The frontal lobe is predictably divided from the temporal lobe by the central sulcus. However, the morphology of the central sulcus varies between subjects, due in part to handedness and aging. The frontal lobes have traditionally been associated with executive functions.
The prefrontal cortex is a part of the frontal lobe. Specifically, it contains the Brodmann areas #8, #9, #10 (possibly important to human evolution), #11, #44, #45, #46 (the DLPFC!), and #47 (involved in speech syntax).
The orbitalfrontal cortex (OFC) consists of Brodmann area #’s 10, 11, and 47. It has roles in coding reward value and predicting the expected reward value of an event. Specifically, lesions to the OFC tend to have the following effects:
1) Makes drug-related responses faster, more erratic, and less associated with learned (i.e., conditioned) cues. For example, Grakalic et al found that mice with OFC lesions began self-administering cocaine after fewer sessions and had higher steady states of drug responding.
2) Diminishes the ability to form associations between probabilistic stimuli and reward. For example, Rudebeck et al showed that in a stimulus–reinforcement experiment, the number of trials necessary for OFC-lesioned macaque monkeys to achieve the optimal response pattern was much slower than for control or ACC lesioned monkeys:
3) Decreases the ability to regulate emotional states. For example, Reekie et al studied marmoset monkeys with orbitalfrontal cortex (OFC) lesions and found that OFC lesions lead to longer autonomic arousal long after the conditioned stimulus and reinforcement has been removed, as measured by blood pressure:
The authors conclude that “…our immediate reactions to emotive stimuli are not always beneficial, and, therefore, an important element of emotion is the ability to appropriately adapt and rapidly modify emotional responses on a moment-by-moment basis. The contribution of the OFC to the regulation of positive emotional states is clearly demonstrated…”
These lesion studies paint the picture of an orbitalfrontal cortex intricately involved with expected reward and its relation to emotion.
Inspired by CalTech’s Question #14 for cognitive scientists: “”Anatomically, what are the frontal and pre-frontal cortical areas? What do you know about patients with lesions in the orbital-frontal cortex?”
Cykowski et al, 2008. The Central Sulcus: an Observer-Independent Characterization of Sulcal Landmarks and Depth Asymmetry. Cerebral Cortex doi:10.1093/cercor/bhm224
Reekie YL et al, 2008. Uncoupling of behavioral and autonomic responses after lesions of the primate orbitofrontal cortex. PNAS doi: 10.1073/pnas.0800417105
Grakalic I et al, 2010. Effects of orbitofrontal cortex lesions on cocaine self-administration. Neuroscience doi:10.1016/j.neuroscience.2009.10.051
Rudebeck PH et al, 2008. Frontal Cortex Subregions Play Distinct Roles in Choices between Actions and Stimuli. doi:10.1523/JNEUROSCI.3541-08.2008