Muscle contraction force and fatigue: effects on mismatch negativity Maria D. Evstigneeva a , Alexander A. Alexandrov a , Svend Erik Mathiassen b and Eugene Lyskov b Muscle load can affect the performance of concurrent cognitive task. This effect is often explained by limited resources in the voluntary attention system. To examine whether earlier stages of cognitive information processing might be affected, we recorded the mismatch negativity component (MMN) of the auditory event-related brain potential before, during and after sustained handgrip at 7 and 30% of maximal voluntary contraction. MMN is an index of automatic detection of a deviating auditory event. MMN was not affected by force level. However, its amplitude at fronto-central sites decreased during the fatiguing 30% contraction, while it tended to increase during the light 7% work. Thus, muscle fatigue may affect auditory information processing at preattentive and preconscious stages, which could modify cognitive performance. NeuroReport 00:000–000  c 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins. NeuroReport 2010, 00:000–000 Keywords: dual task, event-related potentials, force production, isometric contraction, mismatch negativity, muscle fatigue, preattentive auditory information processing a Department of Higher Nervous Activity and Psychophysiology, Saint Petersburg State University, Saint Petersburg, Russian Federation and b Centre for Musculoskeletal Research, University of Ga ¨vle, Ga ¨ vle, Sweden Correspondence to Maria D. Evstigneeva, Department of Higher Nervous Activity and Psychophysiology, Faculty of Biology and Soil Sciences, Saint Petersburg State University, Universitetskaja nab 7/9, Saint Petersburg 199034, Russian Federation Tel: +7921 389 23 67; fax: +7812 328 97 03; e-mail: maria.evstigneeva@gmail.com Received 25 August 2010 accepted 21 September 2010 Introduction Sustained muscle load and fatigue has been shown in some studies to impair cognitive task performance [1–4], while an improvement has also been suggested [1,5]. The neurophysiologic mechanisms underlying such associa- tions however, have not yet been systematically investi- gated. The voluntary attention system with its limited resources is often thought to be a bottleneck at which the interaction between the motor and cognitive processes takes place (e.g. [2,4]). When more effort has to be invested in maintaining a physical work load in spite of fatigue, fewer resources are available for cognitive tasks. On the other hand, as suggested by, for example, Bills [5], cognitive performance could also improve when carrying out a phsyically demanding task, either due to ‘nutritive’ effects following from an increase in vital processes such as blood supply and breathing, or/and because of direct neural interactions, including lowering of thresholds by afferent flow or preparatory activity from activated neuro- muscular systems. A useful investigatory tool for shedding some light on the association between motor and cognitive performance is the event-related brain potential (ERP) technique. Diff- erent ERP components are believed to reflect specific stages of perceptual, cognitive, and motor processes, including attention-related aspects. Earlier ERP research has shown that the amplitude of the P3b component appears to reflect voluntary attention resource allocation in a dual task, when individuals perform cognitive and motor task simultaneously [6]. Not only the voluntary attention level, however, but also earlier stages of information processing may be affected by muscle load and fatigue, with a modulated cognitive task performance as the result. To test the latter idea, we examined the effect of a sustained muscle contraction on the mismatch negativity (MMN) ERP component, which is believed to reflect the automatic, preattentive and preconscious, response to detectable changes in auditory stimulation, and to be involved in attention-switching mechanisms (for reviews see [7–9]). MMN is an en- hanced negativity in the ERP to rare ‘deviant’ acoustic events that occur in a sequence of regular ‘standard’ events, as compared with ERP to those ‘standards’, at a latency of 100–250 ms after standard-deviant divergence point. MMN appears even when no specific attention is paid to the stimuli. Thus, the examination of MMN may help to differentiate between early (more automatic) and later (more effort demanding) processes. A modulation of the MMN component during muscle contractions would indicate that force production and/or fatigue interferes with cognitive information processing at a very early, preattentive and preconscious stage. This study aimed at exploring early associations between force, fatigue and information processing by comparing the MMN before, during, and after sustained muscle contractions at two force levels, leading to different levels of fatigue. This study was carried out in Saint Petersburg State University, Universitetskaja nab 7/9, Saint Petersburg 199034, Russian Federation. Motor systems 1 0959-4965  c 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI: 10.1097/WNR.0b013e328340cc66 Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.