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PubMed1997

A neural network based artificial vision system for licence plate recognition.

This paper presents a neural network based artificial vision system able to analyze the image of a car given by a camera, locate the registration plate and recognize the registration number of the car. The paper describes in detail various practical problems encountered in implementing this particular application and the solutions used to solve them. The main features of the system presented are: controlled stability-plasticity behavior, controlled reliability threshold, both off-line and on-line learning, self assessment of the output reliability and high reliability based on high level multiple feedback. The system has been designed using a modular approach. Sub-modules can be upgraded and/or substituted independently, thus making the system potentially suitable in a large variety of vision applications. The OCR engine was designed as an interchangeable plug-in module. This allows the user to choose an OCR engine which is suited to the particular application and to upgrade it easily in the future. At present, there are several versions of this OCR engine. One of them is based on a fully connected feedforward artificial neural network with sigmoidal activation functions. This network can be trained with various training algorithms such as error backpropagation. An alternative OCR engine is based on the constraint based decomposition (CBD) training architecture. The system has showed the following performances (on average) on real-world data: successful plate location and segmentation about 99%, successful character recognition about 98% and successful recognition of complete registration plates about 80%.

Algorithms↗
PubMed1986

Food avoidance learning is accompanied by synaptic attenuation in identified interneurons controlling feeding behavior in Pleurobranchaea.

Identified paracerebral feeding command interneurons (PCNs) in the brain of the mollusc Pleurobranchaea excite other identified PCNs by means of a chemical polysynaptic pathway whose efficacy is reduced by food avoidance training (conditionally paired food and electric shock). The purpose of the present study was to identify the neurons comprising this pathway and to localize learning-induced changes to single identified neurons. We found that associative training strongly attenuates or abolishes a unitary excitatory postsynaptic potential (EPSP) at a single identified synapse in this polysynaptic pathway, but does not alter other synapses. The PCNs descend to the buccal ganglion, where they monosynaptically excite each member of a set of four identified neurons (two per hemiganglion) that belong to the corollary discharge population described previously. The strength of ascending and descending synapses involving identified PCNs is greatest ipsilaterally and is proportional to relative command efficacy established in previous studies. These findings suggest that command efficacy results directly from synaptic strength. The pair of corollary discharge neurons on each side of the buccal ganglion sends axons to the opposite side and thence up the contralateral cerebrobuccal connective to the brain. These neurons have therefore been termed the contralateral corollary discharge (CCD) neurons. Each CCD monosynaptically excites every PCN on both sides of the brain. Contralateral synaptic influences on identified PCNs are larger than ipsilateral ones. Each of the four identified CCD neurons is electrically coupled to all other members of the subset, including the contralateral homologue (based on simultaneous intracellular recording) and the ipsilateral partner (based on dye coupling). Hyperpolarizing a single CCD eliminates the polysynaptic response of PCNs to stimulation of other PCNs, whereas depolarizing a single CCD mimics the polysynaptic response. The CCD neurons are therefore necessary and sufficient to the polysynaptic response. Consistent with this role, the CCDs discharge in phase with the PCNs during the feeding motor program, and hyperpolarizing a CCD abolishes the cycle discharge of PCNs and weakens the feeding rhythm. Of the several reciprocal synapses identified between the PCNs and CCDs, only one was significantly altered by associative training in the food avoidance paradigm developed previously. This synapse, from the polysynaptic excitor (PSE) to the ipsilateral CCD, was also the strongest in this recurrent positive-feedback loop. In brains taken from conditioned specimens, the mean EPSP amplitude induced by a PSE action potential in ipsi

Action Potentials↗
PubMed2005

Controlling cell behavior electrically: current views and future potential.

Direct-current (DC) electric fields are present in all developing and regenerating animal tissues, yet their existence and potential impact on tissue repair and development are largely ignored. This is primarily due to ignorance of the phenomenon by most researchers, some technically poor early studies of the effects of applied fields on cells, and widespread misunderstanding of the fundamental concepts that underlie bioelectricity. This review aims to resolve these issues by describing: 1) the historical context of bioelectricity, 2) the fundamental principles of physics and physiology responsible for DC electric fields within cells and tissues, 3) the cellular mechanisms for the effects of small electric fields on cell behavior, and 4) the clinical potential for electric field treatment of damaged tissues such as epithelia and the nervous system.

Animals↗
PubMed2002

Estrogen, progesterone, and pregnancy termination alter neural activity in brain regions that control maternal behavior in rats.

Estrogen stimulates maternal behavior in rats, but does so most potently when its administration is temporally coupled with the termination of pregnancy. In contrast, this effect of estrogen is blocked when subjects are administered a large dose of progesterone concurrent with estrogen. The current study was performed to examine the neural circuitry influenced by these treatments and pup presentation during the hormonally-mediated onset and inhibition of maternal behavior. In experiment I, estrogen induced c-Fos immunoreactivity (Fos-IR) in the medial preoptic area (MPOA) in virgin rats, but was much more effective when administered to pregnancy-terminated rats, suggesting that pregnancy termination increases MPOA's susceptibility to the physiological effects of estrogen. In experiment II, administering progesterone concurrently with estrogen in pregnancy-terminated rats strongly inhibited estrogen-stimulated Fos-IR in the MPOA, indicating that the physiological effects of estrogen on the MPOA are blocked if high progesterone levels are maintained. In experiment III, pregnancy-terminated subjects were administered estrogen, progesterone, or both hormones and presented with pups for 2 h. Approximately half of the subjects administered estrogen alone showed maternal behavior, but subjects receiving the other treatments were not maternal. In the MPOA, ventral bed nucleus of the stria terminalis (BSTv), and dorsal and intermediate lateral septum (LSd,i), maternal subjects showed the highest levels of Fos-IR, whereas subjects treated with progesterone alone or progesterone in combination with estrogen showed low levels of Fos-IR. These experiments suggest that estrogen could promote maternal behavior by enhancing pup-stimulated activity in the MPOA, BSTv, and LSd,i, regions believed to constitute the neural circuit that promotes maternal behavior, whereas progesterone could inhibit maternal behavior by inhibiting neural activity in some of these regions.

Animals↗
PubMed1987

Relationship between Russian roulette deaths and risk-taking behavior: a controlled study.

A review of medical examiner records yielded data on 19 men and one woman who died playing Russian roulette. The men differed significantly from 95 male suicide victims who died of gunshot wounds to the head on several variables including age, race, ethnicity, religion, citizenship, marital status, living situation, health, and the likelihood of the death being witnessed. The Russian roulette victims were significantly less likely to die in the bedroom, die in the morning, leave a suicide note, and be depressed but were significantly more likely to have alcohol or drugs in their body fluids and to have a previous history of drug and alcohol abuse.

Adult↗
PubMed1996

Intestinal Na+ and Cl- levels control drinking behavior in the seawater-adapted eel Anguilla japonica

To analyze drinking mechanisms in seawater teleosts, seawater-adapted eels were used as a model system. When the intestine of the eel was perfused with iso-osmotic mannitol, the eels drank sea water. However, when the perfusion medium was switched to iso-osmotic NaCl, seawater drinking was depressed. This depression was observed even after blocking NaCl absorption across the intestine by replacement of the perfusate with choline chloride or by treatment with furosemide, an inhibitor of NaCl and water absorption across the eel intestine. Furthermore, depression of drinking rate preceded an increase in urine flow by over 1 h. These results indicate that this depression is not due to a recovery of blood volume and suggest that intestinal Cl- itself inhibits drinking. Direct action of luminal Cl- on drinking behavior was further supported by the observation that perfusion with iso-osmotic NMDG-HCl, Tris-HCl, choline chloride and RbCl all inhibited seawater drinking. When NaCl in the perfusion medium was replaced with sodium acetate, sodium butyrate, sodium methylsulfate or NaSCN, the drinking rate was enhanced threefold, suggesting that Na+ itself stimulates drinking in the absence of Cl-. In the present study, concentrations of Na+ and Cl- in the swallowed fluid were also measured simultaneously. As the drinking rate was enhanced, the Na+ and Cl- concentrations in the gastrointestinal fluid were increased. On the basis of these results, it seems possible that high concentrations of Cl- in the intestine reduce the drinking rate, thus lowering esophageal Cl- concentration due to desalination of the ingested sea water. When Cl- concentration in the intestine falls below a certain level, Na+ will stimulate seawater drinking again.

Journal Article↗
PubMed1970

Effects of a pre-shock stimulus on temporal control of behavior.

Rats were exposed to a situation in which a response on lever B was followed by reinforcement if a preceding response on lever A had been made at least 5, 10, or 15 sec before. The effects of signalled unavoidable shock were studied on the behavior maintained by this procedure. All rats made fewer A-to-B sequences during the periods of pre-shock stimulus. In addition, when the A-to-B delay was 10 or 15 sec, the distribution of A-to-B times changed, there being more shorter intervals. However, for animals where the A-to-B delay was 5 sec, the distribution of A-to-B times was not changed during the pre-shock stimulus. In all cases, there was an increased proportion of inappropriate B responses (i.e., with no preceding A response) during the pre-shock stimulus; this was most marked with animals exposed to a 15-sec A-to-B delay.

Journal Article↗
PubMed1978

Species differences in temporal control of behavior II: human performance.

Human subjects responded on two panels. A differential-reinforcement-of-low-rate schedule with a limited-hold contingency operated on Panel A. In Condition 1, responses on Panel B produced a stimulus on the panel that signalled whether reinforcement was available on Panel A. In Condition 2, responses on Panel B briefly illuminated a digital clock. In both conditions, performance on Panel A was very efficient; with few exceptions, Panel A was pressed only when reinforcement was available. Thus, in effect, a fixed-interval schedule operated on Panel B. In Condition 1, a "break-and-run" response pattern occurred on Panel B; with increasing temporal parameters, the duration of the postreinforcement pause on Panel B increased linearly while overall response rate and running rate (calculated by excluding the postreinforcement pauses) remained approximately constant. In Condition 2, the response pattern on Panel B was scalloped; the postreinforcement pause was a negatively accelerated increasing function of schedule value, while overall response rate and running rate were negatively accelerated decreasing functions of schedule value. The performance of subjects in Condition 2, but not in Condition 1, was highly sensitive to the contingencies in operation, and resembled that of other species on the fixed-interval schedule.

Journal Article↗
PubMed1979

Temporal control of behavior and the power law.

The performance of rats and pigeons under fixed-interval schedules was studied in two experiments. The duration of postreinforcement pause was a declining proportion of fixed-interval duration. For pigeons this was true both when the duration of the reinforcer was fixed and when it was increased in direct proportion to increases in fixed-interval duration; the longer reinforcer durations did, however, lengthen the postreinforcement pause at higher schedule values. A quantitative analysis of data from Experiments 1 and 2 and from other studies showed that fractional exponent power functions described the relationship between postreinforcement pause and fixed-interval value; similar functions have previously been observed in studies of temporal differentiation. It was concluded that power functions reflect a direct causal, rather than artifactual, relationship between performance and the temporal requirements of reinforcement schedules.

Journal Article↗
PubMed1995

Acute effects of inhalation exposure to carbon monoxide on schedule-controlled operant behavior and blood carboxyhemoglobin levels in rats.

The acute effects of carbon monoxide (CO) exposure on a steady-state operant behavior (bar-pressing under a VI 60-sec schedule of food reinforcement) were repeatedly measured in (a) rats exposed to various concentrations of CO (500, 1,000, 1,500 and 2,000 ppm) for 1 h and (b) rats exposed to 1,500 ppm for different periods (1, 2 and 4 h). Measurements were made continuously before, during and after the exposure period. Abrupt cessation of the response was produced by exposure to 1,000 ppm or higher concentrations of CO. Recovery from the effects of CO exposure was observed as sudden resumption of responding during the post-exposure period. The duration of exposure required to produce response inhibition was closely correlated with the exposure concentration. The post-exposure interval required for response recovery was also correlated with the exposure concentration. This post-exposure response recovery interval, however, was constant and independent of the duration of exposure when the concentration was fixed at 1,500 ppm. In order to correlate these behavioral changes with an internal index of CO exposure, blood carboxyhemoglobin (HbCO) levels were determined under several exposure conditions corresponding to those of the behavioral observations. It was found that HbCO levels were within a certain range (33-43%) when response recovery occurred, suggesting the existence of a critical HbCO level (threshold) associated with the drastic behavioral change. Hence, these results support the view that blood HbCO is an important determinant of the acute behavioral effects of CO.

Administration, Inhalation↗