Kant and Husserl

This paper was presented at the Kant-Congress held in Memphis, Tennessee in March, 1995.     

Neural mechanisms of affective interference in schizotypy

Negatively valenced stimuli foster cognitive impairment in schizotypy and schizophrenia. To identify relevant brain mechanisms, the authors had 16 positive-schizotypy and 16 control participants perform an emotional Stroop task, judging the ink color of negative and neutral words during functional magnetic resonance imaging (fMRI) of regional brain activity. Schizotypy individuals showed increased right and decreased left activity in dorsolateral prefrontal cortex, indicating a deficit in maintenance of attentional set in the presence of negative emotional distractors. They also showed abnormal activity in ventral limbic areas, including decreased activity in nucleus accumbens and increased activity in hippocampus and amygdala, a circuit involved in the integration of cognitive and affective processes. These results indicate that aspects of emotion-cognition processes and the brain mechanisms that implement them are similar in schizotypy and schizophrenia.     

The relevance of Husserl today

Lecture given at the Annual meeting of the British Society for Phenomenology held at St. Edmund Hall, Oxford, on 25 March 1988. The occasion was remembering Husserls passing away fifty years ago.     

Emotion-modulated performance and activity in left dorsolateral prefrontal cortex

Functional MRI (fMRI) was used to examine the relationship between processing of pleasant and unpleasant stimuli and activity in prefrontal cortex. Twenty volunteers identified the colors in which pleasant, neutral, and unpleasant words were printed. Pleasant words prompted more activity bilaterally in dorsolateral prefrontal cortex (DLPFC) than did unpleasant words. In addition, pleasant words prompted more activity in left than in right DLPFC. Response speed to pleasant words was correlated with DLPFC activity. These data directly link positive affect, enhanced performance, and prefrontal activity, providing some of the first fMRI evidence supporting models of emotional valence and frontal brain asymmetry based on electroencephalography (EEG).     

Differential effects of glucose on modulation of emotional and nonemotional spatial memory tasks

Research examining the memory-enhancing effects of glucose in humans has been limited to mnemonic tasks lacking affective components, even though glucose may be a mechanism for emotioninduced memory enhancement. This limitation does not permit analysis of interactions between the enhancing properties of emotional stimuli and glucose. Participants were administered either glucose or saccharin 15 min prior to completing a neutral or emotional spatial memory task. Performance under three glycemic conditions (100 mg/kg or 50 g glucose, or placebo) for the two sets of emotional stimuli revealed a significant interaction. Both 100-mg/kg and 50-g doses of glucose resulted in impaired performance for emotional stimuli. For neutral stimuli, a 100-mg/kg dose enhanced memory, whereas a 50-g dose showed no effect. Results indicate that the enhancing effects of emotional stimuli may be attenuated by the consumption of glucose and suggest that recent food consumption should be considered in paradigms examining memory.     

Perceptual complexity of lexical,surface structure,and deep structure types of ambiguous sentences and change in heart rate

Studies comparing lexical, surface-, and deep-structure types of ambiguous sentences with unambiguous ones for perceptual complexity show conflicting findings mainly because of task artifiacts and lack of adequate control of confounding variables. In the present study, three types of ambiguous sentences and matched unambiguous controls were compared. Acceleration and deceleration measures of heart rate (HR) were used since these have been shown to reliably indicate complexity of cognitive activity. The study used a Groups x Ambiguity Condition x Ambiguous Sentence-Type x Sentence-Clusters repeated measures Latin Square ANOVA design which permitted isolation of variance related to the specific ample of sentences used. Eighteen low-bias ambiguous sentences (six from each type) and their control pairs, divided into three lists, were presented to 30 male undergraduates. Analysis of data showed: (1) significant Ambiguity x Type and Ambiguity effects for the percentage of increase in HR during processing of the sentence and, (2) significant effect of Ambiguity for the percentage of decrease in HR. These results were interpreted as showing that while low-bias ambiguous sentences are perceptually more complex than unambiguous ones, the effect of ambiguity may be greater for deep-structure type of ambiguous sentences than for lexical and surface-structure types.