Tactile agnosia and tactile aphasia: symptomatological and anatomical differences

The effects of cognitive, physical, and somatosensory rehabilitation after right temporo-parietal tumor resection on cognitive, motor, somatosensory, and electrophysiological parameters: A case report

INTRODUCTION

This report examines the effects of a multimodal rehabilitation program which includes cognitive, physical, and somatosensory rehabilitation after right temporo-parietal tumor resection on cognitive, motor, somatosensory, and electrophysiological parameters.

CASE DESCRIPTION

A 22-year-old patient presented with sensory loss in the dominant left hand and reduced writing ability after right temporo-parietal lobe resection. Cognitive, motor, and sensory evaluations were carried out pre and post-treatment. The patient's spontaneous electroencephalo-gram (EEG) and an EEG during application of transcutaneous electrical nerve stimulation (TENS) (TENS EEG) were recorded. As a reference for the patient's electrophysiological values, EEGs of 4 healthy individuals were also taken. Over a period of 1 year, the patient received multimodal rehabilitation which includes cognitive, physical, and somato-sensory rehabilitation on 2 days each week.

OUTCOMES

An improvement of the patient's cognitive capacities, motor strength, superficial, deep and cortical sensations was achieved. After rehabilitation, an increase in parietal and occipital alpha activity as well as in frontal and parietal beta activity was seen both in spontaneous EEG and in TENS EEG. With increasing TENS intensity, alpha and beta power increased as well.

CONCLUSION

Our findings suggest that a multimodal rehabilitation program may improve cognitive, sensory, and motor effects after resection due to tumor surgery.

Tactually-related cognitive impairments: sharing of neural substrates across associative tactile agnosia, agraphesthesia, and kinesthetic reading difficulty

INTRODUCTION

A precise understanding of the neural substrates underlying tactually-related cognitive impairments such as bilateral tactile agnosia, bilateral agraphesthesia, kinesthetic alexia and kinesthetic reading difficulty is currently incomplete. In particular, recent data have implicated a role for the lateral occipital tactile visual region, or LOtv, in tactile object naming (Amedi et al. Cerebral Cortex 2002). Thus, this study set out to examine the degree to which the LOtv may be involved in tactually-related cognitive impairments by examining two unique cases.

METHODS

To assess whether LOtv or the visual word form area (VWFA) is involved in tactually-related cognitive impairments, the average activation point of LOtv and that of VWFA were placed on the single-photon emission computed tomography (SPECT) cerebral blood flow images of two patients: one with bilateral associative tactile agnosia, bilateral agraphesthesia, and ineffective kinesthetic reading, and the other with kinesthetic reading difficulty.

RESULTS

The average LOtv coordinate was involved in the area of hypoperfusion in both patients, whereas that of VWFA was not included in any of the hypoperfused areas.

CONCLUSIONS

The results support the view that interruption of LOtv or disconnection to LOtv and to VWFA may cause these tactually-related cognitive impairments. Further, bilateral associative tactile agnosia and bilateral agraphesthesia are attributable toward the damage of the occipital lobe, whereas unilateral or predominantly one-sided associative tactile agnosia and agraphesthesia are attributable toward the damage of the parietal lobe.

Isolated post-traumatic astereognosis: a case-based review

INTRODUCTION

Astereognosis is the tactile inability to recognize objects placed in the palms by touch with the eyes closed or blind-folded in the presence of intact primary sensory modalities. Stereognosis is usually considered a function of the contralateral sensory cerebral cortex. However, lesions of several anatomic areas and pathologic entities have been reported to be associated with astereognosis. Only two previous reports linked traumatic injury to isolated astereognosis: following surgical evacuation of traumatic parietal extradural hematoma and following bullet injury in the neck in 1992 and 1919, respectively.

METHODS AND RESULTS

All the pertinent literature was analyzed, focusing on the relevant definitions, clinical spectra, pathoanatomical processes, assessment, management, and outcomes of astereognosis. Also, an illustrative case was presented. The case highlights isolated post-traumatic left hand astereognosis in a 17-year-old boy following a blunt trauma to the head which resulted in a non-hemorrhagic contusion of the right post-central gyrus.

CONCLUSIONS

Post-traumatic isolated astereognosis is a rare and probably underreported sequel of traumatic brain injury. Neurosurgeons need to be more sensitive to the assessment and detection of subtle stereognostic deficits in general and in trauma patients in particular. Other anatomical areas, in addition to the contralateral post-central gyrus, may be considered in the pathogenesis of astereognosis with the involvement of the dorsal column medial lemniscus tract such as the brainstem, foramen magnum, and the cervical spinal cord. To the best of our knowledge, this rare case report is considered the second report on astereognosis following head trauma, and the third report on astereognosis following trauma in general.

Convergence of heteromodal lexical retrieval in the lateral prefrontal cortex

Lexical retrieval requires selecting and retrieving the most appropriate word from the lexicon to express a desired concept. Few studies have probed lexical retrieval with tasks other than picture naming, and when non-picture naming lexical retrieval tasks have been applied, both convergent and divergent results emerged. The presence of a single construct for auditory and visual processes of lexical retrieval would influence cognitive rehabilitation strategies for patients with aphasia. In this study, we perform support vector regression lesion-symptom mapping using a brain tumor model to test the hypothesis that brain regions specifically involved in lexical retrieval from visual and auditory stimuli represent overlapping neural systems. We find that principal components analysis of language tasks revealed multicollinearity between picture naming, auditory naming, and a validated measure of word finding, implying the existence of redundant cognitive constructs. Nonparametric, multivariate lesion-symptom mapping across participants was used to model accuracies on each of the four language tasks. Lesions within overlapping clusters of 8,333 voxels and 21,512 voxels in the left lateral prefrontal cortex (PFC) were predictive of impaired picture naming and auditory naming, respectively. These data indicate a convergence of heteromodal lexical retrieval within the PFC.

Case study: A selective tactile naming deficit for letters and numbers due to interhemispheric disconnection

The role of white matter pathways in cognition is a topic of active investigation that is vital to both the fields of clinical neurology and cognitive neuroscience. White matter pathways provide critical connectivity amongst numerous specialized brain regions thereby enabling higher level cognition. While the effects of dissections and lesions of the corpus callosum have been reported, it is less understood how unilateral focal white matter lesions may impact cognitive processes. Here, we report a unique case study in which a small left lateralized stroke in the white matter adjacent to the body of the corpus callosum selectively impaired the ability to name letters and numbers presented to the ipsilesional, left hand. Naming of letters, numbers and objects was tested in both the visual and tactile modalities in both hands. Diffusion-weighted imaging showed a marked reduction in white matter pathway integrity through the body of the corpus callosum. Clinically, this case highlights the significant impact that a focal white matter lesion can have on higher-level cognition, specifically the integration of verbal and tactile information. Moreover, this case adds to prior reports on tactile agnosia by including DTI imaging data and emphasizing the role that white matter pathways through the body of the corpus callosum play in integrating tactile input from the right hemisphere with verbal naming capabilities of the left hemisphere. Finally, the findings also provoke fresh insight into alternative strategies for rehabilitating cognitive functioning when structural connectivity may be compromised.

Cortical lateralization of cheirosensory processing in callosal dysgenesis

The paradoxical absence of a split-brain syndrome in most cases of callosal dysgenesis has originated three main hypotheses, namely, (i) bilateral cortical representation of language, (ii) bilateral thalamocortical projections of somatosensory pathways conveyed by the spinothalamic-medial lemniscus system, and (iii) a variable combination of (i) and (ii). We used functional neuroimaging to investigate the cortical representation and lateralization of somatosensory information from the palm of each hand in six cases of callosal dysgenesis (hypothesis [ii]). Cortical regions of interest were contralateral and ipsilateral S1 (areas 3a and 3b, 1 and 2 in the central sulcus and postcentral gyrus) and S2 (parts of areas 40 and 43 in the parietal operculum). The degree of cortical asymmetry was expressed by a laterality index (LI), which may assume values from −1 (fully left-lateralized) to +1 (fully right-lateralized). In callosal dysgenesis, LI values for the right and the left hands were, respectively, −1 and + 1 for both S1 and S2, indicating absence of engagement of ipsilateral S1 and S2. In controls, LI values were − 0.70 (S1) and − 0.51 (S2) for right hand stimulation, and 0.82 (S1) and 0.36 (S2) for left hand stimulation, reflecting bilateral asymmetric activations, which were significantly higher in the hemisphere contralateral to the stimulated hand. Therefore, none of the main hypotheses so far entertained to account for the callosal dysgenesis-split-brain paradox have succeeded. We conclude that the preserved interhemispheric transfer of somatosensory tactile information in callosal dysgenesis must be mediated by a fourth alternative, such as aberrant interhemispheric bundles, reorganization of subcortical commissures, or both.

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We studied the cortical sensory representation of the hands in callosal dysgenesis.

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The representation of the hands was bilateral but asymmetric in controls.

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The representation of the hands was strictly contralateral in callosal dysgenesis.

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The representation of the hands is a distinguishing feature of callosal dysgenesis.

Representations of microgeometric tactile information during object recognition

Object recognition through tactile perception involves two elements: the shape of the object (macrogeometric properties) and the material of the object (microgeometric properties). Here we sought to determine the characteristics of microgeometric tactile representations regarding object recognition through tactile perception. Participants were directed to recognize objects with different surface materials using either tactile information or visual information. With a quantitative analysis of the cognitive process regarding object recognition, Experiment 1 confirmed the same eight concepts (composed of rules defining distinct cognitive processes) commonly generated in both tactile and visual perceptions to accomplish the task, although an additional concept was generated during the visual task. Experiment 2 focused only on tactile perception. Three tactile objects with different surface materials (plastic, cloth and sandpaper) were used for the object recognition task. The participants answered a questionnaire regarding the process leading to their answers (which was designed based on the results obtained in Experiment 1) and to provide ratings on the vividness, familiarity and affective valence. We used these experimental data to investigate whether changes in material attributes (tactile information) change the characteristics of tactile representation. The observation showed that differences in tactile information resulted in differences in cognitive processes, vividness, familiarity and emotionality. These two experiments collectively indicated that microgeometric tactile information contributes to object recognition by recruiting various cognitive processes including episodic memory and emotion, similar to the case of object recognition by visual information.

Hemispheric Dominance for Stereognosis in a Patient With an Infarct of the Left Postcentral Sensory Hand Area

The concept of left hemispheric dominance for praxis, speech, and language has been one of the pillars of neurology since the mid-19th century. In 1906, Hermann Oppenheim reported a patient with bilateral stereoagnosia (astereognosis) caused by a left parietal lobe tumor and proposed that the left hemisphere was also dominant for stereognosis. Surprisingly, few cases of bilateral stereoagnosia caused by a unilateral cerebral lesion have been documented in the literature since then. Here we report a 75-year-old right-handed man who developed bilateral stereoagnosia after suffering a small infarct in the crown of the left postcentral gyrus. He could not recognize objects with either hand, but retained the ability to localize stimuli applied to the palm of his left (ipsilesional) hand. He was severely disabled in ordinary activities requiring the use of his hands. The lesion corresponded to Brodmann area 1, where probabilistic anatomic, functional, and electrophysiologic studies have located one of the multiple somatosensory representations of the hand. The lesion was in a strategic position to interrupt both the processing of afferent tactile information issuing from the primary somatosensory cortex (areas 3a and 3b) and the forward higher-order processing in area 2, the secondary sensory cortex, and the contralateral area 1. The lesion also deprived the motor hand area of its afferent regulation from the sensory hand area (grasping), while leaving intact the visuomotor projections from the occipital cortex (reaching). Our patient supports Oppenheim's proposal that the left postcentral gyrus of some individuals is dominant for stereognosis.

The role of self-touch in somatosensory and body representation disorders after stroke

Somatosensory impairments occur in about half of the cases of stroke. These impairments range from primary deficits in tactile detection and the perception of features, to higher order impairments in haptic object recognition and bodily experience. In this paper, we review the influence of active- and self-touch on somatosensory impairments after stroke. Studies have shown that self-touch improves tactile detection in patients with primary tactile deficits. A small number of studies concerned with the effect of self-touch on bodily experience in healthy individuals have demonstrated that self-touch influences the structural representation of one's own body. In order to better understand the effect of self-touch on body representations, we present an informal study of a stroke patient with somatoparaphrenia and misoplegia. The role of self-touch on body ownership was investigated by asking the patient to stroke the impaired left hand and foreign hands. The patient reported ownership and a change in affect over all presented hands through self-touch. The time it took to accomplish ownership varied, based on the resemblance of the foreign hand to the patient's own hand. Our findings suggest that self-touch can modulate impairments in body ownership and affect, perhaps by helping to reinstate the representation of the body.

Comparison of cerebral activation involved in oral and manual stereognosis

Brain activity associated with manual stereognosis has been the focus of increasing recent research effort. However, although oral stereognosis, defined as the ability to recognize and discriminate the food bolus in the mouth, is important for mastication and swallowing, there is little information available about the neural network relating to this function. In the present study, cerebral activation associated with oral stereognosis was evaluated as compared with manual stereognosis. Brain imaging data were acquired by functional MRI (fMRI). fMRI experiments were performed on 16 healthy right-handed young adults without any history of neurological or psychiatric disorders. All subjects had all teeth without malocclusion. Ten stereognosis test shape pieces sized approximately 20 mm × 20 mm × 10 mm were fabricated for this experiment. All test pieces had a complicated form that made them difficult to recognize with ease. Subjects were instructed to assess the shape of the test piece in the mouth or hand. The ten test pieces were randomly assigned to each subject and each run. Stereognosis-specific activation was found in the primary somatosensory area, primary motor area, supramarginal gyrus, premotor area, supplementary motor area, fusiform gyrus, frontopolar area and dorsolateral prefrontal cortex. Differences in cerebral activation between oral and manual stereognosis were found in the insular cortex and visual association cortex.

Computation of tactile object properties requires the integrity of praxic skills

We describe a series of experiments to examine the tactile identification of objects over the course of neurological recovery in a patient with an intracerebral haemorrhage involving the left inferior and superior parietal lobe. Tactile agnosia in this case involved the ipsilesional as well as the contralesional hand, allowing us to observe the effects of dominant parietal lobe damage without the confounding effects of hemiparesis. The findings demonstrate that both apraxia and tactile apperceptive agnosia may result from a unilateral lesion involving the left parietal lobe. The findings further suggest that the computation of macro-geometrical and micro-geometrical tactile object properties is dissociable. Macro-geometrical tactile analysis depends on intact programming of exploratory hand movements, while the role of such movements in micro-geometrical analysis is less clear.

The influence of misnaming on object recognition: a case of multimodal agnosia

We present a case of multimodal agnosia in the visual and tactile modality due to an infarction in the territory of the left posterior cerebral artery. The patient's ability to recognize objects fluctuated depending on his verbal activity. When he misnamed presented objects, he tended to use them and to draw them in keeping with the wrong name. We submit that the mechanism causing associative agnosia is more dynamic than it was hitherto considered. It originates from the rivalry between top-down central regulation and bottom-up peripheral flow.

Tactile morphagnosia secondary to spatial deficits

A 73-year old man showed visual and tactile agnosia following bilateral haemorrhagic stroke. Tactile agnosia was present in both hands, as shown by his impaired recognition of objects, geometrical shapes, letters and nonsense shapes. Basic somatosensory functions and the appreciation of substance qualities (hylognosis) were preserved. The patient's inability to identify the stimulus shape (morphagnosia) was associated with a striking impairment in detecting the orientation of a line or a rod in two- and three-dimensional space. This spatial deficit was thought to underlie morphagnosia, since in the tactile modality form recognition is built upon the integration of the successive changes of orientation in space made by the hand as it explores the stimulus. Indirect support for this hypothesis was provided by the location of the lesions, which could not account for the severe impairment of both hands. Only those located in the right hemisphere encroached upon the posterior parietal cortex, which is the region assumed to be specialised in shape recognition. The left hemisphere damage spared the corresponding area and could not, therefore, be held responsible for the right hand tactile agnosia. We submit that tactile agnosia can result from the disruption of two discrete mechanisms and has different features. It may arise from a parietal lesion damaging the high level processing of somatosensory information that culminates in the structured description of the object. In this case, tactile recognition is impaired in the hand contralateral to the side of the lesion. Alternatively, it may be caused by a profound derangement of spatial skills, particularly those involved in detecting the orientation in space of lines, segments and complex patterns. This deficit results in morphagnosia, which affects both hands to the same degree.

Bilateral tactile agnosia: a case report

This study reports a 64-year-old right-handed male who manifested bilateral tactile recognition deficits. They were diagnosed as bilateral tactile agnosia, since the patient showed difficulty in semantic association of objects despite preserved hylognosis and morphognosis. The patient had a bilateral lesion in the subcortical region of the angular gyrus. The case reported by Endo et al. (1992) had a right hand tactile agnosia due to a subcortical lesion in the left angular gyrus. Our findings support Endo's hypothesis that tactile agnosia occurs when the somatosensory association cortex is disconnected from the semantic memory store located in the inferior temporal lobe by a subcortical lesion of the angular gyrus. We suggest that the extent of the lesion in the tactual-semantic pathway is related to the severity of tactile agnosia and the types of the tactile naming errors.

Modality specific naming and gesture disturbances: a case with optic aphasia, bilateral tactile aphasia, optic apraxia and tactile apraxia

This study reports a patient who manifested optic aphasia, tactile aphasia, optic apraxia, and tactile apraxia following an operation for epidural left parietal haematoma. He could neither name nor pantomime the use of objects presented visually or tactually, but correctly performed semantic association tasks, thus demonstrating preserved recognition. He could name and pantomime the use of auditorily presented objects. Experimental results disproved that pantomime disorders were secondary to naming disorders, and suggested that modality specific aphasia and modality specific apraxia are independent clinical syndromes. CT scans showed injury to the posterior callosal radiations, the white matter of the angular gyrus, and the medial portion of the occipital lobe in the left hemisphere. We suggest that modality specific aphasia and modality specific apraxia can be explained by assuming a common semantic memory store.