Assessing a microswitch-based stimulation procedure for eye-blinking responses in a young woman with profound multiple disabilities

We applied a new microswitch-based stimulation procedure for eye-blinking responses with a young woman with profound multiple disabilities, and compared effects of this procedure on the eye-blinking responses and smiling with the effects of a caregiver-based stimulation condition. Analysis showed that the microswitch-based stimulation procedure, with stimulation occurring contingent on eye-blinking responses, increased the frequencies of these responses significantly above the levels recorded in baseline and caregiver-based stimulation conditions. No changes in smiling frequencies occurred. Implications of the findings in terms of alertness, learning, and quality of life are discussed.     

Information along contours and object boundaries

F. Attneave (1954) famously suggested that information along visual contours is concentrated in regions of high magnitude of curvature, rather than being distributed uniformly along the contour. Here the authors give a formal derivation of this claim, yielding an exact expression for information, in C. Shannon's (1948) sense, as a function of contour curvature. Moreover, they extend Attneave's claim to incorporate the role of sign of curvature, not just magnitude of curvature. In particular, the authors show that for closed contours, such as object boundaries, segments of negative curvature (i.e., concave segments) literally carry greater information than do corresponding regions of positive curvature (i.e., convex segments). The psychological validity of this informational analysis is supported by a host of empirical findings demonstrating the asymmetric way in which the visual system treats regions of positive and negative curvature.     

Microswitch programs for persons with multiple disabilities: an overview of the responses adopted for microswitch activation

Background: To introduce a person with multiple disabilities to a microswitch-aided program, one has to select a plausible response(s), that is, a response(s) that can be performed reliably and without excessive effort by the person and can successfully activate the microswitch(es) available (producing preferred stimuli). This paper provides an overview of the responses adopted for microswitch activation in research studies during the last 20 years. Method: Computerized and manual searches were carried out to identify the studies published between 1986 and 2005. Forty-eight research studies were identified. They concerned the use of (1) a single (typical) response, (2) a single (non-typical) response, (3) multiple (typical and non-typical) responses, and (4) multiple (vocal) responses. Results and discussion: The results showed that 151 of the 190 participants involved in the studies had a positive outcome (i.e., clear increases in their responding, which suggested that they had learned the association between responding and consequent preferred stimuli). Failures were largely concentrated in the first group of studies. The discussion focused on (a) the importance of selecting plausible responses for increasing the chances of success, (b) the need of non-typical responses for persons with minimal motor behavior, (c) implications of programs with multiple responses on engagement and choice, and (d) relevance of using vocal utterances. Some suggestions for future research concerning these points were also examined.     

NR2B downregulation in a forebrain region required for avian vocal learning is not sufficient to close the sensitive period for song learning

The neural changes that limit the sensitive period for avian song development are unknown, but neurons in a forebrain region critical for song learning, the lMAN, exhibit experience-driven changes in NMDAR subunit expression that could regulate sensitive period closure. Specifically, NR2B levels in lMAN decrease during song acquisition, potentially reducing synaptic plasticity by decreasing NMDAR EPSC duration and/or affecting NMDAR-coupled intracellular cascades. While rearing birds in isolation extends the sensitive period and also delays the developmental changes in NR2B expression and NMDAR physiology, recent work indicates that a transition to faster NMDAR currents does not preclude further song learning. However, NR2B mRNA expression in isolates remains elevated beyond the age at which NMDAR currents shorten, leaving open the possibility that NR2B levels regulate closure of the sensitive period through effects other than those mediated by NMDAR current duration. To determine whether the experience-driven decrease in NR2B expression in lMAN closes the sensitive period, we promoted this change in gene expression either by treating isolation-reared zebra finches briefly with testosterone (T-isolates) or by allowing males limited access to conspecific song (pre-exposed isolates). We then assessed if these birds could acquire song from tutors after the normal close of the sensitive period. Despite a normal decline in NR2B expression, T-isolate and pre-exposed isolate birds learned tutor songs heard from d65-90, while normally reared birds did not. These findings suggest that the normal decline in NR2B expression with lMAN is not sufficient for sensitive period closure.     

Parsing silhouettes: the short-cut rule.

Many researchers have proposed that, for the purpose of recognition, human vision parses shapes into component parts. Precisely how is not yet known. The minima rule for silhouettes (Hoffman & Richards, 1984) defines boundary points at which to parse but does not tell how to use these points to cut silhouettes and, therefore, does not tell what the parts are. In this paper, we propose the short-cut rule, which states that, other things being equal, human vision prefers to use the shortest possible cuts to parse silhouettes. We motivate this rule, and the well-known Petter's rule for modal completion, by the principle of transversality. We present five psychophysical experiments that test the short-cut rule, show that it successfully predicts part cuts that connect boundary points given by the minima rule, and show that it can also create new boundary points.     

Psychological Distress and Symptoms of Posttraumatic Stress Disorder in Jewish Adolescents Following a Brief Exposure to Concentration Camps

We investigated the psychological impact of an organized visit to Polish concentration camps on Jewish-American adolescents. Eighty-seven adolescents who participated in a B'nai B'rith memorial visit to concentration camps in Poland completed measures of general psychological adjustment and posttraumatic stress disorder (PTSD) at four time-points: pretest, posttest, 6-month follow-up and 12-month follow-up. Measures included the SCL-90-R, the Mississippi Scale for PTSD, and the Impact of Events Scale (IES) for PTSD. On the SCL-90-R, changes in somatization, interpersonal sensitivity, obsessive-compulsive tendencies, depression, anxiety, and phobic anxiety were observed over time, with peak symptom scores at posttest and 6-month follow-up. Scores on the Mississippi Scale for PTSD and the IES Intrusion subscale also increased at 6-months. Predictors of PTSD symptoms on the Mississippi Scale included previous psychiatric treatment and SCL-90-R symptoms of paranoia, depression, and psychosis. Elevated psychotic symptoms on the SCL-90-R predicted PTSD symptoms on the IES. Jewish adolescents with preexisting symptoms of generalized distress or psychoticism appeared at increased risk for PTSD symptoms following exposure to Holocaust stimuli. This study contributes a prospective, multi-measure assessment of trauma reactions in adolescents.     

Parsing silhouettes: The short-cut rule

Many researchers have proposed that, for the purpose of recognition, human vision parses shapes into component parts. Precisely how is not yet known. The minima rule for silhouettes (Hoffman & Richards, 1984) defines boundary points at which to parse but does not tell how to use these points to cut silhouettes and, therefore, does not tell what the parts are. In this paper, we propose the short-cut rule, which states that, other things being equal, human vision prefers to use the shortest possible cuts to parse silhouettes. We motivate this rule, and the well-known Petter’s rule for modal completion, by the principle of transversality. We present five psychophysical experiments that test the short-cut rule, show that it successfully predicts part cuts that connect boundary points given by the minima rule, and show that it can also create new boundary points.