The posterior parietal cortex in visuospatial attention:study with continuous theta burst stimulation / 中华物理医学与康复杂志

Objective To seek more direct evidence of the role of the posterior parietal cortex (PPC) in controlling visuospatial attention.Methods Forty healthy subjects took the Attention Network Test following continuous theta burst stimulation (cTBS) applied over the left or right PPC or sham stimulation.The Attention Network Test measures the alerting,orienting and executive control components of visual attention separately.Results Subjects responded to spatial cues significantly slower after cTBS.Alerting and orienting showed deficits after cTBS over the right PPC.cTBS over the left PPC resulted in significant improvements in alerting,but not in the orienting.Furthermore,there were significant differences in the alerting and orienting indices between cTBS over the left and right PPC,but not in the executive control index.Conclusions The results suggest that the right PPC is associated with spatial orienting and the alerting function.The findings supported the theory of inter-hemispheric competition for visuospatial attention.Visuospatial attention bias might be selectively modulated through cTBS.

Cognitive mechanisms and motor control during a saccadic eye movement task: evidence from quantitative electroencephalography / Mecanismos cognitivos e controle motor durante uma tarefa de movimento sacádico dos olhos: evidências de eletroencefalografia quantitativa

The saccadic movement is an important behavioral measure used to investigate several cognitive processes, including attention and sensorimotor integration. The present study aimed at investigating changes in beta coherence over frontal, motor, occipital, and parietal cortices during the performance of two different conditions of a prosacadic paradigm. The conditions involved a different pattern of stimulus presentation: a fixed and random stimulus presentation. Twelve healthy volunteers (three male, mean age of 26.25 (SD=4.13) performed the task, while their brain activity pattern was recorded using quantitative electroencephalography. The results showed an interaction between factors condition and moment for the pair of electrode C3/C4. We observed a main effect for moment to CZ/C4, FZ/F3, and P3/PZ. We also found a main effect for condition to FZ/F4, P3/P4, and O1/O2. Our results demonstrated an important role of the inter-connection of the two hemispheres in visual search and movement preparation. The study demonstrates an automation of action and reduction of the focus of attention during the task. We also found that the inter-hemispheric beta coherence plays an important role in the differentiation of the two conditions, and that beta in the right frontal cortex is able to differentiate the conditions, demonstrating a greater involvement of procedural memory in fixed condition. Our results suggest a neuronal specialization in the execution of prosacadic paradigm involving motor task sequence.

O movimento sacádico é uma importante medida de comportamento usada para investigar vários processos cognitivos, incluindo atenção e integração sensório-motora. O presente estudo teve como objetivo investigar as mudanças na coerência em beta nos córtices frontal, motor, parietal e occipital durante a realização de duas condições diferentes de um paradigma do movimento sacádico. As condições envolveram um padrão diferente de apresentação do estímulo: a apresentação do estímulo fixo e do aleatório. Doze voluntários saudáveis ​​(três do sexo masculino, com idade média de 26,25; DP=4,13) realizaram a tarefa, enquanto o seu padrão de atividade cerebral era monitorado, usando eletroencefalografia quantitativa. Os resultados mostraram uma interação entre condição dos fatores e momento para o par de eletrodos C3/C4. Observou-se um efeito principal ao momento para CZ/C4, FZ/F3 e P3/PZ. Encontrou-se também um efeito principal à condição para FZ/F4, P3/P4 e O1/O2. Os resultados demonstram um importante papel da ligação interconexão entre os dois hemisférios, em busca visual e preparação do movimento. O estudo demonstra uma automatização da ação e uma redução do foco de atenção durante a tarefa. Identificou-se também que a coerência em beta entre regiões inter-hemisféricas desempenha um papel importante na diferenciação entre as duas condições. Ainda, beta no córtex frontal direito é capaz de diferenciar as condições, demonstrando-se um maior envolvimento da memória de procedimento em condição fixa. Sendo assim, os presentes resultados sugerem especialização neuronal na execução do paradigma prossacádico envolvendo sequência de tarefa motora.

Visuospatial attention deficit in patients with frontoparietal network lesions: Evidence from the attention network test / 中华物理医学与康复杂志

Objective To probe deficits in visuospatial attention using an attention network test (ANT) in patients with frontoparietal network lesions. Methods The ANT was used to measure the alertness, orienting and executive control abilities of 25 patients with local brain lesions, including 13 with frontal and 12 with parietal damage. Their results were compared with those of health adults. Results During ANT tasks, the patients' responses were significantly slower on each cue and target condition than controls', and showed deficits in their alerting and orienting networks. The efficiency of executive control was impaired in patients with frontal lesions, but increased with parietal lesions. Conclusions These findings suggest that the frontoparietal network is involved in alerting and orienting, but the executive control function may be selectively associated with the frontal lobe. ANT is an efficienttool for studying visual attention and cognition.

Lateral asymmetry of voluntary attention orienting

We recently demonstrated that automatic attention favors the right side of space and, in the present study, we investigated whether voluntary attention also favors this side. Six reaction time experiments were conducted. In each experiment, 12 new 18-25-year-old male right-handed individuals were tested. In Experiments 1, 2, 3 (a, b) and 4 (a, b), tasks with increasing attentional demands were used. In Experiments 1, 2, 3a, and 4a, attention was oriented to one or both sides by means of a central spatially informative visual cue. A left or right side visual target appeared 100, 300, or 500 ms later. Attentional effects were observed in the four experiments. In Experiments 2, 3a and 4a, these effects were greater when the cue indicated the right side than when it indicated the left side (respectively: 16 ± 10 and 44 ± 6 ms, P = 0.015, for stimulus onset asynchrony of 500 ms in Experiment 2; 38 ± 10 and 70 ± 7 ms, P = 0.011, for Experiment 3a, and 23 ± 11 and 61 ± 10 ms, P = 0.009, for Experiment 4a). In Experiments 3b and 4b, the central cue pointed to both sides and was said to be non-relevant for task performance. In these experiments right and left reaction times did not differ. The most conservative interpretation of the present findings is that voluntary attention orienting favors the right side of space, particularly when a difficult task has to be performed.

Central Neural Networks of Verbal Working Memory and Visuospatial Attention: An Interference Approach Using Low-frequency Repetitive Transcranial Magnetic Stimulation

OBJECTIVE: We evaluated a role of prefrontal and parietal cortex in verbal working memory and visuospatial attention using repetitive transcranial magnetic stimulation (rTMS). METHOD: In six healthy volunteers, bilateral prefrontal and parietal cortex was stimulated with rTMS (90% of motor threshold, 10 trains of 1 Hz rTMS) during performed cognitive tasks (two-back verbal working memory task and endogenous visuospatial attention task). rTMS was applied to 4 different sites over left prefrontal, right prefrontal, left parietal and right parietal areas at F3, F4, P3 and P4 location on the scalp, according to the 10/20 EEG system. The sham stimulation was applied with the coil placed perpendicular to the scalp. RESULTS: Reaction time (RT) was significantly prolonged by left prefrontal TMS in verbal working memory. In addition, performance deterioration was also observed during rTMS over the right prefrontal and left parietal areas. In visuospatial attention task, RT was significantly prolonged by right parietal TMS. CONCLUSION: These results show that left prefrontal cortex play a major role in the network of working memory, and right parietal cortex is important area in the visuospatial attention. We suggest that an rTMS could be a useful method for evaluation of neural network in human brain.

Neural Network for Visuospatial Attention in Patients with Traumatic Brain Injury

PURPOSE: To investigate the brain areas related with the deficit in visuospatial attention in patients with traumatic brain injury (TBI) using functional MRI (fMRI). METHOD: Twenty TBI and fifteen normal subjects were enrolled. The endogenous visuospatial attention task was used as an activation paradigm during fMRI. FMRI was performed on a 3T ISOL Forte scanner. Thirty slices were acquired using a single-shot EPI sequences (TR/TE=3000/ 30 ms, Flip angle 70 degrees, FOV=220 mm, 64x64 matrix, slice thickness 4 mm). The accuracy and reaction time to the attention task were measured during fMRI. Imaging data were analyzed using SPM-99 software. RESULTS: The ratio of accurate responses was lower (p<0.01) and the average reaction time was slower (p<0.01) in the TBI group than the normal group. The fMRI analysis showed more activation in the bilateral prefrontal cortices (the middle and inferior frontal gyri) and less activation in the cingulate gyrus, medial frontal lobe, bilateral temporo- occipital areas, and cerebellum in the TBI group compared with the normal group. CONCLUSION: In TBI patients, impaired visuospatial attention might be resulted from the decreased activity of the cingulate, medial frontal, and temporo-occipital regions accompanied with compensatory hyperactivation of the prefrontal cortex.

Effects of Methylphenidate on Cognitive Impairment Following Brain Injury: A double-blind placebo-controlled study

OBJECTIVE: To evaluate the effect of methylphenidate on cognitive function especially on working memory and visuospatial attention in the patients with traumatic brain injury (TBI). METHOD: Eighteen subjects, 16 males and 2 females, with TBI were enrolled. Their mean age was 34.2 years old. A double-blind placebo-controlled study was designed. The baseline cognitive assessment was performed before the administration of drug. Two days after the baseline study, 20 mg of methylphenidate or placebo was administered. The second cognitive assessment was performed 2 hours after the treatment. The follow-up assessment conducted two days after the second test. Cognitive assessments consisted of 'one-back working memory task' and 'endogenous visuospatial attention task', designed using SuperLab Pro 2.0 software. RESULTS: In one-back working memory test, there was significant improvement of response accuracy in methylphenidate group in comparison with placebo group (p<0.01). Significant shortening of reaction time was also seen after the administration of drug in methylphenidate group (p<0.05). In endogenous visuospatial attention test, significant improvement of response accuracy was noticed after the administration of drug in methylphenidate group (p<0.05). CONCLUSION: These results demonstrated that the administration of methylphenidate was beneficial in improving cognitive function following TBI. The effect was prominent in the accuracy of working memory.