Japanese Scientist Develops AI-Powered ‘Mind-Captioning’ Technology to Convert Mental Images into Text
In a groundbreaking advancement in neuroscience and artificial intelligence, a Japanese researcher has developed a novel technique that translates people’s mental images into descriptive text using brain scans combined with AI. This emerging technology, coined “mind-captioning,” could pave the way for innovative communication aids and deepen our understanding of how the brain processes visual information.
The research, led by Tomoyasu Horikawa of NTT’s Communication Science Laboratories near Tokyo, was published on November 5, 2025, in the journal Science Advances. Horikawa’s team applied functional magnetic resonance imaging (fMRI), a non-invasive scanning method that measures brain activity, to capture the neural responses of participants as they viewed thousands of diverse video clips.
Methodology: From Brain Activity to Language
Six native Japanese speakers, aged 22 to 37, were scanned while watching 2,180 silent videos ranging from simple objects to complex scenes and actions. The researchers first converted the captions of those videos into numerical sequences using large language models—advanced AI systems trained on extensive datasets. Separate AI decoders were then trained to correlate the participants’ brain activity with these numerical representations of the captions.
When participants later watched or recalled videos outside the training dataset, the AI decoders interpreted their brain patterns and generated progressively refined sequences of words that collectively formed textual descriptions of what the subjects were visualizing or remembering. Remarkably, the AI system produced English-language descriptions even though participants were not English speakers.
Scientific and Medical Implications
Horikawa emphasized that mind-captioning can generate comprehensive visual descriptions without relying on brain regions traditionally involved in language processing. This suggests potential applications for individuals with language impairments, such as aphasia or amyotrophic lateral sclerosis (ALS), who struggle to communicate verbally. Psychologist Scott Barry Kaufman noted that the technology might also offer new support for non-verbal autistic individuals and others facing communication challenges.
Ethical Considerations: Balancing Innovation with Privacy
While the technology holds promise, experts caution that it raises profound ethical questions regarding mental privacy. Marcello Ienca, a leading scholar in AI ethics and neuroethics at the Technical University of Munich, called it “the ultimate privacy challenge,” particularly if applied beyond medical contexts. The possibility of decoding a person’s private thoughts before they are expressed verbally intensifies concerns about consent and data protection.
Adding to this, social scientist Łukasz Szoszkiewicz of the Neurorights Foundation stressed the importance of treating neural data as inherently sensitive. He advocated for explicit, purpose-limited consent and user-controlled unlocking mechanisms to prevent unauthorized access to inner thoughts. Given the integration of AI in this process, he highlighted the urgent need for tailored legal and cybersecurity frameworks.
Limitations and Future Directions
Horikawa cautioned that the current approach requires extensive data collection from willing participants and is not yet accurate enough for everyday practical use. Additionally, the study’s video dataset focused on typical scenes, leaving unanswered questions about how well the system can interpret unusual or unexpected mental images.
Thus, despite public fears, Horikawa reassured that the present technology cannot readily decode deeply private thoughts. Instead, it represents a promising stepping stone in the broader field of brain-reading research, with potentially transformative applications in health care and beyond.
As neuroscience and AI continue to advance, this pioneering mind-captioning research not only offers new insight into the visual mind but also highlights the urgent responsibility to safeguard mental privacy and ethical standards in emerging neurotechnologies.
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