Pliers,not fingers: Tool-action effect in a motor intention paradigm

Tool-use representations have been suggested to be supported by the representation of hand actions and/or by the representation of tool actions. A major issue is to know which one of these two representations is preferentially activated when people intend to use a tool. To address this issue, we developed a paradigm in which, in 20% of trials, participants had to press a button and actually use pliers to move an object in response to a predefined target symbol. Importantly, two masks hiding the symbols performed “opening” or “closing” actions before symbols appeared. In Experiment 1, participants used normal pliers: Hand’s opening actions induced pliers’ opening actions and vice versa for hands’ closing actions. Results indicated a compatibility effect between masks’ actions and pliers’ actions. Participants were faster to press the button in response to the target symbol when opening and closing actions of the masks were congruent with the corresponding actions of the hand. In Experiment 2 participants used inverse pliers: Hand’s opening actions involved pliers’ closing actions and vice versa. In this situation, results showed that the congruency of masks’ actions occurred with pliers’ actions and not hand’s actions. Altogether, these findings demonstrate that intention of use is preferentially based on the representation of tool actions, and have important implications for the domain of neuropsychology of tool use and the theories of goal-directed behavior.     

Occipital gamma activation during Vipassana meditation

Long-term Vipassana meditators sat in meditation vs. a control rest (mind-wandering) state for 21 min in a counterbalanced design with spontaneous EEG recorded. Meditation state dynamics were measured with spectral decomposition of the last 6 min of the eyes-closed silent meditation compared to control state. Meditation was associated with a decrease in frontal delta (1–4 Hz) power, especially pronounced in those participants not reporting drowsiness during meditation. Relative increase in frontal theta (4–8 Hz) power was observed during meditation, as well as significantly increased parieto-occipital gamma (35–45 Hz) power, but no other state effects were found for the theta (4–8 Hz), alpha (8–12 Hz), or beta (12–25 Hz) bands. Alpha power was sensitive to condition order, and more experienced meditators exhibited no tendency toward enhanced alpha during meditation relative to the control task. All participants tended to exhibit decreased alpha in association with reported drowsiness. Cross-experimental session occipital gamma power was the greatest in meditators with a daily practice of 10+ years, and the meditation-related gamma power increase was similarly the strongest in such advanced practitioners. The findings suggest that long-term Vipassana meditation contributes to increased occipital gamma power related to long-term meditational expertise and enhanced sensory awareness.     

Spotting animals in natural scenes: efficiency of humans and monkeys at very low contrasts

The ability of monkeys to categorize objects in visual stimuli such as natural scenes might rely on sets of low-level visual cues without any underlying conceptual abilities. Using a go/no-go rapid animal/non-animal categorization task with briefly flashed achromatic natural scenes, we show that both human and monkey performance is very robust to large variations of stimulus luminance and contrast. When mean luminance was increased or decreased by 25–50%, accuracy and speed impairments were small. The largest impairment was found at the highest luminance value with monkeys being mainly impaired in accuracy (drop of 6% correct vs. <1.5% in humans), whereas humans were mainly impaired in reaction time (20 ms increase in median reaction time vs. 4 ms in monkeys). Contrast reductions induced a large deterioration of image definition, but performance was again remarkably robust. Subjects scored well above chance level, even when the contrast was only 12% of the original photographs (≈81% correct in monkeys; ≈79% correct in humans). Accuracy decreased with contrast reduction but only reached chance level -in both species- for the most extreme condition, when only 3% of the original contrast remained. A progressive reaction time increase was observed that reached 72 ms in monkeys and 66 ms in humans. These results demonstrate the remarkable robustness of the primate visual system in processing objects in natural scenes with large random variations in luminance and contrast. They illustrate the similarity with which performance is impaired in monkeys and humans with such stimulus manipulations. They finally show that in an animal categorization task, the performance of both monkeys and humans is largely independent of cues relying on global luminance or the fine definition of stimuli.     

Finger-number interaction: an ideomotor account

Recent findings have shown that processing numerical magnitude may interact with finger movements through goal-directed movements. Here we tested these number-finger interactions in a response-effect (R-E) paradigm. During a learning phase, participants read meaningless consonant-vowel (CV) syllables immediately followed by unrelated opening or closing finger movements; during a transfer test, they again named these CV syllables in response to processing a small or a large number. The results showed that responding to a large magnitude number during the transfer phase was slower in an incompatible situation, that is, when the answer was the CV syllable that had been associated to a grip closure during the learning phase. This interference effect demonstrates that ideomotor principles can account for the link between the meaning of numbers and the perception of actions through an anticipated-magnitude code.     

Remembering – but not knowing – disturbs the relational bindings newly established in short-term/working memory: an age-group comparison

The aim of this study was to highlight that episodic memory and working memory compete for the same resource, which would be diminished in aging. Using the remember/know paradigm, we compared the interference related to the retrieval of words on the parallel processing of preestablished relational bindings (Shifting condition) or newly established relational bindings (Updating condition). Within each age-group, participants had comparable performances in remembering across recognition conditions. However, the results showed that only updating activity was impaired after a remember response was given in the younger group. This specific interaction between updating and remembering – but not knowing – tends to indicate that both working memory and episodic memory rely on the ability to establish contextualized representations. In the older group, the performance in updating activity was impaired regardless of the kind of the competing retrieval. Limitations in terms of interference hypothesis and limited resource hypothesis are discussed.