Opioid Analgesia Impacts on Neurological Development (OPAL)

In the orthopaedic clinic Parents of children aged 7-12 years will be screened for the study from the usual care team provided with a participant information sheet and invitation letter. Potential participants will be approached by a member of the research team at a subsequent follow up appointment for recruitment into the study. All participants will provide informed consent signed by the parent or guardian in the clinic room upon recruitment by a member of the research staff. Children (aged 7-12) will sign to confirm assent. Parents/guardians will be given a form to fill in their contact details, and a validated age appropriate questionnaire to complete before the study appointment. [The Multisensory Amplification Scale (Dan Wang and Megan Loux, 2022) will asses the participants sensory processing. The Revised Child Anxiety and Depression Scale (RCADS) (Chorpita et al., 2005) will assess the participants' anxiety and depression.]

At home An appointment letter will be emailed or posted to the participants, in line with their preferred contact method. A reminder text message will be sent a few days prior to their appointment. Participants will have a study appointment arranged on the same day as their follow-up appointment to orthopaedics or at an alternative convenient time. The participants will complete the questionnaire with the help of their parent/guardian at home before the study appointment. This will take roughly 20-30 minutes, including schedules breaks.

Study appointment At the research visit, children will attend the Sir Peter Mansfield Imaging Centre (SPMIC) at the University of Nottingham for an appointment 1-1.5 hours (allows for technical difficulties). The OPM-MEG is integrated into a helmet (effectively a modified bicycle helmet). The child will wear this helmet throughout the scanning session, and this will allow the passive measurement of MEG data.

We will use OPM-MEG to record brain activity during rest (tactile-free) and in response to a tactile and visual stimuli.

The tactile attention task involves brief, gentle stimulation to the index fingers using braille-style devices while the participant watches a video of their choice. Stimulation is delivered using a set of custom-built braille cells mounted on a wooden platform, allowing for comfortable and stable hand placement. A single trial comprised approximately 0.5s of stimulation during which the finger is tapped 3 times using all 8 pins. Pins are up for 82ms during each 'tap' and down for 82ms between 'taps'). This is followed by 3 s rest. The finger stimulates the index finger. There is a total of 42 trials for each finger, meaning the experiment lasts a total of 294 seconds (5 minutes).

The visual stimulation to measure gamma activity comprises of an inwardly moving circular grating moving at 1.2°s-1. The grating is displayed centrally at 100% contrast and subtended a visual angle of 7.6°, with 1.32 cycles per degree. A single trial comprises 1000 ms of stimulation followed by a jittered rest period with a white fixation cross located centrally on a black screen for 1250 ± 200 ms. Sixty trials in total are shown and these circles trials are interspersed with images of faces. The total time for this task is roughly 5 minutes.

All devices have been safety tested for use with human volunteers and pose no risk to the participants, and are well tolerated. At all times the child's parent/guardian will remain in the study room with them. The experimenter and parent/guardian can communicate via an intercom set-up, ensuring the comfort of the child and parent throughout the study. Participants will also be continuously monitored on a video camera within the scanning suite. If the child becomes distressed at any point the study will be stopped, and only restarted if both the parent/guardian and their child are happy. The child will also be able to watch a TV program/film during the study to ensure that they remain comfortable.

A typical recording session will last approximately 40 minutes allowing for technical difficulties. It will consist of:

• Two 5 minute recording blocks and one 5-10 minute resting state recording block. The participant will be watching a standardised video on screen for both tasks and resting state recording.
• We will need to record the shape of the child's head- this will be done using an Einscan. This creates a 3D image of the head with, and without the helmet on to accurately record the locations of the sensors on the scalp.