Search

Objective and Background: Patterns of brain-damaged individuals' deficits in categorizing living versus non-living things indicate separation of semantic knowledge categories in the brain. Recent work in patients with dementia suggested that semantic knowledge about social groups differs from knowledge about living and non-living things. In this study we analyzed patients' social appraisal by testing whether their degree of impairment in social-group knowledge predicted their social-group evaluative reactions (prejudice). We hypothesized that impaired knowledge about social groups would correlate with either heightened or reduced prejudice., Methods: In Rumiati et al, Cogn Neurosci (2014) http://dx.doi.org/10.1080/17588928.2013.876981, we had given a sorting task to 21 patients with frontotemporal dementia or dementia of the Alzheimer type and 23 healthy controls, to test their knowledge of social groups and living and non-living things. In this study we asked the same participants to evaluate social groups. We used controls' evaluations to rank 20 social groups from extremely negative to extremely positive. We used patients' severity of deficit in sorting social groups to predict the patients' evaluations of the groups, controlling for their levels of deficit in sorting living and non-living items. We also compared the evaluations by patients±deficits in social-group sorting to controls' evaluations., Results: The patients with impaired social-group knowledge evaluated the less-admired groups more positively than did controls, and the more-admired groups less positively., Conclusions: Impaired social-group knowledge, not a general semantic loss, predicts reduced evaluative bias. Our findings are consistent with neuroimaging evidence for a relationship between semantic and evaluative social-group processes.

Objective: We introduce a novel test that allows pictorial, nonverbal assessment of action understanding., Background: Focusing on action goals and the sequential nature of actions, the "Tomato and Tuna Test" tests whether exposure to the accomplished goal of an action is sufficient to infer the preceding action. This aspect has rarely been addressed in conventional paradigms., Methods: We used the Tomato and Tuna Test in conjunction with another task, the Kissing and Dancing Test, to detect action understanding deficits in 11 patients (mean age 72 ± 6 years) with chronic brain lesions ± aphasia. We compared their performance to an age- and education-matched control group and to 15 young controls (mean age 24 ± 3 years). To investigate the influence of language deficits on test performance, we compared the scores of our patients with and without aphasia., Results: Our patients were less accurate than the matched controls on the Tomato and Tuna Test, though not slower. The Kissing and Dancing Test did not differentiate between patients and matched controls. Young controls performed better than patients on both tests., Conclusions: We found no performance differences between our aphasic and nonaphasic patients, confirming our assumption that both tests measure action understanding without requiring intact language abilities. We recommend the "Tomato and Tuna Test" as a new nonverbal measure of action understanding that can reveal subtle deficits.

We investigated the effects of cortical stimulation on mental rotation tasks in a patient with an electrode array placed over his left primary motor cortex. The array was implanted to relieve chronic pain resulting from right brachial plexus damage. Tasks involving motor imagery were slowed down by cortical stimulation, whereas those involving visual imagery were not. When the patient performed the motor-imagery task, the interference effect on response times disappeared if the stimulator was switched off. We also probed two of the sites (anterior-lateral and posterior-medial position), and found that stimulation of the more anterior-lateral one consistently disrupted motor imagery.

Imitation is a characteristic but little-understood function of the human brain and of some higher animals. The direct matching hypothesis suggests that a specialised brain circuit is able to extract and directly copy the motor commands of another person's observed actions. Here we investigate how conscious people are of this kind of imitation. We first showed that imitation reactions are faster than simple visual reaction times, consistent with a direct matching circuit in the CNS. We next compared the perceived time of imitation reactions in 17 healthy subjects with other kinds of actions. We found a significant delay in subjects' awareness of their own imitation reactions. Thus, while imitation reactions are unusually fast, subjects are not aware of this. The brain's direct-matching circuit for imitation partly bypasses conscious awareness.