Notes
The Cerebral Lobes
Sections
The Cerebral Lobes (Cerebrum)
The Sylvian fissure (aka the lateral sulcus)
- Distinguishes the cerebral lobes.
The central sulcus
- Distinguishes the frontal and parietal lobes.
The parieto-occipital sulcus
- Distinguishes the parietal and occipital lobes.
The precentral gyrus (the primary motor cortex)
- Lies anterior to the central sulcus.
The postcentral gyrus (the primary sensory cortex)
- Lies behind the central sulcus.
2 reliable indicators:
-The characteristic omega-shaped knob of the precentral gyrus
-The precentral gyrus is thicker than the postcentral gyrus
Optic pathway.
- Optic nerves (anteriorly)
- Optic chiasm (when they cross) and transition into the:
- Optic tracts.
Select Functional Regions
Language
- Broca's area is the language output area.
- It lies in the inferior frontal gyrus.
- Broca's aphasia is a non-fluent language disorder, meaning language output is severely impaired but comprehension is mostly preserved (it is hesitant and effortful). Broca's aphasia localizes to Broca's area but also to many other (mostly motor) brain regions.
- Wernicke's area is the language reception area.
- It lies within the superior temporal gyrus (posteriorly)
- Wernicke's aphasia is a fluent aphasia, meaning that there's preserved speech output but poor comprehension (it is melodious but meaningless). Wernicke's aphasia localizes to Wernicke's area and neighboring temporo-parietal regions plus the insula.
Vision
- The occipital lobe comprises cortical visual processing; it's so dedicated to vision that clinicians can easily miss large posterior cerebral strokes, they fail to check the patient's visual fields.
We subdivide visual processing into:
- The dorsal stream ("where") visual pathway, which lies along the superior occipital lobe and parietal lobe, and provides visuo-spatial localization processing.
- The ventral stream ("what") visual pathway, which lies along the inferior occipital lobe and temporal lobe, and provides object recognition processing.