Figure 7.

LFP recordings from DBS electrodes. (A) Correlated synaptic activity dominates the LFP and determines its spatial reach. A DBS electrode is shown implanted in the center of a volume of STN neurons. Neurons within a population radius (R ≤ R_correlated) receive highly synchronous synaptic inputs while the remaining neurons (R > R_correlated) receive uncorrelated synaptic inputs. Within correlated regions, an increase in the population radius produces a linear increase in the amplitude of the LFP. Outside of the correlated volume, there is no significant increase in the LFP amplitude. (B) Recording configuration effects on the LFP. In this example, all neurons receive correlated synaptic inputs. For a monopolar recording (red electrode only), the LFP amplitude increases linearly with an increase in the population radius and does not converge to a maximum value. However, a bipolar recording (red electrode—blue electrode) limits the amplitude and spatial reach of the LFP recording.