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Biomedical subjects

A M Barrett

Publications and source records attributed to A M Barrett.

At least 19 recordsLinked to original sources
PubMed2002

The Gerstmann syndrome in Alzheimer's disease.

BACKGROUND: It remains unclear from lesion studies whether the four signs of the Gerstmann syndrome (finger agnosia, acalculia, agraphia, and right-left confusion) cluster because the neuronal nets that mediate these activities have anatomical proximity, or because these four functions share a common network. If there is a common network, with degeneration, as may occur in Alzheimer's disease, each of the signs associated with Gerstmann's syndrome should correlate with the other three signs more closely than they correlate with other cognitive deficits. METHODS: Thirty eight patients with probable Alzheimer's disease were included in a retrospective analysis of neuropsychological functions. RESULTS: The four Gerstmann's syndrome signs did not cluster together. Finger naming and calculations were not significantly correlated. Right-left knowledge and calculations also did not correlate. CONCLUSIONS: The four cognitive functions impaired in Gerstmann's syndrome do not share a common neuronal network, and their co-occurrence with dominant parietal lobe injuries may be related to the anatomical proximity of the different networks mediating these functions.

Adult↗
PubMed2001

Seeing trees but not the forest: limited perception of large configurations in PD.

OBJECTIVE: To learn if Parkinson's disease (PD) is associated with a restricted attentional "floodlight." BACKGROUND: Different visual tasks may have different attentional requirements. Focused attention may be needed for some tasks; other tasks demand spatially distributed attention. Neglect after right cortical injury and dopamine depletion may limit the area over which attention can be spread. Although subjects with PD have dopamine depletion and can perform poorly on tests of visuospatial function, it is unclear if their attentional floodlight is restricted. METHODS: Eleven subjects with PD and 11 control subjects viewed different-sized letters on five printed stimulus sheets, 43 x 56 cm. On each sheet, four different large letters (14 cm2) were composed of four different medium-sized letters (2.5 cm2), which in turn were composed of four different small letters (0.4 cm2). Stimulus sheets were presented at 30- and 75-cm viewing distances. Subjects named "all the letters they could see." RESULTS: Subjects with PD named small- and medium-sized letters comparably to control subjects, but PD subjects named fewer large letters than control subjects (control = 65.68%, PD = 24.55%; group-by-letter-size interaction, p < 0.05). Subjects with PD who had undergone stereotactic pallidotomy named more letters than prepallidotomy PD subjects (p = 0.05). CONCLUSIONS: PD may affect the patient's ability to perceive large spatial configurations. As global configurations in subjects may be perceived preferentially over local patterns, it is possible that DA depletion induces an aberrant perceptual-attentional bias, such that patients have a narrowed attentional floodlight.

Aged↗
PubMed2001

Emotional conversations in Parkinson's disease.

OBJECTIVE: To learn how PD influences verbal description of emotional events. BACKGROUND: Individuals with PD exhibit emotional processing deficits. Emotional experience likely involves several dimensions (e.g., valence, arousal, motor activation) subserved by a distributed modular network involving cortical, limbic, basal ganglia, diencephalic, and mesencephalic regions. Although the neurodegeneration in PD likely affects components in this network, little is known about how PD influences emotional processing. Because PD is associated with activation deficits, one could predict that the discourse of emotional experiences involving high activation would be reduced in patients with PD compared to control subjects. Alternatively, because patients with PD exhibit paradoxical sensitivity to externally evoked motor activation (kinesia paradoxica), it is possible that emotional stimuli may facilitate verbal emotional expression more so in patients with PD than in control subjects. METHODS: The authors measured verbal descriptions of personal emotional experiences in subjects with PD and normal controls. RESULTS: Compared with control subjects, individuals with PD showed a relative increase in the number of words spoken and in discourse duration when talking about emotional experiences that are usually associated with high levels of arousal and motor activation. Although the authors did not measure arousal or activation, prior research has shown that, when asked to recall an emotional experience, people will often re-experience the emotion previously experienced during that episode. CONCLUSIONS: Recalling emotional episodes induces verbal kinesia paradoxica in patients with PD. Although recall of these emotional episodes may have been associated with increased arousal and activation, the mechanism underlying emotional verbal kinesia paradoxica is unclear.

Aged↗
PubMed2001

Monocular patching may worsen sensory-attentional neglect: a case report.

To determine whether monocular patching influences the performance of a patient with primarily sensory-attentional bias on the line bisection task, we present a case study of a 49-year-old woman who had right cortical infarction affecting temporal, parietal, and occipital regions. She had primarily sensory-attentional bias when performing the line bisection task on a video apparatus. In hospital, she was tested with monocular eye patching of the left or the right eye or unpatched. Paradoxically, the right-eye patching significantly worsened and the left patch significantly improved performance. The eye may have some input to the ipsilateral as well as the contralateral superior colliculus. Alternatively, the patch-a novel tactile stimulus-may induce orienting to its side via noncollicular mechanisms. When using a monocular patch for any reason, clinicians should be aware that increased spatial bias may occur.

Analysis of Variance↗
PubMed2001

The influence of congenital heart disease on survival of infants with oesophageal atresia.

OBJECTIVE: To examine the prevalence of congenital heart disease in babies with oesophageal atresia and its influence on outcome. DESIGN: Retrospective analysis. SETTING: The resident population of one health region. RESULTS: A total of 153 babies with oesophageal atresia were identified from 509 975 live births (0.30 per 1000); 26 (17%) had cardiac defects. Survival of babies with normal hearts was 97%, 97%, and 95% at one week, one month, and one year. Survival of babies with congenital heart disease was 85%, 85%, and 67% at one week, one month, and one year, but only one of ten deaths was the result of the congenital heart disease. The remaining deaths were due to other congenital malformations, respiratory disease, or chromosome abnormalities. CONCLUSIONS: There is a high prevalence of congenital heart disease in babies with oesophageal atresia. Congenital heart disease is associated with a higher mortality in oesophageal atresia but it is not the cause of it.

Cause of Death↗
PubMed2000

Proprioception more impaired distally than proximally in subjects with hemispheric dysfunction.

Holmes noted that with hemispheric injuries proprioceptive disturbances were more marked in the distal than proximal limb segments and proposed that this difference was related to the size of cortical sensory representations. An alternative hypothesis is that sensation from distal segments projects to the contralateral hemisphere and sensation from proximal segments projects to both hemispheres. Selective hemispheric anesthesia was used to test these alternative hypotheses and revealed a decrement in distal but not proximal proprioception with hemispheric anesthesia, thereby supporting the bilateral projection hypothesis.

Arm↗
PubMed2000

Increased discrimination of "false memories" in autism spectrum disorder.

Individuals with autism spectrum disorder (ASD) have impaired ability to use context, which may manifest as alterations of relatedness within the semantic network. However, impairment in context use may be more difficult to detect in high-functioning adults with ASD. To test context use in this population, we examined the influence of context on memory by using the "false memory" test. In the false memory task, lists of words were presented to high-functioning subjects with ASD and matched controls. Each list consists of words highly related to an index word not on the list. Subjects are then given a recognition test. Positive responses to the index words represent false memories. We found that individuals with ASD are able to discriminate false memory items from true items significantly better than are control subjects. Memory in patients with ASD may be more accurate than in normal individuals under certain conditions. These results also suggest that semantic representations comprise a less distributed network in high-functioning adults with ASD. Furthermore, these results may be related to the unusually high memory capacities found in some individuals with ASD. Research directed at defining the range of tasks performed superiorly by high-functioning individuals with ASD will be important for optimal vocational rehabilitation.

Adult↗
PubMed2000

Testing memory for self-generated items in dementia: method makes a difference.

OBJECTIVE: To learn how pAD (probable Alzheimer's disease), PD+ ("Parkinson's Plus" syndrome), and control subjects remember internally generated material under different conditions. BACKGROUND: "Self-discovered," or internally generated knowledge, prized by educators and therapists, can bring about considerable behavioral change. Both parietal-temporal-limbic (pAD) and frontal-subcortical dementia (e.g. PD+) cause dysmemory, but may cause different internal-external memory bias. pAD subjects, confusing internal and external information (confabulation) and reporting internal information during memory testing (intrusions), may be biased to remember internal material. PD+ subjects, impaired at generative tests, may be externally biased. METHODS: Ten pAD, 5 PD+, and 10 control subjects generated words in a category without instruction to remember (INR), and took a list-learning test of incidental memory for internally and externally generated words. To test how INR influences memory, subjects then generated and attempted to recall four more words. RESULTS: All three subject groups remembered more internally generated than externally provided words without INR. Recall versus recognition of internally generated words differed by group, with PD+ subjects showing greatest improvement with recognition. The pAD subjects performed worse with INR than without INR, had the most intrusion errors, and, rather than demonstrating a release from proactive inhibition, recalled fewer words outside the category. Groups differed in overall recall/recognition improvement (p = 0.015). CONCLUSIONS: Aged subjects preferentially retained internally generated material. However, among demented subjects, memory for internally generated words was influenced by the testing method used. PD+ subjects have poor internal recall, but excellent internal recognition. In pAD, memory for internally generated words may exceed external memory, but only when subjects are not explicitly trying to remember.

Aged↗
PubMed2000

Esophageal atresia in the Northern Region Congenital Anomaly Survey, 1985-1997: prenatal diagnosis and outcome.

OBJECTIVE: This study was undertaken to determine the rate of prenatal diagnosis and surgical outcome of all cases of esophageal atresia reported to the Northern Region Congenital Anomaly Survey. STUDY DESIGN: A retrospective review was conducted on maternal and infant case notes of all cases of esophageal atresia in the Northern Region from 1985-1997, inclusive. RESULTS: A total of 176 cases of esophageal atresia was reported, and 158 diagnoses were confirmed after birth. Six cases were excluded because of incomplete data. Among the 32 patients in whom esophageal atresia was suspected antenatally because of an absent stomach bubble and hydramnios, 14 (44%) had esophageal atresia confirmed postnatally. In 10 of the 18 patients with false-positive diagnoses the stomach was subsequently seen. Esophageal atresia should have been suspected prenatally in a further 38 patients with polyhydramnios, 3 of whom also had an absent stomach bubble. There were 12 pregnancy terminations, 1 spontaneous abortion, and 19 perinatal deaths (including 9 stillbirths). Among the patients with esophageal atresia, 63.2% had associated anomalies (including 5.3% with aneuploidy), and 78.4% of these anomalies were missed prenatally. Among the live births 21.5% of the infants had a birth weight below the 5th percentile. One hundred eight (90%) had esophageal atresia with a distal tracheoesophageal fistula, and overall 102 (85%) underwent a primary repair. Among the 120 infants who underwent surgical treatment 11 subsequently died, and 6 of these deaths were related to postoperative complications. Thirty-nine infants (32.5%) had postoperative gastroesophageal reflux, necessitating fundoplication in 21 cases. At 2-year follow-up 23 of 89 infants had dysphagia, for which 7 still required a gastrostomy or jejunostomy. Infants in whom the condition was diagnosed prenatally were more likely to need prolonged mechanical ventilation, to have a longer hospital stay, and to have long-term gastrointestinal problems. CONCLUSIONS: Most cases of esophageal atresia are not suspected prenatally. Among fetuses with ultrasonographic features suggestive of esophageal atresia, 50% have the disorder confirmed postnatally. Overall perinatal and infant mortality rate among those with esophageal atresia is high (21.6%), and a further 21% of affected infants have significant morbidity after the age of 2 years.

Birth Weight↗
PubMed2000

Emotional and physiological responses to false feedback.

The relationship between autonomic-visceral arousal and emotional experience is unclear. The attribution or cognitive-arousal theory of emotional experience posits that emotional experience is dependent on both visceral-autonomic nervous system feedback and the cognitive interpretation of the stimulus that induced this visceral activation. The finding that false cardiac feedback can alter emotional experience suggests that it may be the conscious perception that one is aroused, together with the cognitive interpretation of the stimulus that are important in developing emotional experience. Because the right hemisphere appears to play a special role in modulating arousal and interpreting emotional stimuli, it is possible that right hemisphere damage may interfere with developing the computations needed for emotional experience. To test this hypothesis we exposed men, both neurologically intact and those with right and left hemisphere lesions, to emotionally provocative pictures that were paired with false cardiac feedback, and examined the effects of this false feedback on their ratings of attractiveness of these pictures and their cardiac reactivity to this information. Subjects with left hemisphere damage, but not right hemisphere damage, showed significant changes in their emotional rating whereas control subjects showed marginal reactivity in their emotional ratings. Subjects with left hemisphere damage also showed significant changes in their cardiac reactivity. This finding is consistent with prior reports that indicate, when compared to right hemisphere damaged patients and normal controls, patients with left hemisphere lesions have an increased visceral-autonomic response to stimuli. These findings further provide support for the postulate that it is the cognitive interpretation of perceived physiological arousal together with the cognitive interpretation of the stimulus that is important in the development of emotional judgment and experience. These results do not support the approach-left hemisphere/avoidance-right hemisphere dichotomy, but instead suggest that left hemisphere damage increases reactivity to false feedback, and that the intact right hemisphere function integrates the cognitive interpretation of the emotional information and perceived arousal that lead to that emotional judgment. That these subjects showed no consistent relationship between their measures of cardiac reactivity and their ratings of attractiveness detracts from the James-Lange and attribution theories. These subjects also showed no consistent relationship between their knowledge of affective physiological reactivity and their ratings of attractiveness, or between their knowledge of physiological reactivity and actual measures of cardiac reactivity, suggesting that other neuropsychological factors are involved in making an emotional judgment.

Aged↗
PubMed2000

Cognitive and vestibulo-proprioceptive components of spatial ability in Parkinson's disease.

Visual-spatial deficits are often associated with Parkinson's Disease (PD). Recent theories suggest that frontal-basal ganglionic dysfunction affects cognition in PD. Although this hypothesis does not entirely explain spatial deficits in PD, the inappropriate utilization of cues associated with executive dysfunction may induce spatial deficits. Alternatively, the vestibular system is also involved in spatial cognition, and vestibular dysfunction may affect visual-spatial ability in PD. To test these hypotheses, we administered the Water Jar Test, while perturbing vestibulo-proprioceptive input. Non-demented PD patients were significantly less accurate than controls in judging horizontal, and appeared to inappropriately utilize cues. No group effect was found for head tilt. These findings suggest the visual-spatial difficulties seen in PD are related to executive dysfunction that is associated with a disruption of the frontal-basal ganglionic and frontal-parietal systems.

Basal Ganglia↗
PubMed2000

Attentional grasp in far extrapersonal space after thalamic infarction.

Studies of animals and humans with focal brain damage suggest that attention in near and far extrapersonal space may be mediated by anatomically separate systems. Thalamic lesions have been associated with spatial neglect, but whether asymmetric attention specific to near or far space occur after thalamic damage has not been explored. It is also unclear if thalamic injury can induce contralesional defective response inhibition. We tested a woman with a left thalamic infarction who reported that, when driving, she had a tendency to veer towards people or objects on the right side of the road. Our patient and four controls performed a line bisection task with a laser pointer in near and far extrapersonal space. The experimenter marked each bisection either from the right of the presented line (right-distractor, RD) or the left (left-distractor, LD). RD and LD trials were pseudo-randomized. Our patient performed similarly to controls (mean -0.7 mm, controls -0.6 mm) on the line bisection task in near space. In far space she erred significantly rightward compared to her performance in near space (p<0.001). Controls performed similarly in near and far space. The experimenter position did not affect our patient's performance on near line bisections, nor did controls demonstrate a distractor effect for the near condition. In the far condition, however, our patient showed a significant distractor effect (LD -3.3 mm, RD 35.3 mm, p<0.001). Controls also demonstrated a distractor effect in the far condition (LD -6.4 mm, RD 0.7 mm, p<0.01), though of much smaller magnitude. Our results suggest that frontal-thalamic systems regulating visual attention may be disrupted by thalamic infarction. Such damage may produce an attentional grasp specific to far extrapersonal space.

Attention↗
PubMed2000

Horizontal line bisections in upper and lower body space.

Whereas the ventral cortical visual stream is important in object recognition, the dorsal stream is specialized for spatial localization. In humans there are also right and left hemisphere asymmetries in visual processing: the left hemisphere being more important in object recognition and the right in specifying spatial locations. Based on these dorsal-ventral and right-left where-what dichotomies, one would expect that the dorsal right hemisphere systems would be most activated during spatial localization tasks, and this activation may induce a leftward spatial bias in lower space. To determine if visual stimuli in upper and lower body space evoke different hemispheric activation, we had 12 normal participants bisect horizontal lines above and below eye level. Participants erred leftward in lower body space relative to upper body space (M = 1.3345 mm and 0.4225 mm, respectively; p = .011). In upper body space, bisection errors did not differ from zero, but in lower body space, errors tended to deviate leftward (M = 1.3345 mm, differs from null hypotheses at p = .0755). Our results are consistent with dorsal stream/right hemisphere activation when performing a spatial localization task in lower versus upper body space.

Adult↗
PubMed2000

Dissociation of anosognosia and phantom movement during the Wada test.

OBJECTIVE: Patients who misperceive that they are moving their paralysed arm (phantom movements) may not recognise its weakness. Therefore, the relation between phantom limb movements and anosognosia for hemiplegia during selective right hemispheric anaesthesia (the Wada test) was examined. METHODS: Nine patients with intractable epilepsy underwent the Wada test. During the right hemispheric injection, after the onset of hemiparesis, anosognosia was assessed by asking patients if they were weak. The patient's vision was limited such that they could not see the position of their limbs. Phantom movements were tested for by asking patients to attempt to lift their left upper limb, and to demonstrate their left limb's position by placing their right limb in the same position as their left. Proprioception was tested by lifting the patient's paretic upper limb and having patients demonstrate this position by lifting their right limb to the same position. RESULTS: Three patients experienced left phantom limb movements, and five were anosognosic for their hemiplegia. However, phantom movement occurred in only one patient with anosognosia. The other two patients with phantom movement were without anosognosia. The patient with phantom movement and anosognosia had impaired proprioception. The two patients with phantom movement but without anosognosia had intact proprioception. CONCLUSIONS: Phantom movement in the presence of a proprioceptive deficit could contribute to anosognosia. However, anosognosia and phantom movement are dissociable; therefore phantom movement cannot alone account for anosognosia. Because phantom movement occurred with and without proprioceptive deficits, proprioceptive loss is not a prerequisite for phantom movement.

Adult↗
PubMed1999

Ipsilesional intentional neglect and the effect of cueing.

BACKGROUND: Contralesional hemispatial neglect may be induced by an attentional deficit where patients are inattentive to or unaware of stimuli in contralesional hemispace, an intentional deficit where patients are unable to act in or towards contralesional hemispace, or both. The deficits associated with ipsilesional neglect have not been as well characterized. Because cueing may be used as a rehabilitative assistive device, we wanted to learn whether the efficacy of an attentional or intentional cue was related to the type of bias. METHODS: We studied a patient with a right frontotemporal stroke who had ipsilesional neglect by using a video apparatus that dissociates sensory-attentional and motor-intentional systems. We also performed a cueing experiment with primarily sensory-attentional cues (i.e., read the letter at the end of the line) and primarily motor-intentional cues (i.e., touch the end of the line). RESULTS AND CONCLUSIONS: Ipsilesional neglect was primarily a motor-intentional deficit with a motor-action bias to the left and a secondary sensory-attentional bias for stimuli to the right. With cueing we found a double dissociation: the rightwards motor-intentional cue improved the primary left-sided intentional bias and the leftwards sensory-attentional cue improved the secondary right-sided attentional bias. Effective rehabilitation strategies need to address both sensory-attentional and motor-intentional deficits in patients with neglect.

Attention↗