3—Neuroscience; Forebrain Surface Anatomy
Cerebral Lobes
*1. Frontal lobes* - largest lobes of the brain. motor and cognitive functions. Primary motor cortex is located here. *2. Parietal lobes*- sensory-associative function, includes primary sensory cortex. *3. Occipital lobes*: visual and visual association function. *4. Temporal lobes*: integrative sensory, some functions of memory, audition and olfaction.
Primary Fissures
*1. Longitudinal Fissure* - separates the left and right cerebral hemispheres. The falx cerebri, a dural septum, lies in this fissure. (orange) *2. Lateral fissure (Sylvian fissure)*- separates temporal lobe from frontal and parietal lobes. (yellow) *3. Transverse fissure*- between cerebrum and cerebellum. A dural septum, the tentorium, lies here. (green) *4. Central sulcus (fissure of Rolando)*- separates frontal and parietal lobes, specifically the precentral and postcentral gyri. (blue) *5. Parieto-occipital sulcus/ fissure* - divides the parietal and occipital lobes on the medial surface of the hemisphere. An imaginary line on the lateral surface of the hemisphere from the upper end of this fissure to a small depression called the preoccipital (parieto-occipital) notch defines the border laterally. (pink)
Functional areas of the Temporal Lobe
*Heschl's Gyrus* (BA 41, 42): depths of lateral fissure --primary auditory cortex --basic perception of auditory info *Wernicke's Area* (posterior BA 22; some include part of BA 39, 40): posterior 1/3 of superior temporal gyrus --*Left hemisphere*: decoding meaning of speach --*Right hemisphere*: non-speech related auditory info processing
Functional areas of the Frontal Lobe
*Primary motor cortex* (BA 4): production of movement *Premotor region*(BA 6, 44, 45): --Planning and initiation of motor behaviors --*Broca's area*: motor speech area
Functional areas of the Parietal Lobe
*Primary sensory cortex* (BA 1, 2, 3): somatosensory perception *Somatosensory Association are* (BA 5, 7): process multi-sensory inputs --perception of shape, size, texture and object identification --Role in goal directed/ visually guided movements and object manipulation
Functional areas of the Occipital Lobe
*Primary visual cortex* (BA 17): form vision --located directly above and below calcarine fissure *Visual association cortices* (BA 18, 19, 20, 21, 37): processes features related to shape, color, position and motion
Limbic lobe
A synthetic lobe on the medial aspect of the hemisphere which encircles corpus callosum and medial part of the temporal lobe. Involved in emotion. Primary processor of memory. See hippocampal formation.
Cerebral Cortex Layers
Layers are heterogeneous Brodmann described 47 cytoarchitectural areas in man --Brodman's areas are used to describe functional areas of the cortex --Stroke and functional imaging have proven the validity
Surface Features
The surface of the cerebrum is not smooth, but rather it is marked by ridges and furrows, gyri and sulci, respectively. Deeper and more consistent sulci are called fissures. Primary fissures are used anatomically to divide the cerebrum into functional areas called lobes. This is possible because cortical areas of similar function are located near each other.
Insular lobe
Triangular shaped, invaginated cortical area hidden in the depths of the lateral fissure- mixed function, sensory and motor.
