title: Event-related potential responses to perceptual reversals are modulated by working memory load.
abstract: While viewing ambiguous figures, such as the Necker cube, the available perceptual interpretations alternate with one another. The role of higher level mechanisms in such reversals remains unclear. We tested whether perceptual reversals of discontinuously presented Necker cube pairs depend on working memory resources by manipulating cognitive load while recording event-related potentials (ERPs). The ERPs showed early enhancements of negativity, which were obtained in response to the first cube approximately 500 ms before perceived reversals. We found that working memory load influenced reversal-related brain responses in response to the second cube over occipital areas at the 150-300 ms post-stimulus and over central areas at P3 time window (300-500 ms), suggesting that it modulates intermediate visual processes. Interestingly, reversal rates remained unchanged by the working memory load. We propose that perceptual reversals in discontinuous presentation of ambiguous stimuli are governed by an early (well preceding pending reversals) mechanism, while the effects of load on the reversal related ERPs may reflect general top-down influences on visual processing, possibly mediated by the prefrontal cortex.
authors.affiliation: Visual Neuroscience Laboratory, IBILI, Faculty of Medicine, University of Coimbra, Azinhaga De Santa Comba, Celas, 3000-548 Coimbra, Portugal. Electronic address: mintaite@fmed.uc.pt.
authors.forename: Monika
authors.initials: M
authors.lastname: Intaitė
authors.affiliation: Centre for Cognitive Neuroscience, University of Turku, 20014 Turku, Finland; Department of Psychology, University of Turku, 20014 Turku, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Koivisto
authors.affiliation: Visual Neuroscience Laboratory, IBILI, Faculty of Medicine, University of Coimbra, Azinhaga De Santa Comba, Celas, 3000-548 Coimbra, Portugal.
authors.forename: Miguel
authors.initials: M
authors.lastname: Castelo-Branco
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D055815:Young Adult
keywords: Ambiguous figure; Cognition; EEG/ERP; Normal volunteers; Working memory load