Grasping visual illusions: no evidence for a dissociation between perception and action

Neuropsychological studies prompted the theory that the primate visual system might be organized into two parallel pathways, one for conscious perception and one for guiding action. Supporting evidence in healthy subjects seemed to come from a dissociation in visual illusions: In previous studies, the Ebbinghaus (or Titchener) illusion deceived perceptual judgments of size, but only marginally influenced the size estimates used in grasping. Contrary to those results, the findings from the present study show that there is no difference in the sizes of the perceptual and grasp illusions if the perceptual and grasping tasks are appropriately matched. We show that the differences found previously can be accounted for by a hitherto unknown, nonadditive effect in the illusion. We conclude that the illusion does not provide evidence for the existence of two distinct pathways for perception and action in the visual system.     

Tinnitus als soziale Infektion?

Background

11 out of 35 male employees of a central alert team with rescue coordination function developed a tinnitus disorder. This clinical case-study highlights the psychodynamic background of this accumulation.

Methods

Employees were investigated by psychometric questionnaires and semistructured psychodynamic biografical interviews. Additionally aspects of group dynamics and organisational structure were assessed.

Results

All staff members reported adverse work conditions. Medical and psychometric examination of the tinnitus patients did not reveal severe pathological findings. The interviews identified psychodynamic conflicts dealing with autonomy and regulation of self-esteem. All tinnitus patients reported a very adverse or punitive father relation and difficulties in performing a stabile male role and self-image. Group dynamics was dominated by paranoid and regressive tendencies complicated by maladaptive coping, crude perception of external facts and a pronounced experience of aggressive impulses.

Conclusion

The remobilisation of infantile powerlessness, ineffectiveness and helplessness triggered by adverse work conditions and the introduction of a new culture of personal responsibility within the work organisation together with an impaired coping of separation conflicts enforced by traumatic aspects of the relation with the father may have promoted the tinnitus symptomatology. Additionally, due to the missing awareness of the importance of such group dynamical processes the employers contributed to an increasing psychosocial distress, which promoted the accumulated manifestation of tinnitus as a conflict expressive symptom.     

Do muscles matter for coordinated action?

This article investigates coordination stability when 2 fingers of each hand periodically tap together. The main question concerns the functional origin of the symmetry tendency, which has widely been conceived as a bias toward coactivation of homologous fingers and homologous muscular portions. In Experiment 1, the symmetry tendency was independent of finger combination. In Experiment 2, virtually identical stability characteristics were revealed under full vision and no vision. In Experiment 3, symmetrical and parallel visual labels on the fingers neither stabilized nor destabilized symmetrical and parallel tapping patterns. In Experiment 4, in which the relative position of the hands was varied, it revealed that the observed stability characteristics are to be defined in a hand-centered reference frame. Because the symmetry tendency was always independent of finger combination, the authors suggest that it is not a bias toward coactivation of homologous muscle portions but instead originates on a more abstract, functional level.     

Attentional distribution of task paramters to the two hands during bimanual performance of right- and left-handers

The author tested 12 left-handers and 12 right-handers on a bimanual circling task to examine how attention (either visual or nonvisual) to the task of 1 hand affects within-hand task parameters and whether the effects of attention manipulations are similar in left- and right-handers. The novel prediction that the attended task would be produced larger than the unattended task was confirmed in both handedness groups. The magnitude of the effect on circle size was more pronounced under visual than under nonvisual attention manipulations. The primary effects of attention were similar in the 2 handedness groups, although left-handers demonstrated some evidence of stronger parameter coupling between hands than right-handers did.     

Oddity learning by African dwarf goats ( Capra hircus)

Seventeen African dwarf goats (adult females) were trained on oddity tasks using an automated learning device. One odd stimulus and three identical nonodd stimuli were presented on a screen divided into four sectors; the sector for the odd stimulus was varied pseudorandomly. Responses to the odd stimulus were deemed to be correct and were reinforced with food. In phase 1, the goats were trained on eight stimulus configurations. From trial to trial the odd discriminandum was either a + symbol or the letter S, and the nonodd discriminandum was the symbol not used as the odd one. In phase 2, the animals were similarly trained using an unfilled triangle or a filled (i.e., solid black) circle. In phase 3, three new discriminanda were used, an unfilled, small circle with radiating lines, an unfilled heart-shaped symbol, and an unfilled oval; which of the three discriminanda was odd and nonodd was varied from trial to trial. Following these training phases, a transfer test was given, which involved 24 new discriminanda sets. These were presented twice for a total of 48 transfer test trials. Results early in training showed approximately 25% correct, which might be expected by chance in a four-choice task. After 500-2,000 trials, results improved to approximately 40-44% correct. The best-performing subject reached 60-80% correct during training. On the transfer test, this subject had 47.9% correct and that significantly exceeded 25% expected by chance. This finding suggests that some exceptional individuals of African dwarf goats are capable of learning the oddity concept.     

The social costs of punishment

Lab experiments on punishment are of limited relevance for understanding cooperative behavior in the real world. In real interactions, punishment is not cheap, but the costs of punishment are of a different nature than in experiments. They do not correspond to direct payments or payoff deductions, but they arise from the repercussions punishment has on social networks and future interactions.     

Anterior cingulate cortex activation is related to learning potential on the WCST in schizophrenia patients

The remediation of executive function in patients with schizophrenia is important in rehabilitation because these skills affect the patient's capacity to function in the community. There is evidence that instructional techniques can improve deficits in the Wisconsin Card Sorting Test (WCST) in some schizophrenia patients. We used a standard test/training phase/standard test format of the WCST to classify 36 schizophrenia patients as high-achievers, learners or non-retainers. All healthy controls performed as high-achievers. An event-related fMRI design assessed neural activation patterns during post-training WCST performance. Patients showed a linear trend between set-shifting related activation in the anterior cingulate cortex and learning potential, i.e. increased activation in high-achievers, a trend for increased activation in learners, and no activation in non-retainers compared to controls. In addition, activation in the temporoparietal cortex was highest in patients classified as learners, whereas in non-retainers activation was increased in the inferior frontal gyrus compared to controls and high-achieving patients. These results emphasize the relevance of the ACC's neural integrity in learning set-shifting strategies for patients with schizophrenia. Also, our results support the hypothesis that compensatory neural activation in patients with schizophrenia helps them to catch up with healthy controls on cognitive tasks.