{"doi":"10.1073/pnas.2205301119","title":"The spectral sensitivity of human circadian phase resetting and melatonin suppression to light changes dynamically with light duration","abstract":"Human circadian, neuroendocrine, and neurobehavioral responses to light are mediated primarily by melanopsin-containing intrinsically-photosensitive retinal ganglion cells (ipRGCs) but they also receive input from visual photoreceptors. Relative photoreceptor contributions are irradiance- and duration-dependent but results for long-duration light exposures are limited. We constructed irradiance-response curves and action spectra for melatonin suppression and circadian resetting responses in participants exposed to 6.5-h monochromatic 420, 460, 480, 507, 555, or 620 nm light exposures initiated near the onset of nocturnal melatonin secretion. Melatonin suppression and phase resetting action spectra were best fit by a single-opsin template with lambda max at 481 and 483 nm, respectively. Linear combinations of melanopsin (ipRGC), short-wavelength (S) cone, and combined long- and medium-wavelength (L+M) cone functions were also fit and compared. For melatonin suppression, lambda max was 441 nm in the first quarter of the 6.5-h exposure with a second peak at 550 nm, suggesting strong initial S and L+M cone contribution. This contribution decayed over time; lambda max was 485 nm in the final quarter of light exposure, consistent with a predominant melanopsin contribution. Similarly, for circadian resetting, lambda max ranged from 445 nm (all three functions) to 487 nm (L+M-cone and melanopsin functions only), suggesting significant S-cone contribution, consistent with recent model findings that the first few minutes of a light exposure drive the majority of the phase resetting response. These findings suggest a possible initial strong cone contribution in driving melatonin suppression and phase resetting, followed by a dominant melanopsin contribution over longer duration light exposures.","journal":"Proceedings of the National Academy of Sciences","year":2022,"id":237157,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":63,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9588,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2022-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":858941,"name":"María Lovísa Ámundadóttir","orcid":"0000-0002-6066-6600","position":1,"is_corresponding":false},{"id":342319,"name":"Shadab A. Rahman","orcid":"0000-0002-8729-0500","position":2,"is_corresponding":false},{"id":301744,"name":"Shantha M. W. Rajaratnam","orcid":"0000-0001-7527-8558","position":3,"is_corresponding":false},{"id":859694,"name":"Melanie Rüger","orcid":null,"position":4,"is_corresponding":false},{"id":552027,"name":"George C. Brainard","orcid":"0000-0003-4472-5786","position":5,"is_corresponding":false},{"id":339460,"name":"Charles A. Czeisler","orcid":"0000-0002-7408-1849","position":6,"is_corresponding":false},{"id":858942,"name":"Marilyne Andersen","orcid":"0000-0001-8813-1184","position":7,"is_corresponding":false},{"id":858943,"name":"Joshua J. Gooley","orcid":"0000-0002-4830-3583","position":8,"is_corresponding":false},{"id":342321,"name":"Steven W. Lockley","orcid":"0000-0001-5209-2881","position":9,"is_corresponding":false},{"id":383583,"name":"Melissa A. St. Hilaire","orcid":"0000-0002-5700-8391","position":0,"is_corresponding":true}],"reference_count":70,"raw_metadata":null,"created_at":"2026-07-19T00:22:08.925400Z","pmid":"36508661","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}