Glucose Administration Effects On Sensorimotor Function and Declarative Memory.

This thesis aimed to examine the effects of glucose drink administration on sensorimotor function (studies 1 - 3) and declarative memory (study 4). Glucose had no effect on a modified version of the Hick task in study 1. However in study 2 we observed that glucose slowed reaction times (RTs) during the initial performance of the Eriksen flanker task. One possible reason for this effect is that glucose only slows sensorimotor function when a response is weakly associated with a stimulus, such as at the beginning of task performance. In study 1 stimulus-response (S-R) associations may have been too strong to observe a glucose slowing effect. Here participants performed a greater number of training trials and stimuli were arguably mapped more directly to a response compared to study 2. In study 3 we tested the hypothesis that glucose slows sensorimotor function when S-R associations are weak. Here we used a letter version of the Eriksen flanker task and kept S-R association consistently low by changing the stimulus set to a novel pair of letters every 80 trials. We found that glucose constantly slowed RTs for the duration of this task, a result which is congruent with the hypothesis that glucose slows sensorimotor function when S-R associations are weak. In study 4 we focused on the effects of glucose administration on declarative memory function and sought to determine whether glucose affected the encoding of stimuli in a word recognition task. Here we used ERPs as an online measure of encoding processes. Our findings were that glucose enhanced recognition performance, replicating the well established effect that glucose-facilitates declarative memory. Furthermore, during encoding, glucose affected ERP components associated with early sensory processing, visual word-form generation, lexical/semantic access and long-term memory encoding/consolidation. Furthermore there was a correlation between recognition performance and the degree to which glucose amplified the N400 component, an ERP potential associated with lexical/semantic access. The results of this study therefore indicate that glucose modulates encoding processes and that these effects may, at least partially, underlie the glucose facilitation of declarative memory.