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Povezava med osnovno fiziologijo in različnimi kognitivnimi stanji, kot je pozornost, ni povsem razumljena in pojasnjena. Dosti študij je sicer proučevalo vpliv pozornosti na senzorični sistem, vpliv pozornosti na motorični sistem pa ni tako jasen. Pozornost ima pomemben vpliv na motorični sistem, in sicer na sam proces gibanja, na motorično učenje in na motorični spomin. Opažanja pri zdravih ljudeh, pri profesionalnih športnikih ter klinična opažanja pri nevroloških bolnikih nakazujejo, da je vpliv pozornosti na gibanje kompleksen in večplasten. Pri zdravih ljudeh gibanje večinoma poteka brez vpliva pozornosti na izvajanje giba oz. »avtomatično«, pri čemer lahko ima zavestno usmerjanje pozornosti na neko nalogo negativen vpliv na motoriko. Pri nevroloških bolnikih z motnjami gibanja odvračanje pozornosti od nehotenih zgibkov le-te poudari, medtem ko usmerjanje pozornosti na hoteno gibanje izboljša hojo in pospeši gibe, ki so zaradi bolezni upočasnjeni. Primarna motorična skorja je osnovna živčna enota za izvajanje hotenih gibov, in sicer na osnovi informacij, ki jih dobiva iz drugih delov možganov. Pozornost lahko vpliva na motorično skorjo preko povezav z drugimi področji možganske skorje in povezav z bazalnimi gangliji, prav tako pa tudi preko difuznih modulatornih sistemov, ki skrbijo za povečanje splošne vzburjenosti možganov. Transkranialna magnetna stimulacija (TMS) je nevrofiziološka metoda, s katero lahko preučujemo vpliv pozornosti na motoriko preko spremljanja elektrofizioloških parametrov primarne motorične skorje, odvisno od eksperimentalnega manipuliranja s pozornostjo. Zanimalo nas je, ali različne oblike selektivne pozornosti vplivajo na TMS-parametre vzdražljivosti primarne motorične skorje in ali je kakšna razlika med različnimi senzoričnimi modalnostmi. V ta namen so zdravi preiskovanci pozornost usmerjali na vidno, slušno in somatosenzorično nalogo za pozornost (naloga »oddball«). Medtem smo izvedli različne TMS-meritve, kot so motorični evocirani potenciali, motorični prag v mirovanju in aktivni motorični prag, krivulja vzdražljivosti, parametri intrakortikalne inhibicije in facilitacije. Ugotovili smo, da različne senzorične modalnosti selektivne pozornosti v mirovanju nimajo pomembnega vpliva na TMS-parametre primarne motorične skorje. Naša preliminarna raziskava nakazuje, da je motorična kontrola relativno neobčutljiva na dražljaje iz okolja, ki niso relevantni za gibanje. The link between basic physiology and its modulation by cognitive states, such as attention, is poorly understood. There have been a large number of studies of the effects of attention on sensory systems but the effects of attention on motor system are not well known. Attention modulates motor system through movement processing, motor learning and motor memory. In healthy people everyday movements and motor actions usually don't require much attention and can happen »automatically« excessive focus on the details of a task can acutally be associated with poor performance. The effetct of attention on motor system becomes apparent when patients with movement disorders or professional sportsmen describe experiences with changing their attention focus and the fundamental effect that this has on their motor movement. Some people with movement disorders can actually minimize tremors and improve movements when they pay attention to the affected part of the body. The primary motor cortex (M1) lies along the precentral gyrus, and generates signals that control the execution of movements. Attention can affect primary motor cortex through its connections to other brain regions, thorugh connections to basal ganglia pr through diffuse modulatory brain systems. Transcranial magnetic stimulation is a neurophysiological method that allows us to investigate whether attention does have an impact on motor system – by observing changes of electrophysiological parameters of M1 in different conditions. In our study we investigated whether different sensory modalities of selective attention have an influence on M1 excitability (by looking at basic TMS parameters) and whether this influence differs between modalities. Healthy participants had to focus ther attention on three-stimuli oddball tasks while basic TMS measurements were taken. Visual oddball task, auditory oddball task and somatosensory oddball task were compared to control condition (no attention was required). For each condition different TMS parameters were measured: motor evoked potentials, recruitment curve, active recruitment curve, cortical silent period, short interval intracortical inhibition and intracortical facilitation. We concluded that different sensory modalities of selective attention do not have significant influence on primary motor cortex excitability parameters. Preliminary results show that motor control is relatively unaffected by stimuli from environment, if the stimuli is not relevant to the movement. |
