Visual Working Memory Impairment In Schizophrenia

Visual working memory deficit is considered a core symptom of schizophrenia,however,much less is known about the causes of their visual working memory impairment.One possible explanation is the distraction inhibition hypothesis:the failure in inhibiting task-irrelevant information may be responsible for the lessened visual working memory in schizophrenia.On the other hand,the hyperfocusing hypothesis believes that people with schizophrenia tend to focus their limited cognitive resources more narrowly but more intensely and unable to divided resources to multiple objects.The aim of the present study is to adjudicate between these two accounts and explore the possible neural mechanism underlying the deficits.In experiment 1,two distractors were added to color wheel paradigm in both 1 target and 3 targets conditions.The behavior results of 51 patients and 60 healthy control subjects suggested that patients did not show more distracting effects.Thus,the present study proposed that the distraction inhibition ability may not be the causal of visual working memory impairment in schizophrenia.In experiment 2,the target number is fixed at 3 and patients need to respond to the color of 3 targets.According to different reaction order,the present study put forward the autonomic and random response tasks.The autonomic response task requires subjects to preferentially respond to the color that they remember best,and under this condition patients tend to focus their visual working memory resources on just one target.In experiment 3,in order to understand the neural mechanism underlying the hyperfocusing tendency in schizophrenia,we utilized exogenous and endogenous cues to isolate the bottom-up and top-down attentional pathways,together with electroencephalography(EEG)recording.The results suggested patients cannot make use of endogenous cue,and there is no ADAN and PCN induced by endogenous cue in frontal lobe and parietal-occipital lobe electrodes,which implies the top-down pathway is damaged in schizophrenia.However,people with schizophrenia can effectively use the exogenous cue,and the amplitude of PCN in parietal-occipital lobe electrodes is significantly larger than healthy subjects,which shows the over-reliance on bottom-up pathway in schizophrenia.Taken together,the present study found that the cause of visual working memory impairment in schizophrenia is not due to their disability to inhibit distraction,but because of their tendency of hyper-focus.For the neural mechanisms,schizophrenia patients’ hyperfocusing tendency may be related to their deficit in top-down attention control and over-reliance on bottom-up pathway.