Abstract: Although signed and speech-based languages have a similar internal organization of verbal short-term memory, sign span is lower than word span. We investigated whether this is due to the fact that signs are not suited for serial recall, as proposed by Bavelier, Newport, Hall, Supalla, and Boutla (2008. Ordered short-term memory differs in signers and speakers: Implications for models of short-term memory. Cognition, 107, 433-459). We administered a serial recall task with stimuli in Italian Sign Language to 12 deaf people, and we compared their performance with that of twelve age-, gender-, and education-matched hearing participants who performed the task in Italian. The results do not offer evidence for the hypothesis that serial order per se is a detrimental factor for deaf participants. An alternative explanation for the lower sign span based on signs being phonologically heavier than words is considered.
Abstract: Stereotypes associated with gender, race, ethnicity and religion are powerful forces in human social interactions. Previous neuroimaging and neuropsychological studies point to a role of the prefrontal cortex in controlling stereotypical responses. Here we used transcranial magnetic stimulation (TMS) in combination with an Implicit Association Task (IAT) to highlight the possible causal role of the left dorsolateral prefrontal cortex (DLPFC) and the right anterior dorsomedial prefrontal cortex (aDMPFC) in controlling gender-stereotypical responses. Young male and female participants were tested. Our results showed that applying TMS over the left DLPFC and the right aDMPFC increased the gender-stereotypical bias in male participants compared to when TMS was applied to a control site (vertex). This suggests that both the left DLPFC and the right aDMPFC play a direct role in stereotyping. Females did not show a significant gender bias on the IAT; correspondingly their responses were unaffected by TMS.
Abstract: 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.
Abstract: The brain's plasticity in response to sensory deprivation and other perturbations is well established. While the functional properties of the reorganized areas are under vigorous investigation, the factors that constrain cortical reorganization remain poorly understood. One factor constraining such reorganization may be long-distance subcortical connectivity between relevant cortical regions-reorganization attempts to preserve the functionality of subcortical connections. Here we provide human neurophysiological evidence for the role of the subcortical connections in shaping cortical reorganization of the networks involved in object naming following perturbation of normal function. We used direct electrical stimulation (DES) during surgical removal of gliomas to identify the sites that are involved in naming different categories of objects. The sites that were selectively inhibited in naming either living or non-living objects were displaced relative to those observed with other subject populations, possibly reflecting cortical reorganization due to slowly evolving brain damage. Subcortical DES applied to the white matter underlying these regions also led to category-specific naming deficits. The existence of these subcortical fiber pathways was confirmed using diffusion tensor tractography. These results constitute the first neurophysiological evidence for the critical role of subcortical pathways as part of the neural circuits that are involved in object naming; they also highlight the importance of subcortical connectivity in shaping cortical reorganization following perturbations of normal function.
Abstract: The medial prefrontal cortex (mPFC) and the right somatosensory cortex (rSC) are known to be involved in emotion processing and face expression recognition, although the possibility of segregated circuits for specific emotions in these regions remains unclear. To investigate this issue, we used transcranial magnetic stimulation (TMS) together with a priming paradigm to modulate the activation state of the mPFC and the rSC during emotional expressions discrimination. This novel paradigm allows analyzing how TMS interacts with the ongoing activity of different neuronal populations following prime processing. Participants were asked to discriminate between angry and happy faces that were preceded by a congruent prime (a word expressing the same emotion), an incongruent prime (a word expressing the opposite emotion) or a neutral prime. In TMS trials, a single pulse was delivered over the mPFC, rSC or Vertex (control site) between prime and target presentation. TMS applied over the mPFC significantly affected the priming effect, by selectively increasing response latencies in congruent trials. This indicates that the mPFC contains different neural representations for angry and happy expressions. TMS over rSC did not significantly affect the priming effect, suggesting that rSC is not involved in processing verbal emotional stimuli.
Abstract: 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.
Abstract: Previous studies found mixed results concerning the role of working memory (WM) in the gambling task (GT). Here, we aimed at reconciling inconsistencies by showing that the standard version of the task can be solved using intuitive strategies operating automatically, while more complex versions require analytic strategies drawing on executive functions. In Study 1, where good performance on the GT could be achieved using intuitive strategies, participants performed well both with and without a concurrent WM load. In Study 2, where analytical strategies were required to solve a more complex version of the GT, participants without WM load performed well, while participants with WM load performed poorly. In Study 3, where the complexity of the GT was further increased, participants in both conditions performed poorly. In addition to the standard performance measure, we used participants' subjective expected utility, showing that it differs from the standard measure in some important aspects.
Abstract: Low-grade gliomas are slow growing intrinsic lesions that induces a progressive functional reshaping of the brain. Surgical removal of these lesions requires the combined efforts of a multidiscipinary team of neurosurgeon, neuroradiologist, neuropsychologist, neurophysiologist, and neurooncologists that all together contribute in the definition of the location, extension, and extent of functional involvement that a specific lesion has induced in a particular patient. Each tumor has induced particular and specific changes of the functional network, that varies among patients. This requires that each treatment plan should be tailored to the tumor and to the patient. When this is reached, surgery should be accomplished according to functional and anatomical boundaries, and has to aim to the maximal resection with the maximal patient functional preservation. This can be reached at the time of the initial surgery, depending on the functional organization of the brain, or may require additional surgeries, eventually intermingled with adjuvant treatments. The use of so called brain mapping techniques extend surgical indications, improve extent of resection with greater oncological impact, minimization of morbidity and increase in quality of life. To achieve the goal of a satisfactory tumor resection associated with the full preservation of the patients abilities, a series of neuropsychological, neurophysiological, neuroradiological and intraoperative investigations have to be performed. In this chapter, we will describe the rationale, the indications and the modality for performing a safe and rewarding surgical removal of low-grade gliomas by using these techniques, as well as the functional and oncological results.
Abstract: 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.
Abstract: This article describes the rationale, indications, and modality for intraoperative brain mapping for safe and effective surgical removal of tumors located within functional brain areas.
