The experience of virtual reality: are individual differences in mental imagery associated with sense of presence?

The concept of "presence" describes the quality of subjective experience in immersive virtual reality (IVR). Presence refers to a specific state of consciousness: we behave and feel as if we actually were in the virtual world even though we know there is nothing there. In their handbook of Virtual Reality, Burdea and Coiffet (Virtual reality technology, Wiley, New York, 2003) suggested that the experience of presence in IVR would emerge from the combination of three Is: Immersion or capacity to isolate from the external world, Interaction or capacity to naturally exploring the virtual environment, and Imagination or individual aptitudes with mental imagery. So far, several studies have investigated the technological and psychological factors affecting the degree of immersion and interaction. However, no study has explored the relationship between perceived presence and mental imagery. Here we aim at filling this gap through a correlational study comparing self-reports about sense of presence and mental imagery abilities. After experiencing two IVR scenarios (an art gallery and a living room), 142 male and female users were administered with questionnaires assessing the degree of presence (Igroup Presence Questionnaire), the degree of vividness (Vividness of Visual Imagery Questionnaire) and control (Test of Visual Imagery Control) of subjective mental images. Results showed a clear positive correlation between presence and vividness: the higher the vividness of mental images the stronger the reported sense of presence felt in IVR scenarios. Instead, the capacity to control mental imagery showed a weaker association with presence. We may conclude that individual differences in the degree of perceived presence and mental imagery ability are associated.

Early detection of nephrotoxic effects in thalassemic patients receiving desferrioxamine therapy.

Nineteen transfusion-dependent beta-thalassemia major patients were included in the study. Six of these patients underwent chelation therapy with desferrioxamine by subcutaneous infusion (50 mg/kg/12 hr) and 13 received intravenous infusion (50 mg/kg/6 hr or 100 mg/kg/24 hr). BUN, creatinine, creatinine clearance, beta 2-microglobulin, urinary beta 2-microglobulin and urinary growth hormone excretion were evaluated during desferrioxamine treatment. Thirteen out of nineteen patients presented tubular damage indicated by increased excretion of urinary beta 2-microglobulin. 85% (11 of 13) of these patients showed more serious tubular damage, as demonstrated by concurrent increased urinary growth hormone excretion. Moreover, a positive correlation between urinary growth hormone excretion and urinary beta 2-microglobulin was observed (P < 0.05).

Acute renal failure occurring during intravenous desferrioxamine therapy: recovery after haemodialysis.

A patient with transfusion-dependent thalassemia was undergoing home intravenous desferrioxamine (DFX) treatment by means of a totally implanted system because of his poor compliance with the nightly subcutaneous therapy. Due to an accidental malfunctioning of the infusion pump, the patient was inadvertently administered a toxic dosage of the drug which caused renal insufficiency. Given the progressive deterioration of the symptoms and of the laboratory values, despite adequate medical treatment, a decision was made to introduce haemodialytical therapy in order to remove the drug and therapy reduce the nephrotoxicity. From the results obtained, haemodialysis can therefore be suggested as a useful therapy in rare cases of progressive acute renal failure caused by desferrioxamine.