Trancranial Pulse Stimulation on Anterior Insula Cortex and Dorsal Anterior Cingulate Cortex

The Chinese version of reading the mind in the eyes test (RMET) will be used to assess the AIC function of empathy. In this test, participants will be presented with a series of 28 photographs of the eye region of the face, followed by four mental state terms. Participants will be asked to choose which of four words best describes what the person in the photograph is thinking, feeling, and expressing. The order of trial presentation within each run will be randomized. Participants will be told to complete the task as quickly as possible although they are not timed.

The Balloon Analog Risk Task will be used to assess the AIC function of risky decision-making. Participants have to inflate a virtual balloon that can either grow larger or explode. Each time participants pump up the balloon, they accumulate money, but each pump also carries the risk of the balloon exploding, which results in the participant losing all of their money from that balloon. In the task, participants will be required to complete 30 trials (balloons) with a maximum of 12 pumps. The probability of explosion will be increased with each pump from 2% for the first pump to 90% for the last pump.

The Go/No-go task (GNGT) will be used to assess the AIC and ACC function of response inhibition. The red circles and blue circles will serve as Go and No-go signals, respectively. Each trial will begin with the central fixation cross for a duration of 1000 ms, followed by a Go or No-go stimulus for 400 ms. A total of 100 trials will be randomly presented in two blocks, including high (50%) and low (20%) No-go trials. The participants will be instructed to respond as quickly as possible to the Go signal by pressing the space key on the keyboard with the right index finger and to withhold the response when a No-go signal appears. Before the test task, there will be a practice session with 20 trials. At the end of each trial in the test task, participants will receive feedback for 1000 ms indicating their answer is correct or not.

The counting Stroop task conflict will be used to assess the dACC function of the error monitoring. Participants will be required to report, via key-press, the number of identical words they see on a monitor, regardless of the word's meaning, as quickly and accurately as possible. The alphabets (A, S, K, L) on the keyboard correspond to the number of words (A to 1, S to 2, K to 3, L to 4). In incongruent blocks, the stimuli consisted of Chinese number words such as "一", "二", "三" and "四", while the number of words and meaning will be always inconsistent. During the neutral blocks, Chinese words such as "了", "人", "手", "口" which are irrelevant to the number will be displayed. Both sets of stimuli are common Chinese words with matched visual complexity. Each stimulus will change every 1.5 seconds. The inter-trial interval will be 500 ms. The task consisted of four 48-second blocks of 24 neutral trials alternating with four 48-second blocks of 24 incongruent trials.

Participants will receive a 5-minute structural MRI scan using a Siemens 3T MAGNETOM Prisma system and a 64-channel head coil. The standard scanning parameters will be: TR/TE=2300/2.98 ms, flip angle = 9°, FOV=240x256x208 mm, voxel size=1x1x1 mm. A rs-fMRI scan of 8 minutes will be performed, during which subjects will be instructed to relax with eyes open and gaze at a cross displayed on the screen in front of them, allowing their mind to wander without focusing on anything specific. Rs-fMRI will be performed using a single-shot gradient-recalled EPI with TR/TE=607/32 ms, a FOV of 220x220x160 mm, and a voxel size of 2.5x2.5x2.5 mm with 64 slices (slice thickness = 2.5mm, interleaved series).