122-channel squid instrument for investigating the magnetic signals from the human brain

Ahonen, Antti; Hämäläinen, Matti S.; Kajola, M.; Knuutila, Jukka; Laine, Petteri; Lounasmaa, O. V.; Parkkonen, Lauri; Simola, J.; Tesche, C. D.

doi:10.1088/0031-8949/1993/t49a/033

Cited by 316 publications

(117 citation statements)

References 11 publications

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“…5 (Euroshield, Eura, Finland). The auditory evoked fields were recorded with a 122-channel MEG device (Neuromag, Helsinki, Finland;Ahonen et al 1993). Click stimuli (0.1-ms duration) were presented to the left ear at a rate of 10 Hz at 60 dB above an individually measured hearing threshold.…”

Section: Stimulus Design and Data Acquisitionmentioning

confidence: 99%

Serotonin Modulates Early Cortical Auditory Processing in Healthy Subjects. Evidence from MEG with Acute Tryptophan Depletion

Kähkönen

Ahveninen

Pennanen

et al. 2002

Neuropsychopharmacology

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We studied the effects of acute tryptophan depletion (ATD) on early cortical auditory processing. Middle-latency auditory evoked fields (MAEF) were investigated in 14 healthy subjects after 5 h of ATD or control mixture ingestion in a randomized, double-blinded, controlled crossover design study. MAEFs to monaural click stimuli (0.1-ms duration) were recorded with a 122-channel neuromagnetometer. Total plasma tryptophan (Trp),Low brain serotonin (5-HT) levels and function have been implicated in various psychopathologies including depression and anxiety. Acute tryptophan depletion (ATD) is a dietary intervention that rapidly lowers plasma tryptophan (Trp) and alters 5-HT synthesis, metabolism, and release in animals and humans (Young et al. 1985;Nishizawa et al. 1997;Stancampiano et al. 1997;Carpenter et al. 1998). It involves the administration of an amino acid mixture that lacks Trp, the amino acid precursor of serotonin. The effect of ATD on 5-HT synthesis and metabolism is twofold (Young et al. 1985). First, decline in plasma Trp occurs because the Trpdeficient amino acid mixture promotes synthesis of new proteins. Trp incorporated into protein comes from blood and tissue pools, and therefore its concentration in plasma and brain falls (Biggio et al. 1974;Gessa et al. Stancampiano et al. 1997). Magnetoencephalography (MEG) is a method for the measurement of extracranial magnetic fields produced by ionic current flow generated mainly by cortical pyramidal cells. MEG is a non-invasive method for functional brain studies with temporal resolution as high as electroencephalography (EEG), but with more accurate source localization . Because of cortical folding in the Sylvian fissure, MEG is ideally suited for the localization and measurement of supratemporal auditory cortical activity .Auditory evoked magnetic potentials (AEP) and fields (AEF), which allow the investigation underlying auditory processing, can be obtained by averaging EEG or MEG epochs time-locked to the presentation of auditory stimuli. The earliest cortical AEFs, the middlelatency AEFs (MAEFs), occur at about 20-70 ms from stimulus onset. The MAEFs are composed of several distinct deflections, with Pam peaking at approximately 30 ms and Nbm at about 45 ms.There is evidence to suggest that serotonergic activity may modulate auditory evoked potentials (Hegerl and Juckel 1993;Juckel et al. 1997;Dierks et al. 1999) and background EEG frequencies (Knott et al. 1999). The sound intensity dependence of auditory N1/P2 amplitude has been suggested to be a specific indicator of serotonin function (Hegerl and Juckel 1993;Juckel et al. 1997). Reduced serotonin function leads to higher intensity dependence of N1/P2 amplitude and vice versa. However, Dierks et al. (1999) were not able to confirm these findings using ATD in healthy subjects. In contract, this study showed that ATD decreases the intensity dependence of N1/P2 amplitudes. In the recent ATD study using a 52-g amino acid challenge, Hughes et al. (2000) found no changes in auditory N1, P2, or P3 ampl...

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Section: Stimulus Design and Data Acquisitionmentioning

confidence: 99%

Serotonin Modulates Early Cortical Auditory Processing in Healthy Subjects. Evidence from MEG with Acute Tryptophan Depletion

Kähkönen

Ahveninen

Pennanen

et al. 2002

Neuropsychopharmacology

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“…The ERF and ERP were recorded with a 122 channel MEG (Neuromag, Finland; Ahonen et al 1993) and 64-channel EEG (sampling rate 1 kHz) in each. Each two-channel sensor unit in MEG measured two independent magnetic field gradient components ∂ B z / ∂ x and ∂ B z / ∂ y, the z-axis being normal to the scalp.…”

Section: Data Acquisitionmentioning

confidence: 99%

Effects of Haloperidol on Selective Attention A Combined Whole-Head MEG and High-Resolution EEG Study

Kähkönen

2001

Neuropsychopharmacology

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We used 122-channel magnetoencephalography (MEG) and 64-channel electroencephalogrphy (EEG) simultaneously to study the effects of dopaminergic transmission on human selective attention in a randomized, double-blind placebo-controlled cross-over design. A single dose of dopamine D2 receptor antagonist haloperidol (2 mg) or placebo was given orally to 12 righthanded healthy volunteers 3 hours before measurement. In a dichotic selective attention task, subjects were presented with two trains of standard (700 Hz to the left ear, 1,100Hz to the right ear) and deviant (770 and 1,210 Hz, respectively) Selective attention refers to the ability to attend to relevant information simultaneously ignoring irrelevant information (Posner and Boies 1971). The neural basis of selective attention can be noninvasively studied with high temporal resolution using event-related potentials (ERP) and magnetic fields (ERF), which are electroencephalogram (EEG) or magnetoencephalogram (MEG) changes time-locked to the presentation of external stimuli (Hari and Lounasmaa 1989;Näätänen et al. 1992 (Näätänen 1992). MEG studies of selective attention have, in turn, indicated that the amplitude of the N1m, elicited at about 100 ms poststimulus, is increased by selective attention, but the PN seems to be less visible for the MEG than EEG (Fujiwara et al. 1998). The mismatch negativity (MMN), or magnetic counterpart MMNm, is a pre-attentive ERP/ERF component elicited by any change in a sequence of frequent standard tones reflecting automatic detection and orientation to sudden environmental changes (Alho 1995;Näätänen 1992;Näätänen et al. 1978;Tiitinen et al. 1994).Only a few studies have been devoted to drug effects on selective attention indexing by the PN. The NMDA receptor antagonist ketamine, alcohol, and adrenocorticotropic hormone (ACTH) have been shown to reduce PN (Smolnik et al. 1999;Hirvonen et al. 2000;Oranje et al. 2000). Opposite effects were observed after the administration of the antagonist of GABA receptors flumatzenil and cholecystokinin analog ceruletide (Schreiber et al. 1995;Smolnik et al. 1998). Anesthetic gas nitrous oxide (N 2 O) and adrenergic alpha 2-antagonist atipamezole had no effects on the PN (Mervaala et al. 1993;Pang and Fowler 1999). Shelley et al. (1997) studied effects of another adrenergic alpha 2-receptor agonist clonidine and dopamine D2 receptor antagonist droperidol on ERP indices of selective attention. They found that clonidine increased and droperidol decreased the PN.Haloperidol is a potent, partially selective dopamine D 2 receptor antagonist, which is widely used to treat psychotic disorders in clinical practice. Haloperidol affects spontaneous EEG activity, increasing slow waves and decreasing alpha and beta activity in healthy humans (McClelland et al. 1990). There is also evidence that haloperdiol decreases the transient 40 Hz response elicited by selectively attended tones (Ahveninen et al. 2000).Our study was designed to investigate with simultaneous MEG and EEG recordings whether haloperi...

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“…MEG/EEG was recorded (passband 0.03 -100 Hz, sampling rate 394 Hz) in a magnetically shielded room (Euroshield Ltd., Eura, Finland), where the subjects sat with their head inside a whole-head MEG instrument with 122 planar gradiometers [1] (4-D Neuroimaging Oy, Finland). Each two-channel MEG sensor unit measures two independent magnetic-field gradient components, dB z /dx and dB z / dy, the z-axis being normal to the local helmet surface.…”

mentioning

confidence: 99%

Auditory selective attention modulated by tryptophan depletion in humans

Ahveninen¹,

Jä̈askëlainen²,

Pennanen³

et al. 2003

Neuroscience Letters

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122-channel squid instrument for investigating the magnetic signals from the human brain

Cited by 316 publications

References 11 publications

Serotonin Modulates Early Cortical Auditory Processing in Healthy Subjects. Evidence from MEG with Acute Tryptophan Depletion

Serotonin Modulates Early Cortical Auditory Processing in Healthy Subjects. Evidence from MEG with Acute Tryptophan Depletion

Effects of Haloperidol on Selective Attention A Combined Whole-Head MEG and High-Resolution EEG Study

Auditory selective attention modulated by tryptophan depletion in humans

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