RESUMEN
OBJECTIVES: A novel method of rehabilitation for ideomotor apraxia (IMA), using a modified version of the mirror box (MB), is proposed. The rationale is based on the theory that disrupted body representation occurs in IMA and that MB training may improve body representation. In the present MB training, patients observed and reproduced movements made by the experimenter in a mirror. The visual perspective gave the illusory sensation of seeing one's own affected hand in the mirror. METHODS: Thirteen patients were included in the study; apraxia was measured four times: i) at baseline; ii) after a week of unspecific poststroke rehabilitation (rest); iii) after a week of imitation training for apraxia, used as a control; and iv) after a week of MB training. Imitation and mirror box training were presented in counterbalanced order between participants. The effect of the mirror box on a measure of body representation was also assessed. RESULTS: The results show that MB training improved apraxia when compared to the outcomes in both the imitation and rest conditions. The improvement correlates with the impact of the mirror box on the body representation (i.e., the degree of embodiment). CONCLUSIONS: MB training shows promising effects in promoting recovery from apraxia. The hypothesis is that the mirror box triggers a quickly generated sense of embodiment of the reflected moving arm into the observer's body representation. This embodiment of the visuomotor features of the observed movements would positively affect motor programming, promoting motor improvement. Crucially, this effect seems to extend to actions performed outside the mirror box setup, enhancing patients' performance on an apraxia test.
Asunto(s)
Apraxia Ideomotora , Apraxias , Imagen Corporal , Mano , Humanos , MovimientoRESUMEN
Peripersonal Space (PPS) is the multisensory space immediately surrounding our body. Visual and tactile stimuli here are promptly processed, since their interaction gradually strengthens as the distance between visual stimulus and the body decreases. Recently, a modified version of the Temporal Order Judgment (TOJ) task was proposed to assess PPS based on the spatial congruence between somatosensory and visual stimuli. Here, we used this paradigm to explore how a temporary vs a permanent state of anxiety can alter PPS. Indeed, previous research showed that PPS boundaries are not fixed, but they can be enlarged by contingent factors (i.e. emotional features). Participants performed the TOJ paradigm twice, just before and after completing an anxiety-inducing task (experimental breathing condition) or a neutral one (control breathing condition), while their trait and state anxiety levels were repeatedly measured. We found that the pattern of visuo-tactile integration in PPS changes in the very opposite way following the two breathing tasks for participants with high levels of temporary anxiety, by strengthening and weakening its power after the experimental and control conditions, respectively. On the contrary, both the breathing tasks are capable of reducing the cross-modal interplay as compared to baseline for high trait-anxious participants, who show an overall stronger visuo-tactile integration inside the PPS than low trait anxious individuals. These results are discussed in the light of the double dissociation between orienting and alerting attentional network over-functioning, reported in state anxiety participants, and impoverished prefrontal attentional control shown by trait anxiety individuals.
Asunto(s)
Ansiedad/fisiopatología , Espacio Personal , Personalidad/fisiología , Percepción del Tacto/fisiología , Percepción Visual/fisiología , Adulto , Femenino , Humanos , Masculino , Adulto JovenRESUMEN
The peripersonal space (PPS) is the space surrounding our body, represented in a multisensory fashion by integrating stimuli of different modalities. Recently, it has been demonstrated that PPS is emotionally connoted, being sensitive to the different affective valence of the stimuli located inside it. However, how visuo-tactile interactions can be spatially shaped by intrinsic or acquired valence of stimuli is not clear. To investigate this, we conducted three experiments in which participants performed a visuo-tactile interaction task, while the intrinsic valence (Exp. 1 and 2) or the learned valence (Exp. 3) of visual stimuli was manipulated. Participants were asked to respond as fast as possible to a tactile stimulus that was delivered while a visual stimulus was approaching (Exp.1 and 3) or receding (Exp.2) from the hand. Touch was synchronized with different distances of the visual stimulus from the hand. We found that both the expectancy of stimulus and the distance of the visual one from the hand impact RTs to tactile targets. Crucially, we found that spatial modulation was also influenced by stimulus valence, but only for the approaching and not the receding stimuli. At far distances, neutral stimuli yielded overall slower RTs than intrinsically positive or negative stimuli (Experiment 1), while no modulation was exerted by the level of conditioning (Experiment 3). At near distances, response to touches accompanied by looming neutral stimuli became as fast as that occurring with positive and negative ones. Stimulus valence did not interact with the expectancy of a tactile stimulus (Experiment 2). Overall, these findings support the vision that visuo-tactile interactions can be dynamically modulated by the valence of looming visual stimuli when these are located at longer distances from the body. When closer to it, all stimuli acquire saliency, regardless of their intrinsic or acquired valence, due to their proximity, and then relevance, to the body. Overall, a view of PPS as a gradient modulating visuo-tactile integration, also based on stimulus valence, is discussed.
Asunto(s)
Espacio Personal , Percepción del Tacto/fisiología , Percepción Visual/fisiología , Adulto , Análisis de Varianza , Nivel de Alerta/fisiología , Emociones/fisiología , Femenino , Humanos , Masculino , Tacto/fisiología , Adulto JovenRESUMEN
Disruption of motor control in the alien hand syndrome might result from a dissociation between intentions and sensory information. We hypothesized that voluntary motor control in this condition could improve by restoring the congruency between motor intentions and visual feedback. The present study shows that, in one patient with right alien hand syndrome, the use of a mirror box paradigm improved motor speed. We speculate that the visual feedback provided by the mirror increases the sense of congruence between intention and sensory feedback, leading to motor improvement.
Asunto(s)
Fenómeno de la Extremidad Ajena/rehabilitación , Retroalimentación Sensorial , Desempeño Psicomotor , Fenómeno de la Extremidad Ajena/complicaciones , Fenómeno de la Extremidad Ajena/psicología , Femenino , Humanos , Persona de Mediana Edad , Accidente Cerebrovascular/complicaciones , Accidente Cerebrovascular/psicología , Rehabilitación de Accidente CerebrovascularRESUMEN
Can viewing our own body modified in size reshape the bodily representation employed for interacting with the environment? This question was addressed here by exposing participants to either an enlarged, a shrunken, or an unmodified view of their own hand in a reach-to-grasp task toward a target of fixed dimensions. When presented with a visually larger hand, participants modified the kinematics of their grasping movement by reducing maximum grip aperture. This adjustment was carried over even when the hand was rendered invisible in subsequent trials, suggesting a stable modification of the bodily representation employed for the action. The effect was specific for the size of the grip aperture, leaving the other features of the reach-to-grasp movement unaffected. Reducing the visual size of the hand did not induce the opposite effect, although individual differences were found, which possibly depended on the degree of subject's reliance on visual input. A control experiment suggested that the effect exerted by the vision of the enlarged hand could not be merely explained by simple global visual rescaling. Overall, our results suggest that visual information pertaining to the size of the body is accessed by the body schema and is prioritized over the proprioceptive input for motor control.
Asunto(s)
Imagen Corporal , Retroalimentación Fisiológica/fisiología , Fuerza de la Mano/fisiología , Reconocimiento Visual de Modelos/fisiología , Desempeño Psicomotor/fisiología , Adolescente , Adulto , Análisis de Varianza , Fenómenos Biomecánicos , Femenino , Humanos , Masculino , Valor Predictivo de las Pruebas , Adulto JovenRESUMEN
This review discusses how visual and the tactile signals are combined in the brain to ensure appropriate interactions with the space around the body. Visual and tactile signals converge in many regions of the brain (e.g. parietal and premotor cortices) where multisensory input can interact on the basis of specific spatial constraints. Crossmodal interactions can modulate also unisensory visual and somatosensory cortices, possibly via feed-back projections from fronto-parietal areas. These processes enable attentional selection of relevant locations in near body space, as demonstrated by studies of spatial attention in healthy volunteers and in neuropsychological patients with crossmodal extinction. These crossmodal spatial effects can be flexibly updated taking into account the position of the eyes and the limbs, thus reflecting the spatial alignment of visuo-tactile stimuli in external space. Further, studies that manipulated vision of body parts (alien, real or fake limbs) have demonstrated that passive viewing of the body can influence the perception of somatosensory stimuli, again involving areas in the premotor and parietal cortices. Finally, we discuss how tool-use can expand the region of visuo-tactile integration in near body space, emphasizing the flexibility of this system at the single-neuron level in the monkey's parietal cortex, with corresponding multisensory effects in normals and neuropsychological patients. We conclude that visuo-tactile crossmodal links dominate the representation of near body space and that this is implemented functionally in parietal and premotor brain regions. These integration processes mediate the orienting of spatial attention and generate an efficient and flexible representation the space around the body.
Asunto(s)
Espacio Personal , Percepción Espacial/fisiología , Percepción del Tacto/fisiología , Percepción Visual/fisiología , Animales , Atención/fisiología , Mapeo Encefálico , Corteza Cerebral/fisiología , Lateralidad Funcional , Humanos , Postura/fisiología , Comportamiento del Uso de la Herramienta/fisiologíaRESUMEN
Human eyes are a powerful social cue that may automatically attract the attention of an observer. Here we tested whether looking toward open human eyes, as often arises in standard clinical "confrontation" tests, may affect contralesional errors in a group of right brain-damaged patients showing visual extinction. Patients were requested to discriminate peripheral shape-targets presented on the left, right, or bilaterally. On each trial they also saw a central task-irrelevant stimulus, comprising an image of the eye sector of a human face, with those seen eyes open or closed. The conditions with central eye stimuli open (vs closed) induced more errors for contralesional peripheral targets, particularly for bilateral trials. These results suggest that seeing open eyes in central vision may attract attentional resources there, reducing attention to the periphery, particularly for the affected contralesional side. The seen gaze of the examiner may thus need to be considered during confrontation testing and may contribute to the effectiveness of that clinical procedure.
Asunto(s)
Atención , Infarto Cerebral/fisiopatología , Fijación Ocular , Lateralidad Funcional , Reconocimiento Visual de Modelos , Trastornos de la Percepción/fisiopatología , Anciano , Anciano de 80 o más Años , Atención/fisiología , Infarto Cerebral/psicología , Evaluación de la Discapacidad , Ojo , Cara , Fijación Ocular/fisiología , Lateralidad Funcional/fisiología , Humanos , Persona de Mediana Edad , Examen Neurológico , Pruebas Neuropsicológicas , Reconocimiento Visual de Modelos/fisiología , Trastornos de la Percepción/diagnóstico , Trastornos de la Percepción/etiología , Estimulación Luminosa , Valor Predictivo de las PruebasRESUMEN
The authors show that prismatic adaptation can reduce tactile inattention in stroke patients with unilateral neglect. Four patients with visuospatial neglect and tactile extinction underwent 10-minute application of 20 degrees right-shifting prismatic lenses during pointing. This improved contralesional tactile perception in all patients, even for a task requiring no exploration or spatial motor responses. This finding suggests a potential role for prismatic adaptation in the rehabilitation of multiple sensory modalities in patients with neglect.
Asunto(s)
Lentes , Trastornos de la Percepción/terapia , Accidente Cerebrovascular/complicaciones , Tacto , Adaptación Fisiológica , Anciano , Humanos , Persona de Mediana Edad , Trastornos de la Percepción/diagnóstico , Trastornos de la Percepción/etiología , Accidente Cerebrovascular/diagnóstico por imagen , Tomografía Computarizada por Rayos X , Resultado del TratamientoRESUMEN
Normal human subjects underwent functional magnetic resonance imaging (fMRI) while performing a simple visual manual reaction-time (RT) task with lateralized brief stimuli, the so-called Poffenberger's paradigm. This paradigm was employed to measure interhemispheric transmission (IT) time by subtracting mean RT for the uncrossed hemifield-hand conditions, that is, those conditions not requiring an IT, from the crossed hemifield-hand conditions, that is, those conditions requiring an IT to relay visual information from the hemisphere of entry to the hemisphere subserving the response. The obtained difference is widely believed to reflect callosal conduction time, but so far there is no direct physiological evidence in humans. The aim of our experiment was twofold: first, to test the hypothesis that IT of visuomotor information requires the corpus callosum and to identify the cortical areas specifically activated during IT. Second, we sought to discover whether IT occurs mainly at premotor or perceptual stages of information processing. We found significant activations in a number of frontal, parietal, and temporal cortical areas and in the genu of the corpus callosum. These activations were present only in the crossed conditions and therefore were specifically related to IT. No selective activation was present in the uncrossed conditions. The location of the activated callosal and cortical areas suggests that IT occurs mainly, but not exclusively, at premotor level. These results provide clear cut evidence in favor of the hypothesis that the crossed-uncrossed difference in the Poffenberger paradigm depends on IT rather than on a differential hemispheric activation.
Asunto(s)
Cuerpo Calloso/fisiología , Lóbulo Frontal/fisiología , Imagen por Resonancia Magnética , Lóbulo Parietal/fisiología , Lóbulo Temporal/fisiología , Percepción Visual/fisiología , Adulto , Lateralidad Funcional , Humanos , Tiempo de ReacciónRESUMEN
Several recent studies have shown cross-modal visual-tactile extinction in patients with right hemisphere lesions. In the present case, patient BV, a visual stimulus close to the right hand extinguished awareness of a touch on the left hand that would otherwise have been felt. Such extinction was reduced if the right visual stimulus was placed more distant from the patient's hand in the radial plane. However, when the patient held sticks in both hands, so that a far right visual stimulus was now at the end of the "tool" in his right hand, cross-modal extinction from this far stimulus increased. This effect depended on the patient holding a stick that reached to the position of the far visual stimulus; a similar large stick, but not connected with the patient's hand and laying passively on the right, had no effect. Wielding the stick induced a re-mapping of space, so that the far light became treated as near (and reachable by) the hand, thus modifying the spatial nature of cross-modal extinction. This may relate to the properties of multimodal neurons as found in the monkey intraparietal sulcus.
Asunto(s)
Encéfalo/fisiopatología , Extinción Psicológica , Lateralidad Funcional/fisiología , Percepción Espacial/fisiología , Tacto/fisiología , Percepción Visual/fisiología , Anciano , Encéfalo/patología , Mano/fisiopatología , Humanos , Imagen por Resonancia Magnética , MasculinoRESUMEN
When observing ourselves in a mirror, we see our body and adjacent objects (e.g. a comb or razor) projecting the image of distant objects. Are these recoded by the brain as reflecting stimuli in peripersonal space? To address this, we exploited the neuropsychological phenomenon of crossmodal, visual-tactile extinction, as shown by patient BV following right-hemisphere stroke. In such crossmodal extinction, a right visual event impairs the perception of a simultaneous left tactile event. In BV, the right visual stimulus (an LED flash) induced more extinction of touch on the contralesional left hand when presented near the ipsilesional right hand, than when distant from it. This agrees with previous data in patients and monkeys showing that visual-tactile interactions are strongest within peripersonal space. Crucially, we also found that an ipsilesional flash produced more extinction when observed as the distant mirror-reflection of an LED that lay close to the ipsilesional hand, rather than as a distant LED flash projecting an equivalent visual image directly. This suggests that in BV, seeing his own hand via a mirror activates a representation of peripersonal space around that hand, not of the extrapersonal space suggested by the distant visual image in the mirror. We discuss the possible neural basis of interpreting mirror reflections.
Asunto(s)
Encéfalo/fisiopatología , Reconocimiento Visual de Modelos/fisiología , Accidente Cerebrovascular/fisiopatología , Percepción Visual/fisiología , Anciano , Mapeo Encefálico , Extinción Psicológica , Lateralidad Funcional , Humanos , Procesamiento de Imagen Asistido por Computador , Imagen por Resonancia Magnética , Masculino , Accidente Cerebrovascular/psicologíaRESUMEN
To study the electrophysiological correlates of conscious vision, we recorded event-related potentials (ERPs) in a patient with partial unilateral visual extinction as a result of right-hemisphere damage. When, following bilateral presentations, contralesional stimuli were not perceived, there was an absence of the early attention-sensitive P1 (80-120 msec) and N1 (140-180 msec) components of the ERP response. In contrast, following unilateral presentations, or in those bilateral presentations in which contralesional stimuli were perceived (about 60%), these ERP components were present. These results provide novel evidence that extinction involves the stage of early focusing of attention and that the P1 and N1 components of visual ERPs are reliable physiological correlates of conscious vision.
Asunto(s)
Atención/fisiología , Potenciales Evocados Visuales/fisiología , Trastornos de la Visión/fisiopatología , Trastornos de la Visión/psicología , Visión Ocular/fisiología , Encefalopatías/complicaciones , Dominancia Cerebral , Lateralidad Funcional , Humanos , Estimulación Luminosa/métodos , Trastornos de la Visión/etiología , Campos Visuales/fisiologíaRESUMEN
We studied with PET the intra- and interhemispheric pathways subserving a simple, speeded-up visuomotor task. Six normal subjects and one patient with a complete section of the corpus callosum (M.E.) underwent regional cerebral blood flow (rCBF) measurements under conditions of lateralized tachistoscopic visual presentations in a simple manual reaction time paradigm. Confirming previous behavioural findings, we found that on average crossed hand and/or hemifield conditions, i.e. those requiring an interhemispheric transfer of information, yielded a longer RT than uncrossed conditions. This difference (0.7 ms) was dramatically larger (45.6 ms) in the callosum-sectioned patient M.E. In normal subjects the cortical areas selectively activated in uncrossed and crossed conditions were different. In the former condition, most activation foci were anterior to the ventral anterior commissure (VAC) plane, whereas in the latter there was a prevalent parietal and occipital activation. This shows that a simple model in which the cortical visuo-motor pathways are similar in the intra- and the interhemispheric condition, with an extra callosal route for the latter, is too simplistic. Furthermore, these results suggest that the bulk of visuomotor interhemispheric transfer takes place through the widespread callosal fibres interconnecting the parietal cortices of the two hemispheres. The pattern of activation in the two crossing conditions was markedly different in M.E., in whom interhemispheric transfer might take place via his intact anterior commissure or subcortical commissures.
Asunto(s)
Mapeo Encefálico/métodos , Encéfalo/fisiología , Cuerpo Calloso/cirugía , Tomografía Computarizada de Emisión/métodos , Vías Visuales/fisiología , Adulto , Encéfalo/irrigación sanguínea , Encéfalo/diagnóstico por imagen , Corteza Cerebral/fisiología , Circulación Cerebrovascular , Lateralidad Funcional , Humanos , Imagen por Resonancia Magnética , Masculino , Modelos Neurológicos , Desempeño Psicomotor , Radiografía , Valores de Referencia , Flujo Sanguíneo RegionalRESUMEN
We performed a spike topography study and a functional magnetic resonance imaging (fMRI) in a female patient with benign rolandic epilepsy presenting single high-amplitude evoked spikes in response to somatosensory peripheral stimulation. The stimulus was delivered to the first finger of the right hand using a tendon hammer, which evoked a single spike followed by a slow wave, showing the maximal amplitude over the left central regions. fMRI showed that the contralateral sensory cortices (S1 and S2) and the motor cortex (M I) were activated during tapping stimulation. In 3 normal subjects, tapping stimulation produced no fMRI activation. This fMRI study documents a highly focal activation of sensorimotor areas related to subclinical evoked spikes in benign rolandic epilepsy.
Asunto(s)
Epilepsia Rolándica/diagnóstico , Epilepsia Rolándica/fisiopatología , Imagen por Resonancia Magnética , Estimulación Acústica , Niño , Electroencefalografía , Potenciales Evocados Auditivos , Femenino , Humanos , Corteza Motora/fisiopatología , Corteza Somatosensorial/fisiopatologíaRESUMEN
We investigated the cerebral cortical route by which visual information reaches motor cortex when visual signals are used for manual responses. Subjects responded unimanually to photic stimuli delivered to the hemifield ipsilateral or contralateral to the moving hand. On some trials, trans-cranial magnetic stimulation (TMS) was applied unilaterally over the occiput, with the aim of stimulating extrastriate visual areas and thereby modifying transmission of visual input. In association with the side of a visual stimulus and a motor response, TMS could change inter- or intra-hemispheric transmission needed to convey visual information to motor areas. Reaction time differences following TMS suggested that TMS exerted an inhibitory effect only when visuo-motor information had to be transferred interhemispherically. This result reinforces evidence for an extrastriate pathway of interhemispheric transfer of visuomotor information.
Asunto(s)
Encéfalo/fisiología , Desempeño Psicomotor/fisiología , Estimulación Magnética Transcraneal , Estimulación Acústica , Adulto , Encéfalo/efectos de la radiación , Femenino , Lateralidad Funcional , Humanos , Masculino , Persona de Mediana Edad , Actividad Motora , Desempeño Psicomotor/efectos de la radiación , Tiempo de Reacción , Valores de Referencia , Vías Visuales/fisiología , Percepción VisualRESUMEN
A right-brain damaged patient (GR) showing tactile extinction, neglect and no hypesthesia, was asked to compare, in 30 trials, the size of two spheres of different size simultaneously put into each hand. Accuracy was poor because GR was unable to feel the sphere in his left hand and could only report the size of the right sphere. GR was then asked to compare two spheres of identical sizes although again unable to perceive the left sphere he was deceived by a perceptual after-effect also observed in normal subjects, and reported incorrectly the size of the right sphere. The left sphere although unperceived, influenced the perception of the right hand, thus giving the first evidence for an implicit processing of extinguished somatosensory information.
Asunto(s)
Encefalopatías/fisiopatología , Percepción/fisiología , Corteza Somatosensorial/fisiopatología , Anciano , Anciano de 80 o más Años , Encefalopatías/diagnóstico por imagen , Humanos , Masculino , Corteza Somatosensorial/diagnóstico por imagen , Tomografía Computarizada por Rayos XRESUMEN
A.V., a 73-year-old right-handed man, developed right hemiplegia and hemi-hypoaesthesia following a cerebrovascular accident. A large, left hemispheric lesion was revealed by CT scan but, despite this, the patient did not show any language impairment in either Italian or English (which he spoke fluently). However, he did show right visual neglect and visuo-spatial deficits, a neuropsychological picture that usually follows lesions to the non-dominant hemisphere. Given these clinical data, A.V.'s cerebral organisation seems to be reversed. This and previous cases reported in the literature are discussed.
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Infarto Cerebral/fisiopatología , Dominancia Cerebral , Lenguaje , Conducta Espacial/fisiología , Percepción Visual/fisiología , Anciano , Lateralidad Funcional/fisiología , Hemiplejía/etiología , Humanos , Masculino , Multilingüismo , Pruebas NeuropsicológicasRESUMEN
In order to investigate the organic and psychogenic components of post-concussive syndrome (PCS), the subjective complaints, the cognitive findings and the Minnesota Multiphasic Personality Inventory (MMPI) profiles of 53 consecutive mild head injury patients (MHI) with persistent PCS were evaluated. The results seem to suggest the presence of two groups: in the first, minimal lesional signs were associated with more prolonged loss of consciousness (LC) and post-traumatic amnesia (PTA), as well as an MMPI profile not indicative of a neurotic state, whereas in the second the absence of any lesional sign was associated with shorter LC and PTA duration, as well as evidence of neurotic MMPI scores. A female prevalence was observed in the first group and a male prevalence in the other one.
Asunto(s)
Conmoción Encefálica/diagnóstico , Daño Encefálico Crónico/diagnóstico , Trastornos del Conocimiento/diagnóstico , MMPI/estadística & datos numéricos , Trastornos Somatomorfos/diagnóstico , Adolescente , Adulto , Anciano , Conmoción Encefálica/psicología , Daño Encefálico Crónico/psicología , Corteza Cerebral/diagnóstico por imagen , Corteza Cerebral/lesiones , Trastornos del Conocimiento/psicología , Evaluación de la Discapacidad , Determinación de la Elegibilidad/legislación & jurisprudencia , Testimonio de Experto/legislación & jurisprudencia , Femenino , Humanos , Masculino , Persona de Mediana Edad , Pruebas Neuropsicológicas , Trastornos Neuróticos/diagnóstico , Trastornos Neuróticos/psicología , Psicometría , Seguridad Social/legislación & jurisprudencia , Trastornos Somatomorfos/psicología , Tomografía Computarizada por Rayos XRESUMEN
The classic amnesic syndrome is characterised by a severe anterograde amnesia and a less important retrograde amnesia with sparing of the semantic component. We report the case of a patient who showed a global amnesic syndrome following a mild head injury. Initially, amnesia was both anterograde and retrograde, and also involved semantic knowledge. Two years later the picture had changed remarkably. The retrograde deficit for autobiographical events was still total, while semantic memory had recovered to a large extent. Learning had also greatly improved, but only if assessed after a short delay; abnormally rapid forgetting rate were found at longer intervals. This pattern of impairment does not lend itself to an easy interpretation. However, the hypothesis of a consolidation deficit may be advanced.