Human Physiology, 14th edition (2016)

The Central Nervous System 215

Basal Nuclei

The basal nuclei are masses of gray matter composed of neu-

ron cell bodies located deep within the white matter of the cere-

brum ( fig.  8.11 ). Although these are more commonly called

basal ganglia, the term “basal nuclei” is more anatomically

correct. This is because the basal ganglia are actually subcorti-

cal nuclei (collections of neuron cell bodies in the CNS) that

control voluntary actions.

The most prominent of the basal nuclei is the corpus

striatum, which consists of several masses of nuclei. The upper

mass, called the caudate nucleus, is separated from two lower

masses, collectively called the lentiform nucleus. The lentiform

nucleus consists of a lateral portion, the putamen, and a medial

portion, the globus pallidus. The basal nuclei (basal ganglia)

function in the control of voluntary movements.

The areas of the cerebral cortex that control movement

(including the precentral motor cortex; see fig. 8.6 ) send axons

to the basal nuclei, primarily the putamen. These cortical axons

release the excitatory neurotransmitter glutamate, which stimu-

lates neurons in the putamen. Those neurons, in turn, send axons

from the putamen to other basal nuclei. These axons are inhibi-

tory through their release of the neurotransmitter GABA. The

globus pallidus and the substantia nigra (a part of the midbrain, to

compared to those who were not allowed to have non-REM

sleep. In another study, slow-wave activity in an EEG (indi-

cating non-REM sleep) increased in trained subjects, and the

magnitude of that increase correlated with how well the sub-

jects performed on the learned task the next morning.

These and other studies demonstrate that, although short-

term memory is formed while a person is awake, the consolida-

tion of short-term into long-term memory is promoted by sleep.

Slow-wave sleep particularly benefits the consolidation of spatial

and declarative memories (those that can be verbalized). REM

sleep has been shown to benefit the consolidation of nondeclara-

tive memories, but evidence suggests that both stages of sleep

may participate in the consolidation of declarative and nonde-

clarative memories. Indeed, memory consolidation is best when

slow-wave and REM sleep phases follow each other naturally.

Memory consolidation improves after a nap, but longer

durations of sleep are required for maximum benefit. Evidence

suggests that the time delay between the learning session and

sleep is also an important consideration. Experiments indicate

that a time delay of about three hours between a learning ses-

sion and sleep provides better declarative memory consolidation

than a delay of eight hours. These studies strongly suggest that

students would improve their performance on an exam if they

studied earlier and got a good night’s sleep before the exam.

Figure 8.11 The basal nuclei. These are structures of the cerebrum containing neurons involved in the control of skeletal

muscles (higher motor neurons).The thalamus is a relay center between the motor cerebral cortex and other brain areas.

Basal nuclei

Claustrum

Corpus

striatum

Lentiform

nucleus

Caudate

nucleus

Motor cerebral cortex

Thalamus

Cerebellum

Spinal cord

Putamen

Globus

pallidus