Article Figures & Data
Figures
- Figure 1.
Areas of the superior parietal lobule in a macaque brain. Posterolateral view of a part of M. fascicularis brain showing location and extent of areas V6A, PEc, and PE (outlined by gray dashed lines) of the SPL. The right hemisphere is partially dissected to show the areas hidden in the parieto-occipital and intraparietal sulci. Colored areas represent the reconstructions of the recording regions within these areas as a mean of two animals and four hemispheres. cal, calcarine sulcus; cgs, cingulate sulcus; cs, central sulcus; ios, inferior occipital sulcus; ips, intraparietal sulcus; ls, lunate sulcus; ots, occipitotemporal sulcus; pos, parieto-occipital sulcus; sts, superior temporal sulcus (modified from Gamberini et al., 2020).
- Figure 2.
Scheme of the experimental setup and timing of the task. The monkey sat in a primate chair in front of a horizontal panel located at eye level with nine LEDs used both as fixation and reaching targets. HB, home button. The distances in depth between the three targets of the central row from mid-eye level are shown. The time sequence of task events shows LED status, the eye’s vergence and version traces, arm status, and HB status. From left to right, vertical lines indicate, respectively, trial start (HB press, black line), target appearance (LEDon, green line), fixation onset (end of saccade movement, dashed line), go signal (Go, red line), arm movement onset (M, blue line), holding phase of the target (H, orange line), turning off of the LED (LEDoff, purple line), and trial end (HB press, gray line). Arm drawings indicate the forward and backward arm movement. The relevant time intervals (epochs) used for the analysis of neural activity are indicated with gray areas and white bars below the time axis: FIX = fixation epoch, HOLD = holding epoch.
- Figure 3.
Example V6A neuron tuned by eye/arm positions both in FIX and HOLD. Left, Spike histograms (top), rasters (middle), eye traces (bottom) are shown for each of the nine target positions tested. Target positions were arranged in three directions (columns; contralateral, central, ipsilateral with respect to the recording hemisphere) and three depths (rows; far, intermediate, near with respect to the monkey’s body). Colored vertical lines along rasters indicate behavioral markers that, from left to right, are: LED illumination, fixation onset, go signal, movement onset, movement end (LED pressing), target offset, backward movement onset. Thin vertical lines along spike histograms indicate the alignment of activity at the fixation onset and LED pressing, respectively. Realignment is evidenced with a gap in histograms. Epochs of interest are represented within gray rectangles. Vertical scale on histograms: 40 spikes/s. Right, Distribution of the mean activity of the same cell across trials during epochs FIX (top) and HOLD (bottom) for each of the nine target positions tested. Asterisks indicate the spatial position evoking the highest discharge in each epoch.
- Figure 4.
Example PEc neuron tuned by eye/arm positions both in FIX and HOLD. All the conventions as in Figure 3. Vertical scale on histograms: 70 spikes/s.
- Figure 5.
Example PE neuron tuned by eye/arm positions only in HOLD. All the conventions as in Figure 3. Vertical scale on histograms: 48 spikes/s.
- Figure 6.
Significant effects modulating V6A, PEc, and PE cells. A, The histograms show the results of a two-way ANOVA as the incidence of cells modulated by the fixation and arm holding in space (EPO: epoch) and the nine spatial positions in one or both the epochs of interest (POS: target positions), or by the interaction of the two factors (INT: target positions*epoch). Numbers of modulated cells for each subgroup of task-related cells: POS+EPO, V6A N = 157, PEc = 126, PE = 52; INT+EPO, V6A N = 12, PEc = 18, PE = 19; INT+POS, V6A N = 47, PEc = 36, PE = 8; INT, V6A N = 10, PEc = 8, PE = 6 (cells with no effect, V6A N = 27, PEc = 22, PE = 36 not shown in figure). B, Percentages of cells tuned by the position of the reaching target in FIX, HOLD, and FIX&HOLD, as a result of a one-way ANOVA.
- Figure 7.
Space representation in the three SPL areas along the task. Percentage of V6A (top), PEc (middle), and PE (bottom) task-related cells linearly modulated by depth (left) and direction (right) showing a preference for far (FAR, purple line) or near (NEAR, pink line) space and ipsilateral (IPSI, black line) or contralateral (CONTRA, light blue line) space with respect to the recording hemisphere in a sliding window linear regression (window-bin width: 250 ms; step: 50 ms). Asterisks indicate significant differences between curves in bins of 250 ms (two-sample Kolmogorov–Smirnov test, p < 0.01). Other conventions as in Figure 3.
- Figure 8.
Population activity. Population activity of V6A (top), PEc (middle), and PE (bottom) cells modulated by the position of reaching target during FIX and/or HOLD, expressed as averaged normalized SDFs (thick lines) with variability bands (SEM; thin lines). A, SDFs obtained by ranking the activity of each neuron according to the intensity of the response for each spatial position elicited in FIX for that neuron. B, SDFs obtained ranking the activity of each neuron according to the intensity of the response for each spatial position elicited in HOLD. Neuronal activities have been aligned twice at the onset of fixation and at LED pressing. Vertical bars in all SDF plots: 100% of normalized activity. Permutation test was performed on BEST (blue line) and WORST (red line) curves in all the time intervals shown. At the top of each panel, black bars are used to indicate the significancy (see legend).
In this issue
