Article Figures & Data
Figures
- Figure 1.
A, The two-target radial choice task. 1, At the start of the trial, the cursor is centered by the computer and one of two targets appears. 2, The monkey then has 5 s to move the cursor to the correct target. 3, Once the cursor touches the outer circle or the maximum movement time has been exceeded, the trial is over, a 1 s intertrial interval occurs, and the monkey is rewarded if the correct target was chosen. B, Electrode placement of epidural μECoG array shown on brain surface of monkey J. The two electrodes (green) used for horizontal control are shown along with the reference electrode (R). The central sulcus (CS), arcuate sulcus (AS), and superior precentral dimple (SPD) are labeled.
- Figure 2.
Epidural μECoG mean control signals and histogram. Data are from a single week (5 d) of recording once bias had been completely turned off with a consecutive block of both 400 correct plus any incorrect trials from each day for a total of 2000+ trials for each monkey–dimension combination. A, Mean control signals between 75 and 105 Hz for monkey M on the electrode over M1 for both leftward (red trace) and rightward (blue trace) movements. The shaded area represents the 95% confidence interval of the mean. After an initial symmetric rise, the amplitude for the left trials continues to rise significantly more to properly control the cursor. B, Histogram showing separation in spectral amplitudes between 75 and 105 Hz for trials of right versus left targets. C, The d′ statistic for each control channel for the six different monkey–dimension combinations was calculated using the separation of the mean amplitudes for the two targets. The more caudal recording electrode is shown on the left for each control pair. Error bars represent 95% confidence intervals. D, Cortical location of control electrodes for all three monkeys. The color coding in C maps directly to the colors in D. The label “S” represents the strongly modulated electrode, while the “W” represents the weaker modulated electrode in the push-pull pair. The central sulcus (CS), arcuate sulcus (AS), and superior precentral dimple (SPD) are labeled.
- Figure 3.
A, d′ as a function of distance from the control electrode. Electrodes are grouped based on distance from a strongly modulated or weakly modulated control electrode as shown in Figure 2c. For the strongly modulated electrodes, the mean d′ values significantly decreased as a function of distance (ANCOVA, p < 0.001) from a mean d′ of 2.40 on the control electrodes to 0.97 on the electrodes 6 mm away. B, Time course of learning as measured by Δd′. The increase in the difference between positive and negative control channel (Δd′) across recording days as the subject adapts to the task. The endpoint (large dot) represents full brain control (no bias). Each point represents the first time that a monkey for a given dimension reached a given Δd′ value.
- Figure 4.
The mean RMS values for each day. A, Increased amplitude targets. B, Decreased amplitude targets compared with baseline RMS at the beginning of the day. The data suggest that increasing the signal amplitude is the active process used by the brain to gain control.
