Intracranial study in humans: Neural spectral changes during watching comedy movie of Charlie Chaplin.

Humor plays a prominent role in our lives. Thus, understanding the cognitive and neural mechanisms of humor is particularly important. Previous studies that investigated neural substrates of humor used functional MRI and to a lesser extent EEG. In the present study, we conducted intracranial recording in human patients, enabling us to obtain the signal with high temporal precision from within specific brain locations. Our analysis focused on the temporal lobe and the surrounding areas, the temporal lobe was most densely covered in our recording. Thirteen patients watched a fragment of a Charlie Chaplin movie. An independent group of healthy participants rated the same movie fragment, helping us to identify the most funny and the least funny frames of the movie. We compared neural activity occurring during the most funny and least funny frames across frequencies in the range of 1-170 Hz. The most funny compared to least funny parts of the movie were associated with activity modulation in the broadband high-gamma (70-170 Hz; mostly activation) and to a lesser extent gamma band (40-69Hz; activation) and low frequencies (1-12 Hz, delta, theta, alpha bands; mostly deactivation). With regard to regional specificity, we found three types of brain areas: (I) temporal pole, middle and inferior temporal gyrus (both anterior and posterior) in which there was both activation in the high-gamma/gamma bands and deactivation in low frequencies; (II) ventral part of the temporal lobe such as the fusiform gyrus, in which there was mostly deactivation the low frequencies; (III) posterior temporal cortex and its environment, such as the middle occipital and the temporo-parietal junction, in which there was activation in the high-gamma/gamma band. Overall, our results suggest that humor appreciation might be achieved by neural activity across the frequency spectrum.

Cognitive dissonance resolution depends on executive functions and frontal lobe integrity.

The free choice paradigm constitutes one of the most explored paradigms of cognitive dissonance research. Typically, once asked to choose between two similarly rated items, subjects subsequently exhibit an increased preference for chosen items and a decreased preference for rejected ones. Recent studies have demonstrated that such choice-induced preference change (CIPC) occur exclusively for remembered choices, suggesting a mechanism that ensures subjective coherence across time. In the present work we predicted that in order for CIPC to occur, not only must past choices be remembered, but executive networks responsible for detecting and solving conflicts must also be functioning. We confirmed this prediction in a group of patients with frontal lobe lesions. While non-dysexecutive (NODYS) patients behaved as their matched controls did, dysexecutive (DYS) patients failed to change their subjective preferences even when they could remember their previous choices. We have therefore demonstrated the crucial role of executive functions mediated by the frontal lobe in cognitive dissonance resolution.