Mood manipulation and attentional processes : electrophysiological investigations of the affect-cognition interaction
Although there has been considerable research into the effects of major affective disorders on perception and cognition, there has been less focus on the influence of everyday fluctuations in mood on general cognitive skills. Neurocognitive models of affect-cognition interactions implicate frontal cortical networks and predict that where task control is reliant on such networks, there will be a greater negative impact of mood change. The initial study in this thesis compared the effectiveness of 3 standard mood induction techniques as assessed by a subjective mood assessment instrument. The most effective changes were only evident with the induction of negative mood, using the Velten Mood induction technique, which was therefore adopted for subsequent studies. Three further studies employed a within-subject design, investigating the effect of neutral and negative mood on 3 tasks selected for a) increasing levels of cognitive demand and complexity, and b) the increasing involvement of frontal areas of control. Event-related potentials (ERPs) were measured using a 128 channel dense array system. It was predicted that mood induction would differentially activate the frontal areas, as measured by increased negative amplitude in frontal ERPs, lateralised to the left: hemisphere, and be associated with changes in task performance and the associated ERP 'signature'. The first task, an 'odd-ball' task, was oflow cognitive demand and associated with centralparietal control, and showed no disruption at the behavioural or cortical level. The second task, a standard Stroop task, also showed no behavioural disruption but there were moodrelated differences in frontal ERPs. Increases in negativity caused the pattern of activity associated with congruent and incongruent trials to be reversed. The final task, an N-back working memory task, again showed minimal disruption at the behavioural level, but significant differences in lateralised frontal activity as a function of mood. Again, increased negativity within in left: hemisphere led to a reversal of asymmetry during the cognitively demanding 3-back task. The data are interpreted in terms of Ellis and Ashbrook's Resource Allocation Model, which predicts that depressed moods lead to a reduction in the capacity of resources allocated to the control of cognitive tasks. It is concluded that the maintenance of performance is associated with increased allocation of cortical resources.