Unconditioned stimulus

Acquas E, Wilson C, Fibiger HC. 1996. Conditioned and unconditioned stimuli increase frontal cortical and hippocampal acetylcholine release effects of novelty, habituation, and fear. J Neurosci 16(9) 3089-3096. 

Conditioning. A Pavlovian explanation of placebo effects has been based on the traditional model of classical conditioning active ingredients serve as unconditional stimuli and the vehicles in which they are delivered (pills, injections), particularly the elements of therapeutic procedures, function as conditional stimuli. After repeated pairing of unconditioned and conditioned stimuli, the conditional stimulus elicits a conditional response even if the conditioned stimulus (e.g. the pill) is presented alone (without active ingredient). 

Thus the problem is not the nonexistence of classical conditioning, either in the laboratory or in creating ordinary appetites. On the contrary, conditioning is a familiar phenomenon. The problem is that conditioning per se connects only information—one stimulus to another—and does not transfer responses. Responses certainly arise to conditioned stimuli, and these responses often closely resemble the responses elicited by unconditioned stimuli, but the evidence is that they occur only insofar as they are motivated. 

From the above analysis two views of the behavioral function of the NAc shell versus core emerge according to one view (Corbit et al., 2001) the functions of the NAc core and of the NAc shell are distinct and pertain to separate, although interacting, aspects of responding, instrumental and Pavlovian, respectively. According to another view (Everitt et al., 1999), the NAc core plays a role in the influences exerted by Pavlovian stimuli on instrumental behavior as well as in directional/discriminative aspects of instrumental responding while the NAc shell is involved in the incentive influences exerted by unconditioned stimuli. 

Mechanism through which repeated associations between two stimuli induce a new learned response. In particular, by pairing a neutral stimulus (conditioned stimulus) with an unconditioned stimulus (that induces a physiological response) many times, the neutral stimulus alone will be capable of producing a conditioned physiological response. 

Eikelboom, R., and Stewart, J., Conditioned temperature effects using morphine as the unconditioned stimulus, Psychopharmacology, 61, 31, 1979. 

Fig. 29.2 A. Proportion of pups responding by searching movements to neutral odorant E and F, 24h after being exposed to the MP-odorant E mixture (MP-E) or to odorant E alone (E). B. Proportion of pups displaying searching to an odorant MP-leamed (dotted bar) as compared to the MP (black bar). C. Schematic of the reinforcing function of MP (US, CS and UR unconditioned stimulus, conditioned stimulus and unconditioned response, respectively) (adapted from Coureaud et al. 2006c)...

Referred to as a conditioned fear paradigm, the fear potentiated startle response was first described by Brown et al. (1951). In the original test, an acoustic stimulus is presented in the presence of a conditioned stimulus that has previously been paired with an aversive, unconditioned stimulus. The amplitude of the acoustic startle response is thought to indicate the degree of conditioned anxiety, which can be reduced by anxiolytic drugs (Davis et al. 1993 Hijzen et al. 1995). 

In classical Pavlovian fear conditioning, an initially neutral cue (conditioned stimulus, CS), through temporal pairing with an aversive unconditioned stimulus (US), acquires the abihty to ehcit a fear response in the absence of the US. This acquired abihty represents a type of associative learning and imphes that plasticity mechanisms underlying fear learning may be similar to those... 

In a fear-conditioning experiment, a neutral stimulus, such as a tone or a light, is paired with an aversive stimulus, such as a shock, a loud noise, or an aversive air blast. Following this experience, the formerly neutral stimulus becomes a conditioned stimulus (CS-F) and acquires the ability to elicit behaviors and physiological responses formerly only associated with the aversive stimulus, the unconditioned stimulus (UCS). Enthusiasm for this work derives at least partly from the precise delineation of neural circuits, down to the level of the genome, engaged by environmental components that produce fear conditioning (LeDoux,... 

Classical or Pavlovian conditioning was first demonstrated by Ivan Pavlov in 1927. When food was presented to a hungry dog, it salivated. The food in this case was called the unconditioned stimulus, and salivating was the unconditioned response. Salivation is a natural, automatic response to the sight and smell of food, a reaction to make the chewing and digestion of the food easier. 

The conditioned association between the formerly neutral conditioned stimulus and the conditioned response is formed by the deliberate pairing of the conditioned stimulus and the unconditioned response. Suppose we now break up that pairing, continuing to present the conditioned stimulus, but no longer following it with the unconditioned stimulus. ... 

Catecholamine—Monoamines such as the neurotransmitters norepinephrine, serotonin, and dopamine that are synthesized from the amino acid, tyrosine, and have similar structures. Conditioned reflex—response in which one stimulus, the conditioned one, is associated with and elicits the same response as another stimulus, the unconditioned stimulus. 

In the shuttle box the acquisition of a two-way CAR was analyzed during 5 consecutive days. The rat was put in a box divided inside into two parts by a barrier with a small gate in the middle, and the animal was trained to cross the barrier under the influence of a conditioned stimulus (CS, fight flash). If it failed to respond within 5 s, it was punished with an unconditioned stimulus (US), a footshock (1 mA). If the rat failed to respond within 5 s to the US, it was classified as an escape failure (EF). One trial consisted of a 15 s intertrial interval (IR), followed by 15 s CS. The last 5 s of CS overlapped the 5 s of US. At each learning session, the number of CARs, EFs and IRs were automatically counted and evaluated by multi-way ANOVA. 

HAMMER, M., An identified neuron mediates the unconditioned stimulus in associative olfactory learning in honeybees. Nature, 1993, 366, 59-63. 

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