Weekend bioRxiv Preprint Review: A robust role for motor cortex

Humans, and probably primates in general, use their primary motor cortex (Brodmann area 4) when executing voluntary, specifically directed motor activity, such as reaching for an object. In the human brain, Brodmann area 4 is organized spatially in the brain by the area of the body activated, as a distorted spatial map of the body (a homonculous).

It has been less clear whether non-primate animals such as the rodents use this part of their brain in a similar way. We know that fish such as the zebrafish, which lack a neocortex, probably use their pallium, which in humans is part of the basal ganglia region which modulates but does not determine voluntary motion, for such directed movements. Exactly how in the zebrafish such a basal ganglia analogue activation leads to motion does not seem to be fully understood.

The preprint below theorizes that in mammals such as rats, there is a third option between the primate's use of primary motor cortex and the absence of use in the fish: the rat may use its non-primary motor cortex regions and basal ganglia modulations for familiar, well-learned tasks, and then may activate its primary motor cortex for tasks that are unlearned, when it must move differently in the presence of novelty.

ABSTRACT

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A robust role for motor cortex

Authors: Goncalo Lopes, Joana Nogueira, Joseph J. Paton, Adam R. Kampff

doi: http://dx.doi.org/10.1101/058917

Abstract

The role of motor cortex in the direct control of movement remains unclear, particularly in non-primate mammals. More than a century of research using stimulation, anatomical and electrophysiological studies has implicated neural activity in this region with all kinds of movement. However, following the removal of motor cortex, or even the entire cortex, rats retain the ability to execute a surprisingly large range of adaptive behaviours, including previously learned skilled movements. In this work we revisit these two conflicting views of motor cortical control by asking what the primordial role of motor cortex is in non-primate mammals, and how it can be effectively assayed. In order to motivate the discussion we present a new assay of behaviour in the rat, challenging animals to produce robust responses to unexpected and unpredictable situations while navigating a dynamic obstacle course. Surprisingly, we found that rats with motor cortical lesions show clear impairments in dealing with an unexpected collapse of the obstacles, while showing virtually no impairment with repeated trials in many other motor and cognitive metrics of performance. We propose a new role for motor cortex: extending the robustness of sub-cortical movement systems, specifically to unexpected situations demanding rapid motor responses adapted to environmental context. The implications of this idea for current and future research are discussed.

Milk and Cheese Consumption Associated with Slightly Lower Risk of Stroke

Since milk, an animal product, contains saturated fats and cholesterol, which are often said to increase MI and stroke risks, it has sometimes been asserted that increasing consumption of dairy foods such as milk and cheese would increase stroke risk. Indeed, the Mediterranean diet has been cited as a good diet partly because it limits not just red meat but decreases dairy food consumption compared to diets associated with a higher vascular disease risk.

However, a new meta-analytic study, just published in the Journal of the American Heart Association, shows a small but consistent decrease in stroke risk with increasing consumption of milk and cheese foods, in both Western and Asian populations.

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ABSTRACT

J Am Heart Assoc. 2016; 5: e002787

originally published May 20, 2016

doi: 10.1161/JAHA.115.002787

Dairy Consumption and Risk of Stroke: A Systematic Review and Updated Dose–Response Meta‐Analysis of Prospective Cohort Studies

Janette de Goede, PhD; Sabita S. Soedamah‐Muthu, PhD; An Pan, PhD; Lieke Gijsbers, MSc; Johanna M. Geleijnse, PhD

Abstract

Background A higher milk consumption may be associated with a lower stroke risk. We conducted a comprehensive systematic review and dose–response meta‐analysis of milk and other dairy products in relation to stroke risk.

Methods and Results Through a systematic literature search, prospective cohort studies of dairy foods and incident stroke in stroke‐free adults were identified. Random‐effects meta‐analyses with summarized dose–response data were performed, taking into account sources of heterogeneity, and spline models were used to systematically investigate nonlinearity of the associations. We included 18 studies with 8 to 26 years of follow‐up that included 762 414 individuals and 29 943 stroke events. An increment of 200 g of daily milk intake was associated with a 7% lower risk of stroke (relative risk 0.93; 95% CI 0.88–0.98; P=0.004; I2=86%). Relative risks were 0.82 (95% CI 0.75–0.90) in East Asian and 0.98 (95% CI 0.95–1.01) in Western countries (median intakes 38 and 266 g/day, respectively) with less but still considerable heterogeneity within the continents. Cheese intake was marginally inversely associated with stroke risk (relative risk 0.97; 95% CI 0.94–1.01 per 40 g/day). Risk reductions were maximal around 125 g/day for milk and from 25 g/day onwards for cheese. Based on a limited number of studies, high‐fat milk was directly associated with stroke risk. No associations were found for yogurt, butter, or total dairy.

Conclusions Milk and cheese consumption were inversely associated with stroke risk. Results should be placed in the context of the observed heterogeneity. Future epidemiological studies should provide more details about dairy types, including fat content. In addition, the role of dairy in Asian populations deserves further attention.

DIfferential Coral Bleaching at Two-Step Dive Site: Warming Waters or Runoff?

We've always liked the coral at Two-Step snorkeling beach, the waters directly across from the City of Refuge in south Kona district. Sadly, this area was in the epicenter of the recent dengue outbreak (August 2015 - March 2016) here on the Big Island. Because of this, we avoided the place after August, just returning this past Memorial Day to dive. The weather was good, though the water was a bit cloudy from recent rains. We saw a large whitetip shark cruising below the wall, along with turtles and many fish, so the overall reef life seemed healthy. However, we saw no shrimp, and some (just finger type hard corals, it seemed) of the coral had bleached. I wonder why?

At Twostep, the small polyp finger corals (Porites) were bleached and in poor condition, completely changed from last August (2015) when we last were here. On the other hand, the plate corals (Porites rus) at the wall were healthy and seemed to be growing in the area of reef it occupied at the expense of the bleached finger coral. Closer to shore, the encrusting false brain corals were multicolored and mostly healthy, unchanged I think from last year.

So, what could be the causes of the bleaching we saw between October 2015 and May 2016 at Two-Step?

First of all, there was a significant bleaching event in corals worldwide this past October, attributed to a recent warming cycle or less likely to El Nino water temperature elevations. So perhaps the finger coral was less tolerant of the warming conditions.

Second, it's possible that the spraying of pesticide on the vegetation near the water, needed to eradicate the dengue-infected mosquitoes of this district, caused some insecticide leakage into the water. I do not know why that would only affect the finger coral, though.

A third possibility is some local infection of the coral, perhaps in conjuction with the other two environmental factors, caused the finger coral bleaching.

Will the finger coral return, or will the wall at 2-step become a wall of mostly plate corals? We will see if this becomes a succession event. Hopefully the other corals will not follow the bleaching example of the finger corals later this year.