V1 is not uniquely identified by polarity reversals of responses to upper and lower visual field stimuli.

ABSTRACT: The cruciform hypothesis states that if a visual evoked potential component originates in V1, then stimuli placed in the upper versus lower visual fields will generate responses with opposite polarity at the scalp. This diagnostic has been used by many studies as a definitive marker of V1 sources. To provide an empirical test of the validity of the cruciform hypothesis, we generated forward models of cortical areas V1, V2 and V3 that were based on realistic estimates of the 3-D shape of these areas and the shape and conductivity of the brain, skull and scalp. Functional MRI was used to identify the location of early visual areas and anatomical MRI data was used to construct detailed cortical surface reconstructions and to generate boundary element method forward models of the electrical co

SUBMITTER: Ales JM 

PROVIDER: S-EPMC2922686 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature