Executive control among adolescent inhalant and cannabis users.

INTRODUCTION AND AIMS: Inhalants are frequently among the first drugs abused by adolescents; however, little is known about how chronic inhalant abuse affects cognition (e.g. executive functioning). Several studies have examined cognitive deficits among inhalant users; however, no study has thoroughly addressed the confounding issues frequently associated with inhalant users (e.g. polysubstance use). The aim of the current study was to examine possible deficits in cognitive control among young, regular inhalant users and explore the relationship between inhalant use and executive functioning. DESIGN AND METHODS: Three groups (n = 19) of young people (aged 14-24) were recruited: an inhalant-using group, a drug-using control group and a community control group. The inhalant and drug-using controls were matched on demographic, clinical and substance use measures. All three groups were matched on age, sex and education. Cognitive control was assessed using Stroop and Go/No-Go tasks. RESULTS: There were no significant differences in performance between the groups on any measure. However, three measures (incongruent reaction times and congruent errors for the Stroop and omission errors for the Go/No-Go) were significantly correlated with inhalant use measures, suggesting inhalant use was associated with poorer performance. DISCUSSION AND CONCLUSIONS: The lack of significant differences between the groups is surprising; however, it raises important questions regarding cognitive deficits among chronic inhalant users. Further longitudinal studies using well-matched control participants are required to delineate the nature and timing of cognitive and neurobiological pathology among adolescent inhalant users.

Verbal memory, learning, and executive functioning among adolescent inhalant and cannabis users.

OBJECTIVE: Inhalant use is a common form of drug misuse among young adolescents. However, very little is known about how chronic inhalant misuse affects cognition. Several studies have examined cognitive deficits among inhalant users, but no study has thoroughly addressed the confounding issues frequently associated with inhalant users (e.g., polysubstance use). The aim of the current study was to examine possible deficits in memory, learning, and executive components of memory (interference susceptibility) among young, regular inhalant users relative to a statistically equivalent drug-using control group (primarily cannabis users) and a community control group. METHOD: Three groups of 21 young people (aged 13-24 years) were recruited: an inhalant- using group, a drug-using control group, and a community control group. The inhalant and drug-using controls were matched at the group level on demographic, clinical, and substance use measures. All three groups were statistically equivalent on age, sex, and education. The Rey Auditory Verbal Learning Test was used to assess memory, learning, and interference susceptibility. RESULTS: Community controls performed significantly better than both drug-using groups, while inhalant users were more susceptible to proactive interference relative to drug-using controls. CONCLUSIONS: Difficulty in successful proactive interference resolution demonstrated by the inhalant group may relate to inhalant-specific deficits in executive functioning. These findings raise important questions regarding the hypothesized toxicity of inhalants and of substance-specific cognitive deficits among regular adolescent substance users. Future studies should consider using more specific, experimental probes of cognitive functioning to identify potentially subtle changes among substance-using adolescents.

The influence of attention and age on the occurrence of mirror movements.

This study utilised a finger force task to investigate the influence of attention and age on the occurrence of motor overflow in the form of mirror movements in neurologically intact adults. Forty right-handed participants were recruited from three age groups: 20-30 years, 40-50 years, and 60-70 years. Participants were required to maintain a target force using both their index and middle fingers, representing 50% of their maximum strength capacity for that hand. Attention was directed to a hand by activating a bone conduction vibrator attached to the small finger of that hand. Based on Cabeza's (2002) model of hemispheric asymmetry reduction in older adults, it was hypothesised that mirror movements would increase with age. Furthermore, it was expected that when the attentional demands of the task were increased, motor overflow occurrence would be exacerbated for the older adult group. The results obtained provide support for the model, and qualified support for the hypothesis that increasing the attentional demands of a task results in greater motor overflow. It is proposed that the association between mirror movements and age observed in this study may result from an age-related increase in bihemispheric activation that occurs in older adults, who, unlike younger adults, benefit from bihemispheric processing for task performance.