Contributions of stimulus valence and arousal to visual activation during emotional perception.

Neuroimaging experiments have revealed that the visual cortex is involved in the processing of affective stimuli: seeing emotional pictures leads to greater activation than seeing neutral ones. It is unclear, however, whether such differential activation is due to stimulus valence or whether the results are confounded by arousal level. In order to investigate the contributions of valence and arousal to visual activation, we created a new category of "interesting" stimuli designed to have high arousal, but neutral valence, and employed standard neutral, unpleasant, and pleasant picture categories. Arousal ratings for pleasant and neutral pictures were equivalent, as were valence ratings for interesting and neutral pictures. Differential activation for conditions matched for arousal (pleasant vs neutral) as well as matched for valence (interesting vs neutral) indicated that both stimulus valence and arousal contributed to visual activation.

Executive amnesia in a patient with pre-frontal damage due to a gunshot wound.

This paper reports the case of a young patient with extensive pre-frontal damage in whom we tested the hypothesis that intensive training improves executive performance as assessed by the Wisconsin Card Sorting Test (WCST). As long as her declarative memory, complex perceptual abilities and global cognitive status were spared, we surmised that any deficit in executive learning would have occurred in relative isolation. We showed that her abnormal performance on the WCST, both on the standard as well as on the post-instruction condition, was due to an impairment of shifting attention across perceptual dimensions (extra-dimensional). In contrast, her ability to shift attention within perceptual categories (intra-dimensional) was spared, as were her declarative memory, object and visuospatial perception, oral language comprehension and praxis (ideomotor, tool use and constructional). This case supports the hypothesis that executive amnesia is a type of amnesic disorder distinct from the classic amnesic syndrome due to mamillo-temporomedial damage. As such, it is probably closely related to procedural learning and may depend on the same fronto-subcortical loops that mediate the actual execution of behaviour.

Functional MRI correlates of real and imagined tool-use pantomimes.

OBJECTIVE: To study the pattern of cerebral activation related to the performance of tool-use pantomimes with functional MRI (fMRI) using a task-subtraction design. BACKGROUND: Tool use comprises a particular category of transitive actions. Inability to pantomime the use of tools has been classically associated with retrorolandic dominant hemisphere damage. However, where in the left hemisphere these transitive representations are generated is unclear. METHODS: Echoplanar images were acquired in eight alternating task and control periods. Sixteen right-handed normal adults pantomimed the use of common tools and utensils with each hand. The control condition consisted of a sequence of nonsymbolic complex movements of forearm, hand, and fingers at a self-paced rate. Eight individuals also imagined the execution of the real task and control actions. A repeated measures ANOVA compared activations in five regions of interest in each hemisphere. RESULTS: Regardless of which hand was used, the left hemisphere was more active than the right in both real (p < 0.02) and imagined (p < 0.04) tasks. Activations clustered in the left intraparietal cortex and posterior dorsolateral frontal cortex. CONCLUSIONS: Pantomiming the use of tools is associated with activation of the left intraparietal cortex and dorsolateral frontal cortex. The left intraparietal cortex may store the representations of tool-use formulae, whereas the dorsolateral frontal cortex activation may reflect the switching between innervatory motor programs.

Activation of left intraparietal sulcus using a fMRI conceptual praxis paradigm.

The present paper reports the results of a fMRI subtraction study of the pattern of cortical activation induced by an ideational praxis paradigm in six normal right-handed subjects. The control task consisted of a sequence of complex meaningless hand movements. A complete study was done for each hand in each subject. The left intraparietal sulcus was the only structure activated in all subjects regardless of the hand used in the task. These findings, albeit preliminary, suggest that the organization of actions involving the mediation of tools and utensils are strongly lateralized to the left hemisphere and that damage to the dominant intraparietal sulcus may be critical for the development of the clinical syndrome of conceptual apraxia.

[Virtual dystonia due to posterior ventrolateral thalamic infarct: case report]. / Distonia virtual por infarto talâmico posterolateral ventral.

Behaviors, actions and movements may take place as purely mental events, as in the obsessions of obsessive-compulsive disorder, phantom limbs or sensory tics. In the present paper we report on the case of a 43-year-old diabetic hypertensive man who developed an incomplete form of the Dejerine-Roussy syndrome. Whenever he lay down or withdrew the leg from the ground, he experienced the illusion that the left intermediate toes painfully twisted and mounted each other. Conversely, as he stood up or firm pressure was artificially exerted against the sole, there was a dramatic relief from the "cramp" whose illusory character could he be certain of only by looking down at the foot. By passively moving his toes into the referred position we realized that the experienced deformity conformed to the pattern of a fixed dystonia not outwardly expressed through the motor system. There was severe proprioceptive loss in the same toes that harbored the cramp. MRI showed the appropriate lesion in the posteroventrolateral thalamus (VPL) and wallerian degeneration of thalamo-cortical projections. SPECT showed hypoperfusion of the overlying ipsilateral parietal cortex as well as of the basal nuclei bilaterally, besides the expected image of thalamic exclusion. We hypothesize that the infarct disconnected the somatic sensory cortex (S-1) from critical proprioceptive input with relative sparing of superficial sensibility. Lifting the foot deprived S-1 of tonic inputs conveyed by undamaged contact-pressure pathways, a functional effect promptly reversed by placing the foot back against the ground. The case illustrates how a capricious deafferentation of S-1 by a discrete VPL thalamic infarct might facilitate the emergence of autochthonous activity.

[Coma and transtentorial herniation syndrome due to acute non-expansive hemispheric lesion]. / Coma e síndrome de herniação transtentorial consequentes a lesão hemisférica não expansiva aguda.

An 81-year-old woman developed left hemiplegia and coma due to a right hemisphere infarct and died 6 days later. When first seen in coma she had the classical signs of descending central herniation in the diencephalic stage. The CT scan of the third day showed a large hypodense area occupying the superficial and deep territories of the middle and anterior cerebral arteries on the left as well as a frontal cortico-subcortical hypodense area indicative of an older infarct on the opposite hemisphere. No mass effects were apparent. She followed a downhill course with signs of brainstem deterioration. A second CT scan a few hours before death revealed the expected pattern of brain shift and herniations. This case adds to the available evidence showing that the clinical signs of encroachment of supratentorial structures upon the basal forebrain can be reproduced by an acute mono-hemispheral lesion without visible mass effects. It indicates, further, that the role of intracranial displacements in the genesis and short-term prognosis of coma remains an unsettled matter. In at least a few number of cases, diaschisis might play a major role.

[Spontaneous tegmental-mesencephalic hematoma: neurobehavioral aspects of the rostral third of the human brainstem]. / Hematoma tegmento-mesencefálico espontâneo: aspectos neurocomportamentais do terço rostral do tronco encefálico humano.

The tegmentum of the midbrain is a complex area traversed by a number of anatomical and functional systems, including local circuits, ascending activating systems and descending fibers from the cerebral hemispheres. In the present paper we report on the case of a 67-year-old man who suffered a spontaneous central tegmental hemorrhage and was initially supposed to be in coma due to bilateral ptosis and lack of speech and initiative. By the second hospital week, however, he was shown to be able to respond to verbal commands, sit, stand and walk. He died in sepsis one month later. This case shows that the clinical diagnosis of coma may be misleading in certain patients in whom wakefulness is preserved, though concealed from a casual bedside examination due to abulia and ophthalmoplegia.

[Pathological crying and unilateral pontine infarction]. / Incontinência do choro e infarto protuberancial unilateral.

A 64-year-old man presented with pathologic crying and right hemiplegia due to a unilateral pontine infarct from probable branch disease of the basilar artery. The circumscribed nature of the lesion was supported by MRI and short-latency evoked potentials. The weeping spells ceased after a few days of imipramine in low doses. Pathologic laughing and crying can be viewed as a limbic-motor disconnection syndrome, in which the faciovocal motor system is released from forebrain afferents carrying information of emotional content. The inclusion of pathologic laughing and crying in the syndrome pseudobulbar palsy is inaccurate and misleading, since each is related to distinct functional and anatomic systems intrinsic to the human brainstem.