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Reduction of drive for thinness and body dissatisfaction in people with self-reported dysregulated eating behaviors after intermittent theta burst stimulation (iTBS) of the left dorsolateral prefrontal cortex
Full text linkAim: This study aimed to explore the effect of intermittent theta burst stimulation (iTBS) of the right and left dorsolateral prefrontal cortex (DLPFC) in people with self-reported dysregulated eating behaviors but without a diagnosis of eating disorders (EDs). Methods: Participants were randomly divided into two equivalent groups according to the side (right or left) of the hemisphere to be stimulated and they were tested before and after a single iTBS session. Outcome measurements were scores on self-report questionnaires assessing psychological dimensions related to eating behaviors (EDI-3), anxiety (STAI-Y), and tonic electrodermal activity. Results: The iTBS interfered with both psychological and neurophysiological measures. Significant variations of physiological arousal after iTBS of both the right and left DLPFC were witnessed by increased mean amplitude of non-specific skin conductance responses. With regard to the psychological measures, the iTBS on the left DLPFC significantly reduced the scores of the EDI-3 subscales drive for thinness and body dissatisfaction. Interestingly, these two scales are two of the three EDI-3 clinic scales (drive for thinness, body dissatisfaction, and bulimia) used as specific markers to assess the onset and/or maintenance of eating disorders. Conclusion: Our results show that the left DLPFC iTBS has an impact on the psychological dimensions that are risk factors for the onset of eating disorders, suggesting that an altered hemispheric asymmetry similar to that encountered in clinical populations is present in normal subjects even in the absence of clinical symptoms
Low-Frequency Repetitive Transcranial Magnetic Stimulation of the Right Dorsolateral Prefrontal Cortex Enhances Recognition Memory in Alzheimer’s Disease
No full textBackground: The lack of effective pharmacological or behavioral interventions for memory impairments associated with Alzheimer’s disease (AD) emphasizes the need for the investigation of approaches based on neuromodulation. Objective: This study examined the effects of inhibitory repetitive transcranial magnetic stimulation (rTMS) of prefrontal cortex on recognition memory in AD patients. Methods: In a first experiment, 24 mild AD patients received sham and real 1Hz rTMS over the left and right dorsolateral prefrontal cortex (DLPFC), in different sessions, between encoding and retrieval phases of a non-verbal recognition memory task. In a second experiment, another group of 14 AD patients underwent sham controlled repeated sessions of 1Hz rTMS of the right DLPFC across a two week treatment. Non-verbal recognition memory task was performed at baseline, at the end of the two weeks period and at a follow up of 1 month. Results: Right real rTMS significantly improved memory performance compared to right sham rTMS (p = 0.001). Left real rTMS left the memory performance unchanged as compared with left sham rTMS (p = 0.46). The two sham conditions did not differ between each other (p = 0.24). In the second experiment, AD patients treated with real rTMS showed an improvement of memory performance at the end of the two weeks treatment (p = 0.0009), that persisted at 1-month follow-up (p = 0.002). Conclusion: These findings provide evidence that inhibitory rTMS over the right DLPFC can improve recognition memory function in AD patients. They also suggest the importance of a new approach of non-invasive brain stimulation as a promising treatment in AD
Transcranial Magnetic Stimulation Trains at 1 Hz Frequency of the Right Posterior Parietal Cortex Facilitate Recognition Memory
Full text linkNeuroimaging, 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)
Improvement of phonemic fluency following leftward prism adaptation
Full text linkAnatomo 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
Modulation of memory by prism adaptation in healthy subjects
Full text link: Recent findings suggest that prism adaptation can extend its effects beyond spatial attention, modulating the performance of different cognitive tasks by acting on cerebellar, parietal and temporal-frontal networks. We tested groups of healthy subjects to investigate the effects of rightward vs. leftward prism adaptation vs. neutral lenses exposure in a series of memory tasks, probing either short-term (Digit span, Corsi span) or long-term memory (Supraspan verbal and spatial learning). In the short-term memory tasks, leftward prism adaptation selectively increased verbal span, while rightward prism adaptation increased spatial span. In the long-term memory tasks, leftward prism adaptation selectively increased verbal supraspan, i.e., increased the number of digits in the correct sequence reproduced and reduced the number of repetitions needed to learn the supraspan sequence. On the other hand, rightward prism adaptation selectively increased spatial supraspan, i.e. it increased the number of spatial positions in the correct sequence reproduced and reduced the number of repetitions needed to learn the supraspan sequence. Moreover, rightward, but not leftward, prism adaptation selectively increased supraspan recall after a delay interval, regardless of the stimulus material, i.e., it increased the number of digits or spatial positions recalled after a delay interval. Neutral lenses exposure did not influence any memory task. These findings suggest that prism adaptation can induce both modality/hemispheric-specific and process-specific effects on short-term and long-term explicit memory
Exploring the neural correlates of the reversed letter effect: evidence from left and right parietal patients
Full text linkTo investigate the hemispheric lateralization of attentional processes during visual search tasks depending on the stimulus material embedding the target, twelve patients with unilateral left (n = 7) or right (n = 5) parietal lesions and 20 age and education matched healthy controls (HC) were recruited. We used a visual search task for a uniquely tilted oblique bar embedded in an object shape 'N' or in its mirror reversal 'И'. The accuracy and the averaged reaction times (RTs) in each stimulus type ('N' or 'И') were analysed. HC presented significantly longer RTs when the target bar was embedded in 'N' among its mirror reversed 'И' (p < 0.05). This "reversed letter effect" was also found in the right parietal patients (p < .001), while no evidence of a reversed letter effect was found in the left parietal patients
De novo GRIN2A variants associated with epilepsy and autism and literature review
No full textN-methyl-D-aspartate receptors (NMDAR) are di-or tri-heterotetrameric ligand-gated ion channels composed of two obligate glycine-binding GluN1 subunits and two glutamate-binding GluN2 or GluN3 subunits, encoded by GRIN1, GRIN2A-D, and GRIN3A-B receptor genes respectively. Each NMDA receptor subtype has different temporal and spatial expression patterns in the brain and varies in the cell types and subcellular localization resulting in different functions. They play a crucial role in mediating the excitatory neurotransmission, but are also involved in neuronal development and synaptic plasticity, essential for learning, memory, and high cognitive functions. Among genes coding NMDAR subunits, GRIN2B is predominantly associated with neurodevelopmental disorders such as intellectual disability, developmental delay, autism, attention-deficit/hyperactivity disorder and, further, schizophrenia, Alzheimer's disease. The GRIN2A seems to be predominantly associated with a more definite phenotype including an epileptic spectrum ranging from Landau-Kleffner syndrome to benign childhood epilepsy with centrotemporal spikes, speech or language impairment, intellectual disability/developmental delay often in comorbidity. On the contrary, the occurrence of autism spectrum disorders, unlike GRIN2B- associated disorders, is questionable. To contribute to elucidate the latter issue and to better define the genotype/phenotype correlation, we report the clinical and neuropsychological profile of two patients featuring autism disorder, intellectual disability, language impairment, and focal epilepsy, associated with previously unreported heterozygous de novo GRIN2A pathogenic variants. We hypothesize that the unusual phenotype may be the result of interactions of tri-heterotetrameric 2GluN1/ GluN2A-D/ GluN3A-B subunits with mutated GluN2A subunit and/or the dysfunction may be influenced by other unknown modifier genes and/or environmental factors. (c) 2022 Published by Elsevier Inc
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