGROUND: Healthy individuals show subtle orienting bias, a phenomenon known as pseudoneglect, reflected in a tendency to direct greater attention toward one hemispace. Accumulating evidence indicates that this bias is an individual trait, and attention is preferentially directed contralaterally to the hemisphere with higher dopamine signaling. Administration of methylphenidate (MPH), a dopamine transporter inhibitor, was shown to normalize aberrant spatial attention bias in psychiatric and neurological patients, suggesting that the reduced orienting bias following administration of MPH reflects an asymmetric effect of the drug, increasing extracellular dopamine in the hemisphere with lower dopamine signaling. AIM: We predicted that, similarly to its effect on patients with brain pathology, MPH will reduce the orienting bias in healthy subjects. METHODS: To test this hypothesis, we examined the behavioral effects of a single dose (20 mg) of MPH on orienting bias in 36 healthy subjects (18 females) in a randomized, double-blind placebo-controlled, within-subject design, using the greyscales task, which has been shown to detect subtle attentional biases in both patients and healthy individuals. RESULTS/OUTCOMES: Results demonstrate that healthy individuals vary in both direction and magnitude of spatial orienting bias and show reduced magnitude of orienting bias following MPH administration, regardless of the initial direction of asymmetry. CONCLUSIONS/INTERPRETATIONS: Our findings reveal, for the first time in healthy subjects, that MPH decreases spatial orienting bias in an asymmetric manner. Given the well-documented association between orienting bias and asymmetric dopamine signaling, these findings also suggest that MPH might exert a possible asymmetric neural effect in the healthy brain.

Patterns of psychiatric hospitalizations among migrant workers and asylum-seekers in Israel: a single hospital archive study, 2005-2011.

Aim: Migrants have increased risk for psychiatric hospitalizations. Over the last decades Israel has become a destination for migration of migrant workers and asylum-seekers.Methods: The current retrospective study retrieved socio-demographic, clinical and migration-related chart data for 117 migrants admitted to a major Israeli psychiatric hospital between 2005-2011, to delineate characteristics and risk-factors for psychiatric hospitalizations. Multivariate logistic regression analyses were performed to predict re-hospitalization.Results: Of the study sample, 61% were single men, 20% had been exposed to trauma, 15% had prior psychiatric hospitalizations and 24% had attempted suicide. Approximately, 76% were involuntarily hospitalized and diagnosed with psychosis. None were diagnosed with PTSD. Approximately, 20% were re-hospitalized. Factors significantly associated with re-hospitalization were male gender (OR = 15.2, 95%, CI 1.8-126.9, p = 0.012), prior psychiatric hospitalization (OR = 15.4, 95% CI 2.1-111.9, p < 0.01), being single (OR = 5.96, 95% CI1.14-31.07, p = 0.03) and traumatic exposure (OR = 4.75, 95% CI: 1.17-19.36, p= 0.03). Shorter duration in Israel, unemployment, asylum-seekers, no temporary-visa and use of restraints were more prevalent among those re-hospitalized.Conclusion: Identification of migrants at risk and trauma-informed, culturally relevant services can reduce hospitalizations.

Novelty-seeking trait predicts the effect of methylphenidate on creativity.

In recent years the use of psychostimulants for cognitive enhancement in healthy individuals with no psychiatric disorders has been on the rise. However, it is still unclear whether psychostimulants improve certain cognitive functions at the cost of others, and how these psychostimulants interact with individual personality differences. In the current study, we investigated whether the effect of one common stimulant, methylphenidate (MPH), on creativity is associated with novelty seeking. Thirty-six healthy adults, without attention-deficit hyperactivity disorder (ADHD) symptomology, were assigned randomly in a double-blind fashion to receive MPH or placebo. We found that the effect of MPH on creativity was dependent on novelty-seeking (NS) personality characteristics of the participants. MPH increased creativity in individuals with lower NS, while it reduced creativity levels in individuals with high NS. These findings highlight the role of the dopaminergic system in creativity, and indicate that among healthy individuals NS can be seen as a predictor of the effect of MPH on creativity.

A possible effect of methylphenidate on state anxiety: A single dose, placebo controlled, crossover study in a control group.

Methylphenidate affects state-anxiety in ADHD patients. The current study examines the effect of Methylphenidate on state-anxiety in healthy subjects. In a cross-over, randomized, controlled, double-blind study, 36 healthy subjects received either Methylphenidate or placebo. As a group, no change in state-anxiety was detected with Methylphenidate. However, participants reporting higher anxiety levels experienced a significant and specific state-anxiety reduction following Methylphenidate. Moreover, a strong negative correlation was found between the initial-level of anxiety and net-change in state-anxiety. These changes were unrelated to self-perceived attention levels. Our results point to the state-dependent effects of Methylphenidate on anxiety.

Enhancement of latent inhibition in patients with chronic schizophrenia.

OBJECTIVES: Latent inhibition (LI) refers to the retarding effects of inconsequential stimulus preexposure on subsequent conditioning to that stimulus, and reflects the organism's capacity to ignore irrelevant stimuli. LI is disrupted in schizophrenia patients, due to faster learning of the association between the conditioned stimulus (CS) and an unconditioned stimulus (US). It was recently proposed that LI has an additional pole of abnormality indicated by LI persistence. METHODS: Two experiments were performed to test this hypothesis. Both experiments applied a new within-subject, visual recognition LI procedure in which the association between a cue (CS) and the target (US) is acquired. In Exp 1 the task was applied to healthy volunteers (n=21). In Exp 2 chronic schizophrenia patients (n=19) were compared to control subjects (n=20). RESULTS: In Exp 1 the subjects showed LI in the initial trials of cue-target pairings, and an attenuation of the phenomenon at later trials. In Exp 2 control subjects showed a pattern of response comparable to the subjects of Exp 1, while the patients showed LI only on the later trials of the task. CONCLUSIONS: This result suggests that patients with chronic schizophrenia showed LI persistence. The possible advantages of the new LI paradigm are discussed.