Overestimation of Phonological Judgments on the Right Side of Space

Spatial attentional biases can be observed during the processing of linguistic material. For example, we previously reported that healthy subjects overestimate the semantic distance between word stimuli in the right vs. left space. Here, we explored whether or not attentional biases are also observed in tasks requiring an evaluation of phonological distance between words in the right and left hemifield. Forty-one healthy subjects were presented with triplets of words arranged in space and were asked to indicate the side of the space in which the phonological distance between the middle word and an outer word was smaller. In Experiment 1, real words and pseudowords were used, while in Experiment 2, only pseudowords and consonant strings were used. Subjects overestimated the phonological distance between the middle and outer words in the right space. These findings were specific to word stimuli. These results are consistent with the idea that semantic and phonological information may be internally mapped onto spatial representations

Modulating memory performance in healthy subjects with Trancranial Direct Current Stimulation over the right dorsolateral prefrontal cortex

Objective The role of the Dorsolateral Prefrontal Cortex (DLPFC) in recognition memory has been well documented in lesion, neuroimaging and repetitive Transcranial Magnetic Stimulation (rTMS) studies. The aim of the present study was to investigate the effects of transcranial Direct Current Stimulation (tDCS) over the left and the right DLPFC during the delay interval of a non-verbal recognition memory task. Method 36 right-handed young healthy subjects participated in the study. The experimental task was an Italian version of Recognition Memory Test for unknown faces. Study included two experiments: in a first experiment, each subject underwent one session of sham tDCS and one session of left or right cathodal tDCS; in a second experiment each subject underwent one session of sham tDCS and one session of left or right anodal tDCS. Results Cathodal tDCS over the right DLPFC significantly improved non verbal recognition memory performance, while cathodal tDCS over the left DLPFC had no effect. Anodal tDCS of both the left and right DLPFC did not modify non verbal recognition memory performance. Conclusion Complementing the majority of previous studies, reporting long term memory facilitations following left prefrontal anodal tDCS, the present findings show that cathodal tDCS of the right DLPFC can also improve recognition memory in healthy subjects

Transcranial Magnetic Stimulation Trains at 1 Hz Frequency of the Right Posterior Parietal Cortex Facilitate Recognition Memory

Neuroimaging, neuropsychological, and brain stimulation studies have led to contrasting findings regarding the potential roles of the lateral parietal lobe in episodic memory. Studies using brain stimulation methods reported in the literature do not offer unequivocal findings on the interactions with stimulation location (left vs. right hemisphere) or timing of the stimulation (encoding vs. retrieval). To address these issues, active and sham 1 Hz repetitive transcranial magnetic stimulation (rTMS) trains of 600 stimuli were applied over the right or left posterior parietal cortex (PPC) before the encoding or before the retrieval phase of a recognition memory task of unknown faces in a group of 40 healthy subjects. Active rTMS over the right but not the left PPC significantly improved non-verbal recognition memory performance without any significant modulation of speed of response when applied before the retrieval phase. In contrast, rTMS over the right or the left PPC before the encoding phase did not modulate memory performance. Our results support the hypothesis that the PPC plays a role in episodic memory retrieval that appears to be dependent on both the hemispheric lateralization and the timing of the stimulation (encoding vs. retrieval)

Impairments in top down attentional processes in right parietal patients: Paradoxical functional facilitation in visual search

AbstractIt is well known that the right posterior parietal cortex (PPC) is involved in attentional processes, including binding features. It remains unclear whether PPC is implicated in top-down and/or bottom-up components of attention. We aim to clarify this by comparing performance of seven PPC patients and healthy controls (HC) in a visual search task involving a conflict between top-down and bottom-up processes. This task requires essentially a bottom-up feature search. However, top-down attention triggers feature binding for object recognition, designed to be irrelevant but interfering to the task. This results in top-down interference, prolonging the search reaction time. This interference was indeed found in our HCs but not in our PPC patients. In contrast to HC, the PPC patients showed no evidence of prolonged reactions times, even though they were slower than the HCs in search tasks without the conflict. This finding is an example of paradoxical functional facilitation (PFF) by brain damage. The PFF effect enhanced our patients’ performance by reducing the top down interference. Our finding supports the idea that right PPC plays a crucial role in top-down attentional processes. In our search tasks, right PPC induces top-down interference either by directing spatial attention to achieve viewpoint invariance in shape recognition or by feature binding

Enhancing memory performance with rTMS in healthy subjects and individuals with Mild Cognitive Impairment: the role of the right dorsolateral prefrontal cortex

A debated question in the literature is the degree of anatomical and functional lateralization of the executive control processes sub-served by the dorsolateral prefrontal cortex (DLPFC) during recognition memory retrieval. We investigated if transient inhibition and excitation of the left and right DLPFC at retrieval by means of repetitive transcranial magnetic stimulation (rTMS) modulate recognition memory performance in 100 healthy controls (HCs) and in eight patients with Mild Cognitive Impairment (MCI). Recognition memory tasks of faces, buildings, and words were used in different experiments. rTMS-inhibition of the right DLPFC enhanced recognition memory in both HCs and MCIs. rTMS-excitation of the same region in HCs deteriorated memory performance. Inhibition of the right DLPFC could modulate the excitability of a network of brain regions, in the ipsilateral as well as in the contralateral hemisphere, enhancing function in HCs or restoring an adaptive equilibrium in MCI

Improvement of phonemic fluency following leftward prism adaptation

Anatomo functional studies of prism adaptation (PA) have been shown to modulate a brain frontal-parieto-temporal network, increasing activation of this network in the hemisphere ipsilateral to the side of prism deviation. This effect raises the hypothesis that left prism adaptation, modulating frontal areas of the left hemisphere, could modify subjects' performance on linguistic tasks that map on those areas. To test this hypothesis, 51 healthy subjects participated in experiments in which leftward or rightward prism adaptation were applied before the execution of a phonemic fluency task, i.e., a task with strict left hemispheric lateralization onto frontal areas. Results showed that leftward PA significantly increased the number of words produced whereas rightward PA did not significantly modulate phonemic fluency. The present findings document modulation of a language ability following prism adaptation. The results could have a huge clinical impact in neurological populations, opening new strategies of intervention for language and executive dysfunctions

Boosting Phonological Fluency Following Leftward Prismatic Adaptation: A New Neuromodulation Protocol for Neurological Deficits?

Prism adaptation (PA) has been recently shown to modulate a brain frontal-parieto-temporal network, with an increase of excitation of this network in the hemisphere ipsilateral to the side of prismatic deviation. This effect raises the hypothesis that left prismatic adaptation, modulating the excitability of frontal areas of the left hemisphere could modulate subjects’ performance on linguistic tasks that map on those areas. To test this hypothesis, sixty-one healthy subjects participated in experiments in which leftward, rightward or no-PA were applied before the execution of a phonological fluency task, i.e. a task with the strict left hemispheric lateralization and mapping onto frontal areas. Leftward-PA significantly increased the number of words produced compared with the pre-PA (p = .0017), R-PA (p=.00013) and no-PA (p=.0005) sessions. In contrast, rightward-PA did not significantly modulate phonological fluency compared with the pre-PA (p = .92) and no-PA (p = .99) sessions. The effect of leftward PA on phonological fluency correlated with the magnitude of spatial aftereffect, i.e. the spatial bias towards the side of space opposite to prismatic deviation following prisms removal (r = .51; p = .04). The present findings document for the first time modulation of a language ability following prismatic adaptation. The results could have a huge clinical impact on neurological populations, opening new strategies of intervention for language and executive dysfunctions

Verbal Fluency in Mild Alzheimer's Disease: Transcranial Direct Current Stimulation over the Dorsolateral Prefrontal Cortex

Background: Recent studies showed that in healthy controls and in aphasic patients inhibitory trains of repetitive transcranial magnetic stimulation (rTMS) over the right prefrontal cortex can improve phonemic fluency performance, while anodal transcranial direct current stimulation (tDCS) over the left prefrontal cortex can improve performance in naming and semantic fluency tasks. Objective: This study aimed at investigating the effects of cathodal tDCS over the left or the right dorsolateral prefrontal cortex (DLPFC) on verbal fluency tasks (VFT) in patients with mild Alzheimer’s Disease (AD). Methods: Forty mild AD patients participated in the study (mean age 73.17 ± 5.61 years). All participants underwent cognitive baseline tasks and a VFT twice. Twenty patients randomly received cathodal tDCS to the left or the right DLPFC, and twenty patients were assigned to a control group in which only the two measures of VFT were taken, without the administration of the tDCS. Results: A significant improvement of performance on the VFT in AD patients was present after tDCS over the right DLPFC (p=.001). Instead, no difference was detected between the two VFTs sessions after tDCS over the left DLPFC (p=.42). Furthermore, these results cannot be related to task learning effects, since no significant difference was found between the two VFT sessions in the control group (p= .73). Conclusions: These data suggest that tDCS over DLPFC can improve VFT performance in AD patients. A hypothesis is that tDCS enhances adaptive patterns of brain activity between functionally connected areas

Long-term Memory of Sensory Experiences from the First Pregnancy, its Peri-partum and Post-partum in Women with Autism Spectrum Disorders without Intellectual Disabilities: A Retrospective Study

Purpose: To explore the recalled experience of pregnancy and motherhood in women diagnosed with Autism Spectrum Disorders (ASD) without intellectual disabilities, focusing on sensory perceptions and mood. Methods: We retrospectively evaluated, through an ad-hoc structured interview, the sensory sensitivity during the pre-partum, the peri-partum, and the post-partum of thirty-three mothers with ASD and thirty-two neurotypical mothers. Participants also underwent a psychometric assessment about autistic traits, general sensory sensitivity, and post-partum depressive symptomatology. Results: Mothers with ASD recalled a higher sensitivity than the comparison group across the three time-points; however, during the peri-partum their recalled hypersensitivity decreases, and in the post-partum it returned as high as before childbirth. The difference in the length of recall between groups did not statistically influence our results. Higher levels of autistic traits correlated with higher depressive post-partum symptomatology. Conclusions: Mothers with ASD seem to recall their experience of pregnancy, childbirth, and post-partum period differently from neurotypical mothers, particularly in terms of hypersensitivity. The correlation with depressive symptoms and the potential role of oxytocin and of long-term memory (encoding and recollection) are discussed. Further exploring these aspects might give fundamental hints to provide tailored support to mothers with ASD during pregnancy and motherhood

Motor and Linguistic Linking of Space and Time in the Cerebellum

Background: Recent literature documented the presence of spatial-temporal interactions in the human brain. The aim of the present study was to verify whether representation of past and future is also mapped onto spatial representations and whether the cerebellum may be a neural substrate for linking space and time in the linguistic domain. We asked whether processing of the tense of a verb is influenced by the space where response takes place and by the semantics of the verb. Principal Findings: Responses to past tense were facilitated in the left space while responses to future tense were facilitated in the right space. Repetitive transcranial magnetic stimulation (rTMS) of the right cerebellum selectively slowed down responses to future tense of action verbs; rTMS of both cerebellar hemispheres decreased accuracy of responses to past tense in the left space and to future tense in the right space for non-verbs, and to future tense in the right space for state verbs. Conclusions: The results suggest that representation of past and future is mapped onto spatial formats and that motor action could represent the link between spatial and temporal dimensions. Right cerebellar, left motor brain networks could be part of the prospective brain, whose primary function is to use past experiences to anticipate future events. Bot