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Olfactory hallucinations are inhibited by increasing brain gamma‐aminobutyric acid levels (684.8)
Author(s) -
Henkin Robert
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.684.8
Subject(s) - hyposmia , gabaergic , neuroscience , disinhibition , transcranial magnetic stimulation , stimulation , medicine , gamma aminobutyric acid , brain activity and meditation , psychology , electroencephalography , receptor , inhibitory postsynaptic potential , disease , covid-19 , infectious disease (medical specialty)
Olfactory hallucinations without associated myoclonic activity are obnoxious, horrible sensations which occur in the nasal cavity without any external stimulation and are labeled phantosmias. They are so pervasive and persistent that they can permeate the entire being like a persistent, unremitting pain. They are of two types: unirhinal (in one nostril) and birhinal (in both nostrils). Unirhinal phantosmias occur spontaneously, mainly in women, are uncommon but cyclic in nature, are exacerbated by laughing or shouting, have associated EEG abnormalities and are inhibited by Valsalva maneuvers or CO2 inhalation. Birhinal phantosmias occur commonly following loss of smell (hyposmia), occur equally in men and women, are persistent not cyclic, have few associated EEG abnormalities and are unchanged by physiological maneuvers. Functional magnetic brain imaging revealed massive activation in prefrontal cortex to perception of these phantosmias. Magnetic resonance spectroscopy revealed lower than normal levels of GABA in these brain regions. Treatment with GABAergic drugs or transcranial magnetic stimulation increased brain GABA levels and inhibited these phantosmias. These studies indicate inhibition of brain GABA can initiate phantosmias, as occurs in phantom limb, by activating normally inhibited brain pathways which are activated either spontaneously, by stimulation of peripheral olfactory pathways or following hyposmia but are inhibited by increasing brain GABA levels.