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Recent studies which separate oscillatory and aperiodic components of electrophysiological power spectra have highlighted a relationship between aperiodic activity and functional brain states. Studies in both animal models and humans suggest that the aperiodic slope of electrophysiological power spectra reflects the local balance of excitatory:inhibitory (E:I) synaptic transmission. Aperiodic slope varies across individuals, brain states, and clinical populations, which may reflect important differences in E:I balance. However, there is currently a lack of evidence linking aperiodic slope to other measures of excitation and inhibition in the human brain. Here, we show that flatter (less steep) aperiodic slopes from human electroencephalography (EEG) are associated with higher concentrations of the excitatory neurotransmitter glutamate measured with 7 tesla magnetic resonance spectroscopy (MRS) in the occipital lobe at rest. This suggests that individual differences in aperiodic neural activity reflect cortical glutamate concentrations, providing important insight for understanding changes in neural excitation across brain states and neuropsychiatric populations (e.g., schizophrenia) where glutamatergic function may differ. Our results support the use of aperiodic slope as a non-invasive marker for excitatory tone in the human brain.<\/jats:p>","DOI":"10.1101\/2025.05.15.654118","type":"posted-content","created":{"date-parts":[[2025,5,21]],"date-time":"2025-05-21T00:25:12Z","timestamp":1747787112000},"source":"Crossref","is-referenced-by-count":2,"title":["Aperiodic slope reflects glutamatergic tone in the human brain"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9139-2246","authenticated-orcid":false,"given":"Aislin A.","family":"Sheldon","sequence":"first","affiliation":[{"name":"Department of Psychiatry & Behavioral Sciences, University of Minnesota, Minneapolis, MN"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5534-9929","authenticated-orcid":false,"given":"Hannah R.","family":"Moser","sequence":"additional","affiliation":[{"name":"Department of Psychiatry & Behavioral Sciences, University of Minnesota, Minneapolis, MN"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kamar S.","family":"Abdullahi","sequence":"additional","affiliation":[{"name":"Department of Psychiatry & Behavioral Sciences, University of Minnesota, Minneapolis, MN"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Karly D.","family":"Allison","sequence":"additional","affiliation":[{"name":"Department of Psychiatry & Behavioral Sciences, University of Minnesota, Minneapolis, MN"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carter B.","family":"Mulder","sequence":"additional","affiliation":[{"name":"Department of Psychiatry & Behavioral Sciences, University of Minnesota, Minneapolis, MN"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4020-6380","authenticated-orcid":false,"given":"Samantha A.","family":"Montoya","sequence":"additional","affiliation":[{"name":"Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2782-0856","authenticated-orcid":false,"given":"Scott R.","family":"Sponheim","sequence":"additional","affiliation":[{"name":"Veterans Affairs Medical Center, University of Minnesota, Minneapolis, MN"},{"name":"Department of Psychiatry & Behavioral Sciences, University of Minnesota, Minneapolis, MN"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4727-2447","authenticated-orcid":false,"given":"Ma\u0142gorzata","family":"Marja\u0144ska","sequence":"additional","affiliation":[{"name":"Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8252-8607","authenticated-orcid":false,"given":"Michael-Paul","family":"Schallmo","sequence":"additional","affiliation":[{"name":"Department of Psychiatry & Behavioral Sciences, University of Minnesota, Minneapolis, MN"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026041122430148000_2025.05.15.654118v1.1","doi-asserted-by":"publisher","DOI":"10.1016\/J.NEURON.2019.11.011"},{"key":"2026041122430148000_2025.05.15.654118v1.2","doi-asserted-by":"publisher","DOI":"10.1038\/nn2035"},{"key":"2026041122430148000_2025.05.15.654118v1.3","doi-asserted-by":"publisher","DOI":"10.1113\/JP274986"},{"key":"2026041122430148000_2025.05.15.654118v1.4","doi-asserted-by":"publisher","DOI":"10.1016\/j.neuron.2013.03.017"},{"key":"2026041122430148000_2025.05.15.654118v1.5","doi-asserted-by":"publisher","DOI":"10.1016\/j.neuron.2012.03.036"},{"key":"2026041122430148000_2025.05.15.654118v1.6","doi-asserted-by":"publisher","DOI":"10.1016\/j.jneumeth.2007.11.008"},{"key":"2026041122430148000_2025.05.15.654118v1.7","doi-asserted-by":"publisher","DOI":"10.1038\/nature13321"},{"key":"2026041122430148000_2025.05.15.654118v1.8","doi-asserted-by":"publisher","DOI":"10.1038\/s41593-020-00744-x"},{"key":"2026041122430148000_2025.05.15.654118v1.9","doi-asserted-by":"publisher","DOI":"10.1016\/j.tics.2014.04.003"},{"key":"2026041122430148000_2025.05.15.654118v1.10","doi-asserted-by":"publisher","DOI":"10.1016\/j.neu-roimage.2017.06.078"},{"key":"2026041122430148000_2025.05.15.654118v1.11","doi-asserted-by":"crossref","unstructured":"Deodato, M. & Melcher, D. 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