For severely depressed inpatients aged 18–85, electroconvulsive therapy (ECT) led to remission in 63% of patients, while ketamine infusions led to remission in 46%, a statistically significant difference. Both treatments required a median of six sessions to achieve remission. ECT caused more serious and long-lasting side effects, including persisting amnesia, whereas ketamine caused more treatment-emergent adverse events leading to dropouts. Among those who remitted, about two-thirds in each group relapsed within 12 months, with no significant difference between treatments. Ketamine, though less effective than ECT, appears to be a safe and useful option for treating unipolar depression.
This chapter reframes the Hard Problem of consciousness as a Placement Problem: how subjective phenomena fit into an objective scientific ontology. It surveys varieties of physicalism (reductive, non-reductive, grounding-based) and their responses to anti-physicalist arguments (zombies, subjective character of experience, knowledge argument), finding that persistent tensions remain even when explanatory gaps are treated as epistemic rather than metaphysical. Non-physicalist alternatives—naturalistic dualism, panpsychism, neutral monism, idealism—are assessed for explanatory ambitions and costs. The chapter concludes by proposing strong metaphysical emergentism as a tentative position: consciousness may be a genuine ontological novelty, dependent on yet irreducible to the physical world.
The chapter examines the debate over neural correlates of consciousness, focusing on whether the prefrontal cortex is part of the neural basis of perceptual awareness. It clarifies the concept of neural correlates and surveys methodological challenges, including the distinction between correlates, causes, and enabling conditions. The discussion turns to the dispute between posterior and anterior theories, which respectively emphasize sensory cortices and prefrontal regions. The chapter develops a pluralistic proposal distinguishing two forms of phenomenal consciousness: one tied to rational accessibility and another that is not. Posterior regions may suffice for basic phenomenal experience, whereas prefrontal involvement emerges when consciousness plays rational or epistemic roles.
The letter argues that cognitive science of consciousness, despite recent progress, tends to downplay conceptual issues and underestimate the difficulties of various problems. This tendency, illustrated with a few prominent examples, may be problematic for the field's future progress.