Amodal completion and the perception of depth without binocular correspondence

Half-occlusions and illusory contours have recently been used to show that depth can be perceived in the absence of binocular correspondence and that there is more to stereopsis than solving the correspondence problem. In the present study we show a new way for depth to be assigned in the absence of binocular correspondence, namely amodal completion. Although an occluder removed all possibility of direct binocular matching, subjects consistently assigned the correct depth (convexity or concavity) to partially occluded 'folded cards' stimuli. Our results highlight the importance of more global, surface-based processes in stereopsis.     

Effect of chronic intermittent immobilization stress on Fos-like immunoreactivity in rat brain and adrenal medulla

The present study examined the influence of short- and long-term chronic intermittent immobilization stress throughout the brain and on the adrenal medulla of intact rats using Fos-like immunoreactivity (Fos-LI) as a marker of cellular activation. The effect of adreno-medullectomy on the central nervous system (CNS) response to chronic immobilization stress was also examined. It was found that control unoperated, unstressed rats had no Fos-LI cells in the brain or in the adrenal medulla. In intact rats, neither short term (1 week) nor long term (4 weeks) chronic intermittent immobilization stress produced significant increases in Fos-LI in the CNS compared with control animals. However, marked increase in the number of Fos-LI cells was observed in the adrenal medulla of animals stressed for 4 weeks compared with control, unstressed animals or those stressed for 1 or 2 weeks. In adreno-medullectomised rats, 4 weeks, but not 1 week, chronic immobilization stress produced significant increases in numbers of Fos-LI neurons in the paraventricular hypothalamic and supraoptic nuclei and the medial amygdala compared with intact animals stressed for a similar period of time. It is concluded that long term stress produces chronic Fos-LI in the adrenal medulla and that adreno-medullectomy increases the Fos response of the PVN, supraoptic nucleus and medial amygdala to long term stress.     

Plasticity of the human auditory cortex induced by discrimination learning of non-native,mora-timed contrasts of the Japanese language

In this magnetoencephalographic (MEG) study, we examined with high temporal resolution the traces of learning in the speech-dominant left-hemispheric auditory cortex as a function of newly trained mora-timing. In Japanese, the “mora” is a temporal unit that divides words into almost isochronous segments (e.g., na-ka-mu-ra and to-o-kyo-o each comprises four mora). Changes in the brain responses of a group of German and Japanese subjects to differences in the mora structure of Japanese words were compared. German subjects performed a discrimination training in 10 sessions of 1.5 h each day. They learned to discriminate Japanese pairs of words (in a consonant, anni–ani; and a vowel, kiyo–kyo, condition), where the second word was shortened by one mora in eight steps of 15 msec each. A significant increase in learning performance, as reflected by behavioral measures, was observed, accompanied by a significant increase of the amplitude of the Mismatch Negativity Field (MMF). The German subjects' hit rate for detecting durational deviants increased by up to 35%. Reaction times and MMF latencies decreased significantly across training sessions. Japanese subjects showed a more sensitive MMF to smaller differences. Thus, even in young adults, perceptual learning of non-native mora-timing occurs rapidly and deeply. The enhanced behavioral and neurophysiological sensitivity found after training indicates a strong relationship between learning and (plastic) changes in the cortical substrate.     

The generalization of deferred imitation in enculturated chimpanzees (Pan troglodytes)

Deferred imitation of object-related actions and generalization of imitation to similar but not identical tasks was assessed in three human-reared (enculturated) chimpanzees, ranging in age from 5 to 9 years. Each ape displayed high levels of deferred imitation and only slightly lower levels of generalization of imitation. The youngest two chimpanzees were more apt to generalize the model's actions when they had displayed portions of the target behaviors at baseline, consistent with the idea that learning is more likely to occur when working within the "zone of proximal development." We argue that generalization of imitation is the best evidence to date of imitative learning in chimpanzees. Electronic Publication     

Color discrimination under chronic hypoxic conditions (simulated climb "Everest-Comex 97")

Hypoxia is known to alter visual functions. In the present study, the effects of chronic hypobaric hypoxia upon visual color discrimination were studied in 8 subjects participating in a simulated climb from sea level (PO2 = 210 hPa) to 8,848 m (PO2 = 70 hPa) over a 31-day period of confinement in a decompression chamber ('Everst-Comex 97'). During these investigations, the subjects were required to discriminate between colors of different hue in the red, blue, and green ranges. Alterations in color discrimination increased slightly but significantly as altitude increased. Impairments occurred mainly in the red and blue ranges. In addition, our results further indicate that color discrimination would be affected only when a minimum threshold of difference between color stimuli is not present. Methodological and physiological implications are discussed.     

The perceived position of the hand in space

This paper reports a series of experiments of the perceived position of the hand in egocentric space. The experiments focused on the bias in the proprioceptively perceived position of the hand at a series of locations spanning the midline from left to right. Perceived position was tested in a matching paradigm, in which subjects indicated the perceived position of a target, which could have been either a visual stimulus or their own fingertip, by placing the index finger of the other hand in the corresponding location on the other side of a fixed surface. Both the constant error, or bias, and the variable error, or consistency of matching attempts, were measured. Experiment 1 showed that (1) there is a far-left advantage in matching tasks, such that errors in perceived position are significantly lower in extreme-left positions than in extreme-right positions, and (2) there is a strong hand-bias effect in the absence of vision, such that the perceived positions of the left and right index fingertips held in the same actual target position in fact differ significantly. Experiments 2 and 3 demonstrated that this hand-bias effect is genuinely due to errors in the perceived position of the matched hand, and not to the attempt at matching it with the other hand. These results suggest that there is no unifying representation of egocentric, proprioceptive space. Rather, separate representations appear to be maintained for each effector. The bias of these representations may reflect the motor function of that effector.     

Direction of human motor responses by men and women to aversive stimulation

The frequency of extensions and flexions of the arms of 12 men and 12 women (ages 20-30 years) responding to a neutral tone or to an electric shock was recorded. Subjects had to choose between pushing or pulling a lever upon receipt of an acoustic signal which was paired or unpaired with an electric shock. They were instructed to perform either long duration movements, allowing for on-line control of the execution, or short duration movements with prior specification of amplitude. Regardless of duration of movements, the aversive signal increased the frequency of extensions and intraindividual variability of choices of the men but decreased the frequency of extensions and intraindividual variability of choices of the women. These findings show that stimuli such as pain or fear automatically elicit patterns of terminal motor states corresponding to fight or flight, initiating processes of preparation of spatially oriented movements which are automatic and sex-typed and impair the use of the terminal cues for simultaneous preprogrammed voluntary movements.     

Comparative analysis of different correction methods for measuring Rod-and-Frame Test performance

A comparative analysis was conducted of five different methods for scoring the Rod-and-Frame Test to examine the convergent validities of each of the five methods with performance on the Embedded Figures Test for a sample of 408 13- to 16-yr.-olds. The scoring methods included the absolute error, the algebraic error, the absolute value of the algebraic error, the frame effect, and an assessment of relative field dependence. Correlations obtained among the five methods and the Embedded Figures Test indicated different patterns for boys and girls. In general, the method which employed the absolute value of the algebraic error yielded the strongest convergent validity coefficients with scores on the Embedded Figures Test and Group Embedded Figures Test for boys (.62 and -.54, respectively), although, for girls, the absolute algebraic error and absolute error both yielded coefficients of .50 with Embedded Figures Test scores and -.46 with Group Embedded Figures Test scores.     

An outcome survey of psychology residency training program graduates of the University of Texas Houston Medical School

A survey of 71 graduates of the psychology residency program at The University of Texas Houston Medical School and the Texas Research Institute of Mental Science indicated that two-thirds of the respondents were involved in private practice, conducting primarily individual therapy, with assessment also playing a major role in their practice. Managed care had the effect of placing limits on the numbers of sessions available to patients, reducing income, and increasing paperwork associated with practice. Implications for training during residency are that individual therapy, using focused short-term approaches, and assessment should continue to be the primary clinical experiences for trainees, and that there should also be training in the business aspect of practice, including marketing.