Only Coherent Spiking in Posterior Parietal Cortex Coordinates Looking and Reaching

Here, we report that temporally patterned, coherent spiking activity in the posterior parietal cortex (PPC) coordinates the timing of looking and reaching. Using a spike-field approach, we identify a population of parietal area LIP neurons that fire spikes coherently with 15 Hz beta-frequency LFP activity. The firing rate of coherently active neurons predicts the reaction times (RTs) of coordinated reach-saccade movements but not of saccades when made alone. Area LIP neurons that do not fire coherently do not predict RT of either movement type. Similar beta-band LFP activity is present in the parietal reach region but not nearby visual area V3d. This suggests that coherent spiking activity in PPC can control reaches and saccades together. We propose that the neural mechanism of coordination involves a shared representation that acts to slow or speed movements together. Dean et al. selectively erased fast synchronous synaptic transmission in vivo, thereby blocking information transfer of isolated spikes but not of bursts of spikes. This approach revealed distinct coding schemes in memory circuits, with spike bursts sufficient for hippocampal encoding of memories.