Biomedical subjects

M E Nicholls

Publications and source records attributed to M E Nicholls.

At least 19 recordsLinked to original sources

PubMed2001

Cerebral asymmetries in the level of attention required for word recognition.

Words presented to the right visual field (RVF) are recognised more readily than those presented to the left visual field (LVF). This RVF advantage could reflect: (a) the direct connection between the RVF and left hemisphere, (b) an attentional bias directed towards the RVF, or (c) an attentional advantage, where the left hemisphere is able to recognise words using less attention than the right hemisphere. The attentional bias and advantage models were tested in 20 dextral adults during a divided visual field word-naming task. Spatial attention was manipulated with valid, invalid, or neutral central cues. Error and reaction time measures revealed a RVF advantage for word recognition. If the attentional bias model is correct, the RVF advantage should have been attenuated for valid and invalid cues compared to neutral cues. Instead of this, an interaction emerged whereby the cueing effect was stronger for words in the LVF than the RVF. This interaction has been reported previously in studies using peripheral spatial cues. The interaction suggests that the RVF requires less attention to process words than the LVF. This left hemisphere attentional advantage may reflect asymmetries between the hemispheres in their word processing styles.

Journal Article↗

PubMed2001

The cost of expecting events in the wrong sensory modality.

We examined the effects of modality expectancy on human performance. Participants judged azimuth (left vs. right location) for an unpredictable sequence of auditory, visual, and tactile targets. In some blocks, equal numbers of targets were presented in each modality. In others, the majority (75%) of the targets were presented in just one expected modality. Reaction times (RTs) for targets in an unexpected modality were slower than when that modality was expected or when no expectancy applied. RT costs associated with shifting attention from the tactile modality were greater than those for shifts from either audition or vision. Any RT benefits for the most likely modality were due to priming from an event in the same modality on the previous trial, not to the expectancy per se. These results show that stimulus-driven and expectancy-driven effects must be distinguished in studies of attending to different sensory modalities.

Adult↗

PubMed2000

Inhibition of return is supramodal: a demonstration between all possible pairings of vision, touch, and audition.

Inhibition of return' (IOR) refers to the delayed detection often found for targets at the same location as a preceding event. We examined whether IOR reflects a truly supramodal phenomenon, in an experiment designed to avoid criticisms of previous crossmodal research. We presented a random sequence of visual, tactile, and auditory targets to either the left or right of central fixation, and tested for IOR between targets in all three modalities when presented successively to the same versus different side. Speeded detection for targets in all three modalities was indeed slower if the preceding target had been presented from the same position, regardless of the modality, of this preceding target. These results demonstrate for the first time that IOR is truly supramodal.

Acoustic Stimulation↗

PubMed2000

Cerebral lateralization and cognitive functioning in patients with congenital adrenal hyperplasia.

A battery of tests was administered to 17 patients with congenital adrenal hyperplasia (CAH) and 17 normal controls to investigate the effect of prenatal androgen exposure on cerebral lateralization and cognitive performance. Individuals were compared on measures of hand preference, verbal and performance IQ, and temporal processing asymmetry. A higher incidence of left-handedness was found among CAH participants. CAH individuals exhibited higher performance IQs as opposed to verbal IQs. Temporal processing asymmetries were investigated using an auditory gap detection task. Measures of reaction time and response error revealed a right-ear, therefore left-hemisphere, advantage for gap detection. This right-ear advantage did not differ between CAH individuals and controls. Results partially support the hypothesis that prenatal androgen exposure causes a shift in cerebral lateralization toward right-hemisphere dominance.

Adolescent↗

PubMed2000

A left hemisphere, but not right hemispace, advantage for tactual simultaneity judgments.

Hemispheric asymmetries for tactile simultaneity judgments were investigated in 34 dextral adults. Pairs of vibrotactile stimuli with simultaneous or successive onsets were delivered unilaterally to the left or right hand. Participants made a forced-choice, bipedal response, indicating whether a stimulus was simultaneous or successive. The effect of hemispatial attentional biases was investigated, using ipsilateral (arms uncrossed) and contralateral (arms crossed) hand placements. Trials presented to the right hand were associated with fewer errors and a trend for faster response times than were those presented to the left hand. There was no asymmetry in response bias. Manipulations of hemispace did not affect the right hand advantage. These results confirm the existence of a left hemisphere temporal-processing advantage but fail to demonstrate that the asymmetry is the result of a rightward attentional bias. The implications of these results for absolute and relative models of hemispheric specialization are discussed.

Adolescent↗

PubMed1999

Laterality of expression in portraiture: putting your best cheek forward.

Portraits, both photographic and painted, are often produced with more of one side of the face showing than the other. Typically, the left side of the face is overrepresented, with the head turned slightly to the sitter's right. This leftward bias is weaker for painted male portraits and non-existent for portraits of scientists from the Royal Society. What mechanism might account for this bias? Examination of portraits painted by left- and right-handers and of self-portraits suggests that the bias is not determined by a mechanical preference of the artist or by the viewer's aesthetics. The leftward bias seems to be determined by the sitters and their desire to display the left side of their face, which is controlled by the emotive, right cerebral hemisphere. When we asked people to portray as much emotion as possible when posing for a family portrait, they tended to present the left side of their face. When asked to pose as scientists and avoid portraying emotion, participants tended to present their right side. The motivation to portray emotion, or conceal it, might explain why portraits of males show a reduced leftward bias, and also why portraits of scientists from the Royal Society show no leftward bias.

Adult↗

PubMed1999

Handedness in opposite and same-sex dizygotic twins: testing the testosterone hypothesis.

Prenatal exposure to testosterone is proposed to promote development of the right hemisphere and increase the incidence of sinistrality. This proposition was tested by comparing the hand preference of 59 opposite-sex and 61 same-sex dizygotic twins. Because testosterone is thought to pass between twins in utero, it was predicted that females with a male twin would show a high incidence of sinistrality compared to females with a female twin. Similarly, it was predicted that males with a male twin would be more likely to be sinistral than males with a female twin. Measures of the strength of hand preference and the incidence of sinistrality revealed no difference between the opposite and same-sex twins for either sex. The data also failed to confirm reports that first-born twins are more likely to be sinistral than second-born twins. These data add to a growing body of research which is critical of the testosterone hypothesis.

Adolescent↗

PubMed1999

Free-viewing perceptual asymmetries for the judgement of brightness, numerosity and size.

Perceptual asymmetries under free-viewing conditions were investigated in 24 normal dextral adults. Three tasks were administered that required participants to chose between a pair of left/right reversed stimuli on the basis of their brightness, numerosity or size. These stimulus features were represented asymmetrically within the stimuli, so that each stimulus appeared darker, larger or more numerous on the left or right sides. Participants more often selected the stimulus with the relevant feature on the left-hand side for all three tasks. Response times for leftward responses were faster than rightward responses. Split-half reliabilities revealed a high level of consistency within the tasks. However, the correlation between tasks was low. These results suggest that the different tasks, while showing similar levels of perceptual asymmetry, engage distinct sets of lateralised processes.

Adolescent↗

PubMed1999

Does old age or Parkinson's disease cause bradyphrenia?

BACKGROUND: Age-related declines in intellectual functioning have been linked to slower processing of information. However, any slowness with advancing age could simply reflect slower movement rather than impaired cognition. To assess any age-related decline in cognitive speed, we used an accuracy-based task that does not require a speeded motor response and that measures the time required to acquire information (inspection time). To identify possible biological mechanisms of cognitive slowing, this task was also applied to patients with Parkinson's disease, a basal ganglia disorder that reportedly causes bradyphrenia (slower thought processes). METHODS: In one experiment, 16 young (mean age 22.4 years) and 16 older adults (mean age 71.6 years) matched for intelligence and education completed an inspection time task. The task required judgments as to order of onset of two lights, where the interval between onsets ranged from 20-250 msec. A second experiment compared 16 patients diagnosed with idiopathic Parkinson's disease and 16 age-matched controls upon the same task. RESULTS: Older adults demonstrated significant cognitive slowing compared to younger adults. Medicated nondemented Parkinsonian patients were not impaired on this task compared to age-matched controls. CONCLUSIONS: Clinical and empirical impressions of bradyphrenia in Parkinson's disease may instead reflect advancing age or slower movement, because the effects of age may be greater in some cases than the effects of basal ganglia disease once motor dysfunction has been allowed for.

Adult↗

PubMed1999

Psychophysical and electrophysiologic support for a left hemisphere temporal processing advantage.

OBJECTIVE: The objective of this study was to investigate cerebral asymmetries for the detection of brief temporal events in a group of 22 dextrals using psychophysical measures. BACKGROUND: By combining electrophysiologic and psychophysical measures, it should be possible to demonstrate that the right ear advantage reported in previous studies is the result of a left hemisphere temporal processing advantage rather than a rightward attentional bias. METHOD: Bursts of white noise lasting 300 milliseconds were delivered unilaterally to the participants' ears. Half of the stimuli contained a gap lasting either 4 or 6 milliseconds. Participants indicated whether or not the noise burst contained a gap. Asymmetries in alpha and beta activity at left and right temporal lobe sites were measured during the task. RESULTS: The psychophysical data confirmed previous reports of faster response times (RTs) and lower levels of error for the right ear (RE). There was no asymmetry in alpha activity between the left and right temporal lobes; however, there was a higher level of beta activity in the left temporal lobe. CONCLUSIONS: The electrophysiological data suggest that the perceptual asymmetry is not the result of a nonspecific rightward attentional bias but that of a left hemisphere specialization for the detection of brief temporal events. The relation between atypical temporal processing asymmetries and developmental learning disorders is discussed.

Adolescent↗

PubMed1998

The contribution of attention to the right visual field advantage for word recognition.

Perceptual asymmetries have been explained by structural, attentional bias and attentional advantage models. Structural models focus on asymmetries in the physical access information has to the hemispheres, whereas attentional models focus on asymmetries in the operation of attentional processes. A series of experiments was conducted to assess the contribution of attentional mechanisms to the right visual field (RVF) advantage found for word recognition. Valid, invalid and neutral peripheral cues were presented at a variety of stimulus onset asynchronies to manipulate spatial attention. Results indicated a significant RVF advantage and cueing effect. The effect of the cue was stronger for the left visual field than the RVF. This interaction supports the attentional advantage model which suggests that the left hemisphere requires less attention to process words. The attentional asymmetry is interpreted in terms of the different word processing styles used by the left and right hemispheres. These results have ramifications for the methodology used in divided visual field research and the interpretation of this research.

Adolescent↗

PubMed1998

Support for a structural model of aural asymmetries.

Right ear (RE) advantages for the recognition of speech can be explained by structural or attentional mechanisms. Structural mechanisms focus on biases in the neural access the ears have to the contralateral and ipsilateral cerebral hemispheres. Attentional mechanisms focus on biases in hemispatial attention. The contribution of structural and attentional mechanisms for a monaural lexical decision task was examined in a group of 26 dextral adults. Trials requiring a lexical decision were randomly intermixed with a tone discrimination task. A pre-test demonstrated that the tone discrimination task produced no ear asymmetry, but could be affected by shifts in spatial attention. Responses were faster in the RE for the lexical decision task. No asymmetry emerged for the tone discrimination task. If the RE advantage for lexical decisions was the result of an attentional bias, a RE advantage should have been evident for the tone discrimination task. The independence of the two tasks supports a structural model of perceptual asymmetry. A structural model which takes into account the dynamic functional organization of the hemispheres is proposed.

Acoustic Stimulation↗

PubMed1998

An intermanual advantage for tactual matching.

Previous research reports both increased and decreased levels of performance for concurrent tactual tasks when they are carried out by one hand (intramanual condition) rather than shared between the hands (intermanual condition). Intramanual advantages have been attributed to the benefits of intrahemispheric processing which avoids the need for the transcallosal passage of information. Intermanual advantages are attributed to the benefits of sharing the task load between the cerebral hemispheres. The effects of inter- and intramanual activity was investigated in a group of 72 dextrals. Subjects were required to make same/different discriminations for a tactual matching task. Faster completion times were observed for the intermanual condition compared to the intramanual condition. This suggests that the task was carried out more efficiently when the hemispheres shared the processing load. The intermanual advantage was accentuated for judgements of difference which place more strain on processing resources. There was no evidence of a left hand advantage for tactual matching of the type observed for Braille.

Adolescent↗

PubMed1998

Hemispheric asymmetries for the temporal resolution of brief tactile stimuli.

Hemispheric asymmetries for tactile temporal discriminations were examined in 29 dextrals. Vibrations lasting 120 ms were delivered unilaterally to the hands, half of which contained a gap lasting between 6 and 18 ms. Participants indicated whether or not the vibration contained a gap. Visual and auditory research has demonstrated a left hemisphere (LH) advantage for gap detection. However, this research has confounded the effects of hemisphere and hemispace. These effects were dissociated using midline and lateral hand placements. Reaction time (p < .05), response error (p < .1), and response bias (p < .05) measures revealed a LH advantage for gap detection. The asymmetry was reduced in the midline condition for the error data only (p < .1). These results demonstrate that the LH is better able to detect brief temporal events than is the right hemisphere. Hemispace appears to have a limited impact on this asymmetry.

Acoustic Stimulation↗

PubMed1998

Seasonal trends in the birth of sinistrals.

This study examined the proposition that hand preference may change with season of birth in a group of 523 students born in southern Australia. Hand preference and performance measures revealed a higher incidence of sinistrality or weak dextrality for individuals born in winter and autumn compared to summer and spring. These seasonal effects tended to be more pronounced for females compared to males. Similar seasonal patterns have been observed in the northern hemisphere. Previous research has accounted for seasonal changes in hand preference in terms of changes in the frequency of viral infections. It is proposed that seasonal variations in hand preference can also be accounted for by seasonal variations in hormone levels. Higher levels of testosterone in spring compared to autumn have been reported in females. Exposure to higher levels of testosterone during the first trimester of foetal development is thought to promote the development of the right hemisphere. Individuals born in winter would have been exposed to the high testosterone levels associated with spring during the first critical trimester of foetal brain development. The lack of seasonal effect observed for males may be related to endocrinological differences between the male and female foetus.

Journal Article↗

PubMed1998

Cross-modal links in exogenous covert spatial orienting between touch, audition, and vision.

Three experiments investigated cross-modal links between touch, audition, and vision in the control of covert exogenous orienting. In the first two experiments, participants made speeded discrimination responses (continuous vs. pulsed) for tactile targets presented randomly to the index finger of either hand. Targets were preceded at a variable stimulus onset asynchrony (150, 200, or 300 msec) by a spatially uninformative cue that was either auditory (Experiment 1) or visual (Experiment 2) on the same or opposite side as the tactile target. Tactile discriminations were more rapid and accurate when cue and target occurred on the same side, revealing cross-modal covert orienting. In Experiment 3, spatially uninformative tactile cues were presented prior to randomly intermingled auditory and visual targets requiring an elevation discrimination response (up vs. down). Responses were significantly faster for targets in both modalities when presented ipsilateral to the tactile cue. These findings demonstrate that the peripheral presentation of spatially uninformative auditory and visual cues produces cross-modal orienting that affects touch, and that tactile cues can also produce cross-modal covert orienting that affects audition and vision.

Adolescent↗

PubMed1997

No evidence of hemispheric facilitation following the induction of negative and positive affect.

A dichotomy is thought to exist between the hemispheres whereby the right hemisphere is specialized for the processing of negative emotions and the left hemisphere is specialized for positive emotions. Van Strien and Morpurgo (Neuropsychologia, 1992, 30, 845-848) demonstrated that the activation of negative and positive emotional states resulted in the allocation of attentional resources to the contralateral hemispace. In the present experiment we sought to replicate this effect and improve upon certain methodological features of the experiment. The effect of positive and negative emotions on performance in the left and right visual fields was investigated in 30 dextral students. Positive and negative emotional states were generated by presenting subjects with an emotive word prior to each trial and subsequently requiring them to use that word within a sentence. Performance within the left and right fields was measured using a gap detection task which was neutral in relation to functional asymmetry. No evidence of right or left visual field facilitation was found for the positive or negative conditions, respectively. These results are not interpreted as a refutation of hemispheric specialization for emotional valence. Instead, they are seen to highlight the frailty of hemispheric facilitation effects.

Adolescent↗

PubMed1997

Hemispheric asymmetries for the temporal resolution of brief auditory stimuli.

This study investigates a left-hemisphere (LH) advantage for the discrimination of fine temporal events within the auditory modality in 24 normal adults. Brief noise bursts were delivered monaurally to the left or right ears, half of which contained a gap lasting between 2 and 8 msec. Subjects were required to indicate whether or not the noise burst contained a gap. Research within this area has yielded conflicting results. It is possible that variations in gap position or the properties of the noise burst may have contributed to this conflict. The effect of gap position was investigated by systematically varying the position of the gap during half of the trials. White noise bursts were used to avoid the use of spectral cues. Reaction time, response bias, and response error measures revealed a right-ear (and hence LH) advantage for gap detection. Stable gap positions were recognized more accurately than variable gap positions. Gap position had no effect on the observed LH advantage. These results suggest that the auditory properties of noise burst, rather than gap position, play an important role in the discrepancies observed in this area.

Adolescent↗