BRAIN IMAGINGInvestigating evoked and induced electroencephalogram activity in task-related alpha power increases during an internally directed attention taskCooper, Nicholas R.a; Burgess, Adrian P.a; Croft, Rodney J.b; Gruzelier, John H.a Author Information aDivision of Neuroscience and Psychological Medicine, Faculty of Medicine, Imperial College London, UK bBrain Sciences Institute, Swinburne University of Technology, Hawthorn, Australia Correspondence and requests for reprints to Dr Nicholas Robert Cooper, PhD, Alfred Psychiatry Research Centre, APRC, Alfred Hospital, Old Baker Building, Commercial Road, Melbourne, Victoria 3004, Australia Tel: +61 (0)3 9276 6594; fax: +61 (0)3 9276 6588; e-mail: [email protected] Sponsorship: This study was supported by a grant from the Institut für Grenzgebiete der Psychologie und Psychohygiene, Freiburg, Germany. Received 8 November 2005; revised 17 November 2005; accepted 18 November 2005 NeuroReport 17(2):p 205-208, February 6, 2006. Buy Abstract This study sought to explore whether the so-called ‘paradoxical’ task-related increases in the α bandwidth of the human electroencephalogram result from increases in evoked (phase locked), as opposed to induced (non-phase locked), activity. The electroencephalograms of 18 participants were recorded while they engaged in both auditory sensory-intake tasks (listening to randomly generated ‘tunes’) and internally directed attention tasks (imagining the same randomly generated tunes) matched for auditory input. Measures of evoked (phase locked) and induced (non-phase locked) activity were compared between tasks. Increases in induced α power were found during internal attention. No experimental effects were observed for evoked activity. These results are not entirely consistent with proposals that ‘paradoxical’ α indexes the evoked inhibition of task irrelevant processing. © 2006 Lippincott Williams & Wilkins, Inc.