Responsiveness of sensorimotor cortex during pharmacological intervention with bromazepam.

The aim of this study was to investigate the influence of bromazepam on EEG and the motor learning process when healthy subjects were submitted to a typewriting task. We investigated bromazepam due to its abuse by various populations and its prevalent clinical use among older individuals which are more sensitive to the negative effects of long half-life benzodiazepines. A randomized double-blind design was used with subjects divided into three groups: placebo (n=13), bromazepam 3mg (n=13) and bromazepam 6 mg (n=13). EEG data comprising theta, alpha and beta bands was recorded before, during and after the motor task. Our results showed a lower relative power value in the theta band in the Br 6 mg group when compared with PL. We also observed a reduction in relative power in the beta band in the Br 3mg and Br 6 mg when compared with PL group. These findings suggest that Br can contribute to a reduced working memory load in areas related to attention processes. On the other hand, it produces a higher cortical activation in areas associated with sensory integration. Such areas are responsible for accomplishing the motor learning task. The results are an example of the usefulness of integrating electrophysiological data, sensorimotor activity and a pharmacological approach to aid in our understanding of cerebral changes produced by external agents.

Effects of lorazepam on deductive reasoning.

RATIONALE: Benzodiazepines slow reasoning performance, but it is still unknown which phase of reasoning is affected and whether this effect is present for different types of relations between entities in reasoning problems. OBJECTIVES: We investigated which phases of deductive reasoning are affected by lorazepam and whether this effect varies according to the type of relations in deductive reasoning problems. METHODS: This was a double-blind, crossover design study of acute oral doses of lorazepam (2 mg) and placebo, using young healthy volunteers. We focused on response delay of three separable phases of deductive reasoning and matched working memory tasks (that involved only maintenance of information) the premise processing phase, the premise integration phase, and the validation phase, in which reasoners decide whether a conclusion logically follows from the premises (reasoning task) or is identical to one of the premises (maintenance task). Type of relations in the premises was also manipulated. We employed material that was difficult to envisage visually and visuospatially ("subiconic") and material easy to envisage visually or visuospatially. RESULTS: Lorazepam slowed response as memory load increased, irrespective of type of relations. It also specifically slowed validation in reasoning problems with visual relations, an effect that disappeared after subtraction of maintenance scores, and increased validation time in problems with subiconic relations, which remained after this subtraction. CONCLUSION: Acute lorazepam administration affected reasoning in two ways: it slowed processing nonspecifically when working memory demands increased and augmented validation time depending on the difficulty in generating and/or manipulating mental representations by the central executive.

Neurobehavioral development in children with potential exposure to pesticides.

BACKGROUND: Children may be at higher risk than adults from pesticide exposure, due to their rapidly developing physiology, unique behavioral patterns, and interactions with the physical environment. This preliminary study conducted in Ecuador examines the association between household and environmental risk factors for pesticide exposure and neurobehavioral development. METHODS: We collected data over 6 months in the rural highland region of Cayambe, Ecuador (2003-2004). Children age 24-61 months residing in 3 communities were assessed with the Ages and Stages Questionnaire and the Visual Motor Integration Test. We gathered information on maternal health and work characteristics, the home and community environment, and child characteristics. Growth measurements and a hemoglobin finger-prick blood test were obtained. Multiple linear regression analyses were conducted. RESULTS: Current maternal employment in the flower industry was associated with better developmental scores. Longer hours playing outdoors were associated with lower gross and fine motor and problem solving skills. Children who played with irrigation water scored lower on fine motor skills (8% decrease; 95% confidence interval = -9.31 to -0.53), problem-solving skills (7% decrease; -8.40 to -0.39), and Visual Motor Integration test scores (3% decrease; -12.00 to 1.08). CONCLUSIONS: These results suggest that certain environmental risk factors for exposure to pesticides may affect child development, with contact with irrigation water of particular concern. However, the relationships between these risk factors and social characteristics are complex, as corporate agriculture may increase risk through pesticide exposure and environmental contamination, while indirectly promoting healthy development by providing health care, relatively higher salaries, and daycare options.

Prefrontal cognitive dysfunction following brainstem lesion.

Prefrontal cortex (PFC) dysfunction can lead to impairment in planning and behavioral inhibition, as well as personality changes. As ascending monoaminergic brainstem systems modulate PFC functioning, it is possible that lesions in the brainstem lead to symptoms similar to prefrontal dysfunction. A 29-year-old man developed several cognitive and behavioral symptoms after neurosurgery for resection of a pilocytic astrocytoma in the pontine-mesencephalic area. A careful analysis of symptoms indicated PFC dysfunction that could be attributed to lesions in the ascending monoaminergic brainstem systems. Interestingly, the cognitive symptoms improved after treatment with methylphenidate, which is a drug that modules catecholaminergic neurotransmission, thereby supporting this hypothesis. This is a unique case of PFC dysfunction that may be related to post-operative lesion of the catecholaminergic nuclei in the brainstem.

Neurotoxic lesion of anteromedial/posterior parietal cortex disrupts spatial maze memory in blind rats.

The primary visual cortex of rats is surrounded laterally (in Oc2L) and medially (in Oc2M) by several peristriate visual areas. Previous studies from our laboratory demonstrated that bilateral lesions in Oc2L result in visual pattern discrimination deficit, and in failure to solve a conditional discrimination which requires figure-background association. In contrast, neurotoxic lesions of the rostral part of Oc2M (which contains the anteromedial and anterior peristriate visual areas, collectively referred to as AM complex) result in deficits in visuospatial discrimination, and in disruptions in visual tasks involving spatial memory. The objective of this study was to behaviorally test the role of AM complex in a spatial memory task in absence of visual cues. For this purpose, we analyzed memory retention of Lashley III maze in blind rats after bilateral ibotenate lesions in AM complex, or in the primary visual cortex (V1, Oc1), to test the hypothesis that AM complex is essential for this cognitive task. The results showed a significant loss of memory retention of the maze in rats with lesions in AM complex, but not in rats with lesions in V1. Furthermore, the retention loss in rats with AM complex lesions was positively and significantly correlated with the size of the lesion. The results indicate a critical role of AM complex in spatial memory mechanisms independent on visual cues. A probable homology of rat AM complex with the posterior parietal cortex of primates is discussed.

Methylphenidate and attributions in boys with attention-deficit hyperactivity disorder.

In Experiment 1, 28 attention-deficit hyperactivity disorder (ADHD) boys underwent a double-blind, placebo-controlled medication assessment in a summer day-treatment program. Daily, boys were asked questions to assess their attributions for and evaluations of their behavior. Objective measures showed improved behavior with methylphenidate; however, boys tended to attribute their performance to effort rather than to medication, particularly when medicated. Experiment 2 involved 38 ADHD boys the following summer and replicated the procedures in Experiment 1, with the addition of a no-pill condition and a comparison of attributions for success and failure outcomes. Simply taking a pill (no-pill vs. placebo comparison) did not show significant effects, whereas the results of Experiment 1 were replicated with placebo-methylphenidate comparisons. Across drug conditions a self-enhancing attributional pattern was obtained; the majority of attributions for success were to ability or effort, whereas attributions for failure were to the pill or to counselors.