A novel radiant heat test for assessing pain threshold in human subjects: Measurement stability

New methodologies to assess analgesic response in humans are needed to better integrate preclinical and clinical data. In the present study we examined the test-retest stability of an innovative radiant heat methodology compared with an electrical stimulation methodology. For the radiant heat task, a modified rodent tail flick apparatus was used. The latency for finger withdrawal was recorded. For the electrical stimulation tasks, subjects placed two fingers on two electrodes from which they received a brief series of increasingly intense electrical stimulations. Maximum stimulus intensity (in milliamps) delivered was recorded. On each of 4 test days, the subjects received five test trials with a 10-min interval between trials. All the subjects were tested twice on each apparatus in a counterbalanced design. Finger withdrawal latencies for the radiant heat task did not differ significantly across test trials or test days. Finger withdrawal scores for electrical stimulation increased significantly across test trials as well as test days. These data show that the radiant heat method generates consistent latencies across trials and days, whereas shock produces trends over time. The radiant heat task, which is convenient to operate and inexpensive to build, appears promising as a reliable test of pain threshold in humans.     

Temporal summation of pain from radiant stimulation

Latency thresholds of pricking pain, using radiant thermal stimulation, were obtained. Ten Ss were tested for 10 sessions, and, in each session, single latency determinations were made at each of 10 stimulus intensities. Each intensity was administered to a different spot along the volar surface of S’s nonpreferred forearm. Thus, 10 latency thresholds were obtained from each S at. each intensity and each spot. Initial skin temperature was controlled so that a threshold determination was made when skin temperature measured 33.5° ± 0.5° C. Analysis of variance of the log₁₀ t (seconds) values revealed a highly significant linearity of regression of log t on log intensity, thus confirming the hypothesized inverse and exponential relationship between latency and intensity. The parameters (slope and x-intercept) of the curve were discussed. The x-intercept may be interpreted as an index of an aversive threshold and could be used as a possible measure of the physiological component of pain.     

恶性肿瘤皮肤表现

恶性肿瘤皮肤表现可分为肿瘤直接效应与间接效应。直接效应是指恶性肿瘤或其转移灶生长影响周围器官或组织正常功能;间接效应是指恶性肿瘤或其转移灶经复杂生物学效应影响远处器官或组织正常功能,也称为副肿瘤性皮肤病。恶性肿瘤皮肤表现发病率根据原发肿瘤而束同,可能是患者潜在肿瘤首发临床表现,并且与肿瘤复发转移相关。     

Operant stimulus control applied to maze behavior: heat escape conditioning and discrimination reversal in alligator Mississippiensis

Eight alligators were trained to escape heat by traversing an 8-ft runway containing right or left approaches to a water tank. All subjects were run until they had satisfied three criteria of stable response time, after which the predominant escape path was blocked, requiring discrimination reversal. Seven subjects again met the criteria; three also met them in a second reversal.     

恶性肿瘤皮肤表现

恶性肿瘤皮肤表现可分为肿瘤直接效应与间接效应.直接效应是指恶性肿瘤或其转移灶生长影响周围器官或组织正常功能;间接效应是指恶性肿瘤或其转移灶经复杂生物学效应影响远处器官或组织正常功能,也称为副肿瘤性皮肤病.恶性肿瘤皮肤表现发病率根据原发肿瘤而不同,可能是患者潜在肿瘤首发临床表现,并且与肿瘤复发转移相关.     

Counterfactual discrimination

In counterfactual cases of discrimination, an agent would have treated someone worse had circumstances been different such that instead of being a member of her actual group, she was a member of some other group. The case for considering such cases to be genuine cases of discrimination is bolstered by the fact that we are inclined to say that cases where an agent would have treated someone better had she been a member of another group are discriminatory. But I argue that the cases are relevantly different: in one kind of case, but not the other, a person is harmed. I then consider and reject a number of objections to this suggestion.     

Effect of prior Pavlovian discrimination training upon learning an operant discrimination

The effect of Pavlovian discrimination training with two stimuli upon subsequent learning of an operant discrimination involving those stimuli was studied. After preliminary lever press training, the lever was removed and thirsty rats received noncontingent pairings between S₁ (a tone or a clicker) and water reinforcements, whereas S₂ (a clicker or a tone) occurred always without reinforcement. This procedure presumably established S₁ as a positive CS for respondent behavior, whereas S₂ was established as an inhibitory CS. Following this training, the lever was reintroduced and the rats were trained on an operant (lever pressing) discrimination involving S₁ and S₂. For the Consistent Ss, S₁ was the S^D and S₂ the S^Δ in the operant discrimination; for the Reversed Ss, S₂ served as S^D and S₁ as S^Δ. The Consistent Ss learned the operant discrimination significantly faster than did the Reversed Ss. The result emphasizes the importance of respondents, conditioned to S^D and S^Δ, which modulate operant performance to these stimuli.     

The badness of discrimination

The most blatant forms of discrimination are morally outrageous and very obviously so; but the nature and boundaries of discrimination are more controversial, and it is not clear whether all forms of discrimination are morally bad; nor is it clear why objectionable cases of discrimination are bad. In this paper I address these issues. First, I offer a taxonomy of discrimination. I then argue that discrimination is bad, when it is, because it harms people. Finally, I criticize a rival, disrespect-based account according to which discrimination is bad regardless of whether it causes harm.     

Visual discrimination of texture

Julesz (1975) proposed a theory of texture discrimination, based on an order statistics principle, which states that no two textures can be perceptually discriminated if they have identical second-order statistics. The experiments reported here demonstrate that this principle is not adequate to predict visual texture discriminability. Both letter and dot micropatterns were used to create texture pairs that either differed or were identical with respect to secondorder statistics. The subject’s task was to decide which quadrant of an array contained a disparate texture. In Experiments 1, 2, and 3, when controlling for spatial overlap, texture pairs having identical second-order statistics were discriminated more quickly than similar texture pairs having different second-order statistics, in contradiction to the principle. Although a significant effect in the direction predicted by the order statistics principle was found in Experiment 4 for texture pairs created from the dot micropatterns, other factors, such as spatial overlap, border differences, and goodness of pattern, must also be considered in predicting texture discriminability.     

Chlordiazepoxide-induced discrimination impairment

Chlordiazepoxide (5.0 and 10.0 mg/kg but not 2.5 mg/kg) administered on 10 successive sessions, significantly impaired the reinforcement-cued discrimination performance of male Sprague-Dawley rats. On three postdrug (saline) recovery sessions, groups previously treated with the drug demonstrated good recovery in discrimination performance. An analysis of response components indicated that the discrimination impairment was due to less inhibition of responding during "no-go" phases of the task by the drugged than control animals. While changes in responding during reinforcement phases may also contribute to the performance of drugged animals, no clear pattern emerges from the present study.