Cortical hyperactivation at low working memory load: A primary processing abnormality in people with schizophrenia?

Area of Science:

• Neuroscience
• Cognitive Psychology
• Psychiatry

Background:

• People with schizophrenia (PSZ) often exhibit task-induced brain hyperactivation compared to healthy controls (HCS) during low working memory (WM) load.
• This hyperactivation is typically attributed to cognitive deficits making simple tasks more resource-intensive.

Purpose of the Study:

• To investigate whether the observed hyperactivation in PSZ during low WM load is a secondary consequence of cognitive impairment.
• To test the hyperfocusing hypothesis as an alternative explanation for cognitive differences in schizophrenia.

Main Methods:

• Re-analysis of functional MRI data from PSZ and HCS performing a WM task.
• Subgroup analysis matching participants based on WM capacity (K), WM capacity estimates, or attentional lapse rates.
• Comparison of brain activation (BOLD signal) and task performance across varying WM loads (1-7 items).

Main Results:

• In performance-matched subgroups, PSZ and HCS showed similar performance across all set sizes.
• While BOLD activation did not differ at high WM loads, PSZ consistently hyperactivated the left posterior parietal cortex (PPC) when maintaining a single item.
• This pattern persisted in subgroups matched for WM capacity or attentional lapse rates.

Conclusions:

• The findings suggest that hyperactivation in PSZ during low WM load is not secondary to cognitive impairment.
• The results support the hyperfocusing hypothesis, proposing that an abnormally narrow and intense focus of processing resources is central to schizophrenia-related cognitive impairments.