A combined TMS-EEG study of short-latency afferent inhibition in the motor and dorsolateral prefrontal cortex

Abstract

Combined transcranial magnetic stimulation and electroencephalography (TMS-EEG) enables noninvasive neurophysiological investigation of the human cortex. A TMS paradigm of short-latency afferent inhibition (SAI) is characterized by attenuation of the motor-evoked potential (MEP) and modulation of N100 of the TMS-evoked potential (TEP) when TMS is delivered to motor cortex (M1) following median nerve stimulation. SAI is a marker of cholinergic activity in the motor cortex; however, the SAI has not been tested from the prefrontal cortex. We aimed to explore the effect of SAI in dorsolateral prefrontal cortex (DLPFC). SAI was examined in 12 healthy subjects with median nerve stimulation and TMS delivered to M1 and DLPFC at interstimulus intervals (ISIs) relative to the individual N20 latency. SAI in M1 was tested at the optimal ISI of N20 + 2 ms. SAI in DLPFC was investigated at a range of ISI from N20 + 2 to N20 + 20 ms to explore its temporal profile. For SAI in M1, the attenuation of MEP amplitude was correlated with an increase of TEP N100 from the left central area. A similar spatiotemporal neural signature of SAI in DLPFC was observed with a marked increase of N100 amplitude. SAI in DLPFC was maximal at ISI N20 + 4 ms at the left frontal area. These findings establish the neural signature of SAI in DLPFC. Future studies could explore whether DLPFC-SAI is neurophysiological marker of cholinergic dysfunction in cognitive disorders.

Maturation changes the excitability and effective connectivity of the frontal lobe: A developmental TMS–EEG study

“…Contrary to our hypothesis, an equally complex EEG response was also evoked in children and adolescents at the site of stimulation, although the latencies and topography of the components differed between the groups. The waveform recorded in the participants of our study resembles the sequence of P13‐N18‐P30‐N45‐P60‐N100‐P180‐N280 components elicited by TMS of the adult motor cortex (Ferreri, Pasqualetti, et al, ), and is consistent with the findings of previous frontal cortex TMS studies (Kähkönen et al, ; Lioumis et al, ; Massimini et al, ; Noda et al, ; Rogasch et al, ). We did not find amplitude differences in early TEPs between the age groups, and only a minor difference in the early part of GMFP, but the late P180 was significantly larger in children than in adults, and there was also a trend of the response in children being larger compared to adolescents.…”

“…Both the dorsolateral frontal cortex Fitzgerald et al, 2008;Kähkönen et al, 2004;Lioumis, Kicic, Savolainen, Mäkelä, & Kähkönen, 2009;Rogasch et al, 2014) and superior frontal cortex or premotor area (Casarotto et al, 2011;Ferrarelli et al, 2008;Massimini et al, 2005;Zanon, Battaglini, Jarmolowska, Pizzolato, & Busan, 2013) have been targeted. Despite this methodological difference, a sequence containing deflections (named after their latency and polarity; N = negative, P = positive) at around 30 ms (P30), 40-50 ms (N45), 60 ms (P60), 100-120 ms (N100), and 160-190 ms (P180) is frequently reported in response to frontal cortex stimulation (Kähkönen, Komssi, Wilenius, & Ilmoniemi, 2005a;Lioumis et al, 2009;Noda et al, 2016;Rogasch et al, 2014). In addition, some studies have found activity as early as at 10 ms (Massimini et al, 2005) and at around 20 ms (Lioumis et al, 2009;Massimini et al, 2005), and as late as at 280 ms (Massimini et al, 2005;Rogasch et al, 2014;Rogasch et al, 2015).…”

Characterization of Glutamatergic and GABAA-Mediated Neurotransmission in Motor and Dorsolateral Prefrontal Cortex Using Paired-Pulse TMS–EEG

“…We performed an exploratory correlational analysis between MEP measures and TEP amplitude changes in DLPFC, however no additional correlations were observed. Similarly, other studies have reported an absence of correlations between modulation of specific TEP components in M1 compared to other areas (Farzan et al, 2009(Farzan et al, , 2013Noda et al, 2016), and in the present study this may reflect a difference in the strength of SICI and ICF in M1 compared to DLPFC. This could perhaps be due to differences in GABA A or glutamatergic tone.…”

Reduced Prefrontal Short—Latency Afferent Inhibition in Older Adults and Its Relation to Executive Function: A TMS-EEG Study

“…Our previously published data contain details on the TEP analyses of the young participants (Noda et al, 2016). Further, there was no gender difference on the modulation of TEPs by M1-SAI paradigm.…”