Perceptions are formed when the stimulation of various organs of sensation is transmitted to the central nervous system, and those perceptions change in conformity with the form of this stimulation, on the one hand, and with the state of the neural conductors and nerve cells, on the other.
If the two optic nerves are severed, the whole world of visual perceptions disappears for a given psyche. If the nervous system is poisoned with Santonin, all objects will be perceived in a different hue than before.
If an organism is subjected to the action of a sufficient dose of narcotic toxin, not only will perceptions disappear but psychical images and even emotions and desires will disappear as well. Disrupt the nourishment of the cortex of the brain, and the entire psychical world seems confused and disordered; all its relationships change dramatically. But the physical world, regardless of this, remains as before.
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BOGDANOV, A, 2020. Empiriomonism: essays in philosophy, books 1-3. Chicago, IL: Haymarket Books. ISBN 978-1-64259-348-8, p. 12.