Does Event Related Desynchronization reveal anticipatory attention in the somatosensory modality?
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Attention that is directed at an upcoming stimulus is termed anticipatory attention. The extended thalamocortical gating model (Brunia, 1999) addresses the processes underlying anticipatory attention. ...
Attention that is directed at an upcoming stimulus is termed anticipatory attention. The extended thalamocortical gating model (Brunia, 1999) addresses the processes underlying anticipatory attention. According to this model, both the thalamic relay (TCR) nuclei and the reticular nucleus (RN) are involved in the selection (i.e. gating) of the relevant sensory modality. The TCR nuclei can fire in two modes. The tonic mode is associated with the transmission of afferent and subcortical input to the cortex and leads to desynchronization of 10 Hz rhythmic activity in the cortical projection area of the TCR nucleus. The burst mode is associated with a disruption in this transmission and results in the occurrence of 10 Hz rhythmic activity at the cortical projection area. This implies that event-related changes in 10 Hz activity in the scalp recorded EEG may give insight into the firing mode of the TCR nuclei and thus into the process of anticipatory attention. Event Related Desynchronization (ERD, Pfurtscheller & Aranibar, 1977) can quantify such changes. The extended thalamocortical model states that anticipatory attention is manifest as a prestimulus activation of the sensory cortex corresponding to the modality of the anticipated stimulus. Anticipatory attention to somatosensory stimuli would therefore be manifest as a 10 Hz ERD over the postcentral cortex, whereas anticipatory attention to visual stimuli would be manifest as a 10 Hz ERD over the occipital cortex. To test this hypothesis 9 subjects performed a time-estimation task. They received a Knowledge of Results (KR) stimulus 2 seconds after their manual response. ERD was recorded in the 10 Hz and 20 Hz frequency bands. An occipital ERD was present preceding visual KR stimuli, whereas no significant postcentral ERD was present prior to somatosensory KR stimuli. Nonetheless, the statistical analyses indicated that these differences between conditions were not significant. Therefore, these results do not support the extended thalamocortical gating model. It can be hypothesized that the postcentral ERD preceding somatosensory stimuli is masked by a postmovement Event Related Synchronization (ERS).
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