Diazepam impairs temporal dynamics of visual attention

Stability of diazepam's phase II metabolites in dried blood spots on filter paper

Phase II metabolites play an important role in diazepam-related cases. The study aimed to assess the stability of diazepam's phase II metabolites in dried blood spots on filter paper.

METHODS

A piece of filter paper was spotted with 100 µL of whole blood (added 1% sodium fluoride as needed) obtained from participant who received 5 mg diazepam orally, air dried for 2 h at room temperature, and then stored at different conditions. Whole spots were cut at 0.1 cm from the outer edge of blood spots at post-consumption time-points of prior (zero), 5, 16, 35, 61, 120 days and 1, 1.5 years. Analytes were extracted with methanol/water mixture (8:2, v/v) and determined using HPLC-MS/MS. Decomposition rules were analyzed by a statistical software "SPSS".

RESULTS

Temazepam glucuronide remained stable (0.5-18.6% loss) at 20 ℃ and at 20 ℃ with 1% sodium fluoride for 16 days, while it was unstable after 5 days at 4 ℃ (21.1-26.2% loss) and - 20 ℃ (28.9 - 34.4% loss). After 35 days, temazepam glucuronide concentrations began to fluctuate significantly under all conditions, and an obvious increase (290.4-355.1%) was observed in 1.5 years. Oxazepam glucuronide was always unstable after 5 days, the percentage loss was even 100% when it was stored for 61 days and 1.5 years.

CONCLUSIONS

Dried blood spots on ordinary filter paper are recommended to be stored at 20 ℃ or 20 ℃ with 1% sodium fluoride within 16 days. Samples should be analyzed immediately or stored in sterile and dry media.

Driving anxiety and anxiolytics while driving: Their impacts on behaviour and cognition behind the wheel

Introduction

The interaction between road safety and drivers' mental health is an important issue to take into consideration on transportation and safety research. The present review deals specifically with the link between anxiety and driving activity from two complementary points of view.

Method

A systematic review into primary studies, following the PRISMA statement, was carried out in four databases: Scopus, Web of Science, Transport Research International Documentation and Pubmed. A total of 29 papers were retained. On the one hand, we present a systematic review of research articles exploring the cognitive and behavioural effects of driving anxiety, regardless its onset, when concerned people have to drive. The second goal of the review is to compile the available literature on the influence of legal drugs, which are used to fight against anxiety, on actual driving tasks.

Results

Eighteen papers have been retained for the first question, whose main findings show that exaggerated cautious driving, negative feelings and avoidance are associated with driving anxiety. Most of the conclusions were drawn from self-reported questionnaires and little is known about the effects in situ. Concerning the second question, benzodiazepines are the most studied legal drugs. They affect different attentional processes and could slow reaction times down depending on the population and treatment features.

Conclusions

The two standpoints included in the present work allow us to propose some possible lines of research to study certain aspects that have not been explored in depth about people who either feel apprehensive about driving or who drive under the effects of anxiolytics.

Practical applications

The study on driving anxiety may be crucial to estimate the consequences for traffic safety. Furthermore, it is relevant to design effective campaigns to raise awareness about the issues discussed. To propose standard evaluations of driving anxiety and exhaustive research works to find out the extent of anxiolytics use are also important to be considered for traffic policies.

Differential Contributions of GABA Concentration in Frontal and Parietal Regions to Individual Differences in Attentional Blink

Selective attention plays an important role in identifying transient objects in a complex visual scene. Attentional control ability varies with observers. However, it is unclear what neural mechanisms are responsible for individual differences in attentional control ability. The present study used the following attentional blink paradigm: when two targets are to be identified in rapid serial visual presentation, the processing of the first target interrupts the identification of the second one appearing within 500 ms after the first-target onset. It has been assumed that the reduction of the second-target accuracy is mainly due to a transient inhibition of attentional reorienting from the first to the second target, which is modulated by the GABA system. Using magnetic resonance spectroscopy, we investigated whether individual variation of attentional blink magnitude is associated with GABA concentrations in the left prefrontal cortex (PFC), right posterior-parietal cortex (PPC), and visual cortex (VC) of humans. GABA concentrations in the PFC were related negatively to attentional blink magnitude and positively to the first-target accuracy. GABA concentrations in the PPC were positively correlated with attentional blink magnitude. However, GABA concentrations in the VC did not contribute to attentional blink magnitude and first-target accuracy. Our results suggest that frontoparietal inhibitory mechanisms are closely linked with individual differences in attentional processing and that functional roles of the GABAergic system in selective attention differ between the PFC and PPC.

SIGNIFICANCE STATEMENT

Selective attention is the process of picking up task-relevant information in the environment. Attentional blink reflects time constraints of visual attention. It has been assumed that attentional blink is induced by the inhibition of attentional reorienting to other objects. This study used magnetic resonance spectroscopy to noninvasively measure concentrations of GABA, the principal inhibitory neurotransmitter, in the human brain. We show that a neural interaction between GABA concentrations in the prefrontal and posterior parietal regions accounts for the interindividual variability of attentional blink magnitude. Our results provide direct evidence that the GABAergic system in the frontoparietal networks is responsible for temporal aspects of attentional control ability.

Is attentional blink a byproduct of neocortical attractors?

This study proposes a computational model for attentional blink or “blink of the mind,” a phenomenon where a human subject misses perception of a later expected visual pattern as two expected visual patterns are presented less than 500 ms apart. A neocortical patch modeled as an attractor network is stimulated with a sequence of 14 patterns 100 ms apart, two of which are expected targets. Patterns that become active attractors are considered recognized. A neocortical patch is represented as a square matrix of hypercolumns, each containing a set of minicolumns with synaptic connections within and across both minicolumns and hypercolumns. Each minicolumn consists of locally connected layer 2/3 pyramidal cells with interacting basket cells and layer 4 pyramidal cells for input stimulation. All neurons are implemented using the Hodgkin–Huxley multi-compartmental cell formalism and include calcium dynamics, and they interact via saturating and depressing AMPA/NMDA and GABA_A synapses. Stored patterns are encoded with global connectivity of minicolumns across hypercolumns and active patterns compete as the result of lateral inhibition in the network. Stored patterns were stimulated over time intervals to create attractor interference measurable with synthetic spike traces. This setup corresponds with item presentations in human visual attentional blink studies. Stored target patterns were depolarized while distractor patterns where hyperpolarized to represent expectation of items in working memory. Simulations replicated the basic attentional blink phenomena and showed a reduced blink when targets were more salient. Studies on the inhibitory effect of benzodiazepines on attentional blink in human subjects were compared with neocortical simulations where the GABA_A receptor conductance and decay time were increased. Simulations showed increases in the attentional blink duration, agreeing with observations in human studies. In addition, sensitivity analysis was performed on key parameters of the model, including Ca²⁺-gated K⁺ channel conductance, synaptic depression, GABA_A channel conductance and the NMDA/AMPA ratio of charge entry.

Effects of lorazepam on visual perceptual abilities

OBJECTIVE

To evaluate the effects of an acute dose of the benzodiazepine (BZ) lorazepam in young healthy volunteers on five distinguishable visual perception abilities determined by previous factor-analytic studies.

METHODS

This was a double-blind, cross-over design study of acute oral doses of lorazepam (2 mg) and placebo in young healthy volunteers. We focused on a set of paper-and-pencil tests of visual perceptual abilities that load on five correlated but distinguishable factors (Spatial Visualization, Spatial Relations, Perceptual Speed, Closure Speed, and Closure Flexibility). Some other tests (DSST, immediate and delayed recall of prose; measures of subjective mood alterations) were used to control for the classic BZ-induced effects.

RESULTS

Lorazepam impaired performance in the DSST and delayed recall of prose, increased subjective sedation and impaired tasks of all abilities except Spatial Visualization and Closure Speed. Only impairment in Perceptual Speed (Identical Pictures task) and delayed recall of prose were not explained by sedation.

CONCLUSION

Acute administration of lorazepam, in a dose that impaired episodic memory, selectively affected different visual perceptual abilities before and after controlling for sedation. Central executive demands and sedation did not account for results, so impairment in the Identical Pictures task may be attributed to lorazepam's visual processing alterations.