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"Thinking is easy, acting is difficult, and to put one's thoughts into action is the most difficult thing in the world" - Johann Wolfgang von Goethe

Perception, cognition, and action selection have traditionally been considered (and studied) as largely independent processes. The brain, however, is unlikely to adhere to these text book divisions, and while functional specialization is critical, activity deployment in the brain does not follow these boundaries.


We are interested in how the brain ultimately transforms sensory information, decisions, or predictions about the world into actions. This addresses one of the unresolved questions that have bedazzled neuroscientists ever since Charles Sherrington provided the first detailed ‘motor map’ of the primate motor cortex: How does our brain transform our thoughts into actions?

Addressing this question is important for understanding how the brain enables interaction with an ever-changing and uncertain environment, and thus what may cause decline in action selection abilities during aging, and pathological conditions that are characterised by impairments of both action and cognition, such as Parkinson’s disease, Depression, or Stroke.

To address these questions through an integrated use of different yet complementary state-of-the-art techniques of complementary strengths, including functional neuroimaging (fMRI, EEG), neurostimulation (tDCS, TMS), computational modelling and model-based analyses, and interventional approaches (drug, neurostimulation, concurrent TMS-fMRI) to study the links between "decision making" and action selection in the human brain.

Mechanisms of action preparation and selection

In a changing world, one hallmark feature of human behaviour is the ability to use (learned) prior information for action selection. We ask how prior information and past experience influence activity in the motor system on a trial-by-trial basis. For example, we use electrophysiological TMS to "read-out" the functional state of M1  during action preparation based on uncertain information (Bestmann et al Curr Biol 2008; Mars et al Exp Brain Res 2007).

Related to this, we investigate how action selection is based on dynamic interactions (i.e., effective connectivity changes) between brain regions concerned with the learning and encoding of contextual uncertainty, and frontal regions for implementing these actions. This will ultimately help to understand how decision and preparation signals influence activity in the motor system.

More recently, we have started to explore the role of tonic dopamine for action reprogramming and the encoding of predictions about forthcoming events (Friston et al., 2011; Galea et al., 2011)

Relevant publications

Brown H, Friston K, Bestmann S (2011). Active inference, attention, and motor preparation. Front Psychol. 2011;2:218. Epub 2011 Sep 21.

Galea J, Bestmann S, Beigi M, Jahanshahi M, Rothwell JC. Action reprogramming in Parkinson's disease: response to prediction error is modulated by levels of dopamine. J Neurosci 32:542-50

Friston KJ, Shiner T, FitzGerald T, Galea JM, Adams R, Brown H, Dolan RJ, Moran R, Stephan KE, Bestmann S. Dopamine, affordance and active inference. PLoS Comput Biol. 2012 Jan;8(1):e1002327.

Ward NS, Bestmann S, Hartwigsen G, Weiss M, Christensen LO, Frackowiak RSJ, Siebner HR. Low-frequency transcranial magnetic stimulation of left dorsal premotor cortex improves the ability to adjust pre-planned actions. J Neurosci 30:9216-9223

Mars RB, Debener S, Gladwin TE, Harrison LM, Haggard P, Rothwell JC, Bestmann S (2008) Trial-by-trial fluctuations in the event-related encephalogram reflect dynamic changes in the degree of surprise. J Neurosci 28:12539-12545

Bestmann S, Harrison L, Blankenburg F, Mars R, Haggard P, Friston K, Rothwell JC (2008) Influences of contextual uncertainty and surprise on human corticospinal excitability during preparation for action. Current Biology 18:775-780

Klein-Flugge M, Nobbs D, Pitcher J, Bestmann S (in press). Variability of human cortico-spinal excitability tracks the state of action preparation. Journal of Neuroscience


Value-based decisions for actions

Decision making and action planning have long been studied as separate and independent processes. It was thought that the brain processes leading to a decision need to precede those involved in planning the resulting action. Recent evidence from non-human primates suggests that the brain processes underlying decision making and action planning and execution evolve in parallel, and share common neural resources. For example, decision-related neural signals can be observed in areas traditionally assigned to ‘motor processes’, and different models have been proposed to explain the role of decision variables in action planning.

In the human brain, however, little is known about the interplay between decision making and action planning. In particular, it is unclear (1) whether different mechanisms are involved in decisions that are related or unrelated to specific actions, and (2) how different decision variables, such as expected value, influence and enter the motor system when the decision is linked to a particular action. We study these questions by using a combination of non-invasive neuroimaging, electrophysiological recording, and stimulation techniques in healthy human adults.

Relevant publications

Klein-Flugge M, Bestmann S. Time-dependent changes in human cortico spinal excitability reveal value-based competition for action during decision processing. J Neurosci 32:8373-82


Galea J, Ruge D, Buijink A, Bestmann S, Rothwell JC (2013) Punishment induced behavioural and neurophysiological variability reveals dopamine-dependent selection of kinematic movement parameters. Journal of Neuroscience 33:3981-8


Concurrent TMS-fMRI and combined TMS-neuroimaging


Concurrent TMS-fMRI provides an experimental means to probe causal interactions in the human brain. The approach applies a direct input into the operation of a brain region, while simultaneously measuring evoked activity changes in remote but interconnected brain areas. The technique therefore provides a behaviour-independent assay of causal inter-regional interactions, by causing activity during the operation of an area with TMS. Together with our collaborators at the WTCN, we have helped to pioneer this technique, and currently only a handful of centers worldwide can conduct such experiments.

For example, we have recently used this technique to investigate task-state dependent causal interactions in the human motor system during hand movements. This work has shown that dorsal premotor cortex exerts task-state dependent causal influences on contralateral motor and premotor cortex (Bestmann et al, Cereb Cortex 2008), and how such interactions are altered following damage to the motor system after subcortical stroke (Bestmann et al, J Neurosci, 2010)

More recently, we have used Magnetic Resonance Spectroscopy (MRS) to ask how stimulation of cortex with TMS affects neurotransmitter concentration in human cortex (Stagg et al, J Neurophysiol 2009; Stagg et al, J Physiol 2011). This approach can provide a direct quantification of how modern neurostimulation approaches influence different neurotransmitter systems in health and disease.

Relevant publications

Bestmann S, Swayne O, Blankenburg F, Ruff CC, Teo J, Weiskopf N, Driver J, Rothwell JC, Ward NS. The role of contralesional dorsal premotor cortex after stroke. J Neurosci 30:11926-37

Bestmann S, Swayne O, Blankenburg F, Ruff CC, Haggard P, Weiskopf N, Josephs O, Driver J, Rothwell JC, Ward NS (2008) Dorsal premotor cortex exerts state-dependent causal influences on activity in contralateral motor and premotor cortex. Cereb Cortex 18:1281-1291

Bestmann S, Baudewig J, Siebner HR, Rothwell JC, Frahm J (2004) Functional MRI of the immediate impact of transcranial magnetic stimulation on cortical and subcortical motor circuits. Eur J Neurosci 19:1950-1962

Stagg CJ, Wylenska-Arridge M, Matthews PM, Johansen-Berg H, Jezzard P, Rothwell JC, Bestmann S (2009) The neurochemical effects of theta burst stimulation as assessed by magnetic resonance spectroscopy. J Neurophysiol. 101:2872-77.

Stagg CJ, Bestmann S, Constantinescu AO, Moreno Moreno L, Allman C, Mekle R, Woolrich M, Near J, Johansen-Berg H, Rothwell JC (2011) Relationship between physiological measures of excitability and levels of glutamate and GABA in the human motor cortex. J Physiol. 589:5845-55.


Reviews

Bestmann S, Feredoes E. Combined neurostimulation and neuroimaging in cognitive neuroscience: past, present and future" Annals of the New York Academy of Science (in press)

Bestmann S, Ruff CC, Blankenburg F, Weiskopf N, Driver J, Rothwell JC (2008) Mapping causal interregional influences with concurrent TMS - fMRI. Exp Brain Res 191:383-402.

Ruff CC, Driver J, Bestmann S (2009) Combining TMS and fMRI: from “virtual lesions” to functional network accounts of cognition. Cortex 45:1021-1024

Driver J, Blankenburg F, Bestmann S, Vanduffel W, Ruff CC. Concurrent brain-stimulation and neuroimaging for studies of cognition. Trends Cogn Sci. 13:319-327.

The UCL Institute of Neurology promotes teaching and research of the highest quality in neurology and the neurosciences. The Institute of Neurology and the National Hospital for Neurology and Neurosurgery are members of  UCL Partners, Europe's largest academic health science partnership.