P300 amplitude is insensitive to working memory load in schizophrenia

Area of Science:

• Neuroscience
• Cognitive Psychology
• Psychiatry

Background:

• Working memory (WM) tasks typically show a P300 event-related potential (ERP) component that decreases with higher WM load.
• This load-dependent P300 amplitude modulation has not been previously investigated in individuals with schizophrenia (SZs).
• SZs are characterized by impaired WM capacity and aberrant brain connectivity.

Purpose of the Study:

• To investigate the relationship between P300 amplitude and WM load in individuals with schizophrenia.
• To compare P300 amplitude modulation during a WM task between SZ patients and healthy controls.

Main Methods:

• Utilized an 80-channel electroencephalogram (EEG) to record brain activity in 13 SZ patients and 13 matched healthy controls.
• Subjects performed an N-back task, a standard paradigm for manipulating WM load.

Main Results:

• Healthy controls exhibited the highest P300 amplitude in low WM load conditions, decreasing with higher loads and attentional control conditions.
• SZ patients displayed consistently low P300 amplitudes across all WM load conditions.
• A significant difference in P300 amplitude was observed only at the lowest WM load (1-back), with SZs showing smaller amplitudes than controls.

Conclusions:

• Individuals with schizophrenia demonstrate reduced P300 amplitudes irrespective of WM load.
• The absence of P300 amplitude modulation by WM load in SZs supports the hypothesis of a generalized WM capacity deficit in this population.