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Title: The effects of internally versus externally directed attention on the human electroencephalogram
Author: Cooper, Nicholas Robert
ISNI:       0000 0004 2743 3164
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2003
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This study was carried out in order to test the intake-rejection hypothesis and examine the functional significance of the associated EEG bands. This model argues that the nervous system reacts differently according to the locus of attention, traditionally interpreted as a differentiation between externally and internally directed attention, but work in this field remains fragmented and often contradictory. Experiment 1 was an exploratory study examining differences between internal and external attention using a mental arithmetic versus auditory signal detection protocol. Contrary to expectations, effects were observed in the fast EEG bands, where power was greater during internal attention than during external attention. Experiment 2 employed a multi-modal mental imagery (auditory, haptic and visual) versus sensory-intake protocol. Effects in all modalities in the alpha band were noted showing greater power during internally directed attention. Other less ubiquitous effects were also observed, including differences according to task difficulty in the theta band. Experiment 3 was a constructive replication of the second experiment. Improvements were made to the protocol enabling both increased confidence in the experimental findings and a more detailed topographical analysis of the data. Again, consistent experimental effects were observed in the alpha band. Experiment 4 sought to answer several questions arising from experiments 2 & 3, in particular whether the findings resulted from an evoked component in the EEG deriving from the externally directed attentional stimuli. Results indicated that changes in the alpha band reflect a modulation of the induced component of the EEG caused by attention to mental imagery. These findings suggest that changes in the alpha bandwidth (and other components) of the human EEG maybe seen as an index of attention to mental imagery possibly reflecting top-down executive cortical control mechanisms.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available