Intention and Attention: Different functional roles for LIPd and LIPv

Establishing the circuitry underlying attentional and oculomotor control is a longstanding goal of systems neuroscience. The macaque lateral intraparietal area, LIP, has been implicated in both processes, but numerous studies have produced contradictory findings. Anatomically, LIP consists of a dorsal and ventral subdivision, yet the functional significance of this division remains unclear. We co-injected muscimol, a GABAa agonist, and manganese, an MR-lucent paramagnetic ion, into different portions of LIP, testing the effect of the resulting reversible inactivation on saccade planning and attention, and visualized each injection using anatomical MRI. We find that LIPd is primarily an oculomotor planning region, while LIPv contributes to both attentional and oculomotor processes. Additional testing reveals that, even within LIPv, the two functions are dissociable. Thus our novel muscimol+Mn-MRI technique establishes clear structure-function relationships that distinguish LIPv from LIPd, and reveals dissociable circuits for attention and eye movements in the posterior parietal cortex.