Brain activations for the main effect of faces.

<p>Brain activations for the main effect of faces.</p

Divergences for face and word processing.

<p>Divergences for face and word processing.</p

Projections of the gradient vectors on the X, Y and Z axes for face processing.

<p>Positive projections are indicated in red and negative projections in blue (p(uncor)<0.001 for illustration purposes).</p

Illustration of divergence and gradients in a single brain slice of one subject during face processing.

<p>(A) The levels of divergence in a brain slice as coded by the white-black scale. (B) Each voxel in the slice is presented by an arrow – the direction of the arrow reflects the direction of the fastest change of the signal, the size of the arrow reflects the size of this change. These arrows are gradient vectors in each voxel. (C) The magnified part of B. where gradient vectors diverge. (D) The magnified part of B. where gradient vectors converge.</p

Projections of the gradients for face processing, X axis.

<p>Clusters are ranged in the direction of the <i>increase</i> of the X coordinate for the positive projections and of the <i>decrease</i> of the X coordinate for the negative projections of the gradient (the corresponding columns highlighted).</p

Projections of the gradients for face processing, Z axis.

<p>Clusters are ranged in the direction of the <i>increase</i> of the Z coordinate for the positive projections and of the <i>decrease</i> of the Z coordinate for the negative projections of the gradient (the corresponding columns highlighted).</p

Orientation tuning with different contrasts in mixed and constant contrast blocks, additional examples.

<p>Symbols represent the mean firing rate for each orientation and contrast, and the lines correspond to the von Mises (A, B, E, F) or Gauss (C, D) equations fitted to the orientation-response data. Inset shows fitted lines normalized to the same preferred orientation and to the same height, to facilitate comparison of tuning widths. A. For this cell, contrast, in the mixed contrasts condition, had little effect on orientation tuning width, although response amplitude depended strongly on contrast. Contrasts were 11.3, 16 and 22.6%. HWHH were 20.1, 21.1 and 21.9 deg for low, medium and high contrasts, respectively. B. For the same cell, orientation tuning width was also little affected by contrast in the constant contrast blocks. HWHH were 19.3, 20.2 and 22.4 deg for low, medium and high contrasts, respectively. C. This cell showed, in the mixed contrasts condition, reduced tuning width with low contrast stimuli compared to high or medium contrast stimuli. Contrasts were 22.6, 32 and 64%. HWHH were 20.7, 29.2 and 31.2 deg for low, medium and high contrasts, respectively. D. After matched adaptation (constant contrast), the range of HWHH appears to be less wide. HWHH were 26.7, 28.7 and 32.1 deg for low, medium and high contrasts, respectively. E. No significant response was obtained in this cell with low contrast stimuli (35%) in the mixed contrasts block. The tuning curve obtained with high contrast (90%) was broader (HWHH: 20.9 deg) than the tuning curve obtained with medium contrast (50%, HWHH: 13.2 deg). F. Despite adaptation to matched contrasts, the same cell shows differences in HWHH between low (11.6 deg), medium (16.6 deg) and high (20.85 deg) contrasts.</p

Percent change in orientation tuning width vs. percent change in tuned response amplitude.

<p>In these scatter plots, the <i>x</i>-axis represents percent change in tuned response amplitude and the <i>y</i>-axis represents percent change in HWHH. A. Medium vs. high contrast, mixed contrasts condition. B. Low vs. high contrast, mixed contrasts condition. C. Low vs. medium contrast, mixed contrasts condition. In these three scatter plots, most data points are located in the quadrant delimited by 0 and 100% on both x and y axis, indicating that most cells showed both reduced response amplitude and reduced HWHH when contrast was decreased. However, the two variables were not significantly correlated. D. Medium vs. high contrast, constant contrast condition. E. Low vs. high contrast, constant contrast condition. F. Low vs. medium contrast, constant contrast condition. In the scatter plots in E and F, most data points can be found in the quadrant delimited by 0 and 100% on both x and y axes, indicating that most cells showed both reduced response amplitude and reduced HWHH when contrast was decreased. This is not the case for the scatter plot in D, reflecting the fact that orientation tuning width was not different, on average, between medium and high contrast after adaptation. There is, however, a significant inverse relationship between the two variables in this case. The line corresponds to the linear relationship between the two variables.</p

Projections of the gradients for face processing, Y axis.

<p>Clusters are ranged in the direction of the <i>increase</i> of the Y coordinate for the positive projections and of the <i>decrease</i> of the Y coordinate for the negative projections of the gradient (the corresponding columns highlighted).</p

The left-right and top-down projections of the gradients, the intensity of projections coded by colours.

<p>The following direction of energy flows in the frontal cortex is detected: the right inferior frontal = >the left inferior frontal = >the triangular part of the left inferior frontal cortex = >the left operculum. The whole range of t-values is used for illustration purposes.</p