The role of cortical oscillations in the estimation and maintenance of sensory and duration information in working memory

Shrikanth Kulashekhar

Forskningsoutput: AvhandlingDoktorsavhandlingSamling av artiklar


Working memory is used to maintain information for cognitive operations, and its deficits are associated with several neuropsychological disorders. Human functional magnetic resonance imaging (fMRI) f isolated key brain areas associated with the maintenance of sensory and duration information. However, the systems-level mechanisms coordinating the collective neuronal activity in these brain areas have remained elusive. It has been suggested that synchronized oscillations could regulate communication in neuronal networks and could hence serve such coordination, but their role in the maintenance of sensory and duration information has remained largely unknown. In this thesis, combined magnetoencephalography (MEG) and electroencephalography (EEG) together with minimum norm estimate (MNE) based source modelling was used to study the oscillatory dynamics underlying visual and temporal working memory. In Publication I, we developed a neuro-informatics approach to understand the anatomical and dynamic structures of network synchrony supporting visual working memory (VWM). VWM was associated with a sustained and stable inter-areal phase synchrony among frontoparietal and visual areas in alpha- (10 13 Hz), beta- (18 24 Hz), and gamma- (30 40 Hz) frequency bands. In this study, the subjects' individual behavioural VWM capacity was predicted by synchrony in a network in which the intraparietal sulcus was the most central hub. In Publication II, we characterised the oscillatory amplitude dynamics associated with the VWM maintenance. Increasing VWM load was associated with strengthened oscillation amplitudes in the occipital and occipitotemporal cortical areas, in the alpha (8 14 Hz) beta- (15 30 Hz), gamma- (30-50 Hz), and high-gamma- (50 150 Hz) frequency bands. In Publication III, we addressed the functional significance of local neuronal synchronization, as indexed by the amplitudes of cortical oscillations, in the estimation and maintenance of duration information. The estimation of durations in the seconds range was associated with stronger beta-band (14 30 Hz) oscillations in cortical regions that have earlier been associated with temporal processing. The encoding of duration information was associated with strengthened gamma- (30 120 Hz), and the retrieval and comparison with alpha-band (8 14 Hz) oscillations. Further, the maintenance of stimulus duration was associated with stronger theta- and alpha-band (5 14Hz) frequencies. These data suggested that both local and large-scale phase synchrony in the alpha-, beta-, and gamma-frequency bands in the frontoparietal and visual regions could be a systems level mechanism for coordinating and regulating the maintenance of visual information in VWM. In addition, it suggested that beta-band oscillations may provide a mechanism for estimating short temporal durations, while gamma, alpha and theta-alpha oscillations support their encoding, retrieval, and maintenance in working memory, respectively.
Tilldelande institution
  • Helsingfors universitet
  • Palva, Satu, Handledare
  • Palva, Matias, Handledare
Tilldelningsdatum20 jan. 2017
Tryckta ISBN978-951-51-2858-4
Elektroniska ISBN978-951-51-2859-1
StatusPublicerad - 20 jan. 2017
MoE-publikationstypG5 Doktorsavhandling (artikel)


  • 3112 Neurovetenskaper

Citera det här