Recall (memory) - Neuroanatomy

Neuroanatomy

The anterior cingulate cortex, globus pallidus, thalamus, and cerebellum show higher activation during recall than during recognition which suggests that these components of the cerebello-frontal pathway play a role in recall processes that they do not in recognition. Although recall and recognition are considered separate processes, it should be noted that they are both most likely constitute components of distributed networks of brain regions.

According to neuroimaging data, PET studies on recall and recognition have consistently found increases in regional cerebral blood flow (RCBF) in the following six brain regions: (1) the prefrontal cortex, particularly on the right hemisphere; (2) the hippocampal and parahippocampal regions of the medial temporal lobe; (3) the anterior cingulate cortex; (4) the posterior midline area that includes posterior cingulate, retrosplenial (see retrosplenial region), precuneus, and cuneus regions; (5) the inferior parietal cortex, especially on the right hemisphere; and (6) the cerebellum, particularly on the left.

The specific role of each of the six main regions in episodic retrieval is still unclear, but some ideas have been suggested. The right prefrontal cortex has been related to retrieval attempt; the medial temporal lobes to conscious recollection; the anterior cingulate to response selection; the posterior midline region to imagery; the inferior parietal to awareness of space; and the cerebellum to self-initiated retrieval .

In recent research, a group of subjects was faced with remembering a list of items and then measured when trying to recall said items. The evoked potentials and hemodynamic activity measured during encoding were found to exhibit reliable differences between subsequently recalled and not recalled items. This effect has been termed the subsequent memory effect (SME). This difference in these specific brain regions determines whether or not a item is recalled. A study by Fernandez et al. has shown that the differences that predict recall appear both as a negative deflection in the rhinal cortex of an event-related potential (ERP) 400 ms after stimulus exposure, and as a positive hippocampal ERP beginning 800 ms after stimulus onset. This means that recall only occurs if these two brain regions (rhinal cortex and hippocampus) are activated in synchrony.