Perceiving visual, auditory, or chemical sensations is the first step to sorting objects, events, or situations into categories. Seger and Miller (2010) discuss the importance of contrasting brain regions for this initial task. Specifically for processing visual sensations, early phases of category learning are dependent upon regions in the visual system for perceiving information and discerning between noteworthy characteristics. An area of the visual system believed to be important for analyzing perceptual stimuli is the Inferior Temporal Cortex (ITC) (Seger & Miller, 2010). It has been found to facilitate categorization by recognizing unique features of objects and responding according to perceptual differences between categories (DeGutis & D’Esposito 2007).
Beyond initial perceptual learning, categorization also involves the parietal and the prefrontal cortex (PFC) in order to successively learn and predict behavior and movement sequences. To illustrate the PFC involvement in categorization, Shima, Isoda, Mushiake, and Tanji (2007) measured prefrontal cell activity in monkeys learning to categorize different patterns of movement. They reported that prefrontal cells were activated when categorizing the sequences of learned behaviors. The cells increased in activity for executing and planning the motor responses within the patterns, but were mainly responsive for, and could accurately predict, the category associated with the sequence.
An area that is thought to be important for storing learned categories is the hippocampus and medial temporal lobe (MTL) (Seger & Miller, 2010).
Research has begun to focus on how each of the brain regions works together to learn, store, and retrieve categorical information (Ashby and Maddox, 2010). One major component in coordinating the contrasting brain regions appears to be the basal ganglia. Basal ganglia project to and receive input from several cortical areas, process the information, and provide feedback through the thalamus to the originating cortical areas. This output has been shown to guide behaviors and strengthen synaptic activity (Shohamy, Meyers, & Gluck, 2008). Research has been devoted to identifying the different circuits and mapping their exact pathways. Alexander, DeLong, and Strick (1986) proposed the presence of at least five circuits created from input and output from the basal ganglia. More recently, it has been posited that the circuits may be interconnected and, therefore, identifying separate pathways extensively is not necessary. To this point, Seger and Miller (2010) describe four feedback loops, which project information to and from several cortical regions. These loops are the visual loop, executive loop, motivational loop, and the motor loop. The brain has been shown to recruit the different circuits depending on the activity being formed. Activation within the circuits has further been found to shift depending on the demands of the present task (cite?).