The truth about cognitive impairment in functional motor symptoms: An experimental deception study with the Guilty...

A century ago, Janet was the first to conceptualize conversion reactions as having a neurocognitive component, as disorders of memory processing that arise in the wake of trauma. The available evidence suggests that this impairment might arise from dysfunction in the fronto-subcortical circuits. Our aim was to examine the cognitive functions regulating deception in patients with functional motor symptoms (FMS), using a computerised task, the Guilty Knowledge Task (GKT). We also tested a group of healthy subjects (HS) as a control group.

Thirteen patients affected by FMS and 14 HS underwent a modified version of the GKT, a computer-controlled procedure used to detect truthful and deceptive responses. All participants were also screened for depression, anxiety, alexithymia and for moral sense (moral judgment task).

The reaction times (RTs) were significantly longer for lie responses than for true responses (F(1,26) = 50.47; p < 0.001) in the two groups. Total RTs were significantly longer for patients with FMS than for HS, in true responses (F(1,25) = 4,36; p = 0.047) and lie responses (F(1,25) = 4.26; p = 0.05). No differences were found between the two groups for accuracy in producing true responses (F(1,25) = 0.09, p = 0.77), and lie responses (F(1,25) = 0,12, p = 0.73.

When tested with the GKT, patients with FMS were slower than HS in producing truthful and lying responses. Current knowledge along with our new findings in patients with FMS - possibly arising from individually unrecognised extremely mild, cognitive difficulties - should help in designing specific rehabilitative programmes to improve cognitive and behavioural disturbances in these patients.