Stergios Makris

The truth-telling motor cortex: response competition in M1 discloses deceptive behaviour.

Neural circuits associated with response conflict are active during deception. Here we use transcranial magnetic stimulation to examine for the first time whether competing responses in primary motor cortex can be used to detect lies. Participants used their little finger or thumb to respond either truthfully or deceitfully regarding facial familiarity. Motor-evoked-potentials (MEPs) from muscles associated with both digits tracked the development of each motor plan. When preparing to deceive, the MEP of the non-responding digit (i.e. the plan corresponding to the truth) exceeds the MEP of the responding digit (i.e. the lie), whereas a mirror-reversed pattern occurs when telling the truth. This give away response conflict interacts with the time of stimulation during a speeded reaction period. Lies can even activate digit-specific cortical representations when only verbal responses are made. Our findings support neurobiological models which blend cognitive decision-making with motor programming, and suggest a novel index for discriminating between honest and intentionally false facial recognition.

Are object affordances fully automatic? A case of covert attention

Inspired in part by Gibsons (1979) ecological approach to perception, current neurocognitive theories of action suggest that the simple viewing of an object can automatically elicit motor programs for specific acts. However, the degree to which such affordances should be considered truly automatic is unknown. Here we explored the generation of motor plans afforded by pairs of cue objects that were viewed peripherally under different attentional states. Participants focused centrally while attending to just one of two peripheral cue objects that together had a strong significance for pinching, grasping, or both. They were instructed to ignore the objects and instead give power or precision grip responses to subsequent changes in background color. The data showed a significant interaction between type of response and type of object, indicating that object affordances are perceived even in nonfoveal vision. Critically, the generation of affordances was modulated by the locus of attention: Motor preparation was biased toward the attended object when two different categories of object appeared in the same trial, but the generation of affordances was also influenced by unattended stimuli. This finding demonstrates that object-action priming is not completely automatic, instead being constrained by processes of perceptual selection.

Dissociated Representations of Deceptive Intentions and Kinematic Adaptations in the Observer's Motor System

Previous studies showed that observing deceptive actions modulates the activity of the observers motor system. However, it is unclear whether this modulation reflects the coding of deceptive intentions or the mapping of the kinematic adaptations required to attain deceptive actions. Here, we used single-pulse transcranial magnetic stimulation to measure cortico-spinal excitability (CSE) from hand and forearm muscles while participants predicted the weight of cubes lifted by actors who received truthful information on the object weight and provided 1) truthful (truthful actions) or 2) deceptive (deceptive actions) cues to the observers or 3) who received fooling information and were asked to provide truthful cues (deceived actions). This way, we independently manipulated actors intentions and kinematic adaptations. We found that, as compared to truthful action observation, CSE increased during observation of deceptive actions, but decreased during observation of deceived actions. Importantly, while the CSE enhancement in response to deceptive intentions lacked muscle specificity, perceiving kinematic alterations in the deceived condition affected CSE only for the hand muscle involved in kinematic adaptations to unexpected object weight. This suggests that actors intentions and movement kinematics may be coded by the observers motor system at different hierarchical levels of action representation.

Do experts see it in slow motion? Altered timing of action simulation uncovers domain-specific perceptual processing in expert athletes

Accurate encoding of the spatio-temporal properties of others’ actions is essential for the successful implementation of daily activities and, even more, for successful sportive performance, given its role in movement coordination and action anticipation. Here we investigated whether athletes are provided with special perceptual processing of spatio-temporal properties of familiar sportive actions. Basketball and volleyball players and novices were presented with short video-clips of free basketball throws that were partially occluded ahead of realization and were asked to judge whether a subsequently presented pose was either taken from the same throw depicted in the occluded video (action identification task) or temporally congruent with the expected course of the action during the occlusion period (explicit timing task). Results showed that basketball players outperformed the other groups in detecting action compatibility when the pose depicted earlier or synchronous, but not later phases of the movement as compared to the natural course of the action during occlusion. No difference was obtained for explicit estimations of timing compatibility. This leads us to argue that the timing of simulated actions in the experts might be slower than that of perceived actions (“slow-motion” bias), allowing for more detailed representation of ongoing actions and refined prediction abilities.

Commentary: Viewing photos and reading nouns of natural graspable objects similarly modulate motor responses

Commentary: Viewing photos and reading nouns of natural graspable objects similarly modulate motor responses

P 148. Anticipatory motor simulation of deceptive actions in soccer players

The ability to form anticipatory representations of ongoing actions is crucial for meaningful and effective interactions in dynamic environments. Previous research has shown that simulating and predicting the outcome of ongoing actions is modulated by motor expertise. In sports, elite athletes exhibit great ability in predicting other players’ actions, mainly based on action body kinematics as well as visual body representations. Surprisingly, there has been little evidence so far on how motor experts such as athletes perceive and/or anticipate bluffing actions. A few studies applying temporal occlusion paradigms have shown that expert players are better in detecting deceptive actions compared to expert observers. A recent study by Tomeo et al. (2012) in soccer players has found that the ability to detect deceptive actions relies on a complex mechanism of inhibitory and excitatory processes within the motor system. Furthermore, it was indicated that the balance between these processes depends on both visual and motor expertise. The present study has tried to identify the involvement and interactions between visual and motor areas concerning the detection of bluffing actions in soccer penalty kicks. We used the experimental paradigm described by Tomeo et al. (2012) , during which subjects (expert kickers, goalkeepers and novices) were judging the direction of the ball after a penalty kick, and we applied a repetitive TMS methodology in order to cause online disruption of two different regions; the dorsal premotor cortex (PMd) and the superior temporal sulcus (STS). Results have shown a strong modulation in the task performance between the sample groups caused by disruption of the STS area compared to control areas. Hence, new evidence is provided on how visual and motor expertise contributes to representing actions and detecting bluffing actions.

Continuous Theta Burst Transcranial Magnetic Stimulation of the Right Dorsolateral Prefrontal Cortex Impairs Inhibitory Control and Increases Alcohol Consumption

Previous research indicates that alcohol intoxication impairs inhibitory control and that the right dorsolateral prefrontal cortex (rDLPFC) is a functional brain region important for exercising control over thoughts and behaviour. At the same time, the extent to which changes in inhibitory control following initial intoxication mediate subsequent drinking behaviours has not been elucidated fully. Ascertaining the extent to which inhibitory control impairments drive alcohol consumption, we applied continuous theta burst transcranial magnetic stimulation (rDLPFC cTBS vs. control) to isolate how inhibitory control impairments (measured using the Stop-Signal task) shape ad libitum alcohol consumption in a pseudo taste test. Twenty participants (13 males) took part in a within-participants design; their age ranged between 18 and 27 years (M = 20.95, SD = 2.74). Results indicate that following rDLPFC cTBS participants’ inhibitory control was impaired, and ad libitum consumption increased. The relationship between stimulation and consumption did not appear to be mediated by inhibitory control in the present study. Overall, findings suggest that applying TMS to the rDLPFC may inhibit neural activity and increase alcohol consumption. Future research with greater power is recommended to determine the extent to which inhibitory control is the primary mechanism by which the rDLPFC exerts influence over alcohol consumption, and the degree to which other cognitive processes may play a role.

Cathodal tDCS evidence on how perceived body weight similarity and weight stigma can modulate the understanding of observed familiar actions.

Previous experimental evidence has shown that motor resonance (i.e. the mapping of others’ actions onto one’s own motor repertoire) can be influenced by individual differences in personality traits. However, no evidence has been reported so far of the effects of physical appearance and negative attitudes toward obesity to the mechanism of MR. In the present study, normal-weight and overweight participants performed an implicit task, in which they were observing amateur actors reaching and grasping a light or heavy cube with or without deception (true vs. fake actions). Physical similarity between observers and actors was manipulated by presenting videos of slim or overweight actors. Before the task, all participants received cathodal or sham transcranial direct current stimulation (tDCS) over the left motor cortex, previously shown to decrease excitability of the aforementioned cortical area. At the end of each video-clip participants were instructed to indicate the correct cube size (light or heavy). Fat phobic attitudes and automatic preference for thin than fat people were also examined. Signal detection analysis (d’) on the currently acquired accuracy data (N=15) has indicated a significant 3-way interaction between type of stimulation (cathodal, sham), type of action (true, fake) and model weight. Overall, both normal and overweight participants were able to better simulate the actions performed by the slim as compared to overweight actors. However, this effect was diminished after cathodal stimulation of the left hemisphere motor area. Hence, we provide experimental evidence of action simulation and understanding being modulated by an implicit preference towards slim bodies.

Off-line rTMS of left Dorsolateral Prefrontal Cortex reduces food cravings in females but not males

Dysfunction of the left dorsolateral prefrontal cortex (DLFPC) has been crucially implicated in craving for food. Here, we aimed at expanding this result by investigating gender differences in food cravings in female (n=8; age=20.38yrs; BMI=22.54) and male (n=9; age=20.67yrs; BMI=20.89) healthy participants. Off-line repetitive transcranial magnetic stimulation (rTMS; 15 mins, 900 pulses) was administered on the left DLPFC and on the vertex (as control condition) before and after exposure to sweet food. Desire for salty and sweet food consumption was assessed by visual analogue scales (VAS) and calories consumed before and after rTMS. While after vertex-rTMS women expressed higher desire for sweet but not for salty foods with respect to men, desire for food did not change and remained stable before and after DLPFC-rTMS. No differences were observed in the consumed calories after the two rTMS stimulation. Our results provide preliminary evidence of a brain mechanism by which cognitive inhibition decreases the desire for sweet foods and implicates lower ability to suppress cravings in women as a contributing factor to gender differences possibly in binge eating disorder and obesity.