The projection fibers consist of efferent and afferent fibers uniting the cortex with the lower parts of the brain and with the spinal cord. In human neuroanatomy, bundles of axons within the brain, called fibers, can be categorized by their function into association fibers, projection fibers, and commissural fibers.
The principal efferent strands are:
- (1) the motor tract, occupying the genu and anterior two-thirds of the occipital part of the internal capsule, and consisting of
- (2) the corticopontine fibers, ending in the nuclei pontis.
The chief afferent fibers are:
- (1) those of the lemniscus which are not interrupted in the thalamus;
- (2) those of the superior cerebellar peduncle which are not interrupted in the red nucleus and thalamus;
- (3) numerous fibers arising within the thalamus, and passing through its stalks to the different parts of the cortex ;
- (4) optic and acoustic fibers, the former passing to the occipital, the latter to the temporal lobe.