Eyeblink startle responses in spider phobies before and after treatment: A pilot study

Before and after treatment, acoustic probes eliciting eyeblink startles were presented to 41 female spider phobies during a behavioral approach test (BAT). During this test, subjects pulled a glass jar containing a live spider as nearby as they normally would tolerate. In order to obtain baseline startles, the subjects also carried out a BAT with a basket containing attractive food items. Startle responses were found to be relatively larger during the spider BAT than during the food BAT. This difference in relative magnitude decreased as a result of one-session treatment. The startle response appeared to be relatively independent of other outcome measures (i.e., Spider Questionnaire, BAT, and heart rate). Taken together, the results sustain findings previously reported by Lang and co-workers.     

Responding in configural discrimination problems depends on density of reinforcement in time

Previous research has shown that conditioned responding in differential skin conductance conditioning increased for reinforced stimuli (CSs+) but remained constant for nonreinforced stimuli (CSs-) due to decreasing reinforcement density. The present two experiments (Experiment 1: Negative patterning; Experiment 2: Positive patterning) were designed to disentangle a possible confound of reinforcement density with stimulus frequency. In order to achieve this, we varied the intertrial interval (18 s, 24 s, or 48 s) and held constant the numbers of CSs+ and of CSs- in each of both discrimination problems. With increasing intertrial intervals, we found higher responding both to CSs+ and to CSs- as well as increased response differentiation. We discuss these results with respect to two mechanisms offered by Wagner's SOP model and conclude that the observed effects are due to variations in density of reinforcement in time.     

Children's false memories: easier to elicit for a negative than for a neutral event

The present study examined the role of valence in the development of children's implanted false memories. Seventy-six 7-year-old children listened to two true and one false narrative. The false narrative was either neutral ("moving to another classroom") or emotional negative ("being accused by the teacher for copying off your neighbor"). In addition, half of the children were presented with their class photograph while listening to the narratives. During two interviews, children recalled as many details as possible from the true and false events. Results showed that the negative event elicited more false memories than the neutral event. The presentation of a true photograph did not promote the development of false memories.     

An fMRI study of working memory for schematic facial expressions

Functional magnetic resonance imaging (fMRI) was used to examine neuronal activation in relation to increasing working memory load in an n-back task, using schematic drawings of facial expressions and scrambled drawings of the same facial features as stimuli. The main objective was to investigate whether working memory for drawings of facial features would yield specific activations compared to memory for scrambled drawings based on the same visual features as those making up the face drawings. fMRI-BOLD responses were acquired with a 1.5 T Siemens MR scanner while subjects watched the facial drawings alternated with the scrambled drawings, in a block-design. Subjects had to hold either 1 or 2 items in working memory. We found that the main effect of increasing memory load from one to two items yielded significant activations in a bilaterally distributed cortical network consisting of regions in the occipitotemporal cortex, the inferior parietal lobule, the dorsolateral prefrontal cortex, supplementary motor area and the cerebellum. In addition, we found a memory load x drawings interaction in the right inferior frontal gyrus in favor of the facial drawings. These findings show that working memory is specific for facial features which interact with a general cognitive load component to produce significant activations in prefrontal regions of the brain.     

The Impact of Anxiety on Memory for Details in Spider Phobics

According to the attentional narrowing account of emotional memory, physiological arousal results in attention being directed towards central rather than peripheral characteristics of the situation. Consequently, memory for central details would be relatively good, whereas memory for peripheral information would be impaired. The present experiment sought to test this attentional narrowing hypothesis under highly stressful conditions. Spider phobics and low-fear controls were confronted with a large live spider, eliciting high levels of emotion in the phobic group. Afterwards, subjects' memory for the experimental situation was tested. On a cued recall test, phobics displayed a poor memory for peripheral detail information relative to control subjects. There were no differences between phobics and controls with respect to central detail information. Thus, the present data provide partial support for the attentional narrowing account of emotional memory. © 1997 by John Wiley & Sons, Ltd.     

Survival processing in times of stress

Recent studies have found that processing information according to an evolutionary relevant (i.e., survival) scenario improves its subsequent memorability, potentially as a result of fitness advantages gained in the ancestral past. So far, research has not revealed much about any proximate mechanisms that might underlie this so-called survival processing advantage in memory. Intriguingly, research has shown that the memorability of stressful situations is enhanced via the release of stress hormones acting on brain regions involved in memory. Since survival situations habitually involve some degree of stress, in the present study, we investigated whether stress serves as a proximate mechanism to promote survival processing. Participants rated words for their relevance to either a survival or a neutral (moving) scenario after they had been exposed to a psychosocial stressor or a no-stress control condition. Surprise retention tests immediately following the rating task revealed that survival processing and acute stress independently boosted memory performance. These results therefore suggest that stress does not serve as a proximate mechanism of the survival processing advantage in memory.     

Successive olfactory reversal learning in honeybees

Honeybees Apis mellifera can associate an originally neutral odor with a reinforcement of sucrose solution. Forward pairings of odor and reinforcement enable the odor to release the proboscis extension reflex in consecutive tests. Bees can also be conditioned differentially: They learn to respond to a reinforced odor and not to a nonreinforced one. They can also learn to reverse their choice. Here we ask whether honeybees can learn successive olfactory differential conditioning tasks involving different overlapping pairs of odors. The conditioning schedules were established in order to train the animals with 3, 2, 1, or 0 reversals previous to a last differential conditioning phase in which two additional reversals were present. We studied whether or not successive reversal learning is possible and whether or not learning olfactory discrimination reversals affects the solving of subsequent discrimination reversals. Therefore we compared the responses of bees that had experienced reversals with those of bees that had not experienced such reversals when both are confronted with a new reversal situation. In experiment 1 we showed that bees that had experienced three previous reversals were better in solving the final reversal task than bees with no previous reversal experience. In experiment 2, we showed that one reversal learning is enough for bees to perform better in the final reversal task. The successive different reversals trained in our experiments resemble the natural foraging situation in which a honeybee forager has to switch successively from an initial floral species to different ones. The fact that experiencing such changes seems to improve a bee's performance in dealing with further new exploited food sources has therefore an adaptive impact for the individual and for the colony as a whole.