The formalin test and the opioid nature of stress-induced analgesia

Exposure to electric shock produces an analgesic reaction (SIA) that is reversed by opiate antagonists ("opioid" SIA) under some conditions but not under other conditions ("nonopioid" SIA). A number of studies using tail-flick to radiant heat as the measure of pain sensitivity have found that a small number of shocks lead to nonopioid SIA, while a large number of shocks produce opioid SIA. In contrast, a small number of shocks have been reported to produce opioid SIA when the Formalin test was used to measure pain reactivity. However, the Formalin test involves administering a chronic pain stimulus (injection of Formalin into the paw) for an extended period before the shocks. Here it is reported that this "preexperimental" stress is sufficient to convert the SIA after a small number of shocks measured by tail-flick to the opioid form.     

Acquisition and retention of gestures by apraxic patients

The purpose of this study was to examine whether apraxic-aphasic patients with parietal lesions had difficulty learning lists of gestures and whether the performance deficits they displayed resulted from an inability either to consolidate this information in memory or to retrieve the information once stored. The findings indicate that apraxic-aphasic patients do have difficulty acquiring lists of gestures. This inability to reproduce gestural information was not associated with a retrieval disorder, but instead the apraxic-aphasic subjects could not consolidate the information in memory.     

Explaining the Psychological Effects of Unemployment for Young People: The Importance of Specific Situational Factors

Evidence of the effects of duration of unemployment and gender upon the psychological response to unemployment is reviewed. It is suggested that many of the apparent contradictions in this evidence can be resolved by reference to situational factors which shape how stressful unemployment is for a particular individual. The study reported tested the effects of a stressful period of unemployment on the psychological well-being, self-esteem and life-satisfaction of young people. No sex differences in response to unemployment were found, and this is explained in terms of the similarity of their experiences. The relevance of these findings for counselling the unemployed is discussed.     

Odor recognition: familiarity, identifiability, and encoding consistency

The investigation examined the association between the perceived identity of odorous stimuli and the ability to recognize the previous occurrence of them. The stimuli comprised 20 relatively familiar odorous objects such as chocolate, leather, popcorn, and soy sauce. Participants rated the familiarity of the odors and sought to identify them. At various intervals up to 7 days after initial inspection, the participants sought to recognize the odors among sets of distractor odors that included such items as soap, cloves, pipe tobacco, and so on. The recognition response entailed a confidence rating as to whether or not an item had appeared in the original set. At the time of testing, the participants also sought to identify the stimuli again. The results upheld previous findings of excellent initial recognition memory for environmentally relevant odors and slow forgetting. The results also uncovered, for the first time, a strong association between recognition memory and identifiability, rated familiarity, and the ability to use an odor label consistently at inspection and subsequent testing. Encodability seems to enhance rather than to permit recognizability. Even items identified incorrectly or inconsistently were recognized at levels above chance.     

Representation of linear orders

Two binary classification tasks were used to explore the associative structure of linear orders. In Experiment 1, college students classified English letters as targets or nontargets, the targets being consecutive letters of the alphabet. The time to reject nontargets was a decreasing function of the distance from the target set, suggesting response interference mediated by automatic associations from the target to the nontarget letters. The way in which this interference effect depended on the placement of the boundaries between the target and nontarget sets revealed the relative strengths of individual interletter associations. In Experiment 2, students were assigned novel linear orders composed of letterlike symbols and asked to classify pairs of symbols as being adjacent or nonadjacent in the assigned sequence. Reaction time was found to be a joint function of the distance between any pair of symbols and the relative positions of those symbols within the sequence. The effects of both distance and position decreased systematically over 6 days of practice with a particular order, beginning at a level typical of unfamiliar orders and converging on a level characteristic of familiar orders such as letters and digits. These results provide an empirical unification of two previously disparate sets of findings in the literature on linear orders, those concerning familiar and unfamiliar orders, and the systematic transition between the two patterns of results suggests the gradual integration of a new associative structure.     

The timing of natural prehension movements

Prehension movements were studied by film in 7 adult subjects. Transportation of the hand to the target-object location had features very similar to any aiming arm movement, that is, it involved a fast-velocity initial phase and a low-velocity final phase. The peak velocity of the movement was highly correlated with its amplitude, although total movement duration tended to remain invariant when target distance was changed. The low-velocity phase consistently began after about 75% of movement time had elapsed. This ration was maintained for different movement amplitudes. Formation of the finger grip occurred during hand transportation. Fingers were first stretched and then began to close in anticipation to contact with the object. The onset of the closure phase was highly correlated to the beginning of the low velocity phase of transportation. This pattern for both transportation and finger grip formation was maintained in conditions whether visual feedback from the moving limb was present or not. Implications of these findings for the central programming of multisegmental movements are discussed.     

The micro-structure of tapping movements in children

In order to investigate the development of movement speed in relation to movement organization, children of 5, 6, 7, 8 and 9 years of age and adults carried out a reciprocal tapping task, in which time pressure and distance were manipulated. The duration, velocity, acceleration and accuracy of the movements were compared between age groups. Age differences appeared mainly in the homing time, not in the duration of the distance covering movement phase. Accuracy and velocity of the distance covering movement phase differed with age. Time pressure affected the homing time, but not the duration of the distance covering phase. Distance manipulation affected mainly the velocity and duration of the distance covering movement phase and the homing time. In the discussion it is contended that age differences in homing time may be related to both the accuracy of the distance covering movement phase and the rate of information processing of the subject.     

Programming time as a function of number of movement parts and changes in movement direction

The question of whether changes seen in simple reaction time (SRT) as a function of response complexity (i.e., number of movement parts) should be considered as differences in the time needed to centrally program a motor response was addressed. Using a large-scale tapping response, 14 subjects contacted from one to five targets positioned in a straight line, while a second group of 14 subjects executed 90 degrees changes in direction in striking the targets. Results revealed that mean SRT and mean premotor time increased linearly as the number of movement parts increased, regardless of whether changes in movement direction had to be programmed, with the greatest increase occurring between one-, and two-part responses. Increases in motor time were not sufficient to account for the sizeable SRT effect. These findings support the position of increased central programming time for more complex responses, and also help establish some of the boundaries of the complexity effect.