Max-Philipp Stenner

Attentional Modulation of Alpha/Beta and Gamma Oscillations Reflect Functionally Distinct Processes

The brain adapts to dynamic environments by adjusting the attentional gain or precision afforded to salient and predictable sensory input. Previous research suggests that this involves the regulation of cortical excitability (reflected in prestimulus alpha oscillations) before stimulus onset that modulates subsequent stimulus processing (reflected in stimulus-bound gamma oscillations). We present two spatial attention experiments in humans, where we first replicate the classic finding of prestimulus attentional alpha modulation and poststimulus gamma modulation. In the second experiment, the task-relevant target was a stimulus change that occurred after stimulus onset. This enabled us to show that attentional alpha modulation reflects the predictability (precision) of an upcoming sensory target, rather than an attenuation of alpha activity induced by neuronal excitation related to stimulus onset. In particular, we show that the strength of attentional alpha modulations increases with the predictability of the anticipated sensory target, regardless of current afferent drive. By contrast, we show that the poststimulus attentional gamma enhancement is stimulus-bound and decreases when the subsequent target becomes more predictable. Hence, this pattern suggests that the strength of gamma oscillations is not merely a function of cortical excitability, but also depends on the relative mismatch of predictions and sensory evidence. Together, these findings support recent theoretical proposals for distinct roles of alpha/beta and gamma oscillations in hierarchical perceptual inference and predictive coding.

Dynamic Tuning of Tactile Localization to Body Posture

Localizing touch in space is essential for goal-directed action. Because body posture changes, the brain must transform tactile coordinates from an initial skin-based representation to external space by integrating information about current posture. This process, referred to as tactile remapping, generally results in accurate localization, but accuracy drops when skin-based and external spatial representations of touch are conflicting, e.g., after crossing the limbs. Importantly, frequent experience of such postures can improve localization. This suggests that remapping may not only integrate current sensory input but also prior experience. Here, we demonstrate that this can result in rapid changes in localization performance over the course of few trials. We obtained an implicit measure of tactile localization by studying the perceived temporal order of two touches, one on each hand. Crucially, we varied the number of consecutive trials during which participants held their arms crossed or uncrossed. As expected, accuracy dropped immediately after the arms had been crossed. Importantly, this was followed by a progressive recovery if posture was maintained, despite the absence of performance feedback. Strikingly, a significant improvement was already evident in the localization of the second pair of touches. This rapid improvement required preceding touch in the same posture and did not occur merely as a function of time. Moreover, even touches that were not task relevant led to improved localization of subsequent touch. Our findings show that touches are mapped from skin to external space as a function of recent tactile experience.

Subliminal action priming modulates the perceived intensity of sensory action consequences

Highlights • In theory, the motor system attenuates action-outcome perception to signal agency.• We use subliminal motor priming to test for the predicted motor locus of this effect.• The perceived intensity of an action-outcome is attenuated by compatible priming.• Compatible priming is known to enhance explicit agency judgements.• Sensory attenuation and agency inference depend on overlapping motoric signals.

Parallel processing streams for motor output and sensory prediction during action preparation

Sensory consequences of ones own actions are perceived as less intense than identical, externally generated stimuli. This is generally taken as evidence for sensory prediction of action consequences. Accordingly, recent theoretical models explain this attenuation by an anticipatory modulation of sensory processing prior to stimulus onset (Roussel et al. 2013) or even action execution (Brown et al. 2013). Experimentally, prestimulus changes that occur in anticipation of self-generated sensations are difficult to disentangle from more general effects of stimulus expectation, attention and task load (performing an action). Here, we show that an established manipulation of subjective agency over a stimulus leads to a predictive modulation in sensory cortex that is independent of these factors. We recorded magnetoencephalography while subjects performed a simple action with either hand and judged the loudness of a tone caused by the action. Effector selection was manipulated by subliminal motor priming. Compatible priming is known to enhance a subjective experience of agency over a consequent stimulus (Chambon and Haggard 2012). In line with this effect on subjective agency, we found stronger sensory attenuation when the action that caused the tone was compatibly primed. This perceptual effect was reflected in a transient phase-locked signal in auditory cortex before stimulus onset and motor execution. Interestingly, this sensory signal emerged at a time when the hemispheric lateralization of motor signals in M1 indicated ongoing effector selection. Our findings confirm theoretical predictions of a sensory modulation prior to self-generated sensations and support the idea that a sensory prediction is generated in parallel to motor output (Walsh and Haggard 2010), before an efference copy becomes available.

No unified reward prediction error in local field potentials from the human nucleus accumbens: evidence from epilepsy patients

Functional magnetic resonance imaging (fMRI), cyclic voltammetry, and single-unit electrophysiology studies suggest that signals measured in the nucleus accumbens (Nacc) during value-based decision making represent reward prediction errors (RPEs), the difference between actual and predicted rewards. Here, we studied the precise temporal and spectral pattern of reward-related signals in the human Nacc. We recorded local field potentials (LFPs) from the Nacc of six epilepsy patients during an economic decision-making task. On each trial, patients decided whether to accept or reject a gamble with equal probabilities of a monetary gain or loss. The behavior of four patients was consistent with choices being guided by value expectations. Expected value signals before outcome onset were observed in three of those patients, at varying latencies and with nonoverlapping spectral patterns. Signals after outcome onset were correlated with RPE regressors in all subjects. However, further analysis revealed that these signals were better explained as outcome valence rather than RPE signals, with gamble gains and losses differing in the power of beta oscillations and in evoked response amplitudes. Taken together, our results do not support the idea that postsynaptic potentials in the Nacc represent a RPE that unifies outcome magnitude and prior value expectation. We discuss the generalizability of our findings to healthy individuals and the relation of our results to measurements of RPE signals obtained from the Nacc with other methods.

Voluntary or involuntary? A neurophysiologic approach to functional movement disorders.

Patients with functional movement disorders (FMD) experience movements as involuntary that share fundamental characteristics with voluntary actions. This apparent paradox raises questions regarding the possible sources of a subjective experience of action. In addition, it poses a yet unresolved diagnostic challenge, namely how to describe or even quantify this experience in a scientifically and clinically useful way. Here, we describe recent experimental approaches that have shed light on the phenomenology of action in FMD. We first outline the sources and content of a subjective experience of action in healthy humans and discuss how this experience may be created in the brain. Turning to FMD, we describe implicit, behavioral measures that have revealed specific abnormalities in the awareness of action in FMD. Based on these abnormalities, we propose a potential, new solution to the paradox of volition in FMD.

Re-construction of action awareness depends on an internal model of action-outcome timing

Highlights • Action awareness can shift retrospectively at the time of an action-outcome.• In principle, this could reflect bottom-up interference and not subjective agency.• We keep bottom-up drive constant and manipulate temporal outcome variability instead.• Action awareness is shifted retrospectively in a context of variable outcome timing.• This top-down process may bias subjective agency when an outcome is unpredictable.

Intact automatic motor inhibition in attention deficit hyperactivity disorder

Hyperactivity and impulsivity are defining symptoms of attention-deficit hyperactivity disorder (ADHD), next to inattention. Hyperactive and impulsive behavior in ADHD is often thought to result from a deficit in inhibitory motor control. However, testing for such a deficit is complicated by coexisting deficits in ADHD, specifically an impairment in maintaining task set, e.g., due to inattention. Typical inhibition paradigms, such as Stop-signal, Go/NoGo or Flanker paradigms, are susceptible to a fundamental confound between inhibition and inattention because inhibition is an explicit goal in these tasks. We eliminate this confound by studying the negative compatibility effect (NCE), reflecting a core inhibitory function in the human motor system which, in healthy individuals, inhibits movements automatically, i.e., without deliberation or even conscious awareness. Our behavioral analysis, including Bayesian model comparison, as well as the time-course of the lateralized readiness potential (LRP), consistently show that this function is intact in children with ADHD compared to healthy controls, independent of the presence or absence of prominent hyperactive-impulsive symptoms. We conclude that hyperactivity and impulsivity in ADHD do not result from a low-level deficit in motor inhibition.

Erratum: Corrigendum: Changing pattern in the basal ganglia: motor switching under reduced dopaminergic drive

Scientific Reports 6: Article number: 2332710.1038/srep23327; published online: March 2016 2016; updated: August 19 2016.

Corrigendum to "Changing pattern in the basal ganglia: Motor switching under reduced dopaminergic drive". [Scientific Reports, 6:23327 (2016). doi:10.1038/srep23327]

Scientific Reports 6: Article number: 2332710.1038/srep23327; published online: March 2016 2016; updated: August 19 2016.