[DISSOCIATION BETWEEN DECLERATIVE AND PROCEDURAL MEMORY IN PATIENTS WITH TRAUMATIC BRAIN INJURY]

Converging evidence from studies of patients suffering focal brain lesions and results from animal models led to the notion of two functionally and structurally distinct memory systems, declarative-explicit-episodic and procedural-implicit-skill.

Assessment of skill acquisition and procedural memory in patients after blunt traumatic brain injury (TBI) who suffer from deficit of explicit (episodic) memory in comparison to patients without such a deficit.

Comparison of skill acquisition in the Finger Opposition Sequence task in two patients after TBI presenting with episodic-explicit memory deficit to eight patients without such a deficit.

Both subjects demonstrated severe declarative-episodic memory deficits as demonstrated in the Rivermead Behavioural Memory Test (RBMT) but showed robust learning and retention of skill in practicing a finger movement sequence, improving performance speed with no speed-accuracy trade-off. The practice related gains in performance and their retention in a one-month follow-up test were as robust as in patients without explicit memory deficit.

The results coincide with previous case reports demonstrating a dissociation between procedural-implicit and declarative-explicit memory systems. The evaluation of the two memory systems may contribute to patient rehabilitation as a residual functioning of one system can be used to compensate for deficit of the other, in order to improve daily functioning.