Spatial attention is effector Agnostic, movement intention is effector Specific
To grasp the red apple, a robot needs to: identify the object, come up with a motor plan, and execute it. Information concerning both spatial attention and movement intention can be found in the PPC (posterior parietal cortex). Spatial attention is the way we orient our attention to a specific location in space. Spatial attention can be moved independently of any effector (e.g. hand or eyes). Movement intentions are movement plans directed to a location in space that are specific for each effector. Spatial attention consists of orienting our attention to the object location, and it’s independent from the effector. Conversely, movement intention consists of planning to move to the object location, and it’s specific to the effector. The Posner paradigm investigates attentional capture for spatial attention without effector movement. In the saccade task, a monkey has to memorize the flash location, and later move its eyes to that location. In the reaching task, a monkey has to memorize the flash location, and later move the hand to the target location. By comparison the saccade and reach task, we get different motor intentions, but similar same spatial attention. If PPC reflects movement intentions, we expect different activity during the two tasks, because they’re effector-specific. Activity in the LIP area (Lateral Intraparietal) differs between the saccade and reach trials, with higher activity for saccade trials. LIP codes for saccade motor plans. In contrast, PRR (Parietal Reach Region) shows higher activity during reach trials, so it might code for reaching plans. Spatial attention and movement intentions can be experimentally separated in the memory task. There are separate areas in the PPC that code the specific motor plan, with LIP for saccade and PRR for reaching.