Anosognosia and visuoverbal confabulation.

OBJECTIVE: To examine the relationship between verbal confabulation and anosognosia for hemiplegia (AHP). DESIGN: We compared patients with right hemisphere lesions and AHP with a control group with right hemisphere lesions without anosognosia. Patients attempted visual identifications of objects exposed to the left hemifield with brief (condition 1) or prolonged (condition 2) presentations. Responses were recorded as correct, incorrect, or admission of failure to perceive. SETTING: Inpatients at Beth Israel Medical Center, New York, NY. PATIENTS: A consecutive sample of nine patients with right hemisphere infarcts who demonstrated left hemiparesis, extrapersonal neglect, and left-sided visual field defects. MAIN OUTCOME MEASURES: Rates of correct, incorrect, and admission of failure to perceive responses. RESULTS: Patients with AHP had higher error rates (confabulations) and lower admission of failure to perceive rates than nonanosognosic patients in condition 1. Patients with AHP continued to have higher error rates in condition 2. Nonanosognosic patients had higher correct rates in condition 2 than condition 1. Groups did not differ in degree of neglect, lesion size or location, atrophy, sensory loss, or disorientation. CONCLUSION: Verbal confabulation is an important determinant in anosognosia.

Two alien hand syndromes.

Review of the clinical characteristics and neuroanatomy of 20 reported cases of alien hand syndrome (AHS) and a patient of our own confirm that AHS is actually two distinct syndromes. Frontal AHS occurs in the dominant hand; is associated with reflexive grasping, groping, and compulsive manipulation of tools; and results from damage to the supplementary motor area, anterior cingulate gyrus, and medial prefrontal cortex of the dominant hemisphere and anterior corpus callosum. Callosal AHS is characterized primarily by intermanual conflict and requires only an anterior callosal lesion. the occurrence of frontal AHS in the dominant limb can be explained by an increased tendency for dominant limb exploratory reflexes coupled with release from an asymmetrically distributed, predominant nondominant-hemisphere inhibition. Callosal AHS is best explained by hemispheric disconnection manifested during behaviors requiring dominant-hemisphere control.

Verbal asomatognosia.

Verbal asomatognosia is a form of neglect in which a patient denies ownership of a limb contralateral to a brain lesion. To establish the neuroanatomic substrate of this syndrome, we analyzed the CTs of 12 right-hemisphere stroke patients with neglect and verbal asomatognosia and 4 patients with neglect but without asomatognosia. Of 16 cortical and subcortical brain regions analyzed, supramarginal gyrus and its subcortical connections within posterior corona radiata were most consistently involved in the asomatognosia cases. One or both of these regions were spared in all cases of neglect without asomatognosia. Our data confirm Nielsen's localization of asomatognosia to the right supramarginal gyrus and thalamoparietal peduncle. Converging lines of evidence from experiments in humans and monkeys suggest that damage to area PF may be necessary for the production of personal neglect of a limb.

Ipsilateral extinction in the hemineglect syndrome.

Data suggest right-hemisphere dominance for attention. Right-hemisphere lesions reduce attentional capacity that may manifest as neglect or extinction. Attention can be assessed with the Face-Hand Test where touch on the face may extinguish simultaneous touch on the hand. Extinction ipsilateral to unilateral lesions suggests abnormal attention to ipsilateral hemispace. We tested patients with left- and right-hemisphere lesions without neglect and right-hemisphere lesions with neglect with stimuli applied exclusively ipsilateral to lesions. In experiment 1, stimuli were applied in face-hand combinations. In experiment 2, the Face-Hand Test was ranked from 0 (no extinction) to 7 (marked extinction) using progressively greater stimulation. In both experiments, right-hemisphere patients with neglect made significantly more errors than left-hemisphere patients without neglect. These data support models of bidirectional right-hemisphere attentional dominance.