Showing papers in "Neuroreport in 2002"
TL;DR: It is found that increased alpha power was correlated with decreased MRI signal in multiple regions of occipital, superior temporal, inferior frontal, and cingulate cortex, and with increased signal in the thalamus and insula and may have important implications for interpretation of resting baseline in fMRI studies.
Abstract: The alpha rhythm in the EEG is 8-12 Hz activity present when a subject is awake with eyes closed. In this study, we used simultaneous EEG and fMRI to make maps of regions whose MRI signal changed reliably with modulation in posterior alpha activity. We scanned 11 subjects as they rested with eyes closed. We found that increased alpha power was correlated with decreased MRI signal in multiple regions of occipital, superior temporal, inferior frontal, and cingulate cortex, and with increased signal in the thalamus and insula. These results are consistent with animal experiments and point to the alpha rhythm as an index of cortical inactivity that may be generated in part by the thalamus. These results also may have important implications for interpretation of resting baseline in fMRI studies.
1,072 citations
TL;DR: Results show that mechanical properties of the substrate specifically direct the formation of neurite branches, which are critical for appropriate synaptic connections during development and regeneration.
Abstract: The mechanical properties of substrates underlying cells can have profound effects on cell structure and function. To examine the effect of substrate deformability on neuronal cell growth, protein-laminated polyacrylamide gels were prepared with differing amounts of bisacrylamide to generate substrates of varying deformability with elastic moduli ranging from 500 to 5500 dyne/cm. Mouse spinal cord primary neuronal cells were plated on the gels and allowed to grow and extend neurites for several weeks in culture. While neurons grew well on the gels, glia, which are normally co-cultured with the neurons, did not survive on these deformable substrates even though the chemical environment was permissive for their growth. Substrate flexibility also had a significant effect on neurite branching. Neurons grown on softer substrates formed more than three times as many branches as those grown on stiffer gels. These results show that mechanical properties of the substrate specifically direct the formation of neurite branches, which are critical for appropriate synaptic connections during development and regeneration.
755 citations
TL;DR: It is concluded that emotional expression analysis and the structural encoding of faces are parallel processes and early emotional ERP modulations may reflect the rapid activation of prefrontal areas involved in the analysis of facial expression.
Abstract: Using event-related brain potentials (ERPs), we investigated the time course of facial expression processing in human subjects watching photographs of fearful and neutral faces. Upright fearful faces elicited a frontocentral positivity within120 ms after stimulus presentation, which was followed by a broadly distributed sustained positivity beyond 250 ms post-stimulus. Emotional expression eiects were delayed and attenuated when faces were inverted. In contrast, the face-speci¢c N170 component was completely unaiected by facial expression.We conclude that emotional expression analysis and the structural encoding of faces are parallel processes. Early emotional ERP modulations may re£ect the rapid activation of prefrontal areas involved in the analysis of facial expression. NeuroReport 13:1^5 c 2002 Lippincott Williams &W ilkins.
658 citations
TL;DR: It is proposed that the occasional activation of the fusiform gyrus when listening to spoken words is due to the topdown recruitment of visual orthographic or object representations.
Abstract: Event-related fMRI was used to test the hypothesis that the visual word form area in the left fusiform gyrus holds a modality-specific and prelexical representation of visual words. Subjects were engaged in a repetition-detection task on pairs of words or pronounceable pseudo-words that could be written or spoken. The visual word form area responded only to written stimuli, not to spoken stimuli, independently of their semantic content. We propose that the occasional activation of the fusiform gyrus when listening to spoken words is due to the topdown recruitment of visual orthographic or object representations.
619 citations
TL;DR: The ensemble of studies to date suggest that under certain conditions nicotine can act as an anxiolytic and an antidepressant, but that following chronic use, adaptations to nicotine can occur resulting in increased anxiety and depression following withdrawal.
Abstract: Nicotine has been shown to have effects on anxiety and depression in both human and animal studies. These studies suggest that nicotinic acetylcholine receptors (nAChRs) can modulate the function of pathways involved in stress response, anxiety and depression in the normal brain, and that smoking can result in alterations of anxiety level and mood. The effects of nicotine are complex however, and nicotine treatment can be either anxiolytic or anxiogenic depending on the anxiety model tested, the route of nicotine administration and the time course of administration. The paradoxical effects of nicotine on emotionality are likely due to the broad expression of nAChRs throughout the brain, the large number of nAChR subtypes that have been identified and the ability of nicotine treatment to both activate and desensitize nAChRs. Activation of nAChRs has been shown to modulate many systems associated with stress response including stress hormone pathways, monoaminergic transmission and release of classical neurotransmitters throughout the brain. Local administration studies in animals have identified brain areas that may be involved in the anxiogenic and anxiolytic actions of nicotine including the lateral septum, the dorsal raphe nuclei, the mesolimbic dopamine system and the hippocampus. The ensemble of studies to date suggest that under certain conditions nicotine can act as an anxiolytic and an antidepressant, but that following chronic use, adaptations to nicotine can occur resulting in increased anxiety and depression following withdrawal.
430 citations
TL;DR: Investigation of other ABC transporters in both normal and tumour human brain tissue and the presence of breast cancer resistance protein (BCRP) demonstrate that BCRP is located at the blood–brain barrier, mainly at the luminal surface of microvessel endothelium.
Abstract: Movement of substrates between blood and brain is known to be influenced by P-glycoprotein (P-gp) at the luminal surface of the endothelium lining brain microvessels and by multidrug resistance associated protein 1 (MRP1) at the basolateral surface of the choroid plexus epithelium. Here, using RT-PCR and Western blotting, we investigate other ABC transporters in both normal and tumour human brain tissue and demonstrate the presence of breast cancer resistance protein (BCRP). Immunofluorescence confocal microscopy demonstrates that BCRP is located at the blood-brain barrier, mainly at the luminal surface of microvessel endothelium. This localization closely resembles that of P-gp. BCRP has several substrates in common with P-gp and may pose an additional barrier to drug access to the brain.
401 citations
TL;DR: These findings provide the first direct evidence that the amygdala is involved in emotional reactions elicited by both positive and negative emotional words, and further indicate that positive words additionally activate brain regions related to reward.
Abstract: The human amygdala's involvement in negative emotion is well established, but relatively little is known regarding its role in positive emotion. Here we examined the neural response to emotionally positive, negative, and neutral words using fMRI. Relative to neutral words, positive and negative emotional words elicited greater activity in the left amygdala. Positive but not negative words elicited activity in dorsal and ventral striatal regions which have been linked in previous neuroimaging studies to reward and positive affect, including caudate, putamen, globus pallidus, and accumbens. These findings provide the first direct evidence that the amygdala is involved in emotional reactions elicited by both positive and negative emotional words, and further indicate that positive words additionally activate brain regions related to reward.
380 citations
TL;DR: This pattern of gray matter loss in mild cognitive impairment agrees with but considerably expands upon previous region-of-interest based MRI studies, and is highly consistent with the course of neurofibrillary tangles across aging and Alzheimer's disease.
Abstract: We used voxel-based morphometry to comprehensively and objectively map gray matter loss in 22 patients with amnestic mild cognitive impairment, defined as progressive isolated episodic memory decline. Compared with 22 age-matched healthy controls, patients had highly significant gray matter loss predominantly affecting the hippocampal region and cingulate gyri (posterior and subcallosal part of the anterior), and extending into the temporal neocortex. Compared with 16 age-matched patients with mild Alzheimer's disease, gray matter density was significantly preserved in mild cognitive impairment in the posterior association cortex. This pattern of gray matter loss in mild cognitive impairment agrees with but considerably expands upon previous region-of-interest based MRI studies, and is highly consistent with the course of neurofibrillary tangles across aging and Alzheimer's disease.
364 citations
TL;DR: FMRI results reveal significantly more activation in ventral striatum, orbitofrontal cortex, anterior cingulate and occipital regions for sports cars in contrast to other categories of cars, demonstrating that artificial cultural objects associated with wealth and social dominance elicit activation in reward-related brain areas.
Abstract: Using event-related fMRI we investigated the rewarding properties of cultural objects (cars) signaling wealth and social dominance. It has been shown recently that reward mechanisms are involved in the regulation of social relations like dominance and social rank. Based on evolutionary considerations we hypothesized that sports cars in contrast to other categories of cars, e.g. limousines and small cars, are strong social reinforcers and would modulate the dopaminergic reward circuitry. Twelve healthy male subjects were studied with fMRI while viewing photographs of diierent car classes followed by an attractivity rating. Behaviorally sports cars were rated signi¢cantly more attractive than limousines and small cars.Our fMRI results revealed signi¢cantly more activation in ventral striatum, orbitofrontal cortex, anterior cingulate and occipital regions for sports cars in contrast to other categories of cars.We could thus demonstrate that arti¢cial cultural objects associated with wealth and social dominance elicit activation in reward-related brain areas. NeuroReport 13:2499^2503 � c 2002 Lippincott Williams & Wilkins.
350 citations
TL;DR: It is found that rats with lesions of the orbitofrontal cortex acquired novel discrimination problems at the same rate as controls andImpairments were evident in lesioned rats when the response contingencies of the odors in the discrimination problem were reversed.
Abstract: Recent evidence suggests that orbitofrontal cortex lesions cause an inability to withhold inappropriate responses particularly when learned behavior must be modified to reflect changes in the likely outcome or consequence of responding. By this account, orbitofrontal cortex should not be necessary for acquisition of simple discrimination problems, but should be critical for acquiring reversals of those problems. However, previous work in rats has shown orbitofrontal cortex to be critical for withholding responses even in a simple go, no-go discrimination task. Here we have reexamined the contribution of rat orbitofrontal cortex to acquisition and reversal of go, no-go odor discrimination problems. Contrary to prior reports, we found that rats with lesions of the orbitofrontal cortex acquired novel discrimination problems at the same rate as controls. Impairments were evident in lesioned rats when the response contingencies of the odors in the discrimination problem were reversed. These findings suggest that orbitofrontal cortex is not necessary for inhibiting responses unless responses must be altered to reflect changing relationships between cues and outcomes.
321 citations
TL;DR: Results demonstrate that interference with immuno-inflammatory responses has a beneficial effect in the ALS mice model, suggesting this to be a potential new strategy to treat ALS.
Abstract: Microglial activation is thought to contribute to the progression of selective motor neuron death during amyotrophic lateral sclerosis (ALS) As minocycline has been shown to inhibit microglial activation, the therapeutic efficacy of this tetracycline derivative in the G93A mice model for familial ALS was tested This drug with proven safety delayed disease onset and dose-dependently extended the survival of the G93A mice At 120 days of age, minocycline protected mice from loss of motor neurons and from vacuolization These results demonstrate that interference with immuno-inflammatory responses has a beneficial effect in the ALS mice model, suggesting this to be a potential new strategy to treat ALS
TL;DR: A broader role for the amygdala in modulating the vigilance level during the perception of several negative and positive facial emotions is suggested.
Abstract: Most theories of amygdalar function have underscored its role in fear. One broader theory suggests that neuronal activation of the amygdala in response to fear-related stimuli represents only a portion of its more widespread role in modulating an organism’s vigilance level.To further explore this theory, the amygdalar response to happy, sad, angry, fearful, and neutral faces in 17 subjects was characterized using 3 T fMRI. Utilizing a random eiects model and hypothesis-driven analytic strategy, it was observed that each of the four emotional faces was associated with reliable bilateral activation of the amygdala compared with neutral. These ¢ndings suggest a broader role for the amygdala in modulating the vigilance level during the perception of several negative and positive facial emotions. NeuroReport13:1737^1741 � c 2002 Lippincott Williams & Wilkins.
TL;DR: It is suggested that brain size is the main variable determining the proportion of grey matter, with larger brains exhibiting relatively smaller proportions ofgrey matter.
Abstract: Magnetic resonance imaging was used to evaluate the in£uence of sex and brain size on compartmental brain volumes (grey matter, white matter, CSF) in a large and well-matched sample of neurologically normal women (n ¼ 50) and men (n ¼ 50) As expected, we found a signi¢cant sex diierence for the absolute volumes of total brain, grey matter, white matter and CSF, with greater volumes for men Relating these compartmental volume measures to brain volume resulting in proportional volume measures revealed a higher proportion of grey matter in women No signi¢cant sex diierences were found for white matter and CSF proportions However, when the in£uence of sex was partialized out by regression analyses, brain volume explained 40^ 81% of the variance of the absolute grey matter, white matter and CSF volumes Performing these regression analyses for the proportional volume measures revealed that brain volume explained B16% of the variance in grey matter proportion Sex or the interaction between sex and brain volume revealed no additional predicitve values Interestingly, the correlation between brain volume and grey matter proportion was negative, with larger brains exhibiting relatively smaller proportions of grey matter Thus, sex is not the main variable explaining the variability in grey matter volume Rather, we suggest that brain size is the main variable determining the proportion of grey matter NeuroReport 13:2371^2374 � c 2002 Lippincott Williams & Wilkins
TL;DR: Findings support the notion that failure of the ubiquitin-proteasome system to degrade and clear unwanted proteins is an important etiopathogenic factor in Parkinson's disease.
Abstract: Structural and functional defects in 26/20S proteasomes occur in the substantia nigra pars compacta and may underlie protein accumulation, Lewy body formation and dopaminergic neuronal death in Parkinson's disease. We therefore determined the pathogenicity of proteasomal impairment following stereot
TL;DR: It is concluded that phosphorylation of eIF2alpha is associated with the degeneration of neurons in AD.
Abstract: Inhibition of protein translation is a mode of inducing neuronal apoptosis and neurodegeneration in Alzheimer's disease (AD). Phosphorylation of eukaryotic initiation factor-2alpha (eIF2alpha) terminates global protein translation and induces apoptosis. We examined whether this signaling pathway occurs in degenerating neurons of AD. Brain sections from young individuals, age-matched control individuals and AD patients were examined for immunoreactivity of phosphorylated eIF2alpha by immunohistochemical analysis. While young brain sections did not display and age-matched brain sections have mild immunoreactive positive cells, AD brain sections revealed intense immunoreactivity for phosphorylated eIF2alpha. Most of the phosphorylated eIF2alpha immunoreactive positive neurons have high immunoreactivity for phosphorylated tau using AT8 antibody. Also, intense staining of phosphorylated eIF2alpha is associated vacuoles in degenerating neurons. This phenomenon was also observed for the immunohistochemical staining of phosphorylated PKR (double-stranded RNA-dependent protein kinase), the upstream kinase for eIF2alpha. Activation of PKR-eIF2alpha pathway is considered to be pro-apoptotic. In addition, formation of autophagy is regulated by eIF2alpha kinase. Therefore, it is concluded that phosphorylation of eIF2alpha is associated with the degeneration of neurons in AD.
TL;DR: A correlation between cochlear implant patients' auditory temporal processing and speech recognition abilities and mean modulation thresholds is reported, demonstrating the contribution of temporal processing to implant speech perception.
Abstract: Although the speech recognition performance of cochlear implant patients has steadily improved in recent years, considerable variability remains in implant patient outcomes. Here, we report on a correlation between cochlear implant patients' auditory temporal processing and speech recognition abilities. Modulation detection thresholds were measured as a function of stimulation level; phoneme recognition was also assessed. Results showed marked individual differences in the shape and absolute sensitivity of subjects' modulation threshold functions. Statistical analysis revealed a strong correlation between phoneme recognition scores and subjects' mean modulation thresholds, demonstrating the contribution of temporal processing to implant speech perception. In correlating a basic psychophysical measure to speech performance, these results should contribute toward improved speech processor design and rehabilitation tools for cochlear implant patients.
TL;DR: Overall, plasma lipoproteins may be an important factor in induction of AD-like plaques in mice and the lowering of plasma lipids may be therapeutic for AD patients.
Abstract: Epidemiological data show correlations between hypercholesterolemia and Alzheimer's disease (AD). We test the hypothesis that hypercholesterolemia modulates Abeta deposition in mice overexpressing the human APP695 Swedish mutation (K670N and M671L) (TgAPPsw). Feeding mice a high fat/high cholesterol (HFHC) diet for 7-10 months increased total cholesterol levels by 4-fold. The extent of Abeta immunostained plaque-like deposits were significantly higher for mice fed the HFHC diet as compared with mice fed rodent chow. Extent of deposits correlated inversely with plasma levels of HDL and directly to apolipoprotein E. Overall, plasma lipoproteins may be an important factor in induction of AD-like plaques in mice. The lowering of plasma lipids may be therapeutic for AD patients.
TL;DR: It is shown that prolonged sleep deprivation significantly decreased Cu/Zn-SOD activity in the hippocampus and brainstem, suggesting an alteration in the metabolism of ROS resulting in oxidative stress.
Abstract: Sleep deprivation by the disk-over-water technique results in a predictable syndrome of physiological changes in rats. It has been proposed that reactive oxygen species (ROS) may be responsible for some of these effects. A variety of antioxidative enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) help to regulate the level of ROS. In this study we investigated the effects of prolonged (5-11 days) sleep deprivation on the activities of SOD and GPx as well as the metabolic activity of the mitochondria (using alamar blue) in several brain regions (cortex, hippocampus, hypothalamus, brainstem and cerebellum). We show that prolonged sleep deprivation significantly decreased Cu/Zn-SOD activity in the hippocampus and brainstem, suggesting an alteration in the metabolism of ROS resulting in oxidative stress.
TL;DR: Overall, the development of cortical response latencies for the implanted children was more rapid than for their normal-hearing age-matched peers, demonstrating a high degree of central auditory system plasticity during early human development.
Abstract: The aim of our research was to estimate the time course of development and plasticity of the human central auditory pathways following cochlear implantation. We recorded cortical auditory-evoked potentials in 3-year-old congenitally deaf children after they were fitted with cochlear implants. Immediately after implantation cortical response latencies resembled those of normal-hearing newborns. Over the next few months, the cortical evoked responses showed rapid changes in morphology and latency that resulted in age-appropriate latencies by 8 months after implantation. Overall, the development of cortical response latencies for the implanted children was more rapid than for their normal-hearing age-matched peers. Our results demonstrate a high degree of central auditory system plasticity during early human development.
TL;DR: Findings do not fit the idea of the insula as a specific disgust processor, which is involved in the processing of visual stimuli depicting non-mimic disgust elicitors compared to fear-inducing and neutral scenes.
Abstract: fMRI studies have shown that the perception of facial disgust expressions specifically activates the insula. The present fMRI study investigated whether this structure is also involved in the processing of visual stimuli depicting non-mimic disgust elicitors compared to fear-inducing and neutral scenes. Twelve female subjects were scanned while viewing alternating blocks of 40 disgust-inducing, 40 fear-inducing and 40 affectively neutral pictures, shown for 1.5 s each. Afterwards, affective ratings were assessed. The disgust pictures, rated as highly repulsive, induced activation in the insula, the amygdala, the orbitofrontal and occipito-temporal cortex. Since during the fear condition the insula was also involved, our findings do not fit the idea of the insula as a specific disgust processor.
TL;DR: It was concluded, that the generators of all the infantile ERP peaks are functional already at birth, and that the maturational changes in the waveform morphology can mostly be accounted for by the changing relative strengths of the different generators.
Abstract: This study examined the maturation of cortical auditory event-related potentials (ERPs) from birth until 12 months of age. In the 15 infants studied, all ERP peaks observable at 12 months of age, the P150, N250, P350, and N450 were identifiable already at birth, As in previous studies, the amplitudes of the ERP peaks increased and latencies shortened with increasing age. In addition, the time courses of the amplitude growth of these peaks differed from each other. It was concluded, that the generators of all the infantile ERP peaks are functional already at birth, and that the maturational changes in the waveform morphology can mostly be accounted for by the changing relative strengths of the different generators.
TL;DR: It is concluded that foot sole input contributes to the coding and the spatial representation of body posture, namely body posture awareness and body representation in space.
Abstract: We investigated whether the tactile information from the main supporting areas of the foot are used by the brain for perceptual purposes, namely body posture awareness and body representation in space. We applied various patterns of tactile stimulation to one or both soles of unmoving and blindfolded subjects by a 60 micro-vibrator tactile matrix set in a force platform. The perceptual effects of the stimulation were assessed through a 3D joystick handled by the subjects. All subjects reported illusory perceptions of whole-body leaning. Both orientation and amplitude of these perceptions depended on the stimulation pattern. Additional kinesthetic illusions sometimes occurred along the longitudinal axis of the body. We conclude that foot sole input contributes to the coding and the spatial representation of body posture.
TL;DR: The variability from age to age might be, at least partially, caused by the differences in degree of infants' orienting, resulting in the reduction of the scalp recorded mismatch negativity in recordings when the orienting P3a positivity was elicited.
Abstract: Mismatch negativity (MMN) is a negative component of auditory event-related potential (ERP), reflecting the brain's automatic change detection process. In the present study we investigated the development of the pitch change detection, as indexed by the MMN, in the same infants from birth until 12 months of age. The MMN was identified in approximately 75% of infants at each age, being relatively stable in latency and amplitude at the group level across the ages studied. However, within the same subjects the MMN substantially varied from age to age. The inspection of individual data revealed a possible source of this variability: in a portion of 3- to 9-month-old infants, a large-amplitude positive component commenced at the latency of the MMN and thus might have masked it. The results of the additional experiment, employing distracting novel sounds in 2-year-old infants and newborns, suggested that the observed positive component could represent an infant analogue of the adult P3a response, indexing an involuntary orienting of attention. Therefore, the variability from age to age might be, at least partially, caused by the differences in degree of infants' orienting, resulting in the reduction of the scalp recorded mismatch negativity in recordings when the orienting P3a positivity was elicited.
TL;DR: Successful aging was characterized by preserved left prefrontal and enhanced right prefrontal activation that may have provided compensatory encoding resources.
Abstract: Declarative memory declines with age, but there is profound variation in the severity of this decline. Healthy elderly adults with high or low memory scores and young adults viewed words under semantic or non-semantic encoding conditions while undergoing fMRI. Young adults had superior memory for the words, and elderly adults with high memory scores had better memory for the words than those with low memory scores. The elderly with high scores had left lateral and medial prefrontal activations for semantic encoding equal to the young, and greater right prefrontal activation than the young. The elderly with low scores had reduced activations in all three regions relative to the elderly with high memory scores. Thus, successful aging was characterized by preserved left prefrontal and enhanced right prefrontal activation that may have provided compensatory encoding resources.
TL;DR: The levels of six proteins and their isoforms were significantly altered in CSF of AD patients, and the most prominently altered proteins were the apolipoproteins, especially proapolipoprotein.
Abstract: By comparing the CSF proteome between Alzheimer disease (AD) patients and controls it may be possible to identify proteins that play a role in the disease process and thus to study the pathogenesis of AD. We used mini-gel technology in a two-dimensional electrophoresis procedure, sensitive SYPRO Ruby staining and mass spectrometry for clinical screening of disease-influenced CSF proteins in 15 AD patients and 12 controls. The levels of six proteins and their isoforms, including proapolipoprotein, apolipoprotein E, beta-2 microglobulin, retinol-binding protein, transthyretin, and ubiquitin, were significantly altered in CSF of AD patients. The most prominently altered proteins were the apolipoproteins, especially proapolipoprotein.
TL;DR: Bilateral activity in the inferior parietal lobule in conditions involving confusion about the origin of the action confirmed its role in agency.
Abstract: Agency is the sense that I am the one generating an action. In this neuroimaging experiment, subjects controlled a circle with a mouse while requested either to lead another circle (i.e., being the agent) or to follow it (i.e., being acted upon). Clusters within the right intraparietal sulcus were associated with following for the most rostral and leading for the most caudal ones. Bilateral activity in the inferior parietal lobule in conditions involving confusion about the origin of the action confirmed its role in agency. A lateralization effect was also found in these conditions, the response being stronger in the left inferior parietal lobule when subjects were not the agent of the performed action, and in the right when they were.
TL;DR: This P3a/P3b response system appears to reflect the co-ordinated action of prefrontal and posterior association cortices during the switching and updating of task sets in working memory.
Abstract: Cognitive £exibility hinges on a readiness to direct attention to novel events, and on an ability to change one’s mental set to ¢nd new solutions for old problems. Human event-related potential (ERP) studies have described a brain‘orienting’ response to discrete novel events, marked by a frontally distributed positive potential peaking 300^ 400 ms post-stimulus (P3a). This brain potential has been typically related to bottom-up processing of novel non-targets under a ¢xed task-set (i.e., press a button to coloured targets), but had never been related to top-down attention control in dual-task paradigms. In this study, 27 subjects had their ERPs measured while they performed a version of the Wisconsin card sorting test (WCST), a dual-task paradigm where the same feedback cue signalled unpredictable shifts to a new task set (i.e., from ‘sort by colour’ to ‘sort by shape’).Feedback cues that directed a shift in the subject’s mental set to a new task-set elicited frontally distributed P3a activity, thus suggesting a role of the P3a response system in task-set shifting. Feedback cues also evoked a longer latency positive potential (350^ 600 ms; P3b), that was larger the more task rules were held in memory. In line with current models of prefrontal function in the executive control of attention, this P3a/P3b response system appears to re£ect the co-ordinated action of prefrontal and posterior association cortices during the switching and updating of task sets in working memory. NeuroReport 13:1887^1892 � c 2002 Lippincott Williams & Wilkins.
TL;DR: The results suggest that extrastriate mechanisms mediating these thresholds normally develop in parallel, but that the dorsal stream has a greater, general vulnerability to early neurological impairment.
Abstract: Form and motion coherence thresholds can provide comparable measures of global visual processing in the ventral and dorsal streams respectively. Normal development of thresholds was tested in 360 normally developing children aged 4-11 and in normal adults. The two tasks showed similar developmental trends, with some greater variability and a slight delay in motion coherence compared to form coherence performance, in reaching adult levels. To examine the proposal of dorsal stream vulnerability related to specific developmental disorders, we compared 24 children with hemiplegic cerebral palsy with the normally developing group. Hemiplegic children performed significantly worse than controls on the motion coherence task for their age, but not on the form coherence task; however, within this group no specific brain area was significantly associated with poor motion compared to form coherence performance. These results suggest that extrastriate mechanisms mediating these thresholds normally develop in parallel, but that the dorsal stream has a greater, general vulnerability to early neurological impairment.
TL;DR: Results show a strong predisposition of humans to imitate somebody else's oculomotor behaviour, even when detrimental to task performance, likely linked to a strong tendency to share attentional states of other individuals, known as joint attention.
Abstract: In this study we investigated the tendency of humans to imitate the gaze direction of other individuals. Distracting gaze stimuli or non biological directional cues (arrows) were presented to observers performing an instructed saccadic eye movement task. Eye movement recordings showed that observers performed less accurately when the distracting gaze and the instructed saccade had opposite directions, with a substantial number of saccades matching the direction of the distracting gaze. Static (Experiment 1) and dynamic (Experiment 2) gaze distracters, but not pointing arrows (Experiment 3), produced the effect. Results show a strong predisposition of humans to imitate somebody else's oculomotor behaviour, even when detrimental to task performance. This is likely linked to a strong tendency to share attentional states of other individuals, known as joint attention.
TL;DR: The results suggest that imperceptible electrical noise, when applied to the knee, can enhance the balance performance of healthy older adults and suggest that electrical noise-based devices may be effective in improving balance control in elderly people.
Abstract: Somatosensory information is critical to balance control and fall prevention in older adults. Recently, it has been shown that lowlevel input noise (electrical or mechanical) can enhance the sensitivity of the human somatosensory system. In this study, we tested the eiect of low-level electrical noise, applied at the knee, on balance control in 13 healthy elderly volunteers. Subjects performed multiple single-legged stance trials with imperceptible electrical noise applied at the knee during half of the trials. Balance performance was characterized using a force platform to measure the displacement of the center of pressure (COP) under the subject’s stance foot. Seven sway parameters were extracted from the COP time series. Improved balance was de¢ned as a reduction in postural sway as indicated by decreases in the COP measures. Six of the seven sway parameters decreased with electrical noise. Three of these parameters decreased signi¢cantly (po 0.05), and a fourth parameter was borderline signi¢cant. Averaged across subjects, the application of electrical noise resulted in a 3.8% reduction in mediolateral COP standard deviation (p ¼ 0.04), a 5.4% decrease in the maximum anteroposterior COP excursion (p ¼ 0.03), a 3.1% reduction in the COP path length (p ¼ 0.04), and a 7.8% decrease in swept area (p ¼ 0.05). The results suggest that imperceptible electrical noise, when applied to the knee, can enhance the balance performance of healthy older adults. These ¢ndings suggest that electrical noise-based devices may be eiective in improving balance control in elderly people. NeuroReport 13:1853^1856 � c 2002 Lippincott Williams & Wilkins.