engleski

Attentional modulation of the M50 gating network

Identification of the topology and cortical dynamics of the M50 auditory gating network may advance understanding of the neural ability to inhibit redundant information since disruption of this ability is often associated with pathological conditions. This study challenges the accepted model of the M50 gating as a pre-attentive, automatic inhibitory process by investigating whether a voluntary attention directed at the second tone of a pair could compromise the gating out phenomenon at the cortical level. We used MEG recordings (Elekta Neuromag, Oy 306-channel whole- head system) acquired in a magnetically shielded room at the Biomagnetic Center in Jena, Germany and multi-dipole CSST method for spatio-temporal source localization were used to identify the M50 cortical network evoked within a paired-click paradigm in 19 healthy younger subjects. Two consecutive (ISI=500 ms) identical short tones (S1 and S2 ; duration=20ms ; f=1200Hz ; ITI=8±1ms) were used to evoke standard gating cortical responses. Directing attention toward S2 tone was assessed by the task to respond to a non-identical second tone of the gating pair (R= 1300Hz, p (S1R) = 0.3) in the second condition. Our results indicated the activation of 3-4 brain regions in a 30-100 ms time interval evoked within a classical passive paradigm, including bilateral superior temporal gyri (STG), lateral prefrontal (LPF) and parietal (PA) regions. Targeting attention toward the second tone activated orbitofrontal (OF) region in addition to bilateral STG and enhanced the M50 amplitude of the STG responses to the repeated tone (S2). Gating out phenomenon was evident only in the dynamics of the STG sources while PA, PF and OF generators didn't suppress their responses to the repeated tone. The classical cortical gating out ratio (S2/S1) in the dynamics of the STG sources was found to be 68% lower than in the engaging attention condition. Our novel finding demonstrating an attentional modulation of the dynamics and topology of the M50 gating network suggests using controlled attention as a potentially effective approach to reduce gating out phenomenon disorders that occurs in many pathological conditions and diseases such as schizophrenia, autism or ADHD.

magnetoencephalography (MEG); evoked auditory neuromagnetic fields; auditory processing; paired-click paradigm; auditory M50 component; gating out; attentional modulation; prefrontal cortex (PF); primary auditorx cortex (STG)

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