Rehabilitation of divided attention after severe traumatic brain injury: a randomised trial.

Patients with severe traumatic brain injury (TBI) frequently suffer from a difficulty in dealing with two tasks simultaneously. However, there has been little research on the rehabilitation of divided attention. The objective of the present study was to assess the effectiveness of a rehabilitation programme for divided attention after severe TBI. Twelve patients at a subacute/chronic stage after a severe TBI were included. A randomised AB vs. BA cross-over design was used. Training lasted six weeks, with four one-hour sessions per week. It was compared to a non-specific (control) cognitive training. During experimental treatment, patients were trained to perform two concurrent tasks simultaneously. Each one of the two tasks was first trained as a single task, then both tasks were given simultaneously. A progressive hierarchical order of difficulty was used, by progressively increasing task difficulty following each patient's individual improvement. Patients were randomised in two groups: one starting with dual-task training, the other with control training. Outcome measures included target dual-task measures, executive and working memory tasks, non-target tasks, and the Rating Scale of Attentional Behaviour addressing attentional problems in everyday life. Assessment was not blind to treatment condition. A significant training-related effect was found on dual-task measures and on the divided attention item of the Rating Scale of Attentional Behaviour. There was only little effect on executive measures, and no significant effect on non-target measures. These results suggest that training had specific effects on divided attention and helped patients to deal more rapidly and more accurately with dual-task situations.

Relationships between time estimation, memory, attention, and processing speed in patients with severe traumatic brain injury.

The present experiment was aimed at investigating the effects of memory and attention deficits and of information processing slowing on time estimation in patients with severe traumatic brain injury (TBI). Patients with TBI and normal control subjects reproduced and produced durations (5, 14, 38s) in both a control counting condition and in a concurrent reading condition. They also performed finger-tapping tasks at a free rate and at a 1s rate. Both groups were assessed on processing speed using a reaction-time task, and on memory and attention using a battery of neuropsychological tests. The results showed that time estimation was not less accurate in patients with TBI than in control subjects on the reproduction task or on the production task performed either in the control counting condition or in the concurrent reading condition. Conversely, duration judgments were more variable in patients with TBI than in control subjects on both tasks in both conditions. The results also showed that TBI patients exhibited slower reaction-times, and poorer working and episodic memory scores than control subjects. Most importantly, the variability index in the duration reproduction task was related to both working memory scores and processing speed measures, whereas the variability index in the duration production task was only related with the processing speed measures. The temporal performance pattern in TBI patients does not appear to reflect specific deficits in timing, but rather overall problems in attention, working memory, and processing speed mechanisms.

Divided attention and mental effort after severe traumatic brain injury.

The aim of this study was to assess dual-task performance in TBI patients, under different experimental conditions, with or without explicit emphasis on one of two tasks. Results were compared with measurement of the subjective mental effort required to perform each task. Forty-three severe TBI patients at the subacute or chronic phase performed two tasks under single- and dual-task conditions: (a) random generation; (b) visual go-no go reaction time task. Three dual-task conditions were given, requiring either to consider both tasks as equally important or to focus preferentially on one of them. Patients were compared to matched controls. Subjective mental effort was rated on a visual analogic scale. TBI patients showed a disproportionate increase in reaction time in the go-no go task under the dual-task condition. However, they were just as able as controls to adapt performance to the specific instructions about the task to be emphasised. Patients reported significantly higher subjective mental effort, but the variation of mental effort according to task condition was similar to that of controls. These results suggest that the divided attention deficit of TBI patients is related to a reduction in available processing resources rather than an impairment of strategic processes responsible for attentional allocation and switching. The higher level of subjective mental effort may explain why TBI patients frequently complain of mental fatigue, although this subjective complaint seems to be relatively independent of cognitive impairment.

Interactions between divided attention and working-memory load in patients with severe traumatic brain injury.

The aim of this study was to assess the relationships between divided-attention deficits and working-memory limitations after severe traumatic brain injury (TBI). Severe TBI patients (n = 43) and controls were given a n-back task of three different load levels, which was performed as a single and a dual task. Patients demonstrated, as expected, a difficulty in dual-task processing and an increased susceptibility to high working-memory load, but dual-task performance and working-memory load did not interact as expected. These results are in accordance with recent findings suggesting that dual-task performance and other working-memory functions represent dissociable although interrelated abilities.