Posture recognition in Alzheimer's disease

BACKGROUND: Apraxia is neurologically induced deficit in the ability perform purposeful skilled movements. One of the most common forms is ideomotor apraxia (IMA) where spatial and temporal production errors are most prevalent. IMA can be associated Alzheimer's disease (AD), even early in its course, but is often not identified possibly because the evaluation of IMA by inexperienced judges using performance tests is unreliable. The purpose of this study, therefore, is to learn if the Postural Knowledge Test (PKT), a praxis discrimination test that assesses knowledge of transitive (PKT-T subtest) and intransitive (PKT-I subtest) postures and does not require extensive training, is as sensitive and specific as the praxis performance tests. METHODS: We studied 15 subjects with probable AD as well as 18 age-matched controls by having them perform transitive and intransitive gestures to command and imitation, as well as having them discriminate between correct and incorrect transitive and intransitive postures. RESULTS: Overall on all tests, the control subjects performed better than those with AD. In addition all subjects had more trouble with transitive than intransitive gestures. Using a stepwise discriminative analysis, 81.8% of the subjects could be classified according to Group (94.4% of Controls, 66.7% of AD subjects). In this analysis, the PKT-T (transitive posture subtest) was the only measure that contributed to the discrimination of subjects. CONCLUSION: We found that having subjects select the correct transitive hand postures in this "booklet test" was more sensitive than grading their praxis performances even when using judges with extensive training. This suggests that this discrimination test might be an excellent means for diagnosing and screening patients for AD. The reason why recognition of transitive postures is relatively more difficult for our AD subjects is not known. Two possibilities are that the representations for intransitive movements are stronger than those for transitive movements, and hence, more resistant to degradation, or that intransitive acts are stored in parts of the brain not affected by AD.     

What is the best strategy for retaining gestures in working memory?

This study aimed to determine whether the recall of gestures in working memory could be enhanced by verbal or gestural strategies. We also attempted to examine whether these strategies could help resist verbal or gestural interference. Fifty-four participants were divided into three groups according to the content of the training session. This included a control group, a verbal strategy group (where gestures were associated with labels) and a gestural strategy group (where participants repeated gestures and were told to imagine reproducing the movements). During the experiment, the participants had to reproduce a series of gestures under three conditions: “no interference”, gestural interference (gestural suppression) and verbal interference (articulatory suppression). The results showed that task performance was enhanced in the verbal strategy group, but there was no significant difference between the gestural strategy and control groups. Moreover, compared to the “no interference” condition, performance decreased in the presence of gestural interference, except within the verbal strategy group. Finally, verbal interference hindered performance in all groups. The discussion focuses on the use of labels to recall gestures and differentiates the induced strategies from self-initiated strategies.     

Imagery and verbal encoding in left and right hemisphere damaged patients

Neuropsychological aspects of imaginal and verbal encoding in memory were explored in two forced-choice recognition memory experiments with patients suffering from left and right anterior cerebral hemisphere damage. In the first experiment stimulus type and rate of presentation were varied. Predictions of patient performance based on the hypothesis that left anterior hemisphere pathology impairs verbal memory coding and right anterior hemisphere pathology impairs imaginal coding were confirmed. In a second recognition memory experiment for pictures of common objects, system-specific (imaginal or verbal) interference and distractor effects were demonstrated by analyzing the effects of interpolated tasks and the nature of false-recognition errors.     

The different types of limb apraxia errors made by patients with left vs. right hemisphere damage

Limb apraxia errors were compared among normal controls and right- or left-hemisphere-damaged patients as they imitated gestures with the ipsilateral hand. Both brain-damaged groups made similar errors on nonrepresentative and representative/intransitive movements. In contrast for pretended object use movements (transitive), the left-hemisphere-damaged group made more arm position and classical body-part-as-object errors while the right hemisphere group made as many partial errors and more less-primitive, body-part-as-object errors than the left-hemisphere-damaged group. These results help explain why a certain percentage of right-hemisphere-damaged patients are labeled apraxic, but also suggest that the left hemisphere is more important for integrating intrapersonal space and the “representation” of extrapersonal space.     

MANUAL ACTIVITY DURING SPEAKING IN APHASIC SUBJECTS*

Samples of free conversations were recorded in 6 normal and 12 aphasic subjects. Manual activity during speech was observed. Groups were shown to behave in an opposite way for the verbal and nonverbal measures: while aphasic subjects' verbal behavior is impaired, they produce more speech-related movements than normals. No differences appear concerning other movements (automanipulation, hand-to-hand posture, miscellaneous movements). Analysis of the aphasie group reveals no difference between the fluent and the nonfluent aphasies. Verbal fluency is shown to be a non-critical factor in the explanation of gesture production. Increased gestural production in aphasies may be interpreted according to the hypothesis that gestures are cues for the difficulties the speaker experiences in the verbal encoding process.     

An investigation of body part as object (BPO) responses in normal and brain-damaged adults

A test of simple pantomime was administered to three groups of adults and comparisons were made across groups of the incidence of subjects who exhibited body part as object (BPO) responses and of the mean frequency of occurrence of BPO in each group. The three groups were left-hemisphere-damaged aphasics (N = 28), right-hemisphere-damaged (N = 24), and normal controls (N = 28). The results indicated no significant differences among groups on the BPO measures. Also, to test the strength of association between the frequency of occurrence of BPO and measures of limb apraxia and severity of aphasia for the left-hemisphere-damaged aphasic group, correlation coefficients were obtained. The correlations were low and nonsignificant. The results of this investigation do not support the common clinical assumption that the occurrence of BPO during the performance of simple pantomimes is pathognomic for left-hemisphere pathology or associated with limb apraxia.     

Impairments of nonverbal oral movements after left hemisphere damage: A followup analysis of errors

Acquisition of a task requiring the imitation of a series of nonverbal oral movements is most severely impaired in patients with aphasic disturbance. However, nonaphasic patients with left hemisphere damage also perform more poorly than patients with right hemisphere damage or normal control subjects. Analysis of the errors made on the multiple oral movements task reveals that left, but not right, hemisphere damage is highly associated with perseverative responses. Patients with right hemisphere damage do not differ significantly from normal control subjects in the acquisition of or in the type of errors made on the task. It is suggested that the left hemisphere plays an important role in the control of nonverbal oral movement production.     

Verbal mediation and memory for novel figural designs: a dual interference study

To the extent that all types of visual stimuli can be verbalized to some degree, verbal mediation is intrinsic in so-called "visual" memory processing. This impurity complicates the interpretation of visual memory performance, particularly in certain neurologically impaired populations (e.g., aphasia). The purpose of this study was to investigate the relative contributions of verbal mediation to recognition memory for visual stimuli that vary with respect to their amenability to being verbalized. In Experiment 1, subjects attempted to verbally describe novel figural designs during presentation and then identify them in a subsequent recognition memory test. Verbalizing these designs facilitated memory. Stimuli that were found to be easiest or most difficult to verbalize at the group level were retained for the second study. In Experiment 2, subjects evidenced superior recognition memory for the relatively easy to verbalize items. This advantage was attenuated in subjects who performed a concurrent verbal interference task during encoding, but not in those who performed an analogous visual interference task. These findings provide evidence that impoverished verbal mediation disproportionately impedes memory for visual material that is relatively easy to verbalize. Implications for the clinical assessment of visual memory are discussed.     

Should I fetch one or the other? A study on dogs on the object choice in the bimodal contrasting paradigm

The present study assessed how dogs weigh gestural versus verbal information communicated to them by humans in transitive actions. The dogs were trained by their owners to fetch an object under three conditions: a bimodal congruent condition characterized by using gestures and voices simultaneously; a unimodal gestural condition characterized by using only gestures; and a unimodal verbal condition characterized by using only voices. An additional condition, defined as a bimodal incongruent condition, was later added, in which the gesture contrasted with the verbal command, that is, the owner indicated an object while pronouncing the name of the other object visible to dogs. In the incongruent condition, seven out of nine dogs choose to follow the gestural indication and performed above chance, two were at chance, whereas none of the dogs followed the verbal cues above chance. The dogs, as a group, performed above chance the gestural command in 73.6% of cases. The analysis of latencies in the above-mentioned four conditions exhibited significant differences. The unimodal verbal and the gestural conditions recorded a slower performance than both the bimodal incongruent and congruent conditions. No statistical differences were observed between the unimodal and bimodal conditions. Our results demonstrate that dogs, trained to respond equally well to gestural and verbal commands, choose to follow the indication provided by the gestural command than the verbal one to a significant extent in transitive actions. Furthermore, the responses to bimodal conditions were found to be quicker than the unimodal ones.     

Error Analysis of Limb and Orofacial Praxis in Children with Developmental Motor Deficits

Two models have been suggested to depict the relationship between disorders of limb and orofacial praxis. The first views apraxia as a unitary disorder in which the underlying mechanisms for each type are similar, while the second model suggests that there are two separate praxis systems: one for planning and controlling limb gestures and a second one for planning and controlling orofacial movements. The purpose of this study was to investigate whether a common mechanism may underlie deficits in limb and orofacial praxis in children. This was done by analyzing the types of praxis errors demonstrated by children with developmental motor deficits and normal controls when performing limb and orofacial gestures. Results indicated that there was consistency across modalities (i.e., limb, orofacial) in the types of praxis errors made by children with motor deficits, providing support for the idea that a common mechanism may underlie disruptions to limb and orofacial praxis in children. This study also examined developmental trends in gestural representation and in types of praxis errors. The findings revealed a striking developmental maturation in gestural ability between the ages of 6 and 11 years for all children. However, over this age range, children with developmental motor deficits were impaired relative to normal controls.     

Apraxia in corticobasal degeneration.

Corticobasal degeneration (CBD) is a degenerative disease that often presents with an asymmetric progressive ideomotor limb apraxia. Some apraxic subjects may fail to perform skilled purposive movements on command because they have lost the memories or representations that specify how these movements should be performed (representational deficit). In contrast, other apraxic subjects may have the movement representations but are unable to utilize the information contained in them to execute skilled purposive movements (production-execution deficit). To learn if the apraxic deficit in CBD is induced by a representational or a production-execution deficit, we tested three nondemented subjects with CBD on tasks requiring production of meaningful or meaningless gestures to command, gesture imitation, gesture discrimination, and novel gesture learning. A fourth subject with incomplete data also is presented. The results suggest that the apraxia associated with CBD is initially induced by a production-execution defect with relative sparing of the movement representations.     

EMPLOYING TASK ARRANGEMENTS AND VERBAL CONTINGENCIES TO PROMOTE VERBALIZATIONS BETWEEN RETARDED CHILDREN1

This study investigated the effects of arranging task events for interdependence, to increase the probability of social responding. During task interdependence, the subjects, participating in dyads and a four-person group, obtained task materials (a puzzle piece) from their partner before completing their task (appropriately placing the puzzle piece). The verbal contingency required a verbal request to precede a subject's receiving a task material from his partner. The verbal contingency yoked with task interdependence made task completion contingent on the appropriate verbalization. The findings from two experiments suggested that task interdependence was sufficient to increase partner-directed verbalizations for three of the four subjects. When the verbal contingency was added, all subjects increased their requests and other verbalizations to partner. Applied to a four-person group, the verbal contingency yoked with varying levels of task interdependence correspondingly affected the pattern and level of group communications. The greater the task interdependence, i.e., the more members each subject depended on to complete his task, the more complex the social network of verbal contacts, and the higher the level of both requests and other verbalizations for the group.     

Individual differences in cognition: Some relationships between personality and memory

Individual differences in cognition were studied in the form of the hypothesis that arousal, as indexed by personality measures of extraversion and neuroticism, affects the way in which verbal material is organized in memory. Subjects pretested on measures of these personality variables participated in either a paired-associates learning or a free-recall experiment. On the paired-associates task, subjects who were thought to be high on arousal made fewer errors when response terms were semantically similar than low arousal subjects. On the other hand, subjects thought low on arousal made fewer errors when response words were phonetically similar than high arousal subjects. On the free-recall task, low arousal subjects were found to cluster words together on the basis of semantic category at a higher rate than high arousal subjects. These results were taken to support the view that high arousal (as indexed by personality measures) leads to a focus on the physical aspects of verbal material, whereas low arousal leads to a memory organized around semantic aspects. The implications of these findings for other views of memory are discussed.     

Decisions concerning the rejected channel

It was thought that the physical aspects of auditory stimuli were possibly transmitted via separate pathways from those transmitting the verbal aspects. Three experiments were designed to test this hypothesis. In these experiments subjects had to perform a shadowing task and had to respond simultaneously on response keys to pips superimposed in either ear on verbal messages. The response to these pips was of increasing complexity, in that it was a simple reaction time which was measured in the first experiment, a choice reaction time in the second experiment and a more complex choice reaction time in the third experiment. Subjects were able to perform these tests although the increasing difficulty was reflected in longer reaction times and more errors. The reaction times to the pips presented to the ear which was not being shadowed were slower, and the errors, made to pips in both channels, were “false positives” rather than errors of omission. These results were taken as favouring the hypothesis.     

Division of the articulatory loop according to sensory modality using double dissociation

According to Wilson and Fox (2007), working memory for gestures has the same characteristics as the phonological loop. The purpose of our research was to determine whether there is a common articulatory loop for verbal and gestural learning. We carried out two double dissociation experiments. The first involved 84 participants who had to reproduce a series of three gestures under three conditions: control, gestural interference (repeated gestures) and verbal interference (repeated “blah blah”). A significant difference in performance was observed; gestural interference resulted in the weakest performance, while there was no difference between the verbal interference condition and the control group. The second experiment, with 30 participants, involved the memorisation of letters and digits; performance was significantly affected by verbal interference but there was no difference between the gestural interference condition and the control group. The consequences of the dissociations are discussed in relation to Baddeley's (2000) model.     

Apraxia differs in corticobasal degeneration and left-parietal stroke: A case study.

Corticobasal degeneration (CBD) is a progressive disorder characterized by both cortical and basal ganglia dysfunction such as asymmetrical apraxia, and akinetic rigidity, involuntary movements, and cortical sensory loss. Although apraxia is a key finding for the differential diagnosis of CBD, it has not been determined whether the features of apraxia seen in subjects with CBD are similar to those features exhibited by subjects with left-hemisphere damage from stroke. Therefore, for both clinical purposes and in order to better understand the brain mechanisms that lead to apraxia in CBD, we studied praxis in a patient with CBD and compared him to patients who are apraxic from left-parietal strokes. We used three-dimensional movement analyses to compare the features of apraxic movement. This subject with CBD was a dentist whose initial complaint had been that he "forgot" how to use his tools in the mouths of his patients. Analyses were performed on the trajectories made when using a knife to actually slice bread, and when repetitively gesturing slicing made to verbal command. Movements of the left hand, wrist, elbow, and shoulder were digitized in 3-D space. Although the CBD subject was clearly apraxic, the features of his apraxia differed markedly from those of the subjects with lesions in the left parietal lobe. For movements to command, the CBD subject showed joint coordination deficits, but his wrist trajectories were produced in the appropriate spatial plane, were correctly restricted to a single plane, and, like control subjects, were linear in path shape. However, when he was actually manipulating the tool and object, all of these aspects of his trajectories became impaired. In contrast, the deficits of the apraxic subjects with left-parietal damage were most pronounced to verbal command with their movements improving slightly although remaining impaired during actual tool and object manipulation. Unlike patients with parietal strokes, patients with CBD have degeneration in several systems and perhaps deficits in these other areas may account for the differences in praxic behavior.     

Functional cerebral lateralization in subtypes of disabled readers

This study investigated the functional cortical organization of reading-disabled boys and age-matched normal readers. Subjects were initially classified according to E. Boder's (1971a. In B. Bateman (Ed.), Learning disorders. Seattle: Special Child Publications. Vol. 4.) distinction between dysphonetic children (who make nonphonetic, bizarre spelling errors), dyseidetic children (who make phonetically acceptable errors, but do not respond to some words as “wholes”), and children who display normal error patterns (who make phonetically acceptable errors and respond to words as “wholes”). It was hypothesized that different types of reading disability would be associated with different patterns of lateralized brain function. This proposal was examined by testing subjects on three experimental neuropsychological measures—hemispheric time-sharing, conjugate lateral eye movements, and tactile directional perception. Conjugate lateral eye movements were disregarded as the control subjects failed to show predicted asymmetries on this measure. The two other measures were considered valid and demonstrated atypical lateralization in the reading-disabled groups. Lateralization of verbal and/or spatial functiosn differed among the reading-disabled groups and an attempt was made to relate these atypical patterns to the type of reading difficulties presented.     

Effects of aging on source monitoring: differences in susceptibility to false fame

Older adults were less likely than young adults to spontaneously recollect the source of familiarity for previously read nonfamous names. Older adults were more likely to call old nonfamous names famous when subsequently encountered in a fame judgment task. Poor source monitoring by the elderly could not be accounted for by inability to recognize earlier read nonfamous names when specifically asked to do so. Both source-monitoring errors and recognition memory performance were based on attributions made about the experience of familiarity. Elderly subjects most prone to making familiarity errors recalled fewer items on a verbal learning task and were less likely to chunk information into semantic categories as it was recalled. This finding suggests that a decline in the tendency to spontaneously organize and integrate information underlies the poor source monitoring observed.     

A comparison of attentional and control shift models of the performance of concurrent tasks

A concurrent verbal task was superimposed upon the performance of a practiced bimanual motor skill by right-handed Ss. Addition of the verbal task did not increase the total number of errors; however, a significant interaction between hands and conditions was observed. The right hand made significantly more errors under the verbal condition, while the left hand made non-significantly fewer errors under that condition. These findings were interpreted as supporting an attentional model rather than a model which proposes that addition of the verbal task causes control of the right hand to shift to the non-verbal right hemisphere.     

Co-speech iconic gestures and visuo-spatial working memory

Three experiments tested the role of verbal versus visuo-spatial working memory in the comprehension of co-speech iconic gestures. In Experiment 1, participants viewed congruent discourse primes in which the speaker's gestures matched the information conveyed by his speech, and incongruent ones in which the semantic content of the speaker's gestures diverged from that in his speech. Discourse primes were followed by picture probes that participants judged as being either related or unrelated to the preceding clip. Performance on this picture probe classification task was faster and more accurate after congruent than incongruent discourse primes. The effect of discourse congruency on response times was linearly related to measures of visuo-spatial, but not verbal, working memory capacity, as participants with greater visuo-spatial WM capacity benefited more from congruent gestures. In Experiments 2 and 3, participants performed the same picture probe classification task under conditions of high and low loads on concurrent visuo-spatial (Experiment 2) and verbal (Experiment 3) memory tasks. Effects of discourse congruency and verbal WM load were additive, while effects of discourse congruency and visuo-spatial WM load were interactive. Results suggest that congruent co-speech gestures facilitate multi-modal language comprehension, and indicate an important role for visuo-spatial WM in these speech–gesture integration processes.