Central Sensitization: A Generator of Pain Hypersensitivity by Central Neural Plasticity

Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by means of mathematical models. These models are very similar,in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) -usually energy- and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; and the theory that embodies them, "optimal foraging theory." The situations to which optimal foraging theory has been applied, with the exception of a few recent studies, can be divided into the following four categories: (1) choice by an animal of which food types to eat (i.e., optimal diet); (2) choice of which patch type to feed in (i.e., optimal patch choice); (3) optimal allocation of time to different patches; and (4) optimal patterns and speed of movements. In this review we discuss each of these categories separately, dealing with both the theoretical developments and the data that permit tests of the predictions. The review is selective in the sense that we emphasize studies that either develop testable predictions or that attempt to test predictions in a precise quantitative manner. We also discuss what we see to be some of the future developments in the area of optimal foraging theory and how this theory can be related to other areas of biology. Our general conclusion is that the simple models so far formulated are supported are supported reasonably well by available data and that we are optimistic about the value both now and in the future of optimal foraging theory. We argue, however, that these simple models will requre much modification, espicially to deal with situations that either cannot easily be put into one or another of the above four categories or entail currencies more complicated that just energy.

Citation classic - optimal foraging - a selective review of theory and tests

The addition to proteins of the negatively charged polymer of ADP-ribose (PAR), which is synthesized by PAR polymerases (PARPs) from NAD(+), is a unique post-translational modification. It regulates not only cell survival and cell-death programmes, but also an increasing number of other biological functions with which novel members of the PARP family have been associated. These functions include transcriptional regulation, telomere cohesion and mitotic spindle formation during cell division, intracellular trafficking and energy metabolism.

Poly(ADP-ribose): novel functions for an old molecule.

The computational brain: Patricia S. Churchland and Terrence J. Sejnowski (MIT Press, Cambridge, MA, 1992); xi, 544 pages, $39.95

The sections in this article are:


1
Biomechanical and Electromyographical Information
1.1
Single Limb During Locomotion

1.2
Interlimb Coordination

1.3
Treadmill Versus Overground Locomotion

1.4
Trunk Movements During Locomotion

1.5
Pathological Gaits

1.6
Summary




2
Neural Generation of “Basic Locomotor Synergy”
2.1
Central Versus Peripheral

2.2
Parts of CNS of Primary Importance for Neural Control of Basic Locomotor Synergy

2.3
Spinal Centers for Locomotion—Behavioral Results

2.4
Reflex Control of Basic Locomotor Synergy

2.5
Activity in Certain Spinal, Cerebellar, and Brain Stem Neurons and in Certain Reflex Pathways During Locomotion

2.6
Cerebellum and Locomotion

2.7
Initiation of Locomotion—Brain Stem Circuitry

2.8
Central Organization of Spinal Pattern Generation

2.9
Possible Rhythm-Generating Mechanisms and Models—Facts and Fiction

2.10
Developmental Aspects

2.11
Summary




3
Adapting Basic Locomotor Synergy to Animal's Needs
3.1
Changing Speed

3.2
Goal-Directed Locomotion—Turning and Walking Along Curvatures

3.3
Modifications of “Locomotor Posture”

3.4
Positioning of Limb in Each Step

3.5
Reflex Adaptation of Step

3.6
Summary




4
Concluding Remarks

Control of Locomotion in Bipeds, Tetrapods, and Fish

Over the last 30 years, many laboratories have examined, in parallel, the feeding behaviour of gastropod molluscs and the properties of the nervous system that give rise to this behaviour. Equal attention to both behavioural and neurobiological issues has provided deep insight into the functioning of the nervous system in generating and controlling behaviour. The conclusions derived from studies on gastropod feeding are generally consistent with those from other systems, but often provide more detailed information on the behavioural function of a particular property of the nervous system. A review of the literature on gastropod feeding illustrates a number of important messages. (i) Many of the herbivorous gastropods display similarities in behaviour that are reflected in corresponding similarities in neural anatomy, pharmacology and physiology. By contrast, the same aspects of the behaviour of different carnivorous species are quite variable, possibly because of their specialised prey-capture techniques. Nonetheless, some aspects of the neural control of feeding are preserved. (ii) Feeding in all species is flexible, with the behaviour and the physiology adapting to changes in the current environment and internal state and as a result of past experience. Flexibility arises via processes that may take place at many neural sites, and much of the modulation underlying behavioural flexibility is understood at a systems and at a cellular level. (iii) Neurones seem to have specific functions that are consistent with their endogenous properties and their synaptic connections, suggesting that individual neurones code specific pieces of information (i.e. they are 'grandmother cells'). However, the properties of a neurone can be extremely complex and can be understood only in the context of the complete neural circuit and the behaviour that it controls. In systems that are orders of magnitude more complex, it would be impossible to understand the functional properties of an individual neurone, even if it also coded specific information. (iv) Systems such as gastropod feeding may provide a model for understanding the functional properties of more complex systems.

/pdf/comparative-neuroethology-of-feeding-control-in-molluscs-4trxrkf1c6.pdf

Comparative neuroethology of feeding control in molluscs

Nitric oxide (NO) is widely used in neural circuits giving rise to learning and memory. NO is an unusual neurotransmitter in its modes of release and action. Is its association with learning and memory related to its unusual properties? Reviewing the literature might allow the formulation of a general principle on how NO and memory are related. However, other than confirming that there is indeed a strong association between NO and memory, no simple rules emerge on the role of NO in learning and memory. The effects of NO are not associated with a particular stage or form of memory and are highly dependent on species, strain, and behavior or training paradigm. Nonetheless, a review does provide hints on why NO is associated with learning and memory. Unlike transmitters acting via receptors expressed only in neurons designed to respond to the transmitter, NO is a promiscuous signal that can affect a wide variety of neurons, via many molecular mechanisms. In circuits giving rise to learning and memory, it may be useful to signal some events via a promiscuous messenger having widespread effects. However, each circuit will use the promiscuous signal in a different way, to achieve different ends.

Nitric Oxide and Memory

PolyADP-ribose-polymerase 1 is activated in neurons that mediate several forms of long-term memory in Aplysia. Because polyADP-ribosylation of nuclear proteins is a response to DNA damage in virtually all eukaryotic cells, it is surprising that activation of the polymerase occurs during learning and is required for long-term memory. We suggest that fast and transient decondensation of chromatin structure by polyADP-ribosylation enables the transcription needed to form long-term memory without strand breaks in DNA.

https://science.sciencemag.org/content/sci/304/5678/1820.full.pdf

Long-Term Memory Requires PolyADP-ribosylation

Two patterns of neural activity were identified in excised buccal ganglia of Aplysia californica. Both are expressed in many cells, and each can be expressed independently. Using cells B4 and B5 as monitors of the activity patterns, we searched the buccal ganglia for cells initiating the patterns. Two electrically coupled cells, B31 and B32, can initiate what we termed pattern 2. The cells are active before pattern 2 is expressed. Stimuli initiating pattern 2 excite B31/B32. Depolarizing B31/B32 induces the pattern, while hyperpolarizing them can prevent its expression. The cells have unusual features. Their somata do not sustain conventional action potentials, and depolarization causes a regenerative response. B33 differs from B31/B32 in that its soma sustains conventional action potentials but otherwise has similar features. B34 also seems to be inexcitable but has weaker synaptic input than B31/B32 and appears unable to induce pattern 2. B35 and B36 have prominent regenerative capabilities. B35 is also able to initiate pattern 2. B37 is presynaptic to B31/B32 and can initiate pattern 2 via its effects on them. The newly identified cells provide a starting point for investigating factors that initiate and control different patterns of neural activity in the buccal ganglia. Since the buccal ganglia are involved in generating feeding behavior, further studies on the newly identified cells may provide insights into the neural control of feeding behavior, and provide a neural substrate for studying modulation of the feeding patterns by associative learning.

https://www.jneurosci.org/content/jneuro/8/6/2049.full.pdf

Identification and characterization of neurons initiating patterned neural activity in the buccal ganglia of Aplysia

1. B31 and B32 are pattern-initiator neurons in the buccal ganglia of Aplysia. Along with the B61/B62 neurons, B31/B32 are also motor neurons that innervate the 12 buccal muscle via the I2 nerve. T...

Activity patterns of the B31/B32 pattern initiators innervating the I2 muscle of the buccal mass during normal feeding movements in Aplysia californica

Abraham J. Susswein

Papers

Comparative neuroethology of feeding control in molluscs

Nitric Oxide and Memory

Long-Term Memory Requires PolyADP-ribosylation

Identification and characterization of neurons initiating patterned neural activity in the buccal ganglia of Aplysia

Activity patterns of the B31/B32 pattern initiators innervating the I2 muscle of the buccal mass during normal feeding movements in Aplysia californica