Short-term memory errors are strongly associated with a drift in neural activity in the posterior parietal cortex

Understanding the neural mechanisms behind short-term memory (STM) errors is crucial for unraveling cognitive processes and addressing related deficits in neuropsychiatric disorders. This study investigates whether STM errors result from misrepresentation of sensory information or a decay in these representations over time. Utilizing 2-photon calcium imaging in the posterior parietal cortex (PPC) of mice engaged in a delayed match-to-sample task, we identified a subset of PPC neurons exhibiting both directional and temporal selectivity. Contrary to the idea that STM errors primarily stem from mis-encoding during the sample phase, our findings indicate that these errors are more closely associated with a drift in neural activity during the delay period. This drift results in a gradual shift away from the correct representation, ultimately leading to incorrect behavioral responses. These results emphasize the importance of maintaining stable neural representations in the PPC for accurate STM. Our findings also suggest that targeting PPC activity stabilization during delay periods could be a potential therapeutic strategy for mitigating cognitive impairments in disorders like schizophrenia.