Semantic memory retrieval circuit: Role of pre-SMA, caudate, and thalamus

► Pre-SMA–thalamic interactions mediate semantic retrieval of integrated object memory. ► Pre-SMA starts search via interactions with cortices of semantic memory subsystems. ► Initiation of this search is indexed by theta band EEG power. ► Beta-band increase at pre-SMA–thalamus–cortices marks search end and object retrieval. ► Activity within the circuit is modulated by the caudate nuclei. We propose that pre-supplementary motor area (pre-SMA)–thalamic interactions govern processes fundamental to semantic retrieval of an integrated object memory. At the onset of semantic retrieval, pre-SMA initiates electrical interactions between multiple cortical regions associated with semantic memory subsystems encodings as indexed by an increase in theta-band EEG power. This starts between 100–150ms after stimulus presentation and is sustained throughout the task. We posit that this activity represents initiation of the object memory search, which continues in searching for an object memory. When the correct memory is retrieved, there is a high beta-band EEG power increase, which reflects communication between pre-SMA and thalamus, designates the end of the search process and resultant in object retrieval from multiple semantic memory subsystems. This high beta signal is also detected in cortical regions. This circuit is modulated by the caudate nuclei to facilitate correct and suppress incorrect target memories.