Comprehensive Brodmann Area Guide

Brodmann areas are a historically important division of the cerebral cortex into distinct regions based on their cytoarchitecture or neuronal arrangement and connections. The concept of Brodmann areas was introduced by the German neurologist Korbinian Brodmann in the early 20th century (Brodmann, 1909). Brodmann's work has significantly impacted the understanding of the functional organization of the cortex and remains influential in contemporary neuroscience research.

Brodmann's classification was based on his observations of differences in the cellular organization of the cortex across various mammalian species, including humans. He identified 43 numbered areas in the human brain by examining the cellular organization, cell types, and layer thickness (Zilles & Amunts, 2010). Although some refinements have been made since Brodmann's initial classification, many identified areas retain their original numbering.

The Importance of Brodmann Areas

The identification of Brodmann areas has facilitated the investigation of functional specialization within the cortex. Most cortical functions involve the networked activity of multiple Brodmann areas. Several Brodmann areas are now associated with specific functions, such as primary sensory and motor areas, as well as higher cognitive functions like language processing and decision-making (Glasser et al., 2016). For instance, Brodmann area 4 corresponds to the primary motor cortex, area 17 to the primary visual cortex, and areas 44 and 45 to Broca's area, which is crucial for speech production.

While Brodmann areas provide a valuable framework for understanding cortical organization, they do not capture the full complexity of the brain's functional architecture. Advances in neuroimaging techniques have identified additional areas and functional networks, highlighting the intricate organization of the cortex beyond Brodmann's classification (Glasser et al., 2016).

Researchers have revised the Brodmann maps and correlated areas with their functions. The Brodmann maps below were contributed by Mark Dow, Research Assistant at the Brain Development Lab at the University of Oregon, to Wikimedia Commons.

Areas 3, 1, and 2: Primary Somatosensory Cortex (S1)

The primary somatosensory cortex (S1) is a critical region for processing somatosensory information in the brain. It is involved in processing touch, proprioception, and temperature. These four cortical areas contain separate somatotopic maps (Purves, 2018). Graphic © Big8/Shutterstock.com.

Brodmann areas

The S1 is located in the postcentral gyrus, mainly in Brodmann areas 3, 1, and 2. These areas have distinct functions; Brodmann area 3 receives and processes cutaneous and proprioceptive inputs, area 1 processes tactile stimuli, and area 2 integrates proprioceptive and tactile inputs (Kaas, 2008). Location

The S1 is located in the parietal lobe, immediately posterior to the central sulcus. It is bordered by the primary motor cortex (M1) anteriorly and the secondary somatosensory cortex (S2) posteriorly. The closest sites are C3 and C4, which overlie the central sulcus (Jasper, 1958).

Connections

The S1 strongly connects with other cortical and subcortical areas, including the M1, premotor cortex, supplementary motor area, posterior parietal cortex, and thalamus (Lemon, 2008). These connections are essential for sensorimotor integration and control.

Participation in brain networks

The S1 is a critical node in the somatosensory network, which includes other areas like the S2, insular cortex, and parietal operculum. It also participates in the sensorimotor network, interacting with the motor and premotor cortices (Sepulcre, 2012).

Functions The S1 is crucial for processing somatosensory information like touch, proprioception, and temperature. It plays a significant role in perceiving object features, body awareness, and sensorimotor integration. Role in clinical disorders The altered functioning of the S1 has been implicated in various clinical conditions, including neuropathic pain (Baliki et al., 2011), phantom limb pain (Makin et al., 2013), and stroke-related sensory deficits (Carey et al., 2002).

Area 4: Primary Motor Cortex (M1)

The primary motor cortex (M1) is a key region in the brain responsible for the execution of voluntary movements. Graphic © Big8/Shutterstock.com.

Brodmann areas

The M1 is located in the precentral gyrus, mainly in Brodmann area 4. It contains large pyramidal neurons, known as Betz cells, which are essential for motor control (Geyer et al., 1996). Location

The M1 is situated in the frontal lobe, immediately anterior to the central sulcus. It is bordered by the posteriorly prima