Spatial orientation and the representation of space with parietal lobe lesions

Damage to the human parietal cortex leads to disturbances of spatial perception and of motor behaviour. Within the parietal lobe, lesions of the superior and of the inferior lobule induce quite different, characteristic deficits. Patients with inferior (predominantly right) parietal lobe lesions fail to explore the contralesional part of space by eye or limb movements (spatial neglect). In contrast, superior parietal lobe lesions lead to specific impairments of goal-directed movements (optic ataxia). The observations reported in this paper support the view of dissociated functions represented in the inferior and the superior lobule of the human parietal cortex. They suggest that a spatial reference frame for exploratory behaviour is disturbed in patients with neglect. Data from these patients' visual search argue that their failure to explore the contralesional side is due to a disturbed input transformation leading to a deviation of egocentric space representation to the ipsilesional side. Data further show that this deviation follows a rotation around the earth-vertical body axis to the ipsilesional side rather than a translation towards that side. The results are in clear contrast to explanations that assume a lateral gradient ranging from a minimum of exploration in the extreme contralesional to a maximum in the extreme ipsilesional hemispace. Moreover, the failure to orient towards and to explore the contralesional part of space appears to be distinct from those deficits observed once an object of interest has been located and releases reaching. Although patients with neglect exhibit a severe bias of exploratory movements, their hand trajectories to targets in peripersonal space may follow a straight path. This result suggests that (i) exploratory and (ii) goal-directed behaviour in space do not share the same neural control mechanisms. Neural representation of space in the inferior parietal lobule seems to serve as a matrix for spatial exploration and for orienting in space but not for visuomotor processes involved in reaching for objects. Disturbances of such processes rather appear to be prominent in patients with more superior parietal lobe lesions and optic ataxia.     

Preoperative functional magnetic resonance imaging (fMRI) of the motor system in patients with tumours in the parietal lobe

Intracranial lesions may compromise structures critical for motor performance, and mapping of the cortex, especially of the motor hand area, is important to reduce postoperative morbidity. We investigated nine patients with parietal lobe tumours and used functional MRI sensitized to changes in blood oxygenation to define the different motor areas, especially the primary sensorimotor cortex, in relation to the localization of the tumour. Activation was determined by pixel-by-pixel correlation of the signal intensity time course with a reference waveform equivalent to the stimulus protocol. All subjects showed significant activation of the primary sensorimotor cortex while performing a finger opposition task with the affected and unaffected side. In five patients the finger opposition task additionally activated the ipsilateral sensorimotor cortex and the supplementary motor area (SMA). Extension and flexion of the foot, additionally performed in two patients, also activated the sensorimotor cortex, in one case within the perifocal oedema of the tumour. Tumour localization near the central sulcus induced displacement of the sensorimotor cortex as compared to the unaffected side in all patients with a relevant mass effect. The results of our study demonstrate that functional MRI at 1.5 T with a clinically used tomograph can reproducibly localize critical brain regions in patients with intracranial lesions.     

Parietal lobe syndrome and schizophrenia: Comparison of neuropsychological deficits.

Investigated reported communalities in the perceptual impairments and body image distortions found after parietal lobe lesions and in schizophrenia. To compare these 2 syndromes, 15 patients with lesions of the parietal lobe and 15 patients with schizophrenia were tested on a neuropsychological battery designed to assess deficits in proprioception, tactile functions, and body image experience. Control groups consisted of 15 normal persons and of a series of 15 brain-injured cases in which the parietal lobe had been spared. Results indicate that both schizophrenic and parietally damaged Ss showed significant impairments in weight-discrimination measures of proprioceptive acuity when compared to the control brain-injured and normal Ss. No significant differences among groups were found on a comparable tactile size-estimation task, but the group with parietal injury exhibited a significant deficit in tactile sensory perception on the Finger Agnosia Test. Only the schizophrenic group showed evidence of disturbed body image when reality factors of body dysfunction were taken into account in the brain-injured patients. It is concluded that persons with schizophrenia and parietal lobe damage share a deficit in proprioception that may be based on different neurological substrates leading to (a) tactile impairments in cases with parietal damage, and (b) body-image disturbance in schizophrenia. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The assessment and treatment of patients who have sensory loss following cortical lesions

The assessment of tactile and proprioceptive sensory function in patients with severe sensory deficits resulting from cortical lesions is reviewed. The importance of using age-appropriate normative data to interpret the scores on these tests is discussed in the context of the frequency of ipsilateral disturbances in somesthetic sensation following unilateral cerebral lesions. Tactile and proprioceptive sensory deficits not only affect the processing of sensory information but also result in impairments in manual control. Fine-motor skills, such as those required for grasping and manipulating small objects, must therefore be evaluated in these patients. The treatment of patients with severe sensory deficits focuses on improving the perception of sensory information arising from receptors in the hand and on retraining motor function. The procedures used for sensory re-education and retraining are described.     

Behavioral analyses of visual cortex of the Galago..

To examine the function of primate visual cortex, the performance of 1 normal control group and 3 operated groups of Galago senegalensis (n?=?12) having bilateral cortical lesions in area 17, the middle temporal area (MT), or areas 18 and 19 (XS) was assessed on tasks measuring visual sensory capacity, search, and learning. Striate lesions produced a reduction in foveal vision and were responsible for deficits only on a complex visual learning task. The lesions of Group MT extended beyond the MT and involved the optic radiations. This resulted in impairments on all visual problems. Ss in Group XS had subtotal lesions of prestriate cortex and were also impaired on each task, but they showed less severe deficits in sensory capacity than Ss in Group MT. It is suggested that the Galago striate cortex plays a major role in the identification and utilization of relevant visual information and that areas 18 and 19 are important in both visual learning and visuospatial analyses. Evidence is provided that the MT is involved in visual search. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the reorganization of sensory hand areas after mono-hemispheric lesion: a functional (MEG)/anatomical (MRI) integrative study

The topography of primary sensory cortical hand area following a monohemispheric lesion (sudden = stroke; progressive = neoplasm) was investigated in relationship with clinical recovery of sensorimotor deficits. Twenty seven patients with monohemispheric lesions were studied in a clinically stabilized condition. Functional informations from magnetoencephalography (MEG) were integrated with anatomical data from magnetic resonance imaging (MRI). MEG localizations of the neurons firing at early latencies in primary sensory cortex after separate stimulation of median nerve, thumb and little fingers of each hand were carried out. Characteristics of cerebral equivalent current dipoles (ECDs) activated by each contralateral stimulation, the 'hand extension' (i.e., the distance in millimetres between ECDs of first and fifth digits), as well as interhemispheric differences of the tested parameters were investigated. Finally, ECDs' locations were integrated with MRI. Lesions involving cortical (C) or subcortical (s.c.) areas receiving sensory input from the hand were often combined to increase interhemispheric asymmetry of the tested parameters (22% for C and 49% for s.c. lesions). This might be due to an activation of neuronal districts which in the affected hemisphere (AH) differ from those normally activated in the unaffected hemisphere (UH) and in the control population. Moreover, the 'hand extension' was enlarged on the AH--more frequently after a SC lesion--mainly due to a medial shift of the little finger ECD, combined to a tendency of both finger ECDs to shift frontally. After a C lesion, responses from the AH were often stronger than normal. Spatial reorganizations were also seen in the UH (7% of C and 14% of SC lesions). 'Hand extension' in the UH was selectively enlarged for the P30m only when combined with a similar enlargement in the AH. Significant interhemispheric asymmetries due to neuronal reorganization in the AH were associated with worse clinical outcomes compared to patients without asymmetries.     

Visual control of the arm, the wrist and the fingers: pathways through the brain

Sperry and his colleagues had shown that section of the corpus callosum blocks the normally strong interocular transfer of visual learning in chiasma sectioned monkeys. Although interhemispheric transfer of learning was blocked, monkeys could be readily trained to use any combination of eye and hand in a task that required rapid visually guided responses. Sperry suggested that there must be a subcortical pathway linking sensory to motor areas of the brain. We tested monkeys in a task which required them to orient their wrist and fingers correctly in order to remove a morsel of food from a slotted disc. Animals in which we made lesions of the dorsal extrastriate visual areas of the parietal lobe were profoundly impaired in performing this task, but showed no deficit in visual discrimination learning. A monkey with an extensive lesion of the ventral, temporal lobe extrastriate areas showed no deficit in the visuomotor task but was profoundly impaired in visual discrimination learning. Lesions of peri-arcuate cortex, a major cortical target of parietal lobe visual areas, produced only a mild deficit which was motor in character. We suggest that the visuomotor deficit caused by parietal lobe lesions is brought about by depriving the cerebellum of its cortical visual input.     

Melatonin as an antiaging drug: between facts and fantasy

Structural neuroimaging has been used to correlate lesional patterns with the cognitive profile of patients with multiple sclerosis (MS), especially for "frontal" dysfunction. However, a clear-cut anatomical explanation has yet to be found for the long-term memory deficit which is a hallmark of MS cognitive impairment. We have used PET to measure regional cerebral glucose metabolism (rCMRglc) in a group of 15 MS patients with involvement of verbal and/or spatial long-term memory. These patients were compared with 10 normal controls and 13 MS patients unimpaired on all neuropsychological tests. Relative to the controls, MS patients with memory deficits showed a significant bilateral reduction of rCMRglc in the hippocampus, cingulate gyrus, thalamus, associative occipital cortex, and cerebellum. Direct comparisons between patients with memory deficits and the group of unimpaired MS patients showed a metabolic reduction in the left thalamus and in both hippocampi. Seven of the memory-impaired patients also had neuropsychological signs of frontal dysfunction. These patients were compared with patients who had isolated memory deficit. Here we observed a further metabolic reduction in a number of brain regions including bilateral prefrontal cortex, inferior parietal cortex, and basal ganglia. Our findings indicate that hypometabolism of thalamic and deep cortical gray structures of the temporal lobe is associated with episodic memory dysfunction in MS. On the other hand, pathological performance on tests designed to assess frontal functions was associated with widespread reduction of glucose metabolism.     

Effects of unilateral parietal lesions on spatial localization in the rat.

In the 1st of 2 experiments, rats with left or right parietal lesions and controls were tested in place and landmark navigation in the water maze. Right parietal lesions resulted in deficits in both tasks, but especially landmark navigation. Lateralized effects appeared mainly in latency to find the platform. Exp 2 investigated the role of the corpus callosum. Split-brain rats with unilateral parietal lesions were tested on the same 2 tasks. Place and landmark deficits were particularly severe, but lateralization was weaker. Callosum section had its own effect, impairing the learning of both tasks. There appear to be additive effects of unilateral cortical lesions and bisection of the hemispheres. The impairment from left lesions equaled the right-lesion deficit because of the interruption of compensatory information from the intact right hemisphere and the effect of callosum section itself. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

NF-kappaB2 is a putative target gene of activated Notch-1 via RBP-Jkappa

Cutaneous stimulation of the face and hand with a CO2 laser in three awake patients evoked potentials (LEPs) recorded from the dominant left parasylvian cortex. These were recorded by means of a subdural grid of electrodes implanted for evaluation of epilepsy. Stimulation of the contralateral face resulted in waveforms consisting of a negative potential (N2, 162 +/- 5 ms; mean +/- SE) followed by a positive potential (P2, 340 +/- 18 ms). Both waves occurred at longer latency after hand than after facial stimulation. N2 and P2 potentials recorded from the grid correspond well in morphology to those recorded from the scalp in four additional patients tested with the same stimulation paradigm. The N2 waves recorded from the subdural grid occurred at significantly shorter latencies than did those recorded from the scalp (184 +/- 6 ms), but the P2 waves at the grid occurred at significantly longer latencies than did those recorded at the scalp (281 +/- 13 ms). The amplitudes of the potentials recorded from the grid were maximal over the parietal operculum both for contralateral stimulation of the face or hand and for ipsilateral stimulation of the face. Potentials also were recorded in this area after stimulation of the ipsilateral hand. The cortical distributions of these potentials suggest that their generators are located in the parietal operculum or in the insula, or in both, consistent with previous PET, magnetoencephalographic, and scalp LEP source analyses. These previous analyses provide indirect evidence of nociceptive input to parasylvian cortex because the interpretation of each analysis incorporates multiple assumptions. The present results are the first direct evidence of nociceptive input to the human parasylvian cortex.     

Comparison of magnetoencephalography, functional MRI, and motor evoked potentials in the localization of the sensory-motor cortex

To clarify the topographical relationship between peri-Rolandic lesions and the central sulcus, we carried out presurgical functional mapping by using magnetoencephalography (MEG), functional magnetic resonance imaging (f-MRI), and motor evoked potentials (MEPs) on 5 patients. The sensory cortex was identified by somatosensory evoked magnetic fields using MEG (magnetic source imaging (MSI)). The motor area of the hand region was identified using f-MRI, during a hand squeezing task. In addition, transcranial magnetic stimulation localized the hand motor area on the scalp, which was mapped onto the MRI. In all cases, the sensory cortex was easily identified by MSI and the results of MSI correlated well with the findings obtained by the intraoperative recording of somatosensory evoked potentials. In contrast, the motor cortex could not be localized by f-MRI due to either the activated signal of the large cortical vein or the lack of any functional activation in the area of peri-lesional edema. MEPs were also unable to localize the entire motor strip. Therefore, at present, MSI is considered to be the most reliable method to localize peri-Rolandic lesions [corrected].     

A comparison of the contributions of the frontal and parietal association cortex to spatial localization in rats.

Compared 15 rats with lesions of the medial frontal, orbital frontal, or parietal cortex with 5 rats with complete removal of the neocortex and 5 normal controls on 3 spatial tasks: Morris water task, radial arm maze, and spatial reversals in a Grice box. Decortication produced severe impairments in the acquisition of all 3 tasks. Ss with parietal cortex lesions were relatively unimpaired at any of the tasks, although they had a significant deficit on the spatial reversal task and had a short-term memory impairment on the radial arm maze. In contrast, Ss with medial frontal lesions had a significant, but relatively mild, impairment on the radial arm maze and were poor at learning the water task. Ss with orbital frontal lesions were nearly as impaired on the radial arm maze and water task as decorticate Ss. Results suggest that the frontal and parietal cortex of rats play different roles in the control of spatial orientation but do not support the view that egocentric and allocentric spatial orientation are related to frontal and parietal mechanisms, respectively. In addition, results suggest that the frontal cortex plays a larger role in the control of spatially guided behavior than has been previously recognized and that both the medial frontal and the orbital frontal cortex play a dissociable role in the control of spatial orientation. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Strategic processing and memory for temporal order in patients with frontal lobe lesions.

This study evaluated whether deficits in memory for temporal order in patients with frontal lobe lesions result from impaired automatic encoding of temporal information or are secondary to deficits in effortful processes, such as the use of organizational strategies and control of interference. Patients with lesions in the dorsolateral prefrontal cortex and control participants were tested on temporal order reconstruction of semantically related and unrelated word lists learned under intentional or incidental conditions. Memory for temporal order in patients with frontal lobe lesions was sensitive to semantic relatedness but not to intention to learn. Tests of item free recall and recognition using similar encoding manipulations indicated that order performance in these patients was dissociable from item memory. Results indicate that automatic processing of temporal information is intact in patients with frontal lobe lesions but that strategic processing of this information is impaired. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrical microstimulation distinguishes distinct saccade-related areas in the posterior parietal cortex

Electrical microstimulation (0.1-ms bipolar pulses at 500 Hz, current strength usually between 100 and 200 microA) was used to delineate saccade-related areas in the posterior parietal cortex of monkeys. Stimulation-induced saccades were found to be restricted to the lateral intraparietal area (area LIP) in the intraparietal sulcus (IPS) and a region on the medial aspect of the parietal lobe (area MP, medial parietal area), close to the caudal end of the cingulate sulcus, whereas stimulation of area 7a did not evoke eye movements. Two different types of evoked saccades were observed. Modified vector saccades, whose amplitude was modified by the position of the eyes at stimulation onset were the hallmark of sites in area LIP and area MP. The same sites were characterized by a propensity of single units active in the memory and presaccadic response segments of the memory saccade paradigm. Goal-directed saccades driving the eyes toward a circumscribed region relative to the head were largely restricted to a small strip of cortex on the lateral bank and the floor of the IPS (the intercalated zone), separating the representation of upward and downward directed saccades in LIP. Unlike stimulation in LIP or MP, stimulation in the intercalated zone gave rise to head, pinnae, facial, and shoulder movements accompanying the evoked saccades. We propose that the amplitude modification of vector saccades characterizing LIP and MP may reflect a spatially distributed head-centered coding scheme for saccades. On the other hand, the goal-directed saccades found in the intercalated zone could indicate the use of a spatially much more localized representation of desired location in head-centered space.     

Expression of multidrug resistance (mdr) gene(s) in primary lymphoid organs of chicken immune system during embryonic development

The present study investigated the processing of painful electrical stimuli in patients with unilateral frontal or parietal lobe damage and matched control subjects. Patients with frontal lesions showed increased pain thresholds when the stimuli were administered contralateral to the lesion. While the peak-to-peak amplitudes of the N150/P250 components of the somatosensory potentials increased linearly with stimulus intensity in the control subjects, the responses in the frontal group did not change significantly between stimulation at pain and tolerance threshold. There was no evidence for altered pain processing in patients with parietal lobe lesions. The findings of the present study support the hypothesis of an involvement of the frontal cortex in pain perception in humans.     

The transcriptional effects and DNA-binding specificities of 17beta-estradiol after dimethyldioxirane activation

We investigated the spatio-temporal brain activity on the time scale of several milliseconds related to the mental rotation task requiring judgements of hand orientation, using a whole-cortex MEG (magnetoencephalography) system. Neuronal activity in the visual cortex was observed approximately 100-200 ms from stimulus onset, and that in inferior parietal lobe followed (after 200 ms). Both of these activities showed a contralateral dominance to visual stimulus hemifield. Premotor activity started later than the inferior parietal lobe activity, and these activities partially overlapped. Activity in primary motor and/or motosensory areas was observed in some subjects. The whole-cortex neuromagnetic measurements provided the time course of activity in the human brain associated with the implicit motor imagery: visual cortex-->inferior parietal lobe<-->premotor cortex. This process is considered to be the transformation process of retinotopic locations into a body-centered reference frame necessary for the mental rotation task.     

Surgical management of intractable epilepsy in patients with ganglioglioma

Long-standing intractable seizures are common manifestation of cerebral gangliogliomas. There is much controversy regarding the most appropriate surgical treatment (lesionectomy vs resection of the epileptogenic cortex with the lesion) for patients with intractable epilepsy associated with gangliogliomas. We reported 2 cases, in which the favorable seizure outcome was obtained following lesionectomy alone. (Case 1) Nine-year-old female developed attack of abnormal sensation in her left upper limb followed by motor seizure in her left limbs since 5 years old. MRI revealed hyperintense tumor in the right medial frontal lobe. Chronic invasive subdural recording showed that ictal onset zone was located in the hand motor area. Following lesionectomy alone, she became free from seizures. (Case 2) Eight-year-old girl had intractable generalized seizure since 6 years old. MRI revealed a cystic tumor in the right parietal lobe. She had multiple spike foci on electroencephalography and magnetoencephalography, and intraoperative electrocorticography failed to reveal the paroxysm. Following lesionectomy, she had good relief with less than one minor seizure per 1-3 months. Thus, lesionectomy, even without resection of the epileptogenic cortex, may improve seizure outcome in patients with ganglioglioma-associated epilepsy.     

Effects of divided attention on temporal processing in patients with lesions of the cerebellum or frontal lobe.

Prefrontal cortex and cerebellum have both been implicated in temporal processing tasks although the exact contribution of each system remains unclear. To investigate this issue, control participants and patients with either prefrontal or cerebellar lesions were tested on temporal and nontemporal perceptual tasks under 2 levels of attentional load. Each trial involved a comparison between a standard tone and a subsequent comparison tone that varied in frequency, duration, or both. When participants had to make concurrent judgments on both dimensions, patients with frontal lobe lesions were significantly impaired on both tasks whereas the variability of cerebellar patients increased in the duration task only. This dissociation suggests that deficits on temporal processing tasks observed in frontal patients can be related to the attention demands of such tasks; cerebellar patients have a more specific problem related to timing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The decoding of emotional concepts in patients with focal cerebral lesions

The effects of focal brain lesions on the decoding of emotional concepts in facial expressions were investigated. Facial emotions are hierarchically organized patterns comprising (1) structural surface features, (2) discrete (primary) emotional categories and (3) secondary dimensions, such as valence and arousal. Categorical decoding was measured using (1) selection of category labels and selection of the named emotion category; (2) matching one facial expression with two choice expressions. Dimensional decoding was assessed by matching one face with two different expressions with regard to valence or arousal. 70 patients with well documented cerebral lesions and 15 matched hospital controls participated in the study. 27 had left brain damage (LBD; 10 frontal, 10 temporal, 7 parietal); 37 had right brain damage (RBD; 15 frontal, 11 temporal, 11 parietal). Six additional patients had lesions involving both frontal lobes. Right temporal and parietal lesioned patients were markedly impaired in the decoding of primary emotions. The same patients also showed a reduced arousal decoding. In contrast to several patients with frontal and left hemisphere lesions, emotional conceptualization and face discrimination was not independent in these groups. No group differences were observed in valence decoding. However, right frontal lesions appeared to interfere with the discrimination of negative valence. Moreover, a distraction by structural features was noted in RBD when facial identities were varied across stimulus and response pictures in matching tasks with differing conceptual load. Our results suggest that focal brain lesions differentially affect the comprehension of emotional meaning in faces depending on the level of conceptual load and interference of structural surface features.     

Pretherapy dental decisions in patients with head and neck cancer. A proposed model for dental decision support

OBJECTIVE: Sensory and motor abnormalities are common among patients with complex regional pain syndrome (CRPS). The purpose of the present study was to define and characterize these abnormalities and to develop a hypothesis regarding the area of the central nervous system from which they derive. DESIGN: Data were acquired from study subjects using clinical examination and quantitative assessment of neurological function. Subjects were divided into four groups. CRPS patients were differentiated into two groups based on the presence or absence of sensory deficit on the face to clinical examination. The other two groups were composed of patients with other chronic pain syndromes and normal individuals without chronic pain or disability. Clinical and quantitative data were compared between groups. PATIENTS: One hundred forty-five CRPS patients, 69 patients with other pain conditions, and 26 normal individuals were studied. RESULTS: A high incidence of trigeminal hypoesthesia was observed in CRPS patients. CRPS patients with trigeminal hypoesthesia manifested bilateral deficits of sensory function, with a predominant hemilateral pattern. These patients also manifested bilateral motor weakness with a more prominent hemiparetic pattern. Both sensory and motor deficits were greatest ipsilateral to the painful side of the body. These features differed significantly from those of CRPS patients lacking clinical trigeminal deficit, other pain patients, and normals. A lower cranial nerve abnormality (sternocleidomastoid weakness) and a myelopathic feature (Hoffman's reflex) were more common in CRPS patients with trigeminal hypoesthesia. CONCLUSIONS: Nearly half of CRPS patients had abnormalities of spinothalamic, trigeminothalamic, and corticospinal function that may represent dysfunction of the medulla. One-third of the remaining CRPS patients had neuroimaging evidence of spinal cord or brain pathology. The majority of CRPS patients in this study have measurable abnormalities of the sensory and motor systems or neuroimaging evidence of spinal cord or brain dysfunction.