Synesthesia is a condition in which stimulation of one sensory modality results in perception of another

Question

One man reportedly tastes shapes. Many synesthetic people hear colors. Based on what you know about sensation, propose a physiological mechanism that explains the phenomenon of synesthesia.

What will be an ideal response

Answer 1

Usually a given receptor can only convey a single type of sensory modality. For instance, photoreceptors can usually only relay impulses related to light intensity. Some receptors can relay different modalities based on the type of stimulus received. Lamellated corpuscles relay information about pressure in response to low frequency stimulation but relay information about vibration in response to higher frequency stimulation. Perhaps some types of synesthesia result from anomalous receptors that can send very different information in response to different frequency or intensity of stimulation. A stronger explanation for the phenomenon may be related to the fact that sensations are interpreted based on which part of the cerebral cortex receives the impulses from the 3rd order neuron in the sensory pathway. Synesthetic patients may have unusual distributions of neurons to the cerebral cortex. Most people would sense the taste "sweet" because their 3rd order neuron carrying those impulses terminated in the gustatory area. The man who tastes shapes may have a "sweet" neuron that terminates in the "shape" area of the visual cortex.