Biomedical subjects

Paloma Marí-Beffa

Publications and source records attributed to Paloma Marí-Beffa.

5 recordsLinked to original sources

PubMed2005

Lack of inhibition in Parkinson's disease: evidence from a lexical decision task.

Persons affected by Parkinson's disease (PD) often show an increased semantic priming effect from target words in lexical decision tasks (hyper-priming) as compared to age-matched controls. In this study, a lexical decision task was used to investigate both semantic priming (Experiment 1) and repetition priming (Experiment 2) from distractor words in PD patients and age-matched controls. With this negative priming procedure, target words in successive trials are never related, and therefore participants always have to switch between unrelated target words. Instead, it is the distractor prime word that is either related or unrelated to the subsequent target, giving the measure of priming. Results showed that PD patients demonstrated a robust effect of positive semantic priming from distractor words. Participants from the control group did not show any semantic priming effect (positive or negative) from distractors. Similarly, PD patients showed positive repetition priming from distractor words, but the control group showed significant repetition negative priming. These results support the view that the hyper-priming effect typically shown by persons with Parkinson's disease is the result of impaired inhibitory processes required to control word activation during reading.

Aged↗

PubMed2005

Dissociating object- and response-based components of negative priming through effects of practice.

The negative priming (NP) effect is the slowing of responses to an imperative stimulus (probe) that has recently been ignored (prime). Prevailing accounts of the phenomenon attribute it to a variety of causes, all centered on a representation of the stimulus event itself. However, we argue that the most commonly used NP paradigms confound stimulus- and response-based factors. In two experiments, we demonstrate the importance of response factors in producing NP and show clear empirical dissociations between object- and response-centered NP when studying their time courses over extended practice. When distractors compete for a response (response-based), the NP effect is both more robust and more resistant to the effects of practice. On the other hand, when prime distractors do not compete for response (object-based), they yield weaker NP effects that disappear with practice. We conclude that the NP effects shown in the most common procedures are produced by a combination of distinct factors that tend to act in the same direction.

Attention↗

PubMed2004

ERP analyses of task effects on semantic processing from words.

Semantic (positive) priming refers to the facilitated processing of a probe word when preceded by a related prime word, and is a widely used technique for investigating semantic activation. However, the effect is interrupted or eliminated when attention is directed to low-level features of the prime word, such as its letters, a result which has been used to question the automaticity of semantic processing. We investigated this issue using both behavioural [reaction time (RT)] and electrophysiological measures [event-related potentials (ERPs)]. Subjects performed semantic categorization (living vs. nonliving) and letter search ("A" or "E") tasks on prime words followed by lexical decision on the probe. RT results showed the expected elimination of semantic priming following letter search. However, both prime tasks were affected by the semantic category of the prime, indicating that the meaning was processed. The ERP results supported this conclusion: an early component previously associated with automatic semantic processing [the Recognition Potential (RP)] was sensitive to the category of the prime word irrespective of the prime task. However, a later component (N400) was significantly affected by the task, in both the prime (categorization task) and probe words (semantic priming). The results dissociate rapid, automatic semantic processing from semantic priming. We suggest that a later inhibitory control mechanism suppresses this semantic activation when it is not relevant to the task, and that this produces the loss of semantic priming.

Adolescent↗

PubMed2002

Negative priming from the non-selected meaning of the homograph.

In this article we address the question of whether semantic ambiguity resolution involves the central inhibition of the non-selected meaning of a homograph. Most previous studies on this topic have either not clearly required semantic selection, or have induced this disambiguation by manipulating the context. These studies have not observed clear inhibitory effects on the non-selected meaning of the type studied in negative priming. We suggest that this kind of central inhibition may depend on task demands, and will be more easily observed in tasks where meaning selection is clearly required and is not made easier by cueing or context. In this study, participants had to perform a semantic judgment task in the prime display. Semantic priming from both the selected and the non-selected meaning of homographs was measured by showing facilitation for the selected meaning and inhibitory effects of the non-selected meaning. Participants with slow but accurate performance during the task were mainly responsible for this semantic negative priming effect, reflecting the role of inhibition on task-oriented control. The 'negative priming' effect is discussed in relation to current theories of attentional selection.

Adolescent↗

PubMed2002

Stroop interference effects in partially colored Stroop words.

In the Stroop task word reading is thought to be automatic since it runs without intentional monitoring and is difficult to avoid. This view has recently been challenged by observations that Stroop interference is reduced when only part of the Stroop word is colored. In this study we asked whether the extent of Stroop interference varies with the position of the colored letter(s). We observed that Stroop interference was smallest when the first letter(s) were colored and largest when either the last letter(s) or whole word were colored. On these findings we suggest that colored and noncolored parts of partially colored words are processed separately and differently, and that selection of the color dimension for explicit report entails inhibition of the to-be-ignored colored letters.

Humans↗