- Dec 31, 2019
- 223
- Tinnitus Since
- 02/05/2019
- Cause of Tinnitus
- unknown:medication,cannabis,stress,sleep deprivation
This study is about Visual Snow Syndrome, but it also implies tinnitus. I'm honestly more and more convinced that for a certain subtype of tinnitus patients they may have the same underlying condition. For some time I've felt that the key to understanding tinnitus on the neurological level is in visual snow. Visual snow teaches us about tinnitus and vice versa.
For those who do not know, the visual symptoms of visual snow syndrome have been described as a thalamocortical dysrhytmia of the visual pathway exactly like tinnitus has been described as a thalamocortical dysrhytmia of the auditory pathway.
The whole publication is interesting, especially for those who have VSS, but I want to specifically point to the following paragraph describing the role of the Thalamus in this syndrome:
One pathophysiologic theory regarding the origin of visual hallucinations has emphasized the role of the thalamus. Ffytche used photic stimulation to induce Purkinje hallucinations (colors, geometrical shapes, motion) in volunteers while monitoring them with fMRI and EEG. He found a wide network of areas with increased brain activity including the bilateral ventral occipitotemporal regions centered on the fusiform gyrus, extending medially to the lingual gyrus and laterally to the inferior temporal gyrus. Interestingly, while the occipitotemporalactivity was significantly increased during visual hallucinations compared to control conditions, the primary visual cortex (V1) was not significantly more active, and the lateral geniculate nucleus (LGN) was actually significantly decreased compared to controls. Ffytche hypothesized that during the visual hallucinations, the LGN had switched from its tonic mode where retinal input is sent to the cortex in a proportional fashion) to its burst mode (where input and output become partly
disassociated), in effect creating a "thalamic blindness". He theorized that this burst mode might create a transient LGN de-afferentation allowing hallucinations to form in a fashion similar to CBS hallucinations. Some authors have suggested that the coherent low-frequency thalamic oscillation and the subsequent reduced lateral cortical inhibition create a "thalamocortical dysrhythmia" that might underly multiple neurologic processes including tinnitus and phantom limb pain, in addition to visual snow.
https://www.researchgate.net/public...ria_Clinical_Implications_and_Pathophysiology
For those who do not know, the visual symptoms of visual snow syndrome have been described as a thalamocortical dysrhytmia of the visual pathway exactly like tinnitus has been described as a thalamocortical dysrhytmia of the auditory pathway.
The whole publication is interesting, especially for those who have VSS, but I want to specifically point to the following paragraph describing the role of the Thalamus in this syndrome:
One pathophysiologic theory regarding the origin of visual hallucinations has emphasized the role of the thalamus. Ffytche used photic stimulation to induce Purkinje hallucinations (colors, geometrical shapes, motion) in volunteers while monitoring them with fMRI and EEG. He found a wide network of areas with increased brain activity including the bilateral ventral occipitotemporal regions centered on the fusiform gyrus, extending medially to the lingual gyrus and laterally to the inferior temporal gyrus. Interestingly, while the occipitotemporalactivity was significantly increased during visual hallucinations compared to control conditions, the primary visual cortex (V1) was not significantly more active, and the lateral geniculate nucleus (LGN) was actually significantly decreased compared to controls. Ffytche hypothesized that during the visual hallucinations, the LGN had switched from its tonic mode where retinal input is sent to the cortex in a proportional fashion) to its burst mode (where input and output become partly
disassociated), in effect creating a "thalamic blindness". He theorized that this burst mode might create a transient LGN de-afferentation allowing hallucinations to form in a fashion similar to CBS hallucinations. Some authors have suggested that the coherent low-frequency thalamic oscillation and the subsequent reduced lateral cortical inhibition create a "thalamocortical dysrhythmia" that might underly multiple neurologic processes including tinnitus and phantom limb pain, in addition to visual snow.
https://www.researchgate.net/public...ria_Clinical_Implications_and_Pathophysiology