Rapid categorization of foveal and extrafoveal natural images: associated ERPs and effects of lateralization

Humans are fast and accurate at performing an animal categorization task with natural photographs briefly flashed centrally. Here, this central categorization task is compared to a three position task in which photographs could appear randomly either centrally, or at 3.6 degrees eccentricity (right or left) of the fixation point. A mild behavioral impairment was found with peripheral stimuli with no evidence in support of hemispheric superiority; but enlarging the window of spatial attention to three possible stimuli locations had no behavioral cost on the processing of central images. Performance in the central categorization task has been associated with a large difference between the potentials evoked to target and non-target correct trials, starting about 150 ms after stimulus onset on frontal sites. Present results show that this activity originates within extrastriate visual cortices and probably reflects perceptual stimuli differences processed within areas involved in object recognition. Latencies, slopes, and peak amplitudes of this differential activity were invariant to stimulus position and attentional load. Stimulus location uncertainty and lateralization did not affect speed of visual processing.     

A state of anarchy and a call to arms: The research and treatment of post-traumatic stress disorder

Despite rapid growth and high visibility since the publication of DSM III, the research and treatment of post-traumatic stress disorder have generally been characterized by confusion and a failure to generalize from or to build on earlier findings and clinical experience. Several structural, psychological, and political reasons why this particular field is fraught with such confusion are discussed.     

Spotting animals in natural scenes: efficiency of humans and monkeys at very low contrasts

The ability of monkeys to categorize objects in visual stimuli such as natural scenes might rely on sets of low-level visual cues without any underlying conceptual abilities. Using a go/no-go rapid animal/non-animal categorization task with briefly flashed achromatic natural scenes, we show that both human and monkey performance is very robust to large variations of stimulus luminance and contrast. When mean luminance was increased or decreased by 25–50%, accuracy and speed impairments were small. The largest impairment was found at the highest luminance value with monkeys being mainly impaired in accuracy (drop of 6% correct vs. <1.5% in humans), whereas humans were mainly impaired in reaction time (20 ms increase in median reaction time vs. 4 ms in monkeys). Contrast reductions induced a large deterioration of image definition, but performance was again remarkably robust. Subjects scored well above chance level, even when the contrast was only 12% of the original photographs (≈81% correct in monkeys; ≈79% correct in humans). Accuracy decreased with contrast reduction but only reached chance level -in both species- for the most extreme condition, when only 3% of the original contrast remained. A progressive reaction time increase was observed that reached 72 ms in monkeys and 66 ms in humans. These results demonstrate the remarkable robustness of the primate visual system in processing objects in natural scenes with large random variations in luminance and contrast. They illustrate the similarity with which performance is impaired in monkeys and humans with such stimulus manipulations. They finally show that in an animal categorization task, the performance of both monkeys and humans is largely independent of cues relying on global luminance or the fine definition of stimuli.     

Effects of motor action on affective preferences in autism spectrum disorders: different influences of embodiment

In the embodied cognition framework, sensory, motor and emotional experiences are encoded along with sensorimotor cues from the context in which information was acquired. As such, representations retain an initial imprint of the manner in which information was acquired. The current study reports results indicating a lack of embodiment effects in ASD and, further, an association between embodiment differences and ASD symptomatology. The current results are consistent with an embodied account of ASD that goes beyond social experiences and could be driven by subtle deficits in sensorimotor coordination.     

Genre et performance scolaire en milieu minoritaire au Quebec. Les élèves originaires d’Afrique subsaharienne

This article analyzes the differences in academic performance due to gender within the minority group from Sub-Saharan Africa. Using the statistical data from Quebec’s Ministry of Education on the June 1996, 1999 and 2000 standardized tests, the 1996 census data on the education level of the primary ethnocultural groups in Quebec and interviews, the article shows that girls perform better than boys in this group in Quebec. The higher academic results achieved by the girls and the fact that the boys are falling back is not however a continuum, it is the result of identity shift. Devalued and disadvantaged in their countries of origin, the academic performance of girls is low compared to that of boys in the same conditions. Emancipated in Quebec, the transition is remarkable in the Quebec school system: they have the upper hand on the boys in this academic environment side by side. That success is incumbent on an identity shift upon contact with a universe that is based on the principle of equality under the law with its derivatives: equality of opportunities, dignity, etc. One might say that the performance of each is attributable to the identity path in which socialization and gender referents play a significant role. Among the boys, the splintered male referent gives rise to fragmented identity paths, while the consistent and inclusive female referent generates a common and motivating female model.     

Genetic differences in the mouse defense test battery

The mouse defense test battery (MDTB) has been designed to examine anxiogenic- or anxiolytic-like properties of psychoactive drugs through effects on specific defensive behaviors. In the present study, the MDTB was used to evaluate the potential contribution of genetic factors to these behaviors. The data revealed pronounced differences in several defense reactions among four inbred strains (BALB/c, C57BL/6, CBA, DBA/2) and one outbred (Swiss) mouse line. Thus, when subjects were introduced into the apparatus, Swiss and C57BL/6 displayed the highest levels of horizontal and vertical activities, while BALB/c and DBA/2 mice showed intermediate and CBA low activity rates. When subjects were chased by the rat, C57BL/6 mice used flight as the dominant defense strategy, while the defensive responses of BALB/c, C57BL/6, and DBA/2 mice consisted of flight reactions and risk assessment activities. However, when flight or escape was not possible, risk assessment became the predominant feature of the defense repertoire in the C57BL/6 mice. When defensive threat/attack behaviors were required, Swiss, BALB/c, DBA/2, and C57BL/6 mice showed very similar reactions in terms of the magnitude of the responses observed. CBA mice were poorly defensive in all these test situations. Finally, after the rat was removed from the test apparatus, Swiss, DBA/2, and C57BL/6 mice displayed more vertical activities than BALB/c mice. These latter, however, showed an increased level of ambulation compared to the activity recorded before the rat exposure. Together, these findings indicate that genetic factors contribute to defensive behaviors in this animal model of anxiety. The different behavioral profiles displayed by the strains used here may provide the means to obtain a better insight into the neurobehavioral mechanisms involved in anxiety-related disorders. Aggr. Behav. 23:19–31, 1997. © 1997 Wiley-Liss, Inc.     

Moving along the number line: operational momentum in nonsymbolic arithmetic

Can human adults perform arithmetic operations with large approximate numbers, and what effect, if any, does an internal spatial-numerical representation of numerical magnitude have on their responses? We conducted a psychophysical study in which subjects viewed several hundred short videos of sets of objects being added or subtracted from one another and judged whether the final numerosity was correct or incorrect. Over a wide range of possible outcomes, the subjects' responses peaked at the approximate location of the true numerical outcome and gradually tapered off as a function of the ratio of the true and proposed outcomes (Weber's law). Furthermore, an operational momentum effect was observed, whereby addition problems were overestimated and subtraction problems were underestimated. The results show that approximate arithmetic operates according to precise quantitative rules, perhaps analogous to those characterizing movement on an internal continuum.     

Two-year-olds compute syntactic structure on-line

Syntax allows human beings to build an infinite number of new sentences from a finite stock of words. Because toddlers typically utter only one or two words at a time, they have been thought to have no syntax. Using event-related potentials (ERPs), we demonstrated that 2-year-olds do compute syntactic structure when listening to spoken sentences. We observed an early left-lateralized brain response when an expected verb was incorrectly replaced by a noun (or vice versa). Thus, toddlers build on-line expectations as to the syntactic category of the next word in a sentence. In addition, the response topography was different for nouns and verbs, suggesting that different neural networks already underlie noun and verb processing in toddlers, as they do in adults.     

Reports from the Front: The Effects of Hurricane Katrina on Mental Health Professionals in New Orleans

Hurricane Katrina created an unprecedented mental health crisis in New Orleans. Once they could return to work, local mental health professionals attempted to treat survivors of the storm while dealing with the storm's impact on themselves. Those working in public settings were offered in-service training and supervision. But clinicians in private practice often found themselves bearing the brunt of posttraumatic uncertainty alone. The current paper includes four experiential reports from area clinicians describing their early struggles to maintain a sense of continuity in their ongoing clinical work, only to realize how much of the personal is also professional in the aftermath of a disaster of this magnitude, and how personal and professional inevitably inform one another when clinicians and patients survived similar dangers and losses. The introduction locates these four papers in the larger context of post-Katrina New Orleans and a program that was specifically tailored to meet the needs of local clinicians. This program demonstrated the ways in which psychoanalytic ideas can be used to give meaning to a traumatized mental health community's profound disorientation.     

Development of a view-invariant representation of the human head

Do infants perceive visual cues as diverse as frontal-view faces, profiles or bodies as being different aspects of the same object, a fellow human? If that is the case, visual exposure to one such cue should facilitate the subsequent processing of the others. To verify this hypothesis, we recorded event-related responses in 4-month-old infants and in adults. Pictures of eyes were interleaved amongst images belonging to three human contexts (frontal-view faces, profiles or bodies) or non-human contexts (houses, cars or pliers). In adults, both profile and frontal-face contexts elicited suppression of the N170 response to eye pictures, indicating an access to a view-invariant representation of faces. In infants, a response suppression of the N290 component was recorded only in the context of frontal faces, while profile context induces a different effect (i.e., a P400 enhancement) on eye processing. This dissociation suggests that the view-invariant representation of faces is learned, as it is for other 3-D objects and needs more than 4 months of exposure to be established. In a follow-up study, where infants were exposed to a short movie showing people rotating their heads, the profile-induced P400 effect was speeded up, indicating that exposure to successive views of the same object is probably a way to build up adult-like face representations.