Recent work has suggested that the prefrontal cortex (PFC) plays a key role in context-dependent perceptual decision-making. In this study, we addressed that role using a new method for identifying task-relevant dimensions of neural population activity. Specifically, we show that the PFC has a multidimensional code for context, decisions and both relevant and irrelevant sensory information. Moreover, these representations evolve in time, with an early linear accumulation phase followed by a phase with rotational dynamics. We identify the dimensions of neural activity associated with these phases and show that they do not arise from distinct populations but from a single population with broad tuning characteristics. Finally, we use model-based decoding to show that the transition from linear to rotational dynamics coincides with a plateau in decoding accuracy, revealing that rotational dynamics in the PFC preserve sensory choice information for the duration of the stimulus integration period.
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Data are available for download at https://www.ini.uzh.ch/en/research/groups/mante/data.html.
Demo code for the mTDR method is available for MATLAB at http://www.mikioaoi.com/samplecode/RDRdemo.zip
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This work was supported by grants from the McKnight Foundation, the Simons Collaboration on the Global Brain (SCGB AWD543027 to M.C.A. and J.W.P.), the National Institutes of Health BRAIN Initiative (R01EB026946 and NS104899 to J.W.P.), the National Science Foundation CAREER Award (IIS-1150186 to J.W.P.) and a U19 NIH-NINDS BRAIN Initiative Award (5U19NS104648 to M.C.A. and J.W.P.). V.M. was supported by the Swiss National Science Foundation (SNSF Professorship PP00P3-157539), the Simons Foundation (to W. T. Newsome and V.M., award 328189), the Swiss Primate Competence Center in Research, the Howard Hughes Medical Institute (through W. T. Newsome, investigator) and the DOD ∣ USAF ∣ AFMC ∣ Air Force Research Laboratory: W. T. Newsome, agreement number FA9550-07-1-0537.
The authors declare no competing interests.
Peer review information Nature Neuroscience thanks John Cunningham, Camillo Padoa-Schioppa and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended Data Fig. 1 Projections of population PSTH’s onto the first, second, and third PC-axes for monkey A.
a, The abs(motion) and b, abs(color) subspaces. Subspaces have been orthogonalized with respect to the first dimension of the choice subspace. The monkey gave the correct response for all trials used. Colored axes indicate dominant axes in the early, middle, and late periods of the stimulus epoch, as determined by the methods described in Supplementary section 9. Purple vertical lines indicate transition from the early to middle epochs. Yellow vertical lines indicate transition from the middle to late epochs as in Figure Figure 4. Plotting colors are the same as those in Figure 4. Units of the ordinate are arbitrary but all axes are on the same scale.
Projections are onto the first two jPCA axes identified by the trajectories shown in Figure 4. The jPCA axes reveal strongly rotational dynamics for motion, color, choice, and context subspaces.
Extended Data Fig. 3 Projections of population PSTH’s for monkey F onto the first, second, and third PC-axes of all task variables subspaces.
Plotting conventions and analyses are the same as those for Figure 4. Projected data is averaged over 2-folds of cross validated projections where a random sampling of half of the data was used to estimate parameters and the remaining half used to make projections.
Extended Data Fig. 4 Encoding strength of population pseudosamples for monkey F onto the first three axes of all task variables subspaces.
Plotting conventions and analyses are the same as those for Figure 4. Projected data is averaged over 2-folds of cross validated projections where pseudosamples were drawn from held-out trials. Grey bars at y = 0 indicate time points where the mTDR projections had significantly stronger encoding across all stimulus levels than the 1D projections (left-tailed Wilcoxon signed-rank test, pFDR45 controlled at .01).
Plotting conventions are the same as for Figure 5. a, Proportion of variance among seqPCA axes. Each marker corresponds to one neuron. The position of each neuron indicates the distribution of variance from PSTHs across corresponding early, middle, and late axes. e.g. a point that lies closer to the ‘early’ vertex of the motion plot has more of its motion-specific variance explained by the early axis while a point in the middle of the simplex has variance equally distributed across all axes. Darker regions indicate higher density of points. Colored dots correspond to cells displayed in Figure 3. b, Weights of the top (in terms of variance explained) 3 axes for all cells for motion, color, and choice subspaces. Cell indexes are sorted according to the choice weights from most positive to most negative. c, Magnitude of the Pearson correlation between top 3 subspace axes. The magnitude is used because the axes are only identifiable up to a sign. Markers indicate significant correlations controlled by the positive false discovery rate45)(* Q < .01, +Q < .01). Null distribution is based on the positive half-Gaussian with zero-mean and standard deviation σ0 = 1/n, where n = 640 is the number of neurons. Significant correlations are most consistent between color-choice and motion-choice pairs.
a, Projections of population PSTH’s for monkey F onto the jPC-axes of all task variables subspaces. Plotting conventions and analyses are the same as those for Figure 4. Projected data is averaged over 2-folds of cross validated pro- jections where a random sampling of half of the data was used to estimate parameters and the remaining half used to make projections. b, Angle of rotation over time for low-D trajectories of monkey F. Rotation angle tra- versed through rotational projection using jPCA. Angle was calculated starting from time when the projection transitions between the early and middle epochs. Coherent traversal across stimulus strengths that is con- sistent and monotonically increasing is an indication of rotation. Shaded areas are 95% confidence regions calculated using a maximum entropy method 23 (n = 100 samples) under the null hypothesis of no population structure other than the empirical means and covariances across time, neurons, and task conditions.
Plotting conventions and analyses are the same as for Figure 6 a, Top: Decoded motion coherence by mTDR model in both contexts. Bottom: Mean squared error (MSE) over time of motion coherence decoding across stimulus levels and context. MSE decreases precipitously, and then stabilize around the time of the first transition. b, Same as a) for color coherence decoding. Shaded regions indicate 50% confidence intervals. Dashed lines indicate error trials from the corresponding context for the lowest stimulus strengths. 100 pseudotrials for each of 2-fold cross validation used for each analysis. Solid vertical lines indicate the time of early/middle axis transition for the corresponding stimulus subspace projections. Dashed vertical lines indicate the time of middle/late transition.
Plotting conventions and analyses are the same as for Figure 6 a, Log-likelihood ratios (LLRs) in favor of a preferred choice using single pseu- dotrials from color - context (gold-blue, sorted by color coherence) and motion - context (red-violet, sorted by motion coherence) trials. Shaded regions indicate 95% quantile intervals for each stimulus strength. Solid lines indicate the median of correct trials. Dashed lines indicate median of error trials. b, Probability of a preferred choice based on corresponding LLRs combined over all stimulus strengths (see section 6.3 for details). Solid lines indicate median of correct trials. Dashed lines indicate median of error trials. Shaded regions indicate quantile coverage intervals of correct trials (light-to-dark: 95%,75%,50%). 100 pseudotrials for each of 2-fold cross validation folds used for all analyses. c, LLRs for in favor of a preferred choice where the choice subspace has been restricted to only the early, middle, or late axes. d, Probability of a preferred choice based on LLRs from (c).
a, LLRs for monkey A in favor of the motion context using single pseudotrials, sorted by color coherence. Shaded regions indicate 95% quantile intervals for each stimulus strength. Solid lines indicate the median over correct trials. Dashed lines indicate median of error trials. b, Probability of the motion context based on corresponding LLRs combined over all stimulus strengths. Solid lines indicate median of correct trials. Dashed lines indicate median of error trials. Shaded regions indicate quantile intervals of correct trials (light-to-dark: 50%, 75%, 95%). Color conventions are the same as in Figure 4. 100 pseudotrials for each of 4-fold cross validation folds used for all analyses.
Plotting conventions are the same as in Extended Data 9. 100 pseudotrials for each of 2-fold cross validation folds used for all analyses.
Supplementary Math Note, Supplementary Table and Supplementary Figs. 1–3.
Latent trajectories in motion subspace for monkey A.
jPCA projection and angle of rotation for trajectories in motion subspace of monkey A.
Latent trajectories in color subspace for monkey A.
jPCA projection and angle of rotation for trajectories in color subspace of monkey A.
Latent trajectories in choice subspace for monkey A.
jPCA projection and angle of rotation for trajectories in choice subspace of monkey A.
Latent trajectories in context subspace for monkey A.
jPCA projection and angle of rotation for trajectories in context subspace of monkey A.
Latent trajectories in motion subspace for monkey F.
jPCA projection and angle of rotation for trajectories in motion subspace of monkey F.
Latent trajectories in color subspace for monkey F.
jPCA projection and angle of rotation for trajectories in color subspace of monkey F.
Latent trajectories in choice subspace for monkey F.
jPCA projection and angle of rotation for trajectories in choice subspace of monkey F.
Latent trajectories in context subspace for monkey F.
jPCA projection and angle of rotation for trajectories in context subspace of monkey F.
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Aoi, M.C., Mante, V. & Pillow, J.W. Prefrontal cortex exhibits multidimensional dynamic encoding during decision-making. Nat Neurosci (2020). https://doi.org/10.1038/s41593-020-0696-5