Look over there! Unilateral gaze increases geographical memory of the 50 United States

Based on their specialized processing abilities, the left and right hemispheres of the brain may not contribute equally to recall of general world knowledge. US college students recalled the verbal names and spatial locations of the 50 US states while sustaining leftward or rightward unilateral gaze, a procedure that selectively activates the contralateral hemisphere. Compared to a no-unilateral gaze control, right gaze/left hemisphere activation resulted in better recall, demonstrating left hemisphere superiority in recall of general world knowledge and offering equivocal support for the hemispheric encoding asymmetry model of memory. Unilateral gaze- regardless of direction- improved recall of spatial, but not verbal, information. Future research could investigate the conditions under which unilateral gaze increases recall. Sustained unilateral gaze can be used as a simple, inexpensive, means for testing theories of hemispheric specialization of cognitive functions. Results support an overall deficit in US geographical knowledge in undergraduate college students.     

Superior episodic memory in inconsistent-handers: a replication and extension using fNIRS

A large body of evidence supports the existence of a robust handedness difference in episodic memory retrieval, with inconsistent-handedness being associated with superior memory across a wide variety of paradigms, including superior retrieval of lab-based and real world memories. Despite superior episidoc memory in inconsistent-handers, and despite neuroanatomical and neurophysiological differences in cortical regions between inconsistent- and consistent-handers, we are aware of no studies to date that have examined physiological activity in the brains of inconsistent- versus consistent-handers while engaged in memory tasks. The purpose of this paper, therefore, is to present a first look at this issue, using functional near-infrared spectroscopy (fNIRS) as a simple, non-invasive measure of frontal lobe activity during encoding and recall of list words in inconsistent- and consistent-handers. Behaviourally, we replicated prior studies, finding a significant inconsistent-handed advantage in free recall. Using fNIRS-derived oxygenated haemoglobin (O₂Hb) as a measure of frontal lobe activity, we found the first evidence for handedness differences in brain activity that are associated with the handedness differences in episodic retrieval. Specifically, the primary finding was that increased O₂Hb in the right hemisphere during recall was associated with better retrieval, but for consistent-handers only.     

Mixed- versus strong right-handedness is associated with biases towards "remember" versus "know" judgements in recognition memory: role of interhemispheric interaction

Growing evidence supports the hypothesis that episodic versus semantic memories rely primarily on interhemispheric versus intrahemispheric processing, respectively. For example, a recent study found that individuals with presumed greater interhemispheric interaction were superior in episodic recall but inferior at semantic word fragment completion; however, tests of recognition memory yielded no group differences. Interestingly, recognition memory can be based on either explicitly remembering a stimulus or implicitly knowing that a stimulus had been presented. The current experiments administered recognition memory tests to strongly versus mixed handed participants who judged for each recognised item whether their response was based on remembering (episodic memory) or knowing (semantic memory) (Tulving, 1983). Results indicate that strong versus mixed handers are biased towards basing recognition responses on judgements of knowing versus remembering, respectively. As strong versus mixed handedness is associated with greater versus lesser interhemispheric processing, the results support the original hypothesis.     

An assessment of sleep architecture as a function of degree of handedness in college women using a home sleep monitor

The present study examined sleep architecture as a function of handedness in a population of undergraduate college women using a home sleep monitor. Compared to strongly handed individuals, participants with a tendency toward mixed-handedness had a shorter sleep latency and spent a greater percentage of their sleep period asleep and less awake. Increasing mixed-handedness was also associated with increased NREM; strong-handedness was associated with increased REM. Results are placed in a neurophysiological framework wherein corpus callosum mediated differences in interhemispheric interaction during Wake, REM, and NREM on the one hand, and individual differences in corpus callosum morphology and hemispheric communication as a function of handedness on the other, interact to result in handedness differences in sleep architecture.     

Examining Maternal Elaborative Reminiscing as a Protective Factor in the Intergenerational Transmission of Psychopathology

Most research examining the impact of early parental depression on the developing child has focused on the nature of parenting practices observed in depressed adults. Maternal elaborative reminiscing, or the extent to which mothers elaboratively discuss past shared experiences with their children, has a considerable influence on children’s emotional and social development and is understudied within the context of maternal depression. The current study is the first to examine whether maternal elaborative reminiscing in middle childhood mediates the association between exposure to maternal depressive symptoms in infancy and later internalizing and externalizing problems. The study included 206 mother–child dyads recruited from the community who participated in a prospective longitudinal study. Maternal depressive symptoms were assessed when offspring were 6-months old. At 5-years old, dyads were observed during a free play task to measure sensitive and harsh-intrusive parenting and during a reminiscing task to measure maternal elaboration. Teacher-reported internalizing and externalizing problems were collected at age 7. A saturated path model revealed that maternal elaborative reminiscing, but not sensitive or harsh-intrusive parenting, fully mediated the association between maternal depression in infancy and externalizing, but not internalizing, problems. Reduced maternal elaboration during parent–child reminiscing constitutes one way in which risk from early maternal depression is associated with later externalizing problems.

     

Infant and parent factors associated with early maternal sensitivity: a caregiver-attachment systems approach

We examined variations in maternal sensitivity at 6 months of child age as a function of child negativity and maternal physiology. We expected maternal vagal withdrawal in response to infant negative affect to facilitate the maintenance of sensitivity, but only for mothers of securely attached children. One hundred and forty-eight infant-mother dyads were observed in multiple contexts at 6 months of child age, and associations among maternal and child variables were examined with respect to 12-month attachment quality. Mothers of later securely attached children were more sensitive than mothers of avoidant children. However, sensitivity decreased for all mothers at high levels of infant negative affect. Furthermore, for mothers of avoidant children, vagal withdrawal was associated with sensitivity to child distress. No association was found between vagal withdrawal and sensitivity for mothers of securely attached children. This suggests that mothers of avoidant children may be uniquely challenged by the affective demands of their infants.     

The influence of parenting on infant emotionality: A multi-level psychobiological perspective

Infant temperament is theorized to have a strong genetic basis. Yet, studies of the stability of temperament and molecular genetics research on temperament have revealed inconsistent findings. One reason may be because research has not taken into account the influence of early social experiences. We review research on aspects of infant emotionality presumed to be temperamental in origin, emotion reactivity and emotion regulation, and integrate research addressing parenting influences on physiology and genetics of infant emotionality with traditional research on behavioral expression of emotionality. Empirical research supports the theory that sensitive and appropriately responsive parenting in infancy is related to more optimal patterns of behavioral and physiological reactivity and regulation. Molecular genetics research with both animal and human populations has produced consistent results when environmental experiences are taken into account. Findings suggest that the short allele of the serotonin transporter gene and the long allele of the DRD4 dopamine receptor gene may be related to distinct patterns of infant emotionality and to later problems with depression, impulse control problems, and externalizing/antisocial behaviors, primarily when paired with insensitive parenting, abuse or neglect, or other adverse family environments. Future directions and limitations in the field are discussed.     

Increased interhemispheric interaction is associated with decreased false memories in a verbal converging semantic associates paradigm

Recent evidence indicates that task and subject variables that are associated with increased interaction between the left and right cerebral hemispheres result in enhanced performance on tests of episodic memory. The current study looked at the effects of increased interhemispheric interaction on false memories using a verbal converging semantic associates paradigm. In Experiment 1, strong right-handedness (which is associated with decreased interhemispheric interaction) was associated with higher rates of false memories. In Experiment 2, bilateral saccadic eye movements (which are associated with increases in interhemispheric interaction) were associated with fewer false memories. The results provide further support for an interhemispheric basis for episodic/explicit memory.