Inhibition of the LH Surge by Restraint Stress in Cyclic Rats: Studies on the Role of GABAA and GABAB Receptors

There is evidence that stress can alter the activity in the brain of gamma-aminobutyricacid (GABA), a neurotransmitter that has been implicated in the regulation of LH secretion. In the present study the role of GABA in the restraint stress-induced inhibition of the LH surge was investigated in the intact cyclic rat. Intracerebroventricular (icv) administration of the GABAA receptor agonist muscimol (0.1, 0.5 or 1 μg) 5 min before the presumed onset of the pro-oestrous LH surge (at 0900 h) caused a dose dependent suppression of the surge. A single dose of the GABAB receptor agonist baclofen (1 μg; icv) injected at 0855 h postponed the onset of the LH surge, and repeated injections at 0855 and 1130 h suppressed the surge. These data indicate that GABA-ergic activity in the brain can inhibit the LH surge in the cyclic rat via GABAA and GABAB receptors. Pro-oestrous rats were subjected to 5 hrs of restraint starting at 0855 h. Pretreatment with the GABAA receptor antagonist bicuculine (1 μg; icv) at 0840, 0940 and 1040 h or pretreatment with the GABAB receptor antagonist phaclofen (10 μg; icv) at 0840 h were ineffective in preventing the restraint-induced inhibition of the LH surge. The results suggest that GABAA and GABAB receptors are not involved in the inhibitory effect of restraint stress on the LH surge.     

The role of attention in subitizing

The process of rapidly and accurately enumerating small numbers of items without counting, i.e. subitizing, is often believed to rest on parallel preattentive processes. However, the possibility that enumeration of small numbers of items would also require attentional processes has remained an open question. The present study is the first that directly contrasts the preattentive and attentive models of subitizing. We used an inattentional blindness paradigm to manipulate the availability of attentional resources during enumeration. In the inattention condition, the items to be enumerated were presented unexpectedly while participants focused on a line length comparison task. Divided- and full-attention conditions were also included. The results showed that only numbers one and two could be enumerated when the effects of attention were minimized. Freeing attentional resources increased the enumeration accuracies considerably, including for number two. The results suggest that even for enumerating small numbers, the attentional demands increase as the number of objects increases.     

The eyes know: eye movements as a veridical index of memory

In two experiments, we examined whether observers' eye movements distinguish studied faces from highly similar novel faces. Participants' eye movements were monitored while they viewed three-face displays. Target-present displays contained a studied face and two morphed faces that were visually similar to it; target-absent displays contained three morphed faces that were visually similar to a studied, but not tested, face. On each trial in a test session, participants were instructed to choose the studied face if it was present or a random face if it was not and then to indicate whether the chosen face was studied. Whereas manipulating visual similarity in target-absent displays influenced the rate of false endorsements of nonstudied items as studied, eye movements proved impervious to this manipulation. Studied faces were viewed disproportionately from 1,000 to 2,000 ms after display onset and from 1,000 to 500 ms before explicit identification. Early viewing also distinguished studied faces from faces incorrectly endorsed as studied. Our findings show that eye movements provide a relatively pure index of past experience that is uninfluenced by explicit response strategies, and suggest that eye movement measures may be of practical use in applied settings.     

Spontaneous focusing on numerosity as a domain-specific predictor of arithmetical skills

The aim of this 2 year longitudinal study was to explore whether children’s individual differences in spontaneous focusing on numerosity (SFON) in kindergarten predict arithmetical and reading skills 2 years later in school. Moreover, we investigated whether the positive relationship between SFON and mathematical skills is explained by children’s individual differences in spontaneous focusing on a non-numerical aspect. The participants were 139 Finnish-speaking children. The results show that SFON tendency in kindergarten is a significant domain-specific predictor of arithmetical skills, but not reading skills, assessed at the end of Grade 2. In addition, the relationship between SFON and number sequence skills in kindergarten is not explained by children’s individual differences in their focusing on a non-numerical aspect that is, spatial locations.     

Distinguishing highly confident accurate and inaccurate memory: insights about relevant and irrelevant influences on memory confidence

It is generally believed that accuracy and confidence in one's memory are related, but there are many instances when they diverge. Accordingly it is important to disentangle the factors that contribute to memory accuracy and confidence, especially those factors that contribute to confidence, but not accuracy. We used eye movements to separately measure fluent cue processing, the target recognition experience, and relative evidence assessment on recognition confidence and accuracy. Eye movements were monitored during a face-scene associative recognition task, in which participants first saw a scene cue, followed by a forced-choice recognition test for the associated face, with confidence ratings. Eye movement indices of the target recognition experience were largely indicative of accuracy, and showed a relationship to confidence for accurate decisions. In contrast, eye movements during the scene cue raised the possibility that more fluent cue processing was related to higher confidence for both accurate and inaccurate recognition decisions. In a second experiment we manipulated cue familiarity, and therefore cue fluency. Participants showed higher confidence for cue-target associations for when the cue was more familiar, especially for incorrect responses. These results suggest that over-reliance on cue familiarity and under-reliance on the target recognition experience may lead to erroneous confidence.     

How self‐relevant imagination affects memory for behaviour

Research has demonstrated that imagination can be used to affect behaviour and also to distort memory, yet few studies have examined whether the effects of imagination on behavioural estimates and memory are related. In two experiments, the effects of imagination on self‐reported behaviour and subsequent memory for that behaviour were investigated. A comparison of behavioural estimates collected before and after imagination demonstrated that reported estimates of behaviour changed after imagination. In addition, memory for the original estimates of behaviour was also affected, suggesting that imagination may impair one's ability to remember originally reported behaviour. Experiment 2 demonstrated that the observed changes in reported behaviour were accompanied by the largest errors in memory for originally reported behaviour when participants generate images based on self‐relevant scenarios. On the other hand, memory distortion was minimized when participants read but did not imagine self‐relevant scenarios. These results have direct application to clinicians and researchers who employ imagination techniques as behavioural modifiers, and suggest that techniques that are self‐relevant but do not include imagery may be a useful alternative to imagination. Copyright © 2006 John Wiley & Sons, Ltd.     

The obligatory effects of memory on eye movements

Previous work has shown that eye movement behaviour is affected by previous experience, such that alterations in viewing patterns can be observed to previously viewed compared to novel displays. The current work addresses the extent to which such effects of memory on eye movement behaviour are obligatory; that is, we examined whether prior experience could alter subsequent eye movement behaviour under a variety of testing conditions, for stimuli that varied on the nature of the prior exposure. While task demands influenced whether viewing was predominantly directed to the novel versus familiar faces, viewing of the familiar faces was distinguished from viewing of the novel faces, regardless of whether the task required incidental encoding or intentional retrieval. Changes in scanning of previously viewed over novel faces emerged early in viewing; in particular, viewing duration of the first fixation to the familiar faces was often significantly different from the duration of the first fixation directed to the novel faces, regardless of whether prior exposure was solely in the context of the experiment or due to real-world exposure. These findings suggest that representations maintained in memory may be retrieved and compared with presented information obligatorily.     

The obligatory effects of memory on eye movements

Previous work has shown that eye movement behaviour is affected by previous experience, such that alterations in viewing patterns can be observed to previously viewed compared to novel displays. The current work addresses the extent to which such effects of memory on eye movement behaviour are obligatory; that is, we examined whether prior experience could alter subsequent eye movement behaviour under a variety of testing conditions, for stimuli that varied on the nature of the prior exposure. While task demands influenced whether viewing was predominantly directed to the novel versus familiar faces, viewing of the familiar faces was distinguished from viewing of the novel faces, regardless of whether the task required incidental encoding or intentional retrieval. Changes in scanning of previously viewed over novel faces emerged early in viewing; in particular, viewing duration of the first fixation to the familiar faces was often significantly different from the duration of the first fixation directed to the novel faces, regardless of whether prior exposure was solely in the context of the experiment or due to real-world exposure. These findings suggest that representations maintained in memory may be retrieved and compared with presented information obligatorily.