Atypical cerebral dominance: predictions and tests of the right shift theory

Alexander and Annett (Brain and Language, in press) described new cases of atypical cerebral specialization, and suggested that these observations and others in the literature could be explained by the right shift (RS) theory. The theory generates specific predictions as to the prevalence of different patterns of cerebral dominance and their distribution among right-handers and left-handers. Predictions differ between strict and generous criteria of sinistrality, as between left writers and non-right-handers. Tests of the predictions against reports in the literature reveal good fits for most data. New studies will test the RS theory if their design permits examination of the present predictions.

Pathological crying and laughing: treatment with sertraline

OBJECTIVE

To evaluate the efficacy of sertraline for treating pathological laughing and crying after stroke.

DESIGN

Case series.

SETTING

Inpatient rehabilitation units of a community and a tertiary-care hospital.

PATIENTS

One patient was a 62-year-old right-handed man who had two strokes approximately 2 years apart and had computed tomography consistent with a cerebral infarct involving the left middle cerebral artery branches in the left parietal lobe. A second patient was a 72-year-old right-handed man who had a right middle cerebral artery infarct. He had a questionable history of depression prior to the stroke.

INTERVENTION

Both patients had poststroke labile affect that was interfering with their rehabilitation. Sertraline was prescribed.

MAIN OUTCOME MEASURES

Pretreatment and posttreatment scores on the Pathological Crying and Laughing Scale and Functional Independent Measure.

RESULTS

Both patients showed significant improvement after taking sertraline-improvement that was reflected in their pretreatment and posttreatment scores on the Pathological Crying and Laughing Scale and Functional Independent Measure. The staff noted improvements in sleeping, eating, social interaction, and therapy participation. Both patients tolerated the sertraline well and had no significant side effects.

Illusory memories: a cognitive neuroscience analysis

Memory illusions and distortions have long been of interest to psychology researchers studying memory, but neuropsychologists and neuroscientists have paid relatively little attention to them. This article attempts to lay the foundation for a cognitive neuroscience analysis of memory illusions and distortions by reviewing relevant evidence from a patient with a right frontal lobe lesion, patients with amnesia produced by damage to the medial temporal lobes, normal aging, and healthy young volunteers studied with functional neuroimaging techniques. Particular attention is paid to the contrasting roles of prefrontal cortex and medial temporal lobe structures in accurate and illusory remembering. Converging evidence suggests that the study of illusory memories can provide a useful tool for delineating the brain processes and systems involved in constructive aspects of remembering.

Precipitants of brain infarction. Roles of preceding infection/inflammation and recent psychological stress

BACKGROUND AND PURPOSE

Antecedent febrile infection and psychological stress are described as predisposing risk factors for brain infarction. We examined the temporal relationship between preceding infection/inflammation and stroke onset as well as the role of recent psychological stress as a potential precipitant for brain infarction.

METHODS

In this case-control study, a standardized evaluation including a signs/symptoms-based questionnaire was used to characterize the prevalence and timing of recent prior (< 1 month) infectious and inflammatory syndromes in 37 adults with acute brain infarction, 47 community control subjects, and 34 hospitalized nonstroke neurological patient controls. Recent psychological stress was measured with scales of stressful life events and negative affect.

RESULTS

The prevalence of infection/inflammation was significantly higher in the stroke group only within the preceding 1 week compared with either community control subjects (13/37 versus 6/47, P < .02) or hospitalized neurological patient controls (3/34, P < .02). Upper respiratory tract infections constituted the most common type of infection. A substantial proportion of stroke patients with preceding (< 1 week) infection/inflammation (5/13) had no accompanying fever or chills. There were no significant differences between the stroke and control groups in the levels of stressful life events within the prior 1 month or in negative-affect scale scores within the prior 1 week.

CONCLUSIONS

Our data suggest that both febrile and nonfebrile infectious/inflammatory syndromes may be a common predisposing risk factor for brain infarction and that the period of increased risk is confined within a brief temporal window of less than 1 week. Results of this study argue against a role for recent psychological stress as a precipitant for cerebral infarction.

Sensorimotor impairments in rats with cerebral infarction, induced by unilateral occlusion of the left middle cerebral artery: strain differences and effects of the occlusion site

Enormous differences exist between rat strains with respect to the infarct volume induced by unilateral middle cerebral artery (MCA) occlusion. We performed three experiments to address the following questions. Firstly, whether the pattern of MCA-occlusion (MCA-O) induced sensorimotor impairments in rats are strain dependent; secondly, whether proximal (i.e., close to its origin) and distal occlusions (above the lenticulostriate branch) of the MCA affect infarct volume and the behavioral impairments to a different extent; and thirdly, whether there is a relationship between the infarct volume and behavioral deficits. We found that the pattern of sensorimotor malfunctions induced by proximal unilateral MCA-O were highly strain dependent. Of the eight strains tested, Winkelmann-Wistar rats, Spontaneously Hypertensive Stroke-Prone rats, and Wistar-Kyoto rats were most severely affected. By contrast, Brown-Norway rats showed only mild behavioral deficits after the MCA-O. The second experiment confirmed that proximal occlusions induced slightly more behavioral malfunctions than distal occlusions did. Histological evaluation of the brain damage caused by proximal and distal MCA-O, confirmed that distal MCA-O damaged nearly exclusively cortical areas, and spared the caudate/putamen. An exploratory analysis of the relationship between infarct volume and behavioral deficits did not indicate that the severity of sensorimotor malfunctions can be predicted from the size of the infarct.

Object-centered not scene-based visual neglect

Whether visuospatial attention accesses object-centered representations, in addition to location-based coordinates, was investigated in patients with hemispatial neglect who detected a target on the left or right of a single object (2 connected circles or barbell) or of 2 objects (2 unconnected circles). The object or objects either remained static (left circle in left space) or rotated by 180 degrees (left circle now in right space). Relative to the static condition, in the rotating condition, detection times are facilitated on the left (contralateral) and inhibited on the right (ipsilateral) of space even when eye movements are controlled. This modulation of neglect was only observed for the single object, but not for the 2-object displays. The findings suggest that attention operates on object-centered as well as on location-based representations, and thus accesses multiple reference frames.

Unreliability of TRH test but not dexamethasone suppression test as a marker of depression in chronic vasculopathic patients

Thirteen vasculopathic nondepressed men, admitted to the hospital 2 weeks earlier because of stroke, 10 age- and weight-matched patients with major depression, and 10 age- and weight-matched normal controls were tested with TRH and on different occasion with the dexamethasone (DEX) suppression test (DST). Patients with stroke were tested again with TRH and DST after 1 year. All subjects were euthyroid. A blunted TSH response to TRH was observed in 77% of vasculopathic patients, 64% of depressed patients, and 27% of controls. Some depressed patients showed serum GH or cortisol increments in response to TRH. Nonsuppression to DEX was observed in 45% of depressed patients and 15% of vasculopathics but not in normal controls. These data indicate that, in contrast to cortisol nonsuppression to DEX, blunted TSH response to TRH has poor diagnostic value as a marker for depression after stroke and may merely represent the expression of neuroendocrine dysfunction associated with cerebral vasculopathy.

Bipolar disorder following a stroke involving the left hemisphere

OBJECTIVE

Post-stroke mania has rarely been noted and researched, and reported cases have mostly involved the non-dominant hemisphere. In this paper, we report a case of bipolar disorder secondary to a stroke over the dominant hemisphere.

CLINICAL PICTURE

A 48-year-old, right-handed man had a cerebral infarct over the left temporal region. He became depressed after the stroke, and 4 months later developed a manic episode.

TREATMENT

The patient was treated with haloperidol and lorazepam.

OUTCOME

The symptoms subsided within 2 months after treatment.

CONCLUSIONS

It is premature to consider mania to be a syndrome of the right, or non-dominant, hemisphere. We suggest that further study focusing on specific anatomical regions, rather than laterality, will help to elucidate the interrelationship between mood and brain function.

The validity of observed depression as a criteria for mood disorders in patients with acute stroke

The validity of observed depression as a criteria for major or minor depression was assessed among 301 patients with acute stroke. Patients who acknowledged a depressed mood or loss of interest (standard depression) were compared to patients who denied depression but were 'observed' to be depressed (non-standard depression) for the clinical correlates of depression. Although standard and non-standard major depressions had some clinical correlates such as increased frequency of female gender and prior psychiatric history, standard major depression patients had a significantly higher frequency of left hemisphere lesions than the non-standard major depression patients. These results support the validity of 'observed' depression as a criteria for major depression but also suggest the possibility that failure to report depressed mood may identify a condition with a different etiology than depression that is recognized and acknowledged. Observed depression, however, was not validated among patients with minor depression since there were no clinical or phenomenological differences from non-depression.

Hemispheric antagonism in visuo-spatial neglect: a case study

We report a case of severe visuo-spatial neglect consequent upon right-hemisphere stroke. At the time of testing, the patient had no visual field cut and no significant hemiparesis. Conventional testing on cancellation tasks with the right hand revealed reliable left neglect, but performance was significantly improved when the left hand was used. Investigations of (manual) line bisection showed normal performance with the right hand but right neglect when the left hand was used. Right neglect was also observed on a purely perceptual version of the line bisection task. We argue that the attentional vectors of the cerebral hemispheres can be modulated by (perceptual) task-demands and by (motoric) response-demands.

Effects of hand-used on unilateral spatial neglect: a case study

It was originally claimed that left hand use on line bisection tasks reduced the extent of left neglect by Halligan and Marshall. However, in a following study, the same research group failed to reproduce this left hand amelioration effect if the left hand was initially placed on the right side, and they claimed that spatio-motor cueing was more important in reducing unilateral neglect than the hand used. The present study concerns with the validity of these two theoretical views on modification of unilateral neglect, i.e., hemispheric activation and spatio-motor cueing. A patient with left unilateral neglect and a slight left hemiparesis participated in three experiments. Under conventional testing condition, line bisection performed with the right hand showed more severe left neglect than when performed with the left hand. These hand effects were modified by changing a starting position of the patient's hand when bisecting horizontal lines. However, under body-fixed condition, effects in hand-used as well as starting position were again significant. The results suggest that not only spatio-motor cueing but also differential hemispheric activation can exert a profound effect on unilateral neglect.

Visual neglect associated with frontal lobe infarction

Five patients with left-sided visual neglect following focal infarction of the right frontal lobe are presented. Lesion location was assessed using computed tomography or magnetic resonance imaging. The common area of lesion overlap was small, being confined to the dorsal aspect of the inferior frontal gyrus (Brodmann's area 44) and the immediate underlying white matter. This cortical region is part of the homologue of Broca's area in the right hemisphere and is considered to be part of human premotor cortex. The association of neglect with injury to this area suggests it may play an important role in directing attention in visual space.

Anosognosia for hemiplegia, neglect dyslexia, and drawing neglect: clinical findings and theoretical considerations

In this paper different models of anosognosia are confronted and data concerning denial behaviors are presented that were collected on a selected population of right brain-damaged patients affected by motor and neglect disorders. Anosognosia for motor impairment and anosognosia for cognitive impairments were found to be dissociated, as well as anosognosia for the upper and lower limb motor impairments. These findings are then discussed in an attempt to choose the more suitable theoretical framework for interpreting the various disorders related to denial of illness.

Subtraction bugs in an acalculic patient

We report a patient, MT, who presented a specific, though not isolated, deficit in written calculation. Despite a preserved knowledge of simple arithmetic - single-digit addition and subtraction - he failed systematically in multi-digit subtraction. The nature of errors was consistent across problems and reflected the application of a disturbed underlying algorithm. Moreover, the pattern of error observed mimies a very common finding in developmental studies on arithmetical procedure acquisition (Fuson, 1990, 1992, Young and O'Shea, 1981; VanLehn, 1986, 1990). The data suggest that, within calculation skills, syntax may exist as a system of stable, but inappropriate, rules which are independent of any underlying conceptual knowledge.

Perceptual and premotor components of unilateral auditory neglect

Recent investigations have distinguished between ophthalmokinetic and melokinetic factors of unilateral neglect. The aim of our study was to investigate the possible dissociation between melokinetic (premotor) and perceptual factors, avoiding any overt oculokinetic components. We asked four blindfolded left neglect patients to set a dichotic sound in central position, by moving a handle controlling the difference of intensity between the sounds delivered to the left and to the right ears. Two conflicting conditions were used. In the congruent condition, the sound moved in the same direction as the hand movement; in the noncongruent condition, it moved in the opposite direction. One patient performed as if suffering from melokinetic neglect, and another as if suffering from perceptual neglect. The behavior of the other two subjects did not lend itself to a clearcut interpretation.

False recognition and the right frontal lobe: a case study

We described a patient, BG, who exhibited a striking pattern of false recognition after an infarction of the right frontal lobe. Seven experiments document the existence of the phenomenon, explore its characteristics, and demonstrate how it can be eliminated. BG showed pathologically high false alarm rates when stimuli were visual words (experiments 1 and 4), auditory words (experiment 2), environmental sounds (experiment 3), pseudowords (experiment 5), and pictures (experiment 7). His false alarms were not merely attributable to the semantic or physical similarity of studied and non-studied items (experiments 4 and 5). However, BG's false recognitions were virtually eliminated by presenting him with categorized stimuli and testing him with new stimuli from non-studied categories (experiments 6 and 7). The results suggest that BG's false alarms may be attributable to an over-reliance on memory for general characteristics of the study episode, along with impaired memory for specific items. The damaged right frontal lobe mechanisms may normally support the monitoring and/or retrieval processes that are necessary for item-specific recognition.

[A study of utilization and imitation behavior in cases with striatocapsular infarction]

Utilization behavior (UB) and imitation behavior (IB) were first described by Lhermitte (1983; 1986) for neurobehavioral disorders due to the frontal lobe damage. Recently, the similar symptoms were also observed in several reports of subcortical lesion cases without any lesion of the frontal lobe. We studied 16 consecutive patients with unilateral striatocapsular infarction (SCI), and found 7 patients (44%) presenting UB and/or IB. Characteristics of patients with UB and/or IB revealed the following factors: older age, higher frequency of right-sided lesion, absence of severe aphasia or apraxia, higher frequency of unilateral spatial neglect and/ or psychic change, and no evidence of significant large cerebral artery lesion on angiography. In most of SCI cases, whether IB and/or UB was present or not, the single-photon emission CT demonstrated decreased perfusion in the ipsilateral frontotemporal areas, and the result of neuropsychological assessment was compatible with frontal lobe dysfunction. UB and IB observed in our patients are not only considered to have resulted from secondary impairment of frontal lobe, but also regarded as one of the right hemispheric syndromes associated with such background factors as aging, neglect and general inattention.

Intracisternal basic fibroblast growth factor (bFGF) enhances behavioral recovery following focal cerebral infarction in the rat

Basic fibroblast growth factor (bFGF) is a potent neurotrophic agent that promotes neuronal survival and outgrowth. Previous studies have shown that bFGF, administered intraventricularly or intravenously before or within hours after ischemia, reduces infarct size and neurological deficits in models of focal cerebral ischemia in rats. In the current study, we tested the hypothesis that bFGF, administered at later time points after ischemia, might improve behavioral recovery without affecting infarct size. Mature Sprague-Dawley rats received bFGF (1 microgram/injection) or vehicle by biweekly intracisternal injection for 4 weeks, starting at 1 day following permanent proximal middle cerebral artery (MCA) occlusion. Animals were examined every other day using four different behavioral tests to assess sensorimotor and reflex function. At 4 weeks after ischemia, there was no difference in infarct volume between bFGF- and vehicle-treated animals. There was, however, an enhancement in the rate and degree of behavioral recovery among bFGF-treated animals, as measured by all four tests. There were no apparent side effects of bFGF treatment, except that bFGF-treated animals tended to recover body weight more slowly than did vehicle-treated animals following stroke. The mechanisms of enhancement of behavioral recovery by bFGF require further study, but may include protection against retrograde neuronal death and/or stimulation of neuronal sprouting.

Do silent brain infarctions predict the development of dementia after first ischemic stroke?

BACKGROUND AND PURPOSE

Silent brain infarctions (SBI) are common findings in advanced age, but their relationship to dementia is still uncertain. The present study was designed to evaluate whether SBI predict the development of dementia after first clinical ischemic stroke.

METHODS

We blindly studied admission CT scans of 175 consecutive nondemented patients presenting with ischemic stroke that clinically was their first stroke episode. SBI were defined as CT evidence of infarcts not compatible with the acute event. The patients were subsequently followed for their mental state for 5 years. Survival analysis, wherein onset of dementia was the end point, was performed on the total sample population and conducted separately on those with and without SBI at admission.

RESULTS

Dementia developed in 56 patients (32%), including 22 of the 63 (35%) with SBI and 34 of the 112 (30%) without SBI. Thus, dementia was not related to SBI.

CONCLUSIONS

Our data indicate that SBI do not predict the development of dementia after stroke.

Sensorimotor impairments in Wistar Kyoto rats with cerebral infarction, induced by unilateral occlusion of the middle cerebral artery: recovery of function

Wistar Kyoto (WKY) rats with cerebral infarction induced by permanent unilateral occlusion of the middle cerebral artery (MCA) and sham-operated rats were tested in a series of simple behavioral test 2, 16 and 37 days after surgery. In addition, the motility of the animals was measured over a period of 62 h, after the third test series. A subset of the tests appeared to be suitable to assess the effects of cerebral infarction, namely, grasping reflex of contralateral hindpaw, circling behavior, forelimb flexion, hindlimb flexion, and latency to fall off a square bridge. Except for the impaired grasping reflex of the contralateral hindpaw, there was spontaneous complete recovery of function by the third test session, 37 days after surgery. Some of the other tests might not have been sensitive enough to detect the effects of the unilateral MCA-occlusion (MCA-O) on behavior. Moreover, the WKY rats were very inactive in some of the tests, so that reliable scoring of the effects was not always possible. A rat strain other than the WKY strain might be more suitable to study the behavioral consequences of MCA-O.

A magnetic resonance imaging study of white matter lesions in depression and Alzheimer's disease

BACKGROUND

White matter changes, as revealed by magnetic resonance imaging (MRI), may occur in depression and Alzheimer's disease.

METHOD

T2-weighted MRI scans were performed in 39 control subjects, 61 subjects with NINCDS/ADRDA Alzheimer's disease and 60 subjects with DSM-III-R major depression. Deep white matter lesions (DWML) and periventricular lesions (PVL) were rated on a standard 0-3 scale by two radiologists blind to clinical diagnosis.

RESULTS

After controlling for differences in vascular risk factors and current blood pressure, DWML were significantly more common in depressed subjects and PVL in Alzheimer's disease subjects compared to controls. DWML were most common in those presenting in late life with their first ever depression and 50% of such subjects had severe (grade 3) DWML.

CONCLUSION

An association between DWML and depression and PVL and Alzheimer's disease is supported. The increase with DWML that occurs with ageing may predispose some elderly subjects to depression.

[The man with 6 arms. An analysis of supernumerary phantom limbs after right hemisphere stroke]

Consequently an infarct in the territory of the right middle cerebral artery, a 77-year old man had a complete left sensory motor hemiplegia, with left neglect. For several weeks, he described the existence of one and more supernumerary phantom limbs. The patient's adamant and delusional conviction of their reality caused him considerable distress. Without being anosognosic he was not completely aware of his disorder, and had slight difficulties in judging what was plausible. The mechanisms underlying this delusion concerning specific parts of the body probably involve multifactorial disorders: first, a sensory deafferentation source of a distorsion of the perceived body schema; second, a resulting discrepancy between the perception of the body schema and its innate representation; third abnormalities of self-awareness and of self-judgement, leading the patient to argue forcellully in favor of incongruous rationalizations.

[Interhemispheric disconnection syndrome caused by partial infarction of the corpus callosum: neuropsychological study and MRI]

A partial syndrome of hemisphere disconnection was observed in a 63 year-old woman, following an anterior and middle corpus callosum infarct on MRI. Notably, we found left ideomotor apraxia, diagonistic apraxia, left-year extinction on dichotic listening, but no left-hand anomia nor left visual field anomia. A left tactile extinction in dichaptic condition is interpreted as resultant of a dysregulation of the attentional balance between the two hemispheres. This detailed neuropsychological study permits a correlation between the callosal syndrome and the lesion. We suggest that an occlusion of the anterior callosal artery could explain this limited ischemia.

Grasping without form discrimination in a hemianopic field

Although patients with blindsight are usually unable to discriminate forms, recent neuropsychological data have suggested that they could still use some form attributes in object-oriented actions. One patient with a complete right hemianopia due to a medial occipital lesion has been tested for his capacities to process orientation and size of visual objects. He was presented with either a slot of variable orientation or with rectangular objects of the same surface but variable length. His performance was studied in three types of tasks: motor, in which he had to insert a card in the slot or to grasp the rectangle between thumb and indexfinger; verbal, in which forced-choice verbal guesses were required; and matching, which required matching orientation or size with wrist or fingers. Although responses were at chance level in the two latter conditions, motor responses were systematically influenced by both orientation and size of the stimulus. These data provide further evidence for two dissociable modes of visual information processing dealing respectively with 'what"' the object is vs 'how' to grasp it. They also indicate that the neural pathway controlling visuomotor transformation in humans is much less dependent on V1 input than the pathway involved in visual discrimination and identification.