Search

Neuropsychologia : an international journal in behavioural and cognitive neuroscience 159, 107921 (2021). doi:10.1016/j.neuropsychologia.2021.107921, Published by Elsevier Science, Amsterdam [u.a.]

Background. Frontostriatal networks are neural pathways formed between frontal lobe regions and striatum that is involved in cognitive and behavioural processes. Transcranial Magnetic Stimulation (TMS) is able to modulate connectivity in the human brain and it is widely used for clinical purposes to treat depression patients. This exploratory PET and TMS multimodal study would contribute to better understand the role of striatal dopaminergic neurotransmission in the fronto-striatal area. Objective. The main objective of the study is to investigate the fronto-striatal connectivity by measuring the release of dopamine in the striatum in response to an excitatory intermittent theta burst stimulation (iTBS) of the left-dlPFC. A PET measurement was performed by using the 18F-DesmethoxyFallypride (DMFP) radioligand, that is a high affinity receptor-antagonist which competes with endogenous Dopamine neurotransmitters for D2/D3 receptor binding. Methods. The study was conducted on 23 healthy participants, who underwent iTBS sham (control) and verum stimulations on separate days. The PET scan lasted 120 mins, consisting of 4 iTBS stimulations delivered to the left-DLPFC at 30 mins interval. In verum stimulation, 90% of resting motor threshold (rMT) was used as the stimulation intensity. The excitatory iTBS protocol is delivered in a sequence of trains (burst of 10 pulses in 2 secs having inter train interval of 8 secs), with a total duration of 190 secs. PET dynamic data was analysed using reference region method in which cerebellum was used as the reference region (due to lack of D2-D3 receptors). Binding Potentials (BP) are the main outcome measure representing the ligand binding which is inversely proportional to the Dopamine (DA) levels.Mean Binding Potentials in the sub-regions of the striatum (Nucleus Caudate and Putamen) were compared between the sham and verum stimulation using analysis of variance (ANOVA). Results. iTBS stimulation of the left DLPFC increased the dopamine release (as reflected by BPs) in the striatum areas (putamen and nucleus caudate) in the verum stimulation, as compared to sham stimulation.Although the increase in dopamine release did not differ between the first block of stimulation, we observed significant increase after two, three and fourth blocks of stimulation. Conclusion. Our data suggest that the efficiency of iTBS protocol can effectively enhance fronto-striatal connectivity by applying a higher number of stimuli (i.e., 3rd & 4th TMS block but not 1st-& 2nd block). This minimal time stimulation protocol can be used as a therapy for treating Depression patients by presenting it in the repeated blocks of short intervals. This scheme could prevent the long stimulation protocols, and be less painful. Fig. 1. Figure represents the statistically significant main effect of TMS. The verum stimulation shows a reduction of 8.6% [18F]DMFP Binding Potential as compared to the sham stimulation. Fig. 2. Percentage reduction in [18F] desmethoxyfallypride-binding potentials extracted from the difference of sham and verum stimulation in healthy subjects. Dose-dependent iTBS aftereffects seem to be more pronounced at 3rd block and 4th block respectively as compared to 1st and 2nd block of TMS.

The handle-to-hand correspondence effect consists of faster and more accurate responses when the responding hand is aligned with the handle side of an object tool, compared to when they lay on opposite sides. This effect has been attributed to the activation of affordances. Recent studies, however, claimed that it may depend on the spatial coding of the object on the basis of its visual asymmetry (location-coding account). Affordances are namely direct and meaningful relations between recognized objects and the observers’ action system. Therefore, any manipulation that disrupts the body structure of object tools could potentially affect their identification and prevent the activation of affordances. The present study investigated the nature of the handle-to-hand correspondence effects by manipulating structural asymmetry and visual salience of object tools, while preserving their integrity that is, leaving unaltered the original possibilities to activate grasping affordances. Three experiments were run. Results were consistent with the location-coding account and claim for accurate control of visual asymmetries in object stimuli during investigation of affordance effects.

Responses to object stimuli are often faster when jutting handles are aligned with responding hands, than when they are not: handle-to-hand correspondence effects. According to a location coding account, locations of visually salient jutting parts determine the spatial coding of objects. This asymmetry then facilitates same-sided responses compared to responses on the opposite side. Alternatively, this effect has been attributed to grasping actions of the left or the right hand afforded by the handle orientation and independent of its salience (affordance activation account). Our experiments were designed to disentangle the effects of pure salience from those of affordance activations. We selected pictures of tools with one salient and non-graspable side, and one graspable and non-salient side (non-jutting handle). Two experiments were run. Each experiment had two groups of participants: one group discriminated the location of the salient side of the object stimuli; the other group discriminated the location of the graspable side of them. In Experiment 1, responses were left and right button presses; in Experiment 2, they were left and right button presses plus reach-and-grasp actions. When visual salience was removed from graspable sides, no correspondence effect was observed between their orientation and the responding hands in both the experiments. Conversely, when salience depended on non-graspable portions, a correspondence effect was produced between their orientation and the responding hand. Overt attention to graspable sides did not potentiate any grasping affordance even when participants executed grasping responses in addition to button presses. Results support the location coding account: performance was influenced by the spatial coding of visually salient properties of objects.

Background Transcranial direct current stimulation (tDCS) is a non-invasive technique that modulates excitability of neurons in the motor cortex. In particular, anodal tDCS leads to cortical facilitation and overall increase in excitability ( Nitsche et al., 2000 ). Objective Although the effects of anodal tDCS on modulating motor cortex activation have been reported, there is little evidence of long term reduction of GABA concentration following anodal stimulation. Therefore, to characterize the duration of after effects of primary motor cortex (M1) excitability following anodal stimulation, we performed repeated magnetic resonance spectroscopy (MRS) measurements of GABA for 60 min after the stimulation. Materials and methods Thirty-two right-handed healthy volunteers were recruited in RWTH Aachen University. GABA-edited spectra were acquired using 3 T Siemens scanner from a volume of interest of 3 × 3 × 3 cm (27 mL) carefully placed on the hand motor area of the left primary motor cortex [ Fig. 1 ]. MEGA-PRESS J-editing ( Mescher et al., 1998 ), was used for GABA detection. Data processing and quantification of spectra was performed with TARQUIN ( Wilson et al., 2011 ). Results An ANOVA was performed on percentage of GABA concentrations with stimulation (sham vs. anodal) and measurement (12 measurements: 2 pre-stimulation and 10 post-stimulation measurements taken every 6 min) as between- and within-participants factors. The main effects of stimulation was not significant F(1, 30) = 1.157, p = .291. However, main effect of measurement was significant F(11, 330) = 2.378 p = .008. Remarkably, the interaction of stimulation x measurement was significant F(11, 330) = 2.249, p = .0128 [ Fig. 2 ]. GABA concentration decreased significantly in the anodal stimulation group at first (20th minute) post-stimulation measurement, and then stayed the same at measurements eighth, ninth and tenth ts (3) Discussion and conclusion Our results revealed a significant early drop of GABA concentration within 20 min following anodal stimulation and late drop of GABA after 66th minutes until the last post stimulation measurement (86th min). Early and late decrease in GABA could be due to a decrease of activity of glutamic acid decarboxylase (GAD) 67 and long term depression like plasticity, respectively. This technique may open a new field of application for long-lasting neuroplastic induction, especially in the rehabilitation of stroke patients.

Two experiments are reported in which we manipulated relevant and irrelevant stimulus dimensions to assess whether an increase in temporal overlap would influence the time course of a “standard” Simon effect (obtained when visual stimuli are presented on the left/right of the screen and left/right responses are performed with uncrossed hands). This procedure is new in two ways: First, the manipulations were intended to reduce, instead of increase, the distance between conditional and unconditional response-activation processes. Second, we manipulated the relevant and irrelevant stimulus dimensions in a manner that did not vary stimulus onset asynchronies, precues, or go/no go trials, or alter the stimulus quality. Results were consistent with the hypothesis that when the two response processes are shifted closer to each other, the Simon effect would be sustained across time, instead of decreasing as typically found. These findings are discussed in line with the temporal overlap hypothesis and with an automatic activation account.

The handle-to-hand correspondence effect refers to faster and more accurate responses when the responding hand is aligned with the graspable part of an object tool, compared to when they lay on opposite sides. We performed four behavioral experiments to investigate whether this effect depends on the activation of grasping affordances (affordance activation account) or is to be traced back to a Simon effect, resulting from the spatial coding of stimuli and responses and from their dimensional overlap (location coding account). We manipulated the availability of a response alternative by requiring participants to perform either a unimanual go/no-go task (absence of a response alternative) or a joint go/no-go task (available response alternative) and the type of response required (button-press or grasping response). We found no handle-to-hand correspondence effect in the individual go/no-go task either when a button-press (Experiment 1A) or a grasping (Experiment 2A) response was required, whereas a significant effect emerged in the joint go/no-go task, irrespective of response modality (Experiments1B and 2B). These results do not support the idea that complex motor affordances are activated for meaningful objects, but are rather consistent with the more parsimonious location coding account.

Frontiers in human neuroscience 11, 148 (2017). doi:10.3389/fnhum.2017.00148, Published by Frontiers Research Foundation, Lausanne

An increasing number of studies have shown a close link between perception and action, which is supposed to be responsible for the automatic activation of actions compatible with objects' properties, such as the orientation of their graspable parts. It has been observed that left and right hand responses to objects (e.g., cups) are faster and more accurate if the handle orientation corresponds to the response location than when it does not. Two alternative explanations have been proposed for this handle-to-hand correspondence effect: location coding and affordance activation. The aim of the present study was to provide disambiguating evidence on the origin of this effect by employing object sets for which the visually salient portion was separated from, and opposite to the graspable 1, and vice versa. Seven experiments were conducted employing both single objects and object pairs as visual stimuli to enhance the contextual information about objects' graspability and usability. Notwithstanding these manipulations intended to favor affordance activation, results fully supported the location-coding account displaying significant Simon-like effects that involved the orientation of the visually salient portion of the object stimulus and the location of the response. Crucially, we provided evidence of Simon-like effects based on higher-level cognitive, iconic representations of action directions rather than based on lower-level spatial coding of the pure position of protruding portions of the visual stimuli. (PsycINFO Database Record

Choice reaction tasks are performed faster when stimulus location corresponds to response location (Simon effect). This spatial stimulus-response compatibility effect affects performance at the level of action planning and execution. However, when response selection is completed before movement initiation, the Simon effect arises only at the planning level. The aim of this study was to ascertain whether when a precocious response selection is requested, the Simon effect can be detected on the kinematics characterizing the online control phase of a non-ballistic movement. Participants were presented with red or green colored squares, which could appear on the right, left, above, or below a central cross. Depending on the square's color, participants had to release one of two buttons (right/left), then reach toward and press a corresponding lateral pad. We found evidence of the Simon effect on both action planning and on-line control. Moreover, the investigation of response conflict at the level of previous trials (i.e., n-1), a factor that might determine interference at the level of the current response, revealed a conflict adaptation process across trials. Results are discussed in terms of current theories concerned with the Simon effect and the distinction between action planning and control.

Scientific reports 6, 21706 (2016). doi:10.1038/srep21706, Published by Nature Publishing Group, London

Background Transcranial direct current stimulation (tDCS) is a non-invasive technique that modulates excitability of neurons in the cerebral cortex. Anodal tDCS has been reported to modulate the activation of motor cortex as well as GABA concentration in motor cortex ( Nitsche and Paulus, 2000 ). Objective To date very little is known about the nature and duration of tDCS induced effects. We aimed to investigate long-term effects of anodal tDCS on the primary motor cortex (M1). Repeated magnetic resonance spectroscopy (MRS) was employed to measure relative gamma-aminobutyric acid concentrations in M1 up to 60 min after stimulation. Materials and methods Twenty right-handed healthy volunteers were recruited in RWTH Aachen University. 1 mA anodal and sham tDCS were applied for 10 min, respectively. MRS scans were performed before and after stimulation on a 3T Siemens PRISMA whole-body scanner, GABA-edited spectra were acquired from a volume of interest of 3 × 3 × 3 cm (27 mL) carefully placed on the hand area of the left M1 ( Fig. 1 ). MEGA-PRESS J-editing ( Mescher et al., 1998 ) was used for GABA detection. Data processing and quantification of spectra was performed with TARQUIN ( Wilson et al., 2011 ). Results An ANOVA was performed on GABA concentrations with stimulation (sham vs. anodal) and measurement (12 measurements: 2 pre-stimulation and 10 post-stimulation measurements) as between- and within-participants factors, respectively. The main effects of stimulation and measurements were significant F (1, 18) = 9.200, p = .007 and F (11, 198) = 2.354, p = .010. Crucially, the interaction was significant F (11, 198) = 3.089, p Fig. 2 ). In other words, GABA signal showed no change over time in the sham group, whereas it decreased significantly in the anodal group and stayed at about the same level across the whole planned test measurements over 86 min. Discussion and conclusion Such a long-lasting (over 86 min) decrease in GABA concentration corresponds not only to the reported behavioral effects of tDCS stimulation, such as increased motor learning capacity, but also, to the timeline of increased brain energy consumption following anodal tDCS as measured with Phosphorus spectroscopy ( Binkofski et al., 2011 ). Our results are relevant for the understanding of the mechanism of motor cortical plasticity and neuropsychiatric diseases in humans.

The aim of the present study was to investigate the relationship between the affordance effect (i.e., the advantage for responses corresponding spatially with the location of an object’s graspable part) and the Simon effect (i.e., the advantage for responses corresponding spatially with stimulus location) and to assess whether they both occur at the response selection stage. In two experiments participants were required to respond according to the vertical orientation (upward or inverted) of photographs of graspable objects, located to the left or right of fixation, with their handles oriented to the right or left. In Experiment 1 the response was a buttonpress; in Experiment 2 was a reaching movement. Our results showed that both Simon and affordance effects emerged in response times but not in movement times. In Experiment 1, the two effects did not interact, whereas a clear interaction emerged in Experiment 2. These results seem to suggest that the interaction between Simon and affordance effects may depend on the type of required action.

The Simon effect consists of a faster and a more accurate performance when spatial responses correspond to irrelevant-spatial stimuli than when they do not. The time course of the Simon effect was investigated using centrally presented conventional signals (arrows and spatial words) conveying spatial information through iconic-symbolic (Experiments 1 and 2) and semantic (Experiment 3) codes. Time-demanding object-inherent and semantic spatial codes were generated for arrows and words, respectively. This resulted in Simon effects increasing in size across increasing response times (RTs). However, different onsets of the Simon effect were displayed across RT distributions. For arrows, the Simon effect was already significant at the fastest RT intervals, providing clear evidence that they are distinctively more effective directional indicators compared to words. © 2009 Hogrefe and Huber Publishers

In the present study we considered the two factors that have been advocated for playing a role in emotional attention: perception of gaze direction and facial expression of emotions. Participants performed an oculomotor task in which they had to make a saccade towards one of the two lateral targets, depending on the colour of the fixation dot which appeared at the centre of the computer screen. At different time intervals (stimulus onset asynchronies, SOAs: 50,100,150 ms) following the onset of the dot, a picture of a human face (gazing either to the right or to the left) was presented at the centre of the screen. The gaze direction of the face could be congruent or incongruent with respect to the location of the target, and the expression could be neutral or angry. In Experiment 1 the facial expressions were presented randomly in a single block, whereas in Experiment 2 they were shown in separate blocks. Latencies for correct saccades and percentage of errors (saccade direction errors) were considered in the analyses. Results showed that incongruent trials determined a significantly higher percentage of saccade direction errors with respect to congruent trials, thus confirming that gaze direction, even when task-irrelevant, interferes with the accuracy of the observer's oculomotor behaviour. The angry expression was found to hold attention for a longer time with respect to the neutral one, producing delayed saccade latencies. This was particularly evident at 100 ms SOA and for incongruent trials. Emotional faces may then exert a modulatory effect on overt attention mechanisms. © 2007 Marta Olivetti Belardinelli and Springer-Verlag.

Gaze direction and facial expressions are critical components of face processing and have been shown to influence attention deployment. We investigated whether gaze direction (direct vs. averted) combined with a neutral or angry expression modulates the deployment of attentional resources over time. In a rapid serial visual presentation (RSVP) paradigm participants had to decide the gender of a neutral or an angry target face with direct or averted gaze (T1) and then to judge the orientation of a target picture of a landscape (T2), following the face at different time intervals. Results showed no attentional blink effect (i.e., no deterioration in T2 accuracy) when T1 was an angry face with direct gaze, whereas it was present for angry faces with averted gaze or neutral faces with either averted or direct gaze. These findings are consistent with appraisal theories and are discussed against the background of automatic processing of threat stimuli.

The role of affordances In our opinion the model would be improved if affordance for action mechanisms were integrated: The potentiation of motor interactions consistent with the conventional use of a perceived tool (Bub et al., 2008). Affordances would easily explain the mechanism underlying the quick choice of the most appropriate tool when an action goal is given. In Figure 1A, bidirectional connections between available tools and usage contexts represent the automatic activation of stable affordances (Borghi and Riggio, 2009) emerging from invariant features of the tool (mainly its functional meaning) incorporated into the object representation in long term memory (e.g., a spoon typically stirs and scoops, a knife cuts and spreads). Activation of stable affordances is independent of context or task to be carried out. Furthermore, for each stable affordance, variable affordances emerging from temporary characteristics of the tools such as their current handle orientation are also activated. When an action goal is given (stir the coffee), attention is restricted to a specific action context (to stir) and oriented to available and action-consistent tools (spoon and stirrer). Thus, activation of a restricted number of stable and variable affordances is privileged (e.g., “spoon + to stir” and “stirrer + to stir” with the right hand) over those not consistent with the action goal. Here, the controller will select “spoon + to stir” instead of “stirrer + to stir” and execute the required action with the hand corresponding to the handle orientation. Selection between two equally appropriate tools is assumed to be determined by stronger stable and variable affordances being activated. A commentary on

We compared the performance of skilled drummers with that of nondrummers and nonmusicians in the Simon and spatial stimulus—response compatibility (SRC) tasks to investigate whether and to what extent spatial performance can be modified by motor behaviors acquired in real life. Drummers were chosen because, compared with other musicians and the general population, their efficient performance depends mainly on the processing of spatial information. Although the Simon effect was equivalent for the three groups, the spatial SRC effect was less pronounced in drummers. The advantage was present even when feet were used as responding effectors, suggesting a central locus of the effect. These results suggest that spatial stimulus—response translations are influenced by real-life motor training, with drummers’ training speeding up the intentional stimulus—response translations when stimulus and response locations are on opposite sides.

In the present study two separate stimulus–response compatibility effects (functional affordance and Simon-like effects) were investigated with centrally presented pictures of an object tool (a torch) characterized by a structural separation between the graspable portion and the goal-directed portion. In Experiment 1, participants were required to decide whether the torch was red or blue, while in Experiment 2 they were required to decide whether the torch was upright or inverted. Our results showed that with the same stimulus two types of compatibility effect emerged: one based on the direction signalled by the goal-directed portion of the tool (a Simon-like effect as observed in Experiment 1), and the other based on the actions associated with an object (a functional affordance effect as observed in Experiment 2). Both effects emerged independently of the person's intention to act on the stimulus, but depended on the stimulus properties that were processed in order to perform the task.

The Simon effect refers to faster responding when an irrelevant stimulus location corresponds with the response to a relevant stimulus attribute than when it does not. We investigated whether a memory-based Simon-like effect would occur when the irrelevant spatial attribute was associated with the stimulus during a prior task. In a first task, an association between colour and location was formed by requiring participants to count the occurrences of two colour stimuli, each of which was always presented in a left or right location. In a second task, the colour stimuli were presented centrally and mapped to left and right keypresses, with the mapping being inconsistent or consistent with the prior colour-location associations. A Simon-like effect was evident at the start of the second task, with performance being better when the established colour–position associations were consistent with the colour–response mapping than when they were not. This result indicates that stimulus–stimulus short-term memory as...

Frontiers in psychology 4, 362 (2013). doi:10.3389/fpsyg.2013.00362, Published by Frontiers Research Foundation, Lausanne