Affective and cognitive prefrontal cortex projections to the lateral habenula in humans
Anterior insula (AI) and dACC are known to process information about pain, loss, adversities, bad, harmful or suboptimal choices and consequences that threaten survival or well-being. Pain and loss activate also pregenual ACC (pgACC), linked to sad thoughts, hurt and regrets. The lateral habenula (LHb) is stimulated by predicted and received pain, discomfort, aversive outcome, loss. Its chronic stimulation makes us feel worse/low and gradually stops us choosing and moving for suboptimal, hurtful or punished choices, by direct and indirect (via RMTg) inhibition of DRN and VTA/SNc. Response selectivity of LHb neurons suggests their cortical input from affective and cognitive evaluative regions that make expectations about bad or suboptimal outcomes. Based on these facts I predicted direct corticohabenular projections from the dACC, pgACC and AI, as part of the adversity processing circuit that learns to avoid bad outcomes by suppressing dopamine and serotonin signal. Using DTI I found dACC, pgACC, AI, adjacent caudolateral and lateral OFC projections to LHb. I predicted no corticohabenular projections from the reward processing regions: medial OFC and vACC because both respond most strongly to good, high value stimuli and outcomes, inducing serotonin and dopamine release respectively. This lack of LHb projections was confirmed for vACC and likely for mOFC. The surprising findings were the corticohabenular projections from the cognitive prefrontal cortex regions, known for flexible reasoning, planning and combining whatever information are relevant for reaching current goals. I propose that prefrontohabenular projections provide a teaching signal for value-based choice behaviour, to learn to deselect, avoid or inhibit the potentially harmful, low valued or wrong choices, goals, strategies, predictions, models and ways of doing things, to prevent bad or suboptimal consequences.