Spatial working memory specific activity in dorsal prefrontal cortex? Disparate answers from fMRI beta-weight and timecourse analysis.

Visual spatial processing and object processing rely on dorsal and ventral cortical pathways, respectively. Whether this functional segregation exists in the prefrontal cortex is currently a source of debate. Using functional MRI (fMRI), there has been some evidence that the superior frontal sulcus (within dorsal prefrontal cortex) is specialised for spatial working memory, while ventral prefrontal cortex is associated with object working memory. Employing beta-weight analysis, Postle, Berger, Taich, and D'Esposito (2000) challenged these results, finding no differential activity associated with spatial working memory versus two-dimensional saccades in the superior frontal sulcus. In the present reanalysis of Postle et al.'s data, both beta-weight analysis and event-related timecourse analysis were utilised. Beta-weight analysis results replicated Postle et al.; however, timecourse analysis revealed greater activity associated with spatial working memory versus two-dimensional saccades in the superior frontal sulcus. Thus, identical fMRI data analysed via distinct methods yielded results with different theoretical conclusions.