Causal role of prefrontal cortex in the threshold for access to consciousness

TLDR

Conscious perception of briefly presented stimuli is thought to involve top‑down amplification loops in the prefrontal cortex, but the neural mechanisms underlying this process remain unclear. The study aimed to determine whether the prefrontal cortex causally influences the threshold for conscious access to masked visual stimuli. This was investigated by measuring visual backward‑masking thresholds in patients with focal prefrontal lesions, using objective and subjective performance metrics while controlling for attention deficits. Patients with left anterior prefrontal lesions showed a systematic increase in masking thresholds, especially affecting subjective reports more than objective performance, yet objective accuracy conditioned on subjective visibility remained normal, supporting a causal role of PFC in conscious perception and suggesting a dual‑route signal‑detection framework.

Abstract

What neural mechanisms support our conscious perception of briefly presented stimuli? Some theories of conscious access postulate a key role of top–down amplification loops involving prefrontal cortex (PFC). To test this issue, we measured the visual backward masking threshold in patients with focal prefrontal lesions, using both objective and subjective measures while controlling for putative attention deficits. In all conditions of temporal or spatial attention cueing, the threshold for access to consciousness was systematically shifted in patients, particular after a lesion of the left anterior PFC. The deficit affected subjective reports more than objective performance, and objective performance conditioned on subjective visibility was essentially normal. We conclude that PFC makes a causal contribution to conscious visual perception of masked stimuli, and outline a dual-route signal detection theory of objective and subjective decision making.