Gain fields for hand

and gaze position were accounted for separately in the model by the parameters gH and gG (see Experimental Procedures for more details about the model). The cell shown in Figure 3 was well fit by the model (r2 = 0.87) and had a weight parameter, w, of 0.03, which corresponds to a hand-centered reference frame and is consistent Dactolisib datasheet with the results from the separability analysis. A six-parameter hand-centered model with x = T-H fit the firing rates for this cell just as well as the full seven-parameter model (F test, p = 0.43; r2 = 0.87), whereas models with x = T-G (gaze-centered) and x = T (body- or screen-centered) fit the data significantly worse than the full model (r2 = 0.47 and r2 = 0.54 respectively, p < 0.00001

for both F tests). Figure 6 shows the distribution GSK1120212 datasheet of the weight parameter w across the population of recorded cells (n = 128). The median value was 0.04, and the modal bin was the one centered on w = 0 (hand centered). Consistent with other recent reports ( McGuire and Sabes, 2011), the population was not homogeneous and contained some gaze-centered cells (w∼ = 1) as well as cells with an intermediate reference frame (0 < w < 1). However, the overall trend in the population was toward a hand-centered representation, supporting the results from the SVD/gradient analysis. The hand-centered model fit as well as the full model in 38% of cells (F test,

p > 0.01), whereas the gaze-centered model fit as well as the full model in only 17% of cells. The full model fit better than either reduced model in 29% of cells and both reduced models fit as well as the full model in the remaining 16% of cells. The model uses a Gaussian function for fitting, which is appropriate for cells with a Sodium butyrate peaked response. Most of our recorded cells (108/128; 84%) had a response peak within the working range. The shape of the weights distribution when including only these cells was very similar to that for the entire population (Figure S3A), as was the distribution for the subset of cells with values of r2 greater than 0.6 (n = 75; Figure S3B). We found that the reach vector, or target position relative to the hand, is the principal representation in parietal area 5d during planning of reaches, and that there is a marked absence of coding for the position of the hand relative to gaze (Figures 4, 5, and 6). This hand-centered coding is distinct from the predominantly gaze-centered reference frame reported for the neighboring PRR (Batista et al., 1999; Buneo et al., 2002; Pesaran et al., 2006) and suggests that the two regions subserve different functions.