A Critical Review of the Clinical Effects of Therapeutic Irradiation Damage to the Brain: The Roots of Controversy

We critically examined the damaging affects of therapeutic irradiation by comparing results from cross-disciplinary studies of early- and late-delayed radiotherapy effects. Focus is attained by concentrating on clinical treatment issues (volume of brain, dose, timing of effects, age, modality types, and stereotactic treatment techniques), rather than on methodological means or problems, which is necessary to understand the mechanisms and characteristics of radiotherapy-induced behavioral dysfunction including cognition. We make observations and hypotheses about the actual risks from radiotherapy that could be informative in the treatment decision process, and which may lessen the concerns of some patients and their families about the risks they take when receiving radiation. Conditions that predispose to radiation injury are reviewed: (1) higher doses even to part of the brain versus lower doses to the whole brain, (2) combined treatment modalities, (3) malignancy itself, (4) radiation early during postnatal brain development, and (5) late-delayed effects (more than 3 years posttreatment). Current neurocognitive frameworks for understanding cognitive change over time in children and adults are summarized, along with the literature on effects of brain tumors and treatment on depression. No studies have as yet identified candidate brain regions that are more sensitive to radiotherapy. Two studies have provided early, preliminary evidence for a specific vulnerability of visual attention/memory to the early stage of late radiation damage. Furthermore, radiation effects appear severe only in a minority of patients. Risk is related to direct and indirect effects of cancer type, concurrent clinical factors, and premorbid risk factors.     

Neuropsychological assessment with the Visual Gestalt Test: psychometric properties and differential diagnostic probabilities

The Visual Gestalt Test is a neuropsychological instrument developed for evaluation of learning and memory of visuo-spatial material. A revised strategy of scoring has motivated the present study, where data from 153 normal persons, 99 epilepsy patients, and 24 depressed patients are presented and compared. The Visual Gestalt Test is observed to discriminate between normal and diagnosed groups in several ways. Additionally it is found to discriminate between depressed and brain damage subgroups of patients. Data are presented in order to supplement previously published ways of scoring and norms. Practical guidelines for the clinical applications of the test are suggested as perspectives.     

The relationship between prosody and breathing in spontaneous discourse

This article is concerned with the role of prosody in discourse. Three experiments explored the relationship between inspiration, declination, and syntactic boundaries in normal and RHD participants. Fundamental frequency and intensity were measured at the beginning and end of breath units excised from conversational samples. The results revealed evidence of declination of intensity in all samples measured. However, resetting of fundamental frequency was observed only in the samples of normal participants and then only when a breath coincided with the beginning of a sentence. The results suggest that resetting and declination play separate roles in discourse parsing.     

Trading jobs for health: Ionizing radiation,occupational ethics,and the welfare argument

Blue-collar workers throughout the world generally face higher levels of pollution than the public and are unable to control many health risks that employers impose on them. Economists tend to justify these risky workplaces on the grounds of the compensating wage differential (CWD). The CWD, or hazard-pay premium, is the alleged increment in wages, all things being equal, that workers in hazardous environments receive. According to this theory, employees trade safety for money on the job market, even though they realize some of them will bear the health consequences of their employment in a risky occupational environment. To determine whether the CWD or hazard-pay premium succeeds in justifying alleged environmental injustices in the workplace, this essay (1) surveys the general theory behind the “compensating wage differential”; (2) presents and evaluates the “welfare argument” for the CWD; (3) offers several reasons for rejecting the CWD, as a proposed rationale for allowing apparent environmental injustice in the workplace; and (4) applies the welfare argument to an empirical case, that of US nuclear workers. The essay concludes that this argument fails to provide a justification for the apparent environmental injustice faced by the 600,000 US workers who have labored in government nuclear-weapons plants and laboratories. Shrader-Frechette is O’Neill Professor of Philosophy and Concurrent Professor of Biological Sciences. She teaches ethics, philosophy of science, quantitative risk assessment, and environmental science. The latest of her 280 articles and 14 books is her 2002 volume from Oxford University Press, Environmental Justice: Creating Equality, Reclaiming Democracy. Shrader-Frechette is grateful to the National Science Foundation, Ethics and Values Program, for research support for this article through grant SES-98-10611. All opinions are those of the author, not the NSF.     

Consensus conference on environmental values in radiation protection: a report on building consensus among experts

During the fall of 2001 (October 22–25), The Norwegian Radiation Protection Authority (NRPA) and the Agricultural University of Norway arranged a consensus conference on the protection of the environment against ionising radiation. The motive for the conference was the need to study the ethical and philosophical basis for protection of nature in its own right. The conference was funded by Nordic Nuclear Safety Research (NKS), in cooperation with the International Union of Radioecology (IUR). The National Committee for Research Ethics in Science and Technology (NENT) was hired as facilitators for the consensus process. This paper will give a brief outline of the aims and method of the conference, distinguishing these from other kinds of consensus conferences. The paper ends with some general reflections on the appropriateness of seeking consensus on ethics-related issues among experts.     

Temporal parameters as cues to phrasal boundaries: a comparison of processing by left- and right-hemisphere brain-damaged individuals

Two experiments were conducted to examine the ability of left- (LHD) and right-hemisphere-damaged (RHD) patients and normal controls to use temporal cues in rendering phrase grouping decisions. The phrase "pink and black and green" was manipulated to signal a boundary after "pink" or after "black" by altering pre-boundary word durations and pause durations at the boundary in a stepwise fashion. Stimuli were presented to listeners auditorily along with a card with three alternative groupings of colored squares from which to select the presented alternative. Results revealed that normal controls were able to use both temporal cues to identify the intended grouping. In contrast, LHD patients required longer than normal pause durations to consistently identify the intended grouping, suggesting a higher than normal threshold for perception of temporal prosodic cues. Surprisingly, the RHD patients exhibited great difficulty with the task, perhaps due to the limited acoustic cues available in the stimuli.     

Effects of Right- and Left-Hemisphere Damage on Understanding Conversational Implicatures

Processing of implicatures was examined in 27 right-brain-damaged (RBD) and 31 left-brain-damaged (LBD) stroke patients with focal lesions using a new implicatures battery (IB) as part of an exploration of the neural basis and modularity of natural language pragmatics. Following Grice, we sampled implicatures of Quantity, Quality, Relation, and Manner. Verbal implicatures consisted of two-sentence conversational vignettes which are literally problematic. Nonverbal implicatures consisted mostly of famous paintings that are literally problematic (e.g., Magritte's "Le Domain d'Arnheim"). The patient has to identify and solve the problem. To compare with performance on the IB, patients also received a Hebrew adaptation of Gardner and Brownell's Right Hemisphere Communication Battery, a new test of basic speech acts (verbal and nonverbal assertions, questions, requests, and commands), a Hebrew version of the Western Aphasia Battery, and standardized neuropsychological tests. Both LBD and RBD patients were significantly impaired in implicature processing relative to age-matched normal controls. In general, both patient groups showed weak correlations of implicatures with extents of lesions in left perisylvian language area or its right-hemisphere (RH) homolog. However, performance of LBD and RBD patients on the IB revealed different patterns of correlations with other pragmatic, language, and nonlanguage tests. In LBD patients, there was a greater association between performance on verbal and nonverbal implicatures and between performance on implicatures and basic speech acts than in RBD patients. Given the different modes in which right-and left-hemisphere (LH) damage affect the processing of conversational implicatures, it remains to be discovered how the two hemispheres interact to process natural language pragmatics in the normal brain in real time.     

Partial body weight support treadmill training speed influences paretic and non-paretic leg muscle activation,stride characteristics,and ratings of perceived exertion during acute stroke rehabilitation

BackgroundIntensive task-specific training is promoted as one approach for facilitating neural plastic brain changes and associated motor behavior gains following neurologic injury. Partial body weight support treadmill training (PBWSTT), is one task-specific approach frequently used to improve walking during the acute period of stroke recovery (<1 month post infarct). However, only limited data have been published regarding the relationship between training parameters and physiologic demands during this early recovery phase.ObjectiveTo examine the impact of four walking speeds on stride characteristics, lower extremity muscle demands (both paretic and non-paretic), Borg ratings of perceived exertion (RPE), and blood pressure.DesignA prospective, repeated measures design was used.MethodsTen inpatients post unilateral stroke participated. Following three familiarization sessions, participants engaged in PBWSTT at four predetermined speeds (0.5, 1.0, 1.5 and 2.0 mph) while bilateral electromyographic and stride characteristic data were recorded. RPE was evaluated immediately following each trial.ResultsStride length, cadence, and paretic single limb support increased with faster walking speeds (p ⩽ 0.001), while non-paretic single limb support remained nearly constant. Faster walking resulted in greater peak and mean muscle activation in the paretic medial hamstrings, vastus lateralis and medial gastrocnemius, and non-paretic medial gastrocnemius (p ⩽ 0.001). RPE also was greatest at the fastest compared to two slowest speeds (p < 0.05).ConclusionsDuring the acute phase of stroke recovery, PBWSTT at the fastest speed (2.0 mph) promoted practice of a more optimal gait pattern with greater intensity of effort as evidenced by the longer stride length, increased between-limb symmetry, greater muscle activation, and higher RPE compared to training at the slowest speeds.     

Hydrogen-assisted damage in austenite/martensite dual-phase steel

For understanding the underlying hydrogen embrittlement mechanism in transformation-induced plasticity steels, the process of damage evolution in a model austenite/martensite dual-phase microstructure following hydrogenation was investigated through multi-scale electron channelling contrast imaging and in situ optical microscopy. Localized diffusible hydrogen in martensite causes cracking through two mechanisms: (1) interaction between {1?1?0}_M localized slip and {1?1?2}_M twin and (2) cracking of martensite–martensite grain interfaces. The former resulted in nanovoids along the {1?1?2}_M twin. The coalescence of the nanovoids generated plate-like microvoids. The latter caused shear localization on the specific plane where the crack along the martensite/martensite boundary exists, which led to additional martensite/martensite boundary cracking.     

Cascade effects on the irradiation stability of amorphous SiOC

We studied the heavy ion radiation tolerance of amorphous silicon oxycarbide (SiOC) alloys by in situ Kr ion irradiation within a transmission electron microscopy. The amorphous SiOC thin films were grown via co-sputtering from SiO₂ and SiC targets on a surface-oxidized Si (100) substrate. These films were irradiated by 1 MeV Kr ions at both room temperature and 300 °C with damage levels up to 5 displacements per atom (dpa). TEM characterization shows no sign of crystallization, void formation or segregation in all irradiated samples. Our findings suggest that SiOC alloys are a class of promising radiation tolerant materials.