Biomedical subjects

C Umiltà

Publications and source records attributed to C Umiltà.

At least 37 records · Page 2Linked to original sources

PubMed1998

Deficits in the control of the attentional focus in chronic schizophrenics.

The ability to control the size of the attentional focus and thus to modulate processing efficiency was investigated using simple reaction times in central vision in 17 chronic schizophrenic patients and 17 normal control subjects. The size of the attentional focus was manipulated by varying the size of a central box (i.e., a pre-cue), where the imperative stimulus appeared. In accordance with previous studies, in normal controls reaction time increased with box size. In contrast, in schizophrenic patients reaction time did not depend on box size. That is, schizophrenic patients did not show the inverse relation between size of the box and speed of processing, which is observed in normal controls. These results suggest that a deficit in controlling the size of the attentional focus is a basic impairment in chronic schizophrenia. It was also found that schizophrenics are more susceptible than controls to paracontrast.

Adult↗

PubMed1998

Preferential orienting to faces in newborns: a temporal-nasal asymmetry.

It has been proposed that newborns' preferential orienting to faces is primarily controlled by a subcortical mechanism. As an index of subcortical, extrageniculate mediation, the asymmetry between the temporal and nasal hemifields was exploited. In Experiment 1, under monocular viewing conditions, newborns were presented with a pattern that had 3 blobs in the appropriate locations for the eyes and the mouth or a pattern that had an inverted position of the blobs. Results showed that newborns preferentially oriented to the facelike pattern only when it was presented in the temporal hemifield. In Experiment 2, both patterns had the blobs in the inverted position. For one pattern the blobs were black, and for the other they were striped. Newborns preferentially oriented to the striped blobs in either hemifield. The results support the hypothesis that in newborns, preference for facelike patterns reflects the activity of a subcortical mechanism.

Analysis of Variance↗

PubMed1998

Symbolic distance between numerosity and identity modulates Stroop interference.

Thirty undergraduates participated in an experiment investigating the effect of the arithmetic difference between stimulus identity and stimulus numerosity in a numerical version of the Stroop task. It was found that digits symbolically close to the enumeration response reliably produced larger interference than digits that were farther from the enumeration response. This semantic distance effect was found with different numerosities (1-9) and different enumeration processes (counting and subitizing), and it increased as a function of numerosity in the subitizing range. These findings suggest that digit identity autonomously activates a magnitude representation organized as a compressed number line.

Adult↗

PubMed1997

Lexical and semantic processing in the absence of word reading: evidence from neglect dyslexia.

Nine patients with left-sided neglect and nine matched control patients performed three tasks on horizontal (either normal or mirror-reversed) letter strings. The tasks were: reading aloud, making a lexical decision (word vs non-word), and making a semantic decision (living vs non-living item). Relative to controls, neglect patients performed very poorly in the reading task, whereas they performed nearly normally in the lexical and semantic tasks. This was considered to be a dissociation between direct tasks, rather than a dissociation between explicit and implicit knowledge. The explanation offered for the dissociation is in terms of both a dual-route model for reading aloud and a degraded representation of the letter string.

Aged↗

PubMed1997

The Simon effect occurs relative to the direction of an attention shift.

We investigated whether the Simon effect depends on the orienting of attention. In Experiment 1, participants were required to execute left-right discriminative responses to 2 patterns that were presented to the left or right of fixation. The 2 patterns were similar, and the discrimination was difficult. A letter at fixation signaled whether the current trial was a catch trial. The results showed a reversal of the Simon effect. That is, spatially noncorresponding responses were faster than spatially corresponding responses. In Experiment 2, the discrimination of the relevant stimulus attribute was easy. In Experiment 3, the discrimination of the relevant stimulus attribute was difficult, but the stimulus exposure time was long. In either experiment, the regular Simon effect was reinstated. In Experiment 4, the letter that signaled a catch trial appeared to the left or right of the imperative stimulus. The Simon effect occurred relative to the position of the letter.

Adult↗

PubMed1996

Executive functioning following mild closed head injury.

This study was aimed to identify impaired attentional components in mild CHI patients. The CHI features taken into account were age (< or = 30 vs. > 30 years), loss of consciousness (yes vs. no), and time after injury (few days vs. some months). The groups tested were composed of 26 patients and 26 controls (matched for age, sex and education). Experiment 1 used a dual-task paradigm (Umiltà et al., 1992), which taps executive functions. The double task-single task difference was greater for the CHI group, but only for patients older than 30 years and/or with consciousness loss. Two years after injury, some of these patients were retested: The results showed that this deficit was still present. Experiment 2 studied visual selective attention using the Navon (1977) paradigm. In this case, there were no differences between patients and controls. The results are discussed with reference to the anterior/posterior attention systems.

Adolescent↗

PubMed1996

Face preference at birth.

Four experiments are reported that were aimed at elucidating some of the controversial issues concerning the preference for facelike patterns in newborns. The experiments were devised to contrast the original and the revised versions of the sensory hypothesis and the structural hypothesis as accounts of face preference in newborns. Experiments 1A and 1B supported the structural hypothesis by showing a visual preference for the stimulus for which components were located in the correct arrangement for a human face. Experiment 2 supported the sensory hypothesis by showing a visual preference for stimuli that were designed to have the optimal spatial frequency components for the newborn visual system. Experiment 3 showed that babies directed attention to a facelike pattern also when it was presented simultaneously with a nonfacelike stimulus with optimal spatial frequency for the newborn visual system.

Attention↗

PubMed1995

A computational model of the Simon effect.

Even though stimulus location is task irrelevant, reaction times are faster when the location of the stimulus corresponds with the location of the response than when it does not. This phenomenon is called the Simon effect. Most accounts of the Simon effect are based on the assumption that it arises from a conflict between the spatial code of the stimulus and that of the response. In this paper a computational model of this hypothesis is presented. It provides a computationally explicit mechanism of the Simon effect. Consistent with human performance, the model provides reaction times that indicate both an advantage for the ipsilateral, corresponding response (i.e., facilitation) and a disadvantage of the contralateral, noncorresponding response (i.e., inhibition). In addition, the model accounts for the fact that the size for the effect depends on task difficulty.

Attention↗

PubMed1995

Unilateral neglect can be affected by stimuli in the neglected field.

Neglect patients' attention is usually pathologically captured by stimuli present on the side ipsilateral to the brain damage. In previous research it was shown that not only the mere presence but also the number of "relevant" stimuli on the right side influenced patient's performance. However, the influence of stimuli whose presence was completely irrelevant for the execution of the task was not previously studied. We asked neglect patients to bisect lines of 28 cm of length, which could be presented alone or with line-drawings of objects placed either only on the left, only on the right or bilaterally on the display. We found that the presence of irrelevant left-side stimuli improved the bisection performance in 3 out of 5 patients with respect to the baseline condition, in which, no stimuli were present on either side of the display. Right-side stimuli did not affect the performance, whereas bilateral stimuli tended to worsen the performance for those patients who presented the beneficial effect of left-side stimuli. These findings were discussed with reference to the hypotheses advanced to explain neglect.

Adult↗

PubMed1995

Domain-specific forms of neglect.

In this paper, it is assumed that domain specificity is one of the crucial criteria of modularity. It is also assumed that hemispatial neglect is basically a spatial attention deficit. Then, the literature that has shown, on the basis of either single or double dissociations, that neglect can be confined to very specific representational domains is reviewed. In particular, two recent studies are summarized that reported dissociations between perceptual and motor neglect and between visual and tactile neglect. It is suggested that disorders of spatial attention can affect just one spatial representational domain. This satisfies the domain specificity criterion of modularity and suggests that spatial attention mechanisms may be modular.

Attention↗

PubMed1994

Attention shifts produce spatial stimulus codes.

In the Simon task the spatial position of the stimulus, though task irrelevant, influences speed of response. We (Umiltà & Nicoletti, 1992) proposed that the orienting of attention to the imperative stimulus produces a Stroop-like interference. This paper reports the results of three experiments that provide empirical support for two predictions of this hypothesis. One is that the stimulus spatial code is formed with relation to the position to which attention is directed. The other prediction is that the Simon effect is obtained on condition that attention can orient to the stimulus.

Adult↗

PubMed1994

Hand-hemispace spatial compatibility, precueing, and stimulus-onset asynchrony.

The role of attention and the resolution of coding conflicts in hand-hemispace spatial-compatibility effects was examined in a precueing experiment in which visual and vibrotactile precues, with various stimulus-onset asynchronies (SOAs), were presented in blocked and random order. It was expected that precues at the shorter SOAs would fail to facilitate the shifting of attention, as they occur too close to the imperative stimulus to be informative. The task would therefore approximate one of choice reaction time (RT), resulting in a hand-hemispace spatial-compatibility effect. Conversely, the longer SOAs would provide the subject with sufficient time in which to shift attention fully, and would therefore result in a task more like that of simple reaction time (SRT). It was expected that the hand-hemispace spatial-compatibility effect would then be absent. As was expected, this effect was present at the shorter SOAs, and absent at the longer SOAs. In Experiments 2 and 3, provision of a visual precue further facilitated attentional deployment, as did blocking the presentation of various SOAs in Experiment 3. Vibrotactile and visual precues did not differ in their ability to direct attention, implying that these modalities orient attention and precue location in essentially similar ways. These findings are discussed within the context of the mechanisms though to underlie the time course of spatial compatibility and the dissipation of a fading trace of interfering spatial codes.

Adult↗

PubMed1994

Nonconscious reading? Evidence from neglect dyslexia.

In this study we present evidence which supports the view that reading mechanisms, if implicit assessed, are available also in the presence of a severe deficit of spatial awareness. A Stroop-like task was performed by a right brain-damaged patient affected by severe extrapersonal neglect and neglect dyslexia. In reading words and color words, the patient showed the usual pattern of neglect errors; omission, substitution and addition errors. However, when asked to name the colors in which color words were written, naming time was found to be affected by the meaning of those words he was not able to read correctly. The pattern of results in MD and in a group of normal subjects, who performed a modified version of the Stroop test performed by MD, have been interpreted as evidence of MD's implicit reading of the left-hand letters of color words during the Stroop test. The theoretical implications of this finding are discussed. Moreover, the comparison between the performance of MD and the performance of another group of normal subjects suggested that implicit processing in MD was carried out at a lower level of efficiency than in normals.

Adult↗

PubMed1994

Attention and control deficits following closed head injury.

This study was aimed at identifying the impaired attentional components in patients who had sustained a severe CHI several years before. A group of 14 CHI patients and a Control group (matched for age, sex and education) were tested. Experiment 1 used a dual-task paradigm (Umiltà et al., 1992). The double task-single task difference was greater for the CHI group, indicating a specific damage at a central executive stage where decision are made and responses are coordinated. Experiment 2 used a task-shifting paradigm (Morra and Roncato, 1986). The cost of shifting from one task to the other was greater for the CHI group, but only in the Short Series Condition where a new task-program could be pre-activated. Experiment 3 studied visual selective attention using Navon paradigm (1977); in this case, there was no difference between patients and controls.

Adult↗

PubMed1993

The role of right side objects in left side neglect: a dissociation between perceptual and directional motor neglect.

Based on a test introduced by Tegnér and Levander, Brain 114, 1943-1951, 1991, right brain-damaged patients were assigned to a group with unilateral perceptual neglect and a group with directional motor neglect. Brain scans showed that all directional motor neglect patients had frontal lesions, whereas in perceptual neglect patients the frontal lobes were always spared. All patients were asked to execute two tasks, which were also administered to a control group. One task consisted in pointing to tokens symmetrically distributed on a display. The other task consisted in picking up the same tokens. The tasks were first executed with the aid of vision and then in a blindfolded condition. In the case of patients with perceptual neglect, performance on the left side was better in the pick-up task than in the pointing task and improved in the blindfolded condition. Neither patients with directional motor neglect nor control patients showed these effects. The results were explained in terms of the hyperattentional hypothesis of perceptual neglect, according to which, in this form of neglect, attention is captured by the objects that lie on the right side of space.

Aged↗

PubMed1993

Aging and selective attention in arithmetic calculations.

The aim of the present work was to test the effect of aging on the capacity to perform and validate simple arithmetic calculations. Two experimental groups, eight young and eight old subjects, performed a set of three tasks (A,B,C), requiring different amounts of attentional resources. In test A, the subjects knew in advance the type of operation to be validated; in test B the subjects had to validate items of four randomly mixed operation types; in test C the subjects could use an informative cue which signalled in advance the kind of operation to be performed. The cue was true in 70% of items (valid trials) and false in 30% (invalid trials). The results confirmed a slowing down of cognitive processes in old people that partially depended on task complexity. Differently from young, old subjects could not use the informative cue to orient attention toward specific arithmetic facts: actually in test C the difference between invalid vs. valid trials does not reach statistical significance.

Adult↗

PubMed1992

Spatial representations of words and nonwords.

The first two experiments investigated whether the representations of words, besides being unitary, are also spatial in nature. Subjects were required to search for target letters in either five-letter words or five-letter nonwords. They were instructed to press the right-side key for one target and the left-side key for the other target. The center item of the letter string was always at fixation. Targets appeared one at a time, located at the second (left side) or the fourth (right side) position within the letter string. The results showed that: a) responses to targets within words were faster than responses to targets within nonwords (the word-superiority effect); b) responses to compatible stimulus-response pairings were faster than responses to incompatible stimulus-response pairings (the spatial compatibility, or, more precisely, the Simon effect); and c) in Experiment 2, left-side targets were responded to faster than right-side targets within nonwords (the left-right scanning effect). It was concluded that representations of both words and nonwords are spatial in nature. Experiment 3 was aimed at testing whether the spatial layout of the representations of words is always along the left-right horizontal dimension, regardless of the topographic transformation of the stimulus. The same words and nonwords used in the previous experiments were shown vertically and the subjects were required to make left-right discriminative responses to upper and lower target letters. The results showed the word-superiority effect but no spatial compatibility effects. It was concluded that the representation of a vertically presented word is vertically arranged.

Adult↗

PubMed1992

Splitting focal attention.

The study was based on the inverse relationship between the effect of attention on reaction time (RT) and the size of the area over which focal attention is allocated. Independent occurrence of this in 2 locations in the opposite hemifields would be evidence of attention splitting. In Experiment 1, in which the 2 locations were denoted by empty boxes, there was an inverse relationship between size of the stimulated box and RT. Experiment 2 replicated the finding with different stimulation conditions. In Experiment 3, no relationship was found between RT and length of a cuing line. In Experiment 4, in which attention was manipulated by central cues, there was an effect of box size on valid and neutral trials but not invalid trials. Observers could split focal attention and manipulate simultaneously 2 independent attentional foci on objects located in the opposite hemifields.

Adult↗