Search results for "Brain function"
showing 10 items of 135 documents
Children show hemispheric differences in the basic auditory response properties
2019
Auditory cortex in each hemisphere shows preference to sounds from the opposite hemifield in the auditory space. Besides this contralateral dominance, the auditory cortex shows functional and structural lateralization, presumably influencing the features of subsequent auditory processing. Children have been shown to differ from adults in the hemispheric balance of activation in higher-order auditory based tasks. We studied, first, whether the contralateral dominance can be detected in 7- to 8-year-old children and, second, whether the response properties of auditory cortex in children differ between hemispheres. Magnetoencephalography (MEG) responses to simple tones revealed adult-like cont…
In vivo definition of parieto-motor connections involved in planning of grasping movements
2010
We combined bifocal transcranial magnetic stimulation (TMS) and diffusion tensor imaging (DTI) tractography to investigate in humans the contribution of connections originating from different parietal areas in planning of different reaching to grasp movements. TMS experiments revealed that in the left hemisphere functional connectivity between the primary motor cortex (M1) and a portion of the angular gyrus (AG) close to the caudal intraparietal sulcus was activated during early preparation of reaching and grasping movements only when the movement was made with a whole hand grasp (WHG) towards objects in contralateral space. In contrast, a different pathway, linking M1 with a part of the su…
Hyperexcitability of parietal-motor functional connections in the intact left-hemisphere of patients with neglect
2008
Hemispatial neglect is common after unilateral brain damage, particularly to perisylvian structures in the right-hemisphere (RH). In this disabling syndrome, behaviour and awareness are biased away from the contralesional side of space towards the ipsilesional side. Theoretical accounts of this in terms of hemispheric rivalry have speculated that the intact left-hemisphere (LH) may become hyper-excitable after a RH lesion, due to release of inhibition from the damaged hemisphere. We tested this directly using a novel twin-coil transcranial magnetic stimulation (TMS) approach to measure excitability within the intact LH of neglect patients. This involved applying a conditioning TMS pulse ove…
Rapid changes in brain activity during learning of grapheme-phoneme associations in adults
2020
ABSTRACTLearning to associate written letters with speech sounds is crucial for the initial phase of acquiring reading skills. However, little is known about the cortical reorganization for supporting letter-speech sound learning, particularly the brain dynamics during the learning of grapheme-phoneme associations. In the present study, we trained 30 Finnish participants (mean age: 24.33 years, SD: 3.50 years) to associate novel foreign letters with familiar Finnish speech sounds on two consecutive days (first day ~ 50 minutes; second day ~ 25 minutes), while neural activity was measured using magnetoencephalography (MEG). Two sets of audiovisual stimuli were used for the training in which …
Anosognosia for hemiparesis after left-sided stroke
2014
In patients with left-sided lesions, anosognosia for hemiparesis (AHP) seems to be a rare phenomenon. It has been discussed whether this rareness might be due to an inevitable bias due to language dysfunction and whether the left hemisphere's role for our self-awareness of motor actions thus is underestimated. By applying functional magnetic resonance imaging (fMRI) we examined whether patients with AHP following a left hemisphere stroke show a regular, left-sided or a reversed, right-sided lateralization of language functions. Only the former observation would argue for an original role of the left hemisphere in self-awareness about limb function. In a consecutive series of 44 acute left-s…
The test accuracy of the Montreal Cognitive Assessment (MoCA) by stroke lateralisation
2017
Abstract Background The Montreal Cognitive Assessment (MoCA) is an increasingly popular screening tool for detecting cognitive impairment post-stroke. However its' test accuracy by stroke lateralisation is as yet unknown. Aim Our aim was to investigate whether the test accuracy of the MoCA differs by stroke lateralisation across different cognitive domains. Methods We retrospectively examined the cognitive profiles of 228 subacute stroke patients (86 Left, 142 Right), comparing MoCA-total and domain-specific scores with performance on detailed neuropsychological assessment. Results The prevalence of cognitive impairment detected on neuropsychological assessment was high and relatively compa…
Does mismatch negativity show differences in reading-disabled children compared to normal children and children with attention deficit?
2007
An auditory event-related potential (ERP) component called mismatch negativity (MMN) was examined in three groups of children (n = 63) aged 8-14 years. A control group comprised healthy children in second or sixth grade of comprehensive school (n = 21). The two clinical groups included children with reading disability (RD) (n = 21) and children with attention deficit (AD) (n = 21). MMN was elicited in a passive oddball paradigm by duration changes in a continuous sound, consisting of two alternating (600 and 800 Hz) 100 msec tones. The deviant tones were either 30 or 50 msec in duration. Both deviants elicited a clear MMN in all groups. Statistical analyses showed no systematic difference i…
Mismatch negativity (MMN) elicited by duration deviations in children with reading disorder, attention deficit or both.
2007
According to several studies auditory discrimination as measured by mismatch negativity (MMN) is compromised in participants with reading disorder. However, studies on duration discrimination have produced conflicting findings [Baldeweg, T., Richardson, A., Watkins, S., Foale, C., & Gruzelier, J., 1999. Impaired auditory frequency discrimination in dyslexia detected with mismatch evoked potentials. Annals of Neurology, 4, 1-9; Corbera, S., Escera, C., & Artigas, J., 2006. Impaired duration mismatch negativity in developmental dyslexia. Neuroreport, 17, 1051-1055]. Auditory sensitivity has not been as actively investigated among children with attention deficit, although attention problems of…
Differential involvement of the left frontal and temporal regions in verb naming: A tDCS treatment study
2012
Purpose: In aphasic patients, some studies have already emphasized the efficacy of transcranial direct current stim- ulation (tDCS) during the treatment of noun retrieval deficits. To date, in the same population, there are have been no studies addressing tDCS effects in the recovery of verb retrieval deficits. In this study, we wanted to test the potential of tDCS to improve verb production in a group of aphasic patients. Methods: Seven chronic subjects participated in an intensive language training for their difficulties in action naming. Each subject was treated with tDCS (20 min., 1 mA) over the left hemisphere in three different conditions: anodic tDCS over Wernicke's area, anodic tDCS…
Hemodynamic responses to speech and music in newborn infants
2009
We used near‐infrared spectroscopy (NIRS) to study responses to speech and music on the auditory cortices of 13 healthy full‐term newborn infants during natural sleep. The purpose of the study was to investigate the lateralization of speech and music responses at this stage of development. NIRS data was recorded from eight positions on both hemispheres simultaneously with electroencephalography, electrooculography, electrocardiography, pulse oximetry, and inclinometry. In 11 subjects, statistically significant (P < 0.02) oxygenated (HbO(2)) and total hemoglobin (HbT) responses were recorded. Both stimulus types elicited significant HbO(2) and HbT responses on both hemispheres in five subjec…