Parietal Neurons are Activated by Smooth Pursuit of Imaginary Targets

Abstract

The interpretation of the function of the primate posterior parietal cortex has been influenced for many years by conflicting interpretations of the response properties of posterior parietal cortex neurons, leading to very different and even exclusive interpretations of parietal lobe functions. In the 1970s, neuroscientists began to study the properties of neurons recorded from area 7 of primate posterior parietal cortex using paradigms which required monkeys to direct either their eyes or their hands to visual targets in extrapersonal space (Hyvarinen and Poranen 1974; Mountcastle et al. 1975). Since many of the neurons studied were active in conjunction with distinct oculomotor behaviors such as fixation, saccades, or smooth pursuit, or alternatively in conjunction with visually directed hand movements, Mountcastle et al. (1975) suggested that the neuronal activation reflected commands for the execution of movements to objects in extrapersonal space. Not much later, Robinson and coworkers arrived at a very different interpretation of eye or hand movement related single unit responses (Robinson et al. 1978). Instead of interpreting posterior parietal cortex as a command device programming movements directed to targets in extrapersonal space, they suggested, alternatively, that the posterior parietal cortex of monkeys should be understood as a sensory structure extracting relevant information by focusing spatial attention to relevant sensory stimuli.