Component mechanisms underlying the processing of hierarchically organized patterns: inferences from patients with unilateral cortical lesions

Subjects identified target letters that occurred randomly at the local or global level in a divided attention task. The visual angle of the stimuli was varied. Neurologically intact controls showed a reaction time advantage for local targets which increased as visual angle increased. Patients with lesions centered in the posterior superior temporal gyrus (STG) showed a larger local advantage than controls if the lesion was on the right and a global advantage if the lesion was on the left. STG patients were no more influenced by visual angle than were controls. Control subjects also showed the usual interference of global distractors on responding to local targets. STG patients showed little evidence of interference. Control patients with lesions centered in the rostral inferior parietal lobe performed normally. The findings suggest that several component mechanisms are involved in the processing of hierarchical levels of structure, each linked to specific anatomical regions.     

Spoken syntax in children with acquired unilateral hemisphere lesions

The spoken syntax of eight left hemisphere lesioned and eight right hemisphere lesioned children were compared to matched controls. The children's lesions were acquired between 0.08 and 6.17 years of age (mean = 1.33 years), and at the time of testing they were between 1.67 and 8.15 years of age (mean = 4.19). Based on analyses of spontaneous language samples, left hemisphere lesioned subjects performed more poorly than did their controls on most measures of simple and complex sentence structure. In contrast right lesioned subjects performed similarly to their controls on these measures, except for a tendency to make more errors in simple sentence structures. These findings provide further evidence that the left and right hemispheres are not comparable in supporting syntactic abilities.     

Gastric secretion and activity-stress lesions in the rat

In Experiment 1, gastric samples were obtained by means of a pylorus ligation procedure on either the first or last day of the activity-stress procedure. Experimental rats had more stomach lesions and showed a drop in gastric acid on the last day collection. In Experiment 2, rats were surgically prepared with gastric cannulas and pyloric cuffs, and first and last day collections were obtained from the same animal. Experimental activity rats revealed more stomach lesions and a corresponding drop in gastric acid on the last collection than did control rats, which thereby suggests that acid was not a significant etiological variable. The destruction of acid-bearing parietal cells or the back diffusion of hydrogen ions could also explain the low acid values in rats with stomach lesions.     

Changes in frontal and posterior cortical activity underlie the early emergence of executive function

Executive function (EF) is a key cognitive process that emerges in early childhood and facilitates children's ability to control their own behavior. Individual differences in EF skills early in life are predictive of quality‐of‐life outcomes 30 years later (Moffitt et al., 2011). What changes in the brain give rise to this critical cognitive ability? Traditionally, frontal cortex growth is thought to underlie changes in cognitive control (Bunge & Zelazo, 2006; Moriguchi & Hiraki, 2009). However, more recent data highlight the importance of long‐range cortical interactions between frontal and posterior brain regions. Here, we test the hypothesis that developmental changes in EF skills reflect changes in how posterior and frontal brain regions work together. Results show that children who fail a “hard” version of an EF task and who are thought to have an immature frontal cortex, show robust frontal activity in an “easy” version of the task. We show how this effect can arise via posterior brain regions that provide on‐the‐job training for the frontal cortex, effectively teaching the frontal cortex adaptive patterns of brain activity on “easy” EF tasks. In this case, frontal cortex activation can be seen as both the cause and the consequence of rule switching. Results also show that older children have differential posterior cortical activation on “easy” and “hard” tasks that reflects continued refinement of brain networks even in skilled children. These data set the stage for new training programs to foster the development of EF skills in at‐risk children.