Spatial Attention Influences Plasticity Induction in the Motor Cortex

• ¹ The University of Queensland, Queensland Brain Institute, Australia
• ² The University of Queensland, The School of Psychology, Australia
• ³ The University of Queensland, School of Human Movement Studies, Australia
• ⁴ The University of Queensland , Queensland Brain Institute and School of Psychology, Australia

It is widely accepted that alterations in the strength of communication between neurons, or 'Hebbian' (synaptic) plasticity, plays a major role in the capacity of the adult brain to adapt. Such plasticity is critical for responding to changes in sensory input, learning new skills and behaviours, and recovering from injury to the nervous system. Numerous physiological influences on synaptic plasticity have now been identified, but little is known about how plasticity is affected by cognitive processes. Here, we investigated the influence of visual spatial attention on plasticity induced by external stimulation of the motor cortex. Transcranial magnetic stimulation (TMS) and a paired associative stimulation (PAS) procedure were used to alter functional responses in the thumb area of the primary motor cortex. In different experiments PAS was used to induce either an increase or a decrease in cortical excitability, as indexed by the amplitude of motor-evoked potentials. These PAS-induced effects reflect, respectively, long-term potentiation (LTP)-like and long-term depression (LTD)-like synaptic plasticity. During the induction of plasticity, participants focused their attention on one of two visual stimulus streams located adjacent to each hand. When participants attended to visual stimuli located near the left thumb, which was targeted by the plasticity procedure, LTP-like increases in excitability were enhanced relative to when they attended instead to stimuli located near the right thumb. In contrast, LTD-like decreases in excitability were reduced when attention was directed toward the visual stimuli located near the left, relative to the right, thumb. These findings suggest that voluntary attention can exert an important influence on the functional organisation of the human cortex by both enhancing LTP-like plasticity and suppressing LTD-like effects.