Leslie A. Burton

Are variations among right-handed individuals in perceptual asymmetries caused by characteristic arousal differences between hemispheres?

We propose that much of the variance among right-handed subjects in perceptual asymmetries on standard behavioral measures of laterality arises from individual differences in characteristic patterns of asymmetric hemispheric arousal. Dextrals with large right-visual-field (RVF) advantages on a tachistoscopic syllable-identification task (assumed to reflect characteristically higher left-hemisphere than right-hemisphere arousal) outperformed those having weak or no visual-field asymmetries (assumed to reflect characteristically higher right-hemisphere than left-hemisphere arousal). The two groups were equal, however, in asymmetries of error patterns that are thought to indicate linguistic or nonlinguistic encoding strategies. For both groups, relations between visual fields in the ability to discriminate the accuracy of performance followed the pattern of syllable identification itself, suggesting that linguistic and metalinguistic processes are based on the same laterally specialized functions. Subjects with strong RVF advantages had a pessimistic bias for rating performance, and those with weak or no asymmetries had an optimistic bias, particularly for the left visual field (LVF). This is concordant with evidence that the arousal level of the right hemisphere is closely related to affective mood. Finally, consistent with the arousal model, leftward asymmetries on a free-vision face-processing task became larger as RVF advantages on the syllable task diminished and as optimistic biases for the LVF, relative to the RVF, increased.

Visual evoked potentials in dyslexics and normals: failure to find a difference in transient or steady-state responses.

We measured transient and steady-state checkerboard contrast-reversal visual evoked potentials (VEPs) in ten dyslexics, five patient controls, and 11 normals over a range of contrasts and luminances. Latency, amplitude, and phase measurements failed to distinguish the responses of dyslexics from those of normals or patient controls. Decreases in luminance or contrast resulted in an increased latency of the transient VEP in all groups, but these changes also did not distinguish the responses of dyslexics from those of the controls. Response variability was similar in dyslexics and normals, but was increased in subjects with attention deficit-hyperactivity disorder (ADHD). Performance on standardized psychometric testing did differentiate the dyslexics from controls, but did not correlate with VEP responses.

Gender differences in relations of mental rotation, verbal fluency, and SAT scores to finger length ratios as hormonal indexes

One hundred thirty-four university students (93 women, 41 men) were administered the Vandenberg Mental Rotation Test and the Thurstone Word Fluency Test, and they were asked to report their Scholastic Achievement Test scores. Finger lengths were measured, because literature has reported gender differences in the ratio of the 2nd to 4th, 2nd to 3rd, and 2nd to 5th finger lengths, such that the ratio is larger in women than in men. The goal of this study was to evaluate the relations between finger-length ratios and cognitive skills, such as spatial skills and verbal fluency, which have shown gender differences and direct relations to hormonal effects. Gender differences were found in the expected directions, such that the men performed better than the women for mental rotation, the women performed better than the men for verbal fluency, and the finger-length ratios were in the directions reported in the literature. The finger-length ratios showed an interesting relation with the cognitive variables for the men and women. For the men, better performance on the measures, including mental rotation, verbal fluency, and verbal Scholastic Achievement Test score was associated with less of a male-typical finger-length ratio pattern, or higher ratios. For the women, better performance for mental rotation and verbal fluency was associated with less of a female-typical finger-length ratio pattern, or lower ratios. Thus, in this group of college students, better cognitive performance was associated with a less gender-typical finger-length ratio, for both men and women. These findings are discussed in the context of other similar reports and a possible curvilinear relation between hormones and cognition in normal populations.

Sex differences in the lateralized processing of facial emotion

Two reaction time tasks were administered to male and female normal subjects, involving judgments of facial emotion. In the Word-Face task, judgments of similarity or difference of a centrally presented emotion word and an emotional face presented in the left or right visual field were required, and in the Face-Face task, comparisons of a centrally presented and a laterally presented emotional face were required. Results were significant for the matching trials only. Reaction times to negative emotions were faster overall than to positive emotions, and an Emotional Valence by Visual Field interaction was found such that reaction times were faster for negative emotions in the left visual field and for positive emotions in the right visual field. This interaction was significant for the female but not the male subjects, although similar patterns were observed in both sexes. Further, an interaction of Gender, Task, and Emotional Valence was found, such that the two tasks had opposite effects for the two sexes. The Face-Face task appeared to inhibit the performance of the male subjects and facilitate the performance of the female subjects in terms of reaction time. It was suggested that specifying the target emotion by an emotional face elicits a greater emotional response on the part of the subject than specification by a word, and that this emotional elicitation may result in a reactive inhibition in the male subjects and in an elaboration of the emotional response in the female subjects.

Effect of topiramate on attention

Impaired attention is a frequently reported side effect of anti-epileptic medication, as well as a frequent general complaint of epilepsy. It is thus important to evaluate the effect of new medications on attention processes. Attention was assessed weekly in ten subjects receiving topiramate over a 3 month period. Attention was evaluated with digit span, a widely used index of attention. Different number sequences were constructed and randomized to allow for repeated use. Four of nine subjects showed significant correlations between topiramate dosage and forward digit span measured weekly, such that higher dosage was associated with poorer attention. The average topiramate dosage and seizure reduction did not differ between these subjects and those who did not show a significant relationship.

Utilization Rates of Ecologically Oriented Instruments Among Clinical Neuropsychologists

The ecological validity of neuropsychological instruments has become an important topic in recent decades, as neuropsychologists are asked to address real-world outcomes with increasing frequency. Although novel instruments that tap skills required for everyday functioning have been developed, it is unclear whether these instruments are migrating from research laboratories into the applied settings of clinical neuropsychologists. The current study surveyed assessment practices of neuropsychologists with regard to their utilization of instruments designed with ecological concerns in mind. Respondents included 747 North American, doctorate-level psychologists (40% usable response rate) affiliated with Division 40 of the American Psychological Association, National Academy of Neuropsychology, or the International Neuropsychological Society. Results indicated that approximately one-third of respondents reported use of ecologically oriented instruments (EOIs), and these instruments were generally utilized with much less frequency than traditional measures. Additionally, certain practice demographics affected usage rates of EOIs. Study findings are interpreted in the context of a growing body of literature that calls attention to the importance of developing and utilizing instruments that are able to handle the complex, real-world issues increasingly addressed during the neuropsychological assessment process.

Gender differences in implicit and explicit memory for affective passages

Thirty-two participants were administered 4 verbal tasks, an Implicit Affective Task, an Implicit Neutral Task, an Explicit Affective Task, and an Explicit Neutral Task. For the Implicit Tasks, participants were timed while reading passages aloud as quickly as possible, but not so quickly that they did not understand. A target verbal passage was repeated three times, and alternated with other previously unread passages. The Implicit Affective and Neutral passages had strong affective or neutral content, respectively. The Explicit Tasks were administered at the end of testing, and consisted of multiple choice questions regarding the passages. Priming effects in terms of more rapid reading speed for the target compared to non-target passages were seen for both the Implicit Affective Task and the Implicit Neutral Task. Overall reading speed was faster for the passages with neutral compared to affective content, consistent with studies of the emotional Stroop effect. For the Explicit memory tasks, overall performance was better on the items from the repeated passage, and on the Affective compared to Neutral Task. The male subjects showed greater priming for affective material than female subjects, and a greater gain than female subjects in explicit memory for affective compared to neutral material.

Effects of gender and personality on the Conners Continuous Performance Test.

A total of 91 university community participants were evaluated on the five personality factors (NEO–Five Factor Inventory; NEO-FFI) and with the Conners Continuous Performance Test (CPT). Gender differences for the Conners CPT variables were found such that the men were faster and less variable in their reaction times than the women, and the women were more sensitive in terms of signal detection and conservative in their responses than the men, consistent with the data reported by Conners, Epstein, Angold, and Klaric (2003) for a normative sample of 9–18 year olds. Interesting relationships between personality factors and the CPT variables were seen for the male and female groups, especially in terms of response style and vigilance. For the combined genders, higher vigilance was associated with higher neuroticism, lower extraversion, and lower agreeableness. Lower conscientiousness was associated with a more risk-taking/less conservative response bias. The men were more vigilant than the women, and for the men, this higher vigilance was related to lower conscientiousness, with trends for relationships with greater neuroticism and lower agreeableness. In the women, higher vigilance was related to lower extraversion, consistent with other studies. Men who were more extraverted also tended to be less conservative/more risk taking in their response style. A more risk-taking response style in women was associated with higher neuroticism, higher openness, and lower conscientiousness. The findings are interpreted in terms of underlying biological bases of behavior.

Statistical Analysis of Measures of Arousal in Ovariectomized Female Mice

In preparation for evaluating hormone effects and hormone receptor gene influences on fundamental processes of behavioral arousal, we subjected 48 ovariectomized female mice to a rigid protocol of several tests bearing on arousal concepts. The central hypothesis was that results would organize themselves according to capacities for sensory alertness, motor activity, and emotional reactivity. The large table of across-mouse correlation was subjected to factor analysis and cluster analysis. Results provided evidence for a general arousal (one-factor solution) which, however, accounted for only 29.72% of the variance. Four-factor (72.03%) matched four-cluster and six-factor (84.38%) matched six-cluster lineups of behavior components quite well, but did not conform to the main hypothesis; e.g., home cage exploration frequency and duration variables did not covary, and locomotor wheel activity grouped with fear indices. Besides providing a baseline for ongoing estrogen/thyroid and related genetic experiments, this statistical approach should be useful for a variety of hormonal studies of complex behaviors in mice.

Visual field differences for clockwise and counterclockwise mental rotation

Geometric line drawings were presented to normal subjects in the left visual field (LVF) or right visual field (RVF) at various degrees of rotation from a centrally presented vertical standard. The task of the subject was to indicate with a reaction time (RT) response whether the laterally presented stimulus could be rotated into the vertical standard or if it was a rotated mirror image of the standard. In Study 1, an overall right hemisphere superiority was found for RT and accuracy on match trials. Most interestingly, interactions between Visual Field and Rotation Angle for the match accuracy data and between Visual Field and Direction of Rotation (clockwise or counterclockwise) for the match RT slopes were found. These interactions suggested that clockwise rotations were more readily performed in the LVF and counterclockwise rotations in the RVF, consistent with other literature for mental rotation. The purpose of Study 2 was to replicate this finding of visual field differences for rotation direction using a design in which direction and degree of rotation were varied orthogonally. No main effect of Visual Field was found. However, significant interactions between Visual Field and Rotation Angle were found for both RT and accuracy, confirming the presence of visual field differences for rotation direction in a new sample of subjects. These differences were discussed in terms of the possibly greater relevance of medially directed stimuli and a possible hemispheric bias for rotation direction, and in terms of interhemispheric transmission factors.