Article Figures & Data
Figures
- Figure 1.
Schematic of orientation change detection task. Valid–invalid block (left panel), The task began with the appearance of a central fixation spot. Attention was cued in blocks using an initial set of “instruction trials” where the monkeys were explicitly cued to attend to a location (cued left in the depiction) by briefly flashing a white dot for 50–100 ms which indicated the target location with 100% certainty in the instruction trial and most likely location for rest of the block. Two Gabor stimuli counterphasing at 10 Hz appeared simultaneously and synchronously on the screen. At an unsignalled time between 500 and 5,500 ms after the stimulus onset, one of the Gabor stimuli changed its orientation (target), and the monkey was rewarded if it made a saccade to the location of orientation change between 100 and 550 ms after the target onset. The target appeared at the cued location with an 80% probability (valid cue) and at an uncued location with a 20% probability (invalid cue). Monkeys were rewarded for detecting the target at either of the locations. Once the monkeys performed four instruction trials correctly, then the explicit cue was no longer presented, and the target appeared probabilistically. Neutral block (right panel), Unlike the valid–invalid block, in the neutral block, the monkeys were cued by briefly flashing the white spot at both locations simultaneously during the instruction trials, and the target could occur at either of the two locations with 50% probability. The rest of the task structure is the same as that of the valid–invalid block.
- Figure 2.
Comparison of firing rate (FR) and local field potential (LFP) power across validly cued attention and behavioral conditions for matched target onset time distributions. A, Mean peristimulus time histogram (PSTH) relative to the target-onset time for the conditions in which attention was validly cued into or outside the receptive field of a neuron and the subject either detected (hit) or missed the target, namely, Attend-In Valid Hit (AIVH; blue), Attend-Out Valid Hit (AOVH; red), Attend-in Valid Miss (AIVM; cyan), and Attend-Out Valid Miss (AOVM; magenta). Inset shows the mean firing rate over the same time period as PSTH for the four conditions. The mean is first taken across 643 electrodes recorded across 21 sessions in two monkeys and then averaged across 50 bootstrap iterations of target-onset time-matched trial selection. The shaded lines and error bars indicate the bootstrap mean of SEM across the 643 electrodes. Only sessions in which at least 10 stimulus repeats were available for every condition were used for analysis. The asterisk in the inset indicates that the mean firing rate of AIVH is significantly higher than AOVH (Wilcoxon rank-sum test; Bonferroni corrected p < 0.05). B, Mean event-related potential (ERP) for the four conditions. The horizontal black patches at the bottom indicate the time values during which the ERP of AIVH and AIVM were significantly different (Wilcoxon rank-sum test; Benjamini–Hochberg FDR controlled p < 0.05), and the gray patches indicate the time values during which ERP of AOVH and AOVM were significantly different (Wilcoxon rank-sum test; Benjamini–Hochberg FDR controlled p < 0.05). C, Mean change in power spectral density (PSD) in decibels for all the validly cued conditions relative to the Attend-out Valid Hit (AOVH) condition. The horizontal blue, cyan, and magenta patches at the bottom indicate the frequencies at which the change in PSD relative to the AOVH condition is significantly different from zero of the conditions represented by their corresponding color (Wilcoxon signed-rank test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). The black horizontal patches indicate the frequencies at which the change in PSD of AIVH (blue trace) and AIVM (cyan trace) are significantly different from each other (Wilcoxon rank-sum test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). D, Mean change in LFP power spectral density (PSD) in decibels between attend-in and attend-out conditions for hit (AIVH and AOVH; green) and miss (AIVM and AOVM; yellow) conditions. The horizontal dashed black line marks the zero of the y-axis. The horizontal green and yellow patches at the bottom indicate the frequencies at which the change in PSD between attention conditions are significantly greater than zero for hits and miss conditions, respectively (Wilcoxon signed-rank test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). The horizontal black patch at the bottom indicates the frequencies at which the change in PSD between attention conditions for hit and miss conditions are significantly different from each other (Wilcoxon rank-sum test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). E, Mean change in power spectral density between hit and miss conditions for Attend-In (AIVH and AIVM; blue) and Attend-Out (AOVH and AOVM; red) conditions. The horizontal dashed black line marks the zero of the y-axis. The horizontal blue and red patches at the bottom indicate the frequencies at which the change in PSD between behavioral conditions are significantly greater than zero for attend-in and attend-out conditions, respectively (Wilcoxon signed-rank test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). The horizontal black patch at the bottom indicates the frequencies at which the change in PSD between behavioral conditions for attend-in and attend-out condition are significantly different from each other (Wilcoxon rank-sum test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). F, Mean d′ (the ratio of the mean difference and pooled standard deviation of two conditions) of LFP power (solid lines) and firing rate (dashed color lines) between attend-in and attend-out conditions for hit (green) and miss (yellow) conditions. The horizontal dashed black line marks the zero of the y-axis. The horizontal green and yellow patches at the bottom indicate the frequencies at which the d′ of LFP power is significantly different from the d′ of firing rate for hit and miss conditions, respectively (Wilcoxon rank-sum test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). Negative d′ values were multiplied by −1 before performing the significance test because we were interested in the differences in magnitude of d′. G, Mean d′ of LFP power (solid lines) and firing rate (dashed color lines) between hit and miss conditions for Attend-In (blue) and Attend-out (red) conditions. The horizontal dashed black line marks the zero of the y-axis. The horizontal blue and red patches at the bottom indicate the frequencies at which the d′ of LFP power is significantly different from the d′ of firing rate for attend-in and attend-out conditions, respectively (Wilcoxon rank-sum test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). Negative d′ values were multiplied by −1 before performing the significance test as in F. H, Mean d′ of LFP power between attend-in and attend-out conditions for hit condition where LFP power is estimated by multitaper method using time–frequency bandwidth product (TW) of 1 (darkest green), 3 (dark green), 5 (light green), and 10 (lightest green). The dashed green line indicates the d′ of firing rate between the same conditions. The horizontal dashed black line marks the zero of the y-axis. The horizontal colored patches at the bottom indicate the frequencies at which the d′ of LFP power estimated using different TW is significantly different from the d′ of firing rate (Wilcoxon rank-sum test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). Negative d′ values were multiplied by −1 before performing the significance test as in G and F. A similar comparison of the firing rate and LFP power for valid conditions before matching the target-onset time distribution and for neutral conditions after matching the distributions are shown in Extended Data Figure 2-1.
- Figure 3.
Comparison of LFP phase and pairwise phase consistency of individual electrodes and trial-wise firing rate correlation, LFP power correlation, and pairwise phase consistency (PPC) of electrode pairs across validly cued attention and behavioral conditions. A, Mean sine of the LFP phase angle for Attend-In Valid Hit (AIVH; blue), Attend-Out Valid Hit (AOVH; red), Attend-In Valid Miss (AIVM; cyan), and Attend-Out Valid Miss (AOVM; magenta) conditions. B, Mean d′ of firing rate (dashed color lines) and sine of the LFP phase angle (solid lines) between attend-in and attend-out conditions for hit (green) and miss (yellow) conditions. The horizontal dashed black line marks the zero of the y-axis. The horizontal green and yellow patches at the bottom indicate the frequencies at which the d′ of LFP phase angle for hit and miss conditions, respectively, are significantly greater than zero (Wilcoxon signed-rank test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). The horizontal black and gray patches at the bottom indicate the frequencies at which the d′ of the LFP phase angle is significantly different from the d′ of firing rate for hit and miss condition, respectively (Wilcoxon rank-sum test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). Negative d′ values were multiplied by −1 before performing the significance test. C, Mean d′ of firing rate (dashed color lines) and sine of the LFP phase angle (solid lines) between hit and miss conditions for attend-in (blue) and attend-out (red) conditions. The horizontal dashed black line marks the zero of the y-axis. The horizontal blue and red patches at the bottom indicate the frequencies at which the d′ of LFP phase angle for attend-in and attend-out condition, respectively, are significantly greater than zero (Wilcoxon signed-rank test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). The horizontal gray patches at the bottom indicate the frequencies at which the d′ of the LFP phase angle is significantly different from the d′ of firing rate for attend-out condition. (Wilcoxon rank-sum test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). Note that the difference between d′ for the LFP phase angle and firing rate for attend-in condition was not significant at any frequency (Wilcoxon rank-sum test, Benjamini–Yekutieli procedure for FDR control under unknown dependency); hence, no patch is shown for that comparison. Negative d′ values were multiplied by −1 before performing the significance test. D, Mean single-electrode pairwise phase consistency (PPC; see Materials and Methods for details) for the four conditions as in A. E, Mean change in single-electrode PPC between attend-in and attend-out conditions for hit (green) and miss condition (yellow). The horizontal dashed black line marks the zero of the y-axis. The horizontal green and yellow patches at the bottom indicate the frequencies at which the change in PPC for hit and miss condition, respectively, is significantly greater than zero (Wilcoxon signed-rank test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). F, Mean change in single-electrode PPC between hit and miss conditions for attend-in (blue) and attend-out condition (red). The horizontal dashed black line marks the zero of the y-axis. The horizontal blue and red patches at the bottom indicate the frequencies at which the change in PPC for attend-in and attend-out conditions, respectively, are significantly greater than zero (Wilcoxon signed-rank test, Benjamini–Yekutieli FDR controlled p < 0.05 under unknown dependency). In A–F, mean and SEM are computed like in Figure 2A,G. G, Mean change in trial-wise firing rate correlations for the four conditions relative to the Attend-Out Valid Hit (AOVH) condition. The dashed black line indicates the zero of the y-axis. The asterisks indicate the conditions between which the differences in trial-wise correlation are significant (Wilcoxon rank-sum test; Bonferroni corrected p < 0.05) between the conditions. H, Mean change in trial-wise LFP correlations (solid lines) and firing rate correlation (dashed color lines) between attend-in condition and attend-out condition for hit (green) and miss trials (yellow). The dashed black line indicates the zero of the y-axis. I, Mean change in trial-wise LFP correlation (solid lines) and firing rate correlation (dashed color lines) between hit condition and miss condition for validly cued attend-in (blue) and attend-out (red) conditions. The dashed black line indicates the zero of the y-axis. J, Mean pairwise phase consistency (PPC) across trials for the four conditions as in (A). K, L, Same as E and F but for pairwise phase consistency (PPC) across trials. In G–L, the mean was taken across 50 bootstrap samples of mean across 5,754 pairs, and the shaded lines and error bar indicate the bootstrap mean of SEM across 5,754 electrode pairs. In H, I, K, and L, the significance lines shown at the bottom are calculated using the same approach as B, C, E, and F. A similar comparison of single-electrode phase measures, trial-wise correlations, and PPC for neutrally cued condition is shown in Extended Data Figure 3-1.
- Figure 4.
Illustration of methods used for estimating correlation and pairwise phase consistency within a trial. Binning method (left panel), A single-trial LFP signal of 500 ms duration from two electrodes is first divided into 10 nonoverlapping bins of 50 ms each. Then, the power and phase of each 50 ms LFP segment of the two electrodes were estimated by Fourier transform. Subsequently, we estimated the power correlation and pairwise phase consistency across the ten bins between the pair of electrodes at each frequency between 0 and 200 Hz with 20 Hz resolution. Similarly, the spikes from the two electrodes were also binned and firing rate correlations between the two electrodes were computed across bins (bottom left panel). These correlations were subsequently shuffle corrected (see Materials and Methods). Multitaper method (right panel), We used an alternate method to obtain multiple estimates of power and phase using the multitaper method. LFP signal of 500 ms duration of two electrodes was first multiplied by nine orthogonal Slepian tapers of the same length, and then power and phase of these nine tapered LFP signals were obtained by Fourier transform. Power correlation and PPC were calculated between electrode pairs across tapers at frequencies between 0 and 200 Hz with 2 Hz resolution. The black dot in the PPC vs frequency and correlation versus frequency plots indicates the frequency whose amplitude and phase are shown in the polar plot in the top panel and whose power scatter plot is shown.
- Figure 5.
Comparison of single-trial bin-wise firing rate correlation, bin-wise and taper-wise LFP power correlation, and pairwise phase consistency (PPC) across validly cued attention and behavioral conditions. A, Mean change in single-trial bin-wise LFP power correlation (solid lines) and firing rate correlation (dashed color lines) between validly cued attend-in and attend-out conditions for hit (green) and miss (yellow) conditions. Single-trial bin-wise correlation was measured by dividing the analysis period of 500 ms into 10 nonoverlapping bins and measuring the firing rate or power correlation across bins. Since power was estimated for signals of 50 ms duration, the frequency resolution is 20 Hz. The dashed black line indicates the zero of the y-axis. B, Mean d′ of bin-wise LFP power correlation (solid lines) and firing rate correlation (dashed color lines) between validly cued attend-in and attend-out conditions for hit (green) and miss (yellow) conditions. The dashed black line indicates the zero of the y-axis. C, Mean change in bin-wise LFP power correlation (solid lines) and firing rate correlation (dashed color lines) between hit and miss conditions for validly cued attend-in (blue) and attend-out (red) conditions. The dashed black line indicates the zero of the y-axis. D, Mean d′ of bin-wise LFP power correlation (solid lines) and firing rate correlation (dashed color lines) between hit and miss conditions for validly cued attend-in (blue) and attend-out (red) conditions. The dashed black line indicates the zero of the y-axis. E–H, Same as A–D but for single-trial bin-wise PPC. Single-trial bin-wise PPC was computed across the same 10 nonoverlapping bins used to compute power correlations. In A–H, the colored patches at the bottom indicate significance like that in Figure 3, but here the FDR was controlled using the Benjamini–Hochberg procedure. I–P, Same as A–H but for single-trial taper-wise power correlation and PPC. Here power correlation and PPC are computed by using the multitaper method. Specifically, we use TW = 5 to get 9 (2TW-1) estimates of power and phase values per trial and compute the power correlation or PPC between electrode pairs across these nine values. Unlike A–H, FDR was controlled by using the Benjamini–Yekutieli procedure under unknown dependency. In A–P, the mean was taken across 50 bootstrap samples of mean across 5,754 pairs and shaded lines indicate the bootstrap mean of SEM across 5,754 electrode pairs. A similar comparison of single-trial measures for neutrally cued condition computed using the binning method and multitaper method are shown in Extended Data Figure 5-1 and those computed using the Hilbert transform method for valid and neutral conditions are shown in Extended Data Figure 5-2.
- Figure 6.
Summary plot comparing across the d′ values of all the measures for spikes, LFP power, and phase in different frequency bands for validly cued attention and behavioral comparison. A, d′ of firing rate/LFP power (red), sine of the phase angle (blue), firing rate/LFP power correlation across the bins (green), LFP power correlation across the tapers (magenta), pairwise phase consistency (PPC) across bins (brown), and PPC across tapers (purple) for spikes, alpha (8–12 Hz), SSVEP (18–22 Hz), gamma (40–80 Hz), and high-gamma (120–200 Hz) power between attend-in and attend-out conditions for hit trials. Note that for spikes, only d′ values of firing rate and bin-wise correlation exist because the rest of the measures cannot be computed for the spike data whereas for alpha-band, d′ of bin-wise measures (CorrelationBin and PPCBin) are absent because the frequency resolution in the binning method was 20 Hz. “***” indicates p-value < 0.001, “**” indicates 0.001 < p-values < 0.01, “*” indicates the 0.01 < p-values < 0.05, and no asterisks are shown for p-values > 0.05. Negative d′ values were converted to positive values by multiplying with −1 before performing the significance test since we were comparing only the magnitude. All the p-values are Bonferroni corrected for multiple comparisons. B, Same as A but for the d′ between the hit and miss conditions of the attend-in condition. A summary plot comparing the d′ values of all the measures for neutrally cued condition is shown in Extended Data Figure 6-1.
Extended Data
Figure 2-1
Comparison of firing rate (FR) and local field potential (LFP) power across (1) validly cued attention and behavioral conditions for non-matched target onset time distributions and (2) neutrally cued attention and behavioral conditions for matched target onset time distributions. (A) – (G) Same as Figure 2 (A) – (G) but for the case where the target onset time distributions of hit and miss conditions were not matched. Here the mean is taken across 677 electrodes recorded across 22 sessions in two monkeys. Shaded lines and error bars (not visible for most traces) indicate the s.e.m across the 677 electrodes. (H) Frequency distribution of target onset time for the four validly cued conditions of all the sessions. The number in the brackets indicate total number of trials in the respective conditions. (I) Mean peri-stimulus time histogram (PSTH) relative to the target onset time for the neutrally cued conditions in which attention was cued to both visual hemifields simultaneously and target could appear at either of the location with 50% probability. Unlike the valid cue condition where the conditions were divided based on attention location, here the conditions are divided based on where the target eventually appeared, namely Target-In Neutral Hit (TINH; blue), Target-Out Neutral Hit (TONH; red), Target-In Neutral Miss (TINM; cyan), Target-Out Neutral Miss (TONM; magenta). Inset shows the mean firing rate over the same time period as PSTH for the four conditions. Mean is first taken across 659 electrodes recorded across 21 sessions in two monkeys and then averaged across 50 bootstrap iterations. Shaded lines and error bars indicate the bootstrap mean of s.e.m across the 659 electrodes. (J) Mean ERP for the four conditions described in A. (K) Mean change in power spectral density for all the neutrally cued conditions relative to Target-Out Neutral Hit (TONH) condition. (L) Mean change in LFP power spectral density in decibels between Target-In and Target-Out conditions for hit (TINH and TONH; green) and miss (TINM and TONM; yellow). The horizontal dashed black line marks the zero of the y-axis. (M) Mean change in LFP power spectral density between hit and miss condition for neutrally cued Target-In (TINH and TINM; blue) and Target-Out (TONH and TONM; red) conditions. The horizontal dashed black line indicates the zero of the y-axis. (N) Mean d-prime of LFP power (solid lines) and firing rate (dashed color lines) between neutrally cued attend-in and attend-out conditions for hit (green) and miss (yellow) conditions. The horizontal dashed black line marks the zero of the y-axis. (O) Mean d-prime of LFP power (solid lines) and firing rate (dashed color lines) between hit and miss condition for neutrally cued Target-In (blue) and Target-out (red) conditions. The horizontal dashed black line indicates the zero of the y-axis. (P) Mean d-prime of LFP power between Target-In and Target-Out conditions for hit condition where LFP power is estimated by Multitaper method using time-frequency bandwidth product (TW) of 1 (darkest green), 3 (dark green), 5 (light green) and 10 (lightest green). The dashed green line indicates the d-prime of firing rate between the same conditions. The horizontal dashed black line marks the zero of the y-axis. Asterisks and horizontal color patches at the bottom of each panel indicate the significance level like in Figure 2. Download Figure 2-1, TIF file.
Figure 3-1
Comparison of LFP phase and pairwise phase consistency of individual electrodes and trial-wise firing rate correlation, LFP power correlation and pairwise phase consistency (PPC) of electrode pairs across neutrally cued attention and behavioral conditions. Same as figure 3 but for the neutrally cued conditions. In (A)–(F) mean and s.e.m are computed like in Figure 2-1I – 1O. In (G)-(L) mean was taken across 50 bootstrap samples of mean across 5985 pairs and shaded lines and error bar indicate the bootstrap mean of s.e.m across 5985 electrode pairs. Horizontal color patches at the bottom of each panel indicate the significance level like in Figure 3. Download Figure 3-1, TIF file.
Figure 5-1
Comparison of single trial bin-wise firing rate correlation, bin-wise and taper-wise LFP power correlation and pairwise phase consistency (PPC) across neutrally cued attention and behavioral conditions. Same as figure 5 but for neutrally cued conditions. Mean and s.e.m were computed like in Figure 3-1G – L. Horizontal color patches at the bottom of each panel indicate the significance level like in Figure 5. Download Figure 5-1, TIF file.
Figure 5-2
Comparison of single trial estimates of LFP power correlation and pairwise phase consistency (PPC) computed using Hilbert transform method with bin-wise firing rate correlation across valid and neutrally cued attention and behavioral conditions. (A)-(H) Same as figure 5I - P. Mean was taken across 50 bootstrap samples of mean across 5754 pairs and shaded lines indicate the bootstrap mean of s.e.m across 5754 electrode pairs. Horizontal color patches at the bottom of each panel indicate the significance level like in Figure 5. (I)-(P) Same as figure 5-1I-P. Mean was taken across 50 bootstrap samples of mean across 5985 pairs and shaded lines indicate the bootstrap mean of s.e.m across 5985 electrode pairs. Horizontal color patches at the bottom of each panel indicate the significance level like in (A)-(H). Download Figure 5-2, TIF file.
Figure 6-1
Summary plot comparing across the d-primes of all the measures for spikes, LFP power and phase in different frequency bands for neutrally cued attention and behavioral comparison Same as figure 6 but for neutrally cued condition. Asterisks indicate the significance level like in Figure 6. Download Figure 6-1, TIF file.
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