Biology subjects

Amaya, I. A.

Publications and source records attributed to Amaya, I. A..

2 recordsLinked to original sources

bioRxiv2024

Thalamocortical interactions reflecting the intensity of flicker light-induced visual hallucinatory phenomena

The thalamus has a critical role in the orchestration of cortical activity. Aberrant thalamocortical connectivity occurs together with visual hallucinations in various pathologies and drug-induced states, highlighting the need to better understand how thalamocortical interactions may contribute to hallucinatory phenomena. However, concurring symptoms and physiological changes that occur during psychopathologies and pharmacological interventions make it difficult to distil the specific neural correlates of hallucinatory experiences. Flicker light stimulation (FLS) at 10 Hz reliably and selectively induces transient visual hallucinations in healthy participants. Arrhythmic flicker elicits fewer hallucinatory effects while delivering equal amounts of visual stimulation, together facilitating a well-controlled experimental setup to investigate the neural correlates of visual hallucinations driven by flicker rhythmicity. In this study, we implemented rhythmic and arrhythmic FLS during fMRI scanning to test the elicited changes in cortical activation and thalamocortical functional connectivity. We found that rhythmic FLS elicited stronger activation in higher-order visual cortices compared to arrhythmic control. Consistently, we found that rhythmic flicker selectively increased connectivity between ventroanterior thalamic nuclei and higher-order visual cortices compared to arrhythmic control, which was also found be positively associated with the subjective intensity of visual hallucinatory effects. As these thalamic and cortical areas do not receive primary visual inputs, it suggests that the thalamocortical connectivity changes relate to a higher-order function of the thalamus, such as in the coordination of cortical activity. In sum, we present novel evidence for the role of specific thalamocortical interactions with ventroanterior nuclei within visual hallucinatory experiences. Importantly, this can inform future clinical research into the mechanistic underpinnings of pathologic hallucinations.

neuroscience↗

bioRxiv2023

Flicker light stimulation induces thalamocortical hyperconnectivity with LGN and higher-order thalamic nuclei

The thalamus is primarily known as a relay for sensory information; however, it also critically contributes to higher-order cortical processing and coordination. Thalamocortical hyperconnectivity is associated with hallucinatory phenomena that occur in various psychopathologies (e.g., psychosis, migraine aura) and altered states of consciousness (ASC, e.g., induced by psychedelic drugs). However, the exact functional contribution of thalamocortical hyperconnectivity in forming hallucinatory experiences is unclear. Flicker light stimulation (FLS) can be used as an experimental tool to induce transient visual hallucinatory phenomena in healthy participants. Here, we use FLS in combination with fMRI to test how FLS modulates thalamocortical connectivity between specific thalamic nuclei and visual areas. We show that FLS induces thalamocortical hyperconnectivity between LGN, early visual areas and proximal upstream areas of ventral and dorsal visual streams (e.g., hV4, VO1, V3a). Further, an exploratory analysis indicates specific higher-order thalamic nuclei, such as anterior and mediodorsal nuclei, to be strongly affected by FLS. Here, the connectivity changes to upstream cortical visual areas directly reflect a frequency-dependent increase in experienced visual phenomena. Together these findings contribute to the identification of specific thalamocortical interactions in the emergence of visual hallucinations. HighlightsO_LIFlicker light stimulation (FLS) induces thalamocortical hyperconnectivity between the first-order thalamic LGN and early visual cortices, likely due to entrainment. C_LIO_LIThalamocortical connectivity between LGN and upstream visual areas, but not V1, is associated with the intensity of visual hallucinations. C_LIO_LIThalamocortical connectivity changes with higher-order thalamic nuclei, such as anterior and mediodorsal nuclei, show strongest modulation by flicker frequency, which corresponds to the intensity of visual hallucinations. C_LI

neuroscience↗