What is the parietal lobe contribution to long-term memory?

Until relatively recently, the lateral parietal lobe (PL) was not considered an important region for long-term memory, typically associated instead with functions such as visuospatial attention and visually-guided reaching. Scientific interest in a possible link with episodic memory was fuelled by the realisation of an intriguing discrepancy between functional imaging studies of episodic memory retrieval, which showed consistent PL activation, and the seemingly unaffected memory performance in patients with PL lesions. Shallice and Cooper dedicated a section in their book The Organisation of Mind to this newly emerged topic, reflecting how it has rapidly become an established research focus in the cognitive neurosciences. Research into the role of PL regions in memory has grown following Wagner et al.’s (2005) review of the functional neuroimaging literature, which highlighted how PL responses, in particular on the left, are closely linked with episodic retrieval success. A number of studies have reported greater PL activation during recollection of contextual details than during familiarity-based recognition, both when items are separated based on participants’ introspective ratings (Henson et al., 1999), and when participants are asked to orient towards contextual details as opposed to item familiarity during retrieval (Dobbins et al., 2002). This retrieval success effect may relate to subjective aspects of recollection, as it has been observed for stimuli that participants subjectively consider to have been previously encountered but that are actually novel in the experimental context, a phenomenon known as “perceived oldness” (Wheeler and Buckner, 2003). Meta-analyses have confirmed the prevalence of parietal activity in the functional magnetic resonance imaging (fMRI) literature, with one analysis by Simons et al. (2008) identifying that PL regions may be more consistently activated during recollection (in around 90% of studies examined) than “core” episodic memory regions such as the medial temporal lobes