Leonor J. Romero Lauro

What is the role of the uncinate fasciculus? Surgical removal and proper name retrieval

The functional role of the uncinate fasciculus is still a matter of debate. We examined 44 patients submitted to awake surgery for removal of a left frontal or temporal glioma. In 18 patients, the removal included the uncinate fasciculus. We compared patients with or without removal on a series of neuropsychological tasks, performed at different time intervals: pre-surgery, in the first week after surgery and 3 months after surgery. Functional magnetic resonance and diffusion tensor imaging, fibre-tracking techniques were performed before surgery. At the last examination, patients with uncinate removal were significantly impaired in naming of famous faces and objects as compared with patients without removal. We further divided patients according to the site of the tumour (either frontal or temporal). At the follow-up, patients with a temporal glioma who underwent uncinate removal had the worst loss of performance in famous face naming. In addition, on the same task, the group with a frontal glioma that underwent resection of the frontal part of the uncinate performed significantly worse than the group with a frontal glioma but without uncinate removal. In conclusion, the resection of the uncinate fasciculus, in its frontal or temporal part, has long-lasting consequences for famous face naming. We suggest that this fibre tract is part of a circuitry involved in the retrieval of word form for proper names. Retrieval of conceptual knowledge was intact.

EEG Responses to TMS Are Sensitive to Changes in the Perturbation Parameters and Repeatable over Time

Background High-density electroencephalography (hd-EEG) combined with transcranial magnetic stimulation (TMS) provides a direct and non-invasive measure of cortical excitability and connectivity in humans and may be employed to track over time pathological alterations, plastic changes and therapy-induced modifications in cortical circuits. However, the diagnostic/monitoring applications of this technique would be limited to the extent that TMS-evoked potentials are either stereotypical (non-sensitive) or random (non-repeatable) responses. Here, we used controlled changes in the stimulation parameters (site, intensity, and angle of stimulation) and repeated longitudinal measurements (same day and one week apart) to evaluate the sensitivity and repeatability of TMS/hd-EEG potentials. Methodology/Principal Findings In 10 volunteers, we performed 92 single-subject comparisons to evaluate the similarities/differences between pairs of TMS-evoked potentials recorded in the same/different stimulation conditions. For each pairwise comparison, we used non-parametric statistics to calculate a Divergence Index (DI), i.e., the percentage of samples that differed significantly, considering all scalp locations and the entire post-stimulus period. A receiver operating characteristic analysis showed that it was possible to find an optimal DI threshold of 1.67%, yielding 96.7% overall accuracy of TMS/hd-EEG in detecting whether a change in the perturbation parameters occurred or not. Conclusions/Significance These results demonstrate that the EEG responses to TMS essentially reflect deterministic properties of the stimulated neuronal circuits as opposed to stereotypical responses or uncontrolled variability. To the extent that TMS-evoked potentials are sensitive to changes and repeatable over time, they may be employed to detect longitudinal changes in the state of cortical circuits.

Buffer the Pain Away: Stimulating the Right Ventrolateral Prefrontal Cortex Reduces Pain Following Social Exclusion

Social exclusion hurts, literally. Indeed, various forms of social exclusion trigger a pain response (Eisenberger, Lieberman, & Williams, 2003). According to pain-overlap theories (Eisenberger et al., 2003; MacDonald & Leary, 2005), experiences of social and physical threat are processed similarly. Because belonging is critical for survival and reproduction (Baumeister & Leary, 1995), a system that uses similar signals for social and physical threats may have been evolutionarily advantageous. Supporting these theories, several studies have shown that social exclusion activates brain regions that process and regulate the unpleasantness of physical pain—including the dorsal anterior cingulate cortex (dACC) and the right ventrolateral prefrontal cortex (rVLPFC; Eisenberger et al., 2003). Whereas the dACC relates to the affective component of pain (Rainville, Duncan, Price, Carrier, & Bushnell, 1997), the rVLPFC is associated with the regulation of pain (Wager, Davidson, Hughes, Lindquist, & Ochsner, 2008). Accordingly, neuroimaging studies suggest that the rVLPFC inhibits pain resulting from social exclusion (Eisenberger et al., 2003; Kross, Egner, Ochsner, Hirsch, & Downey, 2007; Onoda et al., 2010). Yet whether a causal relationship exists between rVLPFC activity and feelings of social pain has until now been unknown. The experiment reported here provides the first proof of this causal relationship by showing that stimulating the rVLPFC reduces the pain of social exclusion. Specifically, we tested whether noninvasive brain polarization through transcranial direct current stimulation (tDCS) over rVLPFC, compared with sham stimulation over the same area, reduced pain following social exclusion.

The comprehension of idiomatic expressions in schizophrenic patients.

Recent fMRI and TMS studies on idiom comprehension have shown that the prefrontal cortex is involved in idiom processing. Since schizophrenic patients exhibit prefrontal structural changes and dysexecutive behavioural deficits, we hypothesised an impairment in idiom comprehension, correlating with performance on executive tasks. In this study, idiom comprehension was evaluated by means of a sentence-to-picture-matching task in 45 schizophrenic patients and 45 control subjects, matched for age and educational level. The task included 62 idiomatic and 62 literal sentences. Participants were presented with a written sentence, either literal or idiomatic, followed by a picture, which appeared below the sentence. They were instructed to judge whether the picture represented the meaning of the sentence or not, and responded by pressing one of two response keys. Half of the items correctly represented the meaning, half did not. Reaction times and accuracy were measured. Schizophrenics were impaired in both types of idiomatic sentence. However, their performance was particularly poor in the case of ambiguous idioms. Wisconsin Card Sorting Test and Digit Sequencing were the unique predictors of performance for idiom comprehension in general, while thought disorganization was not. Cognitive decline either did not appear to predict performance.

She runs, the road runs, my mind runs, bad blood runs between us: Literal and figurative motion verbs: An fMRI study

The role of sensory-motor components in language processing is a central topic in cognitive neuroscience. Recent studies showed that the processing of action words recruits cortical motor regions involved in the planning and execution of the described actions. However, it remains unclear to what extent the abstract versus concrete nature of the described motion modulates the activation of premotor and motor areas and how the agent affects this modulation. Here, we contribute to this line of research by investigating the comprehension of motion verbs, used in a literal versus figurative context, in an fMRI study with normal subjects in which the somatotopy of activation was investigated by presenting motion verbs that involve upper vs. lower limbs. A set of sentences including a motion verb used in a literal, fictive (only lower limb), metaphorical, or idiomatic way was studied. Cognition verbs were also included as control. We found that figurative sentences compared to literal ones produced a greater activation of a bilateral fronto-temporal network, in line with previous studies. Moreover, fictive motion activated a more posterior region, involving primary visual areas and motion sensitive visual areas, but also the left middle frontal gyrus. Crucially, the left precentral gyrus was activated in the case of the upper limb for literal and metaphorical motion sentence types, but not idiomatic sentences. For fictive motion, we found a lower limb-related somatotopic effect, also present for literal sentences, while the evidence for metaphorical and idiomatic sentences was less strong. In conclusion, our results confirm that premotor areas are activated by language understanding, but to a different degree depending on the specific literal versus figurative context in which motion verbs appear. Therefore, they support weak embodied views suggesting that the motor system enhances the comprehension of linguistically encoded actions.

Top-down interference and cortical responsiveness in face processing: A TMS-EEG study

Neuroimaging and electrophysiological studies have shown the involvement of a fronto-temporo-occipital network in face processing, but the functional relation among these areas remains unclear. We used transcranial magnetic stimulation combined with electroencephalography (TMS-EEG) to explore the local and global cortical excitability at rest and during two different face processing behavioral tasks. Single-pulse TMS was delivered (100 ms after face stimulus onset) over the right medial prefrontal cortex (mPFC) during a face identity or a face expression matching task, while continuous EEG was recorded using a 60-channel TMS-compatible amplifier. We examined TMS effects on the occipital face-specific ERP component and compared TMS-evoked potentials (TEPs) recorded during task performance and a passive point fixation control task. TMS reduced the P1-N1 component recorded at the occipital electrodes. Moreover, performing face tasks significantly modulated TEPs recorded at the occipital and temporal electrodes within the first 30 ms after right mPFC stimulation, with a specific increase of temporal TEPs in the right hemisphere for the facial expression task. Furthermore, in order to test the site-specificity of the reported effects, TMS was applied over the right premotor cortex (PMC) as a control site using the same experimental paradigm. Results showed that TMS over the right PMC did not affect ERP components in posterior regions during the face tasks and TEP amplitude did not change between task and no task condition, either at fronto-central electrodes near the stimulation or at temporal and occipital electrodes. These findings support the notion that the prefrontal cortex exerts a very early influence over the occipital cortex during face processing tasks and that excitability across right fronto-temporal cortical regions is significantly modulated during explicit facial expression processing.

A case for the involvement of phonological loop in sentence comprehension

The specific role of the phonological loop in sentence comprehension is still a matter of debate. We tested the behavioural consequences of activity disruption in left BA40 and BA44, key regions of the phonological loop, on language comprehension using 1Hz rTMS. Comprehension was assessed by means of two tasks: a sentence-to-picture matching task, with sentences varying in length and syntactic complexity (Experiment 1), and a sentence verification task (Experiment 2). rTMS over left BA40 significantly reduced accuracy for syntactically complex sentences and long, but syntactically simpler sentences, while rTMS over left BA44 significantly reduced accuracy only for syntactically complex sentences. rTMS applied over left BA40 also impaired performance on sentences in which word order was crucial. We suggest that the neural correlates of the phonological loop, left BA40 and BA44, are both involved in the comprehension of syntactically complex sentences, while only left BA40, corresponding to the short-term store, is recruited for the comprehension of long but syntactically simple sentences. Therefore, in contrast with the dominant view, we showed that sentence comprehension is a function of the phonological loop.

Cognitive Enhancement Induced by Anodal tDCS Drives Circuit-Specific Cortical Plasticity

Increasing evidence shows that anodal transcranial direct current stimulation (tDCS) enhances cognitive performance in healthy and clinical population. Such facilitation is supposed to be linked to plastic changes at relevant cortical sites. However, direct electrophysiological evidence for this causal relationship is still missing. Here, we show that cognitive enhancement occurring in healthy human subjects during anodal tDCS is affected by ongoing brain activity, increasing cortical excitability of task-related brain networks only, as directly measured by Transcranial Magnetic Stimulation combined with electroencephalography (TMS-EEG). Specifically, TMS-EEG recordings were performed before and after anodal tDCS coupled with a verbal fluency task. To control for effects of tDCS protocol and TMS target location, 3 conditions were assessed: anodal/sham tDCS with TMS over left premotor cortex, anodal tDCS with TMS over left posterior parietal cortex. Modulation of cortical excitability occurred only at left Brodmanns areas 6, 44, and 45, a key network for language production, after anodal tDCS and TMS over the premotor cortex, and was positively correlated to the degree of cognitive enhancement. Our results suggest that anodal tDCS specifically affects task-related functional networks active while delivering stimulation, and this boost of specific cortical circuits is correlated to the observed cognitive enhancement.

Electrified emotions: Modulatory effects of transcranial direct stimulation on negative emotional reactions to social exclusion

Social exclusion, ostracism, and rejection can be emotionally painful because they thwart the need to belong. Building on studies suggesting that the right ventrolateral prefrontal cortex (rVLPFC) is associated with regulation of negative emotions, the present experiment tests the hypothesis that decreasing the cortical excitability of the rVLPFC may increase negative emotional reactions to social exclusion. Specifically, we applied cathodal transcranial direct current stimulation (tDCS) over the rVLPFC and predicted an increment of negative emotional reactions to social exclusion. In Study 1, participants were either socially excluded or included, while cathodal tDCS or sham stimulation was applied over the rVLPFC. Cathodal stimulation of rVLPFC boosted the typical negative emotional reaction caused by social exclusion. No effects emerged from participants in the inclusion condition. To test the specificity of tDCS effects over rVLPFC, in Study 2, participants were socially excluded and received cathodal tDCS or sham stimulation over a control region (i.e., the right posterior parietal cortex). No effects of tDCS stimulation were found. Our results showed that the rVLPFC is specifically involved in emotion regulation and suggest that cathodal stimulation can increase negative emotional responses to social exclusion.

Localizing the effects of anodal tDCS at the level of cortical sources: A Reply to Bailey et al., 2015.

Leonor J. Romero Lauro , Alberto Pisoni , Mario Rosanova , Silvia Casarotto , Giulia Mattavelli , Nadia Bolognini a,d and Giuseppe Vallar a,d a Department of Psychology, University of Milano-Bicocca, Milano, Italy b Department of Biomedical and Clinical Sciences “L. Sacco”, University of Milano, Milano, Italy c Fondazione Europea per la Ricerca Biomedica, Milan, Italy d Neuropsychological Laboratory, IRCCS Istituto Auxologico Italiano, Milano, Italy