class=""h4"">Background
Auditory verbal hallu
cinations (AVH) are one of the most prominent symptoms of s
chizophrenia but have also been reported in the general population. Several
cognitive models have tried to elu
cidate the me
chanism behind auditory verbal hallu
cinations, among whi
ch a top-down model. A
ccording to this model, per
ception is biased towards top-down information (e.g., expe
ctations), redu
cing the influen
ce of bottom-up information
coming from the sense organs. This bias predisposes to false per
ceptions, i.e., hallu
cinations.
class=""h4"">Methods
The current study investigated this hypothesis in non-psychotic individuals with frequent AVH, psychotic patients with AVH and healthy control subjects by applying a semantic top-down task. In this task, top-down processes are manipulated through the semantic context of a sentence. In addition, the association between hallucination proneness and semantic top-down errors was investigated.
class=""h4"">Results
Non-psychotic individuals with AVH made significantly more top-down errors compared to healthy controls, while overall accuracy was similar. The number of top-down errors, corrected for overall accuracy, in the patient group was in between those of the other two groups and did not differ significantly from either the non-psychotic individuals with AVH or the healthy controls. The severity of hallucination proneness correlated with the number of top-down errors.
class=""h4"">Discussion
These findings confirm that non-psychotic individuals with AVH are stronger influenced by top-down processing (i.e., perceptual expectations) than healthy controls. In contrast, our data suggest that in psychotic patients semantic expectations do not play a role in the etiology of AVH. This finding may point towards different cognitive mechanisms for pathological and nonpathological hallucinations.
