Aviad A. Hadar

Smoking Cessation Induced by Deep Repetitive Transcranial Magnetic Stimulation of the Prefrontal and Insular Cortices: A Prospective, Randomized Controlled Trial

BACKGROUNDnTobacco smoking is the leading cause of preventable death in developed countries. Our previous studies in animal models and humans suggest that repeated activation of cue-induced craving networks followed by electromagnetic stimulation of the dorsal prefrontal cortex (PFC) can cause lasting reductions in drug craving and consumption. We hypothesized that disruption of these circuitries by deep transcranial magnetic stimulation (TMS) of the PFC and insula bilaterally can induce smoking cessation.nnnMETHODSnAdults (N = 115) who smoke at least 20 cigarettes/day and failed previous treatments were recruited from the general population. Participants were randomized to receive 13 daily sessions of high-frequency, low-frequency or sham stimulation following, or without, presentation of smoking cues. Deep TMS was administered using an H-coil version targeting the lateral PFC and insula bilaterally. Cigarette consumption was evaluated during the treatment by measuring cotinine levels in urine samples and recording participants self-reports as a primary outcome variable. Dependence and craving were assessed using standardized questionnaires.nnnRESULTSnHigh (but not low) frequency deep TMS treatment significantly reduced cigarette consumption and nicotine dependence. The combination of this treatment with exposure to smoking cues enhanced reduction in cigarette consumption leading to an abstinence rate of 44% at the end of the treatment and an estimated 33% 6 months following the treatment.nnnCONCLUSIONSnThis study further implicates the lateral PFC and insula in nicotine addiction and suggests the use of deep high-frequency TMS of these regions following presentation of smoking cues as a promising treatment strategy.

Viewing objects and planning actions: On the potentiation of grasping behaviours by visual objects

How do humans interact with tools? Gibson (1979) suggested that humans perceive directly what tools afford in terms of meaningful actions. This affordances hypothesis implies that visual objects can potentiate motor responses even in the absence of an intention to act. Here we explore the temporal evolution of motor plans afforded by common objects. We presented objects that have a strong significance for action (pinching and grasping) and objects with no such significance. Two experimental tasks involved participants viewing objects presented on a computer screen. For the first task, they were instructed to respond rapidly to changes in background colour by using an apparatus mimicking precision and power grip responses. For the second task, they received stimulation of their primary motor cortex using transcranial magnetic stimulation (TMS) while passively viewing the objects. Muscular responses (motor evoked potentials: MEPs) were recorded from two intrinsic hand muscles (associated with either a precision or power grip). The data showed an interaction between type of response (or muscle) and type of object, with both reaction time and MEP measures implying the generation of a congruent motor plan in the period immediately after object presentation. The results provide further support for the notion that the physical properties of objects automatically activate specific motor codes, but also demonstrate that this influence is rapid and relatively short lived.

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.

Binocular vision enhances a rapidly evolving affordance priming effect: Behavioural and TMS evidence

Extensive research has suggested that simply viewing an object can automatically prime compatible actions for object manipulation, known as affordances. Here we explored the generation of covert motor plans afforded by real objects with precision (pinchable) or whole-hand/power (graspable) grip significance under different types of vision. In Experiment 1, participants viewed real object primes either monocularly or binocularly and responded to orthogonal auditory stimuli by making precision or power grips. Pinchable primes facilitated congruent precision grip responses relative to incongruent power grips, and vice versa for graspable primes, but only in the binocular vision condition. To examine the temporal evolution of the binocular affordance effect, participants in Experiment 2 always viewed the objects binocularly but made no responses, instead receiving a transcranial magnetic stimulation pulse over their primary motor cortex at three different times (150, 300, 450ms) after prime onset. Motor evoked potentials (MEPs) recorded from a pinching muscle were selectively increased when subjects were primed with a pinchable object, whereas MEPs from a muscle associated with power grips were increased when viewing graspable stimuli. This interaction was obtained both 300 and 450ms (but not 150ms) after the visual onset of the prime, characterising for the first time the rapid development of binocular grip-specific affordances predicted by functional accounts of the affordance effect.

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.

Right Prefrontal Deep Tms Effects On Attention Symptoms: Behavioral Outcomes and Electrophysiological Correlates

Introduction Despite its high prevalence, the validated treatment for ADHD is chronic administration of psychostimulants, which is associated with side effects and occasionally not tolerated. Deep TMS using special coil designs for targeting neural networks linked with neuropsychiatric disorders, may become a viable alternative. Objectives Comparison of rTMS treatment using deep, figure-8 and sham coils on ADHD symptoms. Methods In the current randomized, sham-controlled study, adult ADHD patients received 15 daily sessions of high-frequency rTMS directed to the right prefrontal cortex (rPFC), using either deep, figure-8, or a sham coil. ADHD symptoms and cognitive alterations were assessed using the CAARS-INV, self–report questionnaires and performance tests. Additionally, the stop signal task (SST) combined with EEG measures was used to asses behavioural inhibition and ERPs. EEG responses to an inhibitory protocol of paired TMS pulses over the rPFC were measured before and after treatments. A healthy control group was evaluated at baseline for comparison. Results Several ADHD symptoms were improved in patients that received dTMS but not standard figure-8 or sham treatment (p=0.007, CAARS; p=0.014, SST). Differences between ADHD patients and healthy controls were demonstrated in ERPs during the SST, and in response to single and paired TMS pulses. The lower amplitudes of ERPs in patients correlated with ADHD symptoms and behavioural inhibition measures. Conclusions Repeated stimulation of deep areas in the rPFC has therapeutic potential, where rPFC excitability is impaired in ADHD patients. Ongoing analysis attempts to establish the neurophysiological measures as predictors and biomarkers for effectiveness of dTMS treatment.

Answering the missed call: Initial exploration of cognitive and electrophysiological changes associated with smartphone use and abuse

Background Smartphone usage is now integral to human behavior. Recent studies associate extensive usage with a range of debilitating effects. We sought to determine whether excessive usage is accompanied by measurable neural, cognitive and behavioral changes. Method Subjects lacking previous experience with smartphones (n = 35) were compared to a matched group of heavy smartphone users (n = 16) on numerous behavioral and electrophysiological measures recorded using electroencephalogram (EEG) combined with transcranial magnetic stimulation (TMS) over the right prefrontal cortex (rPFC). In a second longitudinal intervention, a randomly selected sample of the original non-users received smartphones for 3 months while the others served as controls. All measurements were repeated following this intervention. Results Heavy users showed increased impulsivity, hyperactivity and negative social concern. We also found reduced early TMS evoked potentials in the rPFC of this group, which correlated with severity of self-reported inattention problems. Heavy users also obtained lower accuracy rates than nonusers in a numerical processing. Critically, the second part of the experiment revealed that both the numerical processing and social cognition domains are causally linked to smartphone usage. Conclusion Heavy usage was found to be associated with impaired attention, reduced numerical processing capacity, changes in social cognition, and reduced right prefrontal cortex (rPFC) excitability. Memory impairments were not detected. Novel usage over short period induced a significant reduction in numerical processing capacity and changes in social cognition.

Motor-evoked potentials reveal a motor-cortical readout of evidence accumulation for sensorimotor decisions.

Many everyday activities, such as driving and sports, require us to engage in time-pressured sensorimotor decision making in response to visual cues. The computational principle of continuous evidence accumulation is the dominant account underlying models of speeded decision making, but the nature and locus of the decision variable that triggers action is debated. Traditionally, cognitive stages such as perception, stimulus-response translation, and the generation of motor plans, have been considered to occur in series. However, this idea is challenged by neurophysiological work in animals, suggesting that cognitive operations are distributed across sensorimotor cortex. Here, we investigate whether a decision variable can be observed in the primary motor cortex (M1) of humans. Participants categorised faces as male or female, with task difficulty manipulated using natural or morphed stimuli. Transcranial magnetic stimulation, applied at random across the reaction-time interval, produced motor-evoked potentials (MEPs) in two hand muscles that were the major contributors when generating the correct and incorrect pinch/grip movements. MEP magnitudes reveal covert action preparation, even when no action is produced. Smoothing MEPs using a Gaussian kernel allowed us to recover a continuous time-varying MEP average, comparable to an EEG component, which permitted precise localisation of the time at which the motor plan for the responding muscle began to dominate over the non-responding action. This moment was calculated in both stimulus-locked and response-locked analyses, and was found to occur at the same time with stimulus locking, but earlier with response locking, when ambiguous stimuli made the decision more challenging. This pattern is consistent with M1 providing a continuous readout of evidence accumulation. We predicted the evidence accumulation profile from a drift diffusion model, using only behavioural data, and found a good qualitative match to the observed neurometric MEP profiles. Meeting abstract presented at VSS 2015.