Predictive representation of other people's actions in joint action planning: an EEG study.

It has been postulated that when people engage in joint actions they form internal representations not only of their part of the joint task but of their co-actors' parts of the task as well. However, empirical evidence for this claim is scarce. By means of high-density electroencephalography, this study investigated whether one represents and simulates the action of an interaction partner when planning to perform a joint action. The results showed that joint action planning compared with individual action planning resulted in amplitude modulations of the frontal P3a and parietal P3b event-related potentials, which are associated with stimulus classification, updating of representations, and decision-making. Moreover, there was evidence for anticipatory motor simulation of the partner's action in the amplitude and peak latency of the late, motor part of the Contingent Negative Variation, which was correlated with joint action performance. Our results provide evidence that when people engage in joint tasks, they represent in advance each other's actions in order to facilitate coordination.

EEG correlates of Fitts's law during preparation for action.

Humans' inability to move fast and accurately at the same time is expressed in Fitts's law. It states that the movement time between targets depends on the index of difficulty, which is a function of the target width and the inter-target distance. The present study investigated the electrophysiological correlates of Fitts's law during action planning using high-density electroencephalography. Movement times were scaled according to Fitts's law, indicating that participants could not overcome the speed-accuracy trade-off during a 1-s preparation period. Importantly, the index of difficulty of the planned movement correlated linearly with the amplitudes of the cognitive N2 and P3b components, which developed during the planning period over parieto-occipital areas. These results suggest that the difficulty of a movement during action planning is represented at a level where perceptual information about the difficulty of the ensuing action is linked to motor programming of the required movement.

Maintaining grip: anticipatory and reactive EEG responses to load perturbations.

Previous behavioral work has shown the existence of both anticipatory and reactive grip force responses to predictable load perturbations, but how the brain implements anticipatory control remains unclear. Here we recorded electroencephalographs while participants were subjected to predictable and unpredictable external load perturbations. Participants used precision grip to maintain the position of an object perturbed by load force pulses. The load perturbations were either distributed randomly over an interval 700- to 4,300-ms (unpredictable condition) or they were periodic with interval 2,000 ms (predictable condition). Preparation for the predictable load perturbation was manifested in slow preparatory brain potentials and in electromyographic and force signals recorded concurrently. Preparation modulated the long-latency reflex elicited by load perturbations with a higher amplitude reflex response for unpredictable compared with predictable perturbations. Importantly, this modulation was also reflected in the amplitude of sensorimotor cortex potentials just preceding the long-latency reflex. Together, these results support a transcortical pathway for the long-latency reflex and a central modulation of the reflex grip force response.

New perspectives in the management of sigmoid diverticulitis.

The sigmoid colon is the part of the large intestine, which most commonly involved in diverticular disease due to its anatomical properties. Diverticular disease of the colon is being seen with increasing frequency mostly in western countries. Diverticulitis results from inflammation and subsequent perforation of a colonic diverticulum. Mild forms of diverticulitis usually present with gradually increasing symptoms from the lower left quadrant of the abdomen, whereas acute complicated disease is characterised by dramatic onset of abdominal pain, followed by fever within a few hours. The standard treatment for uncomplicated diverticulitis is bowel rest, with liquid diet or intravenous fluids in combination with antibiotics. Prophylactic resection is not to be recommended for patients with diverticular disease, but a high-fibre diet may afford protection by preventing further complications. Patients not responding to conservative treatment within the first 24 hours require further evaluation by computed tomography or ultrasonography. Fistula formation and intestinal obstruction are indications for surgical intervention, although the frequent recurrent attacks, which commonly afflict these patients, are seldom associated with severe complications. Laparoscopic approach has been introduced in the diagnosis and definitive treatment of uncomplicated diverticulitis, with less morbidity and mortality rates, and hospitalisation of the patients and in these terms could be promising in the future.