Figure 1.
The figure shows two exemplary experimental trials (A, B) and the factorial nature of the design (C). (A) illustrates the laughter type categorization task (CAT) where the participants had to decide which type of laughter they heard: the trial starts with the presentation of a laughter sequence (here: joyful laughter, JOY) followed by a response scale with the three laughter type categories (“Freude” = JOY; “Kitzel” = tickling laughter, TIC; “Hohn” = taunting laughter, TAU) and a variable inter-trial interval. (B) exemplifies the laughter bout counting task (COU) where the participants had to decide of how many laughter bouts the laughter sequence consisted: the laughter sequence (here: TIC) is followed by a response scale with three response categories (“3″, “4″, “W” = any other number of laughter bouts) and the inter-trial interval. Durations on the time axis indicate durations of the stimulus presentation, response window and inter-trial interval. (C) Experimental design: an equal number (n = 20) of JOY, TAU and TIC stimuli are each presented under two task conditions (CAT, COU) leading to total number of 120 trials within an orthogonal factorial design.
Figure 2.
Laughter type- and task-dependent cerebral responses defining ROIs for connectivity analyses.
Increased responses to complex social laughter types (CSL>TIC, red), to tickling laughter (TIC>CSL, green) and during explicit processing of social information of laughter (CAT>COU, blue) (p<0.001, uncorrected, cluster size k≥55 (CSL vs. TIC) and k≥54 (CAT vs. COU), corresponding to p<0.05, FWE corrected at cluster level). Panels depict mean contrast estimates extracted from activated regions. Please note that displayed effects are relative contrasts and do not correspond to general hemodynamic activations or deactivations. Asterisks mark significant interactions (p<0.05) between laughter type (CSL/TIC) and task (CAT/COU). Activations are rendered on an MNI standard brain.
Table 1.
Differential hemodynamic activation following the perception of complex social laughter types (CSL) and tickling laughter (TIC) and stronger hemodynamic activation following explicit evaluation of laughter type.
Figure 3.
Connectivity modulations within the laughter perception network through complex social laughter types and tickling laughter.
Brain regions with significantly increased responses to CSL (CSL>TIC; red areas/dots), to tickling laughter (TIC>CSL; green areas/dots) and during explicit processing of social information of laughter (CAT>COU; blue areas/dots) as well as regions with equal activation under all experimental conditions (mauve areas/dots) are shown in schematic form (A, C) and superimposed on a three dimensional rendering of five transversal slices of the subjects’ mean anatomic image (B). Increased connectivity during perception of CSL (CSL>TIC; red lines; A and B), and during TIC perception (TIC>CSL; green lines; B and C). Continuous lines: modulations of connectivity which survive correction for multiple comparisons within the target ROI and additional Bonferroni-correction for the number of investigated connections (300). Broken lines: modulations which survive correction for multiple comparisons within the target ROI but not Bonferroni-correction and for which the activated portion of the target ROI is part of a significant target cluster of the whole-brain analysis. Z coordinates refer to the MNI-system. The size of the dots symbolizing the separate ROIs is scaled according to the number of Bonferroni-corrected significant modulations of connectivity of the respective ROI.
Figure 4.
Differences in connectivity within the laughter perception network during perception of joyful (JOY) and taunting (TAU) laughter.
Brain regions with significantly increased responses to CSL (CSL>TIC; red areas/dots), to TIC (TIC>CSL; green areas/dots) and during explicit processing of social information of laughter (CAT>COU; blue areas/dots) as well as regions with equal activation under all experimental conditions (mauve areas/dots) are shown in schematic form (A) and superimposed on a three dimensional rendering of three transversal slices of the subjects’ mean anatomic image (B). Increased connectivity during perception of joyful laughter (JOY>TAU; orange-brown lines; A, B), and during taunting laughter perception (TAU>JOY; dark brown lines; A, B). Continuous lines: modulations of connectivity which survive correction for multiple comparisons within the target ROI and additional Bonferroni-correction for the number of investigated connections (300). Broken lines: modulations which survive correction for multiple comparisons within the target ROI but not Bonferroni-correction; additionally, the activated portion of the target ROI is part of a significant target cluster of the whole-brain analysis. Z coordinates refer to the MNI-system.
Table 2.
Regions with common hemodynamic activation for complex social laughter types (CSL) and reflex-like tickling laughter (TIC) during explicit evaluation of laughter type and laughter bout counting which did not show any differential hemodynamic activation between different laughter types or task conditions.