Targeted Neuromodulation of Perceptual Decision-Making Networks Causally Dissociates Sensory and Metacognitive performance

Perceptual judgements and their subjective evaluation (i.e., metacognition) are considered tightly coupled aspects of decision-making. Yet, emerging evidence suggests that distinct neural mechanisms underlie these processes. In motion perception, studies have identified a neural network involving visual and associative parietal areas supporting these abilities. Whilst early (V1/V2) and specialized (V5/MT+) visual areas are associated with motion discrimination accuracy, the intraparietal sulcus (IPS/LIP) plays a critical role in the formation of subjective confidence for sensory decision, given its functionally coupling with the V5/MT+-V1/V2 network. Previous studies have consistently reported that increasing connectivity in the human V5/MT+-to-V1/V2 pathway by means of cortico-cortical paired associative stimulation (ccPAS) - a neurostimulation protocol inducing Hebbian-like changes in neuronal pathways - improves our perceptual ability to discriminate motion. Notably, we recently demonstrated that strengthening V5/MT+ influence over V1/V2 also leads to overconfidence - altering metacognitive bias for motion discrimination, suggesting that the manipulation of V5/MT+-V1/V2 network might functionally affect IPS/LIP activity. Here, we directly investigated this possibility by first strengthening the V5/MT+-V1 pathway with ccPAS, and subsequently interfering with IPS/LIP activity by means of continuous theta-burst stimulation (cTBS). In line with previous evidence, our results corroborate that enhancing V5/MT+-V1/V2 connectivity affects both motion discrimination and metacognitive bias. Crucially, IPS/LIP disruption through cTBS selectively affects metacognitive performance while leaving motion discrimination unaltered. These findings highlight distinct neural substrates for perceptual sensitivity and visual metacognition linked to V5/MT+ and IPS/LIP, respectively, opening to potential tailored applications of non-invasive brain stimulation (NIBS) to functionally improve sensory and metacognitive decision-making processes.