Behavioral/Systems/Cognitive Movement Intention Is Better Predicted than Attention in the Posterior Parietal Cortex

We decoded on a trial-by-trial basis the location of visual targets, as a marker of the locus of attention, and intentions to reach and to saccade indifferent directionsusing the activity of neurons in theposterior parietal cortexof twomonkeys. Predictionsof target locations were significantly worse than predictions ofmovement plans for the same target locations.Moreover, neural signals in the parietal reach region (PRR) gave better predictions of reaches than saccades, whereas signals in the lateral intraparietal area (LIP) gave better predic-tions of saccades than reaches. Taking together the activity of both areas, the prediction of either movement in all directions became nearly perfect. These results cannot be explained in terms of an attention effect and support the idea of two segregated populations in the posterior parietal cortex, PRR and LIP, that are involved in different movement plans. Key words: attention; motor intention; single-trial analysis; population coding; vision; parieta