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R M Stelmack

Publications and source records attributed to R M Stelmack.

At least 19 recordsLinked to original sources
PubMed2001

Event-related potentials and picture-word naming: effects of attention and semantic relation for children and adults.

Event-related potentials (ERPs) were recorded from children, 9 to 13 years of age, while they named words and pictures. The words and pictures were presented individually and in superimposed picture-word pairs in which the meaning of the words and pictures was either congruent, semantically associated, or incongruent. Both words and pictures elicited large amplitude negative waves (N450) at anterior electrode sites. The amplitude of this N450 wave was larger for individually presented pictures than for words. N450 amplitude was also larger when naming pictures than when naming words in the superimposed arrays, an effect that is attributed to differences in attentional demand required to name pictures rather than to exogenous stimulus characteristics. No significant effects of semantic incongruity were observed. These ERP waveforms for children differ from those observed for adults who exhibited positive amplitude waves to individually presented pictures and who also exhibited semantic incongruity effects.

Adult↗
PubMed2000

Effects of attention and semantic relation on event-related potentials in a picture-word naming task.

The interactive effects of attention and semantic relation on event-related potential (ERP) waveforms were examined during a naming task in which the physical stimulus array was the same across conditions. Superimposed picture-word pairs were presented in which the meaning of the words and pictures was congruent, semantically associated, or incongruent. In separate conditions, participants named words or pictures while ignoring the other stimulus. When words were attended, the superimposed pictures modulated the amplitude of P240 waves at posterior sites compared with when words were presented individually, but had no effect on N450 waves. In contrast, when pictures were attended to, the superimposed incongruent words elicited larger amplitude N450 waves at anterior sites than did congruent words or individually presented pictures. These effects affirm the independent processing of words and pictures during attention and are consistent with automatic and controlled processing of words and pictures, respectively. They also illustrate the endogenous nature of these late ERP waves.

Adult↗
PubMed2000

Individual differences in mismatch negativity measures of involuntary attention shift.

OBJECTIVE: The purpose of this study was to compare the automatic detection of deviance in introverts and extraverts. Event-related potentials were recorded to standard and deviant stimuli. These were presented either rapidly or slowly. Stimuli that are presented slowly may intrude into consciousness. METHODS: Twenty subjects were tested and divided into introverted and extraverted groups. A 500 Hz standard stimulus was presented on 85% of trials. On the remaining 15% of trials, a 750 Hz deviant was presented. In separate conditions, stimuli were presented rapidly (every 500 ms) or slowly (every 1500 ms). Subjects ignored the stimuli while reading. RESULTS: The deviant stimulus elicited a mismatch negativity (MMN) in both conditions. No inter-group differences in the MMN emerged when a rapid rate of presentation was employed. When a slower rate was employed, a late negativity was significantly larger for the extraverted than the introverted group. This was followed by a late positive wave. CONCLUSION: The late negative-positive complex is thought to reflect intrusiveness. It would therefore appear that extraverts are more distractible than introverts when stimuli are presented slowly.

Acoustic Stimulation↗
PubMed2000

An event-related potential analysis of extraversion and individual differences in cognitive processing speed and response execution.

Individual differences in cognitive processing speed and response execution were examined in relation to extraversion. Event-related potentials (ERPs) were recorded concurrently with reaction time and movement time (MT) measures as participants (N = 67) performed simple reaction time and stimulus-response compatibility tasks. Slower processing speed for extraverts, as indicated by longer latency of a late positive ERP wave, P3, was only evident in conditions in which stimulus information was in conflict with response selection demands. As previously reported, the salient effect in all conditions of both tasks was faster MT for extraverts, an effect that is indicative of differences in fundamental motor processes. On the simple reaction time task, amplitudes of the N1 component, an early negative ERP wave, were smaller for extraverts than for introverts in response to auditory tones, an effect that affirms the enhanced sensory reactivity of introverts to punctate physical stimuli.

Adolescent↗
PubMed1999

The effect of response execution on P3 latency, reaction time, and movement time.

This study examined the effect of response selection and execution on P3 latency during the performance of simple reaction time (RT) and stimulus-response compatibility tasks. Response time on these tasks was defined in terms of RT and movement time (MT). Event-related brain potentials were recorded from 67 female participants concurrently with the performance measures. On the simple RT task, the distance of the response button from the home button was varied (7, 15, and 23 cm). When stimulus evaluation demands were minimal, response execution affected P3 latency, with increased response button distance resulting in increased P3 latency. However, these movement effects were modest, and in most protocols, would not be a confounding factor. The stimulus-response compatibility task examined the interaction of stimulus evaluation demands and response requirements. RT, MT, and P3 latency were affected by stimulus congruency, whereas RT and P3 amplitude were affected by response compatibility.

Adult↗
PubMed1994

Learning disability subtypes and the effects of auditory and visual priming on visual event-related potentials to words.

Three learning-disability (LD) subtype groups and a normal control group of children were compared in their visual event-related potentials (ERPs) to primed and unprimed words. The LD subtypes were defined by deficient performance on tests of arithmetic (Group A), reading and spelling (Group RS), or both (Group RSA). The primed words were preceded by pictures or spoken words having a related meaning, while unprimed words were preceded by non-associated pictures or spoken words. For normal controls, N450 amplitude was greater to unprimed words than to words primed by pictures and spoken words. For Group A, N450 amplitude was reduced by spoken-word primes, but not by picture primes, an effect that demonstrates a deficit in processing visual-spatial information. For Group RS and Group RSA, neither picture nor spoken-word primes reduced N450 amplitude. These effects can be understood in terms of deficiencies in processing auditory-verbal information. Normal controls displayed a greater left- than right-hemispheric asymmetry in frontal N450 amplitude to unprimed words, an effect that is consistent with the association of skilled reading with hemispheric specialization. This asymmetry was absent in the ERPs of all the LD subtypes. The distinct ERP effects for the groups endorses the value of defining LD subtypes on the basis of patterns of deficits in arithmetic and reading and spelling.

Adolescent↗
PubMed1991

Advances in personality theory and research.

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.

Humans↗
PubMed1990

The effect of picture priming on event-related potentials of normal and disabled readers during a word recognition memory task.

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.

Arousal↗
PubMed1990

Biological bases of extraversion: psychophysiological evidence.

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.

Arousal↗
PubMed1990

Event-related potentials and recognition memory for pictures and words: the effects of intentional and incidental learning.

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.

Adult↗
PubMed1988

Recognition memory for words and event-related potentials: a comparison of normal and disabled readers.

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.

Child↗
PubMed1979

Neuroticism and the effect of stress on the pupillary light reflex.

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.

Humans↗