Today's eye candy focuses on “sense-ational perceptions.” On April 16, 1943, Swiss chemist Albert Hoffman discovered the hallucinogenic effects of LSD when he accidently consumed part of the drug. In Wednesday Is Indigo Blue: Discovering the Brain of Synesthesia, Richard Cytowic and David Eagleman explain the neuroscience and genetics behind synesthesia's multisensory experiences, a phenomenon that can be imitated by taking LSD.
According to Cytowic and Eagleman, “synthesia” means “joined sensation, such that a voice or music, for example, is not only heard but also seen, tasted, or felt as a physical touch.” Other examples of synesthesia include an “icy voice” or a “warm color,” creating a union of separate sensory perceptions.
In the following passage, Cytowic and Eagleman explain how LSD creates synesthetic effects in users:
LSD, mescal, and other anti-serotonergic hallucinogens sometimes produce synesthesia, particularly the sound-to-sight variety. Almost all measures of color vision are affected in volunteers given LSD. Given the drug’s rapid onset of action, we conclude that it must operate on preexisting pathways. LSD is thought to have two main effects: increasing transmission of primary sensory inputs at early levels while inhibiting pathways within the cortex.
In general, serotonin dampens overactive neurons to various internal and external stimuli. Given that serotonin is primarily an inhibitory neurotransmitter and LSD blocks its receptors, the resulting disinhibition allows neural targets to be more easily activated by abnormal inputs, hence synesthesia. Serotonin receptors are maximally concentrated in the hippocampus, thalamic nuclei, basal ganglia, and cerebral cortex. Depth electrodes implanted in animals and humans while on LSD reveal a desynchronized cortex and synchronized, paroxysmal discharges in hippocampus and amygdale. This means that such individuals are aroused but unable to discriminate among sensory channels. In humans, these subcortical discharges coincide behaviorally with heightened emotion and perceptual distortion during the drug high.
Synesthesia is also a naturally occurring phenomenon. Take a Synesthesia Test to see if you can taste the colors of the rainbow.