Hypnosis reduces activity in the default mode network (DMN), a set of brain regions active during rest and linked to self-awareness and task-independent thinking, while increasing activity in prefrontal attentional systems. Using brain imaging and subjective measures during passive visual stimulation, the authors found that the state of attentional absorption after a hypnotic induction was associated with these neural changes. Hypnosis and spontaneous conceptual thought at rest were both subjectively and neurally distinct, offering insight into the hypnotic state and its neural basis.
Ketamine, which blocks N-methyl-D-aspartate receptors (NMDARs), robustly alters functional connectivity in the human brain, shifting patterns from cortex-centered to subcortex-centered connections. This effect was detected with 87.5% accuracy compared to saline. Pre-treatment with risperidone strongly modulated the connectivity changes (81.25% accuracy), whereas lamotrigine did not (43.75% accuracy). The differential modulation suggests the connectivity effects stem primarily from NMDAR blockade rather than downstream glutamate release. No such differential effect was seen in measures of brain response amplitude, underscoring the value of connectivity analysis for understanding how drugs affect the brain.
In depersonalization disorder (DPD), a condition marked by a diminished sense of self and dampened emotional experience, functional MRI revealed that emotional processing is altered. Before treatment, patients showed reduced brain activity in the insula—a region linked to interoceptive awareness and feeling states—along with attenuated autonomic responses to emotional visual stimuli. After pharmacological treatment, clinical improvement in DPD symptoms was associated with increased insula activity. A right ventrolateral prefrontal cortex area also appeared to be involved in top-down inhibition of emotional responses. These findings connect emotional numbing in DPD to disrupted interoception and self-related processes.
Coloured hearing synaesthetes experience colors when hearing words, and some also experience the 'alien colour effect' (ACE), where color names trigger a different color than the one named. The ACE slows color naming in a Stroop task, reflecting cognitive interference from consciously experienced synaesthetic colors. Functional magnetic resonance imaging shows that hippocampal activation distinguishes synaesthetes with the ACE from those without it and from non-synaesthetes. These findings challenge reductive functionalism, which identifies mental states with causal roles. In synaesthesia, color qualia arise from both hearing words and seeing surfaces, and in the ACE these functions oppose each other, providing empirical grounds to argue that reductive functionalism cannot account for conscious experiences.