Flickering light with closed eyes temporarily alters consciousness, producing simple visual hallucinations like colors and geometric patterns. In 24 participants, 10 Hz stimulation caused stronger effects than 3 Hz, including vivid visual hallucinations. Participants' Absorption personality trait strongly correlated with the intensity of altered consciousness. The effects were rated similar in strength to those from psychedelic substances, supporting the study of shared brain mechanisms.
Flicker light stimulation (FLS) induces hyperconnectivity between the lateral geniculate nucleus (LGN) and early visual areas, as well as proximal upstream areas of the ventral visual stream (e.g., hV4, VO1). An exploratory analysis indicates that higher-order thalamic nuclei, such as the anterior and mediodorsal nuclei, are strongly affected by FLS, with connectivity changes to upstream cortical visual areas directly reflecting a frequency-dependent increase in experienced visual phenomena. These findings help identify specific thalamocortical interactions involved in the emergence of visual hallucinations.