THE FUNCTIONAL ROLE OF LEFT AND RIGHT INFERIOR FRONTAL GYRUS IN AUDIOMOTOR PROBABILISTIC SEQUENCE LEARNING

The human brain excels at learning probabilistic patterns in our sensory experience. This ability is fundamental for learning across perceptual domains and is a key basis for acquiring language and motor skills. The inferior frontal gyrus (IFG) is important for probabilistic learning in both language and motor domains but seemingly differs in function between hemispheres. Based on findings from each domain, we hypothesise that while the left IFG stores a representation of the probabilistic system, e.g., grammar, the right IFG is responsible for detecting the most likely sensory cue. This preregistered study (http://osf.io/ns89j) uses continuous theta burst transcranial magnetic stimulation to inhibit the left and right IFG in independent groups (25 participants per stimulated group and sham stimulation group) before learning phoneme-key press probabilistic sequences in a two-session design. Each phoneme cued key press can be followed either by a highly (80%) or a less (20%) likely next cue. Preliminary data (N=6) shows smaller response time differences between highly and less likely key press transitions for left (0.172 s) than right IFG-inhibited (0.319 s), and sham-stimulated (0.244 s) participants. Moreover, the left-inhibited participants generate a smaller proportion of the highly likely transitions than the right-inhibited in both the motor (left: 82%; right 89%) and the spoken (left: 73%; right: 82%) generation task. Preliminary results thus indicate functionally different roles for left and right IFG in probabilistic learning partially in line with our hypothesis. Further data collection and analysis will complement these results.