Prepared and Reactive Inhibition in Smokers and Non-smokers

Models of addiction have identified deficits in inhibitory control, or the ability to inhibit inappropriate or unwanted behaviors, as one factor in the development and maintenance of addictive behaviors. Current literature supports disruption of the prefrontal circuits that mediate reactive inhibitory control processes (i.e. inhibition in response to sudden, unplanned changes in environmental demands) in substance use disorders, however, the relationship between disorders of addiction, such as nicotine dependence, and planned inhibitory processes is unclear. The goal of the present study was to examine the extent to which reactive and planned inhibitory processes are differentially disrupted in nicotine dependent individuals. To this aim, we employed a novel stop signal task that explicitly separates planned and reactive inhibitory processes and assessed (1) group differences in task performance between smokers and non- smokers and (2) the relationship between task performance and smoking behaviors within the smoking group. We found significant differences in stop times for both trial between groups as well as within groups. Analyses of stopping behavior in the smoking group revealed an inverse correlation between stop times on planned stop trials and a measure of nicotine dependence derived from the Fagerstrom Test of Nicotine Dependence and, surprisingly, showed that greater daily average consumption of nicotine was inversely related to stop times for both trial types. Finally, we found that recency of the last cigarette smoked was unrelated to stopping behavior.

Modelling the Phosphorylation of Glucose by Human hexokinase I

In this paper, we develop a comprehensive mathematical model to describe the phosphorylation of glucose by the enzyme hexokinase I. Glucose phosphorylation is the first step of the glycolytic pathway, and as such, it is carefully regulated in cells. Hexokinase I phosphorylates glucose to produce glucose-6-phosphate, and the cell regulates the phosphorylation rate by inhibiting the action of this enzyme. The cell uses three inhibitory processes to regulate the enzyme: an allosteric product inhibitory process, a competitive product inhibitory process, and a competitive inhibitory process. Surprisingly, the cellular regulation of hexokinase I is not yet fully resolved, and so, in this study, we developed a detailed mathematical model to help unpack the behaviour. Numerical simulations of the model produced results that were consistent with the experimentally determined behaviour of hexokinase I. In addition, the simulations provided biological insights into the abstruse enzymatic behaviour, such as the dependence of the phosphorylation rate on the concentration of inorganic phosphate or the concentration of the product glucose-6-phosphate. A global sensitivity analysis of the model was implemented to help identify the key mechanisms of hexokinase I regulation. The sensitivity analysis also enabled the development of a simpler model that produced an output that was very close to that of the full model. Finally, the potential utility of the model in assisting experimental studies is briefly indicated.

Delayed Onset of Inhibition of Return in Visual Snow Syndrome

Visual snow syndrome (VSS) is a complex, sensory processing disorder. We have previously shown that visual processing changes manifest in significantly faster eye movements toward a suddenly appearing visual stimulus and difficulty inhibiting an eye movement toward a non-target visual stimulus. We propose that these changes reflect poor attentional control and occur whether attention is directed exogenously by a suddenly appearing event, or endogenously as a function of manipulating expectation surrounding an upcoming event. Irrespective of how attention is captured, competing facilitatory and inhibitory processes prioritise sensory information that is important to us, filtering out that which is irrelevant. A well-known feature of this conflict is the alteration to behaviour that accompanies variation in the temporal relationship between competing sensory events that manipulate facilitatory and inhibitory processes. A classic example of this is the “Inhibition of Return” (IOR) phenomenon that describes the relative slowing of a response to a validly cued location compared to invalidly cued location with longer cue/target intervals. This study explored temporal changes in the allocation of attention using an ocular motor version of Posner's IOR paradigm, manipulating attention exogenously by varying the temporal relationship between a non-predictive visual cue and target stimulus. Forty participants with VSS (20 with migraine) and 20 controls participated. Saccades were generated to both validly cued and invalidly cued targets with 67, 150, 300, and 500 ms cue/target intervals. VSS participants demonstrated delayed onset of IOR. Unlike controls, who exhibited IOR with 300 and 500 ms cue/target intervals, VSS participants only exhibited IOR with 500 ms cue/target intervals. These findings provide further evidence that attention is impacted in VSS, manifesting in a distinct saccadic behavioural profile, and delayed onset of IOR. Whether IOR is perceived as the build-up of an inhibitory bias against returning attention to an already inspected location or a consequence of a stronger attentional orienting response elicited by the cue, our results are consistent with the proposal that in VSS, a shift of attention elicits a stronger increase in saccade-related activity than healthy controls. This work provides a more refined saccadic behavioural profile of VSS that can be interrogated further using sophisticated neuroimaging techniques and may, in combination with other saccadic markers, be used to monitor the efficacy of any future treatments.

Emotional disorders

Emotional disorders in children with ADHD are often difficult to detect. The emotional problems that occur in children with ADHD fall into three categories: emotional characteristics of ADHD (low frustration tolerance, preoccupation, thrill-seeking, dysthymia, and overexcitability), reactive emotions to having ADHD, and coexisting emotional disorders (depression, anxiety, obsessive-compulsive disorder, and bipolar disorder). Inefficient inhibitory processes in the brain are the basis of these emotional difficulties. It is essential to be aware of the frequent occurrence of emotional disorders in children with ADHD. This chapter discusses emotional disorders in ADHD, including the emotional characteristics of ADHD, reactive emotions, and coexisting emotional disorders.

Specific features of inhibition processes in junior schoolchildren with the handedness of the different type

Within the present paper, we attempted to study specific features of inhibitory control in junior schoolchildren with the handedness of the different types. assessment of inhibitory control was fulfilled with the help of the method of recurrent biological feedback. The assessment of the type of handedness was performed through the set of tasks. resistance of inhibitory processes and stress resistance were identified in the right-handed children compared to the left-handed and mixed-handed children. This study might be useful in the area of psychophysiology of individual differences in children. Despite the abundance of literature on the study of executive functions, there is still no understanding of how inhibitory processes develop in the ontogenesis of children with different lateral preferences.

Inhibition-of-return-like effects in working memory? A preregistered replication study of Johnson et al . (2013)

The present study concerns a preregistered replication of the study conducted by Johnson et al . (Johnson et al. 2013 Psychol. Sci. 24 , 1104–1112 ( doi:10.1177/0956797612466414 )), in which they showed an inhibition-of-return-like effect in working memory. Inhibition of return is a well-known phenomenon observed in the field of perception and refers to the observation that it takes longer to look back at a location which has recently been explored than to look at an unexplored location. Working memory is a central concept in the field of cognitive psychology and refers to the capacity to process and maintain information simultaneously over short periods of time. Johnson's study applied the inhibition of return paradigm to the concept of working memory. Their results showed that it is harder to access a working memory representation that had just been thought of, i.e. refreshed, in comparison to an unrefreshed working memory representation. Contrary to this study of Johnson et al ., who observed refreshing to result in inhibitory processes, most studies on refreshing have described its effect as increasing/prolonging the level of activation of the memory representations. In an attempt to integrate these opposite patterns produced by ‘refreshing’, we started by replicating one of the studies on the inhibition of return in working memory reported by Johnson et al .