Story reading with incidental comprehension and memory: left hemisphere dominance

ABSTRACT Background: There are no studies on adults with unilateral brain lesions regarding story reading with incidental/implicit comprehension and memory, in which memory is only assessed through delayed recall. There is a need for validation of cerebral laterality in this type of verbal recall, which includes spontaneous performance (free or uncued condition (UC)), and induced-through-question performance regarding the forgotten units (cued condition (CC)). Objectives: To explore the effects of unilateral brain lesions, of oral reading with expression (RE) and comprehension (RC) on delayed recall of a story, as either UC or CC; and to validate the ability of UC and CC to discriminate the side of brain injury. Methods: Data were obtained from 200 right-handed volunteers, among whom 42 had left-hemisphere injury (LHI), 49 had right-hemisphere injury (RHI) and 109 were demographically-matched healthy participants (HP). Patients who were unable to read, understand or speak were excluded. Results: LHI individuals presented impairment of both UC and CC, in relation to the other two groups (non-LHI) with sensitivity and specificity above 70%. LHI and RHI individuals were not significantly different in RE and RC, but they were both different from HP in all the assessments except CC, in which RHI individuals resembled HP. Despite this lack of abnormality in RHI individuals during CC, about half of this group showed impairment in UC. Additionally, whereas RE had a significant effect on UC, the moral of the story (RC) had a significant effect on both UC and CC. Conclusions: The left hemisphere was dominant for this memory task involving implicit processing.

A prospective observational study of emboli exposure in open versus closed chamber cardiac surgery

Objective: Exposure to cerebral emboli is ubiquitous and may be harmful in cardiac surgery utilizing cardiopulmonary bypass. This was a prospective observational study aiming to compare emboli exposure in closed-chamber with open-chamber cardiac surgery, distinguish particulate from gaseous emboli and examine cerebral laterality in distribution. Methods: Forty patients underwent either closed-chamber procedures ( n = 20) or open-chamber procedures ( n = 20). Emboli (gaseous and solid) were detected using transcranial Doppler in both middle cerebral arteries in two monitoring phases: 1, initiation of bypass to the removal of the aortic cross-clamp; and 2, removal of aortic cross-clamp to 20 minutes after venous decannulation. Results: Total (median (interquartile range)) emboli counts (both phases) were 898 (499–1366) and 2617 (1007–5847) in closed-chamber and open-chamber surgeries, respectively. The vast majority were gaseous; median 794 (closed-chamber surgery) and 2240 (open-chamber surgery). When normalized for duration, there was no difference between emboli exposures in closed-chamber and open-chamber surgery in phase 1: 6.8 (3.6–15.2) versus 6.4 (2.0–18.1) emboli per minute, respectively. In phase 2, closed-chamber surgery cases were exposed to markedly fewer emboli than open-chamber surgery cases: 9.6 (5.1–14.9) versus 43.3 (19.7–60.3) emboli per minute, respectively. More emboli (total) passed into the right cerebral circulation: 985 (397–2422) right versus 376 (198–769) left. Conclusions: Patients undergoing open-chamber surgery are exposed to considerably higher numbers of cerebral arterial emboli after removal of the aortic cross-clamp than those undergoing closed-chamber surgery, and more emboli enter the right middle cerebral artery than the left. These results may help inform the evaluation of the pathophysiological impact of emboli exposure.

Το νευροβιολογικό υπόστρωμα της νοημοσύνης: Ανατομικά και λειτουργικά χαρακτηριστικά του εγκεφάλου που συνδέονται με γνωστικές ικανότητες

The modern era of brain imaging has enabled the direct investigation of the neurobiological substrate of intelligence thus contributing significantly to our understanding of individual differences in cognitive functions. This is a review of recent findings on the anatomical and functional underpinnings of intelligence. Specifically, the anatomical features of the brain that are associated with intelligence are brain volume, cortical thickness, white matter microstructure, and corpus callosum thickness. The functional characteristics associated with intelligence are the degree of activation of the prefrontal cortex and other areas of the parieto-frontal network, nerve conduction velocity, rate of glucose metabolism, and direction of cerebral laterality. Two recent neurobiological theories of intelligence, namely the neural efficiency hypothesis and the parieto-frontal integration theory (P-FIT), are also presented.

Cerebral laterality for writing in right- and left- handers: A functional transcranial Doppler ultrasound study

The cerebral lateralization of written language has received very limited research attention in comparison to the wealth of studies on the cerebral lateralization of oral language. The purpose of the present study was thus to further our understanding of written language lateralization, by elucidating on the relative contribution of language and motor areas. This was achieved by comparing written word generation with a writing task that has similar visuomotor demands, but does not include language (i.e., the repeated drawing of symbols). We assessed cerebral laterality in 54 left- and right-handed participants by means of functional transcranial Doppler ultrasound (fTCD), a non-invasive, perfusion-sensitive neuroimaging technique. Our findings suggest that, in right-handers, the linguistic aspect of the written word generation task recruited left-hemispheric areas during writing, similarly to oral language production. In left-handers, we failed to observe the same effect, possibly due to the great variability in cerebral laterality patterns within this group or alternatively due to the attentional demands of the symbol copying task. Future work could investigate such demands using both simple and complex stimuli in the copying condition.

CEREBRAL LATERALITY FOR THE GENERATION OF SILENT AND WRITTEN LANGUAGE IN MALE AND FEMALE RIGHT- AND LEFT- HANDERS: A FUNCTIONAL TRANSCRANIAL DOPPLER ULTRASOUND STUDY

The cerebral lateralization of language has attracted great research interest. Nevertheless, the bulk of the work focuses on language production and comprehension; research on cerebral lateralization during writing is limited. The present study assessed cerebral lateralization in 60 participants (mean age = 26.65 years, SD = 6.05, range = 20-44), 30 right-handers (14 men) and 30 left-handers (16 men), during written language production by means of functional transcranial Doppler ultrasonography (fTCD) for the first time. Findings show that left-hemispheric lateralization is observed during silent word production, for both left- and right-handers. However, during written word production, the degree of typical (left) hemispheric lateralization was significantly increased for right-handers, while left-handers presented atypical (right) hemispheric lateralization. Importantly, the difference between silent and written word generation was significantly higher in left- compared to right-handers. No main effect of sex or interactions with sex were observed. Findings suggest that a wider network of right-hemispheric areas is used during writing in left-handers. Thus, the known differences in cerebral lateralization between right- and left-handers are stronger during written language production. However, the relative contribution of language and motor areas needs to be further elucidated.