Providing prior information about the location of a signal to be detected increases its detectability. However, whether the perceptual enhancement observed at the cued location is due to an overall reduction of internal noise or to a sharper signal-matching mechanism remains unclear. This study  manipulates independently two types of prior expectations during a cued signal-detection task at psychophysical threshold - the relevant spatial location for task performance versus the likely presence of a target to be detected. Behavioural results show clear dissociation between these two effects on performance variables. MEG recordings will reveal the how the implementation of these two types of biases on neural measures of visual and motor processing. (Supported by the Wellcome Trust)

Further reading:

Wyart V, Tallon-Baudry C (2009) How ongoing fluctuations in human visual cortex predict perceptual awareness: baseline shift versus decision bias. J Neurosci. 29(27):8715-25.