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. 2012 Jan 9;135(1):148–160. doi: 10.1093/brain/awr315

Figure 4.

Figure 4

(A) Normalized power (mean ± SEM) of alpha peaks during gait and beta peaks during rest or gait grouped according to caudal (deeper than 2 mm below the pontomesencephalic junction) or rostral recording site. Alpha peak power was greater caudally and beta power was greater rostrally. (B) Log alpha peak power at rest (mean ± SEM) divided according to recording site depth into 4-mm subregions (denoted on the x-axis in mm relative to the pontomesencephalic junction). Log alpha peak power is maximal in the −2 to −6 mm region, falling significantly at surrounding sites. *P < 0.05. In grey has been superimposed a plot of the variation in per cent improvement in the Gait and Falls questionnaire (GFQ) postoperatively according to stimulation depth at most recent follow-up [depth selected blinded to the local field potential (LFP) data]. One data point was available from each subject (Table 2), with the exception of the patient from London, where the Gait and Falls questionnaire was not assessed. Three of these data points fell −6 to −10 mm below the pontomesencephalic junction, so that here the SEM is also displayed. (C) Representation of the rostrocaudal location of peak un-normalized alpha power at rest, which correlated strongly in frequency and location with peak alpha power that correlated with gait (but which required normalization to remove movement artefact thereby also diminishing power gradients). Relative log alpha power is represented in grey-scale intensity whereby black is highest and white lowest alpha power. Regions relative to the pontomesencephalic line are numbered as follows: 1, +2 to +6 mm; 2, −2 to +2 mm; 3, −6 to −2 mm; 4, −10 to −6 mm; and 5, −14 to −10 mm. Alpha power was maximal at location 3 (−6 to −2 mm below the pontomesencephalic line). Beta power was highest in regions 1 and 2 combined. Note: no inference is made regarding location in ventrodorsal or mediolateral planes. DBS = deep brain stimulation; GFQ = Gait and Falls questionnaire; LFP = local field potential; PM = pontomesencephalic line connecting the pontomesencephalic junction to the caudal end of the inferior colliculi.