Biomedical subjects

A Peru

Publications and source records attributed to A Peru.

15 recordsLinked to original sources

PubMed2006

Suggestive evidence for an involvement of the right hemisphere in the recovery from childhood aphasia: a 3-year follow-up case study.

We describe the case of an 11-year-old, previously healthy, pre-puberal, right-handed girl with acquired aphasia following an extensive cerebral hemorrhage into a left hemisphere brain tumor. A 3-year follow-up evaluation of the girl's communicative performance showed an incomplete recovery of linguistic abilities with a good recovery of comprehensive components, but persisting severe impairment in expressive language. At the end of the follow-up period, with the aim of assessing the lateralization of some linguistic abilities, we carried out an experimental investigation using tachistoscopic reading and object naming tests along with a dichotic listening test. All these tests showed a clear left field/left ear-right hemisphere advantage. We discuss both clinical and experimental results with regard to implications for the linguistic abilities of the right hemisphere in late versus early childhood and its interaction with aetiology in the recovery from acquired childhood aphasia.

Aphasia↗

PubMed2006

Stroop effects from 3 to 10 years: the critical role of reading acquisition.

We studied 241 nursery and primary school 3- to 10-year old children with a discrete-trial version of the Stroop Test, including both a Color-Naming and (for the 6- to 10-year olds only) a Word-Reading task. The classic Stroop effect was present across all the ages, with an inverted U-shaped pattern: increasing from 3- to 7-year olds, then decreasing. Preschool children who were able to read showed a Stroop effect larger than same-age, unable to read children. The reverse Stroop effect was present across all the studied ages but the 6-year-olds, who instead displayed some facilitation in reading congruent vs. black words. Since the acquisition of reading skills turned out to be crucial for the Stroop effects, the present research may be useful to study developmental reading impairments by providing normative data.

Aging↗

PubMed2000

Right-sided neglect following a left subcortical lesion.

Unilateral spatial neglect is, in humans, typically consequent to lesions of the right hemisphere and pertains to the left hemispace. Although neglect is maximally frequent after right cortical lesions, it may also ensue from lesions confined to right subcortical structures. By contrast, hemispatial neglect consequent to left hemispheric lesions occurs less frequently. Reports of neglect following lesions to left subcortical structures are even more rare and largely anecdotal. Here we report on a right-handed man who had two successive left-sided brain lesions at an interval of 10 years from one another. The first lesion, centered upon the occipital lobe, induced a contralateral hemianopia, but no signs of hemispatial neglect; by contrast, the second lesion, a capsulo-thalamic hemorrhage, did induce a florid and persistent right-sided neglect. This finding would suggest that left subcortical structures may be important nodes in the network subserving spatial representations.

Attention↗

PubMed1999

A new case of representational neglect.

We describe a right-handed female patient who, after a right-hemisphere stroke, showed a florid representational neglect, but no evidence of perceptual neglect. This finding provides further support for the argument that orienting attention to the representational and perceptual spatial domains is subserved by independent neural mechanisms.

Attention↗

PubMed1999

Frames of reference for mapping tactile stimuli in brain-damaged patients.

Twelve normal controls, twelve left-brain-damaged patients, and thirty-six right-brain-damaged patients with or without tactile extinction or tactile neglect were asked to report light touches delivered to the left or the right hand or simultaneously to both hands. The hands could be in anatomic position or one hand could cross over the other. Moreover, the two hands could be in the left or the right hemispace or across the corporeal midline. Controls and nontactile-extinction groups performed better when the hands were in anatomical than in crossed position. By contrast, patients with tactile extinction detected contralesional stimuli with higher accuracy in crossed than in anatomical position. This result suggests that, in these patients, impairments in detecting contralesional stimuli can be due not only to sensory but also to spatial factors contingent upon the position of the hands. There was no interaction between the effect of crossing the hands and the hemispace where the crossing took place. This suggests that coding the position of a hand as left or right does not necessarily occur in relation to the bodily midline, but it may arise from the computation of the position of the other hand.

Brain Damage, Chronic↗

PubMed1999

Possible recoding of visual space in covert orienting tasks.

Reaction time to lateralized light targets is longer if targets are preceded by light stimuli in the same visual hemifield compared to when they are preceded by light stimuli in the opposite visual hemifield. The effect is probably caused by interactions between implicit oculomotor tendencies and covert shifts of attention. We show here that a similar, but much smaller, ipsilateral RT inhibition can be observed when all stimuli are presented in a display completely lateralized to one hemifield, where ipsilateral and contralateral are defined with respect to the midpoint of the display. The persistence of ipsilateral inhibition with unilateral stimulus displays can be accounted for by a recoding of visual space predicated on the centering of covert attention on the display midpoint rather than on the fixation point. The recoding seems to affect the control of covert attention and perhaps oculomotor control as well.

Adult↗

PubMed1998

Neurological recovery after systemic thrombolytic therapy in a chronic stroke case.

We describe a patient who in 1983 suffered a stroke which resulted in severe hemiplegia and somatosensory loss. His neurological condition remained stable until January 1996, when, because of a myocardial infarction, the patient underwent systemic thrombolytic therapy which led to a remarkable improvement of both motor and somatosensory functions. This finding suggests the existence of 'idling neurons' which remain viable for a long time after stroke, and opens a fascinating window on the therapeutic potential of thrombolytic therapy in chronic stroke patients.

Aged↗

PubMed1998

Tactile salience influences extinction.

We delivered unilateral (left or right) or bilateral tactile stimuli to hands or feet of right-brain-damaged patients, six with tactile extinction and two without. Stimuli were simple touches or sliding stimuli directed proximo-distally (e.g., toward the fingers) or disto-proximally (e.g., toward the forearm). Patients were asked to report number (one or two), type (touch or slide), and direction (proximo-distally or disto-proximally) of the experimental stimuli. Nonextinction patients performed perfectly. Extinction patients, although accurate in reporting single stimuli, omitted left stimuli under double-stimuli conditions. However, the number of left stimuli detected consciously was related to an imbalance of the salience between left and right stimuli. Moreover, in three patients the extinguished, left-sided stimulus, even when inaccessible to consciousness, influenced implicitly the report of the features of the right stimulus. Thus, the relationships between left and right stimuli can modulate both overtly and covertly the performance of extinction patients.

Adolescent↗

PubMed1997

Thalamic amnesia following venous infarction: evidence from a single case study.

The present paper describes the case of a right-handed Italian-English bilingual male patient suffering from amnesia following a bilateral thalamic lesion due to venous infarction. Within a few months from the onset, the lesion gradually shrank and was finally confined to the left thalamus only, in particular to the antero-medial portion and the pulvinar. The mammillary bodies and the cortical areas of both hemispheres were spared. After the regression of a series of generalized cognitive deficits implying slow psychic activity confusion, and spatial and temporal disorientation, the patient presented a persistent amnesic syndrome with mild language disorders, both in Italian and in English. Major disorders of memory included a dissociation between verbal memory, which was severely impaired, and spatial memory, which was largely preserved.

Brain Ischemia↗

PubMed1997

Right personal neglect following a left hemisphere stroke. A case report.

Neglect phenomena may occur in both extrapersonal and personal space. Whereas extrapersonal neglect has been found associated with both right- and left-sided brain lesions, no case of right personal neglect following a left-sided lesion has been so far reported. We describe a right-handed female patient who, after two left-hemisphere strokes, exhibited a florid personal neglect, but no extrapersonal neglect, anosognosia or somatoparaphrenia. The symptom persisted for a few weeks and then gradually disappeared. At least in the early phase of disease, a personal neglect can also be observed in patients with left brain damage.

Aneurysm, Ruptured↗

PubMed1997

Influence of perceptual and semantic conflicts between the two halves of chimeric stimuli on the expression of visuo-spatial neglect.

We investigated how perceptual and semantic relationships between the left and right half of chimeric stimuli influence overt and covert visual processing by asking eight right brain damaged (RBD) patients with hemispatial neglect to identify complete, half-, and chimeric drawings. Chimeric stimuli belonged in one of four categories defined according to the perceptual and semantic relatedness between the two compounding hemi-figures. Thus, the hemi-figures could be related both perceptually and semantically, only perceptually, only semantically, or neither perceptually nor semantically. Although patients often appeared to base their report on the right part of the chimerics, the number of errors was minimal when conflicts between the two hemi-figures were maximal. Moreover, perceptual conflicts, which mainly affect the perception of the shape, appeared to influence the performance more than semantic conflicts. Since the analysis of shape incongruency is probably accomplished at early levels of information processing, the result suggests that preattentive analysis is largely spared in the experimental patients and that, in our task, bottom-up factors more than top-down factors modulate the expression of left neglect.

Aged↗

PubMed1996

Overt and covert processing of left-side information in unilateral neglect investigated with chimeric drawings.

Overt and covert processing of contralesional information was investigated in 6 right-brain-damaged (RBD) patients with or without left hemispatial neglect by using three bedside tests that require the analysis of whole, half, and chimeric drawings. In the first task, patients named these stimuli. In the second task, patients designated as "same" or "different" drawings in a pair where one drawing was always whole and the other could be whole, half, or chimeric. In the third task, patients pointed to the more veridical, complete drawing that was presented with one half drawing, and two chimeric drawings. Although patients with no neglect performed without error in all conditions, patients with severe neglect based their performance on the analysis of the right side of the stimuli. In patients with mild neglect, not only did performance rely upon the right side of stimuli but it was also modulated by left-side information acquired either overtly or unconsciously.

Adult↗

PubMed1995

Oculomotor activity and visual spatial attention.

Subjects made a horizontal or vertical saccade in response to a non-lateralized auditory stimulus. Simple manual reaction time (RT) for the detection of light targets at extrafoveal locations was modulated by the intention to make the saccade insofar as RT to targets presented at the saccadic goal location or in the hemifield containing that location was faster than RT to targets presented at the opposite, mirror-symmetric location. This RT difference was maximal prior to the beginning of the saccade and vanished after saccade termination, indicating that the effect was caused by the neural activity leading to the saccade rather than to the eye movement or the eye position per se. The results have implications for the understanding of the relations between visual spatial attention and oculomotor control, especially with regard to inhibitory phenomena arising from the non-correspondence between the line of sight and the focus of attention.

Acoustic Stimulation↗

PubMed1994

Do peripheral non-informative cues induce early facilitation of target detection?

It has been reported that simple reaction time (RT) to a peripheral visual target is faster if the target is presented within about 200 msec from the onset of a non-informative cue flashed at the same location, as compared with RT to a target presented at an uncued location. This period of facilitation is followed by a period of inhibition during which RT is longer if cue and target are shown at the same location or at different locations within the same hemifield, as opposed to contralateral cues and targets. Early facilitation has been explained by an automatic covert orienting towards the cue, while the following inhibition has been regarded as a consequence of such covert orienting. In a series of four experiments, we have investigated the dependency of these effects on the temporal and spatial relationships between cue and target. Normal, right-handed subjects responded to a target displayed for 16 msec simultaneously with, or following at stimulus-onset asynchronies (SOAs) of 60, 130, 300 or 900 msec, the onset of a non-informative cue. Both cues and targets could appear at random in one of four locations (Expts 1-3) or in one of two locations (Expt 4) disposed symmetrically across the fixation point along the horizontal meridian. Duration of the cue varied between experiments. In Expt 1 it was 16 msec. In Expt 2 the cue remained on view throughout the period of the SOA and terminated 300 msec after target onset. In the remaining two experiments cue duration was 130 msec. In the first experiment, at all cue-target SOAs RTs to target flashed either at the same location or in the same hemifield as the cue were significantly slower than RTs to contralateral cue-target combinations (RT inhibition). In the other experiments, there was no RT inhibition with targets in cued locations if the cue remained on during target presentation and outlasted target offset. Since at no SOA was RT to targets in cued locations shorter than RT to targets contralateral to cues, there was no direct evidence for facilitation. However, the facilitatory influence of these cues could be inferred from the fact that they countered and masked inhibition. RT to uncued targets ipsilateral to cues was consistently inhibited in all experimental conditions. These results show that at each cue-target SOA the consequences of a peripheral non-informative cue depend on whether or not the cue remains visible during target processing.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1993

European isolation and confinement study. Attention during isolation and confinement.

The aim of this study was to examine the effect of isolation and confinement on selective attention. The experiments were carried out on six specially selected male subjects. The subjects were isolated in a hyperbaric chamber complex at a low overpressure for a period of 28 days. Distribution of attention between two tasks, visual search and orientation of attention to symbolic and automatic cues were studied. The results showed that 4 weeks of isolation and confinement do not significantly modify visual search and the capacity to execute two tasks simultaneously. In the double task experiment there was a clear improvement of performance during isolation and the post-isolation period. However, the development of a remarkably large difference between subjects was found. Orientation of attention to automatic cues gave results comparable to those obtained under normal conditions. Valid trials (stimulus flash and cue in same box) were faster than both neutral (cue in all boxes) and invalid trials (stimulus flash and cue in different boxes). Orientation of attention to symbolic cues also produced this effect. However, the "meridian effect" (increased reaction time when the stimulus is in the opposite half of the visual field as cue), which is constantly observed under normal conditions, was absent during isolation. The absence of the meridian effect is interpreted as a change in the subject's strategy to allocate attention. It is proposed that the absence of the meridian effect indicates an initial deficit of attentional capacities during isolation and confinement.

Adult↗