Undergraduate Research Symposium Abstracts from Psychology 2007

Theory of Mind Development and Language Acquisition in Preschoolers
A Comparison of Word Learning and False Belief Tasks
Carlyn Friedberg, Matthew Cohen, and Anna Papafragou
Department of Psychology

Theory of Mind (ToM) is a cognitive ability that allows an individual to form representations of others’ mental states independent of one’s own realities or beliefs. Previous research has shown that by four years old, children ascribe false beliefs to others during explicit ToM tasks that involve prediction of actors’ actions or thoughts. However, around age two, children use ToM more implicitly during word learning, which requires the ability to recognize and comprehend adult intentions. This project aims to examine the role of language acquisition in ToM development. Modeled after Happé and Loth (2002) who showed that children tracked false belief significantly better during a word learning task than during the standard task, the current study compares a standard false scenario to an identical scenario with a word learning component. In the standard false belief task, children are asked to make a prediction about what a character thinks is inside of a box, after the contents have been switched during the character’s absence. In the word learning task, the character names the object in the box and the child must chose the intended target object. True belief tasks were included as control items. Results show that children did not perform significantly better on word learning tasks. Interpretations of this outcome are discussed.

Differential Effects of MK-801 Dosage on Trace and Delay Eyeblink Conditioning
Felipe L. Schiffino, Michael A. Burman & Mark E. Stanton
Department of Psychology

Classical conditioning of the eyeblink response in which the conditioned stimulus (CS) and unconditioned stimulus (US) overlap (termed delay conditioning) requires a well-defined cerebellar-brainstem circuit. Insertion of a blank interval between CS offset and US onset (termed trace conditioning) also recruits forebrain structures such as the hippocampus and medial prefrontal cortex in addition to the cerebellar circuit. MK-801 is a commonly used NMDA-type glutamate receptor antagonist and has been suggested to particularly impair tasks which depend upon the intact hippocampus. Although many previous studies demonstrate differential impairment between trace and delay conditioning procedures; there is some evidence that delay conditioning is also disrupted by systemic NMDA receptor antagonism. In order to clarify whether these tasks are differentially sensitive to the effects of MK-801, multiple doses were administered (Saline, 0.03 mg/kg, 0.1 mg/kg). CR percentage showed significant and equivalent decreases across doses in trace conditioning, while only the highest dose of MK-801 impaired delay conditioning across all sessions. Implications of the differential effects of MK-801 dosage on the two paradigms are discussed. Funding was provided by University of Delaware Science and Engineering Scholar Program.

Neonatal one-day binge-like ethanol exposure results in the loss of neurons
in the CA1 subfield of the adult rat hippocampus.
Courtney E. Schnell, R. M. A. Napper., Anna Klintsova
Department of Psychology

It has been demonstrated in the animal model that exposure to ethanol during brain development can permanently alter brain structure and produce functional impairments in many aspects of behavior, including deficits in learning and memory. Cell loss in the hippocampus may contribute to those deficits. Current studies utilize multiple ethanol exposures to achieve significant intoxication of rat pups across several days of development. In contrast, this report uses a one-day alcohol exposure on postnatal day four (PD4). A previous study (Napper and Klintsova, 2007) indicates that this type of single binge exposure, although resulting in significant and immediate apoptosis, does not inhibit spatial learning in rats when training occurs during adolescence. We are analyzing the CA1 hippocampal region of the alcohol-exposed (AE) rats in comparison with relevant controls to determine the effect of one-day ethanol binge exposure on CA1 neuron number. On PD4, Long Evans male and female rat pups received intubations of milk-ethanol formula (4.5g/kg/day of ethanol in two feeds two hours apart). On PD50, animals were anesthetized and transcardially perfused. The total number of neurons in the CA1 hippocampal region was estimated using unbiased stereology. Preliminary data indicates that there is a negative correlation between the blood alcohol concentration measured on PD4 after the second AE intubation and the CA1 neuron count on PD50 (r = - .45). In addition, the number of CA1 neurons is significantly lower in AE rats in comparison with the suckle controls (p=0.027). Estimation of CA1 neurons in sham-intubated animals is under way. This data indicates that even a one-day binge during the developmental period may cause the permanent damage to certain areas of the brain. Funding for this project was provided by the William Evans Visiting Fellowship (University of Otago, New Zealand) and the Science and Engineering Scholarship.

Assessing the validity of prospective and retrospective measures of attachment disruptions
Aundrea Wilkins, Roger Kobak, & Clare Smith
Department of Psychology

This study examines the validity of two types of measures of attachment disruptions in children’s relationships with their primary caregivers. Prospective (beginning at age 4) and retrospective (at age 15) measures were collected in a sample of 113 economically disadvantaged families in New Castle County. Prospective measures were derived from demographic interviews with the child’s primary caregiver when the children were 6-, 13- and 15-years old. Early attachment disruptions were defined as physical separations from the primary caregiver resulting from the child going to live with another caregiver, or, if the child returned to the primary caregiver prior to age 4. Later attachment disruptions were defined as a change in who acted as the child’s primary caregiver that occurred between ages 6 and 13. Retrospective measures consisted of coded teens’ responses during the Adult Attachment Interviews (AAI) administered at age 15. The AAI, a semi-structured interview, asks several questions about the child’s relationships with their parents, beginning with their earliest memories. Disruptions were defined as one of eleven physical separations that were disruptive in nature such that the child might find it difficult or impossible to get to the attachment figure if the child had a need. Disruptions for both measures were scored on a 0/1 scale. The convergence of prospective caregiver reports and retrospective measures based on adolescents’ memories was examined. Both of caregivers prospective reports of early and later disruptions contributed significance variance to adolescents’ retrospective reports of disruptions with their biological mothers. NIMH RO1-MH59867, Attachment and Risk in Early Adolescence.