{"id":{"repo_id":"aachen","oai_identifier":"oai:publications.rwth-aachen.de:60264"},"canonical_url":"https://search.dev.ndltd.org/etd/aachen/oai:publications.rwth-aachen.de:60264","repository":{"repo_id":"aachen","name":"RWTH Aachen University","base_url":"https://publications.rwth-aachen.de/oai2d"},"display":{"title":"Zirkadiane Modulation hochfrequenter SEP-Komponenten (600 Hz) nach Medianusstimulation in Abhängigkeit von tonischer alertness","abstract":"Human somatosensory evoked potentials (SEP) after median nerve stimulation contain a low-amplitude (< 500 nV) high-frequency (~ 600 Hz) burst of repetitive oscillations superimposed onto the primary cortical response “N20”, which can be obtained by digitally filtering the wide-band SEPs. Previous EEG- and MEG-studies indicated these high-frequency oscillations (HFOs) to reflect at least in part activity generated at the thalamus and in the thalamocortical radiation. Since the thalamus is involved in regulating alertness and arousal, the present study aimed to characterize the effects of circadian fluctuations of alertness on HFOs in awake humans. Bilaterally evoked median nerve SEPs were recorded in 11 healthy human subjects at four time points (day I: 8 a.m., 4 p.m., day II: 4 a.m., 8 a.m.) during a 24 hours waking period by using constant current square wave pulses at the right and left wrist (0.2 ms width) with an intensity of twice the motor threshold and a repetition rate of 7 Hz (3.5 Hz per limb). Responses were recorded using a 12-channel arrangement (reference Fz,) with electrode density focused around CP3 and CP4 (somatosensory cortex). Parallel to SEP recordings a reaction time task was performed to describe the level of alertness more objectively. By means of digital filtering the low frequency N20 as well as the HFOs could be obtained and evaluated; for the latter was carried out a time frequency-analysis aside from the conventional single-channel- analysis. Low-frequency SEP components showed no major circadian effects except for a slight latency prolongation during night recordings. In contrast, HFOs were significantly attenuated in amplitude and decreased in frequency at night in comparison to the first morning session, recovering partially at the second morning. In parallel, mean reaction times were significantly prolonged during the night recordings. A control experiment with decreasing body temperature about 0,6°C in two test subjects indicated that the HFO attenuation at night is unrelated to the circadian decrease of temperature. In conclusion, there seems to be an influence on the high-frequency part of early median nerve SEP by modulating the level of intrinsic alertness within a 24-hour waking period. These results fit with the hypothesis that HFOs in awake human subjects contain a component that reflect an vigilance-dependent signal, possibly generated at the thalamic level in the somatosensory relay nucleus, modulated by the reticular nucleus and transmitted to the primary somatosensory cortex.","abstract_html":"Human somatosensory evoked potentials (SEP) after median nerve stimulation contain a low-amplitude (&lt; 500 nV) high-frequency (~ 600 Hz) burst of repetitive oscillations superimposed onto the primary cortical response “N20”, which can be obtained by digitally filtering the wide-band SEPs. Previous EEG- and MEG-studies indicated these high-frequency oscillations (HFOs) to reflect at least in part activity generated at the thalamus and in the thalamocortical radiation. Since the thalamus is involved in regulating alertness and arousal, the present study aimed to characterize the effects of circadian fluctuations of alertness on HFOs in awake humans. Bilaterally evoked median nerve SEPs were recorded in 11 healthy human subjects at four time points (day I: 8 a.m., 4 p.m., day II: 4 a.m., 8 a.m.) during a 24 hours waking period by using constant current square wave pulses at the right and left wrist (0.2 ms width) with an intensity of twice the motor threshold and a repetition rate of 7 Hz (3.5 Hz per limb). Responses were recorded using a 12-channel arrangement (reference Fz,) with electrode density focused around CP3 and CP4 (somatosensory cortex). Parallel to SEP recordings a reaction time task was performed to describe the level of alertness more objectively. By means of digital filtering the low frequency N20 as well as the HFOs could be obtained and evaluated; for the latter was carried out a time frequency-analysis aside from the conventional single-channel- analysis. Low-frequency SEP components showed no major circadian effects except for a slight latency prolongation during night recordings. In contrast, HFOs were significantly attenuated in amplitude and decreased in frequency at night in comparison to the first morning session, recovering partially at the second morning. In parallel, mean reaction times were significantly prolonged during the night recordings. A control experiment with decreasing body temperature about 0,6°C in two test subjects indicated that the HFO attenuation at night is unrelated to the circadian decrease of temperature. In conclusion, there seems to be an influence on the high-frequency part of early median nerve SEP by modulating the level of intrinsic alertness within a 24-hour waking period. These results fit with the hypothesis that HFOs in awake human subjects contain a component that reflect an vigilance-dependent signal, possibly generated at the thalamic level in the somatosensory relay nucleus, modulated by the reticular nucleus and transmitted to the primary somatosensory cortex.","abstract_has_math":false,"creators":["Seiller, Melanie"],"institution":"Publikationsserver der RWTH Aachen University","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Buchner, Helmut"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2005,"date_issued":"2005","date_published":"2005","updated_at":"2026-07-30T19:42:56Z","subjects":["info:eu-repo/classification/ddc/610","Medizin","somatosensorisch evozierte Potentiale","hochfrequente Oszillationen (600 Hz)","alertness"],"languages":["ger"],"rights":["info:eu-repo/semantics/openAccess"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121987%22"],"render_values":[{"text":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121987%22","href":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121987%22","code":true}]}]},"links":{"outbound_url":"https://publications.rwth-aachen.de/record/60264","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Buchner, Helmut"]},{"key":"dc:creator","label":"Author","values":["Seiller, Melanie"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:coverage","label":"Dc Coverage","values":["DE"]},{"key":"dc:date","label":"Dc Date","values":["2005"]},{"key":"dc:publisher","label":"Institution","values":["Publikationsserver der RWTH Aachen University"]},{"key":"dc:relation","label":"Dc Relation","values":["info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-12374"]},{"key":"dc:type","label":"Dc Type","values":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["info:eu-repo/classification/ddc/610","Medizin","somatosensorisch evozierte Potentiale","hochfrequente Oszillationen (600 Hz)","alertness"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["ger"]},{"key":"dc:rights","label":"Dc Rights","values":["info:eu-repo/semantics/openAccess"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/record/60264","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121987%22"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Human somatosensory evoked potentials (SEP) after median nerve stimulation contain a low-amplitude (< 500 nV) high-frequency (~ 600 Hz) burst of repetitive oscillations superimposed onto the primary cortical response “N20”, which can be obtained by digitally filtering the wide-band SEPs. Previous EEG- and MEG-studies indicated these high-frequency oscillations (HFOs) to reflect at least in part activity generated at the thalamus and in the thalamocortical radiation. Since the thalamus is involved in regulating alertness and arousal, the present study aimed to characterize the effects of circadian fluctuations of alertness on HFOs in awake humans. Bilaterally evoked median nerve SEPs were recorded in 11 healthy human subjects at four time points (day I: 8 a.m., 4 p.m., day II: 4 a.m., 8 a.m.) during a 24 hours waking period by using constant current square wave pulses at the right and left wrist (0.2 ms width) with an intensity of twice the motor threshold and a repetition rate of 7 Hz (3.5 Hz per limb). Responses were recorded using a 12-channel arrangement (reference Fz,) with electrode density focused around CP3 and CP4 (somatosensory cortex). Parallel to SEP recordings a reaction time task was performed to describe the level of alertness more objectively. By means of digital filtering the low frequency N20 as well as the HFOs could be obtained and evaluated; for the latter was carried out a time frequency-analysis aside from the conventional single-channel- analysis. Low-frequency SEP components showed no major circadian effects except for a slight latency prolongation during night recordings. In contrast, HFOs were significantly attenuated in amplitude and decreased in frequency at night in comparison to the first morning session, recovering partially at the second morning. In parallel, mean reaction times were significantly prolonged during the night recordings. A control experiment with decreasing body temperature about 0,6°C in two test subjects indicated that the HFO attenuation at night is unrelated to the circadian decrease of temperature. In conclusion, there seems to be an influence on the high-frequency part of early median nerve SEP by modulating the level of intrinsic alertness within a 24-hour waking period. These results fit with the hypothesis that HFOs in awake human subjects contain a component that reflect an vigilance-dependent signal, possibly generated at the thalamic level in the somatosensory relay nucleus, modulated by the reticular nucleus and transmitted to the primary somatosensory cortex."]},{"key":"dc:source","label":"Dc Source","values":["Aachen : Publikationsserver der RWTH Aachen University 108 S. : Ill., graph. Darst. (2005). = Aachen, Techn. 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By means of digital filtering the low frequency N20 as well as the HFOs could be obtained and evaluated; for the latter was carried out a time frequency-analysis aside from the conventional single-channel- analysis. Low-frequency SEP components showed no major circadian effects except for a slight latency prolongation during night recordings. In contrast, HFOs were significantly attenuated in amplitude and decreased in frequency at night in comparison to the first morning session, recovering partially at the second morning. In parallel, mean reaction times were significantly prolonged during the night recordings. A control experiment with decreasing body temperature about 0,6°C in two test subjects indicated that the HFO attenuation at night is unrelated to the circadian decrease of temperature. In conclusion, there seems to be an influence on the high-frequency part of early median nerve SEP by modulating the level of intrinsic alertness within a 24-hour waking period. 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Hochsch., Diss., 2005"],"dc:subject":["info:eu-repo/classification/ddc/610","Medizin","somatosensorisch evozierte Potentiale","hochfrequente Oszillationen (600 Hz)","alertness"],"dc:title":["Zirkadiane Modulation hochfrequenter SEP-Komponenten (600 Hz) nach Medianusstimulation in Abhängigkeit von tonischer alertness"],"dc:type":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]},"updated_at":"2026-07-30T19:42:56Z"}