Credence Goods Markets with Conscientious and Selfish Experts

I study credence goods markets when there are both selfish and conscientious experts. The selfish expert is a profit maximizer. The conscientious expert wants to maximize profit and repair the consumer's problem. There are two classes of equilibria: uniform-price equilibria and nonuniform-price equilibria. A consumer cannot infer the expert's type from his price list in a uniform-price equilibrium but can do that in a nonuniform-price equilibrium. When the fraction of the conscientious expert is small, the selfish expert will be honest about the severity of the consumer's problem. When the fraction of the conscientious expert is large, the selfish expert will cheat the consumer; overcharging the consumer whenever he offers to repair the problem. Finally, more conscientious experts may result in a larger social loss. When the fraction of the conscientious expert is close to one of the two extremes, 0 and 1, more conscientious experts will result in smaller social loss. When the fraction of the conscientious expert is in a middle range, more conscientious experts may result in a larger social loss.credence goods markets; conscientious experts; selfish experts; social loss

Credence Goods Markets with Conscientious and Selfish Experts

I study credence goods markets when there are both selfish and conscientious experts. The selfish expert is a profit maximizer. The conscientious expert wants to maximize profit and repair the consumer's problem. There are two classes of equilibria: uniform-price equilibria and nonuniform-price equilibria. A consumer cannot infer the expert's type from his price list in a uniform-price equilibrium but can do that in a nonuniform-price equilibrium. When the fraction of the conscientious expert is small, the selfish expert will be honest about the severity of the consumer's problem. When the fraction of the conscientious expert is large, the selfish expert will cheat the consumer; overcharging the consumer whenever he offers to repair the problem. Finally, more conscientious experts may result in a larger social loss. When the fraction of the conscientious expert is close to one of the two extremes, 0 and 1, more conscientious experts will result in smaller social loss. When the fraction of the conscientious expert is in a middle range, more conscientious experts may result in a larger social loss.credence goods markets; conscientious experts; selfish experts; social loss

Spinal interneurons in sensorimotor integration

Even though spinal cord research has expanded enormously during the past decades, we still lack a precise understanding of how spinal interneuron networks perfectly integrate sensory feedback with motor control, and how these neuron circuits give rise to specific functions. The present study thus has three basic aims: (1) to investigate propriospinal interneurons connecting rostral and caudal lumbar spinal cord in the rat; (2) to investigate input properties of identified spinal interneurons interposed in different pathways; (3) to investigate cholinergic terminals in the ventral horn of adult rat and cat. To realize the first aim, the B-subunit of cholera toxin (CTb) was injected into the motor nuclei at the L1 or L3 segmental level to retrogradely label propriospinal interneurons in the L5 segment of rat spinal cord. These cells had a clear distribution pattern which showed that they were located mainly in ipsilateral dorsal horn and contralateral lamina VIII. A series triple-labelling experiments revealed that about 1/4 of the CTb-positive cells were immunoreactive for calbindin and/or calretinin. It was also found that a small population of CTb labelled cells were cholinergic and were observed mainly in three locations: lamina X, the medial part of intermediate zone and lamina VIII. In addition, injection of CTb also anterogradely labelled axon terminals, which arose from the commissural interneurons (CINs) within the site of injection, crossed the midline and aroborized in the contralateral lateral motor nuclei of the L5 segment. The neurotransmitter systems in labelled axon terminals of CINs were investigated by using antibodies raised against specific transmitter-related proteins. The results showed that approximately 3/4 terminals were excitatory and among those excitatory terminals about 3/4 forming contacts with motoneurons. To achieve the second aim, 21 interneurons located in the intermediate zone and lamina VIII from 7 adult cats were characterised electrophysiologically and labelled intracellularly with Neurobiotin. Seventeen of these cells were activated monosynaptically from primary muscle afferents but the remaining four cells received monosynaptic inputs from the medial longitudinal fasciculus (MLF). Quantitative analysis revealed that cells in the first group received many contacts from excitatory terminals that were immunoreactive for the vesicular glutamate transporter 1 (VGLUT1) but those cells from the second group received few contacts of this type and were predominantly contacted by terminals immunoreactive for vesicular glutamate transporter 2 (VGLUT2). This result was as predicted because VGLUT1 is found principally in the terminals of myelinated primary afferent axons whereas VGLUT2 is located in the terminals of interneurons in the spinal cord. Interneurons in the first group were then characterised as excitatory and inhibitory on the basis of the transmitter content contained within their axon terminals. Although there was a greater density of VGLUT1 contacts on excitatory rather than inhibitory cells, the difference was not statistically significant. GABAergic terminals formed close appositions with VGLUT1 contacts on both excitatory and inhibitory cells. These appositions were likely to be axoaxonic synapses which mediate presynaptic inhibition. In addition, the densities of VGLUT1 and VGLUT2 contacts on 30 dorsal horn CINs and 60 lamina VIII CINs that were retrogradely labelled with CTb from 3 adult rats were compared. The results showed that VGLUT2 terminals formed the majority of excitatory inputs to both dorsal horn and lamina VIII CINs but dorsal horn CINs received a significantly greater density of VGLUT1/2 inputs than lamina VIII CINs. In order to achieve the third aim, i.e. whether glutamate is a cotransmitter at motoneuron axon collateral terminals in the ventral horn, a series of anatomical experiments were performed on axon collaterals obtained from motoneurons from an adult cat and retrogradely labelled by CTb in adult rats. There was no evidence to support the presence of vesicular glutamate transporters in motoneuron axon terminals of either species. In addition, there was no obvious relationship between motoneuron terminals and R2 subunit of the AMPA receptor (GluR2). However, a population of cholinergic terminals in lamina VII, which did not originate from motoneurons, was found to be immunoreactive for VGLUT2 and formed appositions with GluR2 subunits. These terminals were smaller than motoneuron terminals and, unlike them, formed no relationship with Renshaw cells. The evidence suggests that glutamate does not act as a cotransmitter with acetylcholine at central synapses of motoneurons in the adult cat and rat. However, glutamate is present in a population of cholinergic terminals which probably originate from interneurons where its action is via an AMPA receptor. In conclusion, the present studies add to the understanding of the organization of neuronal networks involved in sensorimotor integration. Propriospinal interneurons located within the lumbar segments have extensive intra-segmental projections to motor nuclei. First order interneurons interposed in reflex pathways and descending pathways receive a significantly different pattern of inputs. A similar proportion of monosynaptic excitatory input from primary afferents has been found in both excitatory and inhibitory interneurons and these two types of cells are subject to presynaptic inhibitory control of this input

Neural Mechanism of Language

This paper is based on our previous work on neural coding. It is a self-organized model supported by existing evidences. Firstly, we briefly introduce this model in this paper, and then we explain the neural mechanism of language and reasoning with it. Moreover, we find that the position of an area determines its importance. Specifically, language relevant areas are in the capital position of the cortical kingdom. Therefore they are closely related with autonomous consciousness and working memories. In essence, language is a miniature of the real world. Briefly, this paper would like to bridge the gap between molecule mechanism of neurons and advanced functions such as language and reasoning.Comment: 6 pages, 3 figure

A Quantitative Neural Coding Model of Sensory Memory

The coding mechanism of sensory memory on the neuron scale is one of the most important questions in neuroscience. We have put forward a quantitative neural network model, which is self organized, self similar, and self adaptive, just like an ecosystem following Darwin theory. According to this model, neural coding is a mult to one mapping from objects to neurons. And the whole cerebrum is a real-time statistical Turing Machine, with powerful representing and learning ability. This model can reconcile some important disputations, such as: temporal coding versus rate based coding, grandmother cell versus population coding, and decay theory versus interference theory. And it has also provided explanations for some key questions such as memory consolidation, episodic memory, consciousness, and sentiment. Philosophical significance is indicated at last.Comment: 9 pages, 3 figure

A Unified Quantitative Model of Vision and Audition

We have put forwards a unified quantitative framework of vision and audition, based on existing data and theories. According to this model, the retina is a feedforward network self-adaptive to inputs in a specific period. After fully grown, cells become specialized detectors based on statistics of stimulus history. This model has provided explanations for perception mechanisms of colour, shape, depth and motion. Moreover, based on this ground we have put forwards a bold conjecture that single ear can detect sound direction. This is complementary to existing theories and has provided better explanations for sound localization.Comment: 7 pages, 3 figure

Motor Learning Mechanism on the Neuron Scale

Based on existing data, we wish to put forward a biological model of motor system on the neuron scale. Then we indicate its implications in statistics and learning. Specifically, neuron firing frequency and synaptic strength are probability estimates in essence. And the lateral inhibition also has statistical implications. From the standpoint of learning, dendritic competition through retrograde messengers is the foundation of conditional reflex and grandmother cell coding. And they are the kernel mechanisms of motor learning and sensory motor integration respectively. Finally, we compare motor system with sensory system. In short, we would like to bridge the gap between molecule evidences and computational models.Comment: 8 pages, 4 figure