Rediscovering tactile agnosia

Eighty-four patients with damage to various levels of the nervous system, ranging from the peripheral nerves to the cerebral cortex, underwent somesthetic assessment in order to determine the degree to which basic and complex perceptual and motor disorders affect tactile object recognition (TOR) and to determine whether TOR can be impaired in the absence of more basic sensorimotor imperception. The results suggest that (1) basic and intermediate disorders of somesthetic function impair TOR but are commensurately more severe for any given degree of TOR impairment in patients with peripheral lesions than in patients with cortical lesions; (2) neither hemiparesis nor hemianopia alone precludes normal TOR; (3) hemineglect contributes substantially to TOR impairment; (4) impairment of TOR can occur in the absence of more basic somesthetic dysfunction and constitutes tactile agnosia; (5) tactile agnosia is a subtle, nondisabling disorder that should be distinguished from the nonagnosic, severe and disabling disorder, astereognosis; and (6) tactile agnosia results from unilateral damage to parietotemporal cortices, possibly including the second somatosensory cortex, in either hemisphere.     

四个不同脑部位卒中后记忆功能状况比较

目的 比较四组脑皮质下单灶卒中患者的认知损害的特点,了解丘脑和基底节的功能,为早期识别血管性认知功能损害（VCI）患者提供依据.方法 使用成套神经心理测验评估63例脑皮质下单灶卒中患者和34名健康对照组,病例组患者分为左丘脑卒中组（14例）、左基底节卒中组（17例）、右丘脑卒中组（15例）和右基底节卒中组（17例）四个组进行比较,分析不同部位单灶卒中后在听觉词语学习即刻记忆、短延迟记忆、长延迟记忆、再认测试,复杂图形测试和符号数字转换回忆测试上的变化.结果 四个部位卒中患者均在AVLT的即刻记忆、短延迟记忆、长延迟记忆和复杂图形测试上与正常组比较,差异均有统计学意义（t分别=3.09、2.81、2.10、2.57;4.69、3.59、3.37、3.83;4.51、3.48、3.02、3.95; 2.45、2.02、2.91、2.47,P均＜0.05）,在AVLT再认上除右丘脑组外,在符号数字转换回忆上除左基底节组外,其余各组与正常组比较,差异均有统计学意义（t分别＝3.19、2.28、1.97;3.76、2.67、2.87,P均＜0.05）.左丘脑组与右丘脑组及右基底节组在AVLT短延时记忆上比较,差异均有统计学意义（t分别=1.82、1.74,P均＜0.05）,与右丘脑组在AVLT再认上比较,差异有统计学意义（t=1.77,P＜0.05）,与左基底节组在符号数字转换回忆上比较,差异有统计学意义（t=2.83,P＜0.05）.结论 丘脑或基底节受损后记忆功能广泛受损,以左丘脑受损后记忆功能损害最严重.     

What vs. where in touch: an fMRI study

Two streams have been identified in cortical visual processing: a ventral stream for form, color, and features, and a dorsal stream for spatial characteristics and motion. We investigated whether similar "what" and "where" dissociations of function exist for human somatosensory processing. Using identical stimuli and hand movements, subjects either performed tactile object recognition (TOR) and ignored location or performed tactile object localization (LOC) and ignored identity. A matched-movement control task separated activation associated with sensorimotor input from higher-level cognitive contributions. Results confirmed separate processing streams for TOR and LOC. TOR activated the frontal pole as well as bilateral inferior parietal and left prefrontal regions involved in tactile feature integration and naming. LOC activated bilateral superior parietal areas involved in spatial processing. The dissociation of object and spatial processing streams appears to be a modality general organizational principle in the brain.     

Thermal and tactile sensory deficits and allodynia in a nerve-injured patient: a multimodal psychophysical and functional magnetic resonance imaging study

OBJECTIVE: A case study was conducted to examine a patient with chronic neuropathic pain of the right foot following peripheral nerve injury and characterize associated sensory abnormalities. METHODS: Multimodal psychophysical examination of the patient's affected and nonaffected foot included thermal sensibility, dynamic touch, and directional sensibility. In addition, we used functional magnetic resonance imaging to study cortical representation of brush-evoked allodynia. RESULTS: Detailed psychophysical examination revealed substantial deficits in warm, cool, and tactile perception on the injured foot. These findings indicated severe dysfunction of perceptual processes mediated by A beta, A delta, and C fibers. Despite reduced tactile perception, light touch evoked a deep burning pain in the foot. Functional magnetic resonance imaging during brushing of the patient's injured foot showed that tactile allodynia led to activation of several cortical regions including secondary somatosensory cortex, anterior and posterior insular cortex, and anterior cingulate cortex. Brushing of the patient's nonaffected foot led to fewer activated regions. DISCUSSION: The profound sensory disturbances suggest a possible deafferentation type of tactile allodynia mediated by changes within the central nervous system, such as a disruption of normal tactile or thermal inhibition of nociception. The functional magnetic resonance imaging data suggest that tactile allodynia is represented in similar brain regions as experimental pain.     

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.     

Patterns of cortical reorganization parallel impaired tactile discrimination and pain intensity in complex regional pain syndrome

In the complex regional pain syndrome (CRPS), several theories proposed the existence of pathophysiological mechanisms of central origin. Recent studies highlighted a smaller representation of the CRPS-affected hand on the primary somatosensory cortex (SI) during non-painful stimulation of the affected side. We addressed the question whether reorganizational changes can also be found in the secondary somatosensory cortex (SII). Moreover, we investigated whether cortical changes might be accompanied by perceptual changes within associated skin territories. Seventeen patients with CRPS of one upper limb without the presence of peripheral nerve injuries (type I) were subjected to functional magnetic resonance imaging (fMRI) during electrical stimulation of both index fingers (IFs) in order to assess hemodynamic signals of the IF representation in SI and SII. As a marker of tactile perception, we tested 2-point discrimination thresholds on the tip of both IFs. Cortical signals within SI and SII were significantly reduced contralateral to the CRPS-affected IF as compared to the ipsilateral side and to the representation of age- and sex-matched healthy controls. In parallel, discrimination thresholds of the CRPS-affected IF were significantly higher, giving rise to an impairment of tactile perception within the corresponding skin territory. Mean sustained, but not current pain levels were correlated with the amount of sensory impairment and the reduction in signal strength. We conclude that patterns of cortical reorganization in SI and SII seem to parallel impaired tactile discrimination. Furthermore, the amount of reorganization and tactile impairment appeared to be linked to characteristics of CRPS pain.     

线分法与行为偏侧忽略的相关性研究

目的 研究线分法与行为偏侧忽略的相关性，探讨线分法能否预测行为偏侧忽略。方法 根据行为偏侧忽略的评估量表——凯瑟林一波哥量表将30例脑卒中致左侧偏瘫的患者分为4组：严重偏侧忽略组，中度偏侧忽略组，轻度偏侧忽略组和无偏侧忽略组。11例年龄匹配的健康成人作为对照组。进行线分法检查时，在A4纸的左侧、中央和右侧分别画6条水平线段，让患者用右手持圆珠笔在线的中央划一垂直分隔线。计算分隔线右侧长度占该线段全长的百分比。结果 除轻度偏侧忽略组外，被分割线段空间的位置对其它各组人员的线分结果有明显影响。严重偏侧忽略组、无偏侧忽略组、对照组出现线分法中的位置“反转效应（crossovereffect）”。严重偏侧忽略组的患者在分隔A4纸左侧及中央的线段时出现向右的偏差，而在分隔A4纸右侧的线段时出现向左的偏差。在无偏侧忽略组及对照组，被检人员在分隔A4纸左侧线段时出现向左的偏差，而在分隔中央及右侧线段时出现向右的偏差。结论 本研究表明线分法中的位置“反转效应”若出现在位于患者右侧的线段，则强烈提示患者有重度行为偏侧忽略。     

偏盲否认症临床分析

目的探讨偏盲否认症的临床特点、发病机制和大脑半球病变的联系。方法对 1 6例脑梗死所致的同位性视野缺损患者 ,进行视野、智能筛查和详细的偏盲认知、视觉疏忽的神经心理学检查 ,结合MRI或CT的病灶定位进行分析研究。结果 1 6例患者中有 1 0例存在偏盲否认症 ,其中 1 3例右侧脑梗死患者中 8例出现偏盲否认症 ,3例左侧脑梗死患者中 2例出现偏盲否认症 ;6例非偏盲否认症患者中 3例存在偏侧视觉忽视。 1 0例偏盲否认症中 ,7例为大脑中动脉供血区较大面积梗死 ,3例为枕叶或颞枕交界处小灶梗死。结论视觉认知过程在大脑皮层中没有固定的特殊区域 ,其通过多个皮层及皮层下结构协同完成 ;双侧大脑半球均与视觉认知过程有关     

Gender Difference in Premotor Activity during Active Tactile Discrimination

To investigate possible gender differences in tactile discrimination tasks, we measured cerebral blood flow of seven men and seven women using positron emission tomography and ¹⁵O water during tactile tasks performed with the right index finger. A nondiscrimination, somatosensory control task activated the left primary sensorimotor cortex and the left parietal operculum extending to the posterior insula without any gender difference. Compared with the control task, discrimination tasks activated the superior and inferior parietal lobules bilaterally, right dorsal premotor cortex, and dorsolateral prefrontal cortex in both genders, consistent with the notion of right hemisphere involvement during exploratory attentional movements. In both genders, symmetric activation of the superior and inferior parietal lobules and asymmetric activation of the right dorsolateral prefrontal cortex were confirmed. The former is consistent with the spatial representation of the tactile input and the latter with the spatial working memory. However, activation of the dorsal premotor cortex was asymmetric in men, whereas it was symmetric in women, the gender difference being statistically significant. This may suggest gender differences in motor programs for exploration in manipulospatial tasks such as tactile discrimination with active touch, possibly by greater interhemispheric interaction through the dorsal premotor cortices in women than in men.     

双侧上肢训练影响脑梗死患者脑功能重组的fMRI研究

目的利用BOLD-fMRI技术探讨双侧上肢训练对脑梗死患者脑功能重组的影响。 方法采用随机数字表法将14例患侧上肢功能中度到重度损伤皮质下梗死患者分为双侧训练组及对照组,前者接受双侧上肢训练,后者接受以患侧上肢为主的常规单侧肢体训练。2组患者分别于治疗前、治疗4周后进行上肢功能评定以及BOLD-fMRI扫描,刺激任务为肘关节被动屈伸。 结果治疗后2组患者Fugl-Meyer量表上肢部分（FMA-UE）、改良Barthel指数（MBI）评分均明显提高（P<0.05）,但两组间差异无统计学意义（P>0.05）;治疗后2组患者激活脑区增加,以双侧训练组更明显;治疗后双侧训练组患者出现双侧M1、S1、辅助运动区（SMA）激活;治疗后双侧训练组中度损伤患者呈M1对侧激活趋势,重度损伤患者呈M1同侧激活趋势。 结论双侧上肢训练能提高脑梗死患者上肢运动功能及日常生活能力,其机制可能与促进两侧大脑皮质间抑制正常化及同侧皮质脊髓通路开放有关。     

Cognitive profile and brain morphological changes in obstructive sleep apnea

Obstructive sleep apnea (OSA) is accompanied by neurocognitive impairment, likely mediated by injury to various brain regions. We evaluated brain morphological changes in patients with OSA and their relationship to neuropsychological and oximetric data. Sixteen patients affected by moderate-severe OSA (age: 55.8±6.7 years, 13 males) and fourteen control subjects (age: 57.6±5.1 years, 9 males) underwent 3.0 Tesla brain magnetic resonance imaging (MRI) and neuropsychological testing evaluating short- and long-term memory, executive functions, language, attention, praxia and non-verbal learning. Volumetric segmentation of cortical and subcortical structures and voxel-based morphometry (VBM) were performed. Patients and controls differed significantly in Rey Auditory-Verbal Learning test (immediate and delayed recall), Stroop test and Digit span backward scores. Volumes of cortical gray matter (GM), right hippocampus, right and left caudate were smaller in patients compared to controls, with also brain parenchymal fraction (a normalized measure of cerebral atrophy) approaching statistical significance. Differences remained significant after controlling for comorbidities (hypertension, diabetes, smoking, hypercholesterolemia). VBM analysis showed regions of decreased GM volume in right and left hippocampus and within more lateral temporal areas in patients with OSA. Our findings indicate that the significant cognitive impairment seen in patients with moderate-severe OSA is associated with brain tissue damage in regions involved in several cognitive tasks. We conclude that OSA can increase brain susceptibility to the effects of aging and other clinical and pathological occurrences.     

Temporal summation of heat pain in humans: Evidence supporting thalamocortical modulation

Noxious cutaneous contact heat stimuli (48 °C) are perceived as increasingly painful when the stimulus duration is extended from 5 to 10 s, reflecting the temporal summation of central neuronal activity mediating heat pain. However, the sensation of increasing heat pain disappears, reaching a plateau as stimulus duration increases from 10 to 20 s. We used functional magnetic resonance imaging (fMRI) in 10 healthy subjects to determine if active central mechanisms could contribute to this psychophysical plateau. During heat pain durations ranging from 5 to 20 s, activation intensities in the bilateral orbitofrontal cortices and the activation volume in the left primary (S1) somatosensory cortex correlated only with perceived stimulus intensity and not with stimulus duration. Activation volumes increased with both stimulus duration and perceived intensity in the left lateral thalamus, posterior insula, inferior parietal cortex, and hippocampus. In contrast, during the psychophysical plateau, both the intensity and volume of thalamic and cortical activations in the right medial thalamus, right posterior insula, and left secondary (S2) somatosensory cortex continued to increase with stimulus duration but not with perceived stimulus intensity. Activation volumes in the left medial and right lateral thalamus, and the bilateral mid-anterior cingulate, left orbitofrontal, and right S2 cortices also increased only with stimulus duration. The increased activity of specific thalamic and cortical structures as stimulus duration, but not perceived intensity, increases is consistent with the recruitment of a thalamocortical mechanism that participates in the modulation of pain-related cortical responses and the temporal summation of heat pain.     

Unilateral hemispheric lesions disrupt parallel processing within the contralateral intact hemisphere: an auditory fMRI study

Evidence from activation studies suggests that sound recognition and localization are processed in two distinct cortical networks that are each present in both hemispheres. Sound recognition and/or localization may, however, be disrupted by purely unilateral damage, suggesting that processing within one hemisphere may not be sufficient or may be disturbed by the contralateral lesion. Sound recognition and localization were investigated psychophysically and using fMRI in patients with unilateral right hemisphere lesions. Two patients had a combined deficit in sound recognition and sound localization, two a selective deficit in sound localization, one a selective deficit in sound recognition, and two normal performance in both tasks. The overall level of activation in the intact left hemisphere of the patients was smaller than in normal control subjects, irrespective of whether the patient's performance in the psychophysical tasks was impaired. Despite this overall decrease in activation strength, patients with normal performance still exhibited activation patterns similar to those of the control subjects in the recognition and localization tasks, indicating that the specialized brain networks subserving sound recognition and sound localization in normal subjects were also activated in the patients with normal performance, albeit to an altogether lesser degree. In patients with deficient performance, on the other hand, the activation patterns during the sound recognition and localization tasks were severely reduced, comprising fewer and partly atypical activation foci compared to the normal subjects. This indicates that impaired psychophysical performance correlates with a breakdown of parallel processing within specialized networks in the contralesional hemisphere.     

Callosal syndrome: implications for understanding the neuropsychology of stroke

A case is presented of callosal syndrome following cerebral hemorrhage and amphetamine abuse in a 26-year-old right-handed man. There were few hemispheric findings but a full callosal syndrome including left apraxia to verbal commands, left tactile anomia, left agraphia, right constructional apraxia, failure of blindfolded side-to-side hand replication and form-board testing showing loss of interhemispheric transmission including intermanual interference. The "draw-a-clock" test showed left inattention when drawn with the right hand but not the left, and perseveration was noted for spatial tasks done with the right hand and symbolic tasks done with the left. The patient recovered functionally almost completely but testing demonstrated continued loss of interhemispheric transmission. The case is considered of most interest for its potential in explaining phenomena observed in severe unilateral hemispheric lesions. Our findings suggest that perseveration is not a dysfunction of the damaged portion of the brain, but a phenomenon associated with intact brain attempting unfamiliar tasks. The persistence of left hemi-inattention is attributed to the inability of the left hemisphere to utilize spatial information to compensate for the phenomenon of inattention. Left-sided dyskinesia following left hemisphere lesions was attributed to the lack of symbolic information necessary to perform some movements. Dysprosody was attributed to lack of tonal information to the left hemisphere. Recovery of function following severe unilateral lesions may be largely due to compensatory learning by the intact hemisphere and assertion of ipsilateral control. As our patient originally assumed an inverted left-handed writing posture, we assume the posture is controlled by the right hemisphere.(ABSTRACT TRUNCATED AT 250 WORDS)     

Object naming is a more sensitive measure of speech localization than number counting: Converging evidence from direct cortical stimulation and fMRI

Using direct cortical stimulation to map language function during awake craniotomy is a well-described and useful technique. However, the optimum neuropsychological tasks to use have not been detailed. We used both functional MRI (fMRI) and direct cortical stimulation to compare the sensitivity of two behavioral paradigms, number counting and object naming, in the demonstration of eloquent cortical language areas. Fifteen patients with left hemisphere lesions and seven healthy control subjects participated. Patients had both preoperative fMRI at 3 T and direct cortical stimulation. Patients and controls performed object naming and number counting during fMRI at 3 T. Laterality indices were calculated from the fMRI maps for the Number-counting>Object-naming and Object-naming>Number-counting contrasts. The same number-counting and object-naming paradigms were tested during awake craniotomy and assessed for sensitivity to speech disruption. In all patients during intraoperative cortical stimulation, speech disruption occurred at more sites during object naming than during number counting. Subtle speech errors were only elicited with the object-naming paradigm, whereas only speech arrest and/or hypophonia were measured using the number counting paradigm. In both patients and controls, fMRI activation maps demonstrated greater left lateralization for object naming as compared to number counting in both frontal and temporal language areas. Number counting resulted in a more bihemispheric distribution of activations than object naming. Both cortical stimulation testing and fMRI suggest that automated speech tasks such as number counting may not fully engage putative language networks and therefore are not optimal for language localization for surgical planning.     

Ipsilateral movement-evoked fields reconsidered.

The generation mechanism of movement-evoked fields (MEFs) is poorly known and the existence of ipsilateral MEFs is still in dispute. We recorded whole-scalp neuromagnetic activity from eight subjects who were pressing response keys alternately with the right 2nd and 4th digits, while keeping the left palm on the table containing the keys. Clear ipsilateral MEFs peaked 58 +/- 2 ms after the key touch, with sources in the hand area of the right primary somatosensory cortex. The ipsilateral MEFs decreased to half size when the resting left hand was palm up on the table. However, very similar responses were obtained when another person operated the response keys and the subjects just kept their left palm on the table. No signals were elicited when the subjects only viewed these actions with no hand contact to the table. The results indicate that the MEFs receive a strong contribution from tactile input. In our experiment the ipsilateral sensorimotor activation was triggered by the movement-related vibrations transmitted to the resting hand.     

脑血管病患者失认症的神经心理学研究

为了解脑血管病患者失认症的类型与半球侧向性,对35例经影像学证实为单一病灶的脑血管病患者进行了汉语失语症检查法及自行设计的失认症检查法测试。结果显示：左半球组出现了物体、图画、色彩的失认,失认性失算,听失认,触觉失认,忽视,地理失定向,身体失认和病觉缺失;右半球组出现了色失认,忽视,地理失定向和病觉缺失。结论：大多数右利手患者的视觉、听觉、触觉、身体认知的优势半球位于左侧大脑半球;右半球可以产生色失认;忽视、病觉缺失在任何半球病变均可产生,右半球的机率高于左半球     

A comparative fMRI study of cortical representations for thermal painful, vibrotactile, and motor performance tasks.

Cortical activity due to a thermal painful stimulus applied to the right hand was studied in the middle third of the contralateral brain and compared to activations for vibrotactile and motor tasks using the same body part, in nine normal subjects. Cortical activity was demonstrated utilizing multislice echo-planar functional magnetic resonance imaging (fMRI) and a surface coil. The cortical activity was analyzed based upon individual subject activity maps and on group-averaged activity maps. The results show significant differences in activations across the three tasks and the cortical areas studied. The study indicates that fMRI enables examination of cortical networks subserving pain perception at an anatomical detail not available with other brain imaging techniques and shows that this cortical network underlying pain perception shares components with the networks underlying touch perception and motor execution. However, the thermal pain perception network also has components that are unique to this perception. The uniquely activated areas were in the secondary somatosensory region, insula, and posterior cingulate cortex. The posterior cingulate cortex activity was in a region that, in the monkey, receives nociceptive inputs from posterior thalamic medial and lateral nuclei that in turn are targets for spinothalamic terminations. Discrete subdivisions of the primary somatosensory and motor cortical areas were also activated in the thermal pain task, showing region-dependent differences in the extent of overlap with the other two tasks. Within the primary motor cortex, a hand region was preferentially active in the task in which the stimulus was painful heat. In the primary somatosensory cortex most activity in the painful heat task was localized to area 1, where the motor and vibratory task activities were also coincident. The study also indicates that the functional connectivity across multiple cortical regions reorganizes dynamically with each task.     

A fronto-parietal circuit for tactile object discrimination: an event-related fMRI study

Previous studies of somatosensory object discrimination have been focused on the primary and secondary sensorimotor cortices. However, we expected the prefrontal cortex to also become involved in sequential tactile discrimination on the basis of its role in working memory and stimulus discrimination as established in other domains. To investigate the contributions of the different cerebral structures to tactile discrimination of sequentially presented objects, we obtained event-related functional magnetic resonance images from seven healthy volunteers. Our results show that right hand object exploration involved left sensorimotor cortices, bilateral premotor, parietal and temporal cortex, putamen, thalamus, and cerebellum. Tactile exploration of parallelepipeds for subsequent object discrimination activated further areas in the dorsal and ventral portions of the premotor cortex, as well as parietal, midtemporal, and occipital areas of both cerebral hemispheres. Discriminating a parallelepiped from the preceding one involved a bilateral prefrontal-anterior cingulate-superior temporal-posterior parietal circuit. While the prefrontal cortex was active with right hemisphere dominance during discrimination, there was left hemispheric prefrontal activation during the delay period between object presentations. Delay related activity was further seen in the anterior intraparietal area and the fusiform gyrus. The results reveal a prominent role of the human prefrontal cortex for somatosensory object discrimination in correspondence with recent models on stimulus discrimination and working memory.     

腔隙性脑梗死患者血脂代谢与颈动脉内膜中层厚度的关系

目的探讨腔隙性脑梗死患者血脂代谢与颈动脉内膜中层厚度(IMT)的关系。方法选取120例腔隙性脑梗死患者(观察组)与50例无腔隙性脑梗死患者(对照组)作为研究对象,并根据颈总动脉IMT将腔隙性脑梗死患者分为IMT阳性组与IMT阴性组。所有患者均实施颈动脉超声检查,比较观察组与对照组的颈动脉IMT和血脂指标,并分析腔隙性脑梗死患者双侧颈总动脉平均IMT与血脂指标的相关性。结果观察组的左颈内动脉、右颈内动脉、左颈总动脉、右颈总动脉的IMT均高于对照组(P<0.05);观察组的TC、TG、LDL-C、APOB水平均高于对照组,HDL-C、APOA水平均低于对照组(P<0.05)。IMT阳性组的TC、TG、LDL-C、APOB水平均高于IMT阴性组,HDL-C、APOA水平均低于IMT阴性组(P<0.05)。相关性分析结果显示,TC、TG、LDL-C、APOB与腔隙性脑梗死患者的双侧颈总动脉平均IMT呈正相关,HDL-C、APOA与双侧颈总动脉平均IMT呈负相关(P<0.05)。结论腔隙性脑梗死患者的血脂代谢与其颈动脉IMT密切相关,临床上可通过超声监测腔隙性脑梗死患者的颈动脉IMT情况对血脂代谢情况进行判断。