An investigation into the effects of glucose and caffeine on multitasking, mood and fMRI

This study will employ a double blind, randomised, placebo controlled, four way cross-over design. Participants will be required to attend one practice session followed by four testing sessions. During the practice session particpants will sign the consent form and practice the multi-tasking assessment and be familiarised with the mood scales and other procedures. The testing sessions will see participants taking one of four interventions: (1) Caffeine drink (40mg caffeine) (2) Caffeine and Glucose Drink (25mg Glucose, 40mg caffeine) (3) Caffeine and Glucose Drink (60mg Glucose, 40mg caffeine) (4) Placebo All four treatments will be administered as carbonated drinks and will be matched for colour, smell and taste. On the testing days participants will complete baseline testing (consisting of the multitasking framework, mood) after which they will be administered their randomly assigned treatment. 30 minutes post dose participant will complete the testing again (multitasking framework, mood). 20 participants will additionally complete the fMRI component which will take an additional hour and a half at the end of each treatment arm (60 minutes post dose). Once in the scanner participants will have a structural scan followed by the functional scans in which they will complete two cognitive tasks. There will be a seven day washout period between each testing session. Participants will be randomly allocated to receive either treatment (1) or (2) or (3) or (4) on their first testing day. This will be done by a randomised computer number sequence generator. Over the course of the investigation, they will complete all four treatments with treatment order counterbalanced across participants. A disinterested third party will be responsible for the blinding procedure.