A single dose of ketamine could alter communication between different brain regions. This discovery opens new perspectives for treating mental disorders.
The research, presented at the Psychedelic Science 2025 conference, examines ketamine's impact on human neuroplasticity. Neuroplasticity refers to the brain's ability to adapt by forming new connections. Although the results haven't yet been peer-reviewed, they provide valuable insight into this substance's mechanism of action.
Clinical trials have already shown ketamine's effectiveness against depression within hours. In animals, it stimulates the growth of new dendritic spines, essential for synapses. However, its functioning in humans remains poorly understood. To clarify this, researchers scanned the brains of 11 men before and after ketamine administration.
The study used functional magnetic resonance imaging (fMRI) to observe changes in brain activity. Normally, high-level brain networks like the default mode network (DMN) communicate less with low-level sensory networks. After ketamine intake, this hierarchy appears to flatten, with increased communication between these networks.
The DMN, often associated with daydreaming and planning, is linked to depression when overactive. PET scans also revealed changes in the posterior cingulate cortex, a key DMN region. These observations suggest ketamine reorganizes brain communication, potentially explaining its antidepressant effect.
Despite these promising results, the study has limitations, including a small number of participants and no placebo group. Nevertheless, it represents an important step in understanding ketamine's action on the human brain.
What is neuroplasticity?
Neuroplasticity is the brain's remarkable ability to reshape itself throughout life. It enables the formation of new neural connections in response to learning or experience.
This phenomenon is crucial for recovery after brain injury. It also explains how certain therapies can durably modify brain circuits involved in mental disorders.
By promoting neuroplasticity, ketamine might 'reset' some dysfunctional circuits. This property makes it a promising candidate for treating treatment-resistant depression.
However, the precise mechanisms by which ketamine affects neuroplasticity remain to be elucidated. Further research is needed to fully understand its therapeutic potential.
How does the default mode network (DMN) work?
The default mode network is active when we're not focused on the external world. It's involved in daydreaming, self-reflection, and memory.
Excessive DMN activity has been associated with disorders like depression. Affected individuals tend to ruminate, getting lost in repetitive negative thoughts.
Ketamine appears to reduce this hyperactivity, enabling better thought regulation. This could explain its rapid effect on depressive symptoms.
The DMN also plays a role in integrating information between different brain regions. Its dysfunction could therefore affect many aspects of cognition and mood.