Thursday, April 09, 2015

Five papers that seem to all go together

Lately I've seen or have been sent one paper after another that chase each other around in my head, so I'm going to put them all in here, for later digestion. 

1. A very interesting paper that supports the idea that the brain does its own thing, mostly, and uses up a large amount of energy to do so. There is a section in there pointing out how very little sensory information actually reaches the brain. I saw a video a long time ago that spelled this out for vision, but alas I couldn't find it again. Something like only 2% of raw sensory input ever makes it in there to be processed. Shocking, I know. Such an illusion we enjoy, that we are perfectly aware of everything around us all the time. Our brain makes us believe that even while it burns up large amounts of fuel doing its own thing. 

Raichle ME; The restless brain: how intrinsic activity organizes brain function. Philosophical Transactions B 
30 March 2015 (FULL TEXT)

ABSTRACT: Traditionally studies of brain function have focused on task-evoked responses. By their very nature such experiments tacitly encourage a reflexive view of brain function. While such an approach has been remarkably productive at all levels of neuroscience, it ignores the alternative possibility that brain functions are mainly intrinsic and ongoing, involving information processing for interpreting, responding to and predicting environmental demands. I suggest that the latter view best captures the essence of brain function, a position that accords well with the allocation of the brain's energy resources, its limited access to sensory information and a dynamic, intrinsic functional organization. The nature of this intrinsic activity, which exhibits a surprising level of organization with dimensions of both space and time, is revealed in the ongoing activity of the brain and its metabolism. As we look to the future, understanding the nature of this intrinsic activity will require integrating knowledge from cognitive and systems neuroscience with cellular and molecular neuroscience where ion channels, receptors, components of signal transduction and metabolic pathways are all in a constant state of flux. The reward for doing so will be a much better understanding of human behaviour in health and disease.

2.  Abstract only, I'm afraid.. but great paper. It explains, among much else, why octopuses and other very brainy non-vertebrates never made it to the moon while we did. 

"There are two major groups on Earth that have highly developed sensory systems and large brains: the chordates and the cephalopods. Part of the Mollusc phylum, the cephalopods (the nautilus, squid, octopus, and cuttlefish) have never evolved myelin. In addition, they use hemocyanin, which has one-quarter of the oxygen-carrying capacity of hemoglobin. These two factors, the lack of myelinated axons and hemoglobin, hindered the evolution of the cephalopod nervous system, while the descendants of the jawed fish landed on the Moon."

OrĂ³ JJ. Evolution of the brain: from behavior to consciousness in 3.4 billion years. Neurosurgery. 2004 Jun;54(6):1287-96 (ABSTRACT ONLY)

ABSTRACT: Once life began as single-cell organisms, evolution favored those able to seek nutrients and avoid risks. Receptors sensed the environment, memory traces were laid, and adaptive responses were made. Environmental stress, at times as dramatic as the collision of an asteroid, resulted in extinctions that favored small predators with dorsal nerve cords and cranially positioned brains. Myelination, and later thermoregulation, led to increasingly efficient neural processing. As somatosensory, visual, and auditory input increased, a neocortex developed containing both sensory and motor neural maps. Hominids, with their free hands, pushed cortical development further and began to make simple stone tools. Tools and increasing cognition allowed procurement of a richer diet that led to a smaller gut, thus freeing more energy for brain expansion. Multimodal association areas, initially developed for processing incoming sensory information, blossomed and began to provide the organism with an awareness of self and environment. Advancements in memory storage and retrieval gave the organism a sense of continuity through time. This developing consciousness eventually left visible traces, which today are dramatically evident on cave walls in France and Spain. We will take this journey from the single cell to human consciousness.

3.  All about the formation of the nervous system. I LOVE this paper. Why? because it tracks how everything started and how it's all still in there.  Plus I love the "skin/brain thesis" for all my usual biased reasons. Plus it is congruent with all the work Seth Grant has done on protenomics, the proteins that are found at brain synapses, the complexity of them in humans but especially the point he makes about how the ones that work are highly conserved, even from membrane pores of single-cell organisms (like yeast for petesake.. ! Yes, some of our brain synaptic proteins are same as those yeast invented!)

Fred Keijzer; Moving and sensing without input and output: early nervous systems and the origins of the animal sensorimotor organization. Biology & Philosophy 10.1007/s10539-015-9483-1 - FULL TEXT

ABSTRACT: It remains a standing problem how and why the first nervous systems evolved. Molecular and genomic information is now rapidly accumulating but the macroscopic organization and functioning of early nervous systems remains unclear. To explore potential evolutionary options, a coordination centered view is discussed that diverges from a standard input–output view on early nervous systems. The scenario involved, the skin brain thesis (SBT), stresses the need to coordinate muscle-based motility at a very early stage. This paper addresses how this scenario with its focus on coordination also deals with sensory aspects. It will be argued that the neural structure required to coordinate extensive sheets of contractile tissue for motility provides the starting point for a new multicellular organized form of sensing. Moving a body by muscle contraction provides the basis for a multicellular organization that is sensitive to external surface structure at the scale of the animal body. Instead of thinking about early nervous systems as being connected to the environment merely through input and output, the implication developed here is that early nervous systems provide the foundation for a highly specific animal sensorimotor organization in which neural activity directly reflects bodily and environmental spatiotemporal structure. While the SBT diverges from the input–output view, it is closely linked to and supported by ongoing work on embodied approaches to intelligence to which it adds a new interpretation of animal embodiment and sensorimotor organization.

4. Massive amount of information about the skin and all the neurology therein. I have not yet even begun to absorb everything this paper offers. It's likely of interest to dermatologists, mainly, but hey, there is plenty in there to learn about the neurology in/of skin.

Dirk Roosterman , Tobias Goerge , Stefan W. Schneider , Nigel W. Bunnett , Martin Steinhoff;  Neuronal Control of Skin Function: The Skin as a Neuroimmunoendocrine Organ. Physiological Reviews October 1, 2006 Vol. 86 no. 4, 1309-1379 FULL TEXT

ABSTRACT: This review focuses on the role of the peripheral nervous system in cutaneous biology and disease. During the last few years, a modern concept of an interactive network between cutaneous nerves, the neuroendocrine axis, and the immune system has been established. We learned that neurocutaneous interactions influence a variety of physiological and pathophysiological functions, including cell growth, immunity, inflammation, pruritus, and wound healing. This interaction is mediated by primary afferent as well as autonomic nerves, which release neuromediators and activate specific receptors on many target cells in the skin. A dense network of sensory nerves releases neuropeptides, thereby modulating inflammation, cell growth, and the immune responses in the skin. Neurotrophic factors, in addition to regulating nerve growth, participate in many properties of skin function. The skin expresses a variety of neurohormone receptors coupled to heterotrimeric G proteins that are tightly involved in skin homeostasis and inflammation. This neurohormone-receptor interaction is modulated by endopeptidases, which are able to terminate neuropeptide-induced inflammatory or immune responses. Neuronal proteinase-activated receptors or transient receptor potential ion channels are recently described receptors that may have been important in regulating neurogenic inflammation, pain, and pruritus. Together, a close multidirectional interaction between neuromediators, high-affinity receptors, and regulatory proteases is critically involved to maintain tissue integrity and regulate inflammatory responses in the skin. A deeper understanding of cutaneous neuroimmunoendocrinology may help to develop new strategies for the treatment of several skin diseases.

5. Lastly but far from leastly, a recent paper that makes sense of physical contact, providing the PT world with a good reason to retain manual therapy in our profession. Just in case there was ever any danger of it being discarded. Which I hear rumours about from time to time. Also with a path into new avenues of research into what we can do with people, and how we might get the attention of their marvelous, massive, evolved, nervous systems whose parts have been jealously conserved since they evolved and are still all in there, mostly getting along but sometimes not, sometimes one bit creating problems for some other bit, and how we try to help all those bits all get along together better again. Izabela Panek , Tuan Bui, Asher T.B. Wright, and Robert M. Brownstone;  Cutaneous afferent regulation of motor function. Acta Neurobiol Exp 2014, 74: 158–171 FULL TEXT

ABSTRACT: Motor systems must be responsive to the environment in which the organism moves. Accordingly, there are many sensory systems that affect intrinsic motor programs. In this mini review, we will discuss the effects that inputs from cutaneous low-threshold mechanoreceptors have on motor function, focusing on locomotion and hand grasp. A mathematical analysis of grip strength is provided to quantify the regulation of the forces required in maintaining the grip of a moving object. These two behaviours were selected because the neural control of locomotion has been primarily studied for hind-limbs in cats and rodents, whereas hand grasp has been primarily studied in fore-limbs in human and non-human primates. When taken together, insight can be gleaned on the cutaneous regulation of movement as well as the role these afferents may play in mediating functional recovery following injury. We conclude that low-threshold mechanoreceptors are critical for normal motor function and for inducing plasticity in motor microcircuits following injury

1 comment:

Anonymous said...

Thanks Diane!