Biomedical subjects
Publications and source records attributed to R M Stelmack.
This paper briefly describes important advances in personality research that have been achieved during the past 20 years in the development of a fundamental personality typology and in the determination of the heritability of personality traits. Research conducted at the University of Ottawa that has contributed to the exploration of the biological bases of the extraversion trait is summarized.
Normal and one subtype of disabled readers were compared in their visual event-related potentials (ERPs) that were elicited by primed and unprimed words during a recognition memory task. The primed words were preceded by a picture having the same denotative meaning, while unprimed words were preceded by a picture having a non-associated meaning. Normal readers exhibited consistently greater amplitude than the disabled readers to unprimed words with a negative wave at 455 ms (N400). For the disabled readers, this N400 was evident, though somewhat smaller, than for controls, at fronto-central placements, but absent at the lateral parietal and occipital sites. Priming a word with a picture reduced N400 amplitude for both the normal and disabled readers. There were no remarkable differences between groups in their ERPs to the pictures. The pattern of ERP results obtained seems to reflect a failure of this subtype of disabled readers to engage long-term, semantic memory, while their short-term linguistic processing is intact.
There is a good deal of evidence, particularly from electrodermal and electrocortical recording procedures, that introverts exhibit greater reactivity to sensory stimulation than extraverts. There is little evidence that introverts and extraverts differ in base level of arousal in neutral conditions, and there is no clear evidence that their differences in sensitivity to stimulation are determined by differences in attentional state. Faster auditory brainstem evoked response latencies observed for introverts implicate differences in peripheral sensory processes that are not determined by mechanisms in the reticular system as proposed in the arousal hypothesis. There is also evidence that individual differences in the expression of motor activity between introverts and extraverts involve differences in motoneuronal excitability.
Event-related potentials were recorded under conditions of intentional or incidental learning of pictures and words, and during the subsequent recognition memory test for these stimuli. Intentionally learned pictures were remembered better than incidentally learned pictures and intentionally learned words, which, in turn, were remembered better than incidentally learned words. In comparison to pictures that were ignored, the pictures that were attended were characterized by greater positive amplitude frontally at 250 ms and centro-parietally at 350 ms and by greater negativity at 450 ms at parietal and occipital sites. There were no effects of attention on the waveforms elicited by words. These results support the view that processing becomes automatic for words, whereas the processing of pictures involves additional effort or allocation of attentional resources. The N450 amplitude was greater for words than for pictures during both acquisition (intentional items) and recognition phases (hit and correct rejection categories for intentional items, hit category for incidental items). Because pictures are better remembered than words, the greater late positive wave (600 ms) elicited by the pictures than the words during the acquisition phase is also consistent with the association between P300 and better memory that has been reported.
Visual event-related potentials elicited during a word-recognition memory task were examined for groups of normal and disabled readers (RD). The strong association of reading ability with recognition memory performance endorsed the appropriateness of this signal detection paradigm as a reading-related task. Enhanced amplitude of the P200 component for the RD group was evident during both the acquisition and recognition series and it is indicative of differences at an early sensory stage of item encoding and retrieval. Normal readers displayed greater N400 amplitude than the RD group during both the acquisition and recognition series, an effect which is consistent with more extensive semantic evaluation or memory search that is attributed to that component. In the absence of any remarkable differences in P300 amplitude between groups, the poorer recognition memory performance for the RD group may not be attributable to attentional deficits.
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The pupillary light reflex was recorded under control, stress and fatigue conditions for 30 subjects equally divided into groups low, moderate, and high in Neuroticism. The effects of stress were distinguished by a decrease in both latency and extent of pupillary constriction during the initial light stimulation trials, as well as by a greater magnitude of redilation. Latency to maximum constriction and extent of constriction and redilation progressively decreased during the fatigue condition. No differences between Neuroticism groups were observed although it was noted that Neuroticism was negatively correlated with magnitude of redilation during the post-stress condition.
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Three experiments were designed to investigate the role of the orienting response (OR) in the recognition memory for pictures and words. In the first experiment (n = 60), pictures which were shown to have a high frequency of correct recognition in an independent analysis of recognition memory evoked larger initial ORs than words and low recognition frequency pictures. In experiment 2 (n = 56) subjects participated in the recognition memory task and then they received 12 repetitions of a picture or word stimulus which they either recognized or failed to recognize. The magnitude of the initial electrodermal OR was larger for the not recognized than for the recognized stimuli. This finding, which is a stimulus priming effect, was replicated in experiment 3 (n = 40). In experiments 1 and 2, recovery of the OR following a habituation series was induced by a change to the alternate representational form of the stimulus. Differences between the picture-word and word-picture transitions were not consistent between experiments. Overall, the experiments indicate that OR magnitude is influenced by the availability of the stimulus memory trace, with increased amplitude determined by less accessible memory traces.