STIMA: a short screening test for ideo-motor apraxia, selective for action meaning and bodily district.

We propose STIMA, a short test for ideo-motor apraxia, allowing us to quantify the apraxic deficit according to action meaning and affected body segment. STIMA is based on a neurocognitive model holding that there are two processes involved in action imitation (i.e., a semantic route for recognizing and imitating known gestures, and a direct route for reproducing new gestures). The test allows to identify which imitative process has been selectively impaired by brain damage (direct vs. semantic route) and possible deficits depending on the body segment involved (hand/limb vs. hand/fingers). N = 111 healthy participants were administered with an imitation task in two separated blocks of known and new gestures. In each block, half of the gestures were performed mainly with the proximal part of the upper limb and the remaining half with the distal one. It resulted in 18 known gestures (nine proximal and nine distal) and 18 new gestures (nine proximal and nine distal) for a total of 36. Each gesture was presented up to a maximum of two times. Detailed criteria are used to assign the final imitation score. Cut offs, equivalent scores and main percentile scores were computed for each subscale. Participants imitated better known than new gestures, and proximal better than distal gestures. Age influenced performance on all subscales, while education only affected one subscale. STIMA is easy and quick to administer, and compared to previous tests, it offers important information for planning adequate rehabilitation programs based on the functional locus of the deficit.

Good division, but bad addition, subtraction and multiplication. A "leftmost-first" bug?

The present investigation reports the case of patient AS, ambidextrous, who showed a selective problem with arithmetical procedures in addition, subtraction and multiplication, contrasting with complete sparing of division. AS displayed a specific and never described "bug" error, involving the selection of digits that have to be added, subtracted or multiplied. This bug consisted in inverting the order of the numbers that have to be selected to correctly solve the operation. In particular, AS selected the numbers beginning from the leftmost position. This bug spared division, since it is the only operation that requires starting from the leftmost digit(s). The present case would suggest that some aspects of arithmetical procedures are operation independent. Moreover, an account of the nature of the syntactic rule getting lost in AS's performance has been proposed.

Action performance and action-word understanding: evidence of double dissociations in left-damaged patients.

It has been proposed that language and action representational systems overlap when the tasks used to assess them involve the same stimuli and require abilities acquired at similarly early developmental stage. We matched variables at task and stimulus level to test this hypothesis in a group of 12 left-damaged patients (and 17 controls). At the patients' group level, we replicated previously reported correlations between linguistic and nonlinguistic tasks. When performances were analysed individually, however, double dissociations were observed between the ability to imitate pantomimes and the ability to produce and comprehend the corresponding action verbs, as well as between the ability to use tools and the ability to comprehend the corresponding tool nouns. These findings suggest that processing action words is independent of the ability to produce the associated object-directed actions. Double dissociations were also found between the ability to comprehend action verbs and the ability to comprehend tool nouns. Moreover, action and tool naming showed differential effects of age of acquisition, suggesting that the two word categories meet the lexical organization by word class (nouns and verbs), even when related to identical action concept. Dissociations at behavioural level are supported by anatomical dissociations shown in the analysis of patients' lesions.

Praxic and executive components in tool use learning: the role of imitation.

Recent research in comparative psychology suggests that similarities between the behaviour of two individuals may not be the consequence of imitation only, but also of nonimitative social-learning processes. In the present study we aimed to investigate whether these alternative learning processes can take place in human adults, specifically in patients whose ability to imitate has been reduced by brain damage. Left (LBD) and right (RBD) brain-damaged patients were asked to perform four tool use tasks in three experimental conditions: exposure to the apparatus (N); demonstration of the correct solution (C); and demonstration of a failed attempt followed by the correct solution to the problem (I + C). Results suggest that the left hemisphere is indeed critical for action and that selective neuropsychological deficits can affect action imitation and selection of goal-directed movements, independently from each other. Findings also indicate that when the ability to imitate actions is lowered emulation may become available.

A left basal ganglia case of dynamic aphasia or impairment of extra-language cognitive processes?

We report the case of OTM who presented with dynamic aphasia following a stroke that occurred in the left basal ganglia. He showed drastically reduced spontaneous speech in the context of well preserved naming, repetition and comprehension skills. OTM was particularly impaired in generating words, sentences and phrases when cued by a stimulus allowing many response options. By contrast, when a single response was strongly suggested by a stimulus, he could generate verbal responses adequately. OTM's non-verbal response generation abilities varied across tasks. He performed in the normal range in a motor movement generation test and he produced as many figures as controls when tested on a figural fluency task. He showed, however, many perseverations on this test. Moreover in a random number generation task he produced more responses that were part of ascending and descending series of numbers. The patient's impairments are interpreted as a consequence of two deficits. The first of these consists of an inability to generate verbal responses particularly in situations of high competition and involves the function of left frontal regions. The second deficit is one of impaired novel thought generation as evidenced by perseverations. This second deficit has been proposed to be a function of basal ganglia damage.

What is the role of motor simulation in action and object recognition? Evidence from apraxia.

An important issue in contemporary cognitive neuroscience concerns the role of motor production processes in perceptual and conceptual analysis. To address this issue, we studied the performance of a large group of unilateral stroke patients across a range of tasks using the same set of common manipulable objects. All patients (n = 37) were tested for their ability to demonstrate the use of the objects, recognize the objects, recognize the corresponding object-associated pantomimes, and imitate those same pantomimes. At the group level we observed reliable correlations between object use and pantomime recognition, object use and object recognition, and pantomime imitation and pantomime recognition. At the single-case level, we document that the ability to recognize actions and objects dissociates from the ability to use those same objects. These data are problematic for the hypothesis that motor processes are constitutively involved in the recognition of actions and objects and frame new questions about the inferences that are merited by recent findings in cognitive neuroscience.