Revisiting a study of callosal apraxia: The right hemisphere can imitate the orientation but not the position of the hand

Callosal disconnection can reveal asymmetrical contributions of the two brain hemispheres to praxis. In this paper, we revisit a study of a patient with callosal disconnection (Goldenberg et al., 2001, Neuropsychologia, 39:1432-1443), who perfectly imitated meaningless gestures when imitation was controlled only by the left hemisphere, but was severely impaired when the right hemisphere was in charge of motor control. We decomposed the gestures into a set of geometric variables that were to be reproduced, such as the orientation of the hand and the position of contact between the hand and the face. Whereas orientation of the hand in extrinsic coordinates was replicated correctly by both hemispheres, only the left hemisphere reproduced correctly the position of contact between the hand and the face. This goal-dissociation as well as several partial perseveration errors speak against the hypothesis of a direct route from perception to motor replication of gestures, as interruption of a direct route would probably impair all the features of the gesture. We speculate that incorrect coordination between the reproductions of multiple goals may be the core deficit underlying callosal apraxia.     

The interplay between gesture and speech in the production of referring expressions: investigating the tradeoff hypothesis

The tradeoff hypothesis in the speech-gesture relationship claims that (a) when gesturing gets harder, speakers will rely relatively more on speech, and (b) when speaking gets harder, speakers will rely relatively more on gestures. We tested the second part of this hypothesis in an experimental collaborative referring paradigm where pairs of participants (directors and matchers) identified targets to each other from an array visible to both of them. We manipulated two factors known to affect the difficulty of speaking to assess their effects on the gesture rate per 100 words. The first factor, codability, is the ease with which targets can be described. The second factor, repetition, is whether the targets are old or new (having been already described once or twice). We also manipulated a third factor, mutual visibility, because it is known to affect the rate and type of gesture produced. None of the manipulations systematically affected the gesture rate. Our data are thus mostly inconsistent with the tradeoff hypothesis. However, the gesture rate was sensitive to concurrent features of referring expressions, suggesting that gesture parallels aspects of speech. We argue that the redundancy between speech and gesture is communicatively motivated.     

Social cues, mentalizing and the neural processing of speech accompanied by gestures

Body orientation and eye gaze influence how information is conveyed during face-to-face communication. However, the neural pathways underpinning the comprehension of social cues in everyday interaction are not known. In this study we investigated the influence of addressing vs. non-addressing body orientation on the neural processing of speech accompanied by gestures.While in an fMRI scanner, participants viewed short video clips of an actor speaking sentences with object- (O; e.g., shape) or person-related content (P; e.g., saying goodbye) accompanied by iconic (e.g., circle) or emblematic gestures (e.g., waving), respectively. The actor's body was oriented either toward the participant (frontal, F) or toward a third person (lateral, L) not visible.For frontal vs. lateral actor orientation (F > L), we observed activation of bilateral occipital, inferior frontal, medial frontal, right anterior temporal and left parietal brain regions. Additionally, we observed activity in the occipital and anterior temporal lobes due to an interaction effect between actor orientation and content of the communication (PF > PL) > (OF > OL).Our findings indicate that social cues influence the neural processing of speech-gesture utterances. Mentalizing (the process of inferring the mental state of another individual) could be responsible for these effects. In particular, socially relevant cues seem to activate regions of the anterior temporal lobes if abstract person-related content is communicated by speech and gesture. These new findings illustrate the complexity of interpersonal communication, as our data demonstrate that multisensory information pathways interact at both perceptual and semantic levels.     

Coverbal gestures in Alzheimer's type dementia

Patterns of conversational gestures were analysed in subjects with Alzheimer's type dementia (DAT), fluent aphasics with a primarily lexical-semantic deficit (FA) and normal subjects. The FA subjects produced twice as many gestures as the normal participants with a normal percentage of gestures that showed semantic features of the lexical items in concurrent speech (iconic). A comparable lexical-semantic deficit together with a deficit in conceptual organisation of information corresponded to a normal gesturing rate in the DAT subjects; however, the percentage of iconic gestures was reduced. Gestures were also analysed in four DAT patients whose communicative performance indicated primarily lexical-semantic (2 patients) or conceptual deficit (2 patients). In the two DAT patients with lexical-semantic deficit, the gesture pattern was like that of the FA patients; in the other two, the pattern of the DAT group was observed. These results agree with previous findings that DAT "empty" speech corresponds to reduced production of gestures showing semantic features (Glosser et al., 1998). However, the comparison between DAT with primarily lexical-semantic or conceptual deficits indicates that the nature of the cognitive impairment underlying poor information content and lack of reference in DAT discourse constrains the production of conversational gestures by patients with this disease. These findings are at variance with the hypothesis of parallel dissolution of speech and gestures in language disorders after brain damage (Cicone et al., 1979; McNeill, 1992; Glosser et al., 1998).     

How toddlers think with their hands: social and private gestures as evidence of cognitive self-regulation in guided play with objects

The role of language as a tool to support the self-regulation has been widely studied, yet there is little evidence on the role of prelinguistic communication in the early development of self-regulation. To address this gap, we developed behavioural indicators of preverbal cognitive self-regulation, and described how can parents support it through guided play. We observed 16 children at 14, 16 and 18 months interacting with two complex toys, either independently or with a parent. A microanalytic coding captured a total of 721 gestures, of which 473 were classed as self-regulatory. Children used gestures to support self-regulation in planning monitoring, control, and evaluation. Analysis of parental mediation revealed a relationship between supporting autonomy, providing challenge, responsiveness, effective communication, children’s competence with objects, and self-regulatory gestures. We produced reliable indicators of self-regulation through gestures and characterized effective parental mediation, thus making explicit key social mechanisms to foster self-regulation in preverbal development.     

Comprehension of conventional gestures in typical children,children with autism spectrum disorders and children with language disorders

Background

Conventional gestures (CG) contribute to communication and are a precursor of verbal language. The aim of our study was: (a) to analyse the developmental course of CG comprehension in typical children; (b) from a clinical perspective, to document how children with autism spectrum disorders (ASD) and language disorder (LD) can understand CG.

Scanning your body is different from performing body movements: A double dissociation between body representational neglect and apraxia

Body representational neglect (BRN) and apraxia can be found after left hemisphere (LH) lesions. Additionally, both disorders recruit knowledge about certain body parts, their position in space, and their spatial relationship to each other. Hence, the present study examined whether BRN and apraxia can be functionally dissociated at the behavioral and neural level. 23 LH lesioned patients were examined with a standardized body neglect test (Vest test) and a standardized test of apraxia (imitation of meaningless gestures). At the behavioral level BRN and apraxia showed a double dissociation. Moreover, these deficits were associated with specific brain lesions: while BRN was related to lesions in Brodmann areas 6 and 44 and frontal white matter, apraxia was linked to lesions in the superior longitudinal fasciculus and parietal and central white matter. The results are discussed as indicating dissociable representations of the human body within the left cerebral hemisphere.     

Productions corporelles dans les derniers stades de la maladie d’Alzheimer comme expression subjective ?

Objectives

Currently, the research on Alzheimer's focuses more on the neurological aspects than the psychological aspects of the disease. Even though its neurobiological basis is widely accepted, the psychical apparatus is affected greatly by this pathology. Since we know that for the patient, the words seem non-existent and the body does not have the capacity to respond, the clinical meeting can become a real challenge. The patient may shout, use imitative or stereotypic gestures, and the patient's behavior can become very confusing for the clinician. We are going to set up our hypothesis from these stereotypic gestures. We support and defend the idea that the patient intentionally sends us signals which mean something to the Other.

Hemispheric specialisation for imitation of hand-head positions and finger configurations: a controlled study in patients with complete callosotomy

Several studies of patients with unilateral brain damage and a patient with spontaneous callosal disconnection [Journal of Neurology, Neurosurgery, and Psychiatry 61 (1996) 176; Neuropsychologia 37 (1999) 559; Neuropsychologia 39 (2001) 1432] suggest that the imitation of positions of the hand relative to the head is a strongly lateralised left hemispheric function. In contrast, the imitation of finger configurations draws on resources of both hemispheres with a predominance of the right hemisphere. While these findings suggest a specific pattern of imitation impairment in split-brain patients, thus far, no imitation deficits have been reported in split-brain patients. Three patients with complete callosotomy and two control groups, four patients with partial callosotomy and 10 healthy subjects, imitated hand-head positions and finger configurations with non-lateralised and tachistoscopic stimulus presentation. In addition, the influence of visual control on the imitation performance was examined. One split-brain patient showed the predicted dissociation as she had severe right hemispheric deficit in imitating hand-head positions, while finger configuration imitation was preserved. The other two split-brain patients had no impairment in hand-head position imitation. Withdrawal of visual control significantly deteriorated imitation of finger configurations in the split-brain group, but not in the controls, demonstrating that the split-brain patients relied heavily on visual control as a compensatory strategy indicating an imitation deficit in the separate hemispheres. The findings question the previously held belief that in split-brain patients both hemispheres are perfectly capable of imitating gestures and that imitation is not dependent on hemispherically specialised functions.