Rehabilitation of endogenous task shift processes in closed head injury patients

This paper reports a study that was aimed to rehabilitate executive functions in CHI patients. When a subject is engaged in two speeded tasks, not simultaneously but with some form of alternation, the response is slower to an item of task A if it was preceded by an item of task B, than when it was preceded by an item of task A. This shift cost is small when subjects can prepare in advance for the new task (endogenous task shift), whereas the cost is much greater when preparation is not possible (exogenous task shift). The groups tested comprised 20 severe closed head injury (CHI) patients (10 who underwent treatment and 10 controls), 8 mild CHI patients, and 18 non-brain damaged (NBD) controls. In the present study, the shift cost was greater for severe CHI patients than for NBD controls. Treatment consisted of five sessions, in which an endogenous task shift paradigm was used. A significant reduction of the endogenous shift cost from assessment to retest was found. The reduction remained stable at the 4-month follow-up session. These results are not simply due to retesting, as the control patients did not show any improvement at retest. Interestingly, no reduction of exogenous task shift cost was found. The results showed also that the beneficial effect of the treatment generalises to other executive functions.