Avoidance of obstacles in the absence of visual awareness

The spatial character of our reaching movements is extremely sensitive to potential obstacles in the workspace. We recently found that this sensitivity was retained by most patients with left visual neglect when reaching between two objects, despite the fact that they tended to ignore the leftward object when asked to bisect the space between them. This raises the possibility that obstacle avoidance does not require a conscious awareness of the obstacle avoided. We have now tested this hypothesis in a patient with visual extinction following right temporoparietal damage. Extinction is an attentional disorder in which patients fail to report stimuli on the side of space opposite a brain lesion under conditions of bilateral stimulation. Our patient avoided obstacles during reaching, to exactly the same degree, regardless of whether he was able to report their presence. This implicit processing of object location, which may depend on spared superior parietal-lobe pathways, demonstrates that conscious awareness is not necessary for normal obstacle avoidance.

Preserved obstacle avoidance during reaching in patients with left visual neglect

We asked 12 patients with left visual neglect to bisect the gap between two cylinders or to reach rapidly between them to a more distal target zone. Both tasks demanded a motor response but these responses were quite different in nature. The bisection response was a communicative act whereby the patient indicated the perceived midpoint. The reaching task carried no imperative to bisect the gap, only to maintain a safe distance from either cylinder while steering to the target zone. Optimal performance on either task could only be achieved by reference to the location of both cylinders. Our analysis focused upon the relative influence of the left and right cylinders on the lateral location of the response. In the bisection task, all neglect patients showed qualitatively the same asymmetry, with the left cylinder exerting less influence than the right. In the reaching task, the neglect group behaved like normal subjects, being influenced approximately equally by the two cylinders. This was true for all bar two of the patients, who showed clear neglect in both tasks. We conclude that the visuomotor processing underlying obstacle avoidance during reaching is preserved in most patients with left visual neglect. (C) 2004 Elsevier Ltd. All rights reserved.

Bait avoidance and habitat use by the roof rat, Rattus rattus, in a piggery

The acceptance of four anticoagulant rodenticide baits was evaluated in a piggery. The bait bases were cracked wheat, wax block, pig feed, and Racumin Paste(R). Mean daily consumption of each bait was poor (< 5 g). Mean activity index measured with tracking plates did not change significantly throughout pre-baiting (3 days), baiting (37) or post-baiting (7), indicating that the baits had no impact on the population. The same baiting regime applied simultaneously in nearby stables with lower feed availability induced a significantly higher mean consumption of the cracked wheat based bait, and the activity index declined to zero at day 23, indicating that the rats were eradicated. The failure of the baits to control rats in the piggery was possibly due to the poor bait acceptance caused by the abundant feed supply. Results of live-trapping and radio- and spool-and-line tracking indicated that the population was confined within the piggery; lower windowsills were the most used above-ground structure for movements; and minimum home range span was 17 m. We suggest that rodent control should be implemented within the confines of the piggery to reduce the risk to non-target animals, and that mortality agents should be placed less than or equal to 17 in apart arboreally for the roof rat. (C) 2004 Elsevier Ltd. All rights reserved.

The appetitive motivation scale and other BAS measures in the prediction of Approach and Active Avoidance

The Appetitive Motivation Scale (Jackson & Smillie, 2004) is a new trait conceptualisation of Gray's (I 970 199 1) Behavioural Activation System. In this experiment we explore relationships that the Appetitive Motivation Scale and other measures of Gray's model have with Approach and Active Avoidance responses. Using a sample of 144 undergraduate students, both Appetitive Motivation and Sensitivity to Reward (from the Sensitivity to Punishment and Sensitivity to Reward Questionnaire, SPSRQ; Torrubia, Avila, Molto, & Ceseras, 2001), were found to be significant predictors of Approach and Active Avoidance response latency. This confirms previous experimental validations of the SPSRQ (e.g., Avila, 2001) and provides the first experimental evidence for the validity of the Appetitive Motivation scale. Consistent with interactive views of Gray's model (e.g., Corr, 2001), high SPSRQ Sensitivity to Punishment diminished the relationship between Sensitivity to Reward and our BAS criteria. Measures of BIS did not however interact in this way with the appetitive motivation scale. A surprising result was the failure for any of Carver and White's (1994) BAS scales to correlate with RST criteria. Implications of these findings and potential future directions are discussed. (C) 2004 Elsevier Ltd. All rights reserved.

The role of avoidance coping in the disclosure of trauma

Little research has been undertaken to examine the empirical basis of commonly applied methods of posttrauma intervention. We propose that Pennebaker's work on structured disclosure of trauma provides a suitable analogue to explore questions of interest. The present study asks whether avoidance coping is likely to interfere with abbreviated disclosure of traumatic experiences. Subjects were 118 college students randomly allocated to either a one-session or four-session written trauma-disclosure condition. At 2 months postdisclosure, subjects with high avoidance coping within the one-session condition exhibited significantly more trauma-specific and physical symptoms than all other subjects. Avoidance coping significantly predicted trauma-specific symptoms at 2 months. These findings suggest that single session traumatic disclosure may not be useful for individuals with an avoidance style of coping.

Photoregulation and photodamage in Schefflera arboricola leaves adapted to different light environments

Leaves of the subtropical understorey shrub Schefflera arboricola Hayata growing in full sunlight had higher specific leaf weight, higher chlorophyll a/b ratios, lower total chlorophyll content and a threefold higher xanthophyll cycle pigment content than leaves growing in a naturally shaded, but sunfleck-punctuated, environment. A number of measurements, all made in situ and during natural day/night cycles, were taken as follows: current photochemical capacity (F-v/F-m after 10 min dark-adaptation), size and epoxidation state of the xanthophyll cycle, CO2 gas exchange and determination of the D1 synthesis rate. In sun leaves the lowest daily F-v/F-m was found to be approximately 0.6, the change from maximum correlating with an increase in zeaxanthin. Daily changes in zeaxanthin were partly due to de novo synthesis and turnover. We suggest that sun leaves can dissipate most of the excess light energy absorbed safely via the photoprotective xanthophyll cycle. D1 synthesis rates did not correlate with photosynthetic photon flux density or F-v/F-m. The shade leaves had high F-v/F-m values and constant photosynthetic rates throughout the day except during sunflecks, when photosynthetic rates increased and D1 synthesis accelerated, all without a substantial decrease in F-v/F-m. It seems that leaves of S. arboricola adapted to natural shade conditions can use sunflecks to contribute significantly to their productivity. The third leaf type investigated was from greenhouse-grown plants of S. arboricola after exposure to full sunlight. These leaves showed a rapid and large reduction in F-v/F-m (to 0.3), which neither correlated with zeaxanthin formation nor recovered within the same day. From long-term effects following full sunlight exposure of greenhouse-grown plants we suggest that this F-v/F-m reduction actually reflects photodestruction.

Do simple prudent health behaviours protect men from myocardial infarction?

Background We tested whether behaviours such as discarding obvious fat on meat, cessation of smoking, avoidance of passive smoking, habitual use of reduced fat milk, prudent consumption of alcohol and regular but moderate physical exercise are associated with a reduction of cardiovascular risk. Methods This was a population-based case-control study done in Perth, Western Australia. The cases (n = 336) were men aged 27-64 years with a first-ever acute myocardial infarction (AMI) during the period 1992-1993, and who survived at least 28 days. The controls (n = 735) were participants in a population-based survey of cardiovascular risk factors conducted during May-November 1994. Both groups completed the same questionnaire and the data were analysed with multiple logistic regression using backward elimination technique. Results Among men aged 27-64 years simple measures such as participation in non-vigorous exercise (odds ratio [OR] = 0.5, 95% CI : 0.4-0.7), and avoidance of added salt (OR = 0.6, 95% CI : 0.4-0.9) are associated with significant and Important protection from AMI. Conclusion After 25 years of falling mortality in Australia, lifestyles can still be significantly improved to reduce heart disease even further.