M. Oliveri

Contralateral neglect induced by right posterior parietal rTMS in healthy subjects.

&NA; We applied repetitive transcranial magnetic stimulation (rTMS) in order to induce interference on visuo‐spatial perception in 11 healthy subjects. Subjects performed a visuo‐spatial task requiring judgements about the symmetry of prebisected lines. Visual stimuli consisted of symmetrically or asymmetrically transected lines, tachystoscopically presented for 50 ms on a computer‐monitor. Performance was examined in basal condition and during rTMS trains of 10 stimuli at 25 Hz, delivered through a focal coil over right or left posterior parietal cortex (P5 and P6 sites) and triggered synchronously with visual stimulus. Randomly intermixed sham rTMS trains were employed to control for non‐specific effects. Right parietal rTMS induced a significant rightward bias in symmetry judgements as compared with basal and sham rTMS conditions. No differences emerged between other conditions.

1 Hz repetitive transcranial magnetic stimulation of the unaffected hemisphere ameliorates contralesional visuospatial neglect in humans

The aim of the study was to investigate whether low-frequency repetitive transcranial magnetic stimulation (rTMS) over the unaffected hemisphere can ameliorate visuospatial neglect. We treated three right brain damaged patients with left neglect. 900 pulses (1 Hz frequency) were given over left posterior parietal cortex every other day for 2 weeks. Patients performed a computerized task requiring length judgement of prebisected lines, tachistoscopically presented for 150 ms. With respect to rTMS the task was given 15 days before, at the beginning, at the end and 15 days after. At these times patients performed also line bisection and clock drawing tasks. rTMS induced a significant improvement of visuo-spatial performance that remained quite unchanged 15 days after. Patients performance at Time 3 and 4 improved also as concerns line bisection and clock drawing tasks.

rTMS of the unaffected hemisphere transiently reduces contralesional visuospatial hemineglect

To verify the role of interhemispheric influences on manifestations of neglect, the authors investigated the effects of a transient repetitive transcranial magnetic stimulation (rTMS)-induced disruption of the unaffected hemisphere on contralesional visuospatial neglect in two left- and five right-brain-damaged patients. Parietal rTMS of the unaffected hemisphere during the execution of a computerized task of bisected line’s length judgment transiently decreased the magnitude of neglect as expressed in the number of errors.

Magnetic stimulation study during observation of motor tasks

The aim of the study was to assess if the observation of single or more complex muscle movements activates the premotor cortex in man. We stimulated by transcranial magnetic stimulation the right and left motor cortex recording from the abductor pollicis brevis of eight normal subjects, during observation of different movements performed by the examiner: (1) single movements: thumb abduction, arm elevation; (2) motor sequences: finger opposing movements performed in an ordinate sequence: 1-2, 1-3, 1-4, 1-5, 1-2ellipsis, and in a non-consecutive non-repetitive order: 1-3, 1-5, 1-4, 1-2, 1-5, 1-2ellipsis We found an increased excitability of the right cortex during observation of isolated muscle movement regardless of which muscle is moved. At the stimulation of the left cortex, MEPs were significantly increased during observation of complex muscular synergies.

Reorganization of cortical motor area in prior polio patients

OBJECTIVE Focal transcranial magnetic stimulation (TMS) was used to study the motor maps of upper limb muscles in 7 adult patients with a history of paralytic poliomyelitis. The aim of the study was to verify the potential for long-term cortical reorganization of a selective peripheral motor neuron lesion suffered early in life. METHODS Patient selection was based on the prevalent involvement of proximal muscles in only one of the upper limbs. Motor evoked potentials (MEPs) were recorded from deltoid and abductor pollicis brevis (APB) muscles. Each muscle map was characterized by area (no. of excitable positions), volume (the sum of MEP amplitudes at all scalp positions), maximal amplitude (the highest MEP recorded). RESULTS In the patients, the mean area, volume and maximal amplitude were significantly greater in affected vs. contralateral deltoid (P<0.05) and vs. controls (P<0.01). No significant differences were found in APB map parameters. The APB/deltoid ratio for area was lower in the affected compared with the unaffected side and controls (P = 0.06). Cortical reorganization was not significantly correlated with motor performance. CONCLUSION These findings are consistent with a rearrangement in human motor pathways targeting muscles affected by a lower motor neuron lesion.

Magnetic stimulation study in patients with myotonic dystrophy

To further define motor nervous system alterations in myotonic dystrophy (MD), motor potentials to transcranial and cervical magnetic stimulation (MEPs) were recorded from the right abductor pollicis brevis muscle in 10 patients with MD and in 10 healthy controls. Cortical and cervical latencies, central motor conduction time (CMCT), stimulus threshold intensity and cortical MEP amplitudes expressed both as absolute values and as %M were analysed. MEP cervical latency, absolute or relative amplitude and excitability threshold did not significantly differ in patients and controls. The mean cortical motor latency and CMCT were significantly prolonged in MD patients with respect to normal subjects. Moreover, CMCTs were found to be significantly related to stimulus threshold intensity (P = 0.03) and only marginally related to absolute cortical amplitude (P = 0.06). These findings are indicative of a central motor delay, also related to decreased excitability of motor neurons, in patients with MD. No correlations were found between individual neurophysiological parameters and age, duration of disease and clinical impairment. Our results suggest that magnetic stimulation studies can detect subclinical dysfunctions of the central motor system in MD patients, as one of the multisystemic manifestations of the disease, rather independent of the primitive muscle damage.

P258 Combining tDCS with prismatic adaptation for non invasive neuromodulation of the motor cortex

Introduction Prismatic adaptation (PA) shifts visual field laterally and induces lateralized deviations of spatial attention. Recently, it has been suggested that prismatic goggles are also able to modulate brain excitability ( Magnani, 2014 ), with cognitive after-effects documented even in tasks not necessarily spatial in nature ( Oliveri, 2013 ). Objectives The aim of the present study was to test whether prisms can modulate motor cortical excitability similarly as anodal transcranial direct current stimulation (tDCS) does; to test whether neuromodulatory effects obtained from tDCS and prismatic goggles could interact and induce homeostatic changes in brain excitability. Materials and methods Twenty-four subjects were submitted to single-pulse transcranial magnetic stimulation (TMS) over the right M1 to measure their Input–Output (IO) curve as a measure of cortical excitability ( Carroll, 2011 ). Assessment was made in three experimental groups: before and after rightward PA; before and after atDCS of the right M1; before and after rightward PA and atDCS of the right M1. Results A significant increase of the steepness of the IO curve slope on the right motor cortex was found following either rightward PA or atDCS; on the other hand, a decrease of the steepness of the IO curve slope was found after the combination of rightward PA and atDCS. Conclusion These findings suggest that PA could be an additional tool to modulate cortical plasticity in motor cortices and that an increase or a decrease in corticospinal excitability depends on the functional state of the M1 before or at the time of conditioning ( Lang, 2004 ).

P 61. Is high frequency rTMS a new tool in remediating dyslexia

Introduction Evidence from functional neuroimaging has reported hypoactivation of the left parieto-temporal regions in children and adults with dyslexia when they engage in reading-related tasks (Shaywitz et al., 2002; Richlan et al., 2011). Studies on the remediation of dyslexia have consistently found that remedial treatment improves reading ability and increases activation in critical brain areas (Temple et al., 2003; Hoeft et al., 2011). Objectives We wanted to determine whether high frequency repetitive trancranial magnetic stimulation (hf-rTMS) over areas that are underactive in dyslexics during reading, such as the left superior temporal gyrus (STG) and the left inferior parietal lobe (IPL), would improve the reading performance of dyslexic adults. Materials and methods Ten dyslexics performed three reading tasks (reading aloud words, non-words and text) in seven experimental conditions: following 5Hz-rTMS over the IPL and STG (target sites) bilaterally (left and right hemisphere); following 5Hz-rTMS over the vertex (control site); in two conditions without rTMS (no-TMS or baseline). Reading accuracy (number of errors) and speed (onset reaction times-RTs-for word and non-word reading; number of syllables read in the text per second-syll/sec) were calculated. Stimulus consisted of seven sets of 30 words (15 trisyllabic and 15 disyllabic) with high frequency in Italian written texts, 30 non-words (15 trisyllabic and 15 disyllabic), and texts over 600 syllables long. Brain stimulation consisted of ten rTMS trains of 50 stimuli at 5-Hz frequency (stimulation time, 10s); stimuli were delivered at 100% of the motor threshold. The coil was placed tangential to the skull over P3, P4, P5 and P6 of the 10–20 EEG system and over the vertex. Results Non-word reading errors after both left and right IPL stimulations were significantly fewer than all other conditions. Text reading errors following L-STG stimulation were fewer than all other conditions. Word-reading RTs after left STG stimulation were shorter than all other conditions. Furthermore, non-word reading RTs after left IPL stimulation were shorter than Vertex and Baseline, but not than other conditions. Notably, no differences emerged between the Vertex and mean Baseline thus indicating the absence of unspecific effects related to rTMS per se. Conclusion The study shows that hf-rTMS is effective in improving the reading accuracy and speed of dyslexics and that the effect is strictly task-related and site-specific. To the best of our knowledge, this is the first study which demonstrates that distinctive facilitation of neural pathways known to be underactive in dyslexics improves their reading performance. Although preliminary, these findings could suggest new treatment perspectives for the development of long-term specific treatments for dyslexia.