| Part | Fact | Value | Species | n | Source | Access |
|---|---|---|---|---|---|---|
| I. Pre-receptor | Proportion of inspired volumetric flow passing through the olfactory airway (quiet breathing) | ~10 % | human | 1 (model) | Keyhani, Scherer, Mozell 1995 10.1115/1.2794204 | abstract |
| I. Pre-receptor | Proportion of flow passing below the inferior turbinate | ~30 % | human | 1 | Keyhani 1995 10.1115/1.2794204 | abstract |
| I. Pre-receptor | Review statement: under 15% of inspired air passes through the olfactory region during normal breathing | <15 % | human | NR | Li et al. 2018 10.1093/chemse/bjy013 | partial |
| I. Pre-receptor | Review: usually under 10% of inspired air reaches the olfactory region | <10 % | human | NR | Jiang X et al. 2026 10.1007/s12016-026-09149-3 | full |
| I. Pre-receptor | Olfactory airflow proportion by nasal vestibule phenotype at 15 L/min | 3.0-7.7 (standard); 2.0-6.8 (notched); 1.2-5.4 (elongated) % | human | NR | Sicard & Frank-Ito 2021 (cited via Jiang 2026) NR | partial |
| I. Pre-receptor | Median flow at the olfactory cleft, Standard phenotype, anterior region | 0.5006 L/min | human | 10 | Sicard, Shah, Frank-Ito 2022 10.1080/08958378.2022.2115175 | abstract |
| I. Pre-receptor | Olfactory airflow proportion by age | children 13.3-15; older adults 3.1-4.9 % | human | NR | Dong et al. 2022 (cited via Jiang 2026) 10.1002/cnm.3565 | partial |
| I. Pre-receptor | Upper third of section D (olfactory cleft + upper middle meatus) receives unilateral airflow | 11.1 ± 7.4 % | human | 3 | Cherobin et al. 2018 10.1371/journal.pone.0207178 | full |
| I. Pre-receptor | Relieving nasal valve obstruction: increase in total airflow / increase in olfactory-region airflow | 23.1 / 334 % | human | 1 (model) | Zhao et al. 2004 (cited via Jiang 2026) 10.1093/chemse/bjh033 | partial |
| I. Pre-receptor | Inspiratory flow per nostril during a sniff | > 300 ml/s | human | NR | Zhao, Dalton, Yang, Scherer 2006 10.1093/chemse/bjj008 | abstract |
| I. Pre-receptor | Odorant flux to the olfactory region: turbulent versus laminar flow | no significant difference at 300-1,000 ml/s | human | 1 model | Zhao et al. 2006 10.1093/chemse/bjj008 | abstract |
| I. Pre-receptor | Pressure drop concentrated around the head of the inferior turbinate | >50 % of total pressure drop | human | 22 | Zhao & Jiang 2014 10.1002/alr.21319 | abstract |
| I. Pre-receptor | Mean inspiratory flow at a pressure drop of 15 Pa | 14.5 ± 4.2 L/min | human | 22 | Li et al. 2018 10.1093/chemse/bjy013 | partial |
| I. Pre-receptor | Correlation of anterior nasal vestibule size with l-carvone threshold | 0.31 r | human | 22 | Li et al. 2018 10.1093/chemse/bjy013 | abstract |
| I. Pre-receptor | Correlation of vestibular notch with PEA / l-carvone threshold | 0.32 / 0.33 r | human | 22 | Li et al. 2018 10.1093/chemse/bjy013 | abstract |
| I. Pre-receptor | Correlation of olfactory-region odorant absorption (CFD) with detection threshold in CRS | -0.60 r | human | 29 | Zhao et al. 2014 10.1002/alr.21272 | abstract |
| I. Pre-receptor | Absorption + MCA + CT score + nasal resistance explain variance in threshold | 65 % | human | 29 | Zhao et al. 2014 10.1002/alr.21272 | abstract |
| I. Pre-receptor | Improvement in airflow and odorant delivery rate to the olfactory epithelium after surgery | >1,000-fold | human | 1 | Zhao et al. 2006 Am J Rhinol 10.2500/ajr.2006.20.2848 | abstract |
| I. Pre-receptor | Optimal sniff flow for the average person | 30 L/min | human | 21 | Laing 1983 10.1068/p120099 | abstract |
| I. Pre-receptor | Optimal sniff volume | 200 cm3 | human | 21 | Laing 1983 10.1068/p120099 | abstract |
| I. Pre-receptor | Optimal sniff duration | 0.4 s | human | 21 | Laing 1983 10.1068/p120099 | abstract |
| I. Pre-receptor | A single natural sniff provides information equal to | ≥7 sniffs | human | 21 | Laing 1983 10.1068/p120099 | abstract |
| I. Pre-receptor | Latency of sniff adjustment to stimulus properties | 160-260 ms | human | NR | Johnson, Mainland, Sobel 2003 (cited via Ferdenzi 2015) 10.1152/jn.00115.2003 | partial |
| I. Pre-receptor | Variance in sniff volume explained by pleasantness (linear / quadratic) | 0.46 / 0.62 R2 | human | 20 (Exp. 1) | Ferdenzi et al. 2015 10.3389/fpsyg.2015.01776 | full |
| I. Pre-receptor | Variance in sniff duration explained by pleasantness (linear / quadratic) | 0.51 / 0.68 R2 | human | 20 | Ferdenzi et al. 2015 10.3389/fpsyg.2015.01776 | full |
| I. Pre-receptor | Thresholds of the high-flow and low-flow nostrils are equal because sniffing is longer through the low-flow nostril | qualitative | human | NR | Sobel et al. 2000 10.1093/chemse/25.1.1 | abstract |
| I. Pre-receptor | Proportion of people with a nasal cycle (>=1 switch of dominant side in 24 h) | 100 (33/33) % | human | 33 | Kahana-Zweig et al. 2016 10.1371/journal.pone.0162918 | full |
| I. Pre-receptor | Mean nasal cycle length | 2.15 ± 1.84 (range 0.25-10.35) h | human | 33 | Kahana-Zweig et al. 2016 10.1371/journal.pone.0162918 | full |
| I. Pre-receptor | Cycle length awake / asleep | 2.02 ± 1.7 / 4.5 ± 1.7 h | human | 33 | Kahana-Zweig et al. 2016 10.1371/journal.pone.0162918 | full |
| I. Pre-receptor | Duration of left / right dominance | 2.63 ± 0.89 / 2.17 ± 0.89 h | human | 33 | Kahana-Zweig et al. 2016 10.1371/journal.pone.0162918 | full |
| I. Pre-receptor | Mean 24 h amplitude of the laterality index LI (awake / asleep) | 0.47 ± 0.14 (0.34 / 0.78) LI | human | 33 | Kahana-Zweig et al. 2016 10.1371/journal.pone.0162918 | full |
| I. Pre-receptor | The low-flow nostril judges mixtures as biased toward the slowly sorbed compound | 17/20 people | human | 20 | Sobel et al. 1999 (details via Stanford Magazine) 10.1038/46944 | abstract |
| I. Pre-receptor | Longer GC retention time gives a smaller LB/MB ratio (odorant retained anteriorly) | qualitative, 16 compounds | frog | 24 | Mozell 1970 10.1085/jgp.56.1.46 | abstract |
| I. Pre-receptor | Butanol produces an anterior-posterior sorption gradient, octane sorbs evenly; slope does not change with flow | qualitative | bullfrog | NR | Hornung & Mozell 1977 10.1085/jgp.69.3.343 | abstract |
| I. Pre-receptor | Solubility in mucosa is compound-specific; poorly water-soluble compounds dissolve in mucosa more than predicted | qualitative | human | NR | Kurtz, Zhao, Hornung, Scherer 2004 10.1093/chemse/bjh079 | abstract |
| I. Pre-receptor | Range of mucus/air partition coefficients used in the model | 1e-6 - 1 dimensionless | model (human/canine paramete | NR | Sen & Zwicker 2023 (arXiv 2301.09852) NR | full |
| I. Pre-receptor | Diffusion coefficient in mucus / in air | 1e-6 - 1e-5 / 1e-2 - 0.1 cm2/s | model | NR | Sen & Zwicker 2023 NR | full |
| I. Pre-receptor | Decay length of odorant concentration along the nasal cavity | 5-50 cm | model | NR | Sen & Zwicker 2023 NR | full |
| I. Pre-receptor | LFER for 193 thresholds (Nagata data) | R2 = 0.748; SD = 0.830 log units | human | 193 compounds | Abraham, Sanchez-Moreno, Cometto-Muniz, Cain 2012 10.1093/chemse/bjr094 | abstract |
| I. Pre-receptor | LFER for 353 pooled thresholds | R2 = 0.759; SD = 0.819 log units | human | 353 compounds | Abraham et al. 2012 10.1093/chemse/bjr094 | abstract |
| I. Pre-receptor | Share of information explained: odour threshold / odour threshold + descriptors of length / eye irritation / nasal pungency | 77 / 82 / 94 / 95 % | human | NR | Abraham et al. 2007 (conference paper) NR | full |
| I. Pre-receptor | Terpene odour thresholds | 0.1-1.0 (abstract) and 0.1-1.7 (results) ppm | human | NR | Cometto-Muniz et al. 1998 10.1111/j.1749-6632.1998.tb10640.x | full |
| I. Pre-receptor | Olfactory cleft mucus volume per nasal cavity | 7-144 (median 36.9) mg | human | 30 | Shirai et al. 2023 10.1038/s41598-023-27937-1 | full |
| I. Pre-receptor | Olfactory cleft mucus volume by age: 20s / 60s | 59.1 ± 21.0 / 23.5 ± 10.6 mg | human | 30 | Shirai et al. 2023 10.1038/s41598-023-27937-1 | full |
| I. Pre-receptor | Total protein in olfactory cleft mucus | 6.2-20.8 mg/mL | human | 30 | Shirai et al. 2023 10.1038/s41598-023-27937-1 | full |
| I. Pre-receptor | Copper (Cu) in olfactory cleft mucus | 4.8 ppm (75 µM; range 12.6-189 µM) | human | 30 | Shirai et al. 2023 10.1038/s41598-023-27937-1 | full |
| I. Pre-receptor | Glutathione in pooled respiratory nasal mucus | 163 GSSG / 23 GSH µM | human | NR | Shirai et al. 2023 10.1038/s41598-023-27937-1 | full |
| I. Pre-receptor | CES-1: olfactory cleft / respiratory nasal mucus / saliva | 5.73 / 1.24 / 0.06 µg/mL | human | NR | Shirai et al. 2023 10.1038/s41598-023-27937-1 | full |
| I. Pre-receptor | Olfactory mucus thickness | ~5 µm | mammal (non-human) | NR | McEwen, Jenkins, Martens 2008 10.1016/S0070-2153(08)00812-0 | full |
| I. Pre-receptor | Mucus thickness used in the model | ~10 µm | model | NR | Sen & Zwicker 2023 NR | full |
| I. Pre-receptor | Number of olfactory cilia per receptor cell | 10-20 cilia | human | NR | Morrison & Costanzo 1990 (cited via Chen et al. 2014) 10.1055/s-0033-1361837 | full |
| I. Pre-receptor | Mammalian olfactory cilia are immotile (lack dynein arms) | qualitative | mammal | NR | McEwen 2008 10.1016/S0070-2153(08)00812-0 | full |
| I. Pre-receptor | The OBP2A/OBP2B genes lie in the lipocalin cluster | 9q34 | human | NR | Lacazette et al. 2000 10.1093/hmg/9.2.289 | partial |
| I. Pre-receptor | OBP2A is present in olfactory mucus; high affinity for aldehydes and fatty acids | Kd NR | human | NR | Briand et al. 2002 10.1021/bi015916c | partial |
| I. Pre-receptor | Lys112 determines the specificity of hOBP-2A for aldehydes | qualitative | human (recombinant protein) | NR | Tcatchoff et al. 2006 10.1016/j.febslet.2006.03.017 | abstract |
| I. Pre-receptor | OBP2A and OBP2B sequence identity | ~90 (17 residues differ) % | human | NR | Chen et al. 2025 (arXiv 2507.03794) NR | full |
| I. Pre-receptor | rs2590498: AA threshold scores higher than GG and AG | p = 0.00003 / p < 0.00001 | human | 69 | Sollai et al. 2019 10.1016/j.bbr.2019.112030 | full |
| I. Pre-receptor | rs2590498: AA detects more odorous molecules (GC-O, banana headspace) | F(2,49) = 6.639; p = 0.003 | human | 52 | Melis et al. 2021 NR | full |
| I. Pre-receptor | Deleting all abundant OBPs in basiconic sensilla does not reduce responses (6 sensillum types) | qualitative | Drosophila | NR | Xiao, Sun, Carlson 2019 10.7554/eLife.51040 | abstract |
| I. Pre-receptor | Odorant metabolism in the human nose/mouth (thiol methylation, hexanal reduction, benzyl acetate hydrolysis) occurs within a few seconds | a few s | human | NR | Ijichi et al. 2019 10.1093/chemse/bjz041 | abstract |
| I. Pre-receptor | Olfactory cleft mucus: p-cresyl acetate -> p-cresol | 99 % (TIC peak ratio) | human | pooled sample | Shirai et al. 2023 10.1038/s41598-023-27937-1 | full |
| I. Pre-receptor | Olfactory cleft mucus: 2-phenylethyl acetate hydrolysed | 43 % | human | pooled sample | Shirai et al. 2023 10.1038/s41598-023-27937-1 | full |
| I. Pre-receptor | Olfactory cleft mucus: benzaldehyde -> benzyl alcohol | 51 % | human | pooled sample | Shirai et al. 2023 10.1038/s41598-023-27937-1 | full |
| I. Pre-receptor | Olfactory cleft mucus: octanal -> octanol / octanoic acid | 33 / 50 % | human | pooled sample | Shirai et al. 2023 10.1038/s41598-023-27937-1 | full |
| I. Pre-receptor | Inter-individual variation in esterase activity (pCA, mucus diluted 10x, 5 min) | 5-45 (mean 18) % | human | 29 | Shirai et al. 2023 10.1038/s41598-023-27937-1 | full |
| I. Pre-receptor | Benzaldehyde metabolised in mouse mucus (5 min, 50 µM) | ~80 % | mouse | NR | Nagashima & Touhara 2010 NR (J Neurosci 30:16391) | full |
| I. Pre-receptor | Aromatic acetates / straight-chain acetates metabolised in mouse mucus | 90-100 / 20-40 % | mouse | NR | Nagashima & Touhara 2010 NR (J Neurosci 30:16391) | full |
| I. Pre-receptor | Coumarin hydroxylation: olfactory mucosa / liver microsomes | 13.3 / 0.2 nmol/min/mg protein | rat | 5 mucosae pooled x3 | Thiebaud et al. 2013 10.1371/journal.pone.0059547 | full |
| I. Pre-receptor | EOG increase when CYP is inhibited with ABT: coumarin / quinoline | 43 / 32 % | rat | 5 | Thiebaud et al. 2013 10.1371/journal.pone.0059547 | full |
| I. Pre-receptor | EOG increase with isoamyl acetate when CES is inhibited with BNPP | 30 % | rat | 5 | Thiebaud et al. 2013 10.1371/journal.pone.0059547 | full |
| I. Pre-receptor | Metabolites appear in the olfactory mucosa ex vivo | ~100 ms | rat | NR | Robert-Hazotte et al. 2019 (per CSGA news item) NR (Sci Rep 9:2492; s41598-019-39404-x) | partial |
| I. Pre-receptor | Retronasal EOG amplitude smaller than orthonasal (significant only for PEA) | p = 0.048 | human | 10 | Hummel, Seo, Pellegrino, Heilmann 2017 NR | abstract |
| I. Pre-receptor | Peak retronasal versus orthonasal absorption at the olfactory epithelium (left / right) | +90 / +45 % | human | 1 model, 65 absorption rates | Kim & Zhao 2022 10.1007/s12078-022-09300-2 | abstract |
| I. Pre-receptor | Peak retronasal versus orthonasal absorption (medial / lateral region) | -97 / -75 % | rat | 1 model | Kim & Zhao 2022 10.1007/s12078-022-09300-2 | abstract |
| I. Pre-receptor | Nasopharyngeal changes reduce retronasal absorption (left / right) | 41.4 / 44.2 % | human | 1 | Kim & Zhao 2022 10.1007/s12078-022-09300-2 | abstract |
| I. Pre-receptor | Proportion of VOCs returning to the nasal cavity retronasally after lung retention | 42 ± 15 % | human (calculated) | 38 compounds | Jakubowski & Czerczak 2009 10.1016/j.etap.2009.05.011 | partial |
| I. Pre-receptor | Asymmetry of volatile transport (air curtain) is maximal at Reynolds number | ~800 Re | human (3D-printed model) | 1 | Ni et al. 2015 PNAS NR (not resolved) | abstract |
| I. Pre-receptor | Valeric acid threshold: ortho / retro | 0.01 / 10 % v/v | mouse | NR | Furudono, Cruz, Lowe 2013 10.1186/1471-2202-14-45 | full |
| I. Pre-receptor | Eugenol response amplitude: ortho / retro (dF/F) | 1.92 ± 0.09 / 0.60 ± 0.21 dF/F | mouse | 3 trials | Furudono et al. 2013 10.1186/1471-2202-14-45 | full |
| I. Pre-receptor | Ortho and retro activate different brain regions, most clearly for a food odour (chocolate); butanol/farnesol do not differ by route | qualitative | human | NR | Small, Gerber, Mak, Hummel 2005 10.1016/j.neuron.2005.07.022 | partial |
| I. Pre-receptor | Persistence on skin: top notes / middle notes / base notes | 15-30 min / 3-4 h / >4 h | human (industry convention) | NR | Nogueira & Rodrigues 2021 10.3390/molecules26113095 | full |
| I. Pre-receptor | First-order one-compartment model explains variance in headspace after 1 h on skin (5 fragrances) | 65 (range 32-76) % | human | 5 formulations | Kasting & Saiyasombati 2004 NR | abstract |
| I. Pre-receptor | Evaporation rate constant k1’ (Vector A / B) | 14.5 ± 10.5 / 9.1 ± 8.9 h-1 | human | 20 determinations/vector | Kasting 2006 (CRC chapter) NR | full |
| I. Pre-receptor | r2 of cumulative evaporation (Vector A / B) | 0.80 / 0.73 r2 | human | 143 / 132 points | Kasting 2006 NR | full |
| I. Pre-receptor | Airflow through the measuring chamber on the forearm | 5 L/h (83 mL/min) | human | NR | Vuilleumier et al. 1995 (cited via Kasting 2006) NR | partial |
| I. Pre-receptor | Fragrance with fixative: single-exponential decay; without: bi-exponential | qualitative | human | NR | Kasting & Saiyasombati 2003 NR | abstract |
| I. Pre-receptor | ODT ethyl butyrate / linalool / benzaldehyde | 3.35e-4 / 9.33e-3 / 6 mg/m3 | human | NR | Nogueira & Rodrigues 2021 10.3390/molecules26113095 | full |
| II. Receptors | Orco homomer cryo-EM resolution | 3.50 Å | insect (Apocrypta bakeri) | 1 structure (PDB 6C70) | Butterwick 2018 10.1038/s41586-018-0420-8 | full |
| II. Receptors | MhOR5-eugenol cryo-EM resolution | 2.90 Å | insect (Machilis hrabei) | PDB 7LID | del Marmol 2021 10.1038/s41586-021-03794-8 | full |
| II. Receptors | AaegOR10-Orco heteromer stoichiometry | 1 OR : 3 Orco ratio | insect (Aedes aegypti OR10 + | PDB 8V00, 2.88 Å | Zhao 2024 10.1126/science.adn6384 | full |
| II. Receptors | ApisOR5-Orco geranyl acetate complex resolution | 3.00 Å | insect (Acyrthosiphon pisum) | PDB 8Z9A | Wang/Yin 2024 10.1126/science.adn6881 | full |
| II. Receptors | OR52cs (consensus OR52)-octanoate-Gs cryo-EM resolution | 2.97 Å | human (consensus) | 1 structure | Choi 2023 10.1038/s41467-023-43983-9 | full |
| II. Receptors | OR52cs TM6 extracellular inward shift on activation | 7.4 Å | human (consensus) | 1 | Choi 2023 10.1038/s41467-023-43983-9 | full |
| II. Receptors | OR52cs apo TM5-TM6 lateral opening width | 14 Å | human (consensus) | 1 | Choi 2023 10.1038/s41467-023-43983-9 | full |
| II. Receptors | Apo OR52cs vs AlphaFold2 prediction RMSD | 1.1 Å over 242 Cα | human (consensus) | 242 Cα | Choi 2023 10.1038/s41467-023-43983-9 | full |
| II. Receptors | OR52cs vs OR51E2 cryo-EM RMSD | 1.5 Å over 289 Cα | human | 289 Cα | Choi 2023 10.1038/s41467-023-43983-9 | full |
| II. Receptors | OR sequence identity to structurally characterised GPCRs | <20 % | human | NR | 3decision OR5K1 2024 NR | full |
| II. Receptors | mTAAR9-DMCHA-Gs cryo-EM resolution | 3.46 Å | mouse | PDB 8ITF | Guo 2023 10.1038/s41586-023-06106-4 | full |
| II. Receptors | ConsOR5 apo-Gs resolution (fatty-acid OR paper) | 2.60 Å | human (consensus) / mouse Ol | PDB 9WPM | Han/Sun 2026 10.1016/j.cell.2025.12.018 | abstract |
| II. Receptors | Fraction of human olfactory biopsies yielding odorant-responsive neurons | 52 % | human | NR biopsies | Rawson 1997 10.1152/jn.1997.77.3.1606 | abstract |
| II. Receptors | Fraction of human olfactory neurons responding to odorant with Ca2+ change | 24 % | human | NR | Rawson 1997 10.1152/jn.1997.77.3.1606 | abstract |
| II. Receptors | Odorant-elicited Ca2+ increases in cultured human olfactory neurons abolished by removing extracellular Ca2+ | qualitative NR | human | NR | Gomez 2000 10.1002/1097-4547(20001201)62:5<737::AID-JNR14>3.0.CO;2-A | abstract |
| II. Receptors | Humans distinguishing deuterated acetophenone (d8) from normal | near chance (48-55% correct) % correct | human | 5 subjects | Gane 2013 10.1371/journal.pone.0055780 | full |
| II. Receptors | Humans distinguishing deuterated cyclopentadecanone (musk) from normal | 119/132 correct (~90%) trials | human | 11 subjects | Gane 2013 10.1371/journal.pone.0055780 | full |
| II. Receptors | Human musk receptor OR5AN1 response to muscone vs deuterated muscone in vitro | identical (no discrimination) NR | human (OR5AN1 in vitro) | OR5AN1 + ~25 other OR-odorant pairs | Block 2015 10.1073/pnas.1503054112 | full |
| II. Receptors | Drosophila spontaneous avoidance of deuterated acetophenone, scaling with number of D atoms | behavioural (dose-dependent) NR | Drosophila (NOT human) | NR | Franco 2011 10.1073/pnas.1012293108 | abstract |
| II. Receptors | Untrained humans cannot distinguish acetophenone from deuterated acetophenone | no discrimination NR | human | NR | Keller & Vosshall 2004 10.1038/nn1215 | citation |
| II. Receptors | Enantiomer pairs discriminated above chance (group level) out of 10 tested | 3 of 10 pairs | human | 20 subjects | Laska & Teubner 1999 10.1093/chemse/24.2.161 | abstract |
| II. Receptors | (R)-(-)-carvone activates human OR1A1 pEC50 | -6.82 ± 0.05 (~150 nM) pEC50 | human (OR1A1 in vitro) | NR | de March 2024 10.1038/s41586-024-08126-0 | full |
| II. Receptors | (+)- vs (-)-rose oxide psychophysically indistinguishable in humans | 3.2/9 correct (p=0.41) 3-AFC | human | 19 subjects | Poletti 2017 10.1038/s41598-017-09594-3 | full |
| II. Receptors | Human OR clones screened / genes covered | 511 clones, 394/418 (94%) intact OR genes count | human | 511 clones | Mainland 2013 10.1038/nn.3598 | full |
| II. Receptors | OR-odorant pairs responding above control in human screen | 425 pairs (160 unique ORs) pairs | human | 1,572 pairs tested | Mainland 2013 10.1038/nn.3598 | full |
| II. Receptors | Human ORs with function-altering polymorphisms | 63% (17/27) fraction | human | 27 ORs | Mainland 2013 10.1038/nn.3598 | full |
| II. Receptors | ORs deorphanised in mammalian repertoire screen | 52 mouse + 10 human ORs count | mouse + human | 464 ORs, 93 odorants | Saito 2009 10.1126/scisignal.2000016 | abstract |
| II. Receptors | M2OR database unique OR-odorant pairs (2024 publication) | 51,395 pairs | 11 mammalian (human ~66%, mo | 75,050 bioassays, 42 papers | Lalis 2024 (M2OR) 10.1093/nar/gkad886 | full |
| II. Receptors | Principal Odor Map GNN cross-validation AUROC | 0.89 AUROC | human (crowd perception) | ~5,000 molecules | Lee 2023 (POM) 10.1126/science.ade4401 | full |
| II. Receptors | POM GNN matches or beats median human panellist | 53% of molecules (RF baseline 41%) % molecules | human panel | 320 odorants | Lee 2023 (POM) 10.1126/science.ade4401 | full |
| II. Receptors | POM perceptual-distance vs map-distance correlation | R=0.73 correlation | human | NR | Lee 2023 (POM) 10.1126/science.ade4401 | full |
| II. Receptors | Odorant stimuli whose nominal compound alone caused the odour (contamination QC) | 12 of 50 count | human | 50 stimuli | Lee 2023 (POM) 10.1126/science.ade4401 | full |
| II. Receptors | AI docking prediction of OR activation for unseen odorants | near chance NR | human ORs | panel of human ORs | Tran 2026 NeurIPS ICBINB NR | abstract |
| III. Epithelium & olfactory bulb | Olfactory mucosa area (septum + lateral wall), case 1 | 307 (133+174) mm² | human | 1 cadaver | von Brunn 1892 (via Escada 2013) 10.20344/amp.4238 | partial |
| III. Epithelium & olfactory bulb | Olfactory mucosa area, case 2 | 238 (99+139) mm² | human | 1 cadaver | von Brunn 1892 (via Escada 2013) 10.20344/amp.4238 | partial |
| III. Epithelium & olfactory bulb | Textbook olfactory epithelium area | 5 per nasal cavity; 10 total cm² | human | NR | Purves et al. 2001 (via Hu et al. 2022) NR | partial |
| III. Epithelium & olfactory bulb | Proportion of the nasal cavity occupied by olfactory epithelium | ~3 (human) versus ~50 (rat) % | human; rat | NR | Gross et al. 1982 (via Kikuta 2024) 10.3389/fncir.2024.1406218 | full |
| III. Epithelium & olfactory bulb | Distance from the cribriform plate to the lower boundary of the olfactory mucosa, septum anterior/middle/posterior | 15.9±3.2 / 15.3±3.0 / 16.0±2.8 mm | human | 13 specimens, aged 18–45 | Escada et al. 2013 10.20344/amp.4238 | full |
| III. Epithelium & olfactory bulb | Same distance on the turbinate wall, anterior/middle/posterior | 15.3±2.4 / 14.8±2.3 / 12.3±1.9; minimum 12 mm | human | 13 specimens, aged 18–45 | Escada et al. 2013 10.20344/amp.4238 | full |
| III. Epithelium & olfactory bulb | Proportion of biopsies containing olfactory epithelium, by site | 30–76 % | human | 97 samples / 33 people, aged 21–74 | Féron et al. 1998 10.1001/archotol.124.8.861 | partial |
| III. Epithelium & olfactory bulb | Posterior middle turbinate samples with pure olfactory tissue | 40 % | human | subgroup of 97 samples | Féron et al. 1998 10.1001/archotol.124.8.861 | partial |
| III. Epithelium & olfactory bulb | Number of people with a measurable electro-olfactogram (EOG) in the anterior middle turbinate region | 7/12; 9 sites people; sites | human | 12 volunteers aged 21–48; 15 patients | Leopold et al. 2000 10.1097/00005537-200003000-00016 | abstract |
| III. Epithelium & olfactory bulb | Distribution of olfactory epithelium: anterior 2/3 of the superior turbinate + opposite septum, absent from the superior meatus; OSN density falls with distance from the ethmoid roof | qualitative — | human | NR | Omura et al. 2021 10.1002/alr.22885 | abstract |
| III. Epithelium & olfactory bulb | Correlation between age and the probability of obtaining olfactory epithelium | r = −0.728 — | human | 12 cadavers, 36 samples | Paik et al. 1992 10.1001/archotol.1992.01880070061012 | abstract |
| III. Epithelium & olfactory bulb | Measurements in which the boundary could not be determined because of mucosal change (septum / lateral wall) | 13 / 18 % | human | 13 specimens, aged 18–45 | Escada et al. 2013 10.20344/amp.4238 | full |
| III. Epithelium & olfactory bulb | Mean vertical extent of the olfactory mucosa from the cribriform plate | 14.3 mm | human | 3 people (aged 34, 57, 82) | Paik et al. 1992 (via Escada 2013) 10.1001/archotol.1992.01880070061012 | partial |
| III. Epithelium & olfactory bulb | Total number of OSNs in humans (cited estimate) | 6–10 million (Sankaran 2012); 6–20 million (Escada 2013) cells | human | NR | Sankaran 2012 via Hu 2022; Escada 2013 10.20344/amp.4238 | partial |
| III. Epithelium & olfactory bulb | Number of OMP+ OSNs per side of epithelium | ~5,000,000 cells | mouse (C57BL/6J) | NR | Kawagishi et al. 2014 10.1016/j.neuroscience.2014.04.050 | partial |
| III. Epithelium & olfactory bulb | Number of OSNs in rats: newborn / 8 weeks old | ~500,000 / ~21,000,000 cells | rat (Wistar) | NR | Kawagishi (KAKEN report 25462661) NR | partial |
| III. Epithelium & olfactory bulb | Number of cilia per OSN olfactory knob | 10–30 cilia | human | 8 volunteers | Moran et al. 1982 10.1007/BF01153516 | abstract |
| III. Epithelium & olfactory bulb | Basal cell classification: HBC/GBC not clearly separable by morphology; p75NGFR expression; neurons not layered | qualitative — | human | NR | Hahn et al. 2005 10.1002/cne.20424 | abstract |
| III. Epithelium & olfactory bulb | Two basal progenitor types as in rodents; neuron-rich epithelium always lies just below the cribriform plate | qualitative — | human | 21 cadaver specimens | Holbrook et al. 2011 10.1002/lary.21856 | abstract |
| III. Epithelium & olfactory bulb | OSN half-life | ~90 days | mouse | NR | Gogos et al. 2000 (PMID 11106731) NR | abstract |
| III. Epithelium & olfactory bulb | OSN lifespan or turnover rate in humans | NR — | human | — | — — | — |
| III. Epithelium & olfactory bulb | Total cells in single-cell sequencing (olfactory + respiratory mucosa) | 28,726 cells | human | 4 patients | Durante et al. 2020 10.1038/s41593-020-0587-9 | abstract |
| III. Epithelium & olfactory bulb | Number of mature OSNs / GBCs / HBCs in the single-cell data | 222 / 115 / 2,182 cells | human | 4 patients | Durante et al. 2020 (Extended Data Fig. 6) 10.1038/s41593-020-0587-9 | abstract |
| III. Epithelium & olfactory bulb | Number of olfactory receptors (ORs) with described expression | 140 OR | human | 4 patients | Durante et al. 2020 10.1038/s41593-020-0587-9 | abstract |
| III. Epithelium & olfactory bulb | Number of intact OR genes in humans | ~350 (Maresh); ~400 (Kikuta) genes | human | — | Maresh 2008; Kikuta 2024 10.1371/journal.pone.0002640 | full |
| III. Epithelium & olfactory bulb | Correlation of age with OB volume (left/right) | r = −0.37 / −0.38 — | human | 125 people, aged 19–79 (mean 37) | Buschhüter et al. 2008 (2007 conference abstract) 10.1016/j.neuroimage.2008.05.004 | partial |
| III. Epithelium & olfactory bulb | Correlation of OB volume with odour threshold / identification ability | r = 0.19–0.25 — | human | 125 people | Buschhüter et al. 2008 (2007 conference abstract) 10.1016/j.neuroimage.2008.05.004 | partial |
| III. Epithelium & olfactory bulb | Sex difference in OB volume (men > women) | F(1,110) = 6.16; p = 0.015 — | human | 125 people | Buschhüter et al. 2008 (2007 conference abstract) 10.1016/j.neuroimage.2008.05.004 | partial |
| III. Epithelium & olfactory bulb | Left / right OB volume in healthy people | 67.0±16.7 / 71.2±17.1 mm³ per bulb | human | 51 people, aged 20–69 | Rottstaedt et al. 2018 10.3389/fnagi.2018.00354 | full |
| III. Epithelium & olfactory bulb | Total volume of both OBs | 54.05±16.09 (range 12.8–111.1) mm³ (left + right) | human | 560 people, aged 30–87 | Estrada et al. 2021 (Rhineland Study) 10.1016/j.neuroimage.2021.118464 | full |
| III. Epithelium & olfactory bulb | Age-related decline in OB volume | −0.319 (±0.092) mm³/year | human | 203 people | Estrada et al. 2021 10.1016/j.neuroimage.2021.118464 | full |
| III. Epithelium & olfactory bulb | Association between OB volume and odour identification ability | β = 0.09 (95% CI 0.06–0.12) SD | human | 5,605 people, aged 30–95 | Zeng et al. 2026 (Rhineland, PMID 41769923) NR | abstract |
| III. Epithelium & olfactory bulb | Histological OB volume at ages 25 / 60 / 95 | 50.02 / 43.35 / 36.68 mm³ per bulb | human (female) | 8 bulb pairs, aged 25–102 | Bhatnagar et al. 1987 10.1002/ar.1092180112 | abstract |
| III. Epithelium & olfactory bulb | Olfactory sulcus (OS) depth cut-off for congenital anosmia | ≤8 mm: sensitivity 0.72, specificity 1.0 mm | human | 36 patients + 70 controls, aged 7–79 | Huart et al. 2011 10.3174/ajnr.A2632 | full |
| III. Epithelium & olfactory bulb | Olfactory sulcus depth in controls (left/right) | 8.8±1.5 / 8.9±1.4 mm | human | NR | Abolmaali (via Huart 2011) 10.3174/ajnr.A2632 | partial |
| III. Epithelium & olfactory bulb | Number of glomeruli per bulb | 5,568 ± 830 (SEM); range 2,975–9,325 glomeruli | human | 7 bulbs (inferred), aged 39–89 | Maresh et al. 2008 10.1371/journal.pone.0002640 | full |
| III. Epithelium & olfactory bulb | Number of glomeruli in the < 50 / > 50 age group | 6,960±2,365 (n = 2) / 5,012±785 (n = 5); p = 0.33 glomeruli | human | 7 | Maresh et al. 2008 10.1371/journal.pone.0002640 | full |
| III. Epithelium & olfactory bulb | Number of glomeruli in young people; falls by about 10%/decade; < 30% remain in the 9th–10th decades | ~8,000 glomeruli | human | NR | Meisami et al. 1998 10.1111/j.1749-6632.1998.tb10649.x | abstract |
| III. Epithelium & olfactory bulb | ‘Textbook’ number of glomeruli | 1,100–1,200 glomeruli | human (asserted) | — | Wikipedia, citing Pinching & Powell 1971 (PMID 4108057) + Kosaka 1998 NR | partial |
| III. Epithelium & olfactory bulb | Number of glomeruli per OR (per bulb) | ~16 (human) versus predicted 2 — | human | 7 | Maresh et al. 2008 10.1371/journal.pone.0002640 | full |
| III. Epithelium & olfactory bulb | Number of glomeruli per bulb (median, P56) | 2,851 glomeruli | mouse | 12 bulbs | Weng et al. 2025 10.1111/ejn.70327 | abstract |
| III. Epithelium & olfactory bulb | Number of glomeruli per intact OR gene (per bulb) | 2.50 — | mouse | 12 bulbs | Weng et al. 2025 10.1111/ejn.70327 | abstract |
| III. Epithelium & olfactory bulb | Effective glomerular diameter (median, P56) | 77.54 µm | mouse | 12 bulbs | Weng et al. 2025 10.1111/ejn.70327 | abstract |
| III. Epithelium & olfactory bulb | Number of OSNs per glomerulus (derived) | ~500–900 (human) versus ~1,750 (mouse) OSNs/glomerulus | human; mouse | — | derived from Maresh 2008, Kawagishi 2014, Weng 2025 — | — |
| III. Epithelium & olfactory bulb | Number of mitral cells per bulb at ages 25 / 60 / 95 | 50,935 / 32,718 / 14,501 cells | human (female) | 8 bulb pairs, aged 25–102 | Bhatnagar et al. 1987 10.1002/ar.1092180112 | abstract |
| III. Epithelium & olfactory bulb | Number of mitral cells in young people | ~40,000 cells | human | NR | Meisami et al. 1998 10.1111/j.1749-6632.1998.tb10649.x | abstract |
| III. Epithelium & olfactory bulb | Olfactory bulb neuron turnover rate | 0.008 ± 0.08 (95% CI includes 0); < 1% after 100 years %/year | human | 15 neuronal DNA samples (37 data points) | Bergmann et al. 2012 10.1016/j.neuron.2012.03.030 | full |
| III. Epithelium & olfactory bulb | Turnover rate of non-neuronal cells in the olfactory bulb | 2.0–3.4 %/year | human | 11 samples | Bergmann et al. 2012 10.1016/j.neuron.2012.03.030 | full |
| III. Epithelium & olfactory bulb | Proportion of olfactory bulb neurons renewed per year | up to 50 %/year | rodent | NR | Imayoshi 2008 (via Bergmann 2012) 10.1016/j.neuron.2012.03.030 | partial |
| III. Epithelium & olfactory bulb | RMS migratory stream strong before 18 months of age, almost absent in adults | 18 months | human | aged 0–84 | Sanai et al. 2011 10.1038/nature10487 | abstract |
| III. Epithelium & olfactory bulb | An RMS around an extension of the lateral ventricle; BrdU+ cells mature into neurons in the olfactory bulb | qualitative — | human | NR | Curtis et al. 2007 10.1126/science.1136281 | abstract |
| III. Epithelium & olfactory bulb | No neuroblasts in the adult olfactory bulb; neuroblasts occur singly or in pairs in the RMS; no dividing cells in the RMS | 0 neuroblasts | human | NR | Wang et al. 2011 10.1038/cr.2011.83 | abstract |
| III. Epithelium & olfactory bulb | Length of olfactory tract / olfactory bulb | 2.8±0.1 / 1.0±0.1 cm | human | 6 people, aged 37–84 | Raspeño-García et al. 2024 (bioRxiv) 10.1101/2024.11.26.625157 | full |
| III. Epithelium & olfactory bulb | Cross-sectional area of the olfactory tract | 2.09±0.16 (range 1.01–3.37) mm² | human | 6 people | Raspeño-García et al. 2024 10.1101/2024.11.26.625157 | full |
| III. Epithelium & olfactory bulb | Number of axons in the olfactory tract | NR — | human | — | — — | — |
| III. Epithelium & olfactory bulb | AON volume or AON neuron number measured stereologically | NR — | human | — | — — | — |
| III. Epithelium & olfactory bulb | α-synuclein in the olfactory bulb: PD / DLB / ILBD / elderly controls | 95 / 97 / 67 / 7 (5/69) % | human | 328 autopsies | Beach et al. 2009 10.1007/s00401-008-0450-7 | abstract |
| III. Epithelium & olfactory bulb | Unified staging system for Lewy body disease: stage I = olfactory bulb only; the two older systems could not classify up to 50% of cases | 50 % | human | 417 autopsies | Beach et al. 2009b 10.1007/s00401-009-0538-8 | abstract |
| III. Epithelium & olfactory bulb | Olfactory bulb pathology in cognitively normal older people: tau / Aβ / α-synuclein | 95 / 27 / 20 % | human | 138 people | Tremblay et al. 2022 10.1111/bpa.13075 | abstract |
| III. Epithelium & olfactory bulb | Tau in the olfactory bulb/tract by Braak stage 0–1 / 2 / 3 / 4 / 5–6 | 0 / 31.2 / 37.0 / 85.2 / 100 % | human | 130 autopsies, aged 61–102 | Attems et al. 2005 10.3233/JAD-2005-7208 | abstract |
| III. Epithelium & olfactory bulb | Lewy bodies in the olfactory bulb of PD patients, especially in the AON | 8/8 bulbs | human | 8 brains | Hawkes et al. 1997 10.1136/jnnp.62.5.436 | partial |
| IV. Cortex | The human medial piriform region comprises 4 areas: PirTBd and PirTBv (3-layered paleocortex), PirTit and PirTu (5-layered periallocortex) | 4 areas | human | 10 brains (20 hemispheres), aged 37–79 | Kedo 2024 10.3390/anatomia3020007 | partial |
| IV. Cortex | PirTBv is the only area with a superficial sublayer 3s; PirTBd has layer 1 divided into 1a–1c | qualitative | human | 10 brains | Kedo 2024 10.3390/anatomia3020007 | partial |
| IV. Cortex | PirTit volume (shrinkage-corrected), extremes across brains | 215–626 mm³ | human | 10 brains | Kedo 2024 10.3390/anatomia3020007 | partial |
| IV. Cortex | PirTBv volume, extremes | 34–74 mm³ | human | 10 brains | Kedo 2024 10.3390/anatomia3020007 | partial |
| IV. Cortex | PirTBd volume, extremes | 32–114 mm³ | human | 10 brains | Kedo 2024 10.3390/anatomia3020007 | partial |
| IV. Cortex | Variation in piriform area volume across brains | 2–3-fold | human | 10 brains | Kedo 2024 10.3390/anatomia3020007 | partial |
| IV. Cortex | PirTBd right-lateralised; PirTBv, PirTit, PirTu not asymmetric; no sex difference | p<0.05 (no Bonferroni correction) | human | 10 brains | Kedo 2024 10.3390/anatomia3020007 | partial |
| IV. Cortex | Number of hemispheres in which PirTBd extends beyond the anterior border of the limen insulae | 8/20 hemispheres | human | 20 hemispheres | Kedo 2024 10.3390/anatomia3020007 | partial |
| IV. Cortex | Number of hemispheres in which PirTBv extends beyond the anterior border of the limen insulae | 6/20 hemispheres | human | 20 hemispheres | Kedo 2024 10.3390/anatomia3020007 | partial |
| IV. Cortex | PirTBd extends further anteriorly than PirTBv (in 12 hemispheres), difference | 0.3–1.2 mm | human | 12/20 hemispheres | Kedo 2024 10.3390/anatomia3020007 | partial |
| IV. Cortex | Mean piriform volume in controls, right hemisphere | 485 mm³ | human | 58 controls (TLE cohort) | Steinbart 2023 10.1002/hbm.26274 | abstract |
| IV. Cortex | Mean piriform volume in controls, left hemisphere | 461 mm³ | human | 58 controls | Steinbart 2023 10.1002/hbm.26274 | abstract |
| IV. Cortex | Jaccard overlap between automated and manual segmentation: controls / TLE / AD | 0.5 / 0.40 / 0.34 Jaccard | human | atlas n=30; TLE n=174; ADNI n=151 | Steinbart 2023 10.1002/hbm.26274 | abstract |
| IV. Cortex | Bilaterally lower piriform volume in MCI and AD than in controls | p<0.001 | human | ADNI 47 CN, 71 MCI, 33 AD | Steinbart 2023 10.1002/hbm.26274 | abstract |
| IV. Cortex | Frontal piriform in controls, right/left, mean (SD) | 118 (33) / 104 (22) mm³ | human | 11 controls | Henry 2012 (AES abstract 1.171) NR | abstract |
| IV. Cortex | Temporal piriform in controls, right/left | 134 (33) / 124 (40) mm³ | human | 11 controls | Henry 2012 (AES abstract 1.171) NR | abstract |
| IV. Cortex | Endopiriform nucleus in controls, right/left | 76 (22) / 68 (21) mm³ | human | 11 controls | Henry 2012 (AES abstract 1.171) NR | abstract |
| IV. Cortex | Reduction in piriform/endopiriform volume in TLE with unilateral hippocampal sclerosis, bilateral (own calculation from group means) | ≈27–37 % | human | 8 TLE, 11 controls | Henry 2012 (AES abstract 1.171) NR | abstract |
| IV. Cortex | Right piriform larger than left in controls | ≈17.7 % | human | 20 controls (+60 TLE) | Leon-Rojas 2021 10.1080/02688697.2021.1966385 | full |
| IV. Cortex | Right piriform extends further anteriorly than left | 6 mm (mean) | human | 20 controls | Leon-Rojas 2021 10.1080/02688697.2021.1966385 | full |
| IV. Cortex | Piriform volume in controls, left/right (automated ASHS) | ≈506 / 484 mm³ | human | 26 controls | Lucas 2024 (medRxiv) 10.1101/2024.07.21.24310778 | full |
| IV. Cortex | Anterior commissure streamline diameter: low versus high inter-piriform coupling group | 4.60 vs 5.61 DSI Studio units | human | 55 TLE | Lucas 2024 (medRxiv) 10.1101/2024.07.21.24310778 | full |
| IV. Cortex | Number of anterior commissure streamlines: low versus high group | 25.31 vs 42.44 streamlines | human | 55 TLE | Lucas 2024 (medRxiv) 10.1101/2024.07.21.24310778 | full |
| IV. Cortex | Proportion of piriform resected (median): seizure-free versus not seizure-free group | 83 vs 52 % | human | 107 (46 seizure-free) | Galovic 2019 10.1001/jamaneurol.2019.0204 | abstract |
| IV. Cortex | Odds of seizure freedom when ≥50% of piriform is resected | ≈16 (95% CI 5–47) OR | human | 107 + 31 validation | Galovic 2019 10.1001/jamaneurol.2019.0204 | abstract |
| IV. Cortex | By structural connectivity: amygdala separates from piriform; piriform splits into frontal (posterior) / temporal (anterior); olfactory amygdala clusters with amygdala | k=2–10 clusters | human | 100 unrelated HCP participants (55 | NeuroImage 2024 (authors not verified; PII S1053811924002441) NR | abstract |
| IV. Cortex | A single piriform pyramidal cell synapses with more than 1,000 other cells | 1,000 cells | rat | NR | Vaughan & Jackson 2014 10.3389/fneur.2014.00259 | full |
| IV. Cortex | Chemosensitive (bicuculline) focus in primate frontal piriform | ≈2 mm | macaque | NR | Vaughan & Jackson 2014 10.3389/fneur.2014.00259 | full |
| IV. Cortex | Neuron density beneath 1 mm² of piriform surface versus neocortex | 59,000 vs 100,000 neurons/mm² | mouse | NR | Srinivasan & Stevens (bioRxiv) 10.1101/449447 | full |
| IV. Cortex | Scaling law of piriform layer 2 neuron number (n) with glomerulus number (g) | n = 2.08·g^(3/2) | mouse, rat, guinea pig, ferr | 6 species | Srinivasan & Stevens (bioRxiv) 10.1101/449447 | full |
| IV. Cortex | Number of synapses per glomerulus–layer 2 neuron pair | ≈1 (1.0002 ± 0.037) synapse | 6 mammalian species | 6 species | Srinivasan & Stevens (bioRxiv) 10.1101/449447 | full |
| IV. Cortex | Piriform glutamatergic neurons vary continuously in transcription (not in discrete types as in neocortex); many immature neurons | qualitative | mouse | NR | Zeppilli 2025 (Nat Neurosci 28:937) NR | abstract |
| IV. Cortex | Proportion of DCX+ immature neurons in layer II of human neocortex | ≈0.7 % of NeuN+ | human | 20 + 17 | Coviello 2022 10.3389/fnana.2022.851432 | full |
| IV. Cortex | NeuN area overlapping with Lewy bodies in the AON (Parkinson’s) | 8 % | human | NR | Villar-Conde 2022 10.3389/fnana.2022.907373 | abstract |
| IV. Cortex | Cytoarchitectonic map of the olfactory tubercle + islands of Calleja; medium spiny neurons present; high inter-individual variability | 10 brains | human | 10 brains | Poleksić 2022 (BrainComp abstract) NR | abstract |
| IV. Cortex | MeA, CoA, PAC defined from the Mai 2015 atlas (no histology) | 3 ROI | human | 25 (14 female), aged 25.5 | Noto 2021 10.3389/fnsys.2021.752320 | partial |
| IV. Cortex | Probabilistic amygdala map with 10 subdivisions; superficial/centromedial/basolateral groups by 15 receptor types | 10 subdivisions; 15 receptors | human | NR | Kedo 2018 10.1007/s00429-017-1577-x | abstract |
| IV. Cortex | Acquisition: 30 directions, b = 1,000, 2 mm voxels; CSD MRtrix3 | 30 directions | human | 10 (6 male, 4 female), aged 25–50 | Milardi 2017 10.3389/fnana.2017.00032 | full |
| IV. Cortex | Direct pathway from piriform, entorhinal, amygdala → medial OFC through the sublenticular white matter | qualitative | human | 10 | Milardi 2017 10.3389/fnana.2017.00032 | full |
| IV. Cortex | Piriform and amygdala connections within the ‘functional olfactory cortex network’ present in everyone | 100 % of people | human | 16 (aged 20–29) | Fjaeldstad 2017 10.1038/srep42534 | full |
| IV. Cortex | Connection to the thalamus (fOCN) left/right; disappears with grey-matter-only ROIs | 94 / 88 % of people | human | 16 | Fjaeldstad 2017 10.1038/srep42534 | full |
| IV. Cortex | Piriform–thalamus streamline count higher on the left; piriform–OFC higher on the right | directional | human | 38 | Thaploo 2022 10.1016/j.neuroimage.2022.119518 | abstract |
| IV. Cortex | Lateral olfactory stria longer on the left; medial olfactory stria inconsistent; no correlation between DTI and function | qualitative | human | 10 hemispheres; 25; 75 | Stenwall 2025 10.3390/brainsci15040368 | abstract |
| IV. Cortex | Amount of data in the olfactory ALE | 45 studies / 69 contrasts / 594 coordinates | human | 45 studies | Seubert 2013 (NeuroImage) 10.1016/j.neuroimage.2012.10.030 | abstract |
| IV. Cortex | Food-odour ALE: early olfactory region clusters left/right | 3,616 / 3,072 mm³ | human | 18 contrasts (food); 16 (non- | Oka 2023 10.3389/fnins.2023.1191617 | full |
| IV. Cortex | Right orbital sulcus grey-matter volume correlates positively with olfactory function | significant | human | 90 | Seubert 2013 (Cereb Cortex) 10.1093/cercor/bhs230 | abstract |
| IV. Cortex | Right OFC lesion → loss of conscious odour perception with ‘blind smell’ (left OFC still responds) | 1 case | human | 1 | Li 2010 10.1177/0956797610382121 | abstract |
| IV. Cortex | fMRI data: 160 odours, ~18 hours per person; coding dimensionality increases from piriform to OFC | 3 people × ~18 hours | human | 3 | Sagar 2023 10.1038/s41593-023-01414-4 | abstract |
| IV. Cortex | Piriform activated bilaterally; right OFC activated unilaterally | qualitative | human | NR | Zatorre 1992 10.1038/360339a0 | abstract |
| IV. Cortex | Proportion of olfactory sensations among responses to electrical stimulation of the insula | ≈1 % | human | NR | Roy-Côté 2021 10.3390/brainsci11020198 | full |
| IV. Cortex | Olfactory impairment after insular lesions: left 6/7 versus right 2/8 | 6/7 vs 2/8 patients | human | 16 (secondary citation) | Roy-Côté 2021 10.3390/brainsci11020198 | full |
| IV. Cortex | Olfactory sensations in patients with insular tumours: right 2/18, left 0/22 | 2/18 vs 0/22 patients | human | 40 | Roy-Côté 2021 10.3390/brainsci11020198 | full |
| IV. Cortex | MD lesions: normal sensitivity, discrimination, naming, recognition memory and pleasantness ratings; impaired olfactory attention | 6 lesion / 14 controls | human | 20 | Tham 2011 (Neurocase) 10.1080/13554794.2010.504728 | abstract |
| IV. Cortex | MD lesions: impaired olfactory attention, increased ‘oral capture’ | 4 patients | human | 4 + 2 control groups | Tham 2011 (Brain Cogn) 10.1016/j.bandc.2011.05.008 | abstract |
| IV. Cortex | Ventrolateral thalamic lesions: impaired odour threshold in the ipsilateral nostril | 15/15/15 thalamus/cerebellum/controls | human | 45 | Zobel 2010 10.1007/s00415-010-5656-7 | abstract |
| IV. Cortex | Forward MD→OFC coupling when attending to odours versus attending to sounds | 0.033 ± 0.02 vs −0.006 ± 0.01 DCM parameter | human | 12 (16 recruited, 4 excluded) | Plailly 2008 10.1523/JNEUROSCI.5607-07.2008 | partial |
| IV. Cortex | Modulation of the indirect pathway (via MD) greater than of the direct pathway | 0.097 ± 0.049 DCM parameter | human | 12 | Plailly 2008 10.1523/JNEUROSCI.5607-07.2008 | partial |
| IV. Cortex | Proportion of MD units responding to odours | 51 / 44 / 55 % | rat / cat / rabbit | NR | Courtiol & Wilson 2015 10.3389/fncir.2015.00049 | full |
| IV. Cortex | Odour identification impaired with resection on either side, no difference between left and right | p = 0.427 (free), 0.948 (cued) | human | 31 patients (17L/14R per abstract; 19/1 | Juran 2016 10.3389/fpsyg.2015.02015 | full |
| IV. Cortex | Temporal piriform activated bilaterally whichever nostril is stimulated; frontal piriform only on the right; entorhinal only on the left | qualitative | human | 20 | bioRxiv 2023 (authors not verified) 10.1101/2023.08.01.551475 | full |
| IV. Cortex | People with interhemispheric defects cannot localise odours | 3/6 people | human | 6 (+46 controls) | Lapointe 2025 10.1093/chemse/bjaf010 | abstract |
| IV. Cortex | The largest fibre group of the human anterior commissure arises from the inferior temporal lobe; targets include the amygdala and possibly the OFC | 6 lesion cases | human | 6 | Di Virgilio 1999 10.1007/s002210050593 | abstract |
| IV. Cortex | Anterior commissure diameter: callosal hypoplasia versus controls | 5.2 vs 1.8 mm | human | 1 + 9 | van Meer 2016 10.3389/fnsys.2016.00101 | full |
| IV. Cortex | Correlation of AAL ‘olfactory’ ROI volume with age | −0.586 r | human | 214 (53/66/95) | Alotaibi 2023 10.3389/fnhum.2023.1130200 | full |
| IV. Cortex | Women begin losing olfactory cortex volume (AAL) earlier, from the 4th decade | 4th decade | human | 214 | Alotaibi 2023 10.3389/fnhum.2023.1130200 | full |
| IV. Cortex | Correlation of UPSIT with entorhinal/perirhinal grey matter, left/right | 0.62 / 0.63 r | human | 30 (aged 51–77) | Segura 2013 NR | full |
| IV. Cortex | Additional grey-matter loss in olfaction-related regions (mean) | ≈0.7 % | human | 401 infected / 384 controls | Douaud 2022 10.1038/s41586-022-04569-5 | partial |
| IV. Cortex | Additional parahippocampal/perirhinal and entorhinal volume loss | 1.3–1.8 % | human | 785 | Douaud 2022 10.1038/s41586-022-04569-5 | partial |
| IV. Cortex | Baseline hippocampal volume predicts faster decline in odour identification over 15 years | β = 0.056 (CI 0.018–0.093) | human | 401 | Oltra 2025 (Front Aging Neurosci) 10.3389/fnagi.2025.1539508 | full |
| IV. Cortex | Pooled Hedges g for olfactory bulb volume in AD versus controls | −1.21 g | human | 6 studies; 152 AD / 166 controls | Jobin 2021 10.3390/brainsci11081010 | full |
| IV. Cortex | Number of independent samples on primary olfactory cortex volume in AD/MCI (too few to pool) | 3 samples | human | 3 samples | Jobin 2021 10.3390/brainsci11081010 | full |
| IV. Cortex | POC and hippocampal atrophy in MCI and AD | 27 CN / 21 MCI / 15 AD | human | 63 | Vasavada 2015 10.3233/JAD-141947 | abstract |
| IV. Cortex | Tau–olfaction association persists after adjusting for amyloid | T = 2.80, p = 0.006 | human | 155 | Diez 2024 10.1038/s41467-024-48462-3 | full |
| IV. Cortex | Sample sizes: UPSIT / tau PET / longitudinal tau PET / DWI | 418 / 155 / 89 / 82 people | human | 418 | Diez 2024 10.1038/s41467-024-48462-3 | full |
| IV. Cortex | Correlation of olfaction with PACC cognition: baseline / after ~2.5 years | 0.20 / 0.31 r | human | NR | Diez 2024 10.1038/s41467-024-48462-3 | full |
| IV. Cortex | Piriform tau increases in the order Aβ− < Aβ+ < MCI < AD; no increase in Parkinson’s | 94 (journal) / 92 (conference abstract) people | human | 92–94 | Taghavi 2024 10.1002/dad2.70040 | abstract |
| IV. Cortex | Odour identification score SCI / MCI / AD | 14.1 / 12.7 / 12.8 points (0–16) | human | 154 / 51 / 31 | Oltra 2025 (AAIC abstract) 10.1002/alz70862_109879 | abstract |
| IV. Cortex | Left parahippocampal region most strongly associated with olfactory decline; entorhinal not directly | 27 older / 27 young | human | 54 | Iizuka 2021 10.1002/brb3.2115 | abstract |
Yellow-shaded rows: facts that conflict with other sources (see Table 8). Access: full = full text; partial = part of the text; abstract = abstract only.
A monograph compiled from 259 sourced facts collected under a common protocol. Practical-implication sections are the compilers’ inferences. Diagrams are newly drawn from published data. Scientific reference material, not medical advice.