Coding of the Reach Vector in Parietal Area 5d

Competing models of sensorimotor computation predict different topological constraints in the brain. Some models propose population coding of particular reference frames in anatomically distinct nodes, whereas others require no such dedicated subpopulations and instead predict that regions will simultaneously code in multiple, intermediate, reference frames. Current empirical evidence is conflicting, partly due to difficulties involved in identifying underlying reference frames. Here, we independently varied the locations of hand, gaze, and target over many positions while recording from the dorsal aspect of parietal area 5. We find that the target is represented in a predominantly hand-centered reference frame here, contrasting with the relative code seen in dorsal premotor cortex and the mostly gaze-centered reference frame in the parietal reach region. This supports the hypothesis that different nodes of the sensorimotor circuit contain distinct and systematic representations, and this constrains the types of computational model that are neurobiologically relevant

Temporal Analysis of Reference Frames in Parietal Cortex Area 5d during Reach Planning

The neural encoding of spatial and postural reference frames in posterior parietal cortex has traditionally been studied during fixed epochs, but the temporal evolution of these representations (or lack thereof) can provide insight into the underlying computations and functions of this region. Here we present single-unit data recorded from two rhesus macaques during a reach planning task. We found that area 5d coded the position of the hand relative to gaze before presentation of the reach target, but switched to coding the target location relative to hand position soon after target presentation. In the pretarget period the most relevant information for success in the task is the position of the hand relative to gaze; however, after target onset, the most task-relevant spatial relationship is the location of the target relative to the hand. The switch in coding suggests that population activity in area 5d may represent postural and spatial information in the reference frame that is most pertinent at each stage of the task. Moreover, although target−hand coding was dominant from soon after the reach target onset, this representation was not static but built in strength as movement onset approached, which we speculate could reflect a role for this region in building an accurate state estimate for the limb. We conclude that representations in area 5d are more flexible and dynamic than previously reported

Dorsal Raphe Dopamine Neurons Modulate Arousal and Promote Wakefulness by Salient Stimuli

Ventral midbrain dopamine (DA) is unambiguously involved in motivation and behavioral arousal, yet the contributions of other DA populations to these processes are poorly understood. Here, we demonstrate that the dorsal raphe nucleus DA neurons are critical modulators of behavioral arousal and sleep-wake patterning. Using simultaneous fiber photometry and polysomnography, we observed time-delineated dorsal raphe nucleus dopaminergic (DRNDA) activity upon exposure to arousal-evoking salient cues, irrespective of their hedonic valence. We also observed broader fluctuations of DRNDA activity across sleep-wake cycles with highest activity during wakefulness. Both endogenous DRNDA activity and optogenetically driven DRNDA activity were associated with waking from sleep, with DA signal strength predictive of wake duration. Conversely, chemogenetic inhibition opposed wakefulness and promoted NREM sleep, even in the face of salient stimuli. Therefore, the DRNDA population is a critical contributor to wake-promoting pathways and is capable of modulating sleep-wake states according to the outside environment, wherein the perception of salient stimuli prompts vigilance and arousal

Demographics of extra-articular calcaneal fractures: Including a review of the literature on treatment and outcome

Introduction: Extra-articular calcaneal fractures represent 25-40% of all calcaneal fractures and an even higher percentage of up to 60% is seen in children. A disproportionately small part of the literature on calcaneal fractures involves the extra-articular type. The aim of this study was to investigate the incidence of extra-articular calcaneal fractures in a Level 1 trauma centre, define the distribution of the various types of fractures and compare patient demographics between extra- and intra-articular calcaneal fractures. In addition the literature was reviewed for the most common types of extra-articular calcaneal fractures with regard to incidence, treatment and clinical outcome. Methods: The radiological records between 2003 and 2005 were reviewed for intra- and extra-articular calcaneal fractures. Patient gender-distribution and age were compared. A literature search was conducted for the treatment of extra-articular calcaneal fractures. Results: In this 3-year study period a total of 49 patients with 50 extra-articular calcaneal fractures and 91 patients with 101 intra-articular fractures were identified. The median age for the first group was 32.7 years, and for the second group 40.3 years; P = 0.04. Male predominance was significantly less pronounced for extra-articular (63%) compared with intra-articular fractures (79%; P = 0.04). Conclusion: One-third of all calcaneal fractures are extra-articular. Significant differences exist between the intra- and extra-articular groups, in terms of lower age and male-female ratio. The literature study shows inconsistencies in treatment options, but most extra-articular fractures are well manageable conservatively

Community-based dietary and physical activity interventions in low socioeconomic groups in the UK: a mixed methods systematic review

Objective: Low socioeconomic status (SES) is a risk factor for type 2 diabetes and changes in diet and physical activity can prevent diabetes. We assessed the effectiveness and acceptability of community-based dietary and physical activity interventions among low-SES groups in the UK. Method: We searched relevant databases and web resources from 1990 to November 2009 to identify relevant published and grey literature using an iterative approach, focusing on UK studies. Results: Thirty-five relevant papers (nine quantitative, 23 qualitative and three mixed methods studies) were data extracted, quality assessed and synthesised using narrative synthesis and thematic analysis. The relationship between interventions and barriers and facilitators was also examined. Dietary/nutritional, food retail, physical activity and multi-component interventions demonstrated mixed effectiveness. Qualitative studies indicated a range of barriers and facilitators, which spanned pragmatic, social and psychological issues. The more effective interventions used a range of techniques to address some surface-level psychological and pragmatic concerns, however many deeper-level social, psychological and pragmatic concerns were not addressed. Conclusion: Evidence on the effectiveness of community-based dietary and physical activity interventions is inconclusive. A range of barriers and facilitators exist, some of which were addressed by interventions but some of which require consideration in future research