Modulation of Spike Count Correlations Between Macaque Primary Visual Cortex Neurons by Difficulty of Attentional Task / 神经科学通报·英文版

Studies have shown that spatial attention remarkably affects the trial-to-trial response variability shared between neurons. Difficulty in the attentional task adjusts how much concentration we maintain on what is currently important and what is filtered as irrelevant sensory information. However, how task difficulty mediates the interactions between neurons with separated receptive fields (RFs) that are attended to or attended away is still not clear. We examined spike count correlations between single-unit activities recorded simultaneously in the primary visual cortex (V1) while monkeys performed a spatial attention task with two levels of difficulty. Moreover, the RFs of the two neurons recorded were non-overlapping to allow us to study fluctuations in the correlated responses between competing visual inputs when the focus of attention was allocated to the RF of one neuron. While increasing difficulty in the spatial attention task, spike count correlations were either decreased to become negative between neuronal pairs, implying competition among them, with one neuron (or none) exhibiting attentional enhancement of firing rate, or increased to become positive, suggesting inter-neuronal cooperation, with one of the pair showing attentional suppression of spiking responses. Besides, the modulation of spike count correlations by task difficulty was independent of the attended locations. These findings provide evidence that task difficulty affects the functional interactions between different neuronal pools in V1 when selective attention resolves the spatial competition.

Analysis of spatial attention processing characteristics in patients with unilateral spatial neglect after stroke / 中国脑血管病杂志

Objective To study spatial attention processing characteristics in patients with unilateral spatial neglect (USN)by comparing the patients with right USN and behavioral findings of event-related potential (ERP)in normal subjects and the amplitude and latency of P1,N1 and P300. Methods Ten consecutive patients with USN (USN group)after right-hemisphere stroke admitted to the Department of Rehabilitation Medicine,Xuanwu Hospital,Capital Medical University from April 2012 to April 2013 were enrolled retrospectively. Age-and sex-matched 10 normal subjects with the USN group were selected. ERP was used to document the electroencephalogram changes of two groups of subjects when performing visual Oddball pattern tasks. The response time and accuracy of target stimuli in both groups appearing on the left (left target)and right (right target)were analyzed and compared. The amplitude and latency of all ERP components (P1,N1,P300)on the left and right target stimuli were analyzed by repeated measurement of multivariate analysis of variance. The pathogenesis of USN after stroke was investigated. Results In the USN group,the accuracy of target stimuli on left side and right side was lower than that in the normal group (left target:17. 7 ± 7. 5% vs. 98. 5 ± 7. 5%,P＜0. 01;right target:88. 5 ± 2. 0% vs. 99. 0 ± 2. 0 %,P＝0. 002). There was no significant difference in P1 amplitude between the two groups (F ＝1. 104,P ＝0. 307). When the target stimulus appeared on the left side,the N1 amplitude on the right hemisphere of the USN group was lower than that of the normal group (-0. 3 ± 1. 1 μV vs. -5. 8 ± 1. 1 μV;P＝0. 001), when the target stimulus appeared on the right side,the N1 amplitude of USN group was lower than that of the normal group (-1. 8 ± 1. 0 μV vs. -6. 0 ± 1. 0 μV;F＝9. 799,P＝0. 006). The P300 amplitude of left target of the USN group was lower than that of the normal group (1. 0 ± 1. 1 μV vs. 7. 2 ± 1. 1 μV;P＝0. 001). Compared with the normal group,the latency of each wave of P1 (right hemisphere)(136. 7 ± 3. 8 ms vs. 122. 1 ± 3. 8 ms;P ＝0. 013),N1 (179. 7 ± 2. 0 ms vs. 172. 8 ± 2. 0 ms;F ＝5. 775,P ＝0. 027),and P300 (490 ± 12 ms vs. 402 ± 12 ms;F＝27. 310,P＜0. 01]in the USN group was prolonged. Conclusion During the spatial attention processing in patients with USN,regardless of the stimuli from the left and right,its information processing had been damaged to a certain degree.

Dysfunction of visual spatial attention in occipital stroke patients with hemianopia during the acute phase / 中华神经科杂志

Objective To investigate the visual spatial attention of occipital stroke patients with hemianopia during the acute phase.Methods Eight occipital stroke patients with homonymous hemianopia of left side in the acute stage and 10 age-matched healthy controls were recruited to examine the capability of visual spatial attention.The cue-target paradigms were applied in this behavioral research.Results In the repeated measures analysis of variance,the difference of group and cue range had distinct main effect in reaction time and accuracy rate,while the difference of target location only had main effect in reaction time.Compared with the control group,the patients exhibited longer reaction time ((1 628.26 ± 183.97) ms vs (839.79±61.29) ms,F(1,16) =163.706,P＜0.05) and lower accuracy rate (73.40％ ±3.12％ vs 92.99％ ±0.76％,F(1,16) =371.850,P ＜ 0.05).The patients displayed lower accuracy rate under large cue than small cue (71.38％ ±3.35％ vs 75.42％ ±4.23％,F(1,7) =6.706,P ＜0.05),while that of healthy controls did not vary under different cue range(93.01％ ± 0.50％ vs 92.96％ ± 1.42％,F(1,9) =0.010,P ＞ 0.05).The patients showed longer reaction time in blind-side target than healthy-side target ((1 664.17±196.57) msvs (1 594.35±174.45) ms,F(1,7) =14.157,P＜0.05),while that of control group in two target location had no statistically significant difference ((839.67 ± 60.41) ms vs (839.91 ±73.54) ms,F(1,9) =0.000,P ＞0.05).Furthermore,the mean reaction time of stroke patients had a negative correlation with the binocular vision field index (r =-0.824,P ＜ 0.05).Conclusions The extent of vision field loss in occipital stroke patients with hemianopia can reflect impairment of visual spatial attention during the acute phase.The rehabilitation training should emphasize promoting recovery of visual spatial attention in the blind side under large cue.

Monitoramento do tempo de reação como estratégia de avaliação cognitiva e acompanhamento psicológico de judocas / Reaction time monitoring as a cognitive assessment strategy and psychological accompaniment of judokas

Medidas do tempo de reação manual têm sido extensivamente empregadas pela neurociência cognitiva para o estudo de funções psicomotoras em diferentes circunstâncias, incluindo modelos aplicados ao contexto do esporte de alto rendimento. O presente estudo teve a finalidade de investigar possíveis aplicações de um teste de reação manual específico - protocolo de Simon - como estratégia de avaliação cognitiva e acompanhamento de atletas na área da psicologia do esporte. Para isso, dois atletas de judô foram testados semanalmente, durante o período de um mês, com o teste de Simon. As análises demonstraram que é possível identificar variações no desempenho individual entre as diferentes sessões realizadas. O atleta 1 apresentou diferenças significativas entre as sessões de avaliação, reduzindo progressivamente seu tempo de reação ao longo das três primeiras sessões,mas lentificando novamente suas respostas na última sessão de avaliação. Por sua vez, o atleta 2, apresentou um perfil diferente, oscilando mais seu desempenho ao longo do acompanhamento mensal (lentificou suas respostas da primeira para a terceira sessão e reduziu seus tempos de resposta na quarta avaliação). Esses resultados trazem evidências a favor da utilização do teste de Simon como mais uma estratégia de avaliação cognitiva no esporte, apresentando sensibilidade às variações individuais de desempenho e também obedecendo ao princípio da individualidade biológica, permitindo a distinção dos padrões de resposta entre os indivíduos. Os resultados obtidos fortalecem o potencial das medidas psicofísicas ao revelarem uma forma alternativa de avaliação em comparação aos tradicionais métodos explícitos da psicologia do esporte, além de propiciarem uma abordagem informatizada para avaliação situacional de capacidades de integração sensório-motora, tomada de decisão e atenção espacial.

Manual reaction measures have been extensively employed by cognitive neuroscience to psychomotor studies in different circumstances, including applied methods to the high performance sportive context. The present study aimed to studypossible applications of a specific reaction time procedure (Simon task) as a cognitive assessment strategy and accompaniment in the sport psychology area. In this study, two judo athletes were weekly evaluated with the Simon task during a period of one month. Analyses have shown that is possible to identify variations in individual performance between the different practiced sessions. The Athlete 1 showed significant differences between the assessment sessions, progressively reducing your reaction time over the first three sessions, but slowing the responses at the last session. The athlete 2, showed a different profile, varying his performance over the monthly monitoring (slowed your responses from the first to the third session and reduced the reaction time on fourth assessment). These results provide evidences in favour for the use of the Simon test as more one cognitive assessment strategy in sport, showing sensitivity to individual performance variations and also obeying the principle of biological individuality, allowing the distinction of response patterns between the individuals. The results strengthen the potential use of psychophysics measures revealing an alternative way for assessment compared totraditional explicit methods of sport psychology, providing a computerized approach for situational assessment of sensorimotor integration, decision making and spatial attention abilities

Non-invasive induction and cancellation of visuo-spatial deficits by repetitive Transcranial Magnetic Stimulation (rTMS): Lessons on “surgery-less” manipulation of complex visuo-spatial brain networks

Repetitive Magnetic Stimulation (rTMS) has shown to modify the excitability of targeted cortical regions in animals and humans, thus transiently altering the efficiency of neural projections within extended brain networks. Adequate processing and behavioral output depend on a given ‘state’ of functional interactions between cortical and subcortical nodes within this network. We applied rTMS trains targeted at the visuoparietal (VP) cortex, which is a crucial cortical node of an extended visuo-spatial neural network, in both, intact (n=2) and injured cats (n=2) with unilateral ablation of the VP region. All four intact cats were intensively trained in a set of visuo-spatial tasks consisting in the detection and localization of moving or static targets. In two of these cats, a 50 mm circular coil was centered on the left VP cortex and Sham or real rTMS was delivered during 20 minutes at 1 Hz. Real but not Sham rTMS significantly increased the number of errors in orienting responses towards static but not moving targets, presented at the contralateral visual hemifield (38±4%; and 48±3% p<0.05 vs. pre rTMS), whereas no increase respect to baseline was observed for ipsilateral targets (5±2%; 2±1%; n.s). Performance went back to baseline error levels 45 minutes after the end of the stimulation (4±2; 6±1%). In 2 other animals, the right or left parietal and primary visual cortex was surgically removed, generating a Daily stimulation with 1 Hz rTMS on the intact VP region resulted in a progressive reduction of detection¬orienting mistakes to moving but not static stimuli (down to 34±5% and 28±4% errors; p<0.05). We conclude that rTMS is able to interact with brain networks in both ways, transiently disrupting visuo-spatial processing in normal animals, and also canceling spatial neglect generated by lesions of the same areas. It constitutes, thus, a non-invasive ‘surgery-less’ method to manipulate brain activity and promote recovery after injuries.