Bidirectional links in the network of multiplication facts

In three experiments, we tested the hypothesis that activation of multiplication operand nodes (e.g., 3 and 8) can occur through presentation of their product (e.g., 24). In Experiments 1 and 2 we found activation of the operands when the product was presented as a cue in a number-matching task. In Experiment 3, activation also occurred in a parity-matching task, where the product (24) was not relevant to the parity matching on its operands (3 and 8). We concluded that bidirectional links exist among the operands and their product for multiplication problems and these links can be activated in a purely stimulus-driven manner. We suggest this may constitute the basis for the solution of simple divisions by mediation through the complementary multiplication facts.     

Suppression of extinction with TMS in humans: from healthy controls to patients

We review a series of studies exemplifying some applications of single-pulse and paired-transcranial magnetic stimulation (TMS) in the study of spatial attention and of its deficits. We will focus primarily on sensory extinction, the failure to consciously perceive a contralesional sensory stimulus only during bilateral stimulation of homologous surfaces. TMS studies in healthy controls show that it is possible either to interfere or modulate the excitability of the parietal cortex during sensory (i.e. tactile and visual) attentional tasks, thus reproducing a condition of virtual extinction. TMS studies in patients with unilateral (mainly right) brain damage show that the modulation of the unbalance in cortical excitability between the two cerebral hemispheres transiently improves contralesional sensory extinction. These studies show the possible application of TMS not only as a research method in healthy subjects, but also as a tool for inducing brain excitability changes in patients with sensory extinction, which could be useful for supporting the rehabilitation of this deficit.     

Number magnitude orients attention, but not against one’s will

Recent evidence has shown that uninformative numbers can trigger attention shifts congruent with the spatial representation of number magnitude (Fischer, Castel, Dodd, & Pratt, 2003). In the present study, three spatial-cuing experiments whose aim was to qualify the automaticity of this numbermediated orienting are described. Experiment 1 replicated the phenomenon, showing that uninformative numbers can evoke orienting in a simple detection task. In Experiment 2, target location was random, but the participants were encouraged to shift attention to the left in response to large numbers and to the right in response to small numbers. No evidence for strong automaticity was observed, since the participants’ performance was better when left-side targets were preceded by large numbers than when they were preceded by small numbers and vice versa. Experiment 3 corroborated this pattern by comparing gaze- and number-mediated cuing under conditions of real counterpredictiveness. The results indicate that unlike gaze-driven orienting, number-mediated orienting is not obligatory.     

Is handedness recognition automatic? A study using a Simon-like paradigm

The authors used a modified Simon task (J. R. Simon, 1969) to assess the automatic recognition of handedness. Participants responded to the color of a circle in the center of the photograph of a right or a left hand, displayed in the center of the computer screen. A regular Simon effect was found for back views, whereas a reverse Simon effect was found for palm views. This pattern of results was found when the forearm was present (Experiment 2), when 1 finger at a time was rendered invisible (Experiment 3), and when the hands were connected to a body image (Experiment 4). When the hands were cut at the wrist, no effect emerged (Experiment 1). These findings suggest an automatic encoding of the relative position of the hand in relation to the body (imaginary or real) rather than the automatic encoding of handedness.     

Right-left prevalence with task-irrelevant spatial codes

The present work investigated the right-left prevalence effect caused by the automatic activation of horizontal and vertical spatial codes in a task (Simon task) in which spatial information is task-irrelevant. Experiment 1 showed a horizontal Simon effect and a vertical Simon effect with a two-dimensional stimulus-response set. In Experiments 2 and 3, the right-left prevalence was obtained in two-dimensional Simon tasks with two contralateral effectors and four effectors respectively. Experiment 4 showed that horizontal coding is based on multiple spatial codes, whereas only one spatial code was formed for vertical coding. On the whole, these results support the notion that the right-left prevalence effect is a general phenomenon affecting spatial coding, and suggest that the horizontal dimension is prevalent because it is based on multiple spatial codes.     

Two brains, one clock

A recent study has shown that information about the duration of brief time intervals acquired by one side of the brain is readily available to the other cerebral hemisphere in a patient in which the corpus callosum and the other forebrain commissures have been sectioned. This strongly suggests that the internal clock that measures time duration is subcortical, and that its output can be easily projected to both hemispheres via subcortical commissures.     

Imposing structure on a Corsi-type task: evidence for hierarchical organisation based on spatial proximity in serial-spatial memory

Structure was imposed on a tapping task by requiring participants to reproduce sequences of responses to icons organised in spatial clusters. A first experiment featured sequences either segregated or not segregated by clusters. Accuracy was higher for sequences segregated by clusters. Moreover, inter-response times were longer at cluster boundaries than within cluster boundaries. To rule out possible confounding effects of movement length, this temporal pattern was replicated in a second experiment requiring a single response indicating the next sequential step, following the presentation of a portion of a previously practised sequence. These results suggest that sequence reproduction can be sustained by a hierarchical representation based on spatial proximity and provide a first indication of the role of spatial structure in serial-spatial memory.     

The mental representation of verb-noun compounds in Italian: evidence from a multiple single-case study in aphasia

This study seeks information on the mental representation of Verb–Noun (VN) nominal compounds through neuropsychological methods. The lexical retrieval of compound nouns is tested in 30 aphasic patients using a visual confrontation naming task. The target names are VN compounds, Noun–Noun (NN) compounds, and long morphologically simple nouns (LSN). In order to check the ability to produce simple nouns and verbs in the same participants, a further visual confrontation naming task of objects and actions is used. Results of the study confirm that several patients with disproportionate verb deficit are also impaired in naming VN compounds. Data are in favor of a (de)compositional processing of compound words. A further group of patients is selectively more impaired with compound nouns than with comparably long simple nouns, irrespective of their VN or NN morphological structure. It is suggested that this impairment is to be ascribed to a specific disorder in retrieving two different lexemes with a single lexical entry.     

Automatic spatial coding of perceived gaze direction is revealed by the Simon effect

In a typical Simon task, the (irrelevant) spatial position of the stimulus interferes with the processing of the salient characteristic (e.g., color). We used the Simon effect to investigate the automatic processing of gaze cues. We show that a simple drawing of schematic eyes automatically generates a spatially defined code of gaze direction. Although completely irrelevant to the task, direction of gaze influenced reaction times in a spatially selective two-choice discrimination based on eye color. Moreover, in one experiment employing an orthogonal manipulation of stimulus position and gaze direction, we found that coding of gaze direction is independent of stimulus spatial coding. Our finding of a “gazedirection Simon effect” is congruent with the hypothesis that gaze direction is coded by a specialized mechanism.     

The SNARC effect: an instance of the Simon effect?

Our aim was to investigate the relations between the Spatial-Numerical Association of Response Codes (SNARC) effect and the Simon effect. In Experiment 1 participants were required to make a parity judgment to numbers from 1 to 9 (without 5), by pressing a left or a right key. The numbers were presented to either the left or right side of fixation. Results showed the Simon effect (left-side stimuli were responded to faster with the left hand than with the right hand whereas right-side stimuli were responded to faster with the right hand), and the SNARC effect (smaller numbers were responded to faster with the left hand than with the right hand, whereas larger numbers were responded to faster with the right hand). No interaction was found between the Simon and SNARC effects, suggesting that they combine additively. In Experiment 2 the temporal distance between formation of the task-relevant non-spatial stimulus code and the task-irrelevant stimulus spatial code was increased. As in Experiment 1, results showed the presence of the Simon and SNARC effects but no interaction between them. Moreover, we found a regular Simon effect for faster RTs, and a reversed Simon effect for longer RTs. In contrast, the SNARC effect did not vary as a function of RT. Taken together, the results of the two experiments show that the SNARC effect does not simply constitute a variant of the Simon effect. This is considered to be evidence that number representation and space representation rest on different neural (likely parietal) circuits.