KANDEL PRINCIPLES OF NEURAL SCIENCE CHAPTER 4: OVERALL
PERSPECTIVE
Somatosensory information from the ventral posterior lateral nucleus is conveyed mainly to the
primary somatosensory cortex. The neurons in the primary somatosensory cortex are exquisitely
sensitive to tactile stimulation of the skin surface. The primary somatosensory cortex is
somatotopically organized.
The amount of surface area of cortex devoted to each body part is proportional to the fineness of
discrimination in the body part this is related to the density of innervation of sensory fibers.
Brain circuitry is capable of plastic changes in response to use or disuse.
Layers of the neocortex:
I. – molecular layer
- occupied by the dendrites of cells located in deeper layers and axons that travel through
this layer to make connections in other areas of the cortex.
II. & III.
- contain mainly small pyramidal shaped cells
- external granual cell layer
- neurons located deeper in layer III are typically larger than those located more
superficially.
- axons project locally to other neurons within the same cortical area as well as the other
cortical areas intracortical communication.
III. ^
IV. – contains a large number of small spherical neurons and thus is called the internal granual
cell layer
- main recipient of sensory input from the thalamus and is most prominent in primary
sensory areas.
- areas with a prominent layer IV are called granular cortex.
V. – internal pyramidal cell layer
- neurons give rise to the major output pathways of the cortex, projecting to other cortical
areas and to subcortical structures.
VI. – polymorphic/multiform layer
- neurons are heterogenous in shape
- blends into the white matter.
Multimodal association areas appear to be particularly important for two functions:
1. The production of a unified percept
2. The representation of the percept in memory.
PERSPECTIVE
Somatosensory information from the ventral posterior lateral nucleus is conveyed mainly to the
primary somatosensory cortex. The neurons in the primary somatosensory cortex are exquisitely
sensitive to tactile stimulation of the skin surface. The primary somatosensory cortex is
somatotopically organized.
The amount of surface area of cortex devoted to each body part is proportional to the fineness of
discrimination in the body part this is related to the density of innervation of sensory fibers.
Brain circuitry is capable of plastic changes in response to use or disuse.
Layers of the neocortex:
I. – molecular layer
- occupied by the dendrites of cells located in deeper layers and axons that travel through
this layer to make connections in other areas of the cortex.
II. & III.
- contain mainly small pyramidal shaped cells
- external granual cell layer
- neurons located deeper in layer III are typically larger than those located more
superficially.
- axons project locally to other neurons within the same cortical area as well as the other
cortical areas intracortical communication.
III. ^
IV. – contains a large number of small spherical neurons and thus is called the internal granual
cell layer
- main recipient of sensory input from the thalamus and is most prominent in primary
sensory areas.
- areas with a prominent layer IV are called granular cortex.
V. – internal pyramidal cell layer
- neurons give rise to the major output pathways of the cortex, projecting to other cortical
areas and to subcortical structures.
VI. – polymorphic/multiform layer
- neurons are heterogenous in shape
- blends into the white matter.
Multimodal association areas appear to be particularly important for two functions:
1. The production of a unified percept
2. The representation of the percept in memory.
