Sensorimotor responsiveness in rats with unilateral superior collicular and amygdaloid lesions.

Large unilateral lesions of superior colliculus, but not amygdala, result in strong ipsiversive progression tendencies and permanent neglects of visual, auditory, and whisker-touch stimuli presented on the contralateral side of the body. Combined collicular-amygdaloid lesions also yield circling behaviors and multimodal neglects that are completely independent of the order or laterality of the amygdaloid lesion. Rats with colliculectomy either neglect or else turn away from pinches of the contralateral ear and forepaw. Subjects with combined lesions display more crossed orientations, and this tendency is greatly potentiated by ipsilateral lesion placement. The nature and time course of the crossed response in rats with sensory neglects is reminiscent of the clinical syndrome described as alloaesthesia or as contralateral sensory displacement.     

The thalamus and basal ganglia: What is exactly where?: A reply to ‘Neuropsychological consequences of right thalamic injury: Case study and review,’ MJ Summers, Brain and Cognition 50 (2002)

The present paper re-analyzes anatomical and clinical data of a previous case report ([Summers, 2002]). In this case study, a patient with severe neuropsychological and behavioral impairments is described and it is claimed that these impairments are causally linked to an right thalamic lesion. A simple method how to perform a lesion analysis is introduced which shows that PD’s lesion was a striatocapsular hematoma, and not a thalamic bleeding. The results of this anatomical re-analysis challenge the original behavioral-lesion hypothesis and emphasize the importance to provide appropriate data on brain lesions and clinical findings in neuropsychological case reports.     

The thalamus and basal ganglia: What is exactly where? A reply to 'Neuropsychological consequences of right thalamic injury: case study and review,' MJ Summers, Brain and Cognition 50 (2002)

The present paper re-analyzes anatomical and clinical data of a previous case report (Summer, 2002). In this case study, a patient with severe neuropsychological and behavioral impairments is described and it is claimed that these impairments are causally linked to an right thalamic lesion. A simple method how to perform a lesion analysis is introduced which shows that PD's lesion was a striatocapsular hematoma, and not a thalamic bleeding. The results of this anatomical re-analysis challenge the original behavioral-lesion hypothesis and emphasize the importance to provide appropriate data on brain lesions and clinical findings in neuropsychological case reports.     

Persisting apraxia in two left-handed, aphasic patients with right-hemisphere lesions

Apraxia usually follows a left hemisphere lesion in right-handers with left hemisphere speech representation. Apraxia following a right hemisphere lesion in left-handers is rare, however, and not well documented in the literature. Two left-handed patients are described in whom apraxia and aphasia followed a right hemisphere lesion. Both the apraxic and the aphasic deficits improved but were still demonstrable 6 weeks following the infarct. The data are consistent with those for right-handers with left hemisphere lesions in suggesting some overlap of anatomical structures for the control of speech and praxis.     

The opercular-subopercular syndrome: four cases with review of the literature

We present four cases of the 'opercular syndrome' of volitional paresis of the facial, lingual, and laryngeal muscles (bilateral facio-glosso-pharyngo-masticatory paresis). Case histories and CT brain images are presented, along with a review of the literature concerning this long-recognized but little-known syndrome. The neuroanatomic basis of the syndrome classically involves bilateral lesions of the frontal operculum. We propose, on the basis of our cases and others, that the identical syndrome can arise from lesions of the corticobulbar tracts, not involving the cortical operculum. Our cases included one with bilateral subcortical lesions, one with a unilateral left opercular lesion and a possible, non-visualized right hemisphere lesion, one with unilateral cortical and unilateral subcortical pathology, and one with bilateral cortical lesions. These lesion localizations suggest that any combination of cortical or subcortical lesions of the operculum or its connections on both sides of the brain can produce a syndrome indistinguishable from the classical opercular syndrome. We propose the new term 'opercular-subopercular syndrome' to encompass cases with predominantly or partially subcortical lesions.     

Psychometric and CT scan measurements in a case of crossed aphasia in a dextral

A case of crossed aphasia with lesion deep to the right supramarginal gyrus was studied to determine (1) if this patient behaved similar to patients with the same lesion site in the left hemisphere, (2) if visuospatial deficits were present, and (3) if the CT scan asymmetries were similar to those of other right-handers. Speech and language skills were similar to those patients with similar lesions in the left hemisphere. Visuospatial and arithmetic deficits were similar to those described after right-hemisphere and left-hemisphere damage. CT scan asymmetries were atypical. These results provide behavioral and neuroradiological confirmation of atypical hemispheric dominance.     

Handling from weaning to adulthood does not prevent hyperdefensiveness induced by septal, medial accumbens, or medial hypothalamic lesions

Weanling male hooded rats were handled or not handled for 10 min each day, 5 days/week, for 6 weeks. At the end of this time all animals received one of the following: a septal lesion, a medial accumbens lesion, a medial hypothalamic lesion, or a sham lesion. The animals were tested for defensiveness toward the experimenter on Days 3, 7, and 14 postoperatively. All behavioral testing was done blind. Each of the three lesions increased defensiveness toward the experimenter. However, with each lesion, there was no difference in the defensiveness scores of preoperatively handled and nonhandled animals at any of the postoperative test sessions while those of animals with medial hypothalamic lesions did not. These results are consistent with observations that hyperdefensiveness occurs in human subjects following tumors in each of these brain areas in spite of their familiarity with the situation in which they are observed. They contrast with observations that mouse killing induced by septal lesions is readily prevented by preoperative exposure to a mouse.     

Physiological changes during operations on the limbic system in man

The limbic system is a phylogenetically old part of the brain which is concerned with a variety of emotional and viscerosomatic functions. It has been found that small discrete lesions, placed by stereotaxis in this system during limbic leukotomy, may result in marked clinical improvement in severely incapacitated psychiatric patients who have failed to respond to any other type of treatment. In one patient, electrical stimulation of the anterior cingulate gyrus was carried out under local anesthesia to locate a suitable site for a limbic lesion. Physiological arousal was produced, as evidenced by changes in heart rate, forearm blood flow, sweat gland activity and respiration. Bilateral lesions, 8 mm in diameter, produced by freezing this site, resulted in marked clinical improvement. Peripheral physiological changes are now being used to aid in the selection of target sites in various parts of the limbic system. Under general anesthesia marked respiratory changes have been found on stimulation of the lower medial quadrant of the frontal lobe, anterior cingulate gyrus, above the roof of the lateral ventricle, and in the amygdala nucleus of the temporal lobe. Lesions are made with a cryogenic probe at sites of maximum physiological response. It is postulated that physiological monitoring during electrical stimulation of target areas will improve the accuracy of lesion placement. Some of the results of this procedure are described.     

Neocortex and feeding behavior in the rat.

Consummatory behavior and weight-regulation capacity were measured in 12 normal rats and in 43 rats that survived complete (C), sequential unilateral (U), anterolateral (A), or posterior (P) neocortical ablations. Groups C and A displayed aphagia and adipsia followed by a sequence of recovery stages gualitatively identical to, but shorter than, recovery typically seen following lateral hypothalamic lesions. After recovery, Group C displayed long-term effects of finickiness and pradial drinking. These effects as well as a measure of recovery of body-weight-regulation capacity were significantly intercorrelated with lesion size, and body-weight set point remained significantly lower than normal. Group U was relatively unaffected by the first unilateral ablation and showed, relative the second ablation but displayed the long-term effects. Group P, though significantly affected by the lesion, did not display the pattern or intensity of effects described for the other bilaterally ablated groups.     

Transient manic behavior after pallidotomy

We report two cases of transient hypomanic behavior following pallidotomy. Both of the reported patients had lesions involving non-motor portions of the globus pallidus. Patient 1 had a lesion in the left anteromedial portion of GPi, while patient 2 had one lesion involving the anteromedial portion of GPi on the right and a second lesion involving the postero-ventral most portion of the putamen on the left. These cases emphasize the importance of placing lesions within the sensori-motor portion of GPi without infringing on adjacent non-motor portions. Cases involving transient manic behavior after pallidotomy have not been previously reported. Centers performing pallidotomy or DBS should be aware that lesions or stimulation too anterior in the GPi might lead to manic behavior.     

Quantification of brain lesions using interactive automated software

We developed an interactive program, Analysis of Brain Lesions (ABLe) so that researchers studying the effects of brain lesions on cognition could have a user-friendly tool that could quantitatively characterize such lesions. The program was prepared in Tcl/Tk and will run on any UNIX or PC LINUX platform with the MEDx medical imaging software package. The ABLe is almost completely automated and determines the brain lesion size as well as which cytoarchitectonic brain regions (Brodmann areas) are contained within the boundaries of the lesion. Lesion data from multiple subjects can be grouped together and the degree of lesion overlap displayed. All images are analyzed and displayed within standard Talairach coordinate space, and the precision of the match between the ABLe Brodmann area graphics and the subject/patient brain is easily confirmed. The program is the first easy-to-use software that contains these specific features and is available for interested researchers with a background in lesion analysis.     

Basal ganglia participation in language pathology

Language disturbances were studied in 40 patients with well-demarcated vascular lesions of the speech-dominant hemisphere. Computerized cranial tomography was used for localization of the lesion. Special emphasis was given to the analysis of automatized speech and repetitive verbal phenomena.Subcortical infarctions with basal ganglia involvement led to transient aphasia although long-lasting abnormalities of language could be detected in these patients. Aphasia was more severe if a cortical lesion was combined with a basal ganglia lesion. Automatisms and recurring utterances occurred only with combined cortical and basal ganglia lesions. A lesion of Wernicke's area alone, without involvement of prerolandic structures or subcortical nuclei, was sufficient to produce long-lasting aphasia, whereas lesions of Broca's area alone produced only transient language disturbances. The results are compatible with a recent theory of multiple cerebral representation of function.     

Differential effect of lesion side on intra-individual variability in children with focal lateralized epilepsy

A differential impact of hemispheric side (left vs right) on cognitive measures, specifically Verbal and Performance IQ, has been described previously for both focal onset seizures and lateralized brain lesions. This study revealed a differential effect on intra-individual variability, measured as subtest scaled-score range, on the Dutch WISC-R and WISC-III, in children with epilepsy. The presence of documented brain lesion was associated with elevated variability on the Verbal Scale for the left hemisphere seizure group and with decreased variability on the Verbal and Full Scales for the right hemisphere seizure group.     

Effects of medial and lateral septal lesions on the partial reinforcement extinction effect at one trial a day

Rats sustained electrolytic lesions of either the medial septal (MS) area (of a kind known to eliminate the hippocampal theta rhythm) or the dorso-lateral septal (LS) area (of a kind known to spare theta) or both (a “total septal”, TS, lesion). They were compared to sham-operated controls in three experiments in the straight alley with food reward on continuous (CRF) or partial (PRF) reinforcement at one trial a day. MS lesions either left the partial reinforcement extinction effect (PREE) unchanged or enhanced it; LS lesions substantially reduced the PREE. The latter effect was due to a fall in resistance to extinction in PRF animals with no change in CRF animals. MS lesions greatly increased resistance to extinction in both CRF and PRF animals in one experiment but increased resistance to extinction only marginally and only in PRF animals in a second experiment. The TS lesion acted like the LS lesion. These results demonstrate a clear double dissociation between the effects of MS and LS lesions, especially in the PRF condition (LS lesions reduce resistance to extinction, MS lesions increase it).     

The impact of lesion laterality on neuropsychological change following posterior pallidotomy: a review of current findings

This paper reviews seven studies evaluating the impact of lesion laterality on the neuropsychological sequelae of posterior pallidotomy for treatment of Parkinson's disease. Left lesions of the internal globus pallidus (GPi) were associated with subtle deficits on measures sensitive to frontal lobe function. The findings of a randomized clinical trial including a patient control group indicated that many of these deficits were transient, resolving by 6 months following surgery. Right GPi lesions were not consistently associated with neuropsychological deficit, except in one study that included a significant proportion of demented patients. It is hypothesized that when neuropsychological decline is present following surgery, this reflects impingement of posterior GPi lesions into proximal regions such as anterior GPi or the external pallidum that participate in cognitive basal ganglia-thalamocortical circuits. The findings from neuroimaging will be important for elucidating the relationship between lesion locus and neuropsychological sequelae.     

Lesions of the rat nucleus basalis magnocellularis disrupt appetitive-to-aversive transfer learning

Rats with selective lesions of the nucleus basalis magnocellularis (NBM) and sham-lesion control animals were tested in an operant appetitive-to-aversive transfer task. We hypothesized that NBM lesions would not affect performance in the appetitive phase, but that performance would be impaired during subsequent transfer to the aversive phase of the task. Additional groups of NBM lesion and control rats were tested in the avoidance condition only, where we hypothesized that NBM lesions would not disrupt performance. These hypotheses were based, on the argument that the NBM is not necessary for simple association learning that does not tax attention. Both the appetitive phase of the transfer task and the avoidance only task depend only on simple associative learning and are argued not to tax attention. Consequently, performance in these tasks was predicted to be spared following NBM lesions. Complex, attention-demanding associative learning, however, is argued to depend on the NBM. Performance, in the aversive phase of the transfer task is both attentionally demanding and associatively more complex than in either the appetitive or aversive tasks alone; thus, avoidance performance in the NBM lesion group was predicted to be impaired following transfer from prior appetitive conditioning. Results supported our hypotheses, with the NBM lesion group acquiring the appetitive response normally, but showing impaired performance following transfer to the aversive conditioning phase of the transfer task. Impairments were not attributable to disrupted avoidance learning per se, as avoidance behavior was normal in the NBM lesion group tested in the avoidance condition only.     

Lesions of the Rat Nucleus Basalis Magnocellularis Disrupt Appetitive-to-Aversive Transfer Learning

Rats with selective lesions of the nucleus basalis magnocellularis (NBM) and sham-lesion control animals were tested in an operant appetitive-to-aversive transfer task. We hypothesized that NBM lesions would not affect performance in the appetitive phase, but that performance would be impaired during subsequent transfer to the aversive phase of the task. Additional groups of NBM lesion and control rats were tested in the avoidance condition only, where we hypothesized that NBM lesions would not disrupt performance. These hypotheses were based on the argument that the NBM is not necessary for simple association learning that does not tax attention. Both the appetitive phase of the transfer task and the avoidance only task depend only on simple associative learning and are argued not to tax attention. Consequently, performance in these tasks was predicted to be spared following NBM lesions. Complex, attention-demanding associative learning, however, is argued to depend on the NBM. Performance in the aversive phase of the transfer task is both attentionally demanding and associatively more complex than in either the appetitive or aversive tasks alone; thus, avoidance performance in the NBM lesion group was predicted to be impaired following transfer from prior appetitive conditioning. Results supported our hypotheses, with the NBM lesion group acquiring the appetitive response normally, but showing impaired performance following transfer to the aversive conditioning phase of the transfer task. Impairments were not attributable to disrupted avoidance learning per se, as avoidance behavior was normal in the NBM lesion group tested in the avoidance condition only.     

Supra- and infrasylvian conduction aphasia

Fifteen cases of conduction aphasia which were tested with the Aachen Aphasia Test (AAT), are presented. The CT lesion data were transformed to a standard 3D-reference brain referring to the ACPC line. According to the lesion profiles a group of 6 patients had pure suprasylvian lesions, a group of 4 patients had pure infrasylvian lesions, and a group of 5 patients had lesions in both supra- and infrasylvian regions. Suprasylvian conduction aphasics are superior to infrasylvian conduction aphasics in the token test and in repetition tasks. Infrasylvian conduction aphasics use more stereotypes in spontaneous speech than suprasylvian conduction aphasics. Conduction aphasics with both lesion sites perform less well in tests of naming, writing, and comprehension than the pure types. Thus conduction aphasia is a heterogeneous syndrome anatomically and linguistically.     

Aphasia in left-handers. Comparison of aphasia profiles and language recovery in non-right-handed and matched right-handed patients.

The present retrospective analysis reports two studies. In Study 1, clinical aspects of aphasia are compared in right-handed (RH) and non-right-handed (NRH) patients; in Study 2, recovery from aphasia is compared in RH and NRH aphasic patients with a minimum of 5 months of daily language rehabilitation. From a continuous series of 1200 brain-damaged subjects, 24 NRH patients with a vascular lesion documented by computerized tomography were selected. In 19 cases the lesion was in the left hemisphere and in 5 cases in the right hemisphere. For 14 NRH patients, a RH subject with similar lesion, matched for age, education, length of illness, etiology (ischemic vs. hemorrhagic), and, when possible, sex was found. Presence and type of aphasia were compared in the two patients of the same pair and were found similar except for Pair 14; the RH subject had global aphasia and the NRH had conduction-like aphasia. Fifteen NRH patients were rehabilitated and reexamined at least 5 months after the first examination. Recovery of the 12 patients with a left-hemisphere lesion was compared with recovery of a group of RH subjects and no significant differences were found. Recovery of the three patients with right-hemisphere lesions is described. It is concluded that differences in type of aphasia and recovery between RHs and NRHs have been overemphasized in the past and must be reconsidered.