Gene frequencies of ABO and Rh blood groups in Nigeria: A review

Background : ABO and Rhesus factor (Rh) blood type are germane in human life in genetics and clinical studies. Aim of the study : The review was undertaken with the objective to provide data on the ABO and Rh(D) blood group distribution and gene frequency across Nigeria which is vital for blood transfusion and susceptibility to disease. Materials and methods: Literature search for ABO/Rh blood distribution in Nigeria was done and allele frequencies of A, B, O, D and d were calculated from the frequency recorded from six geopolitical zones in Nigeria. We reported frequency of ABO and Rhesus blood type from 318,940 and 280,514 individuals respectively. Prevalence were reported as percentage and Hardy-Weinberg equilibrium was tested using Chi square test and p was set at 0.05 unless otherwise stated. Results : We reported ABO blood group frequencies in the order O > A > B > AB (52.93%, 22.77%, 20.64% and 3.66%) while prevalence of Rh+ was 94.90% from total population studied. Our reported frequencies did not differ from Hardy-Weinberg equilibrium (goodness-of-fit X 2 for ABO = 1.74 df = 3, p < 0.05). Allelic frequencies for A(p), B(q) and O(r) are 0.143, 0.130 and 0.728 respectively. Conclusion : The study provides information on the distribution/frequency of ABO/Rh(D) blood group and their corresponding allelic proportion in a large Nigeria study. It also revealed how the Nigerian populations in the North, South, West and East vary with respect to genetic traits. This vital information will be important for population genetics and anthropology studies and may be helpful in planning for future health strategy and blueprint, particularly planning with regards to disease management and blood transfusion medicine

Plasticity and cerebral reorganization: an update

International audienc

Système cérébraux de l'attention spatiale (une approche combinée en neuroimagerie et en neuropsycholgie)

Nous avons étudié les réseaux de l'attention spatiale du cerveau humain dans le cadre de la négligence spatiale, un syndrome neurologique qui est le plus souvent la conséquence dune lésion de l 'hémisphère droit. Les patients négligents montrent une attraction magntique vers les stimuli qui apparaissent du côté ipsilésionel, tout en ignorant le côté contralésionel. La nature attentionelle de la négligence a été postulée dans différents modèles et démontrée expérimentalement. Pourtant, le rôle de l'attention dans certains signes cliniques de la négligence est débattu. La première étude de cette thèse a investigué la nature attentionnelle de la déviation vers la droite en bissection de ligne, avec un paradigme expérimental basé sur l'effet de répulsion attentionnelle chez des sujets normaux. Les résultats confirment l'implication de l'attention dans cette tâche. En adoptant la perspective d'une organisation de l'attention spatiale en réseaux, une deuxième étude a été menée chez les patients cérébrolés droits. Cette étude a combiné une approche comportementale basée sur une analyse factorielle, avec une cartographie de lésions et une tractographie de faisceaux de matière blanche, reconstruits à partir de séquences en IRM de diffusion. Les résultats confirment l'implication d'un réseau fronto-pariétal dans les deux composantes (visuo-perceptive et visuo-motrice) de la négligence spatiale. Une implication bilatérale des réseaux fronto-pariétaux dans l'attention est suggérée dans la troisème étude basée sur la tractographie de données obtenues en tenseur de diffusion chez un patient présentant une négligence droite, la suite de lésions de l'hémisphère gauche.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Attention biases the perceived midpoint of horizontal lines

In patients with right brain damage and left visual neglect, attention tends to be captured by right-sided objects and cannot easily disengage from them. While these phenomena can account for several clinical and experimental patterns of performance such as biased visual search, its role is more controversial for other neglect-related signs, such as the typical rightward shifts in horizontal line bisection. It is thus important to see whether and how attentional orienting can bias line bisection in normal participants using standard clinical bisection stimuli. In 3 experiments, we explored the Attentional Repulsion Effect (ARE, Suzuki & Cavanagh, 1997) on pre-bisected lines. Normal observers saw horizontal lines with a vertical bisection mark near the center, preceded by a cue to the left or right of the line, or by no cue. On each trial, observers indicated whether they saw the bisection mark to the left or at the right of the midpoint. We plotted the proportion of 'seen-at-right' responses as a function of the mark's actual position. For uncued lines, the point of subjective equality was slightly at the left of the true center, consistent with the pseudoneglect phenomenon. Right-sided cues shifted the apparent bisection point to the left (and vice versa), as predicted by the ARE. Similar results occurred with different task instructions (compare the length of the left-sided line segment to the right-sided segment) and in the presence or absence of central fixation marks. These results obtained in normal participants support attentional accounts of biased line bisection in neglect patients

Prismatic adaptation therapy in visual neglect: the importance of connectional anatomy

International audienceThe meta-analysis conducted by Székely et al. described the lack of beneficial effect of prism adaptation in neglect patients. The authors concluded that the results did “not support the routine use of prism adaptation as a therapy for spatial neglect”. However, a possible nuance to this conclusion could be that the response (or lack thereof) of neglect patients to prism adaptation may actually depend on the connectional anatomy of their lesion. We develop this idea in our commentary, in order to offer a more balanced perspective on the implications of the findings obtained by Székely et al

Visual neglect: Is there a relationship between impaired spatial working memory and re-cancellation?

In visual search tasks, neglect patients tend to explore and repeatedly re-cancel stimuli on the ipsilesional side, as if they did not realize that they had previously examined the rightward locations favoured by their lateral bias. The aim of this study was to explore the hypothesis that a spatial working memory deficit explains these ipsilesional re-cancellation errors in neglect patients. For the first time, we evaluated spatial working memory and re-cancellation through separate and independent tasks in a group of patients with right hemisphere damage and a diagnosis of left neglect. Results showed impaired spatial working memory in neglect patients. Compared to the control group, neglect patients cancelled fewer targets and made more re-cancellations both on the left side and on the right side. The spatial working memory deficit appears to be related to re-cancellations, but only for some neglect patients. Alternative interpretations of re-exploration of space are discussed

Facilitation paradoxale induite par la perturbation de la fonction visuo-spatiale: revisiter «l’effet Sprague»

International audienceThe ‘Sprague Effect’ described in the seminal paper of James Sprague (Science 153:1544 e1547, 1966a) is an unexpected paradoxical effect in which a second brain lesion reversed functional deficits induced by an earlier lesion. It was observed initially in the cat where severe and permanent contralateral visually guided attentional deficits generated by the ablation of large areas of the visual cortex were reversed by the subsequent removal of the superior colliculus (SC) opposite to the cortical lesion or by the splitting of the collicular commissure. Physiologically, this effect has been explained in several ways-most notably by the reduction of the functional inhibition of the ipsilateral SC by the contralateral SC, and the restoration of normal interactions between cortical and midbrain structures after ablation. In the present review, we aim at reappraising the ‘Sprague Effect’ by critically analyzing studies that have been conducted in the feline and human brain. Moreover, we assess applications of the ‘Sprague Effect’ in the rehabilitation of visually guided atten- tional impairments by using non-invasive therapeutic approaches such as transcranial magnetic stimulation (TMS) and transcranial direct-current stimulation (tDCS). We also review theoretical models of the effect that emphasize the inhibition and balancing be- tween the two hemispheres and show implications for lesion inference approaches. Last, we critically review whether the resulting inter-hemispheric rivalry theories lead toward an efficient rehabilitation of stroke in humans. We conclude by emphasizing key challenges in the field of ‘Sprague Effect’ applications in order to design better therapies for brain-damaged patients.L’effet Sprague décrit dans le document fondateur de James Sprague (Science 153: 1544 e1547, 1966a) est un effet paradoxal inattendu dans lequel une deuxième lésion cérébrale inversait les déficits fonctionnels induits par une lésion antérieure. Il a été observé initialement chez le chat où les déficits attentionnels controlatéraux sévères et permanents générés par l'ablation de grandes zones du cortex visuel ont été inversés par l'ablation ultérieure du colliculus supérieur (SC) opposé à la lésion corticale ou par la division de la commissure colliculaire. Physiologiquement, cet effet a été expliqué de plusieurs façons, notamment par la réduction de l'inhibition fonctionnelle de la SC ipsilatérale par la SC controlatérale et la restauration des interactions normales entre les structures corticales et du mésencéphale après l'ablation. Dans la présente revue, nous visons à réévaluer «l’effet Sprague» en analysant de manière critique les études qui ont été menées sur le cerveau félin et humain. De plus, nous évaluons les applications de «l’effet Sprague» dans la réadaptation des troubles de l’attention guidés visuellement en utilisant des approches thérapeutiques non invasives telles que la stimulation magnétique transcrânienne (TMS) et la stimulation transcrânienne à courant continu (tDCS). Nous passons également en revue les modèles théoriques de l'effet qui mettent l'accent sur l'inhibition et l'équilibre entre les deux hémisphères et montrent les implications pour les approches d'inférence des lésions. Enfin, nous examinons de manière critique si les théories de rivalité interhémisphérique qui en résultent conduisent à une réhabilitation efficace de l'AVC chez l'homme. Nous concluons en mettant l’accent sur les principaux défis dans le domaine des applications de «l’effet Sprague» afin de concevoir de meilleures thérapies pour les patients atteints de lésions cérébrales

Is there a relationship between perseverations and spatial short-term memory deficits in unilateral neglect?

peer reviewedIntroduction Spatial neglect is a multicomponent syndrome characterized by an inability to orient or to respond to stimuli arising in the hemispace contralateral to a brain lesion. According to many authors, spatial neglect can be explained by an attentional deficit, and more specifically by a lateral attentional bias towards the right (magnetic attraction) and/or difficulties in disengaging attention from items to the right side. However, attentional theories are not sufficient to explain some behaviors such as revisiting and perseverations. Recently, it has been suggested that revisiting and perseveration behaviors in visual search tasks shown in parietal neglect could be related to impairments in visuo-spatial working memory (Husain et al., 2001; Malhotra et al., 2005; Malhotra, Mannan, Driver, & Husain, 2004). This hypothesis is supported by studies (1) in which a contrast is made between cancellation tasks with and without visual control, the absence of visual feedback increasing left neglect (omissions) and repeated cancellations (perseverations) towards the ipsilesional space, and (2) in which the Corsi test is administrated in a vertical way. However, Ronchi et al. (2009) did not confirm the link between impairments in spatial short-term memory and perseverations. Indeed, these authors found no correlation between perseverations in star cancellation and spatial memory performance in the Corsi test. Nevertheless, they did not use a condition without visual feedback, which is considered as involving more spatial short-term memory than a condition with visual feedback. This methodological choice could explain the lack of relationship between short-term memory and perseverations in the Ronchi et al.’s study. The purpose of our study was to test the hypothesis of a spatial short-term memory deficit being an explanatory factor of perseverations in unilateral neglect. Methods We assessed twenty right-damaged patients suffering from left neglect. Neglect signs were evaluated with the Batterie d’Evaluation de la Négligence (BEN) (Azouvi et al., 2002). Twenty healthy older participants matched for age and sociocultural level served as controls. In order to explore the relationship between perseverations and spatial short-term memory, two different tasks were administrated: a computerized version of the Corsi test and a cancellation task. All tests were computerized and presented on a touchscreen. The subject’s spatial span corresponded to the longest sequence in which at least three out of four sequences were correctly reproduced. The cancellation task consisted of 32 “O” presented in two conditions: with (visible) and without (invisible) visual feedback. Patients were instructed to cancel out all targets only once. The number of omissions and perseverations was calculated for each participant in both conditions. Results Control participants performed better than neglect patients in the Corsi test; eleven neglect patients showed a deficit in spatial short-term memory. In the cancellation tasks, Wilcoxon matched-pairs signed ranks tests highlighted that perseverations and omissions were greater in the invisible condition for each group. In this condition, neglect patients made more omissions and perseverations (all ps <.05) than control subjects, while in the visible condition there was only a significant difference for the omissions. However, spatial short-term memory did not explain perseverations in invisible condition (R² = .17, F(1,18) = 3.66, p = .07). Discussion These findings suggest that a spatial short-term memory deficit cannot be considered as an explanatory factor for the perseveration behavior in unilateral neglect. Moreover, perseverations and omissions were greater in the invisible condition than in the visible one; therefore, the hypothesis of the magnetic attraction is not confirmed either. In the neglect patients’ group, the visual feedback decreases, and even eliminates the neglect symptoms (omissions and perseverations) compared to the invisible condition. In other words, the presence of visual feedback can help patients to explore their visual environment. We propose that, in the invisible condition, difficulties to plan a visual search could exacerbate both omissions and perseverations, leading to recursive search towards the right side of the space and thus promote failure to explore left space. However, further investigations will be necessary to confirm this hypothesis