Effect of heat wave on N2 fixation and N remobilisation of lentil (Lens culinaris MEDIK) grown under free air CO2 enrichment in a mediterranean-type environment

The stimulatory effect of elevated [CO₂ ] (e[CO₂ ]) on crop production in future climates is likely to be cancelled out by predicted increases in average temperatures. This effect may become stronger through more frequent and severe heat waves, which are predicted to increase in most climate change scenarios. Whilst the growth and yield response of some legumes grown under the interactive effect of e[CO₂ ] and heat waves has been studied, little is known about how N₂ fixation and overall N metabolism is affected by this combination. To address these knowledge gaps, two lentil genotypes were grown under ambient [CO₂ ] (a[CO₂ ], ~400 µmol·mol^-1 ) and e[CO₂ ] (~550 µmol·mol^-1 ) in the Australian Grains Free Air CO₂ Enrichment facility and exposed to a simulated heat wave (3-day periods of high temperatures ~40 °C) at flat pod stage. Nodulation and concentrations of water-soluble carbohydrates (WSC), total free amino acids, N and N₂ fixation were assessed following the imposition of the heat wave until crop maturity. Elevated [CO₂ ] stimulated N₂ fixation so that total N₂ fixation in e[CO₂ ]-grown plants was always higher than in a[CO₂ ], non-stressed control plants. Heat wave triggered a significant decrease in active nodules and WSC concentrations, but e[CO₂ ] had the opposite effect. Leaf N remobilization and grain N improved under interaction of e[CO₂ ] and heat wave. These results suggested that larger WSC pools and nodulation under e[CO₂ ] can support post-heat wave recovery of N₂ fixation. Elevated [CO₂ ]-induced accelerated leaf N remobilisation might contribute to restore grain N concentration following a heat wave.

Rehabilitation of frontal/executive impairments in schizophrenia

OBJECTIVE

A relatively high prevalence of deficits in cognitive flexibility, working memory and planning ability has been reported in schizophrenia patients. The objective was to develop a rehabilitation training program in an attempt to improve these specific cognitive functions.

METHODS

The deficits in cognitive flexibility, working memory and planning ability were interpreted as reflecting executive cognitive processing impairments secondary to prefrontal neural system dysfunction. Following the 'process specific' approach, it was considered important to develop tasks that hypothesised the exercise of these cognitive abilities and the more molecular information processes thought to be fundamental to these abilities. Care was taken to ensure that all tasks involved the practice of processes thought to activate frontal/prefrontal neural systems. Attentional, visual, verbal, conceptual, motor and fine motor tasks were considered important for each process area in order to involve as many functional modalities as possible.

RESULTS

A program comprising cognitive shift, working memory and planning modules was developed. Conducted over 11 weeks, four modules were of 2 weeks' duration, and the fifth of 3 weeks' duration. Four individual 1 hour training sessions were conducted each week. Core elements of the modules are described.

CONCLUSION

Consisting predominantly of pencil and paper information processing exercises, all of the training exercises are presented in the volumes of the Frontal/Executive Program. The program appears to be user-friendly with therapists now successfully delivering the program, in its entirety, to schizophrenia patients. Should future studies replicate preliminary findings of improved neurocognitive performance following training with the program, such findings would have important implications for the treatment of schizophrenia.

Frontal/executive impairments in schizophrenia

A study of frontal/executive impairments in schizophrenia is reported. Schizophrenia patients and controls were not significantly different with respect to age, sex, and premorbid IQ. The schizophrenia group demonstrated significant impairments in cognitive flexibility and forward planning, replicating results from a 1990 study by Morice. Impairment prevalence figures of 65 and 76 percent for cognitive flexibility and forward planning, respectively, were demonstrated. Several tests for short-term memory were administered. Schizophrenia patients were not found to be impaired on tests of simple, or primary, short-term memory as measured by Digits Span Forward and Words Span Forward, but they were found to be significantly impaired compared with controls on two tests of working memory, Alphabet Span and Sentence Span. Using a cutoff derived from the mean score for the controls, 65 percent of schizophrenia patients proved to be impaired on Sentence Span. A total of 16 (94%) were impaired on one or more of the three tests of executive functioning used. The effects of IQ on test results were examined, and impairment of cognitive flexibility and forward planning seemed to occur regardless of whether premorbid IQ had been preserved or had deteriorated. However, working memory impairments occurred in the subgroup of schizophrenia patients demonstrating a substantial fall in IQ from premorbid levels. The ability to process increasingly complex information was addressed by a more detailed examination of the Tower of London results. There were no differences in performance between groups for the first three levels of complexity (1-3 moves), but significant, and increasing, differences emerged for the last three levels (4-6 moves). These results were taken to support the hypothesis that schizophrenia represents a loss of, or a failure to acquire, the ability to process complex information. Impairments of executive functions that could affect complex information processing could have implications for schizophrenia rehabilitation.

Specific cognitive flexibility rehabilitation in schizophrenia

A Cognitive Shift neurocognitive training module was developed in the attempt to ameliorate cognitive flexibility deficits in chronic schizophrenic patients. A procedural training approach hypothesized the exercise of specific neural network processes, identified from theories of frontal and prefrontal lobe functioning. Three male patients who underwent the intensive program demonstrated significant gains in Wisconsin Card Sorting Test performance, gains that were maintained at a six month reassessment. Expanded Brief Psychiatric Rating Scale (a measure of symptomatology) and Life Skills Profile (a measure of daily functioning) measures showed smaller improvements. The ability to improve cognitive flexibility could have important implications for the treatment of schizophrenia.